Fassett, 2009

Palaeontologia Electronica http://palaeo-electronica.org

NEW GEOCHRONOLOGIC AND STRATIGRAPHIC EVIDENCE CONFIRMS THE PALEOCENE AGE OF THE DINOSAUR-BEARING OJO

ALAMO SANDSTONE AND ANIMAS FORMATION IN THE SAN JUAN BASIN, NEW MEXICO AND COLORADO

James E. Fassett

ABSTRACT

Dinosaur fossils are present in the Paleocene Ojo Alamo Sandstone and AnimasFormation in the San Juan Basin, New Mexico, and Colorado. Evidence for the Paleo-cene age of the Ojo Alamo Sandstone includes palynologic and paleomagnetic data.Palynologic data indicate that the entire Ojo Alamo Sandstone, including the lowerdinosaur-bearing part, is Paleocene in age. All of the palynomorph-productive rocksamples collected from the Ojo Alamo Sandstone at multiple localities lacked Creta-ceous index palynomorphs (except for rare, reworked specimens) and producedPaleocene index palynomorphs. Paleocene palynomorphs have been identified strati-graphically below dinosaur fossils at two separate localities in the Ojo Alamo Sand-stone in the central and southern parts of the basin. The Animas Formation in theColorado part of the basin also contains dinosaur fossils, and its Paleocene age hasbeen established based on fossil leaves and palynology.

Magnetostratigraphy provides independent evidence for the Paleocene age of theOjo Alamo Sandstone and its dinosaur-bearing beds. Normal-polarity magnetochronC29n (early Paleocene) has been identified in the Ojo Alamo Sandstone at six locali-ties in the southern part of the San Juan Basin.

An assemblage of 34 skeletal elements from a single hadrosaur, found in the OjoAlamo Sandstone in the southern San Juan Basin, provided conclusive evidence thatthis assemblage could not have been reworked from underlying Cretaceous strata. Inaddition, geochemical studies of 15 vertebrate bones from the Paleocene Ojo AlamoSandstone and 15 bone samples from the underlying Kirtland Formation of Late Creta-ceous (Campanian) age show that each sample suite contained distinctly differentabundances of uranium and rare-earth elements, indicating that the bones were miner-alized in place soon after burial, and that none of the Paleocene dinosaur bones ana-lyzed had been reworked.

PE Article Number: 12.1.3ACopyright: U.S. Geological Survey, Public Domain April 2009Submission: 13 December 2007. Acceptance: 28 January 2009

Fassett, James E. 2008. New Geochronologic and Stratigraphic Evidence Confirms the Paleocene Age of the Dinosaur-Bearing Ojo Alamo Sandstone and Animas Formation in the San Juan Basis, New Mexico and Colorado. Palaeontologia Electronica Vol. 12, Issue 1; 3A: 146p; http://palaeo-electronica.org/2009_1/149/index.html

FASSETT: PALEOCENE DINOSAURS

James E. Fassett. U. S. Geological Survey, Emeritus, 552 Los Nidos Drive, Santa Fe, New Mexico 87501 [email protected]

KEY WORDS: Paleocene dinosaurs; K-T interface, geochronology, palynology, paleomagnetism, verte-brate paleontology

INTRODUCTION

This paper reports new paleomagnetic, palyn-ologic, radiometric, and geochemical data relatedto the Paleocene age of the dinosaur-bearing OjoAlamo Sandstone and Animas Formation in theSan Juan Basin of New Mexico and Colorado.These data provide the primary evidence for theages of rock strata adjacent to the K-T interface inthe San Juan Basin.

Because the Ojo Alamo Sandstone containsin situ dinosaur fossils, its Paleocene age has beenquestioned over the years. Multiple workers, begin-ning with Reeside (1924), suggested (or implied)that the dinosaur fossils of the Animas Formationand the Ojo Alamo Sandstone were Paleocene inage, however until recently, the evidence for thePaleocene age of the Ojo Alamo has been sugges-tive, but not entirely conclusive (Fassett 1982,1987). Fassett and Lucas (2000) and Fassett et al.(2002), however, presented new data supportingthe Paleocene age of the Ojo Alamo Sandstone.Fassett et al. (2002) presented geochemical datashowing that all dinosaur fossils from the OjoAlamo Sandstone that were analyzed, had beenmineralized in place during Paleocene time andthus could not have been reworked from underly-ing Cretaceous strata. These new data, plus theexpanded paleontologic, paleomagnetic, and geo-chemical analyses presented in this report, fullysupport earlier conclusions of Fassett and Lucas(2000) and Fassett et al. (2002) that some dino-saurs lived on into earliest Paleocene time in theSan Juan Basin area. This study shows that theseLazarus dinosaurs lived for as long as 0.5 m.y. intoPaleocene time. The presence of dinosaur fossilsin the Paleocene Animas Formation of the northernSan Juan Basin, first noted by Reeside (1924),seems to have been forgotten or ignored since thattime; a discussion of Reeside’s data plus new infor-mation related to Animas Formation dinosaur fos-sils are presented herein.

PHYSICAL STRATIGRAPHY OF K-T BOUNDARY STRATA

Lithology and Mode of Deposition of Ojo Alamo Sandstone

The Paleocene Ojo Alamo Sandstone is aprominent stratigraphic unit throughout the NewMexico part of the San Juan Basin. This formationforms the striking, massive, 100 m high verticalcliffs along the south side of the San Juan River onthe south side of the city of Farmington in the west-central part of the basin (Figure 1). The Ojo Alamois a coarse-grained, conglomeratic sandstone thatcrops out around the periphery of most of the NewMexico part of the San Juan Basin but is absent inthe northern part (mostly in Colorado, Figure 1).The Ojo Alamo was deposited on a basin-wide ero-sion surface in early, but not quite earliest, Paleo-cene time by south-to-southeasterly flowing, highenergy, braided streams (Fassett 2000, Fassett etal. 2002). A hiatus of nearly 8 m.y., at (or in a fewplaces, slightly below) the base of the Ojo Alamo,separates Cretaceous and Tertiary rocks in thesouthern part of the basin (Fassett 1982, 1987,2000, Fassett and Steiner 1997, Fassett and Lucas2000, Fassett et al. 2002).

The Ojo Alamo is a multi-storied conglomer-atic sandstone with highly varied internal architec-ture and thicknesses throughout the basin (Fassettet al. 2002, figures 4 and 5). Conglomerate clastsrange from near-boulder size in the northwest partof the basin to small pebbles and grit in the south-east part. The rock-stratigraphic definition and ageof the formation have been characterized differ-ently by various workers over the years as dis-cussed in numerous papers; those discussions aresummarized and referenced in Fassett et al.(2002). Figure 2 shows the principal differences inthe ways the Ojo Alamo has been characterized inits type area and the way the name is used in thisreport. The so-called middle, “shaly” part of the OjoAlamo in the type area of the Ojo Alamo Sand-stone is a mischaracterization of this intervalbecause it contains multiple sandstone beds, andthese sandstones represent a significant part of theinterval. In the type area, the sandstones of themiddle part of the Ojo Alamo are white and rela-

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PALAEO-ELECTRONICA.ORG

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COLORADONEW MEXICO

Durango

MONTEZUMA

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Dulce

Cuba

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0 30 Km15

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NM San JuanBasin

Hunter Wash

Moncisco Mesa

San JuanRiver site(D6877)

Alamo Wash

De-na-zin Arroyo

Mesa Portales

Eagle Mesa

Gasbuggydrill hole

Important dinosaur-bone site

Paleocene pollen

Dinosaur bone andPaleocene pollen

Paleocene pollen fromdrill core

OJO ALAMOSANDSTONE

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Isopach map of Huerfanito Bentonite Bed - base of Ojo Alamo Sandstone from Fassett (2000); contour interval is 100 ft (about 30 m).

Farmington Sandstoneand upper shale memberof Kir t land Formation

Frui t land Formation and lower shalemember of Kir t land Formation

Lewis Shale

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Pictured Cliffs Sandstone

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Figure 1. Index map and cross section of San Juan Basin. Outcrops of Ojo Alamo Sandstone and Animas Forma-tion modified from Fassett and Hinds (1971, plate 1). 1.1 Important fossil localities and paleomagnetic-sectionlocalities through parts of Ojo Alamo Sandstone and adjacent strata. Isopach map shows thickness of intervalbetween Huerfanito Bentonite Bed and base of Ojo Alamo Sandstone. Area between Hunter Wash and De-na-zinArroyo is type area for Ojo Alamo Sandstone. D4119, D5393, D5394, D5408, D6877, and MM are USGS paleobot-any localities. DA (Durango area) palynologic site from Newman (1997). Bone symbol labeled FSS shows localityof dinosaur-bone sample collected for chemical analysis. 1.2 Stratigraphic cross section A-A' showing interval fromHuerfanito Bentonite Bed to base of Ojo Alamo Sandstone. Wells shown on cross section listed in Fassett andHinds (1971). Modified from Fassett et al. (2002).


tively friable rather than having the rusty-browncolor of the harder lower and upper benches, thusthese beds do not typically form cliffs or ledges.Photographs of the Ojo Alamo Sandstone at sev-eral outcrop localities are included in this reportand show the nature and variability of the lithologyof this formation.

The uppermost sandstone bench of the OjoAlamo Sandstone at most exposures, is rustybrown in color, tightly cemented, and forms a verti-cal cliff face. In some exposures, such as south ofFarmington (Figure 1), where the Ojo Alamo con-sists of as many as four, stepped-back benches,the uppermost sandstone bed capping each benchis also rusty brown, tightly cemented, and forms avertical cliff. At many localities, sandstone beds ofthe Ojo Alamo lying below the upper, cliff-forming,rusty-brown bed, are less well cemented, arewhiter in color, and weather into gentler slopes.

This phenomenon is probably the result ofdownward-moving ground water, containing moreiron in solution, moving laterally and selectivelythrough the relatively more permeable, uppermostOjo Alamo sandstone beds, thus cementing themmore tightly and giving them their distinctive rusty-

brown color. In the southern part of the San JuanBasin, this relationship has misled some workersinto thinking that there is a continuous uppermostsandstone bed of the Ojo Alamo that is widespreadthroughout large parts of the basin, whereas inreality, these upper beds are separate lenses of theOjo Alamo that happen to be rusty brown and moretightly cemented. This misconception has beenexacerbated by the presence of numerous sand-filled arroyos that cut through the Ojo Alamo out-crop preventing the continuous tracing of this rockunit.

Relation of Ojo Alamo Sandstoneto Underlying Strata

The stratigraphy of the rocks adjacent to theCretaceous-Tertiary interface in the San JuanBasin has been discussed in numerous paperssince about the beginning of the 20th century. Thefirst publication to describe the geometry of thesestrata over a large part of the basin was Reeside(1924). Reeside presented a series of 20 mea-sured sections around the north, west, and southedges of the basin; these sections showed thinningof the Fruitland-Kirtland interval from 561 m north-

Ojo Alamo Sandstone CRETACEOUS

Ojo Alamo Sandstone,restricted PALEOCENE

Ojo Alamo SandstoneTERTIARY (?)

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Nacimiento Formation

Kirtland shaleCRETACEOUS

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Torrejon and Puerco formations

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Paleocenedinosaur bone

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Bauer (1916) Baltz and others (1966) This reportReeside (1924)

Puercan mammalbone

CRETACEOUS CRETACEOUS

Figure 2. Generalized stratigraphic column showing lithology of Ojo Alamo Sandstone and adjacent strata in OjoAlamo type area (Figure 1), original rock-stratigraphic definition of Ojo Alamo of Bauer (1916), two subsequent prin-cipal redefinitions, and definition used in this report.

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west of Farmington (Figure 1) to 0 m northeast ofCuba, New Mexico. Reeside (1924, p. 52, 53, fig-ure 3) suggested that the thinning of Kirtland-Fruit-land strata, from northwest to southeast across thebasin, was the result of uplift and erosion of Creta-ceous strata that was much greater in the south-east part of the basin. Reeside acknowledged thatat some outcrops, the base of the Ojo Alamo Sand-stone appeared to be concordant with underlyingCretaceous strata, but in spite of that, he was con-vinced that there was a significant erosional hiatusat or below the base of the Ojo Alamo.

Dane (1936), however, on the basis of surfacemapping of Cretaceous and Tertiary rocks in thesoutheastern part of the basin, concluded thatthere was no erosional unconformity at the base ofthe Ojo Alamo. He reached this conclusionbecause he found places where a sandstone bedat the base of the Ojo Alamo thinned laterally andpinched out. At those localities, the shale abovethickened and appeared to merge with the underly-ing Kirtland Shale. Dane indicated that at suchplaces, the base of the Ojo Alamo should beshifted upward to the base of the next-highestsandstone bed. Dane thus concluded that therewas continuous deposition across the Kirtland-OjoAlamo contact, and thus there was no significanthiatus at this contact.

The geometry of the Ojo Alamo Sandstone atMesa Portales (Figures 1, 3) illustrates the exactsituation described by Dane. There, a lower benchof the Ojo Alamo Sandstone pinches out into mud-stones to the east, and its basal contact is thenapparently at the base of the higher sandstone bed(Fassett 1966, Fassett and Hinds 1971, figure 12).At this locality, however, the actual erosion surfaceat the K-T interface is about 22 m below the baseof the rock stratigraphic Ojo Alamo at the base of asandy interval (Fassett and Hinds 1971). Farthereast on Mesa Portales, where the lower sandyinterval marking the unconformity pinches out, theCretaceous-Tertiary interface becomes difficult todiscern, although it usually can be found with dili-gent searching.

Following Dane’s 1936 paper, dozens of localstudies of the rocks adjacent to the Cretaceous-Tertiary interface were published, with authors tak-ing varying positions regarding the presence orabsence of an unconformity at (or near) the base ofthe Ojo Alamo. These different interpretations werereviewed in Fassett and Hinds (1971); Fassett(1973, 1987, 2000); and Fassett et al. (2002). Fas-sett and Hinds (1971) presented a synthesis of allpreviously published data and included an analysisof hundreds of geophysical logs of drill holesthroughout the basin to precisely map the subsur-face relations of uppermost Cretaceous and lower-

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TERTIARY(Paleocene)

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GEOLOGY

Pot Mesa Area Map(figure 59)

Betonnie Tsosie WashArea Map(figure 11)

SE San Juan BasinMap (figure 21)

OA Type AreaMap (figure 4)D6900

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USGS palynology localities

Mammal-bone localitiesPaleomagnetic sections

Drill-hole locations

NAVAJO INDIANRESERVATION

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MM Moncisco MesaHW Hunter Wash

KW Kimbeto Wash

HW/AW Hunter Wash/Alamo WashBBA Barnum Brown AmphitheaterBSA Barrel Spring Arroyo

BTW Betonnie Tsosie WashEM Eagle MesaMP Mesa Portales

FBS Flynn (1986) Burnham South

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Kf

BurnhamTrading Post

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C Clemens (1973)FK Flynn (1986) KirtlandFOA Flynn (1986) Ojo Alamo Ss.LOA Lehman (1984) Ojo Alamo Ss.

RW

RW Rigby and Wolberg (1987)

WWWW Weil and Williamson (2000)

DNW

WKWEKW

DNZ De-na-zin WashWKW West Flank Kimbeto WashEKW East Flank Kimbeto WashBTW Betonnie Tsosie WashSMC Simpson (1959) Mesa de Cuba

BTW

SMC

SMC

Toa

HWGC

GC Gallegos Canyon

Figure 3. Geologic map of southern San Juan Basin showing locations of paleomagnetic sections through Creta-ceous and (or) Paleocene strata plus selected fossil-mammal bone and palynologic localities; mammal-bone locali-ties are approximate. Geology modified from Fassett and Hinds (1971). Areas of large-scale map figures are shown.

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most Paleocene strata and to assess the coalresources of the Fruitland Formation throughoutthe basin. This study confirmed Reeside’s interpre-tation of the thinning of the Fruitland-Kirtland inter-val from northwest to southeast (Figure 1).

Fassett and Hinds (1971) concluded thatFruitland and Kirtland rocks were deposited bystreams flowing northeastward toward the retreat-ing shoreline of the Western Interior Seaway, andthat this shoreline trended generally northwestthroughout the time it was retreating northeastwardacross the San Juan Basin area. Moreover, theychallenged an earlier contention by Silver (1950)that a basin of deposition had existed in the north-western part of the San Juan Basin in Kirtland For-mation time (named by Silver the “Kirtland basin”).Silver had inferred the presence of this basin solelyon the basis of an isopach map of the Fruitland-Kirtland interval that showed much greater thick-nesses of these rocks in the northwestern part ofthe basin. Fassett and Hinds (1971, figure 11) pro-duced a more detailed Fruitland-Kirtland isopachmap that showed in much greater detail how theserocks thinned southeastward across the basin.They also concluded that Silver’s concept of a Kirt-land basin was incorrect because the stratabeneath the Ojo Alamo had been truncated fromnorthwest to southeast across the basin during apre-Ojo Alamo erosion cycle.

The only published study of paleo-currentdirections for the Fruitland-Kirtland interval was byDilworth (1960) who measured cross-bedding inthe Farmington Sandstone Member of the KirtlandFormation at five localities west of Farmington (Fig-ure 1). Dilworth observed that streams depositingthe Farmington Sandstone flowed from southwestto northeast. Dilworth’s paleo-current study sup-ports the findings of Fassett and Hinds (1971) thatFruitland and Kirtland strata were deposited bynortheast-flowing streams.

Two comprehensive studies of paleo-currentdirections of the Ojo Alamo Sandstone (Powell1973, Sikkink 1987) showed that the Ojo AlamoSandstone was deposited by high-energy streamsflowing from the north or northwest. Those conclu-sions are supported by the fact that the conglomer-ate clasts of the Ojo Alamo Sandstone becomesmaller from north to south and from west to eastacross the basin. Sandstone beds in Fruitland-Kirt-land strata are fine to very-fine grained, whereasOjo Alamo Sandstone beds are coarse-grainedsandstone and conglomerates containing near-boulder-size clasts in the northwest part of thebasin. These contrasting lithologies have made the

mapping of the basal contact of the Ojo AlamoSandstone on the outcrop and in well logs straight-forward and uncontroversial.

Butler and Lindsay (1985) resurrected Silver’s(1950) “Kirtland basin” model and argued for anorthwest sediment source for the Kirtland Forma-tion and the Ojo Alamo Sandstone. They namedthis the “clastic-wedge” model for Fruitland-Kirtlanddeposition. This “clastic-wedge” model was basedprimarily on the assumption that there had beencontinuous deposition across the Kirtland-OjoAlamo contact. These authors, however, statedthat their model would effectively be disproved ifprecise dating of Kirtland strata proved that a sub-stantial hiatus was present at the base of the OjoAlamo Sandstone. Subsequent radiometric datingof altered volcanic ash beds in the Kirtland Forma-tion, to within 5 m of its upper contact with the OjoAlamo Sandstone by Fassett and Steiner (1997),demonstrated that nearly 8 m.y. are missing fromthe rock record at the Kirtland-Ojo Alamo contact inthe southern San Juan Basin. Thus, the “clasticwedge” model of Butler and Lindsay (1985) hasbeen refuted by their own suggested test of theirmodel.

In summation, present data show that theFruitland and Kirtland Formations were depositedby streams flowing northeastward toward theretreating Pictured Cliffs Sandstone paleo-shore-line. A single-crystal 40Ar/39Ar age of 73.04 ± 0.25Ma for sanidine crystals from an altered volcanicash bed in uppermost Kirtland Formation strata(Fassett and Steiner 1997) indicates that a nearly 8m.y. hiatus exists between the top of the KirtlandFormation and the base of the Ojo Alamo Sand-stone.

Animas and McDermott Formations

The Animas Formation was defined byReeside (1924), and that definition was revised byBarnes et al. (1954). Those authors extended thebase of the Animas Formation downward to incor-porate the upper part of the underlying McDermottFormation of Reeside (1924) renaming these stratathe McDermott Member of the Animas Formation.Barnes et al. (1954) reassigned the lower part ofReeside’s McDermott Formation to the upper partof the Kirtland Formation (then named “KirtlandShale”). The Animas Formation of Reeside (1924)thus became the “upper member of the Animas” aspart of this redefinition. The southern extent of theMcDermott Member was later restricted by Baltz etal. (1966) to the west side of the La Plata River,northwest of Farmington, New Mexico.

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It is here recommended that the original defi-nitions of the Animas Formation and McDermottFormation, as defined by Reeside (1924), be rein-stated. Reeside’s original McDermott Formation isan easily mappable unit of Late Cretaceous age(upper Campanian to lower Maastrichtian, as dem-onstrated by Newman 1987). The Animas Forma-tion of Reeside (1924) is also an easily mappableunit of Paleocene age (Knowlton 1924, Newman1987). An unconformity of several million years,representing the upper part of the MaastrichtianStage separates these rock units. In retrospect, nouseful purpose was served by the Barnes et al.(1954) redefinition of the Animas Formation, thus itis recommended that that redefinition be vacated inits entirety. The southern limit of the McDermottFormation suggested by Baltz et al. is still consid-ered valid and should thus still stand.

The Animas Formation is present mostly inthe Colorado part of the San Juan Basin (Figure 1)where it unconformably overlies, from west to east,the Cretaceous McDermott, Kirtland, and FruitlandFormations and is overlain by the Eocene SanJose Formation. The most detailed description ofthe lithology and stratigraphy of the Animas Forma-tion is discussed in Reeside (1924). The Animas isa volcaniclastic rock unit that consists of coarse-grained to conglomeratic, reddish sandstone bedsinterbedded with olive-green, finer grained, over-bank deposits. Knowlton (1924) presented adetailed study of the fossil leaves in the Animasand concluded that this flora indicated that the Ani-mas was Paleocene.

The lower part of the Animas Formation isequivalent in age to the Ojo Alamo Sandstone. TheOjo Alamo has been mapped separate from theAnimas in the northeastern part of the basin northand south of the Colorado-New Mexico State line(Figure 1). The upper part of the Animas is time-equivalent to the Nacimiento Formation in thesouthern (New Mexico) part of the San Juan Basin.The volcaniclastic content of the Animas is mostprominent in the northern part of the basin and theformation grades southward into volcaniclastic-freefluvial and lacustrine sandstones and mudstones ofthe Nacimiento Formation near the Colorado-NewMexico State line (Figure 1); mudstones dominatethe Nacimiento throughout most of the San JuanBasin.

Cretaceous-Tertiary Interface

The striking contrast between the fine- tomedium-grained rocks of the uppermost Creta-ceous Kirtland and Fruitland Formations and the

coarse-grained to conglomeratic strata of thePaleocene Ojo Alamo Sandstone and the AnimasFormation has made the mapping of the contactbetween these formations a relatively easy processin the San Juan Basin. This distinct physical con-trast alone is clearly suggestive of a significant hia-tus at the K-T interface. When the totally differentcurrent directions for rocks above and below theinterface are added to the equation, northeast-flow-ing streams for Cretaceous strata and south- tosoutheast-flowing streams for Paleocene strata,the case for a substantial hiatus at the K-T inter-face is strengthened even more. Clearly, significanttectonic events (representing millions of years)must have occurred between the time of depositionof Cretaceous strata and Paleocene strata in theSan Juan Basin. The geochronologic data obtainedover the past few decades have now allowed us toprecisely quantify this hiatus, as discussed below.

GEOCHRONOLOGY

The presence of abundant dinosaur bone inthe Ojo Alamo Sandstone in the San Juan Basinhas bedeviled researchers for more than 80 yearsbecause all other paleontological data, and thephysical stratigraphic relations discussed above,indicated that the Ojo Alamo was Paleocene inage. Indeed, had it not been for the presence ofabundant dinosaur remains in the Ojo AlamoSandstone, its Paleocene age would probablynever have been questioned. Because the lastoccurrence of dinosaur bone has always been con-sidered by vertebrate paleontologists to mark theend of the Cretaceous Period, various explanationswere suggested to explain away the presence ofthese dinosaur remains in what otherwiseappeared to be Paleocene rocks. (For a completediscussion of those explanations, see Fassett et al.2002.)

The relative age of sedimentary rock forma-tions was originally based on the fossils found inthose rocks (Winchester 2001). This criterionworked extremely well for marine rocks containingabundant fossils of small, steadily evolving, mostlyinvertebrate life forms, but was much less usefulfor continental strata containing far fewer diagnos-tic fossils, such as those of vertebrates. Wherepresent, the last occurrence of dinosaur fossils wastraditionally used to mark the top of the Cretaceousand Paleocene mammal fossils helped to locatethe base of the Tertiary. These vertebrate fossil arenormally not abundant in continental strata, thus inmost areas they did not allow for a precise place-ment of the K-T interface. Exacerbating the prob-

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lem, the endemic nature of vertebrate faunas in thenorthern and southern parts of the Western Interiorof North America made correlations of these fossilsdifficult. Plant fossils, being much more abundantin most continental strata, have proven to be amuch more valuable biochronologic tool. In particu-lar, fossil pollen and spores have proven to be aprecise tool for locating the K-T interface in theWestern Interior of North America.

Relatively recently, geophysical tools havebeen developed to precisely date sedimentary rockstrata, including radiometric dating and paleomag-netism. In the San Juan Basin, 40Ar/39Ar dating ofsanidine crystals from altered volcanic ash bedshas provided a series of eight precise ages for LateCretaceous strata ranging from 75.76 Ma to 73.04Ma (Fassett and Steiner 1997, Fassett 2000). Thusfar, in spite of much searching, only one dateableash bed has been found in Paleocene strata (in theNacimiento Formation) in the southeast part of theSan Juan Basin. Several paleomagnetic traverses,however, have been conducted across the K-Tinterface in the basin, and the magnetochron rever-sal boundaries from those studies provide excel-lent geochronologic tie points for the ages of K-T-interface strata.

This report focuses on the radiometric datingof ash beds, the determination of remanent paleo-magnetism of rocks adjacent to the K-T interface,and palynologic dating of rock strata to preciselylocate the K-T interface in the San Juan Basin. Itwill be shown that these independent geochrono-logic tools are mutually supportive in locating thisinterface at or below the base of the Ojo AlamoSandstone. Vertebrate paleontology, on the otherhand, has not proven to be a very precise tool forbiochronology in the San Juan Basin. Rather, theradiometric, paleomagnetic, and palynologic datafor rock samples from strata adjacent to the K-T-interface have established a precise geochrono-logic framework that can now be used to more pre-cisely assign ages to the vertebrate faunalassemblages in these strata.

PALEOMAGNETISM

Remanent magnetism of rock strata adjacentto the K-T interface in the San Juan Basin providesan objective geochronologic tool for placement ofthe K-T interface and for estimating a more preciseage for the base of the Ojo Alamo Sandstone.Paleomagnetic studies of these rocks have beenconducted by different workers in the southern SanJuan Basin at nine localities (Figures 1, 3). Thisreport presents published paleomagnetic data from

eight localities and one previously unpublishedpaleomagnetic data set from the Mesa Portalesstudy area (Figures 1, 3) in an integrated format.Eight of the published paleomagnetic studies werein: Butler et al. (1977); Lindsay et al. (1978, 1981,1982); Butler and Lindsay (1985); and Fassett andSteiner (1997). The paleomagnetic data presentedherein demonstrate that the dinosaur-bearing partof the Ojo Alamo Sandstone in the southern SanJuan Basin is within the lower part of normal-polar-ity chron C29n and is thus Paleocene in age.

Four of the paleomagnetic sections throughthe Ojo Alamo Sandstone were discussed in Lind-say et al. (1981): South Mesa, Barnum BrownAmphitheater, Barrel Spring, and Betonnie TsosieWash (Figures 3 and 4). The South Mesa, BarnumBrown Amphitheater, and Barrel Spring sectionsare 1.3 km and 1.8 km apart, respectively, (Figure4) and are in the heart of what is known as the OjoAlamo Sandstone type area (Bauer 1916, Baltz etal. 1966, Fassett 1973, Fassett 2000, Fassett et al.2002). These three sections are also within theBisti - De-na-zin Wilderness Area on the southedge of a topographic feature named “South Mesa”by Clemens (1973b, figure 3); South Mesa iscapped by the Ojo Alamo Sandstone. Clemensdefined South Mesa as being outlined by the6,400ft contour line on the USGS 1:24,000 AlamoMesa East Topographic Quadrangle (the name“South Mesa” does not appear on that map). TheBetonnie Tsosie Wash section is about 27 kmsoutheast of the Ojo Alamo type area (Figure 3).

The South Mesa paleomagnetic sectionthrough the Ojo Alamo Sandstone is the upper partof a longer section labeled the Hunter Wash-AlamoWash section in Lindsay et al. (1981). In a laterreport by Butler and Lindsay (1985), the part of thispaleomagnetic section through the Ojo AlamoSandstone was named the South Mesa section.The Betonnie Tsosie Wash section (Figure 3) wasnamed the “Tsosie Wash” section in Lindsay et al.(1981), however, the wash this section is namedfor is Betonnie Tsosie Wash (USGS 1:24,000 Kim-beto Topographic Quadrangle). The MonciscoMesa and Eagle Mesa sections do not include theOjo Alamo Sandstone and were published in Butlerand Lindsay (1985). The Hunter Wash section(Fassett and Steiner 1997) includes all of the Kirt-land Formation and the lower part of the Ojo AlamoSandstone in the western part of the type area(Figure 4).

Rock samples for the Mesa Portales paleo-magnetic section were collected in 1983 by E.M.Shoemaker (USGS, deceased), M.B. Steiner (U. of

8


Wyoming), and the author and in 1989 by Steinerand the author. Paleomagnetic analyses of thesesamples were performed by Steiner at the Univer-sity of Wyoming and by J.L. Kirschvink (for Shoe-maker) at the California Institute of Technology.The Mesa Portales section is especially importantbecause it is supplemented by detailed palynologicdata from multiple stratigraphic levels through theUpper Cretaceous Fruitland-Kirtland Formation(undivided), across the Cretaceous-Tertiary inter-face, and upward through most of the PaleoceneOjo Alamo Sandstone. Some of the Mesa Portalespalynologic data were published in Fassett andHinds (1971); additional palynologic data from thatlocality are presented herein for the first time. Anearlier palynologic study of the Ojo Alamo Sand-stone about 15 km northeast of Mesa Portales(Figure 3) was published by Anderson (1960) and

the significance of Anderson’s data, as related tothe Paleocene age of the Ojo Alamo Sandstone, isdiscussed in the “Palynology” section of this report.

Because magnetochrons contain no inherentgeochronologic information, it is essential thatpaleomagnetic data be supported by other geo-chronologic data to uniquely identify them. For Cre-taceous rocks underlying the Ojo AlamoSandstone, a robust sequence of eight precise40Ar/39Ar radiometric ages exists (Fassett andSteiner 1997, Fassett 2000, Fassett et al. 2002),thus the two magnetochrons identified in the south-ern San Juan Basin in these strata are unquestion-ably chrons C33n and C32r. Moreover, thestratigraphically highest radiometric date: 73.04 ±0.25 Ma, for an altered volcanic ash bed (ash J,Figure 4) less than 5 m below the base of the OjoAlamo Sandstone near Hunter Wash, confirmed

8

16

1 6


Willo

wW

ash

N

A B C

D

D

E F

H

I

JK

L

Ojo Alamo Ss dinosaur-bone localityKirtland Fm. dinosaurbone locality

B

Ojo Alamo Ss. dinosaur-bone locality - not sampledfor geochemical analysisAltered volcanic ash beds: Ash J: 73.04 +/- 0.25 Ma Ash H: 73.37 +/- 0.18 Ma

Hunter

Wash

T. 24 N.T. 25 N.

BarrelSpring

Alam

o

Wash

Ojo Alamo Sandstone

2930

31 3132

252627

33 35 36

28

23

45 1

11 12

6 5 4

7 8 10

151718 16

20 2221

R. 12 W. R. 11 W.

34

Kirtland Formation

0 5 km

De-

na-z

in

W

ash

M

Localities where dinosaur-bone was collectedfor geochemical analysis:

Locality Sample No. Locality Sample No.

A 070498-8A 070498-8A A 070498-8BA 070498-8CA 090498-8XA 090498-8Y B 022899-OA1C 020203-BC 020203-TD 020203-AE 022899-A

F 051298-BB1G SMP VP-1494H 020103I P-19147J 022799-B1J 022799-B2K 022799-CL 022799-AM 022799-DN 051504O SMP VP-1625

NOTE: Sample numbers keyed to geochemistry tables 2 and 3

LEGEND

Ash J

Ash H

O

Paleocene palynomorph assemblageCretaceous palynomorph assemblage

D8179-80

D9157

BAA-2

BAA-1

BSA

BBA

SM

WW

HW

BAA-3

Hunter Wash Pmag section (u. part)

Fig. A1-11

Ojo AlamoT.P. (ruins)

9

D6391

DNW

DNW Nacimiento Puercanmammal-bone site

San Juan CountyRoad 7500

Bisti - De-na-zinWildernessboundary

G

Figure 4. Geologic map of the Ojo Alamo Sandstone type area. White arrowheads point to areas where paleomag-netic data were obtained from the Ojo Alamo Sandstone; HW = Hunter Wash, SM = South Mesa, BBA = BarnumBrown Amphitheater, and BSA = Barrel Spring Arroyo; WW marks the Williamson-Weil mammal quarry. Dinosaur-bone locality I, in the NW 1/4 Sec. 7, T. 24 N., R. 11 W., is locality where 34 bones from a single Hadrosaur were dis-covered and collected from Ojo Alamo Sandstone. Geology modified from Brown (1982) and Scott et al. (1979);base of Ojo Alamo Sandstone was remapped for this study. Numbers with D prefixes are USGS paleobotany localitynumbers. Published palynomorph lists from this area and other areas are in tables in the Appendix. BAA-1 throughBAA-3 are palynologic sample localities of Baltz et al. (1966). Radiometric ages for sanidine crystals from alteredvolcanic ash beds H and J from Fassett and Steiner (1997) and Fassett (2000).

9


10

0

50

100

150

Meters

0

50

Meters

Virtual geomagnetic pole latitude- 90 0 + 90


KirtlandFormtion

KirtlandFormtion

Ojo AlamoSandstone

Ojo AlamoSandstone


BARREL SPRING ARROYO

11.02.5

17.0

-0.5-4.0-6.3

Paleocene mammal bonePaleocene dinosaur bone

C29r

C29r

C27r

C28r

C28r

C29n

C29n

C28n

C27n

5.0

3.07.2 9.0

8.5

-1.0

16.2 13.5

-11.0

14.5

21.0

-3.0

-8.0-5.0

15.2

BARNUM BROWN AMPHITHEATER

Altered volcanic ash bed

Figure 5. Paleomagnetic and stratigraphic sections at Barrel Spring Arroyo and Barnum Brown Amphitheater, modi-fied from Lindsay et al. (1981): “Solid data points indicate sites with grouping of directions significant from random atthe 95% confidence level. Open circles indicate data points from sites with poorer clustering.” (Lindsay et al. 1981).The same symbology applies for all subsequent figures of these authors reproduced herein. These localities arelabeled BSA and BBA, respectively, on Figures 3 and 4. (Barrel Spring Arroyo of the Lindsay et al. report is nownamed De-na-zin Wash (Alamo Mesa East, 1:24,000 USGS quadrangle map.) Labels of magnetochrons (as appliedby Lindsay et al. 1981, elsewhere in their paper) have been added to this illustration, for ease of discussion. (Note:some magnetochron labels shown are now known to be incorrect as discussed in the section of this paper labeled“Identification of Kirtland Formation-Ojo Alamo Sandstone Magnetochrons.”) Distances of selected paleomagnetic-samples sites, above and below the base of Ojo Alamo Sandstone (in meters), are added. Dinosaur-bone symbol onBarnum Brown Amphitheater column was added by author.


the presence of a 7.8-m.y. hiatus separating theKirtland Formation of Cretaceous (Campanian) agefrom the overlying Ojo Alamo Sandstone of Paleo-cene age. Palynomorphs identified from thesestrata also help to date them, although somewhatless precisely. Tschudy (1973) and Newman (1987)published palynologic data from the stratigraphi-cally highest Cretaceous rocks in the San JuanBasin. Both of these studies indicated that a signifi-cant hiatus existed at the K-T interface represent-ing all or most of Maastrichtian time; theradiometric dates published by Fassett and Steiner(1997) and Fassett (2000) confirmed the bio-chronologic findings of Tschudy and Newman.

All attempts to radiometrically date the OjoAlamo Sandstone have thus far been unsuccess-ful; however, all paleobotanical evidence suggestsa Paleocene age (Reeside 1924, Knowlton 1924,Anderson 1960, Fassett and Hinds 1971, Tschudy1973, Fassett 1982, Fassett 1987, Fassett andSteiner 1997, Fassett 2000, Fassett and Lucas2000, and Fassett et al. 2002). New, robust palyno-logic data from the Mesa Portales locality confirmthese earlier studies that showed that the age ofthe entire formation is Paleocene; a summary ofthis palynologic data is contained in the “Palynol-ogy” section of this report.

Puercan-age (lowermost Paleocene) verte-brate fossils have been identified in the lowermostpart of the Nacimiento Formation. The Nacimientodirectly overlies and intertongues with the OjoAlamo Sandstone at five localities in the southernSan Juan Basin. These data provide additional, ifinferential, evidence that at least the upper part ofthe Ojo Alamo is Paleocene (Williamson and Lucas1992, 1993; Williamson 1996). Vertebrate paleon-tologists have disagreed about the biochronologicage of the lower, dinosaur-bearing part of the OjoAlamo Sandstone. For example, Sullivan et al.(2005) contended that the Ojo Alamo contains adinosaur fauna that is latest Campanian or earlyMaastrichtian whereas Weil and Williamson (2000)and Farke and Williamson (2006) state that thevertebrate fauna of the lower Ojo Alamo is clearlyLancian (latest Maastrichtian) in age. These differ-ent vertebrate-fossil ages for the Ojo Alamo areevaluated in the “Vertebrate Paleontology” sectionof this paper.

The following sections discuss the severalpublished paleomagnetic studies that include theOjo Alamo Sandstone. These publications are pre-sented in chronologic order to best show the evolu-tion of thinking about the numbering of themagnetic-polarity intervals identified in the rock

strata adjacent to the K-T interface in the southernSan Juan Basin. In this historical discussion, therelatively thin, normal-magnetic-polarity intervalwithin the Ojo Alamo Sandstone is labeled C29n,after Lindsay et al. (1981), Fassett and Steiner(1997), and Fassett (2000). This thin Ojo Alamo-normal interval is now known to be only the lower-most part of chron C29n and is therefore desig-nated C29n.2n as discussed in the “Identification ofMagnetochrons” section of this paper.

Localities of Lindsay et al. (1981)

Barrel Spring Arroyo. The Barrel Spring Arroyopaleomagnetic section (BSA, Figure 4) is on thenorth side of De-na-zin arroyo, about 0.4 km northof Barrel Spring. The paleomagnetic data plot forthis section of Lindsay et al. (1981, figure 7) isshown on Figure 5. This plot contains five datapoints of reversed polarity in the Kirtland Forma-tion, four data points with normal polarity in thelower part of the Ojo Alamo Sandstone, and fivedata points with reversed polarity in the upper partof the Ojo Alamo. Additional alternating zones ofnormal and reversed polarity are shown in theoverlying Nacimiento Formation. The entire sectionis about 160 m in length, and critical data pointsbelow, within, and above the Ojo Alamo Sandstoneare numbered in meters, below or above the baseof the Ojo Alamo Sandstone. The magnetochronsin the lower part of the section were labeled B-, C+,D-, E+, F-, and G+ by Lindsay et al. (1981) on theirfigure 7, but in a subsequent section of their paperwere relabeled C29r, C29n, C28r, C28n, C27r, andC27n, respectively, as shown on Figure 5.

Figure 6 is an annotated photograph of theBarrel-Spring-Arroyo locality showing that the OjoAlamo Sandstone consists of a lower conglomer-atic sandstone, a middle “shaly” part, and an upper,massive, conglomeratic-sandstone bench. Thestratigraphic positions of the paleomagnetic datapoints from Lindsay et al. (1981) were placed onthis photograph based on the locations of thesepoints shown on Figure 5. Figures 5 and 6 showthat the Ojo Alamo at this locality contains in itslower part a normal magnetochron (labeled C29nby Lindsay et al. 1981). This normal interval isshown to be about 14 m thick, based on theassumption that a thin, reversed-polarity interval,the uppermost part of chron C29r, is present herein the lowermost part of the Ojo Alamo Sandstone.This assumption is based on the fact that all otherpaleomagnetic sections through the Ojo AlamoSandstone in the southern San Juan Basin showthe presence of a thin reversed paleomagnetic

11


interval in the lowermost part of this formation. Allbut one of the samples collected for paleomagneticanalyses were from gray mudstones; the sample at9.0 m above the base of the Ojo Alamo (Figure 6)is from a slightly reddish-brown mudstone. Thelower samples are from a gently sloping topo-graphic bench, whereas samples 13.5, 15.2, and16.2 are from more steeply dipping terrain. Note onFigure 6 that all samples were collected from mud-stone layers avoiding the prominent white sand-stone beds present in the middle “shaly” part of theOjo Alamo. The lensing nature of all of the strata inthe middle part of the Ojo Alamo is apparent at thislocality.Barnum Brown Amphitheater. The BarnumBrown Amphitheater paleomagnetic section (BBA,Figure 4) is on the south edge of South Mesa; thislocality is about 1.8 km west of the Barrel SpringArroyo (BSA) section. (The name “Barnum BrownAmphitheater” was apparently coined by Lindsay et

al. (1981) for this locality and should not be con-fused with the amphitheater referred to by BarnumBrown (1910) that is several kilometers northeastof this locality in Alamo Wash stratigraphicallyabove the Ojo Alamo Sandstone in the NacimientoFormation.) The paleomagnetic section at the BBAlocality is short (~32 m), consisting of only 11 sam-ple levels; samples were collected from the upper-most Kirtland Formation and the lower part of theOjo Alamo Sandstone (Figure 5). The five Kirtlandsamples exhibit reversed polarity; the lowest OjoAlamo sample also exhibits reversed polarity, thenext three samples in the lower Ojo Alamo exhibitnormal-reversed-normal polarity, and the upper-most three samples show reversed polarity. Lind-say et al. (1981, p. 411) stated that the reversedsite in the middle of the Ojo Alamo Sandstone nor-mal interval at the Barnum Brown locality wasweakly magnetized and that “. . . the site meanVGP moved toward positive values during AFdemagnetization. Thus we do not interpret the data

Base - upperOjo Alamo SsOjo Alamo Ss

Lowerconglomerate

Lowerconglomerate

C32r

C29r Lowerconglomerate

-1.0

3.0

13.5

7.2

9.0

15.216.2

Contact - Ojo Alamo Sson Kirtland Formation

C32r

C29n.2n

C29n.1r

r

Middle shaly unit

Figure 6. Photograph of Barrel Spring locality (looking north) of Lindsay et al. (1981); location is shown on Figures 3and 4. Magnetochron labels for Ojo Alamo Sandstone are corrected as discussed in the “Identification of KirtlandFormation-Ojo Alamo Sandstone Magnetochrons” section of this report. Lindsay et al.’s (1981) paleomagnetic dataplot at this locality is on Figure 5. Numbered arrow heads are distances above base of Ojo Alamo Sandstone inmeters; sample levels are approximate. Arrow heads pointing left indicate reversed polarity, arrow heads pointingright indicate normal polarity. Sample levels are estimated from Figure 5, but exact original sample localities are notknown.

12


from this site to be a reliable indication of areversed subzone within normal C+ [C29n].”

Figure 7 is an annotated photograph showingthat the Ojo Alamo Sandstone at the BBA localityconsists of a lower conglomerate, a middle “shaly”unit, and an upper more massive sandstonebench. The lithologies of the Ojo Alamo Sandstoneat the BBA and BSA localities are similar, exceptthere is more sandstone present at the BBA localityin the middle part of the Ojo Alamo. The strati-graphic locations of the paleomagnetic data pointsfrom the Lindsay et al. (1981) report are placed onthis photograph based on the positions of thesepoints shown on Figure 5. The normal-polarityinterval labeled C29n by these authors is 11 mthick at the BBA locality; the underlying interval ofreversed polarity in the lowermost OjoAlamo—labeled C29r—is 2.6 m thick. All of thesamples collected at this locality were from graymudstones. The lowermost, reversed-polarity sam-

ple (2.5) was from a gently sloping hill, whereas thehigher Ojo Alamo samples were from a muchsteeper cliff face. This steeper cliff face reflects thetopographic expression of the white sandstonebeds in the upper part of the middle interval of theOjo Alamo Sandstone. Figure 7 shows that thesamples collected for paleomagnetic analyses atthis locality were from relatively thin interbeds ofmudstone.South Mesa. The South Mesa (SM) paleomag-netic section is at the west end of South Mesa neara westward-projecting spur capped by the cliff-forming Ojo Alamo Sandstone (Figure 4). This sec-tion is the uppermost part of a much longer paleo-magnetic section through the underlying Fruitlandand Kirtland Formations. Lindsay et al. (1981)named this the Hunter Wash/Alamo Wash section(Figure 8). Figure 9, a large-scale paleomagneticplot through the uppermost Kirtland Formation andlower part of the Ojo Alamo Sandstone, contains

Lowerconglomerate


Lowerconglomerate

act - Ojo O Alamo rtland Formation

Ssn

Contaon Kir

-0.5

2.5

5.0

8.5

14.5

11.0

C29n.2n

C29n.1r

C32r

C29r

Base - UppperOjo Alamo Ss

Middle shaly unit

Figure 7. Photograph of Barnum Brown Amphitheater locality (looking north) of Lindsay et al. (1981); location is onFigures 3 and 4. The paleomagnetic data plot at this locality is on Figure 5. Magnetochron labels in Ojo Alamo Sand-stone are corrected as discussed in section of this paper labeled “Identification of Kirtland Formation-Ojo AlamoSandstone Magnetochrons.” Numbers at arrow heads are distances above base of Ojo Alamo Sandstone in meters;sample levels are approximate. Arrow heads pointing left indicate reversed polarity, arrow heads pointing right indi-cate normal polarity. Sample levels are estimated from Figure 5, but exact original sample localities are not known.

13


three reversed-polarity and four normal-polaritydata points. The numbers shown for each datapoint are distances in meters above or below thebase of the Ojo Alamo Sandstone. This paleomag-netic section ended just beneath the base of theupper massive sandstone bed of the Ojo Alamo,thus the top of magnetochron C29n was notlocated at this locality. Magnetochrons C29n andC29r are shown on Figure 9 as identified by Lind-say et al. (1981).

Figure 10 is an annotated photograph of theSouth Mesa paleomagnetic locality, and here, as atthe Barrel Spring and Barnum Brown Amphitheaterlocalities, the Ojo Alamo Sandstone consists of alower conglomerate bed, a middle “shaly” unit, andan upper, massive, conglomeratic sandstonebench. The stratigraphic locations of the paleo-magnetic data points from Lindsay et al. (1981) areplaced on this photograph based on the positionsof these points shown on Figures 8 and 9. Mag-netic normal interval C29n is 5.9 m thick here (top


0

50

100

150

Meters

200

250

C29r

C29n

C30n

C30r

C31n

Ojo AlamoSandstone

KirtlandFormtion

FruitlandFormtion

Figure 8. Paleomagnetic data plot at “Hunter Wash/Alamo Wash” locality. (Figure is modification of figure 6 of Lindsayet al. 1981 and is reproduced herein with permission of the American Journal of Science.) Upper part of sectionthrough upper Kirtland Formation and lower Ojo Alamo Sandstone is labeled SM on Figures 3 and 4. Cretaceous-Ter-tiary boundary plus magnetochron labels as identified by Lindsay et al. (1981) are added for ease of discussion. Bonesymbols represent important vertebrate-fossil levels. (Note: some magnetochron labels shown are now known to beincorrect as discussed in the section of this paper labeled “Identification of Kirtland Formation-Ojo Alamo SandstoneMagnetochrons.”)

14


not determined), and the underlying reversed-polarity chron C29r (in the lowermost part of theOjo Alamo) is 5 m thick. All samples collected forpaleomagnetic analysis at this locality appear tohave come from gray mudstones. The reversed-polarity sample 1 m above the base of the OjoAlamo in the basal part of the middle “shaly” unitis from a gently sloping topographic bench.Reversed polarity sample 4.5 and the four overly-ing samples of normal polarity, were from a muchsteeper cliff face. The middle “shaly” interval of theOjo Alamo Sandstone contains multiple sandstonebeds at this locality.Betonnie Tsosie Wash. The Betonnie TsosieWash (BTW) paleomagnetic section (“TsosieWash” section of Lindsay et al. 1981) is about 28km southeast of the Ojo Alamo Sandstone typearea (Figure 3). This locality is on an outlier of mid-dle and upper Ojo Alamo Sandstone strata on theeast side of a north-trending tributary of BetonnieTsosie Wash (Figure 11). The paleomagnetic dataplot for samples collected from this locality(Figure12) contains five normal-polarity sites at thebase overlain by two reversed-polarity sites in themiddle Ojo Alamo Sandstone; one normal-polaritysample is in the upper part of the Ojo Alamo. Theoverlying Nacimiento Formation contains a largenumber of data points with normal polarity (andone sample with reversed polarity). The middle andupper parts of the Ojo Alamo Sandstone at this

locality are about 27 m thick. The base of the OjoAlamo is about 5 m stratigraphically below the 26.6sample locality (Figure 12). This paleomagneticsection is particularly important because it includesa Puercan mammal quarry only 12 m above the topof the Ojo Alamo (Figures 11 and 12). (The bio-chronology of the paleomagnetic sections includedin this report is discussed in detail in subsequentsections of this paper.) The magnetochron labeledC29n (Figure 12) is 7.1 m thick, however, its basewas not determined because of alluvial coverimmediately below sample 26.6. Chron C29n isoverlain by chrons labeled C28r, C28n, C27r, andC27n by Lindsay et al. (1981). (These labels arerevised in a subsequent section of this paper.)

Figure 13 is a photograph of the small buttewhere samples from the Ojo Alamo Sandstone partof the Betonnie Tsosie Wash paleomagnetic sec-tion were collected (Figure 12). This butte iscapped by a 4 m thick, hard, iron-cemented, cliff-forming, conglomeratic sandstone layer that is theuppermost part of the upper bench of the OjoAlamo. The underlying shaly interval is about 11 mthick here with its base masked by alluvium. (Alower sandstone bench of the Ojo Alamo Sand-stone is exposed farther south in this tributary ofBetonnie Tsosie Wash (Figure 11) and its base isabout 5 m below the exposed part of the Ojo Alamoseen on Figure 13.) The upper part of magneto-chron C29n is in the lower part of the middle shalyunit of the Ojo Alamo Sandstone (Figure 13). Most

-90 +900Virtual geomagnetic pole latitude

C29n

0

5

-5

10

15meters

-2.1

TERTIARY

CRETACEOUS

magnetochrons stratigraphy

1.0

4.5 6.0

7.5

9.811.1 ? upper cgl.

lower cgl.

Ojo AlamoSandstone

C29rKirtland Shale

Figure 9. Large-scale view of South Mesa paleomagnetic section (labeled SM on Figures 3, 4). Stratigraphic levelsof samples collected for paleomagnetic analyses are shown in meters above or below base of Ojo Alamo Sandstone.Plot is expanded-scale rendition of upper part of Hunter Wash/Alamo Wash section of Lindsay et al. (1981) of Figure8; top of chron C29n was not determined. (Magnetochron labels are now known to be incorrect as discussed in sec-tion of this paper labeled “Identification of Kirtland Formation-Ojo Alamo Sandstone Magnetochrons.”)

15


of the paleomagnetic samples were collected fromgray mudstone beds; sample 23.6, however, wasfrom maroon-colored strata. All of the sample sitesare on a relatively steep topographic slope (Figure13).Summary. As a result of their paleomagnetic andbiochronologic studies of the rock strata adjacentto the Cretaceous-Tertiary (K-T) interface in thesouthern San Juan Basin, Lindsay et al. (1981)concluded that there was continuous depositionacross it. They identified magnetochrons C31n,C30r, C30n, and the lower part of C29r in the Cre-taceous Kirtland Formation beneath the K-T inter-face and found the upper part of C29r, C29n, C28r,and the lower part of C28n to be within the OjoAlamo Sandstone, above the K-T interface. Inaddition, they identified chrons C27n, and C27r

higher in the Nacimiento Formation. Lindsay et al.(1981) thus determined that chron C29n was pres-ent in the lower part of the Ojo Alamo Sandstone atall four localities where they had conducted paleo-magnetic traverses through that formation.

Lindsay et al. (1982)

Lindsay et al. (1982) reexamined their identifi-cation of magnetochron C29n in the Ojo AlamoSandstone because they were apparently troubledby the fact that their data indicated (p. 449) “thatthe extinction of dinosaurs was not coincident withthe extinction of marine organisms at the end of theCretaceous Period, as recorded in several marinesequences.” They were also responding to numer-ous challenges to their earlier findings by Alvarezand Vann (1979), Fassett (1979), and Lucas and


C32r

9.8

7.5

6.0

11.1

1.0

4.5

C29r

C29n.2n

PALEOCENE

CRETACEOUS(Campanian)

?

Top - lowerconglomerate

Upper conglomerate

Middle shaly unit

Figure 10. Photograph of South Mesa locality (looking north) of Lindsay et al. (1981); location is on Figures 3 and 4.The paleomagnetic data plot at this locality is on Figures 8, 9. (Paleocene magnetochron labels shown are correctedas discussed in the section of this paper labeled “Identification of Kirtland Formation-Ojo Alamo Sandstone Magneto-chrons.”) Numbers at arrow heads are distances above base of Ojo Alamo Sandstone in meters; sample levels areapproximate. Arrow heads pointing left indicate reversed polarity, arrow heads pointing right indicate normal polarity.Sample levels estimated from Figure 9, but exact original sample localities are not known.

16


Tsosie

Paleocene mammal

32 33 34 35

4 235

8 9 10 11

T. 22 N.

T. 23 N.

Betonnie

Was

h

Puercanmammalquarry

Top OA

BTWsite

A

B CD

Cretaceous dinosaur Paleocene dinosaur

Figure 11. Map showing location of Betonnie Tsosie Wash (BTW) paleomagnetic section (“Tsosie Wash” locality ofLindsay et al. 1981). Also shown are places where mammal- and dinosaur-fossils have been found. Dinosaur-bonesample letters keyed to tables showing chemistry of bone samples collected from Cretaceous Kirtland Formation andPaleocene Ojo Alamo Sandstone; unlettered dinosaur-bone localities from Lucas and Sullivan (2000). Mammal-bone site is Betonnie Tsosie Wash locality of Williamson and Lucas (1992). Map from USGS 1:24,000-scale KimbetoTopographic Quadrangle map.

Rigby (1979). Those criticisms primarily related totheir conclusion that there had been continuousdeposition across the K-T interface in contraven-tion to numerous previous publications indicatingthat a substantial hiatus existed at this boundary.(Several papers in Fassett and Rigby 1987 subse-quently presented evidence for a substantial hiatusat the K-T interface in the San Juan Basin.) Lind-say et al. (1981) were also criticized for stating thatthe K-T boundary in the San Juan Basin was notsynchronous with the K-T boundary in the marinesequence near Gubbio, Italy. In their 1982 paperthese authors reaffirmed their correlation of thenormal-polarity interval in the lower part of the OjoAlamo Sandstone with magnetochron C29n and

concluded (p. 451): “We believe that correlation isaccurate, which implies Paleocene dinosaurs livedin the San Juan Basin [my emphasis].” They alsoreaffirmed their earlier contention that there was nosignificant hiatus at the K-T interface in the SanJuan Basin.

In addition, Lindsay et al. (1982) stated: “Wedoubt that magnetochron + [C29n] is caused by anormal overprint . . .” and discussed tests of thereliability of their identification of the lower OjoAlamo Sandstone normal chron, C29n. Theystated that each of their sites that yielded normalremanent magnetic polarity in the Ojo Alamo Sand-stone was represented by multiple samples, andthat a statistical “test for nonrandom distribution” of

17


their data showed that 87% passed this “rigoroustest.” In a discussion of the minerals carrying theremanent magnetism in the Kirtland Formation andOjo Alamo Sandstone in their study localities, theyconcluded that “the dominant ferromagnetic min-eral in sediments of the San Juan Basin is detritalstoichiometric titanomagnetite in the 0.51 x 0.54proportionality range.” They further determined thatthe Ojo Alamo Sandstone samples did contain arelatively high hematite content but that this higherhematite content existed in both normal andreversed polarity intervals in the Ojo Alamo andstated that “The available data do not favor anoverprint origin for magnetozone + [C29n].” Theyconcluded: “Thus, the available data suggest thatmagnetozone + [C29n] in the San Juan Basin isreliable, and we continue to correlate it with mag-netic anomaly 29.”

Butler and Lindsay (1985)

Butler and Lindsay (1985) published theresults of further tests of possible overprinting ofthe normal-polarity interval in the lower part of theOjo Alamo Sandstone. However, they stated (insome parts of this paper) that the normal intervalC29n (labeled + in their report) was in the KirtlandFormation rather than in the Ojo Alamo Sandstone,contrary to the placement of this magnetochron inthe Ojo Alamo Sandstone in all of their previouspublications. Normal chron C29n (also designated“C+”) is clearly shown to be within the Ojo Alamo intheir 1981 paper.

Butler and Lindsay (1985) offered no explana-tion as to why they considered chron C29n to be inthe Kirtland Formation in this report. Adding to theconfusion, they show this normal to be in the OjoAlamo in figure 7 of their 1985 paper, even though

0

50

100

Meters


C27r

C28r


Ojo AlamoSandstone

Q

20.7

26.625.0

23.622.0

18.715.5

P

C29n

C27n

C28n

Figure 12. Paleomagnetic data plot and stratigraphic section at Betonnie Tsosie Wash locality, modified from Lind-say et al. 1981. Betonnie Tsosie Wash labeled “Tsosie Wash” in Lindsay et al. report. Q = fossiliferous interval con-taining Periptychus, Torrejonian age; P = fossiliferous interval containing Puercan mammals (listed in Lindsay et al.1981). Distances of P and Q fossil levels above top of Ojo Alamo Sandstone and thickness of upper bed of OjoAlamo Sandstone, are shown. Labeling of magnetochrons C29n, C28r, C28n, C27r, and C27n are also added as aredistances, in meters, below top of Ojo Alamo Sandstone of selected paleomagnetic sample-collection sites. (Magne-tochron labels shown are now known to be incorrect as discussed in section of this paper labeled “Identification ofKirtland Formation-Ojo Alamo Sandstone Magnetochrons.”)

18


they state in their figure 7 caption that this figureshows: “Paleomagnetic data from re-collections ofthe three sections below [my emphasis] Ojo AlamoSandstone on South Mesa originally used by Lind-say et al. (1981) to define Magnetozone + [C29n].”Because of these conflicting statements, it is notpossible to assess with certainty where in the mea-sured sections the “re-collections” discussed bythese authors were made.

The 1985 paper by Butler and Lindsay con-tains a comprehensive discussion of the magneticminerals that carry the normal-polarity signal in theOjo Alamo Sandstone at the South Mesa, BarnumBrown Amphitheater, and Barrel Spring Arroyosections (Figure 4). (Curiously, there is no mention

in this paper of the normal-polarity interval identi-fied in 1981 as C29n in the Ojo Alamo at their“Tsosie Wash” locality.) These authors concludedthat their previous publications showing the pres-ence of the normal-polarity interval C29n in thelower Ojo Alamo were in error, and stated that thisnormal interval was in reality a Bruhnes (present-day-normal) overprint, and thus should be removedfrom their San Juan Basin paleomagnetic section.As a consequence of the elimination of C29n,these authors were forced to re-number the sev-eral other magnetochrons they had previouslyidentified overlying it, by changing the next-highestnormal from C28n to C29n, changing C27n toC28n, etc. Butler and Lindsay (1985) concluded

25.0

26.6

20.7

23.6

22.0

15.5

18.7

C29n.2n

C29n.1r

Middle part of Ojo AlamoSandstone

Upper BenchOjo Alamo Ss

Upper BenchOjo Alamo Ss

?

Figure 13. Photograph of Betonnie Tsosie Wash paleomagnetic locality, looking north (“Tsosie Wash” of Lindsay et al.1981.) Locality is just east of north-trending tributary of Betonnie Tsosie Wash (Figure 11), about 28 km southeast ofBarrel Spring locality (Figure 4). Magnetochron labels shown are corrected as discussed in section of this paperlabeled “Identification of Kirtland Formation-Ojo Alamo Sandstone Magnetochrons.” Numbers at arrowheads are dis-tances in meters below base of iron-cemented cap rock of upper bench of Ojo Alamo Sandstone. Arrow heads point-ing left indicate reversed polarity; arrowheads pointing right indicate normal polarity. Paleomagnetic data plot at thislocality shown on Figure 12. Sample levels estimated from Figure 12, but exact original sample sites not known. Lind-say et al. (1981) placed base of upper Ojo Alamo Sandstone at base of hard, iron-cemented-sandstone cap rock atthis locality, however, as figure shows, this cap rock is just a harder layer at top of upper bench of Ojo Alamo Sand-stone.

19


that the dinosaur fossils in the Ojo Alamo Sand-stone were Cretaceous in age, and they continuedto maintain that there was no significant hiatus atthe Cretaceous-Tertiary boundary in the San JuanBasin. The question of the validity of the remanentpaleomagnetism of the normal interval in the lowerOjo Alamo Sandstone is further addressed in asubsequent section of this paper.

Fassett and Steiner (1997) - Hunter Wash Paleomagnetic Section

The Hunter Wash paleomagnetic section ofFassett and Steiner (1997) is in the southwesternpart of the San Juan Basin in Hunter Wash and inthe headwaters of a northwest-trending tributary ofHunter Wash (Figures 2, 4). The paleomagneticdata plot for the Hunter Wash section is on Figure14. The upper part of this section through the

uppermost Kirtland Formation and lower part of theOjo Alamo Sandstone is shown at an expandedscale on Figure 15. This figure shows reversedremanent magnetism 4 m below the base of theOjo Alamo in the Upper Cretaceous Kirtland For-mation, a reversed polarity site 0.8 m above thebase of the Paleocene Ojo Alamo Sandstone, twonormal-polarity sites higher in the Ojo Alamo, and areversed site 14.2 m above the base of the OjoAlamo. Thus, the normal-polarity interval (lowerpart of C29n) is 7.1 m thick here and is bracketedby reversed-polarity intervals within the Ojo Alamo.The Ojo Alamo Sandstone is mostly sandstone atthis locality without the distinct lower conglomerateand middle “shaly” parts found at the South Mesa,Barnum Brown Amphitheater, and Barrel SpringArroyo localities.

400

175

200

225

250

275

300

325

350

375

270 0 90 180 270 -90 +900

Ojo AlamoSandstone

Ash J73.04 0.25 Ma+ -

+ -

Ash H73.37 0.18 Ma+ -

+ -

Ash 474.55 0.29 Ma

Farmington Sandstone Member of Kirtland Formation

Lower Shale Member of Kirtland Fm.

FruitlandFormation

Declination Inclination

de

B eti

not

ne

B oti

nafr

eu

H e

vo

ba sr

ete

m - n

oitiso

p ci

hp

argit

artS

Top C33n

C33n

C29n

73.50 0.19

C32r

C29r

Figure 14. Paleomagnetic data plot of Fassett and Steiner (1997, figure 2), and Fassett (2000, figure 11) at HunterWash locality (Figures 3, 4). Magnetic-polarity chron labels are added. (Label for chron C29n revised as discussed insection of this paper labeled “Identification of Kirtland Formation-Ojo Alamo Sandstone Magnetochrons.”) Full col-umn width indicates Cretaceous or Paleocene magnetization, two-thirds column width indicates probable Cretaceousor Paleocene magnetization, one-third column width means there is some indication of Cretaceous or Paleocenemagnetization.

20


Figure 16 is a photograph of the Ojo AlamoSandstone outcrop at the Hunter Wash locality.The sandier nature of the lower part of the OjoAlamo is readily apparent in this photograph. Rela-tively few rock samples suitable for paleomagneticanalysis could be obtained in the Ojo Alamo at thislocality because of the paucity of fine-grained mud-stone layers here. The stratigraphic levels of paleo-magnetic sample sites on Figure 15 are shown onthis photograph. All of the samples collected herewere from thin, gray, mudstone beds on relativelygentle slopes. One of the Ojo Alamo Sandstonedinosaur bones collected for chemical analysis(specimen 022899-OA1, discussed in a subse-quent section of this report) was found about 30 meast of the area shown on Figure 4 and 7.3 mabove the base of the Ojo Alamo Sandstone. Thisbone is within magnetochron C29n.

Identification of Kirtland Formation-Ojo Alamo Sandstone Magnetochrons

Figure 17 is a nearly 40 km long stratigraphiccross section from Hunter Wash to Betonnie TsosieWash through the Upper Cretaceous Kirtland For-mation and Paleocene Ojo Alamo Sandstone in thesouthwestern part of the San Juan Basin. Thiscross section illustrates the relations of the fivepaleomagnetic sections discussed above. Rever-sal boundaries are placed at the midpoint betweenthe nearest-to-the-reversal-boundary data points.

The remarkable thing about this cross section isthat it shows that every published paleomagneticsection through the Ojo Alamo Sandstone in thesouthern San Juan Basin reveals the presence of anormal-polarity interval in the lower part of the OjoAlamo. At two of the localities: HW and BBA, thisnormal interval is bracketed within the Ojo Alamoby reversed-polarity intervals. At two other locali-ties: SM and BTW, either the top or base of thenormal interval was not determined. And at onelocality: BSA, the base of this normal is not brack-eted within the Ojo Alamo.

The number of paleomagnetic sample sitesdefining this normal interval varies from two to five.The average thickness of the normal interval, asshown, is 9.1 m; the average thickness at the local-ities where the normal’s top and bottom weredetermined is 9.6 m; normal-polarity-interval thick-nesses range from at least 5.9 m at the SouthMesa locality (top not determined) to 12.8 m at theBarrel Spring locality. Thicknesses for thereversed-polarity interval C29r (between the baseof C29n and the base of the Ojo Alamo) range from1 m at Barrel Spring to 5.3 m at the South Mesalocality, and average 3.3m. (Labels of magneto-chrons on Figure 17 are shown as indicated byLindsay et al. 1981 and Fassett and Steiner 1997;a revised labeling scheme for these magneto-chrons is recommended in the “Revision of Paleo-

Farmington Ss. Mbr. of Kirtland Fm.

C29n

C29r

C28r

C32r

PALEOCENE

CAMPANIAN


Ojo AlamoSandstone

+90-90 00Inclination

0

5

-5

10

15meters

-4

0.84.2

5.0

14.2

270 90 180 270Declination

Figure 15. Large-scale view of Hunter Wash paleomagnetic section (HW on Figures 3, 4). Stratigraphic levels ofsample-collection sites for paleomagnetic analysis are shown in meters above or below the base of the Ojo AlamoSandstone. Plot is expanded-scale rendition of upper part of Hunter Wash section of Fassett (2000) of Figure 14.(Magnetochron labels for intervals shown as C29n and C28r are revised as discussed in section of this paper labeled“Identification of Kirtland Formation-Ojo Alamo Sandstone Magnetochrons.”)

21


cene-Magnetochron Designations” section of thisreport.)

The sample-collection methodology of Fassettand Steiner (1997) at Hunter Wash was differentfrom that of Lindsay et al. (1981) at the SouthMesa, Barnum Brown Arroyo, Barrel SpringArroyo, and Betonnie Tsosie Wash localities. TheFassett and Steiner samples consisted of orienteddrill cores of the rock, whereas Lindsay et al.(1981) carved out oriented blocks of rock for theirsamples. In addition, samples were processed dif-

ferently in different labs on different instruments atdifferent times. The samples for the Fassett andSteiner (1997) Hunter Wash study were obtained ata locality 9 km west of the closest part of the Lind-say et al. (1981) section (Figures 3, 4). In spite ofthese differences, the patterns of remanent mag-netic polarity resulting from these independentstudies are virtually identical. Figure 18 shows acomparison of paleomagnetic data plots from Fas-sett and Steiner (1997) and Lindsay et al. (1981).


C32r

4.2

5.0

0.8

14.2

White Sandstone

C29r

C29n.2n

C29n.1r

PALEOCENE


Figure 16. Photograph of Ojo Alamo Sandstone near head of tributary of Hunter Wash (looking north); location isshown on Figures 3 and 4. Dinosaur-bone locality 022899-OA1 (Figure 4) is near base of white sandstone bedshown in upper right of photograph and is about 30 m to southeast. This dinosaur-bone collection site is 7.3 m abovebase of Ojo Alamo Sandstone. Sample levels of paleomagnetic data points are shown in meters above base of OjoAlamo Sandstone; arrowheads pointing left indicate reversed polarity, arrowheads pointing right indicate normalpolarity. Stratigraphic levels of samples are relatively accurate, as shown, but locations are not exact. Magnetochronlabels are corrected as discussed in section of this paper labeled “Identification of Kirtland Formation-Ojo AlamoSandstone Magnetochrons.” Note vehicle in upper left on skyline for scale. See Figures 14 and 15 for paleomagneticdata plots for this area.

22


(For ease of discussion, these sections arereferred to as HW and HW/AW, respectively.)

Just above the top of C33n in the HW plot at335 m (Figure 18), there is a thin normal intervaland on the HW/AW plot a similar thin normal ispresent. Just below the top of the HW C33n normalchron, there is a thin reversed interval, and on theHW/AW plot at about the same level, there is a sin-gle-site polarity excursion that almost reachesreversed polarity. At the 370 m level there is thesuggestion of a thin normal interval on the HW dataplot; at exactly the same level on the HW/AW dataplot, two data points represent an excursion towardnormal polarity. Gradstein et al. (2004) showed athin normal interval above C33n labeled C32r.1nwith a duration of 0.087 m.y.; this chron is sepa-rated from the top of C33n by a reversed-polarityinterval (C32r.2r) of 0.239 m.y. duration. It is possi-ble, therefore, that the thin normal interval at 370 mon the HW plot is chron C32r.1N. On both the HWand HW/AW paleomagnetic plots, thin reversed

polarity intervals are present within chron C33n atthe 188-195 m interval on the HW plot. Within thisinterval there are two thin reversals on the HW plotand only one on the HW/AW plot; this differencecould be an artifact of the more closely spacedsamples collected at the HW locality. Gradstein etal. (2004) did not show this reversed interval inmagnetochron C33n, probably because the muchslower rates of crustal formation at the mid-Atlanticridge did not allow this thin reversal to be recog-nized.

There has been reluctance on the part ofsome paleomagnetists to fully embrace the poten-tial of paleomagnetic studies of sedimentary rocksbecause of the possibility of overprinting of hemati-tic minerals incorporated within those strata, butthe close agreement in the results of the two inde-pendent paleomagnetic studies discussed abovedemonstrates that such strata did accuratelyrecord and preserve the remanent magnetic polar-

Top of chron C29n not determined

Base of chron C29n not determined

C29rC32r

0

5

0

5

-5

10

15

20

25

30

meters

PALEOCENE

CAMPANIAN

?

?

?C28rHW SM

BSA

BBA

BTW

9.0 1.3 1.8 27.5

DATUM - BASE OF OJO ALAMO SANDSTONE

35

40

45

-65

-60

-55

-50

-45

-40

-35

-30

-5

10

15

20

25

30

35

40

45

-65

-60

-55

-50

-45

-40

-35

-30

LEGEND

C30nC33n

Tick marks on left side of columnare levels of paleomagnetic data;red ticks are sites with a lowerconfidence level.

PALEOMAGNETIC-COLUMN FIGURE REFERENCES

Column Pmag data plot Photograph

HW Figures 14, 15 Figure 16

SM Figures 8, 9 Figure 10

BBA Figure 5 Figure 7

BSA Figure 5 Figure 6

BTW Figure 12 Figure 13

Locality name

Hunter Wash

South Mesa


Barrel Spring Arroyo


meters

39.6 km

km

C29nC29nC29rC32r

C28r

C28r

C29n

C28n

C28r

C29rC29r C29r

C29n

Top - Ojo Alamo SsTop - Ojo Alamo Ss

C29n

C28n

vertical exaggeration = X 258

-10 -10

?

Figure 17. Cross section through five published paleomagnetic sections in southwestern San Juan Basin. (Sectionlocalities are shown on Figures 3 and 4; full data plots for all sections are on the figures indicated.) Section HW fromFassett and Steiner (1997), four other sections from Lindsay et al. (1981); labels of magnetochrons and top of OjoAlamo Sandstone are as shown by those authors. (Some magnetochron labels shown are now known to be incor-rect as discussed in section of this paper labeled “Identification of Kirtland Formation-Ojo Alamo Sandstone Magne-tochrons.”) Columns are broken by a gap of 25 m to show position of top of chron C33n (C30n of Lindsay et al. 1981)at Hunter Wash and South Mesa localities at a reasonable scale. Alignment of column BTW is based on field mea-surements of distance from lowermost C29n data point to base of Ojo Alamo Sandstone at BTW locality.

23


ity of the earth’s magnetic field at the time thoserocks were deposited.

Because the Ojo Alamo Sandstone wasdeposited on an erosion surface, using the base ofthe Ojo Alamo as a horizontal datum (Figure 17) ismisleading for comparing thicknesses of the OjoAlamo normal intervals at the five localities. Figure19 reconfigures the upper part of this cross sectionusing the base of the Ojo Alamo normal interval—atime horizon—as a datum. The boundaries of theOjo Alamo normal interval are adjusted on Figure19, to the extent reasonably possible, to makethese intervals as close as possible to the samethickness at each locality, while still honoring thesample-polarity data. In addition, the SM and BTWnormal intervals are extended to match the topsand bases of the adjacent normal intervals. Theresults of this interpretation show that the OjoAlamo Sandstone normal-polarity interval is about11 m thick at all localities, and the maximum reliefon the pre-Ojo Alamo erosion surface is about 4 m.These thicknesses are reasonable because therates of sediment accumulation across this rela-tively small area were probably uniform, thus thethickness of the Ojo Alamo normal at these locali-ties should be nearly the same.

Figure 20 is a modification of figure 7 of Butlerand Lindsay (1985). These authors stated that:“Data from sites where evidence indicates normalpolarity VRM [viscous remanent magnetism] over-printing are indicated with lines through the datapoints.” but they are unclear as to why these partic-ular sites were considered to be overprinted. Notethat the Barrel Spring and South Mesa localitiesare shown (Figure 20) to contain two “overprinted”normal sites, and the Barnum Brown section hasone “overprinted” normal site. Butler and Lindsay(p. 543) stated that one of the features “crucial” totheir interpretation was that “these reversed polar-ity sites occur throughout the stratigraphic intervalfrom which + [C29n] was originally defined..

This statement is puzzling because there isonly one reversed-polarity site shown within theiroriginal C29n chron, and that site is at the BarnumBrown locality (Figure 20, site 7). The reversed-polarity site shown on this figure is at exactly thesame level as a reversed-polarity site shown to bepresent at Barnum Brown by Lindsay et al. (1981)on their figure 7 (Figure 5 of this report), and thesignificance of this reversed site at that locality wasdiscounted in the Lindsay et al. (1981) report.Therefore the “crucial” evidence purporting to dis-

400

175

200

225

250

275

300

325

350

375

270 0 90 180 270 -90 +900

Ojo AlamoSandstone

Ash J73.04 0.25 Ma+ -

+ -

Ash H73.37 0.18 Ma+ -

+ -

Ash 474.55 0.29 Ma

Farmington Sandstone Member of Kirtland Formation

Lower Shale Member of Kirtland Fm.

FruitlandFormation

Declination Inclination

de

B eti

not

ne

B oti

nafre

uH

evo

ba sret

em -

noitis

op ci

hpar

gitartS

Top C33n

C33n

C29n

73.50 0.19

C32r

C29r C29r

Lindsay, Butler, and Johnson (1981, fig. 6) Hunter Wash/Alamo WashFassett and Steiner (1997, fig. 2), Hunter Wash


C32r

C29n

C33n

C32r.1n (?)

C32r.1n (?)

Ojo AlamoSandstone

KirtlandFormtion

FruitlandFormtion

Meters

150

125

DATUMS

Figure 18. Comparison of independent paleomagnetic studies at two nearby sections in type area of Ojo AlamoSandstone in southwestern San Juan Basin (see Figure 4 for locations); the two localities are 9 km apart; modifiedfrom Lindsay et al. 1981. The two sections are aligned on top of chron C33n and base of chron C29n. Chron labelson Lindsay et al. figure are corrected from their original designations as discussed in section of this paper headed“Identification of Kirtland Formation-Ojo Alamo Sandstone Magnetochrons.”

24


prove the presence of normal-polarity intervalC29n in the lower part of the Ojo Alamo was notprovided in Butler and Lindsay (1985).

Butler and Lindsay (1985), in their reexamina-tion of the paleomagnetic-normal interval in the OjoAlamo Sandstone at South Mesa, Barnum BrownAmphitheater, and Barrel Spring Arroyo, concludedthat their earlier determinations that this normalrepresented true remanent magnetism were inerror. Instead, they stated that this normal intervalrepresented a present-day, normal-field overprintthat should be removed from their paleomagneticsections in the southern San Juan Basin. Theyoffered no mechanism for how present-day normaloverprinting might have occurred at these threeseparate localities. Photographs of the Ojo AlamoSandstone at these localities (Figures 6, 7, 10)show that the exposures are all in barren badlandsthat are eroding at a relatively rapid rate. Becausesamples for paleomagnetic analysis by Lindsay etal. (1981) and Fassett and Steiner (1997) were col-lected from fresh bedrock, never more than 1 mbelow the surface, any present-day normal over-printing would have had to occur within the lastthousand years or so, at most. Thus, there is noconceivable mechanism for such overprinting of a

normal-polarity interval in the lower Ojo Alamo,with virtually identical thicknesses, at three topo-graphically different and separate localities. More-over, normal intervals at two localities are overlainand underlain by reversed-polarity sites making itextremely unlikely that an 11 m thick interval in thelower part of the Ojo Alamo could have been over-printed by the present-day normal magnetic fieldwhile the overlying and underlying rocks, also con-taining titanohematite, were not similarly over-printed. Thus, the Butler and Lindsay (1985)contention that the Ojo Alamo normal interval atthe three South Mesa localities is a present-daynormal overprint is rejected.

Lindsay et al. (1981) also identified a paleo-magnetic normal interval in the lower Ojo AlamoSandstone at the Betonnie Tsosie Wash locality.The presence of this normal interval was not ques-tioned in the Butler and Lindsay (1985) paper, thusit can only be concluded that these authorsbelieved that the Ojo Alamo normal interval at thislocality, at least, did represent true Paleoceneremanent magnetism. All available evidenceshows that the paleomagnetic-normal intervalpresent within the Ojo Alamo Sandstone at the fivelocalities discussed herein, must represent true


Base of chron C29n not determined

0

5

-5

10

15

20

25

30

meters

CAMPANIAN

?

?

C29nC29n

C29rC32r

C28rC28r

C28rHW

SM

BSA

BBA

C29n

BTW

C29n

9.0 1.3 1.8 27.5

35

40

45

0

5

-5

10

15

20

25

30

35

40

45

C28n

C28n LEGENDmeters

C28r

39.6 km

km

C29n

Top - Ojo Alamo Ss

DATUM - Base of magnetochron C29nBase of OA Ss Base of OA Ss

PALEOCENE

vertical exaggeration = X 276

Top - Ojo Alamo Ss

-10 -10

Tick marks on left side of columnare levels of paleomagnetic data;red ticks are sites with a lowerconfidence level.

Probable extension of normal-polarity interval C29n

C29rC29r

C29r

?

?

?

Figure 19. Stratigraphic cross section through five paleomagnetic sections in southwestern San Juan Basin (modifiedfrom Figure 17) using base of magnetochron C29n instead of base of Ojo Alamo Sandstone as a datum. Columnlocalities shown on Figures 3 and 4. Column headings and figure references described on figure 17. Section HW fromFassett and Steiner (1997), four other sections from Lindsay et al. (1981); labels of magnetochrons are as shown bythose authors. Alignment of column BTW based on field measurements of distance from lowermost C29n data pointto base of Ojo Alamo Sandstone at BTW locality. (Some magnetochron labels shown are now known to be incorrectas discussed in section of this paper labeled “Identification of Kirtland Formation-Ojo Alamo Sandstone Magneto-chrons.”)

25


Paleocene remanent magnetism. Thus, the pres-ence of paleomagnetic normal interval C29n in thelower part of the Ojo Alamo Sandstone confirms itsPaleocene age. In addition, because the base ofmagnetochron C29n has an age of 65.12 Ma(Gradstein et al. 2004) and because the base ofthis chron is near the base of the Ojo Alamo, theage of the base of the Ojo Alamo can be estimatedto be about 65.2 Ma. These findings are furthersupported by paleomagnetic data obtained atMesa Portales, as discussed below.

Mesa Portales Study Area

Geography and Stratigraphy. Mesa Portales isabout 17 km southwest of Cuba, New Mexico (Fig-ures 3 and 21). The mesa is capped by the Paleo-cene Ojo Alamo Sandstone, which forms a gentledip slope (from 1 to 1.5 degrees) dipping to thenorth; the south edge of the mesa is a steep,south-facing, 130 m high cliff face. The Upper Cre-taceous Lewis Shale, Pictured Cliffs Sandstone,and the undivided Fruitland and Kirtland Forma-tions underlie the Ojo Alamo and are well exposedat this locality. These exposures are within theMesa Portales study area (Figure 21). Fassett(1966) mapped the Ojo Alamo Sandstone on MesaPortales and observed that it consisted of discon-tinuous, sheet-like, “overlapping massive beds of

light- to rusty-brown fine- to coarse-grained sand-stone that contain scattered silicified wood andconglomerate and are separated by light- to dark-gray and green shale.”

In the photograph of the Mesa Portales studyarea (Figure 22), the Ojo Alamo Sandstone is seento consist of two sandstone benches; the upperbench is continuous whereas the lower benchpinches out to the east about one-third of the dis-tance from the east edge of the photograph. On thegeologic map of the Mesa Portales quadrangle(Fassett 1966), the base of the Ojo Alamo shiftsfrom the base of the lower bench to the base of theupper bench where the lower bench pinches out.At other places on Mesa Portales, there are asmany as five distinct sandstone benches includedin the Ojo Alamo (Fassett 1966). Below the lowestsandstone bench (Figure 22) there is a discontinu-ous sandstone interval. This interval pinches outeast and west of the area shown on Figure 22.Even though the base of this sandstone intervalclearly marks the Cretaceous-Tertiary interface atthis locality, in other areas where this lower sandyinterval is not present, there is a shale-on-shalecontact marking that interface. Because this lowersandy interval is not a distinct, continuous, mappa-ble unit, it was not included in the rock-stratigraphicOjo Alamo Sandstone on Mesa Portales of Fassett

Meters

0

10

20

OjoAlamo Ss.

Kirtland Fm.

-90 +900 -90 +900 -90 +900

SOUTH MESA

BARNUM BROWN BARREL SPRING

C29n C29n C29n

Virtual geomagnetic pole latitude

74

8

10

Figure 20. Stratigraphic columns and paleomagnetic plots at South Mesa, Barnum Brown Amphitheater, and BarrelSpring Arroyo (Figure 4), modified from Butler and Lindsay (1985). Figure shows positions of original paleomagneticnormal intervals (C29n) of Lindsay et al. (1981). Tick marks on left side of columns show levels of original samplesites of those authors; red tick marks indicate sites with normal polarity.

26


(1966). A detailed discussion of the Ojo AlamoSandstone on Mesa Portales is in Fassett andHinds (1971, p. 29-31). The Fruitland-Kirtland inter-val is only 100 m thick in the Mesa Portales studyarea (Figure 23), whereas this interval is 400 mthick in the Hunter Wash area to the northwest(Figures 3, 14). The thinning of this interval south-

eastward along the south rim of the San JuanBasin is discussed in detail in a separate section ofthis report.Paleomagnetic Analysis. Paleomagnetic sam-pling at Mesa Portales was conducted along adiagonal traverse (from lower left to upper right) upthe face of the exposure shown on Figure 22. Sam-

Ojo Alamo Sandstone

5

8

18

6

14

2

18 17

11

15 1416

OA-2

Rio

Rio

Puerco

Puerco

CubaHighSch.

126

Tsj

107º

OA-1

Mesa Portales

Mesa Portales

Mesa Portalesstudy area

9

3135

6 2

31 34

22

T. 20 N.

T. 21 N.

R. 3 W. R. 2 W.

R. 1 W.

R. 3 W. R. 2 W.

T. 19 N.

T. 20 N.

20

Cuba

36

16 14

26

9

16

197

197

197

Fork Rock Mesa

CR 13

CR 13

CR 11

23

Upp

er

C

reta

ceou

s

KF

D6582

Paleocene palynomorph assemblages

Late Cretaceous palynomorph assemblage

LEGEND

N-2

N-1

Ammonite locality; Lucas and Sealey (1992)

D3803

22

34 36

23 24

R. 2 W.

Mesa

de

Cuba

D6878

Fed. 11-D 1

Nacim

iento

Form

ation

San Jose Formation550

Rio

Puerco

19

550

Fossil-mammal localities; Simpson (1957)

Dated ash bed

Figure 21. Geologic map showing outcrop of Ojo Alamo Sandstone in southeastern San Juan Basin (Figure 3). MesaPortales study area contains paleomagnetic section across Cretaceous-Tertiary boundary and multiple USGS paleo-botany localities through the same strata. OA-1, OA-2, KF, and N-1, N-2 (southwest and northeast of Cuba) arepalynologic-collection localities of Anderson (1960). D6878, D3803, and D6582 are USGS paleobotany localities;palynomorphs from these sites are listed in the Appendix. Geology west of long. 107° W. and south of the northernboundary of T. 20 N. from Fassett (1966); geology for the rest of area from Baltz (1967).

27


ple collection was conducted by E.M. Shoemaker(USGS), M.B. Steiner (U. Wyoming), and theauthor in 1983; in 1988, Steiner and the author col-lected additional samples to fill in gaps in the origi-nal 1983 sampling. The only publication resultingfrom this work was an abstract by Shoemaker et al.(1984) summarizing the paleomagnetic dataobtained at Mesa Portales in 1983. Figure 23shows the paleomagnetic data plot and a strati-graphic column for the Mesa Portales locality. Dig-ging through the weathered-rock rind down tounweathered bedrock was required at many sam-ple sites, generally to depths of about 0.1 m or so,but in some places to a meter or more. Samples ofthe freshly exposed bedrock were obtained by coredrilling.

The following discussion of the paleomagneticanalysis of Mesa Portales samples is slightly modi-fied from a report by M.B. Steiner (personal com-mun., 1989).

Natural remanent magnetism (NRM) direc-tions for Mesa Portales samples varied betweenCretaceous normal, axial field, present field, andLate Cretaceous and early Paleocene reversedand normal directions. A reversal from normalpolarity to reversed polarity was found in the NRMdirections in the Cretaceous part of the section(Fruitland-Kirtland Formations) between 60 m and68 m above the base of the sampled section (Fig-ure 23); this reversal is estimated to be at the 64 mlevel (Figure 23). Another reversal, from reversedto normal polarity, was discovered in the Paleo-cene Ojo Alamo Sandstone between the 119 m

Pictured Clffs Ss

Upper Bench - OA Ss

Lower Bench - OA Ss

PALEOCENE


C33n

C29r

C29n

D 4017-B

D 4017-C

D 3738-C

D 3738-A

D 6583-AD 6583-BD3738-B

D 4017-A

D 6626-A,B,C

C32r

73.50 Ma

Tree

Basal Paleocene sandstone bed

Kirtland andFruitland Formation undivided

Figure 22. Photograph of south-facing cliff of Mesa Portales (Figures 1, 3, 21). Photograph annotated to show rele-vant chronostratigraphic data, sample-collection localities, geologic contacts, and names of geologic rock units. Apaleomagnetic traverse was made up the face of this exposure, angling from the lower left to just below base ofupper Ojo Alamo Sandstone bench in shadowed area just left of labeled tree. Palynologic sample-collection sitesand USGS paleobotany locality numbers, such as D 4017-A, are shown with arrowheads. Sample locations areapproximate; however, stratigraphic levels are accurately placed. Palynomorphs identified from these collectionlocalities are listed in the Appendix.

28


29

270 2700 90 180

0

Meters

Declination Inclination-90 +900

Palynologysample nos.

D 3738-A

D 6626-A,B,C

D 4017-BD 4017-A

D 4017-A - Contains Tschudypollis spp.(Proteacidites spp.)

D 3738-C

D 4017-C

D 3738-B

PALEOCENE LATECRETACEOUS(CAMPANIAN)

C29r

C29n

C32r

C33n

D 6583-B

D 6583-B - Contains no Tschudypollis spp. plus Momipites tenuipolus

D 6583-A

D 6583-A - Contains no Tschudypollis spp.

Magnetochrons

Stratigraphic Column

Ojo

Alamo

Sandstone

Pictured

CliffsSandstone

LEGEND


~ 8 m.y. hiatus

10 m

100

110

120

50

40

30

20

10

60

70

80

90

Kirtland/

Fruitland

Formation

undivided

?

?

Figure 23. Paleomagnetic data plot and stratigraphic column at Mesa Portales, southeastern San Juan Basin, NewMexico (locality on Figure 21). Stratigraphy of section from Fassett (1966) and Fassett and Hinds (1971). Palyno-morphs from rock samples from this section identified by R.H. Tschudy (personal commun., 1966, 1967, 1968, 1983,1984); palynomorphs identified in tables in the Appendix. Paleomagnetic data plot provided by M.B. Steiner (personalcommun., 1992). Samples for Mesa Portales paleomagnetic study were collected by E. M. Shoemaker, M.B. Steiner,and the author in 1983 and 1989; lab analyses of samples were conducted by Steiner and Shoemaker. On paleo-magnetic column, full column width indicates latest Cretaceous-earliest Paleocene magnetization; two-thirds columnwidth indicates probable latest Cretaceous-earliest Paleocene magnetization. An annotated photograph of section isFigure 22. Cretaceous index palynomorph Tschudypollis was originally named Proteacidites.


and 122 m levels (Figure 23); this reversal isplaced at the 121 m level.

NRM intensities were typically 1 x 10-3 AIM (lx10-6 emu/cc). A small number of samples fromboth sandstone and mudstone beds had intensitiesof 1 x 10-2 AIM (10-5 emu/cc) and some rangeddown to 1 x 10-4 AIM (10-7 emu/cc). Intensities ofheavy-mineral laminae were as much as 2 x 10-1

AIM (2 x 10- 4 emu/cc). NRM directions of theselayers were clearly of Late Cretaceous-earliestPaleocene origin.

Pilot samples were demagnetized using alter-nating field (AF) and thermal demagnetization. Tensamples were AF demagnetized to 100 mT (1000oe). Thirty samples were thermally demagnetizedin steps of 25 degrees between 150° C and 400°C. Another 32 samples were thermally demagne-tized to 200° C and then AF demagnetized to 15mT. The remainder of the samples was thermallydemagnetized in five steps between 170° C and325° C. Subtracted vectors were computedbetween demagnetization steps, and characteristicdirections were determined by a least-squaresanalysis of lines fit to the demagnetization trajecto-ries.

AF demagnetization indicated a mediandemagnetizing field of between 12.5 and 20 mT.Demagnetization to as high as 100 mT, however,did not always engender stable directions and (or)decay to the origin of orthogonal axes plots. Ther-mal demagnetization was performed on specimenscut from the same core as the samples that wereAF demagnetized. These data displayed the samedirection as AF treatment for those samples forwhich AF caused decay to the origin; for thosespecimens that did not, thermal demagnetizationrevealed a trend (generally incomplete) toward anapparent reversed-polarity magnetization. Ther-mal demagnetization indicated a magnetizationcomponent stable between 200° C and 300° C,having antipodal directions.

Another group of samples was thermallydemagnetized to 200° C and then AF demagne-tized to 15 mT. The directions at 200° C are gener-ally representative of the normal or reverseddirections later shown to be characteristic fromwholesale thermal demagnetization. Furtherdemagnetization of the 200° C thermally demagne-tized samples by AF demagnetization to 15 mT didnot reduce intensities further nor induce any appre-ciable continuation of the demagnetization trendbegun by thermal demagnetization. Further ther-mal demagnetization above 200° C generallyremoved an additional amount of magnetization

and continued the demagnetization trend begunbelow 200° C. In most cases, this demagnetizationrevealed a direction closer to the characteristicmean, but above 300° C an increasing dispersionof directions was observed. These findings indicatean antipodal magnetization with coercivities around16 mT and unblocking temperatures between 200°C and 300° C and the presence of secondary mag-netization(s) having higher coercivity and unblock-ing temperatures.

The greater effectiveness of thermal demag-netization dictated that the majority of samples bedemagnetized by thermal means. As mentioned,the characteristic directions appeared to be heldbetween 200° C and 300° C as is indicated in sev-eral ways: above 300° C, directions generallybecame erratic or diverged from a trend toward theorigin. Moreover, visual inspection of the directionsof the sample population at each temperature stepindicated that the dispersion among directionsbegan to increase at 300° C, and continued toincrease with each succeeding temperature step. A50% reduction in NRM intensity occurred between200° C and 300° C for most normal, and somereversed, samples. Finally, the polarity sequencesindicated by directions below 325° C is very sim-ple, showing a well-defined change from normal toreversed polarity at 64 m above the base of thesection in Cretaceous strata and from reversed tonormal polarity at 121 m (Figure 23). The polaritysequences became more complex and stratigraph-ically inconsistent when directions above 300° Cwere considered.

Heavy mineral laminae in massive sandstonebeds between about 70 and 84 m (Figure 23) weresampled extensively (21 samples). (These sand-stone beds are the buff-colored beds seen justabove the “C32r” label on Figure 22.) The samplesgenerally had clearly defined reversed directionswith only minor influence of secondary magnetiza-tion on the NRM and remanence held below 300°C. As in the other samples from Mesa Portales, thecharacteristic magnetization is held between 200°C and 300° C, above which the intensities diminishrapidly, and directions become more erratic. Sev-eral of the samples indicated the presence of twoslightly different directions, one generally heldbelow 300° C and the other above. The demagneti-zation trajectories of the heavy-mineral samplesare more ragged than many other heavy-minerallaminae (Steiner 1983), which may reflect thesuperposition of the reversed overprint observed inthe Mesa Portales section in general onto a pri-

30


mary reversed detrital or post-depositional rema-nence in these concentrates.

Curie temperatures were measured on theheavy mineral laminae collected at about 78 mabove the base of the section. These displayednearly reversible thermomagnetic curves withCurie/Neel temperatures of about 210° C. In alarge-scale study of San Juan Basin sections, Lind-say et al. (1981) stressed the necessity of collect-ing mudstones to ensure that good magneticremanences are obtained. The Cretaceous part ofthe Mesa Portales sequence (Figures 22 and 23)consists of mixed sandstone-mudstone lithologiesand contains several massive sandstone beds inits upper part (Figure 22). To obtain an adequatesample-spacing pattern, large numbers of sand-stone samples were collected in the section. Mostof these samples were from the normal-polaritypart of the section in the undivided Fruitland-Kirt-land Formation. A comparison of directions andintensities of paleomagnetism of the mudstonesand sandstones throughout the Mesa Portalesstratigraphic section showed no differences inmean direction or polarity between the two litholo-gies. The uppermost (Paleocene) part of the MesaPortales section is dominated by massive, cliff-forming sandstone beds (Figures 22 and 23); thesebeds were not sampled for paleomagnetic analy-sis.

Sample-site density for the entire sectionaveraged about one site per meter except for twosignificant gaps between the 60 and 69 m level andthe 98 to 108 m level (Figure 23). The lower 9 mgap is in the prominent white sandstone bed (Fig-ure 22) that is above the coaly interval where theD-4017A, B palynologic samples were collected;the magnetic-polarity reversal from C33n to C32rfalls within this white sandstone. The upper 10 mgap is mostly in the lower, sandy, Paleocene strataabove the unconformity at the Cretaceous-Tertiaryinterface (Figure 22). When these two gaps aresubtracted from the total-section thickness, sam-ple-site spacing is about 0.80 m. Generally, threeor more samples per site were collected.

The bulk of the paleomagnetic sample analy-sis was conducted by M.B. Steiner at the Universityof Wyoming paleomagnetism lab. Samples fromselected intervals were also processed at theCaltech paleomagnetism lab by Joe Kirschvink forE.M. Shoemaker. Shoemaker stated (personalcommun., 1984):

Enclosed is a listing of results on the Mesa Portales samples run at Caltech in Joe Kirschvink's laboratory. All samples

were thermally demaged [demagnetized] first at 150° C, so we have a good record for this temperature. All of these (except KMP 0.01) were also demaged at 200°C; in all cases the shift in direction from 150° to 200°C is relatively small and the loss of magnetization less than 50%, usually much less than 50%. Hence, demagnetization to 200°C does not appear to be pushing too deep to retain the stable component of primary magnetization (Curie T = 180°C to 300°C according to Butler[“Butler” refers to Butler and Lindsay 1985]). All samples were also AF demagnetized in steps to 150 Oe. Only samples 175.61 [54 m] and 183.0 [56 m] seemed to shift significantly toward the opposite polarity at these low fields.The two samples at 54 m and 56 m (Figure

23) that “seemed to shift significantly toward theopposite polarity” are at about the same levelbelow the top of C33n as the thin reversed-polarityinterval seen at the Hunter Wash section (Figure18).Paleomagnetic Data Plot. The final plot of themagnetic polarity of the samples from Mesa Por-tales (Figure 23) incorporates both Steiner’s andShoemaker’s data. This plot shows the presence ofa normal-polarity interval from the base of the sec-tion in the Pictured Cliffs Sandstone to the 64 mlevel in the Fruitland-Kirtland sequence (Figure23). This normal-polarity interval is overlain by areversed-polarity interval extending to the K-Tinterface at the 100 m level. Another reversed-polarity interval extends from the K-T interface tojust above the 120 m level; this reversed-polarityinterval is overlain by a normal-polarity intervalabout 5 m thick that extends to the top of the paleo-magnetic section. The normal and reversed inter-vals in the Cretaceous strata are identified as C33nand C32r as discussed in the “Fassett and Steiner(1997) - Hunter Wash Paleomagnetic Section” sec-tion of this report. The Cretaceous part of the MesaPortales paleomagnetic section bears a remark-able similarity to that part of the Lindsay et al.(1981) Cretaceous section at their Hunter Wash/Alamo Wash locality and the Fassett and Steiner(1997) section at Hunter Wash (Figure 18). Themain difference is that the reversed-interval C32r is61 m thick in the Ojo Alamo type area vs. 35 mthick at Mesa Portales. A zone of thin, reversed-polarity intervals in the upper part of C33n also is

31


common to the Mesa Portales and Hunter Washsections (Figures 18, 23).

The Paleocene part of the Mesa Portales dataplot is shown at larger scales on Figure 24. Thedistances, in meters, of paleomagnetic samplesites below the base of the upper Ojo Alamo Sand-stone bench are shown on Figure 24.2. Thereversed and normal magnetochrons above theCampanian-Paleocene interface are labeled C29rand C29n, respectively. (The identification of thesechrons is discussed in the following section of thisreport.) Figure 25 is an annotated photograph ofthe upper part of the Ojo Alamo Sandstone atMesa Portales showing the locations of paleomag-netic sample sites on the upper cliff face. This fig-ure shows that the paleomagnetic samples fromthe upper Ojo Alamo were collected from a rela-tively steep slope. Sample 5.3 was from a dark-gray mudstone, samples 2.7, 2.3, and 1.8 werefrom light-gray, silty mudstones, and the uppermostfour samples were collected from a greenish-brownsiltstone beneath the overhang of the upper OjoAlamo Sandstone bench; sample numbers arekeyed to Figure 24.2.

Revision of Paleocene-Magnetochron Designations

Figure 26 contains two cross sections thatshow paleomagnetic sections in the southern SanJuan Basin that included the Ojo Alamo Sand-stone. Figure 26.1 shows the magnetochron labelsof Lindsay et al. (1981) and Fassett and Steiner(1997). Figure 26.2 shows the revised labeling ofthese magnetochrons of this report. The datum forthese cross sections is the pre-Ojo-Alamo-Sand-stone unconformity (Cretaceous-Paleocene inter-face).

Figure 27 shows the magnetic polarity of thelowermost Paleocene using all available data andusing the base of chron C29n as a datum. HW dataare from Fassett and Steiner (1997), MP data arefrom this report, and all other paleomagnetic dataare from Lindsay et al. (1981). The labeling of themagnetochrons on Figure 27 is different from publi-cations by Lindsay et al. (1981), Butler and Lindsay(1985), and Fassett and Steiner (1997). The lower-most normal-polarity interval in the Ojo AlamoSandstone is here labeled C29n.2n. This chronwas labeled C29n in Lindsay et al. (1981), wasdeleted from the section in Butler and Lindsay(1985), and was labeled C29n in Fassett andSteiner. The overlying reversed-polarity interval islabeled C29n.1r; this chron was called C28r inLindsay et al. (1981), was the upper part of C29r in

Butler and Lindsay (1985), and was C28r in Fas-sett and Steiner. C28r of Figure 27 was C27r ofLindsay et al. (1981), was C28r of Butler and Lind-say (1985), and was not discussed in Fassett andSteiner (1997). Chron C28n of Figure 27 was C27nof Lindsay et al. (1981) and C28n of Butler andLindsay (1985).

The magnetochron-numbering scheme shownon Figure 27 is very similar to that of Butler andLindsay (1985), with one important difference. Thelowermost normal interval in the Paleocene;C29n.2n of Figure 27, was deleted from the Butlerand Lindsay (1985) paleomagnetic section in thesouthern San Juan Basin, however, this thin nor-mal interval has been found to be ubiquitous andvirtually of the same thickness at all localitieswhere paleomagnetic data have been obtainedfrom the Ojo Alamo. The reversed-polarity interval:C29n.1r (Figure 27) is a newly identified reversedinterval in the lower part of chron C29n. This inter-val, with a duration of about 0.07 m.y., has notbeen recognized in the basal part of C29n hereto-fore. The inclusion of chrons C29n.1r and C29n.2nin magnetochron C29n gives this chron an averagethickness of about 70 m in the San Juan Basin(Figure 27). With a duration of 0.685 m.y. (Grad-stein et al. 2004), the rock strata encompassingC29n has a sedimentation rate of 102 m/m.y. (notdecompacted). This rate seems reasonable whencompared to the sedimentation rate calculated foruppermost Cretaceous strata of 142 m/m.y. (Fas-sett 2000). Previous studies by Lindsay et al.(1981) and Fassett and Steiner (1997) assumedthat the 11-m thick normal magnetochron in thelower Ojo Alamo Sandstone represented all ofchron C29n. Using that thickness for C29n wouldyield a sedimentation rate of 16 m/m.y.; a rate thatis unrealistically too low.

The labeling of Paleocene magnetochronsshown on Figure 27 is considered to be a best-fitinterpretation of existing data. Other interpretationsare possible, such as placing the lowermost OjoAlamo Sandstone normal interval in magnetochronC29r and labeling it C29r.1n. Because the averagethickness of C29n.2n is 11 m, and the thickness ofC29n.1r is only about 7 m, it was thought that theplacement of C29n.2n within C29n was the mostparsimonious solution. It is clear that supplemen-tary paleomagnetic studies of lowermost Paleo-cene strata in the San Juan Basin would beextremely useful in clarifying these relations. Mostuseful of all would be the precise dating of lowerPaleocene strata in the basin using 40Ar/39Ar sin-

32


33


C29r

C29r

C32r

0

5

-5

10

15

270 2700 90 180


C29n

20

25

30

35

meters

PALEOCENE

CAMPANIAN


meters magnetochrons stratigraphy

Kirtland andFruitlandFormationsundivided

lowersandstone bench

lowersandstone bench

uppersandstone bench

Ojo AlamoSandstone

?

?

?

10270 2700 90 180


0

5

0.2

Top of chron C29n not determined?

0.40.81.01.82.3

2.7

5.3

6.8

24.1

Ojo AlamoSandstone

u. ss bench

24.2

C29n

Figure 24. Large-scale views of upper part of paleomagnetic section at Mesa Portales (from upper part of paleomag-netic section of Figure 23). 24.1 Blow-up of entire Ojo Alamo Sandstone part of section; 24.2 Expanded view of paleo-magnetic collection sites in upper part of magnetochrons C29r and C29n. Numbers of sample levels are in metersbelow base of upper massive sandstone bed of Ojo Alamo Sandstone.


gle-crystal-sanidine or other state-of-the-art radio-metric-dating methods.

Figure 27 shows an irregular erosion surfaceat the base of the Paleocene across the basin witha 21 m topographic low on the pre-Paleocene landsurface in the Mesa Portales area. Fassett andHinds (1971, figure 13) showed an isopach map ofthe interval from the Huerfanito Bentonite Bed ofthe Lewis Shale to the base of the Ojo AlamoSandstone (reproduced herein as Figure 1.1);those authors suggested that because the Huer-fanito Bed is a time plane (a volcanic ash fall intothe Western Interior Seaway), this isopach mapshould represent the approximate topography ofthe land surface prior to deposition of the OjoAlamo Sandstone. Fassett (1985) discussed theevolution of the pre-Ojo Alamo Sandstone erosionsurface and offered illustrations (figures 3, 4)showing possible drainage patterns on that surface

at the end of the pre-Ojo-Alamo-Sandstone erosioncycle. Fassett suggested in that paper that thestrong perturbations (bulges to the east) of the 600and 700 ft contour lines in the southeast part of thebasin (Figure 1.1) represented erosion channels onthe pre-Ojo-Alamo surface suggesting relativelyhigh relief near the Mesa Portales area. Thus, thepresence of 20 m of relief on the erosion surface inthe Mesa Portales area is not unreasonable.

Moncisco Mesa and Eagle Mesa Localities

Butler and Lindsay (1985) presented newpaleomagnetic data from uppermost Cretaceousstrata at two widely separated localities MonciscoMesa and Eagle Mesa (Figure 1). The data plotsfor these two localities are shown on Figure 28. AtMoncisco Mesa, the sampled section is 140 m longand contains 16 sample sites; a sample spacing ofabout 9 m. At Eagle Mesa the section is about 80

Tree

D 3738-A

C29n

C29r

Upper Ojo Alamo Sandstone bench

0.20.4

1.0

1.8

2.32.7

5.3

0.8

Figure 25. Photograph of upper part of Mesa Portales paleomagnetic section showing approximate locations ofseven sample-collection sites of normal polarity (white arrows pointing left) and one sample of reversed polarity(white arrow pointing right). Numbers at arrows are distances in meters below the base of upper Ojo Alamo Sand-stone bench (Figure 22). Palynologic collection locality for sample D 3738-A is also shown. Tree in upper right of pho-tograph is also labeled on Figure 22 to indicate location of this photograph.

34


35

Top of magnetochron not determined

Base of magnetochron not determined

C29r

C32rC32r

C32r

0

5

-5

10

15

C29n20

25

30

meters

PALEOCENECAMPANIAN

?

?

?

?

?

?

C29n

C29r

C28r

HW

MP

C29n

9.0 1.3 1.8 27.5 72.5 k m

DATUM - Pre-Ojo Alamo Ss unconformity

112 km

35

40

45

-65

-60

-55

-50

-45

-40

-35

-30

0

5

-5

10

15

20

25

30

meters

35

40

45

LEGEND

C33n

Tick marks on left side of columnare levels of paleomagnetic data


Column Pmag data plot(s) Photograph(s)






MP Figures 23, 24 Figures 22, 25

Locality name

Hunter Wash

South Mesa




Mesa Portales

C32r

C33n

C29r

C30n

C29n

C28rSM

BSA

BBA

C29n

C28n

C28r

C29n

Top - Ojo Alamo Ss

Top - Ojo Alamo Ss

C28r

BTW

C29n

C28n

C29n

-65

-60

-55

-50

-45

-40

-35

-30

Vertical exaggeration = X 780

C29r

C32r

C32r

0

5

-5

10

15

C29n20

25

30

meters

PALEOCENECAMPANIAN

C29n.2n

C29n.1r

C29n.1r

C29n.1r

C29n.1r

C29r C29r C29r

C32r C32r C32rC32r

HW

MP

C29n

9.0 1.3 1.8 27.5 72.5 k m


112 km

35

40

45

-65

-60

-55

-50

-45

-40

-35

-30

0

5

-5

10

15

20

25

30

meters

35

40

45

C33n

C32r

C33n

C32r

C33n

SM

BSA

BBA

Top - Ojo Alamo Ss

Top - Ojo Alamo SsBTW

C29n

-65

-60

-55

-50

-45

-40

-35

-30

C29r


26.1

26.2

C29r C29rC29r

C29n.2n C29n.2n

C29n.1n

C29n.1n

C29n.2n C29n.2n

?

?

Figure 26. Cross sections through six paleomagnetic sections in southern San Juan Basin. (Section localities areshown on Figure 1; full data plots for all sections are on the figures indicated.) Only paleomagnetic sections throughall or part of the Ojo Alamo Sandstone are shown. Columns are broken by a gap of 25 m to show positions of top ofchron C33n at the HW, SM, and MP localities at a reasonable scale. Alignment of column TW based on field mea-surements of distance from lowermost C29n data point to base of Ojo Alamo Sandstone. Magnetochron boundariesare placed at mid-point between nearest-to-the-reversal data sites. 26.1 Published Paleocene magnetochron labelsof Lindsay et al. (1981) and Fassett and Steiner (1997) for all but the Mesa Portales (MP) column. 26.2 Revised mag-netochron labels of this report.


36

Top of magnetochron not determined

Base of magnetochron not determined

C29r

C32rC32r

C32r

0

5

-5

10

15

C29n20

25

30

meters

PALEOCENECAMPANIAN

?

?

?

?

?

?

C29n

C29r

C28r

HW

MP

C29n

9.0 1.3 1.8 27.5 72.5 k m


112 km

35

40

45

-65

-60

-55

-50

-45

-40

-35

-30

0

5

-5

10

15

20

25

30

meters

35

40

45

LEGEND

C33n



Column Pmag data plot(s) Photograph(s)






MP Figures 23, 24 Figures 22, 25

Locality name

Hunter Wash

South Mesa




Mesa Portales

C32r

C33n

C29r

C30n

C29n

C28rSM

BSA

BBA

C29n

C28n

C28r

C29n

Top - Ojo Alamo Ss

Top - Ojo Alamo Ss

C28r

BTW

C29n

C28n

C29n

-65

-60

-55

-50

-45

-40

-35

-30


C29r

C32r

C32r

0

5

-5

10

15

C29n20

25

30

meters

PALEOCENECAMPANIAN

C29n.2n

C29n.1r

C29n.1r

C29n.1r

C29n.1r

C29r C29r C29r

C32r C32r C32rC32r

HW

MP

C29n

9.0 1.3 1.8 27.5 72.5 k m


112 km

35

40

45

-65

-60

-55

-50

-45

-40

-35

-30

0

5

-5

10

15

20

25

30

meters

35

40

45

C33n

C32r

C33n

C32r

C33n

SM

BSA

BBA

Top - Ojo Alamo Ss

Top - Ojo Alamo SsBTW

C29n

-65

-60

-55

-50

-45

-40

-35

-30

C29r


26.1

26.2

C29r C29rC29r

C29n.2n C29n.2n

C29n.1n

C29n.1n

C29n.2n C29n.2n

?

?

Figure 27. Cross section through six paleomagnetic sections of Paleocene and uppermost Cretaceous (Campanian)strata in southwest San Juan Basin using base of magnetochron C29n as a datum. Boundaries for chrons C28r,C29n.1r, and C29n.2n are adjusted to make the thicknesses of these chrons as close to the same as possible ateach locality, while still honoring the magnetic-polarity-site data. The resulting average thickness of C29n.1r is about7 m.; for C29n.2n average thickness is about 11 m. Thickness of chron C28r and position of base of Ojo AlamoSandstone on column BSA are corrected from thickness and position shown in Lindsay et al. (1981, figure 7) basedon field studies in this area. Figures containing paleomagnetic data plots and photographs at these localities (exceptfor KW section) listed on Figure 26.


m long and contains 16 sample sites for a spacingof 5 m. Apparently, the intent of Butler and Lindsay(1985) at these two sections was to locate theboundary between the normal and reversed polar-ity intervals in Cretaceous Kirtland Formation strataunderlying the Ojo Alamo Sandstone. The wide

spacing of samples at these two localities pre-cluded the detection of the thinner normal andreversed polarity intervals seen in the Hunter Washand Mesa Portales paleomagnetic sections.

Figure 29 is a cross section across the south-western part of the San Juan Basin showing all of

C32r

C33n

C33n

100


0

50

100

Meters


0

50

100

150

Meters

C32r

C33n

Ojo AlamoSandstone

KirtlandFormation

Ojo AlamoSandstone

KirtlandFormation

MONCISCO MESA

EAGLE MESA

Figure 28. Paleomagnetic data plots at the Moncisco Mesa and Eagle Mesa localities (Butler and Lindsay 1985, fig-ures 10, 11). Polarity chron C32r was labeled B- and C30n; chron C33n was labeled A+ and C30n on figures 10 and11 of these authors. These polarity intervals are now known to be C32r and C33n (as labeled hereon). Note the signif-icantly different vertical scales for these two sections.

37


the paleomagnetic sections that extended deepenough into the Kirtland and Fruitland Formationsto include chrons C32r and C33n (see Figure 1 forlocations of these sections). The complete paleo-magnetic sections at the Moncisco Mesa, EagleMesa, and Mesa Portales localities are shown onFigure 29. The lower parts of the Hunter Wash andHunter Wash/Alamo Wash sections are not shownon this figure, but only contain more normal polarity(including the thin reversed-polarity interval dis-

cussed earlier) below the truncation points on theoriginal data plots (Figure 18). Figure 29 showsthat the C32r interval thins from the MM to the MPcolumn by 73 m, but that the thinning is not uni-form. For example, C32r thins by 48 m from col-umn MM to HW over a distance of 19 km (2.5 m/km), whereas the C32r interval only thins byanother 25 m over a distance of 112 km (0.22 m/km) from column HW to MP. Figure 30 is a recon-struction of Figure 29 using the top of polarity

C33n

C33n

PALEOMAGNETIC-DATA-PLOT FIGURE REFERENCES

Column Pmag data plot(s)

HW Figures 14, 15, 18

HW/AW Figure 8, 18

ES Figure 28

MP Figure 23

Locality name

Hunter Wash

MM Figure 28Monsisco Mesa

Hunter Wash/Alamo Wash

Eagle Mesa

Mesa Portales

C32r

C32r C32rC32r

60

50

40

30

20

10

10

20

30

0

70

80

90

100

110

130

120

140

150

60

50

40

30

20

10

10

20

30

0

70

80

90

100

110

130

120

140

150

131 km

C33n

C29r

15.519 9 87.5

MM EM

MP

C33n

C29r

HW

C33n

C29r

HW/AW

C29n

C29n.2n C29n.2n

DATUM - K-T interface

C32r

km

meters meters


?

?

LEGEND



C29n.1r

Top pmagsection

Top pmagsection

Figure 29. Cross section showing five magnetic-polarity columns containing chrons C33n and C32r in southern SanJuan Basin; datum K-T interface. Figure 1 shows column localities. Column HW/AW from Lindsay et al. (1981), col-umns MM and EM from Butler and Lindsay (1985), column HW from Fassett and Steiner (1997), column MP is pub-lished herein for first time.

38


chron C33n as a datum. This figure more accu-rately shows the southeastward truncation of thestrata underlying the Cretaceous-Tertiary interfacethat preceded deposition of the Ojo Alamo Sand-stone.

A detailed discussion of the thinning of UpperCretaceous rocks across the San Juan Basin (Fig-ure 1) is presented in the following section of thisreport. Radiometric ages and palynologic dataclearly indicate that the Maastrichtian and part ofthe uppermost Campanian are not presentthroughout most of the southern San Juan Basin

representing a hiatus of nearly 8 m.y. at the K-Tinterface. Much of the missing strata was probablyremoved by erosion, however, there may also havebeen a reduced rate of deposition of uppermostUpper Cretaceous rocks in parts of the basin in lat-est Cretaceous (Maastrichtian) time.

In their discussion of the Moncisco Mesa andEagle Mesa paleomagnetic sections (neither ofwhich included the Ojo Alamo Sandstone) Butlerand Lindsay (1985, p. 548) again state that theC29n normal chron (C29n.2n of Figure 27) is in theKirtland Formation. As discussed above, state-

C33n C33n

C32r

C32r C32r

C32r C32r

C33n

40

50

60

70

80

90

110

120

100

30

20

10

0

10

30

20

40

131 km

C33n

C29r

15.519 9 87.5

MM

EM

MP

C33n

C29r

HW

C33n

C29r

HW/AW

C29n

C29n.2n

C29n.1r

C29n.2n

DATUM - C33n-C32R polarity reversal

km

meters

40

50

60

70

80

90

110

120

100

30

20

10

0

10

30

20

40

meters


?

?

LEGEND



PALEOMAGNETIC-DATA-PLOT FIGURE REFERENCES

Column Pmag data plot(s)

HW Figures 14, 15, 18

HW/AW Figure 8, 18

ES Figure 28

MP Figure 23

Locality name

Hunter Wash

MM Figure 28Monsisco Mesa

Hunter Wash/Alamo Wash

Eagle Mesa

Mesa Portales

Top pmagsection

Top pmagsection

K-T interface

Figure 30. Cross section showing five magnetic-polarity columns containing chrons C33n and C32r in the southernSan Juan Basin; datum is C33n-C32r reversal. Figure 1 shows column localities. Column HW/AW from Lindsay et al.(1981), columns MM and EM from Butler and Lindsay (1985), column HW from Fassett and Steiner (1997), and col-umn MP is published herein for the first time. This figure is modification of Figure 29.

39


ments that chron C29n is in the Kirtland Formationdiffer from these author’s previous placement ofchron C29n within the Ojo Alamo Sandstone.Chron C29n was not found at Moncisco Mesa orEagle Mesa because the Ojo Alamo Sandstonewas clearly not sampled at those localities. Thisnormal chron—C29.2n of this report—is clearlypresent within the Ojo Alamo Sandstone at MesaPortales, only about 16 km east of Eagle Mesa.

Summary of San Juan Basin Paleomagnetism

Paleomagnetic studies of rock strata adjacentto the Cretaceous-Tertiary interface have beenconducted at eight localities in the southern part ofthe San Juan Basin (Figure 1). At three of theselocalities Hunter Wash, Hunter Wash/AlamoWash, and Mesa Portales the paleomagnetic sec-tions include the lower part of the Paleocene OjoAlamo Sandstone and as much as 150 m of under-lying Cretaceous strata that include magneto-chrons C32n and C33n (Figures 29, 30). Inaddition, chron C32r.1n may be present above thetop of chron C33n at the Hunter Wash and HunterWash/Alamo Wash localities. At two other localitiesMoncisco Mesa and Eagle Mesa where only Cre-taceous strata below the base of the Ojo Alamowere sampled, chrons C32r and C33n were identi-fied (Figure 29). Chron C32r.1n was not identifiedat those places, probably because of the widespacing of sample sites in those two sections.

At six localities (Figures 26, 27), a normal-polarity interval was found to be present in thelower part of the Ojo Alamo Sandstone. In the foursections where this normal interval was bracketedby reversed-polarity sites (Figures 26, 27), it isabout 11 m thick. Biochronologic evidence (dis-cussed below) unequivocally shows that the OjoAlamo Sandstone is Paleocene, thus the normal-polarity interval in the lower Ojo Alamo is the lower-most part of chron C29n (herein labeled C29n.2n).Butler and Lindsay (1985) recommended deletingthe normal-polarity interval in the lower part of theOjo Alamo (labeled chron C29n by Lindsay et al.1981, 1982) at three closely spaced localitiesSouth Mesa, Barnum Brown Amphitheater, andBarrel Spring Arroyo. These authors stated thattheir original studies were in error because thesenormal intervals did not represent true Paleoceneremanent magnetism but were present-day-normaloverprints. However, because this normal-polarityinterval is also present in the Ojo Alamo Sandstoneat three other widely spaced localities, it is notcredible that these normal-polarity intervals in thelower Ojo Alamo at these six localities could all

have been the result of present-day, normal-field,overprinting. The presence of chron C29n in thelower part of the Ojo Alamo Sandstone thus pro-vides independent evidence that this formation,including its dinosaur-bearing parts at severallocalities, is Paleocene in age.

The Paleocene magnetochrons identified inthe southern San Juan Basin have been reevalu-ated and relabeled as shown on Figures 26 and27. Magnetochron C29n is about 70 m thick andcontains a persistent, 7 m thick reversed-polarityinterval in its lower part, thus, C29n in the SanJuan Basin consists of three subchrons: C29n.1n,C29n.1r, and C29n.2n (Figure 27).

Revised Magnetic-Polarity Calibration

Figure 31 portrays a recalibration of paleo-magnetic-reversal ages between the top of chronC33n and the base of chron C29r based on inter-polation between two tie points: the precisely datedpolarity reversal between chrons C33n and C32r(73.50 ± 0.19 Ma, Fassett and Steiner 1997 andFassett 2000), and the age of the Cretaceous-Ter-tiary boundary (65.51 ± 0.01, Hicks et al. 2002).The age of the C33n-C32r reversal was calculatedon the basis of eight 40Ar/39Ar ages determined byJ.D. Obradovich (USGS, retired) using the TaylorCreek Rhyolite as a standard with an assigned ageof 28.32 Ma. Figure 32 (from Fassett 2000, figure13) is a northeast-trending stratigraphic cross sec-tion across the San Juan Basin showing the posi-tions of the eight dated ash beds from the UpperCretaceous Lewis Shale, Fruitland, and KirtlandFormations. The stratigraphic positions of WesternInterior ammonite zones and the Hunter Wash andChimney Rock magnetic-polarity columns are alsoshown.

The age of the K-T boundary was determinedby Hicks et al. (2002, p. 43) by normalizing “allavailable 40Ar/39Ar isotopic dates as published forthe K-T boundary interval . . . based on the monitorage of 28.02 Ma for Fish Canyon Tuff and 28.32Ma for Taylor Creek Rhyolite, which yields an aver-age age of 65.51 ± 0.01 for the K-T boundary.” Thetwo tie points used to construct the calibrated mag-netic-polarity column (Figure 31) are thus based onthe same standards.

The global geologic time scale of Gradstein etal. (2004) shows the correct age of 65.50 Ma forthe K-T boundary but an incorrect age of 73.0 Mafor the C33n-C32r reversal—the correct age of thisreversal is 73.50 Ma. The use of an incorrect agefor the C33n-C32r reversal resulted in incorrectage assignments in Gradstein et al. (2004) for the

40


41

C32r.1n

C32n.2n

C32n.1nC32n.1r

C31r

C31n

C30r

C30n

C29r

C29n

C28r

C28n

73.5073.2773.19

72.93

71.62

1.31

5.46

0.260.080.23

0.57

71.39

71.14

0.23

0.25

1.79

68.99

2.33

68.0767.95

66.07

65.12

64.43

64.13

63.00

1.13

0.35

0.69

0.95

1.88

0.12

0.92

65.51PALEOCENE

CRETACEOUS0.56

0.39

C33n

Ash J - 73.04 ± 0.25

Ash H - 73.37 ± 0.18 C32r.2r

This interval is not present in the southern San Juan Basin

C32r.1r

Figure 31. Paleomagnetic-polarity column showing ages of polarity reversals and durations of polarity chrons for lat-est Cretaceous strata based on data from San Juan Basin, New Mexico. Polarity-chron durations and reversal agesfor Cretaceous magnetochrons were determined by proportionalizing chron durations of Cande and Kent (1992,1995) between ages of 65.51 Ma for the Cretaceous-Tertiary (K-T) boundary (Hicks et al. 2002) and 73.50 Ma for theC33n-C32r reversal (Fassett and Steiner 1997; Fassett 2000). Polarity-chron ages above K-T boundary are fromGradstein et al. (2004). Ages of ash beds J and H in polarity chron C32r from Fassett and Steiner (1997).


reversal ages between this reversal and the K-Tboundary. Ages for the paleomagnetic reversalsshown on Figure 31 are calibrated based on moreprecisely dated tie points and thus are consideredto be the most accurate currently available for thistime interval. It is recommended that the reversalages for the Upper Cretaceous of Figure 31replace those of Gradstein et al. (2004).

The ages of uppermost Upper CretaceousWestern Interior ammonite zones of Gradstein etal. (2004, table 19.3) are also not in agreementwith the ages of these faunal zones in the SanJuan Basin. Figure 32 shows the positions of theWestern Interior ammonite zones from Baculitesscotti to Baculites compressus relative to a strati-

graphic cross section encompassing the LewisShale, Pictured Cliffs Sandstone, and the Fruitlandand Kirtland Formations. These ammonite-zoneplacements are from Fassett (1987), based on thework of Cobban (1973) and Cobban et al. (1974).Time lines opposite ash-bed ages and ammonite-zone boundaries determined at outcrops in the SanJuan Basin are projected into the subsurface of thebasin. The highest ammonite-zone boundaryshown on Figure 32 is between the Didymocerascheyennense and B. compressus zones. Thisboundary was located on the outcrop in the vicinityof Chimney Rock (Figure 32) by W.A. Cobban asdiscussed in Fassett and Steiner (1997, p. 245). Asseen on Figure 32, the base of B. compressus is

(base ?)

Baculitesscotti

Didymocerasnebrascense

Didymocerasstevensoni

Didymocerascheyennense

Baculitescompressus

Ammonite Zones

Chimney Rockmagnetic-polarity column

C32r.1r

AA

AA

74.25 Ma (ash CR)

C32r.1n

C32r.2r

C33n

OU

TCR

OP

OU

TCR

OP

Hunter Washmagnetic-polarity column

C29n.1r

C29rC29n.2n

C32r

C33n

C32rC33n

74.56 Ma (ash 2)

75.56 Ma(ash DEP)

1 2 3 4 5 6 7 8 9 10 11

145 km

Northeast

(top ?)

Exiteloceras jenneyi

73.37 Ma (ash H)

0

73.50 Ma

0 50 km

Durango

Farmington

Cuba

109 108 107

37

36

COLORADO

NEW MEXICO

UTA

HA

RIZ

ON

A

PagosaSprings

Kf

Kf

Hunter Washstudy area

(interpolated)

8 m.y.

LP

HBB

Datum - Huerfanito Bentonite Bed

Lewis Shale

Kirtland and

Fruitland Formations

Sandstone

CRETACEOUSTERTIARY

Ojo

Alamo

Sandstone

Southwest

Kf

ChimneyRock site

74.55 Ma (ash 4)

Animas Formation

HW CR

74.30 Ma (ash LP)

75.76 Ma(ash HBB)

34

56

78 9

1011

1

2

25

S A N6

J U A N B A S I N

Meters600

500

400

300

200

100

73.04 Ma (ash J)

Figure 32. Stratigraphic cross section from Hunter Wash to Chimney Rock (modified from Fassett 2000). Contacts ofgeologic formations are from geophysical logs at localities shown (log-data are provided in Fassett and Steiner1997). Ash-bed sample localities are shown on index map. Ash-bed ages are shown; those in red are projected intothe Hunter Wash section. Letters A at right side of section show levels of ammonite collection sites. Lower ammo-nite-zone boundaries modified from Fassett (1985) and Fassett et al. (1997). On magnetic-polarity columns, black isnormal polarity, white is reversed polarity. Vertical exaggeration = 200 X. Age of C33n-C32r magnetic-polarity rever-sal of 73.50 Ma is mean of 12 interpolated reversal ages based on dated ash beds bracketing reversal as discussedin Fassett and Steiner (1997) and in Fassett (2000).

42


bracketed by the top of polarity chron C33n, withan age of 73.50 Ma and altered volcanic ash bedCR (in the underlying D. cheyennense zone) withan age of 74.25 Ma; these bracketing ages arefrom the same, continuous, stratigraphic section ata single locality. The base of B. compressus fallsabout halfway between these levels, thus the ageof the base of B. compressus is estimated to be73.90 Ma. The B. scotti-D. nebrascense ammonite-zone boundary was also located very precisely onthe outcrop by Cobban, as reported in Fassett etal. (1997) north of Cuba, New Mexico at the HBB(Huerfanito Bentonite Bed) locality shown on theinset map on Figure 32. This ammonite-zoneboundary is virtually at the same level as the Huer-fanito Bentonite Bed of the Lewis Shale (Figure32). The age of the Huerfanito Bed of 75.76 Mawas determined on the basis of samples collectedat the same outcrop locality where the B. scotti-D.nebrascense boundary was located, thus theammonite-zone boundary has been directly datedthere. The duration of the interval from the base ofthe D. nebrascense zone to the base of the B.compressus zone is 1.86 m.y.

Gradstein et al. (2004, table 19.3) show theage of the base of B. compressus as 73.50 Ma andthe base of D. nebrascense as 76.38 Ma for aduration of 2.88 m.y., or about 1 m.y. longer thanthe San Juan Basin interval. The base of the B.compressus zone of Gradstein et al. is 0.4 m.y.younger than the base of this zone in the San JuanBasin and the base of the D. nebrascense zoneaccording to those authors is 0.62 m.y. older thanin the San Juan Basin. Because the San JuanBasin ammonite-zone ages were determined at the

same outcrops where the ammonite-zone bound-aries were located (Figure 32), it is suggested thatthe San Juan Basin ages for these ammonite-zoneboundaries are more precise.

The ages of the intervening ammonite-zoneboundaries between the base of D. nebrascenseand the base of B. compressus were calibrated byinterpolation between the ages of ash bed CR andHBB in the Chimney Rock section (Figure 32).Table 1 shows the ages and durations of the West-ern Interior ammonite zones determined in thisreport compared to the ages and durations of thesesame ammonite zones published in Gradstein etal. (2004). The more precise ages here reported forthese boundaries supersede those of Gradstein etal. (2004). The base of the B. scotti zone in theLewis Shale has not yet been located in the SanJuan Basin.

Lucas et al. (2006, p. 5) discussed the identifi-cation by Lucas and Sealey (1992) of “ammonitesof the D. cheyennense zone in the upper LewisShale near Cuba [NM].” This fossil locality is southof Mesa Portales (Figure 21) and is below the levelof the Huerfanito Bentonite Bed there. Figure 32shows that the Huerfanito Bed is 75.76 Ma, asdetermined by Fassett et al. (1997) who found thatthe Huerfanito Bed is almost exactly at the base ofthe D. nebrascense ammonite zone. Table 1 showsthat the base of the D. nebrascense zone is about2 m.y. older than the D. cheyennense zone in theSan Juan Basin. As discussed above, the ammo-nite-zone boundaries shown on Table 1 have allbeen precisely dated on the outcrop in the SanJuan Basin. It is therefore not physically possiblefor the ammonite collections of Lucas and Sealey

TABLE 1. Ages of some late Cretaceous western interior ammonite-zone boundaries of Gradstein et al.(2004) and this report.

Gradstein et al. (2004) This report

W. Interior Ammonite Zone Age (Ma) Duration (m.y.) Age (Ma) Duration (m.y.)

Bacutes compressus 73.50 0.72 73.90 ?

Didymoceras cheyennense 74.28 0.78 74.50 0.60

Exiteloceras jenneyi 75.05 0.77 74.65 0.15

Didymoceras stevensoni 75.74 0.69 74.98 0.33

Didymoceras nebrascense 76.38 0.64 75.76 0.78

Note: Ages are for base of ammonite zones.

43


44

1

3

4

5

6

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ion

Far

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mag

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r top

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ictu

red

Clif

fs S

ands

tone

) are

sho

wn.

Pal

eom

agne

tic d

ata

in d

rill h

oles

1, 2

, 4, a

nd 6

pro

ject

ed fr

om n

earb

y ou

tcro

p lo

calit

ies

(Fig

ure

3); p

aleo

-m

agne

tic d

ata

plot

s on

Fig

ures

8, 1

2, 1

4, 1

8, 2

3, a

nd 2

8. P

alyn

olog

ic s

ampl

e-co

llect

ion

leve

ls in

dril

l hol

es 1

, 2, 5

, and

6 a

re p

roje

cted

from

nea

rby

outc

rop

loca

litie

s;pa

lyno

mor

phs

iden

tifie

d fro

m s

ampl

es li

sted

on

the

Appe

ndix

tabl

es, a

s sh

own.

Top

of F

ruitl

and

Form

atio

n is

def

ined

by

high

est c

oal b

ed o

r car

bona

ceou

s sh

ale

bed

in s

ectio

n (F

asse

tt an

d H

inds

197

1); c

onta

ct is

sho

wn

as d

ashe

d lin

e be

caus

e of

diff

icul

ty lo

catin

g it

with

cer

tain

ty o

n ge

ophy

sica

l log

s. R

adio

met

ric a

ges

of s

anid

ine

crys

tals

from

alte

red

volc

anic

ash

bed

s in

Ojo

Ala

mo

type

are

a fro

m F

asse

tt an

d St

eine

r (19

97) a

nd F

asse

tt (2

000)

; stra

tigra

phic

leve

ls o

f dat

ed a

sh b

eds

are

pro-

ject

ed in

to lo

g of

dril

l-hol

e 2

from

mea

sure

d ou

tcro

p lo

calit

ies

at o

r ne

ar H

unte

r W

ash

(Fig

ure

3).

Stra

tigra

phic

lev

els

of P

uerc

an m

amm

al s

ites

in lo

wer

mos

tN

acim

ient

o Fo

rmat

ion

show

n in

dril

l-hol

e lo

gs 2

and

4 fr

om n

earb

y ou

tcro

p lo

calit

ies

from

Will

iam

son

(199

6) a

nd L

inds

ay e

t al.

(198

1). V

ertic

al e

xagg

erat

ion

= 13

0 x.

Dis

tanc

es b

etw

een

drill

-hol

e lo

calit

ies

not s

cale

d ho

rizon

tally

.


45

13

45

62

Low

er sh

ale

mem

ber

of K

irtla

nd F

orm

atio

n

Fru

itlan

dFo

rmat

ion

Pict

ured

Clif

fs

Sand

ston

e

Lew

is S

hale

Hue

rfan

ito B

ento

nite

Bed

DAT

UM

75.7

6 M

a

5 6 8 9 10 11 12C32

r

C33

n

.1r

C29

r

C29

n

C29

r

7 14 15 16 17 18 1913

Base

of P

mag

Sect

ion

Base

of P

mag

Sect

ion

Base

of P

mag

Sect

ion

MO

NC

ISC

O M

ESA

OJO

ALA

MO

TYPE

ARE

AB

ETTO

NIE

TSO

SIE

W

ASH

MES

A P

OR

TALE

S

C29

n .1

r

C29

n .1

n

POT

MES

A

NW

SE

21 k

m.

20 k

m.

20 k

m.

28 k

m.

35 k

m.

Ash

274

.56

Ma

Ash

474

.55

Ma

A

A

B

A

To

p of

Pm

agSe

ctio

n

Nac

imie

nto

Form

atio

n

G

FGO

jo A

lam

o Sa

ndst

one

A

C33

n

Ash

H73

.37

Ma

A

sh J

73.0

4 M

a

Kirt

land

Form

atio

n

Fru

itlan

dFo

rmat

ion

Ojo

Ala

mo

Sand

ston

eF

E

HI

AT

US

HI

AT

US

(Not

to s

cale

ver

tical

ly)

Puer

can

mam

mal

sPu

erca

nm

amm

als

65.2

Ma

C29

n .1

n

C B

SILV

ER M

EDA

L 1

C32

rC

32r

Top

of P

mag

Sect

ion F

arm

ingt

on S

ands

tone

and

uppe

r sha

le m

embe

r o

f Kirt

land

For

mat

ion

CD

C33

n

C33

n

1.3

m.y

.

C B

E D

Whi

te S

s

C29

n .2

nC

29n

.2n

C33

n

C33

n

C33

n

Din

osau

rbo

nes

Din

osau

rbo

nes

Figu

re 3

4. T

ime-

stra

tigra

phic

cro

ss s

ectio

n al

ong

sout

hwes

t mar

gin

of th

e S

an J

uan

Bas

in (

line

of s

ectio

n on

Fig

ure

3). C

ross

sec

tion

mod

ified

from

Fig

ure

33 to

show

pre

senc

e of

hia

tus

in F

ruitl

and-

Kirtl

and

sect

ion

betw

een

Mes

a Po

rtale

s ar

ea a

nd O

jo A

lam

o ty

pe a

rea;

pre

-Ojo

Ala

mo

San

dsto

ne h

iatu

s al

so s

how

n. (S

ee F

ig-

ure

33 fo

r dril

l-hol

e id

entif

icat

ions

and

pal

ynol

ogic

-sam

ple

data

.) A

bout

215

m o

f sec

tion

mis

sing

from

the

Frui

tland

-Kirt

land

sec

tion

in M

esa

Por

tale

s ar

ea re

pres

ents

abou

t 1.3

m.y

. Pre

-Ojo

Ala

mo

Sand

ston

e hi

atus

repr

esen

ts n

early

8 m

.y. i

n O

jo A

lam

o Sa

ndst

one

type

are

a. V

ertic

al e

xagg

erat

ion

= 13

0 x.


46

1 3 4 5 62

5

6

8

9

10

11

12

c33N

29n

7

14

15

16

17

18

19

13

MONCISCO MESAOJO ALAMOTYPE AREA

BETTONIE TSOSIE WASH MESA PORTALESPOT MESA

NW SE

Nacimiento FormationOjo Alamo Sandstone

Puercan mammal Puercan mammal29n.1n

29n.1n

Farmington Ssand u. sh. mbr. of Kirtland Fm.

Lower sh. mbr.of Kirtland Fm

Fruitland Fm.Fruitland Fm.

Pictured Cliffs Ss

Lewis Sh.

Kirtland Fm.

Huerfanito Bentonite BedDATUM

7.8 m.y.

1.3 m.y.

32

H I A T U S

H I A T U S

MAASTRICHTIAN

CAMPANIAN

PALEOCENE

75.8 Ma

74.6 Ma.

74.6 Ma

73.4 Ma.73.0 Ma

70.6 Ma

35 KM28 KM20 KM20 KM21 KM

32

32

33

33

3333

SILVER MEDAL 1

33

DinosaurDinosaur

CRETACEOUS

.2n .2n.1r

65.2 Ma

65.5 Ma

Figure 35. Time-stratigraphic cross section along southwest margin of San Juan Basin (line of section on Figure 3).Modified from Figure 34 to show magnitude of Fruitland-Kirtland and pre-Ojo Alamo Sandstone hiatuses at samescale. (See Figure 33 for drill-hole identifications.) Vertical exaggeration = 85 x.


(1992, and discussed in Lucas et al. 2006) foundsouth of Mesa Portales to be in the D. cheyenn-ense zone. Moreover, USGS paleontologist W.A.Cobban visited this locality in 1997 accompaniedby the author, Lucas, and Sealey and concludedthat the fossil assemblage there was in the B. scottiWestern Interior ammonite zone. Thus, it can onlybe concluded that the ammonite fossils found byLucas and Sealey (1992) at this locality were incor-rectly identified.

NW TO SE THINNING OF CRETACEOUS STRATA IN SW SAN JUAN BASIN

Figure 1 shows that the Fruitland Formation-Kirtland Formation interval thins by 2,100 feet (640m) from the northwestern to the southeastern partof the San Juan Basin. This interval also thins dra-matically in the southern part of the basin fromMoncisco Mesa to Mesa Portales. The isopachmap (Figure 1.1) of the interval between the Huer-fanito Bentonite Bed and the base of the OjoAlamo Sandstone shows thinning of this interval ofabout 1,000 feet (300 m) between these two locali-ties. To better understand and illustrate the natureof this thinning, northwest-trending stratigraphicand time-stratigraphic cross sections (Figures 33-35) were constructed across the southern part ofthe basin to illustrate the stratigraphy of the intervalfrom the uppermost part of the Upper CretaceousLewis Shale to the lowermost part of the lower-Paleocene Nacimiento Formation; the line of thesecross sections is shown on Figure 3. (Note: Thefollowing discussion of these cross sections usesfeet, followed by the parenthetical thicknesses inmeters, because the depth track for the geophysi-cal logs referred to are calibrated in feet.)

The stratigraphic, geophysical-log cross sec-tion (Figure 33) was constructed using drill-holelogs at localities numbered 1 through 6 on Figure3. Contacts of most of the geologic formationsincluded in the interval studied are easily locatedon these logs, with the possible exception of thetop of the Fruitland Formation whose contact hasbeen defined as being at the top of the highest coalor carbonaceous shale bed in the formation (Fas-sett and Hinds 1971). This contact cannot be con-tinuously mapped, either on the surface or ongeophysical logs, because of the discontinuousnature of thin, uppermost-Fruitland coal or carbo-naceous mudstone beds. Because the lithologiesof the Fruitland and lower shale member of theKirtland are virtually identical, the presence ofthese carbon-rich beds provides the only criterionto separate these formations. The next-highest

geologic contact between the lower shale memberof the Kirtland Formation and the overlying Farm-ington Sandstone Member is quite distinctivebecause the Farmington Sandstone consists of aseries of closely spaced and discontinuous chan-nel-sandstone beds (Figure 33) that are clearly vis-ible on geophysical logs and on the outcrop. Thelowermost sandstone bed of the Farmington Sand-stone Member is not always at the same strati-graphic level at different localities. This contactshifts up and down from location to location, usu-ally within a vertical range along depositional strikeof at most tens of meters (Fassett and Hinds1971). The contact between the Kirtland Formationand the Ojo Alamo Sandstone (Figure 33) is clear-cut and easily located on geophysical logs (and onthe outcrop) because the Ojo Alamo contains fromone to several massive, coarse-grained, conglom-eratic sandstone benches with distinctive geophys-ical-log characteristics.

The locations of five of the six geophysicallogs on the stratigraphic cross section (Figure 33)were selected close to important outcrop localitiesin the southwestern San Juan Basin where paleo-magnetic, palynologic, and fossil-vertebrate datawere obtained. The log of drill-hole 3 was insertedin the section to maintain even spacing of subsur-face control along the line of section. The datum forthis cross section is the Huerfanito Bentonite Bedof the Lewis Shale. Because the Huerfanito Bed isan altered volcanic ash bed that represents an ashfall into the Lewis-Shale sea in Late Cretaceous(Campanian) time, this marker bed represents atime horizon throughout the San Juan Basin. TheHuerfanito Bed is an easily recognizable markerbed on geophysical logs in the subsurface through-out most of the San Juan Basin.

Radiometric ages of sanidine crystals from thealtered volcanic ash beds shown on Figures 32and 33 were acquired using 40Ar/39Ar methodology(Fassett and Steiner 1997, Fassett et al. 1997,Fassett 2000). Four of these ages are projectedinto the log of drill-hole 2 of Figure 33 from theiroutcrop locations in or near Hunter Wash, about 9km to the southwest. Magnetochrons identifiednear drill holes 1, 2, 4, and 6 (discussed in detailabove) have also been projected into the geophys-ical logs. The magnetic-polarity column of drill-hole2 is a composite of the two (virtually identical) col-umns of Lindsay et al. (1981) and Fassett andSteiner (1997) of Figure 18. The magnetic-polaritycolumn at drill-hole 6 is from Mesa Portales (Figure23). The nearby Eagle Mesa magnetic-polarity col-umn of Butler and Lindsay (1985) depicted on Fig-

47


ures 28 and 29 places the C33n-C32r reversal atvirtually the same level as at Mesa Portales. Thelevels of palynologic samples collected fromnearby outcrop localities are shown on drill-holelogs 1, 2, 5, and 6; the palynology of these strata issummarized in the “Palynology” section of thisreport and is discussed in greater detail in theAppendix. Dinosaur- and mammal-bone localitiesshown in the Ojo Alamo Sandstone at drill holes 2and 4 are at nearby outcrops and are discussed inthe “Vertebrate Paleontology” section of this report.

The lowest unit shown on the stratigraphiccross section of Figure 33, the Lewis Shale, wasdeposited as marine muds and silts on the westernedge of the Western Interior Seaway in late Cam-panian time. Overlying the Lewis Shale is the Pic-tured Cliffs Sandstone, a time-transgressive,shoreface-marine sandstone, deposited during thefinal regression of the Western Interior Seawayfrom southwest to northeast across the San JuanBasin area. The fact that the top of the PicturedCliffs is essentially parallel to the Huerfanito Ben-tonite Bed on the logs of drill holes 1 through 5(Figure 33) indicates that the line of cross sectionis directly along the depositional strike or paleo-shoreline of the Pictured Cliffs sea. Between holes5 and 6, the Pictured Cliffs is seen to rise strati-graphically; this is because the trend of the line ofsection between these two holes is eastward,diverging from the Pictured Cliffs shoreline’s south-east trend, and is thus reflecting the northeastwardstratigraphic rise of the Pictured Cliffs Sandstone.The 400 m stratigraphic rise of the Pictured Cliffsacross the entire San Juan Basin is illustrated onFigure 32.

The thickness of the Fruitland Formationranges from about 300 feet (90 m) in drill hole 3 to400 feet (120 m) in drill hole 1 on this cross sec-tion. The Fruitland-Kirtland contact is virtually par-allel to the top of the Pictured Cliffs in drill holes 1through 5 (Figure 33). Coal beds, representingback-shore swamp deposits in the lower FruitlandFormation, are present in all six drill holes. Thecontact of the lower shale member of the KirtlandFormation and the Farmington Sandstone Memberof the Kirtland is about 600 feet (180 m) above thetop of the Pictured Cliffs in holes 1 through 3, how-ever in holes 4 through 6, the Farmington Sand-stone is absent and large channel sandstonesappear in the upper part of the section. Above theFarmington Sandstone and upper shale member ofthe Kirtland Formation, undivided, the Ojo AlamoSandstone is seen to be stepping down from drillhole 1 to drill hole 6; the base of the Ojo Alamo is

950 feet (290 m) lower in drill hole 6 than in drillhole 1. All of this thinning is apparently at theexpense of the underlying Kirtland Formation,which appears to be totally cut out in drill hole 6.

There is a problem with the simple interpreta-tion of the geophysical-log section depicted on Fig-ure 33, apparently showing progressive truncationof the Fruitland-Kirtland interval from northwest tosoutheast. Note that the polarity reversal fromC33n to C32r (within the Fruitland-Kirtland interval)is also stepping down from drill hole 1 to drill hole2, and from drill hole 2 to drill hole 6 (Figure 33).Paleomagnetic reversals are isochrons, therefore,if deposition of the Fruitland-Kirtland interval stratahad been continuous and even across the area ofthe Figure 33 cross section, the C33n-C32r rever-sal would be parallel with the underlying HuerfanitoBentonite Bed isochron. If the progressive trunca-tion of Kirtland strata from northwest to southeastwere as simple as apparently shown on Figure 32,resulting only from a pre-Ojo-Alamo-Sandstoneerosion cycle, that truncation would have totally cutout magnetochron C32r and several hundred feet(about 200 m) of the upper part of chron C33n indrill hole 6, which is clearly not the case. Why thenis the C33n-C32r reversal present in the Mesa Por-tales area? There is an elegant, straightforwardsolution to this problem.

Figure 34 is a time-stratigraphic cross sectionon which the stratigraphic section of Figure 33 hasbeen reordered so that the two isochrones, theC33n-C32r reversal and the Huerfanito BentoniteBed, are parallel. Raising the top of C33n to thesame level in drill holes 2 through 6 as in drill hole1 reveals the presence of a wedge-shaped hiatuspresent in the Fruitland-Kirtland interval on Figure34 (it is assumed there is no hiatus in this intervalin drill hole 1, although this is not known for cer-tain). The top of polarity chron C33n was raised 75feet (23 m) in drill hole 2 to bring it to the samelevel as in drill hole 1. In drill hole 6, however, thetop of chron C33n had to be raised 600 feet (185m) to bring it up to the level of the top of this chronin drill-hole 1. Because the rate of deposition of therock strata between the Huerfanito Bentonite Bedand Ash J averages 142 m/m.y. (384 m/2.72 m.y.)the duration of the hiatus at drill-hole 2 must beabout 160,000 years whereas at drill hole 6 it isabout 1.3 m.y.

The stratigraphic level of the unconformitywithin the Fruitland-Kirtland interval is not knownwith certainty, because it has never been discov-ered on the outcrop and it cannot be detected ongeophysical logs. In drill hole 6 (Figure 34), the

48


unconformity has to be below the top of chronC33n and above the coal bed in the lower part ofthe Fruitland. Because the top of C33n is within theprominent white sandstone bed at Mesa Portales(Figures 22, 23), a reasonable placement is at thebase of the white sandstone (Figures 33-35). Indrill holes 4 and 5, the unconformity would logicallybe at the base of the conspicuous channel-sand-stone beds that are present in the uppermost partof the Kirtland Formation. In drill hole 3, wherethere is no obvious lithologic level at which to placethe unconformity, it is projected horizontally west-ward from hole 4, within the Farmington SandstoneMember of the Kirtland Formation (Figure 34). Andin drill hole 2, the unconformity is placed below thetop of chron C33n, also within the FarmingtonSandstone.

Figure 35 is a time-stratigraphic cross sectionalong the same line of section as Figures 33 and34, but with the vertical exaggeration changed from130 X to 85 X to make possible the portrayal of the7.8-m.y. hiatus separating Campanian Kirtland For-mation strata from the overlying Paleocene OjoAlamo Sandstone strata. The age of the base ofthe Ojo Alamo Sandstone is estimated to be 65.2Ma based on an age of 65.112 Ma (Gradstein et al.2004) for the base of magnetochron C29n locatedjust above the base of the Ojo Alamo. Palynologicdata also confirm that earliest Paleocene strata areabsent in the San Juan Basin (Newman 1987, p.158). In addition, the K-T boundary asteroid-impactfall-out layer or the iridium-enriched layer found atthe K-T boundary at many localities in the WesternInterior of North America, have not been found ator near the K-T interface in the San Juan Basindespite concerted attempts to locate them at sev-eral localities in the southern San Juan Basin (Orthet al. 1982). It is thus estimated that about 0.3 m.y.of earliest Paleocene time is not represented byrock strata in the southern San Juan Basin (Figure35). Palynologic data (discussed below) supportthe absence of lowermost Paleocene strata belowthe base of the Ojo Alamo Sandstone.

PALEOBOTANY

Leaf Fossils

Knowlton (1917, 1924) discussed leaf fossilshe identified from the Fruitland and Kirtland Forma-tions in the San Juan Basin and also discussed thesignificance of leaf fossils he identified from the OjoAlamo Sandstone at several localities. Knowltonstated that Ojo Alamo Sandstone fossils were com-pletely different from those found in underlying

beds and even though these fossil leaves did notdefinitively fix the age of the Ojo Alamo as Tertiary,Knowlton found them to be more Tertiary-like thanCretaceous. As far as is known, Knowlton’s work isthe only published report on leaf fossils from theOjo Alamo Sandstone. Reeside (1924) addressedthe age of the Ojo Alamo Sandstone and cited thepaleobotanical studies of Knowlton (1917, 1924) astentatively supporting the Paleocene age of thisformation.

Palynology

The palynology of the rocks adjacent to theCretaceous-Tertiary boundary in the San JuanBasin is discussed in detail in the Appendix of thisreport. All palynomorphs identified from theserocks are listed in the Appendix tables and thepaleochronologic significance of these fossils isdiscussed therein in detail. The following section ofthis report summarizes the palynologic data pre-sented in the Appendix.

Palynology has been a valuable and precisebiochronologic tool for defining the Cretaceous-Tertiary boundary in continental strata of the West-ern Interior of North America. For nearly 50 years,index palynomorphs such as Proteacidites spp.and many species of Aquillapollenites, for exam-ple, have been the primary Cretaceous index fos-sils in the Western Interior with the last occurrenceof these key taxa unequivocally marking the end ofthe Cretaceous Period (Anderson 1960, Tschudy1973, Nichols and Johnson 2002, among others).(Proteacidites was renamed Tschudypollis in Nich-ols 2002.) The K-T boundary was located withincentimeters in the Raton Basin of New Mexico andColorado by R.H. Tschudy (USGS) on the basis ofthe last occurrence of Tschudypollis spp. That workenabled Orth et al. (1981) to find the iridium-enriched, end-Cretaceous, asteroid-impact, fall-outlayer within that same centimeters-thick interval.Because the fall-out layer is only about 25 mmthick and not conspicuous in most exposures, theuse of palynology to narrow the stratigraphic inter-val of interest has been critical in locating this bedat numerous sites in the Western Interior. The iden-tification of the end-Cretaceous fall-out layer in theRaton Basin (Orth et al. 1981, 1982) was the firstdiscovery of this important geochron in continentalrocks anywhere in the world. Subsequently, thefall-out layer has been found at numerous otherlocalities in continental strata in the Western Inte-rior using palynology to zero in on the appropriaterock strata. The discovery of the asteroid-impactfall-out layer has not only established for the first

49


time the presence of a physical rock layer markingthe Cretaceous-Tertiary boundary, but equallyimportantly, has also validated the precise age sig-nificance of Late Cretaceous and Paleocene indexpalynomorphs found below or above it in the West-ern Interior of North America.

The use of fossil pollen to fine tune ageswithin Upper Cretaceous or lower Paleocenestrata, however, has proved to be useful, but lessprecise. As the discussion in the Appendix indi-cates, palynologic data in the San Juan Basin sug-gests that the Maastrichtian Stage is missingthroughout most of the basin, however, this Stagelasted 5 m.y. (Gradstein et al. 2004); thus, this find-ing did not have the precision of the end-Creta-ceous-boundary determination. (In actuality, asFigure 35 shows, the Cretaceous-Tertiary hiatus inthe southern San Juan Basin spans 7.8 m.y.; atime period that includes about 2.5 m.y. of lateCampanian time, all of Maastrichtian time, andabout 0.3 m.y. of earliest Paleocene time.) The firstappearance of Paleocene index palynomorphs,such as Momipites tenuipolus and Brevicolporitescolpella, in the southern part of the Western Interior(Anderson 1960, Tschudy 1973, Nichols and John-son 2002, Nichols 2003) has also been useful indetermining the ages of strata adjacent to the K-Tinterface in the San Juan Basin. Palynologistsagree (Nichols, personal commun., 2005) that rocksamples that yield diverse palynomorph assem-blages, contain no specimens of Cretaceous indexfossils (such as Tschudypollis spp.), and containPaleocene index palynomorphs (such as B.colpella or M. tenuipolus), are “unquestionably”Paleocene in age.

The palynology of rock strata in the San JuanBasin adjacent to the K-T interface has beenaddressed in a number of publications beginningwith Anderson (1960). In addition, a large amountof palynologic data exists for these same strata inthe form of unpublished USGS “Reports onReferred Fossils” in the files of the author. Theappendix of this report contains a detailed discus-sion and synthesis of all of these palynologic data.

Palynology has fixed the Cretaceous-Tertiary(K-T) interface at (or just below) the base of the OjoAlamo Sandstone at five principal localities in theNew Mexico part of the San Juan Basin: 1) theCuba, New Mexico area; 2) the Gasbuggy core; 3)the Mesa Portales area; 4) the Ojo Alamo Sand-stone type area; and 5) the San Juan River site(see Figure 1 for locations). At one locality in theColorado part of the basin, near Durango (Figure1), palynology has bracketed the K-T interface at

the contact between the Cretaceous Kirtland For-mation and the Paleocene Animas Formation.Cuba, New Mexico Area. Anderson (1960) wasthe first geologist to use palynology to determinethe location of the Cretaceous-Tertiary boundary inthe San Juan Basin. He collected rock samplesfrom the uppermost Kirtland Formation and fromwithin the Ojo Alamo Sandstone in the southeastpart of the basin near Cuba, N.M. (Figure 1) andconcluded that the palynomorph assemblagesfrom the Ojo Alamo Sandstone were all Tertiary inage and the assemblages from the underlying Kirt-land Formation were Cretaceous in age. Based onthese data, Anderson (1960) placed the K-Tboundary at the base of the Ojo Alamo Sandstone.Anderson was aware that the Ojo Alamo containedabundant dinosaur bone in other parts of the basinand concluded that (p. 13) either those dinosaurfossils had been reworked or misidentified or that:“Alternatively, pre-Lance-type dinosaurs persistedinto a Tertiary environment.”Gasbuggy Core. Core chips from 52 levels werecollected from the Gasbuggy core (Figure 1) in1967 by the author from a drill hole in the east-cen-tral part of the San Juan Basin (Fassett 1968a, b).These samples were from the Lewis Shale, Pic-tured Cliffs Sandstone, Fruitland Formation, OjoAlamo Sandstone, and Nacimiento Formation(depths of 4,263 to 3,437 ft). These samples weresubmitted to R.H. Tschudy (USGS) for palynologicanalysis, and he reported (1973, p. 131) that 30samples yielded sufficient specimens for a percent-age count. Tschudy found that all of the FruitlandFormation samples contained abundant specimensof Proteacidites spp. (Tschudypollis) and, that theoverlying Ojo Alamo Sandstone contained thePaleocene index fossil Maceopolipollenites tenui-polus (Momipites tenuipolus) and a few reworkedspecimens of Proteacidites spp. On the basis ofthese palynologic data, Tschudy placed the Creta-ceous-Tertiary boundary in the GB-1 core at thebase of the Ojo Alamo Sandstone.

Tschudy (1973) also compared the palyno-morph assemblages from the Gasbuggy core withthose of other Western-Interior basins, including,the nearby Raton Basin of northeastern New Mex-ico and southwestern Colorado. On the basis ofthose comparisons, Tschudy concluded that upper-most Campanian-age and all Maastrichtian-agerocks were missing in the Gasbuggy core indicat-ing the presence of a significant hiatus separatingthe Paleocene Ojo Alamo Sandstone from theunderlying Campanian Fruitland Formation in theSan Juan Basin.

50


Mesa Portales. The palynology of strata adjacentto the K-T interface at Mesa Portales was dis-cussed in Fassett and Hinds (1971). These authorscollected rock samples for palynologic analysisfrom the uppermost Kirtland-Fruitland Formation(undivided) and from the Ojo Alamo Sandstone onMesa Portales (Figures 1, 21). R.H. Tschudy ana-lyzed the samples and found (in Fassett and Hinds1971, p. 31,33, and table 1) that the K-T interfaceat Mesa Portales was in the uppermost part of theKirtland-Fruitland interval, 13 m below the base ofthe Ojo Alamo Sandstone (Figure 23). Tschudyconcluded that the uppermost 13 m of the Kirtland-Fruitland Formation and all of the Ojo Alamo Sand-stone at Mesa Portales were Paleocene in age(Figures 22-25). Additional samples were subse-quently collected at Mesa Portales from other partsof the Fruitland-Kirtland Formation and from theOjo Alamo Sandstone and palynomorph lists iden-tified by Tschudy from those samples are publishedfor the first time in the Appendix of this paper.These new data confirmed that the K-T interface atMesa Portales is 14 m below the base of the OjoAlamo Sandstone in uppermost Fruitland-Kirtlandstrata (Figure 23). All samples from below thisinterface yielded large numbers of Proteaciditesspp., and no specimens of this Cretaceous indexfossil were found above this level. One sample 5 mbelow the base of the Ojo Alamo (D6583-B of Fig-ure 23) yielded the Paleocene index fossil M. tenu-ipolus. Thus the Ojo Alamo Sandstone isunequivocally Paleocene in age in its entirety atMesa Portales.Ojo Alamo Sandstone Type Area. The Ojo AlamoSandstone type area is between Hunter Wash andDe-na-zin Arroyo in the southwest part of the SanJuan Basin (Figures 1, 4). The Ojo Alamo Sand-stone contains abundant dinosaur fossils in thisarea. As discussed in the Appendix, palynologicdata from strata adjacent to the K-T interface in theOjo Alamo Sandstone type area have been pre-sented in several publications. In addition, theAppendix also presents unpublished palynomorphlists for this area from the files of the author. Thesedata show that all of the many rock samples fromthe Cretaceous Fruitland and Kirtland Formationsin this area have yielded abundant specimens ofTschudypollis spp. One sample from the upper-most Kirtland Formation (less than 1-m below thebase of the Ojo Alamo) has yielded the Paleoceneindex palynomorph M. tenuipolus and a fewreworked specimens of Tschudypollis spp. Severalsamples from mudstone interbeds in the upper partof the Ojo Alamo in this area have also yielded

Paleocene index palynomorphs and no specimensof Tschudypollis spp.

On the basis of these data, the K-T interfaceis placed just below the base of the Ojo AlamoSandstone in the Ojo Alamo Sandstone type area.San Juan River Site. Rock samples collected forpalynologic analysis from the Ojo Alamo Sand-stone at the San Juan River site from a coaly, car-bonaceous shale interbed, 13 m above the base ofthe Ojo Alamo Sandstone, have yielded the Paleo-cene index fossil M. tenuipolus; in addition onesample also yielded the Paleocene index fossilBrevicolporites colpella. The carbonaceous shaleyielding these Paleocene palynomorphs is 3.5 mbelow the level of a large hadrosaur femur col-lected from this locality. Some, but not all of thesesamples, also yielded rare, reworked specimens ofTschudypollis spp. The presence of two Paleoceneindex palynomorphs from the Ojo Alamo Sand-stone at the San Juan River site provides conclu-sive evidence that the Ojo Alamo Sandstone isPaleocene in age at this location.Durango Area. Studies of the palynology of rockstrata adjacent to the K-T interface were conductedby Manfrino (1984) and Newman (1987) in an areain the northern San Juan Basin near Durango, Col-orado (Figure 1). The results of those studies aresummarized in Newman (1987). The rock strataadjacent to the K-T interface in the Durango areaare different from those in the New Mexico part ofthe San Juan Basin because: 1) The Animas For-mation rather than the Ojo Alamo Sandstone over-lies the K-T interface in the northern San JuanBasin (Figure 1.1), and 2) The McDermott Forma-tion is the stratigraphically highest Cretaceous rockunit in that area. The lower part of the Animas For-mation is the same age as the Ojo Alamo Sand-stone, even though the two formations aredistinctly different, lithologically, and the Animas ismuch thicker: about 335 m in the Durango area.The upper part of the Animas Formation in thenorthern San Juan Basin is time equivalent to theNacimiento Formation in the southern part of thebasin even though the two formations are lithologi-cally distinct (Fassett 1985).

The Appendix contains a summary of New-man’s (1987) findings regarding the biochronologicsignificance of the palynomorphs identified fromrock samples collected from uppermost Creta-ceous and lowermost Paleocene strata in the Dur-ango, Colorado area. Newman showed that thepalynomorph assemblages from the uppermostLewis Shale, Pictured Cliffs Sandstone, and mostof the Fruitland Formation are late Campanian in

51


age, and that most of the Kirtland Formation andthe lower half of the McDermott Formation yieldedpalynomorphs of early Maastrichtian age. He alsoshowed that the Animas Formation containspalynomorphs of early Paleocene age. Newman(1987) placed the K-T interface at the base of theAnimas Formation in the Durango, Colorado area.Newman also concluded (p. 158) that based on hispalynologic studies in this area: “Approximately theupper half of the Maastrichtian Stage is not repre-sented, and perhaps some earliest Paleocene ismissing as well between McDermott and Animasstrata.”

Newman’s finding that the Animas Formationis Paleocene in the northern San Juan Basin sup-ports earlier conclusions by Knowlton (1924) whoconducted an extensive study of leaf fossils in theAnimas Formation. Knowlton stated (p. 71) that theAnimas is:

. . . undoubtedly Tertiary. Not a single species is known to be common to the Animas formation and the Cretaceous exclusively—in fact, there are only five species that extend into the

acknowledged Cretaceous anywhere.

Summary

Figure 36 summarizes the palynologic bio-chronology of strata adjacent to the K-T interface inthe San Juan Basin. The six columns show thelocalities where palynology definitively establishesthe age of the Ojo Alamo Sandstone (or lowermostAnimas Formation) in the San Juan Basin. The col-umn headed “Durango Area” shows that the Creta-ceous-Tertiary (K-T) interface is at the base of theAnimas Formation—top of the McDermott Forma-tion based on palynology. The McDermott restsconformably on top of the Kirtland Formation and isonly found in a small area in the northwest part ofthe San Juan Basin (Fassett 1985).

At the San Juan River locality (Figure 36), twoPaleocene index palynomorphs M. tenuipolus andB. colpella were identified from samples about 13m above the base of the Ojo Alamo Sandstonewhere it rests unconformably on the Kirtland For-mation. No samples have been collected from theKirtland for palynologic analysis at this locality, thusthe K-T interface is not bracketed by palynomorphassemblages here. At the Ojo Alamo type area, the

Mesa Portales

Gasbuggy core

San Juan River

Cuba Area

Durango Area

Ojo AlamoType Area

Animas Fm. Ojo Alamo Ss

Ojo Alamo Ss

Nacimiento Fm.

Ojo Alamo SsOjo Alamo Ss

Fruitland Fm.Fruitland Fm.McDermott Fm. Kirtland Fm.

Kirtland Fm.Fruitland -Kirtland Fm.

Ojo Alamo Ss

73.04 Ma0

130

120

110

100

50

40

30

30

20

20

10

10

90

80

70

60

meters

DATUMbase Ojo Alamo Ss

Cretaceous-Tertiary interface

LEGEND

Paleocene Dinosaur bone

Cretaceous (Judithean) Dinosaur bone

Cretaceous pollen -- Tschudypollis, etc.

Ash bed J with sanidine Ar/ Ar age

Paleocene (Puercan) mammal bone

40 39

70 313 kilometers10545 16 77

?

Paleocene pollen -- M. tenuipolus, etc.

Figure 36. Stratigraphic columns showing formations adjacent to Cretaceous-Tertiary (K-T) interface at six localitiesin San Juan Basin (Figure 1) where palynologic data have precisely fixed its stratigraphic position. Interface is palyno-logically bracketed at all localities except San Juan River site. K-T interface coincident with base of Ojo Alamo Sand-stone or Animas Formation except at Mesa Portales and possibly locally in Cuba area. Complete palynomorph lists inthe Appendix.

52


basal contact of the Ojo Alamo Sandstone with thetop of the Kirtland Formation is closely bracketedby palynologic assemblages indicating that all OjoAlamo strata are Paleocene in age there.

At Mesa Portales, palynologic data show thatnot only is the Ojo Alamo Sandstone Paleocene inits entirety, but about 14 m of the underlying Fruit-land-Kirtland Formation is Paleocene as well. Inthe Cuba area and in the Gasbuggy core, Paleo-cene and Cretaceous palynomorph assemblagesclosely bracket the basal contact between the baseof the Ojo Alamo Sandstone and the top of theFruitland Formation providing conclusive evidencethat the Ojo Alamo at those places is Paleocene inits entirety.

In summary, at all localities where palyno-morphs have been identified bracketing the base ofthe Ojo Alamo Sandstone or Animas Formation,Cretaceous palynomorphs such as Tschudypollisspp. are found in large numbers in underlying Cre-taceous strata and Paleocene palynomorphs suchas M. tenuipolus and (or) B. colpella are found inthe Ojo Alamo and lowermost Animas orNacimiento Formations. At three localities SanJuan River, the Ojo Alamo type area, and the Gas-buggy core hole (Figure 36) rare, reworked speci-mens of the Cretaceous index palynomorphTschudypollis have been identified in some sam-ples in the lowermost part of the Ojo Alamo Sand-stone but at the other localities shown on Figure36, Tschudypollis has not been identified in the OjoAlamo or Animas Formations. The weight of thepalynologic evidence thus supports the conclusionthat the Ojo Alamo Sandstone and the Animas For-mation are Paleocene in age in their entiretythroughout the San Juan Basin.

In addition, because M. tenuipolus has beenshown to be present only in the upper part of bio-zone P1 in many Western Interior basins (includingthe nearby Raton Basin) and absent in lowermostPaleocene strata (Nichols 2003), the presence ofthis guide fossil in lowermost Paleocene strata inthe San Juan Basin suggests that strata represent-ing the lower part of biozone P1 is not present inthe San Juan Basin (see discussion in the Appen-dix). This finding supports paleomagnetic evidence(discussed above) suggesting that the lowermostPaleocene strata in the San Juan Basin are 63.2Ma (Figures 34, 35).

VERTEBRATE PALEONTOLOGY

Vertebrate fossils have been known to exist instrata adjacent to the Cretaceous-Tertiary (K-T)boundary in the San Juan Basin since the work of

Cope (1881). Subsequently, many vertebrate pale-ontologists visited the southern San Juan Basinand collected large numbers of vertebrate fossils inK-T strata that have been discussed and describedin numerous publications up to the present day; fora list of the principal references to those publica-tions see Williamson (1996), Fassett et al. (2002),and papers in Lucas and Heckert (2000). Adetailed discussion of the history of vertebratepaleontology in the San Juan Basin is beyond thescope of this report but such discussions may befound in papers by Clemens (1973b), Fassett(1973), Powell (1973), Simpson (1981), and in Wil-liamson (1996). This report focuses on the bio-chronologic significance of vertebrate fossils fromthe Paleocene Ojo Alamo Sandstone, Animas For-mation, and the lowermost part of the NacimientoFormation, with brief discussions of vertebratesfrom underlying Cretaceous strata.

Vertebrate paleontology has had limited bio-chronologic value in determining the age of strataadjacent to the K-T interface in the San JuanBasin. However, with the publication of a series ofsix radiometric ages throughout the CretaceousFruitland and Kirtland Formations (Fassett andSteiner 1997; Fassett 2000), the precise ages ofthe vertebrate assemblages in these strata havenow been established. This temporal calibration ofLate Cretaceous (Campanian) vertebrates in theSan Juan Basin provides a standard to correlatefaunal zones of the San Juan Basin to other West-ern Interior basins where such data sets may beless complete.

Dating of the Paleocene Ojo Alamo Sand-stone on the basis of robust palynologic data and,independently, on the basis of paleomagnetism(Fassett and Lucas 2000, Fassett et al. 2002, andthis report) has now established the Paleoceneage of this formation and its contained vertebrate-fossil assemblage: the “Alamo Wash local fauna..Correlation of these Paleocene vertebrates to otherNorth American basins may improve our under-standing of the survival of various “Lancian”-aspectvertebrates across the Cretaceous-Tertiary inter-face.

Dinosaurs

Cretaceous Kirtland and Fruitland Formations.Dinosaurs of the Fruitland and Kirtland Formationsin the San Juan Basin were summarized in Lucaset al. (2000, p. 87, 88). Sullivan and Lucas (2006,p. 18-20) also presented a detailed analysis of thedinosaur taxa identified from these formations anddefined their new “Kirtlandian” land vertebrate age

53


as being “equivalent to 2.2 m.y. of Campaniantime” falling between the Judithian and Edmonto-nian land-vertebrate ages of the northern part ofthe Western Interior of North America. Sullivan andLucas (2006) is an amplification of the Sullivan andLucas (2003) paper in which the “Kirtlandian” namewas first proposed. Paleocene Ojo Alamo Sandstone. In 1983, alarge—1.3 m long—right hadrosaur femur was dis-covered about 15 m above the base of the Ojo

Alamo Sandstone at the San Juan River locality(Figure 1.1). This bone was imbedded in the lowerpart of a vertical cliff face of coarse-grained, con-glomeratic sandstone; only one surface of this fos-sil was partially exposed when it was discovered(Fassett and Lucas 2000, figure 3A). This fossilwas subsequently excavated and prepared and isnow on display at the University of New Mexico,Earth and Planetary Sciences Department in Albu-querque. This specimen is described in detail inFassett and Lucas (2000); Figure 37.1 is a colorphotograph of this bone.

Fassett and Lucas stated that because thisfossil was so massive and its outer surface so pris-tine (Figure 37.1), this bone could not possiblyhave been reworked from underlying Cretaceousstrata into the high-energy, conglomeratic, OjoAlamo Sandstone, and they wrote (p. 228): “Wesuggest that the hadrosaur represented by thisfemur lived in early Paleocene time and died nearthe place where this specimen was found.” ThePaleocene age of the Ojo Alamo Sandstone at theSan Juan River site (reported in Fassett and Lucas2000) was established by the presence of Paleo-cene index palynomorphs in the lower Ojo Alamo,below the level of the hadrosaur femur. A sampleof this hadrosaur femur was chemically analyzedand found to have distinct elemental concentra-tions characteristic of Paleocene dinosaur bone inthe San Juan Basin. (The chemistry of Cretaceousvs. Paleocene dinosaur-bone samples from theSan Juan Basin is discussed in detail in a subse-quent section of this report.)

Sullivan et al. (2005, p. 401) discussed thehadrosaur femur from the Ojo Alamo Sandstone atthe San Juan River site, as follows:

However, despite the bone’s near-pristine appearance, we argue here, largely based on parsimony [my emphasis], that the bone has been reworked, and not transported any significant distance, thereby preserving the integrity of the bone’s outer surface.Three points are relevant to this suggestion

that this specimen is “reworked”: 1) The femur wasfound 15 m above the base of the Ojo AlamoSandstone in an area where the contact of the OjoAlamo Sandstone and the underlying Kirtland For-mation is essentially a planar surface; there is noconceivable way this bone could have been weath-ered out of the underlying Cretaceous strata andbeen redeposited 15 m above the base of the OjoAlamo without moving it a “significant distance”; 2)The word “parsimony”, as used above apparently

37.2

37.3

0 .5 1 meter

damaged by erosion

37.1

Figure 37. Photographs of three dinosaur bones fromOjo Alamo Sandstone showing different degrees ofpreservation. Bone in 37.1 is right hadrosaur femurfrom San Juan River site; bone is almost perfectly pre-served (photo from Fassett et al. 2002). Bone in 37.2 issauropod femur from Barrel Spring area (letter O onFigure 4); well preserved where encased in bed rock,but end in upper right has been subjected to subaerialerosion, become fragmented, and part is missing (Pho-tograph from R.M. Sullivan). Bone in 37.3 is also fromBarrel Spring area (letter N on Figure 4); bone is badlyfragmented, however shape of large limb bone still dis-cernible (dashed outline). Hammer 0.33 m long; ham-mer handle scaled in tenths of foot.

54


means adherence to the concept that dinosaursare defacto Cretaceous index fossils; it is sug-gested that adherence to this precept, in the faceof overwhelming physical evidence to the contrary,is not parsimonious; 3) The hadrosaur femur’schemistry strongly suggests that it is a Paleocenebone (see the “Geochemistry of Vertebrate BoneSample” section of this report). Sullivan, Lucas,and Braman (2005) offer no new evidence contra-vening these facts.

With the exception of the San Juan Riverlocality, all dinosaur remains from the Ojo AlamoSandstone are from the southwestern part of theSan Juan Basin between Hunter Wash and Beton-nie Tsosie Wash (Figures 1, 3). Within this region,the highest concentration of dinosaur bone is in theOjo Alamo Sandstone type area: from just west ofHunter Wash to just east of De-na-zin Wash (Fig-ure 4). Dinosaur fossils have also been found rela-tively recently in the Ojo Alamo Sandstonesoutheast of the type area near Betonnie TsosieWash (Figure 11). Fassett et al. (2002) discussedand referenced all significant published reports ofdinosaur fossils from the Ojo Alamo Sandstoneand listed the following dinosaurs from that forma-tion (as reported by Lucas et al. 2000, p. 88): Alam-osaurus sanjuanensis; ?Albertosaurus sp., cfTyrannosaurus sp.; ankylosaurid, indeterminate;dromaeosaurid, indeterminate; hadrosaurids, inde-terminate; nodosaurids, indeterminate; orni-thomimid, indeterminate; Pentaceratops;saurornithoidids, indeterminate; Torosaurus cf. T.latus.

The “Pentaceratops” specimen was reexam-ined (Sullivan et al. 2005, p. 567), and theseauthors determined that this fossil should be rela-beled “chasmosaurine, indeterminate.” Glyptodon-topelta mimus, according to R.M. Sullivan(personal commun., 2006) should be added to thelist along with Tyrannosauridae, indeterminate.Sullivan et al. (2005) indicated that all specimensfrom the Ojo Alamo originally named Torosauruswere incorrectly identified and suggested that thename Torosaurus be replaced by “chasmosaurine,indeterminate.” Farke (2002), however, indicatedthat specimen NMMNH P.22884 from the OjoAlamo is the ceratopsian Torosaurus cf T. utahen-sis , thus this name is retained in the list of OjoAlamo dinosaurs. Specimen NMMNH P.25074 wasoriginally reported to be from the Ojo Alamo Sand-stone) and was referred to Torosaurus sp. by Farke(2002). Sullivan et al. (2005), however, stated thatthis specimen was from the uppermost KirtlandFormation, not the Ojo Alamo Sandstone, and

moreover determined that this specimen was notTorosaurus and should thus be labeled “chasmo-saurine, indeterminate.” Sullivan (personal com-mun., 2006) suggested that the name“saurornithoidids, indeterminate” be removed fromthe dinosaur-fossil list of Lucas et al. (2000) repro-duced above.

Williamson and Weil (2001) listed additionaldinosaurs identified from vertebrate microfossilsites in the Ojo Alamo Sandstone (their “Naashoib-ito Member” of the Kirtland Formation), as follows:

At the top of the Kirtland Formation, the Naashoibito Member (Alamo Wash local fauna) has yielded teeth of, in decreasing order of abundance, ceratopsids, titanosaurids, hadrosaurids, tyrannosaurids including cf. T. rex, and species of Troodon and Richardoestesia distinct from those of from (sic) the Fruitland and lower Kirtland Formations.Thus, a revised list of dinosaur specimens

identified from the Ojo Alamo Sandstone is: Alamo-saurus sanjuanensis; ?Albertosaurus sp., cf Tyran-nosaurus sp.; ankylosaurid, indeterminate;dromaeosaurid, indeterminate; Glyptodontopeltamimus; hadrosaurids, indeterminate; nodosaurids,indeterminate; ornithomimid, indeterminate; Rich-ardoestesia sp.; cf titanosaurids, indeterminate;Torosaurus cf T. utahensis; Troodon sp.; Tyrano-saurus rex; and tyrannosaurid, indeterminate.

Many of the dinosaur fossils identified fromthe dozens of known occurrences in the Ojo AlamoSandstone in the Ojo Alamo type area and else-where in the San Juan Basin are labeled “indeter-minate” because nearly all specimens are singlelimb bones or parts of bones that cannot be identi-fied as to genus and species. Some of these singlebones are pristine and beautifully preserved, suchas the hadrosaur femur from the San Juan Riverlocality (Figure 37.1). Figure 37 shows three OjoAlamo Sandstone dinosaur fossils in variousstages of preservation ranging from being virtuallyperfectly preserved (Figure 37.1) to partially ornearly totally fragmented (Figure 37.2, 37.3); muchof the dinosaur bone found in the Ojo Alamo is inthe latter category. In at least one locality (sample020103, locality H, Figure 4), bone fragments fromseveral animals are preserved in a paleo channel-lag deposit.

The disintegration of dinosaur bone, as itweathers from its matrix, subaerially, (Figure 37)offers a compelling argument against the reworkingof intact dinosaur bones from underlying strata intohigher strata. Such reworking would require the

55


weathering-out of such bones, intact andunabraded, from their original matrix, millions ofyears after their original entombment, and thenrequire that they be transported long distances lat-erally to a place topographically lower but strati-graphically higher than the original bone site. Thefragmentation and dispersal of the weathered dino-saur fossils of Figure 37.2 and 37.3 shows whysuch a scenario is unlikely to impossible. Even thepristine hadrosaur femur from the San Juan Riversite was beginning to degrade as it weathered outof the cliff face where it was found (Figure 37.1),

and its continued erosion would have resulted inthe total fragmentation and destruction of this spec-imen.

A commonly proposed scenario for reworkingfossils from older into younger strata supposes thaton a high-relief surface, a channel scour mightundercut a topographically higher exposure ofolder strata resulting in a bone encased in thatstrata being dropped into a channel of youngerage. This very unlikely scenario, however, wouldresult in the displaced bone’s being emplaced inthe younger strata within a disoriented exotic block

38.1

38.2

Figure 38. Photograph and drawing of hadrosaur-bone assemblage in lower part of Ojo Alamo Sandstone at AlamoWash locality of Hunt and Lucas (1991). Locality is letter I of Figure 4. Bone-sample from scapula was chemically ana-lyzed (sample P-19147 of the Appendix tables). Hammer 0.25 m long. Photograph by S.G. Lucas, New MexicoMuseum of Natural History and Science, Albuquerque, New Mexico 38.1 Partially excavated bone assemblage beforejacketing and removal. 38.2 Drawing of hadrosaur skeleton (from Hunt and Lucas 1991, figure 3) showing positions ofbones (shaded) identified in bone assemblage of photograph 38.1. Length of skeleton is 13.5 m. Figure is from Fas-sett et al. (2002).

56


of rock that would be clearly apparent. The largehadrosaur bone from the San Juan River site wasdefinitely not encased in an exotic block of Creta-ceous strata because, as discussed above, upper-most Cretaceous strata in the San Juan Basin areinvariably fine- to medium-grained, whereas, OjoAlamo strata are coarse-grained and conglomer-atic. Figure 7 of Fassett et al. (2002) contains aphotograph of the San Juan River site hadrosaurfemur in place; that photograph clearly shows thisfossil encased in coarse-grained conglomerate thatis clearly an integral part of the surrounding rockstrata. Moreover, none of the dozens of other dino-saur bones found in the Ojo Alamo in the southernpart of the basin are contained in down-droppedexotic blocks. It would thus seem that the down-dropped-block scenario for all of the many dino-saur bones in the Ojo Alamo Sandstone at numer-ous localities in the San Juan Basin is not realistic.

The most significant, unequivocally in-place,dinosaur-bone assemblage found in the Ojo AlamoSandstone in the San Juan Basin contained 34skeletal elements from a single hadrosaur.Although not literally an articulated skeleton, theseskeletal elements are doubtless from a single ani-mal. This bone assemblage was described by Huntand Lucas (1991) and was also discussed in Fas-sett et al. (2002) as providing clear evidence thatthese bones could not possibly have beenreworked from underlying Cretaceous strata andthus were from an animal that lived and died in OjoAlamo Sandstone (early Paleocene) time. Thelocation of this site is shown on Figure 4 (locality I,sample no. P 19147). Figure 38 (reproduced fromFassett et al. 2002, figure 18, p. 327) shows thispartially excavated bone assemblage.

The question of possible reworking of themany single-bone dinosaur specimens found in theOjo Alamo Sandstone was addressed by Fassettet al. (2002). These authors presented chemical

analyses of Cretaceous and Paleocene dinosaur-bone samples showing that critical elemental con-centrations in them were distinctive. An additional14 bone samples were subsequently analyzed; sixfrom the Ojo Alamo Sandstone, six from the Kirt-land Formation, and two not in place.

These chemical analyses showed a higherabundance of uranium and a lower abundance ofrare-earth elements (REE) in Paleocene bonesamples and lower uranium and higher REE con-centrations in Cretaceous bone samples. The dis-tinctly different chemical “fingerprints” indicate thatthe Paleocene dinosaur bones were mineralized inplace in the Ojo Alamo Sandstone in early Paleo-cene time and thus could not represent bones thathad been reworked from underlying Cretaceousstrata. One of the Paleocene bones chemicallyanalyzed was a scapula from the 34-bone assem-blage from a single hadrosaur, discussed above.(The geochemistry of dinosaur-bone samples fromstrata adjacent to the K-T interface is summarizedbelow in the “Geochemistry of Vertebrate BoneSamples” section of this report.)

The biochronologic age of dinosaur bonesfrom the Ojo Alamo Sandstone has been muchdebated over the years: Some workers haveassigned a Lancian age to these fossils (Lucas etal. 1987, Hunt and Lucas 1992, Weil and William-son 2000, and Williamson and Weil 2001, forexample). Other workers (Lucas et al. 2000, p. 88),however, state that whereas the “conventionalview” is that the Ojo Alamo dinosaur bones are “ofMaastrichtian age, or Lancian in terms of verte-brate biochronology” a “reasonable alternative” forthe age of these fossils is that they are “late Cam-panian”. Conclusions by Sullivan, Boere, andLucas (2005) and Sullivan, Lucas, and Braman(2005) are far less equivocal stating that the OjoAlamo dinosaur fossils are “early Maastrichtian” in

Land surface

NESW

CONM

TK


Kirtland Formation

AnimasFormationOjo Alamo Sandstone

Figure 39. Diagrammatic cross section across San Juan Basin showing relations of formations near Cretaceous-Tertiary (K-T) interface. Modified from Fassett (1985).

57


age or “near the Campanian-Maastrichtian bound-ary.”

Farke and Williamson (2006 p.1019), on theother hand, concluded that the biochronologic ageof the Ojo Alamo Sandstone (their NaashoibitoMember of the Kirtland Formation) based on bothdinosaur and mammal fossils was Lancian. Theystated:

We consider the Naashoibito Member and the Alamo Wash local fauna to be of latest Cretaceous age (Lancian land-mammal age) based on the presence of cf. T. rex (Carr and Williamson 2000) and the Lancian index mammal Essonodon browni (Lehman 1984; Williamson and Weil 2003). This correlation refutes a late Campanian or early Maastrichtian age for the Naashoibito Member (e.g., Sullivan, Lucas, and Braman [2005]).

Paleocene Animas Formation. Knowlton (1924)identified fossil leaves from Animas Formation col-lections from 24 numbered localities. The strati-graphic levels of these localities ranged from about60 m above the base of the Animas to near its topmore than 500 m above the base of the formation.Knowlton (p. 71) concluded that based on thesefossils the Animas Formation was “undoubtedlyTertiary.”

Because of the antiquity of Knowlton’s (1924)study of fossil leaves in the Animas Formation, K.Johnson, with the Denver Museum of Nature andScience, Denver, Colorado, was asked to reviewKnowlton’s faunal lists from the Animas Formationand Knowlton’s conclusion that this floral assem-blage was indicative of a Paleocene age for theAnimas. Johnson reported (personal commun.,2008): “I would conclude that the Animas is proba-bly early Paleocene.” Newman (1987), as dis-cussed above, reported that the Animas Formationnear Durango, Colorado, was Paleocene based onits contained palynomorphs.

Newman’s (1987) palynologic studies thusconfirm Knowlton’s (1924) fossil-leaf studies indi-cating a Paleocene age for the Animas Formation.In addition, these studies demonstrated that thelowermost part of the Animas Formation is thesame age as the Ojo Alamo Sandstone in thesouthern part of the San Juan Basin. (Figure 39 isa diagrammatic portrayal of Animas-Ojo Alamorelations.) Newman also confirmed the assertionby Reeside (1924) that a substantial unconformityis present between the base of the Paleocene Ani-mas Formation and underlying Cretaceous strata.Newman’s suggestion that “perhaps some earliest

Paleocene is missing” from the lowermost Animasis in agreement with the same findings for thebasal Ojo Alamo Sandstone in the southern SanJuan Basin on the basis of paleomagnetism andpalynology, as discussed in the Paleomagnetismand Palynology sections of this report.

The principal published references to dino-saurs found in the Animas Formation in the north-ern San Juan Basin are in Reeside (1924; p. 32,34, and 52-53). Unfortunately, Reeside did not pro-vide specific localities for any of the dinosaur-bonesites he referred to, other than “near the dividebetween the Pine and Piedra rivers” for one ofthem. There is no evidence that any of the AnimasFormation dinosaur fossils referred to by Reesidewere ever collected.

A search was made of the USGS field notesarchives at the Denver Federal Center, Denver,Colorado, in an attempt to find more specific dino-saur-bone localities in the Animas Formation.Because one of Reeside’s (1924) references to anAnimas dinosaur-bone locality contained this foot-note: “Gardner, J.H., unpublished data,” Gardner’sfield note books were carefully examined. The onlyreference to Animas dinosaurs found in Gardner’sfield notes is reproduced in its entirety on Figure40. This note indicated that Gardner, in 1907, haddiscovered a “Triceratops” specimen in the AnimasFormation about 35 feet (11 m) above its base.This fossil was apparently considered to be of suffi-cient importance that J.W. Gidley, vertebrate pale-ontologist at the American Museum of NaturalHistory, made a special trip to investigate this site.Unfortunately, the specific location of this fossil siteis not given, nor is it known if this specimen wasever collected. Nevertheless, this note does con-firm the presence of a recognizable ceratopsiandinosaur fossil in the lowermost part of the AnimasFormation in the Colorado part of the San JuanBasin.

Apparently the presence of dinosaur fossils inthe Animas Formation was common knowledgeamong vertebrate paleontologists working in thearea at that time, as indicated in a paper by Simp-son (1950, p. 86). In this report, Simpson statedthat “Dinosaurs have been found in middle andlower parts of the Animas in Colorado . . .” Simp-son, however indicated that the “Cretaceous-Ter-tiary transition occurs within this formation[Animas], at an undetermined level.” Simpsonclearly thought that the K-T boundary should beplaced above the highest dinosaurs in spite ofKnowlton’s (1924) assertion that the Animas For-mation was Paleocene based on fossil leaves.

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Simpson (1950, p. 85) is known to haveworked on the Paleocene in the San Juan Basin forthe American Museum beginning in 1929. Simp-son’s colleague at the American Museum, WalterGranger, had worked in the basin in 1912 through1914 and in 1916. And another colleague, J.W.Gidley, had visited a ceratopsian bone site withReeside in 1909 (Figure 40). It is probable thatGranger and USGS geologists Reeside and Gard-ner also made field trips together and may haveeven visited Animas-Formation, dinosaur-bonelocalities together in the northern part of the SanJuan Basin. The reference to Gidley in Gardner’sfield notes (Figure 40) clearly indicated that theAmerican Museum staff of vertebrate paleontolo-gists was well aware of the presence of dinosaursdiscovered in the Animas Formation by USGSgeologists. Although no dinosaur-bone locality hasbeen located in the Animas Formation in moderntimes, there can be no doubt that these localitiesdo exist and thus remain to be rediscovered.

Reeside (1924, p. 32 and Appendix) con-cluded that:

In view of the wide differences in opinion expressed by various students as to the correct assignment of this whole group of related formations, the Ojo Alamo sandstone and Animas formation are herein classified as Tertiary (?).

This conclusion by Reeside (1924) was star-tling and not a trivial one. Reeside had done fieldwork throughout the San Juan Basin for manyyears, had measured thousands of meters of sec-tion through all of the rocks adjacent to the Creta-ceous-Tertiary interface, and was well aware of theabundance of dinosaur bone in the Ojo AlamoSandstone in the southern San Juan Basin and inthe Animas Formation in the northern San JuanBasin. Reeside was certainly well aware of the sig-nificance of dinosaur bone as a Cretaceous indexfossil in terrestrial strata in the Western Interior ofNorth America. In spite of this, Reeside concludedthat the Animas and Ojo Alamo were “Tertiary (?) inage.” (It is suggested that Reeside’s query mayhave been added to mollify vertebrate paleontolo-gists and/or USGS editors of his time.) Reeside’sdiscussions of the data in his 1924 USGS Profes-sional Paper leave no doubt that he considered theOjo Alamo and Animas Formations to be Tertiary inage. It is thus clear that Reeside, in 1924, was thefirst known geologist to challenge (albeit tacitly) thethesis that all dinosaurs became extinct at the endof the Cretaceous.

This discussion of dinosaur fossils in thePaleocene Animas Formation provides powerful,additional, independent evidence that dinosaurslived in the San Juan Basin area in early Paleo-cene time. These findings, that have been slum-bering in the published (and unpublished) literaturefor more than 80 years, seem to have been over-

Figure 40. Copy of entry in field notes of J.H. Gardner dated Friday, August 27, 1909. Entry reads: “Gidley & I driveeast to see dinosaur (Triceratops) in Animas that I found in 1907. About 35 ft above coarse, gr. blue igneous s.s.base Animas resting on Laramie drab shales some 50 ft. above [?word]-gray s.s. Top Laramie.” J.W. Gidley was avertebrate paleontologist with American Museum of Natural History. (Field note entry discovered and copy providedby F. Peterson (USGS, Emeritus), Denver, Colorado.)

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looked or ignored by nearly all subsequent workersin the San Juan Basin. Fassett et al. (2002) brieflyreferred to Reeside’s (1924) mention of Animasdinosaurs, however this report amplifies Reeside’swork and adds additional supporting data fromGardner’s 1909 field notes and Simpson’s 1950paper.

Mammals

Cretaceous Strata. Most of the mammalian fossilsdiscovered in Cretaceous strata in the San JuanBasin have been recovered relatively recentlyusing screen-washing techniques to primarilyrecover mammal teeth. Clemens (1973b) was thefirst paleontologist to conduct a concerted andextensive search for fossil mammals in upper Cre-taceous strata in the San Juan Basin. He workedprimarily in the southwestern part of the basin inFruitland and Kirtland Formation strata near theBisti Trading Post (since burned down, Figure 3),and he compiled the first list of mammal fossilsfrom these strata. Clemens considered thesemammals to be part of his “Hunter Wash localfauna” writing (p. 164) that this fauna had a “uniquecomposition” and questioned whether this faunadiffered from other faunas of the same age due toecological or biogeographic differences “or somecombination of these factors?” Clemens (1973b, p.154) concluded that the temporal significance ofhis Hunter Wash local fauna was uncertainbecause it contained genera and species “in asso-ciation with animals also known from the typeLance local fauna (Clemens 1964, 1973a), thefauna of the upper part of the Edmonton Formation(Lillegraven 1969), and those recovered from theJudith River (Sahni 1972) and Milk River forma-tions (Fox 1970).” Clemens concluded that “Differ-ences in local faunal composition are probably theresults of both biogeographic provinciality andinequality in age.”

Lindsay et al. (1981) added no new mammalidentifications from the Fruitland-Kirtland interval,but based on a review of Clemens (1973b) mam-mal list, stated (p. 422) that the Hunter Wash fauna“includes some and lacks other mammals” charac-terizing the Lancian Land Mammal Age and con-cluded that this fauna was late, but not latestCretaceous. This reinterpretation of the temporalsignificance of Clemens (1973b) mammal fauna (abolder and quite different interpretation from that ofClemens, as noted above) was one of the lines ofevidence that convinced Lindsay et al. (1981) thatthere was no unconformity at the base of the OjoAlamo Sandstone and thus (mistakenly) convinced

these authors that deposition had been continuousacross the Cretaceous-Tertiary interface in the SanJuan Basin. Fassett and Steiner’s (1997) discoveryof a 40Ar/39Ar single-crystal sanidine age of 73.04± 0.25 Ma for an altered volcanic ash bed (Ash J ofFigure 4) in the uppermost part of the Kirtland For-mation (less than 5 m below the base of the OjoAlamo Sandstone) in the Hunter Wash area refutedthe assertion of Lindsay et al. (1981) that upper-most Cretaceous strata in the Hunter Wash area“represent latest Cretaceous.”

Flynn (1986) reported on fossil mammals col-lected between 1975 and 1978 in conjunction withthe field studies of Lindsay et al. (1981). The Creta-ceous collections came from two areas labeled onFigure 3 as: FBS (Flynn Burnham South); and FK(Flynn Kirtland). The FBS locality is in the middle toupper part of the Fruitland Formation in the south-western part of the San Juan Basin, southeast ofthe Burnham Trading Post (Figure 3). The FKlocality consists of sites in the lower part of the Kirt-land Formation west of Alamo Wash; these siteswere apparently discovered by Lindsay et al.(1978, figure 2). Flynn listed his and previouslypublished Cretaceous mammal identifications ofClemens (1973b) in his table 3.

Flynn (1986, table 3, Figure 41 of this report),listed 19 mammal taxa from Cretaceous strata inthe southwest San Juan Basin and found that onfaunal grounds, the Hunter Wash local fauna wasearly Judithian near the Campanian/Maastrichtianboundary with an age of about 74 Ma.

Flynn’s colleagues (Lindsay et al. 1981), how-ever, had concluded that the Hunter Wash localfauna was in the upper part of paleomagneticchron C31n and the lower part of C30n suggestingaccording to Flynn (1986, p. 28) that this faunalassemblage was from strata “equivalent to the lateMaastrichtian with an age of about 68 Ma” Flynn(1986, p. 28) opted to side with the geophysicaldata, concluding that: “The most parsimonious cor-relation of the normal magnetozones, without theprejudice of biochronological assumptions, is withanomalies 30 and 31.” (It is now known that anom-alies 30 and 31 of Lindsay et al. (1981) are reallymagnetochrons C32r and C33n, respectively.)

Rigby and Wolberg (1987) conducted anextensive study of microvertebrates collected froma small area in the southwestern part of the SanJuan Basin known as the Fossil Forest area. TheFossil Forest mammal quarry is about 18 kmsoutheast of the Bisti area (Figure 3) where Clem-ens (1973b) did his collecting and about 12 kmsoutheast of the Alamo Wash area where Flynn

60


(1986) collected. The Fossil Forest collectionscame from the lowermost Kirtland Formation andthus are at about the same stratigraphic level asClemens’ and Flynn’s Lower Hunter Wash collec-tion sites. Rigby and Wolberg (1987, p. 51) deter-mined that their collections were most closelyrelated to faunas of Sahni (1972) from the JudithRiver Formation and those of Fox (1977, 1979a,1979b, 1979c, and 1981) from the Oldman Forma-tion—a Judith River equivalent. These authors thusconcluded that “The age of the lowermost part ofthe Kirtland Shale must be near the Campanian-Maastrichtian boundary based on mammalian evi-dence.”

As discussed above, the age of the contactbetween the Fruitland Formation and overlyingKirtland Formation is now known to be 74.6 Ma inthe Ojo Alamo Sandstone type area (Figure 33);the precise age of dated ash 4 at about this level is74.55 ± 0.29 Ma (Fassett and Steiner 1997, Fas-sett 2000). The latest published global geologictime scale (Gradstein et al. 2004) puts the Campa-nian-Maastrichtian boundary at 70.6 Ma. Thus, themammal assemblages of Clemens (1973b) andRigby and Wolberg (1987), as well as the LowerHunter Wash mammalian fauna of Flynn (1986),can now be confidently placed in the upper Cam-panian with an age of 74.6 Ma; about 4 m.y. olderthan the Campanian-Maastrichtian boundary.

Sullivan and Lucas (2006, p. 20-21) discussedthe latest Cretaceous and earliest Paleocenemammals of the southern San Juan Basin, butadded nothing new to the above discussion. Noother studies of Cretaceous mammals from theSan Juan Basin have been published since theRigby and Wolberg (1987) paper.Paleocene Strata. The Ojo Alamo Sandstone hasyielded relatively few mammal-fossil localities inthe San Juan Basin, despite extensive searches inthat formation over the last three decades. Lehman(1984) was the first paleontologist to report a smallcollection of fossil mammals from the lowermostpart of the Ojo Alamo Sandstone (his NaashoibitoMember of the Kirtland Formation) in the type area(Figure 3). Lehman assigned a Lancian Age to theOjo Alamo because his collection contained a mul-tituberculate tooth identified as Essonodon browni.Flynn (1986) identified microvertebrates from theOjo Alamo (his Naashoibito Member of the Kirt-land) less than 2 km southeast of the Lehman(1984) site (Figure 3). Flynn named this assem-blage the Alamo Wash fauna and included in itLehman’s Essonodon browni (Figure 41). Flynn(1986, p. 26-27) concluded that: “Mammals fromthese high Kirtland strata appear to represent theLancian age, based on co-occurrence ofEssonodon browni (see Lehman 1984), Alphadonmarshi, and Mesodma formosa.”

Weil and Williamson (2000) presented prelimi-nary data from an Ojo Alamo Sandstone microver-tebrate site about 1 km north of the Lehman (1984)mammal site (Figure 3). They discussed the totalvertebrate assemblage from this site, includingdinosaurs, and stated that the Lancian index fossilEssonodon was the most common mammal foundin the Ojo Alamo. They also noted that Essonodonwas “relatively rare in localities of the northernWestern Interior, and the striking difference in rela-

Figure 41. Table 3 of Flynn (1986, p. 26) showing mam-mal taxa identified from Fruitland and Kirtland Forma-tions and Ojo Alamo Sandstone in southwestern SanJuan Basin. Mammal-bone localities are shown on Fig-ure 3: LHW includes localities labeled C and FK; 7592 isFK; BS is FBS; and Alamo Wash is FOA.

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tive abundance confirms speculation that latestCretaceous southern mammalian faunas differmarkedly from those of the northern Western Inte-rior, as do dinosaurian assemblages.”

Clemens and Williamson (2005, p. 212) cau-tioned that the geochronologic value of fossil mam-mals in Western North America is in a state of flux.They stated that the record of mammalian evolu-tion in the North American Western Interior is notyet complete as evidenced by “Fox and Naylor’s(2003) recent description of a new taeniodont fromAlberta [that] extended the range of this eutherianlineage from the Puercan (Pu2) back into the Lan-cian.” These authors also noted that the multituber-culate Stygimys that first appears in the northernpart of the Western Interior at the beginning of thePuercan (Pu1) “is a member of a local fauna ofJudithian age in Baja California del Norte (Weil2002).” The cautionary statements of these authorsregarding the current state of uncertainty about thebiochronologic status of various fossil mammalsbecause of the “incompleteness of the fossilrecord” are well advised. Moreover, these uncer-tainties tend to make less incredible the findings inthis paper that the fossil mammals of the OjoAlamo Sandstone (previously thought to be “Lan-cian”) are Paleocene in age. These mammalassemblages thus represent lineages that survivedacross the K-T boundary.

It seems clear that the use of fossil mammalsas index fossils for dating lower Paleocene strata inthe Western Interior of North America is prematureat this time because of: 1) limited numbers of col-lection sites; 2) biogeographic diversity of taxa; and3) limited knowledge of the evolution and radiationof mammals in earliest Paleocene time. The use ofmore robust geochronologic tools, such as palynol-ogy and isotopic and paleomagnetic dating ofstrata, as done in this study to confirm the Paleo-cene age of the Ojo Alamo Sandstone in the SanJuan Basin, will ultimately help us to better under-stand the biogeographic and temporal diversity ofmammals found near the K-T boundary throughoutthe Western Interior.Lowermost Nacimiento Formation. As discussedabove, the Nacimiento Formation intertongues withthe underlying Ojo Alamo Sandstone; thus, on thebasis of physical stratigraphy, it appears that depo-sition was continuous across this formation bound-ary. These formations are, however, distinctlydifferent lithologically: the Ojo Alamo is character-ized by massive, coarse-grained, conglomeraticsandstone beds deposited by high-energy braidedstreams flowing south to southeastward across the

San Juan Basin in early Paleocene time (Fassett2000, Fassett et al. 2002). The Nacimiento Forma-tion, however, at least in its lowermost part, con-sists of relatively finer-grained sediments depositedin a low-energy environment of low-gradientstreams interspersed with lakes and swamps. Thisdifference suggests that the pulse of high-energystream flow represented by the Ojo Alamo Sand-stone began suddenly about 65.2 Ma -300 k.y. intoPaleocene time - and ended abruptly a few hun-dred thousand years later. Such a pulse must havebeen driven by a corresponding rapid uplift andthen subsequent subsidence of a northern sourcearea.

Williamson (1996) published a detailed paperon the stratigraphy and mammalian biostratigraphyof the Nacimiento Formation in the southern SanJuan Basin that included a series of detailed mea-sured sections through the Nacimiento at selectedlocalities (Williamson 1996, appendix 1, p. 110-126). Williamson reported that Puercan (earliestPaleocene) mammals had been found in the lower-most part of the Nacimiento Formation at five local-ities in the southwestern part of the San JuanBasin between Gallegos Canyon and BetonnieTsosie Wash (Figure 3).

Figure 42 is a stratigraphic cross sectionshowing the five Puercan mammal-fossil localitiesand six Torrejonian localities in the lowermost partof the Nacimiento Formation; this figure is a modifi-cation of part of figure 9 of Williamson (1996). Thefossil-mammal levels shown by Williamson for theDNZW, WFKW, and BTW localities differ slightlyfrom those shown by Lindsay et al. (1981). At theDNZW and WFKW localities, the stratigraphic lev-els of Puercan mammals are from Lindsay et al.(1981). At the BTW locality, the levels of the Puer-can and uppermost Torrejonian fossils are fromLindsay et al. (1981, figure 10) and the lower Torre-jonian fossil level is from Williamson (1996, figure9). The fossil levels at the MDC section are fromSimpson (1959, figure 1) as explained below.

On Figure 42, the DNZW, BTW, and MDC col-umns are aligned on the base of magnetochronC29n (base projected for the BTW column). Col-umn GC is aligned with column DNZW on the topof the Ojo Alamo Sandstone. Column WFKW isaligned with the DNZW column on the top of chronC29n. Column EFKW is aligned with the WFKWcolumn on the top of the Ojo Alamo Sandstone.These alignments of the six columns appear to bequite reasonable in terms of the good correlation ofthe Puercan and Torrejonian fossil levels reportedat the six localities.

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The magnetic-polarity columns shown at theDNZW, WFKW, and the BTW localities are fromLindsay et al. (1981). (The DNZW section of Wil-liamson is at the same locality as the Barrel SpringArroyo (BSA) locality of Lindsay et al. 1981.) Thetop of magnetic-polarity chron C29n at the MDClocality was estimated based on a rate of deposi-tion for the lower part of the Nacimiento Formationof 143 m/m.y. This rate was calculated based onthe 40Ar/39Ar age of 64.40 ± 0.50 Ma for the young-est sanidine crystals from an altered volcanic ashbed found at the MDC locality (Fassett et al. 2007,Heizler personal commun., 2008). The level of thisash bed is shown on the MDC column on Figure42. Williamson numbered the magnetic polaritychrons on his figure 9 based on the reinterpretationof these chrons suggested by Butler and Lindsay(1985). These magnetic-polarity intervals, how-ever, are renumbered on Figure 42 in accordance

with the reevaluation of these chrons as discussedin detail in the “Paleomagnetism” section of thispaper.

Williamson (1996, p. 27) stated that there aretwo faunal zones within the Puercan of theNacimiento Formation in the southern San JuanBasin: a lower Ectoconus zone and an upper Tae-niolabis zone. Figure 42 shows the Ectoconuszone present at four localities and the Taeniolabiszone at two localities; both zones are foundtogether at only the DNZW locality where the Ecto-conus zone was found only 10 m above the top ofthe Ojo Alamo Sandstone. These two zonesappear to overlap very slightly at the DNZW andthe EFKW localities (Figure 42).

At the Mesa de Cuba (MDC) locality, the twoTorrejonian fossil levels shown on Figure 42 are 57m and 71 m above the base of the exposure at thefoot of Mesa de Cuba (Figure 43). Williamson

TK

FRUITLAND FM.

Base - chron C29n

12 17 3 9 72 113 k m

GC WFKW EFKW BTW MDCDNZW(BSA)

28 n

28 n

28 n

29 n

29(e)

32 r

29 r

29 r

Torrejonian mammal

Puercan mammal - Taeniolabis

Puercan mammal - Ectoconus

EXPLANATION

projected OJO ALAMO SANDSTONE

NACIMIENTO FORMATION

28 r

NOTES: 1. GC = Gallegos Canyon, DNZW = De-na-zin Wash (same locality as BSA - Barrel Spring Arroyo of Lindsay and others, 1981),WFKW = West Fork Kimbeto Wash, EFKW = East Fork Kimbeto Wash, BTW = Betonnie Tsosie Wash, MDC = Mesa de Cuba

29 n

29

28 r

Altered volcanic ash bed

29 n

interpolated

Torrejonian

64.432 Ma

Puercan

NW SE

64.40 Ma

Top C29n

Figure 42. Stratigraphic cross section showing levels of Paleocene mammal fossils identified in lowermost part ofNacimiento Formation, southern San Juan Basin, modified fromWilliamson 1996. Magnetic-polarity columns andfossil levels for DNZW, WFKW, and BTW localities scaled directly from illustrations in original source: Lindsay et al.(1981), thus differ slightly from figure 9 of Williamson (1996). Fossil levels in GC and EFKW columns from William-son (1996). Stratigraphic levels of Torrejonian mammals in MDC column from Simpson (1959, figure 1). Base ofC29n not determined at BTW locality but projected to just above base of Ojo Alamo Sandstone. Top of C29n notdetermined at MDC locality but interpolated based on estimated rates of deposition for lower part of Nacimiento For-mation. Boundary between Puercan and Torrejonian mammals (black dashed line) is placed between lowest Torrejo-nian fossil at MDC locality and highest Puercan fossil at GC locality. Boundary is estimated to be about 64.4 Mabecause it is near top of magnetochron C29n. Column localities are shown on Figure 3.

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(1996, figure 9), however, showed these faunal lev-els much lower in the Nacimiento at about 5 m and30 m above the base of the exposure. In addition,whereas Simpson showed the two Torrejonian fau-nal zones to be about 22 m apart, stratigraphically,Williamson showed them to be 26 m apart. Appar-ently, Williamson (1996) misplaced these faunalzones because of a miscorrelation of the “persis-tent lignite” of Simpson (Figure 43). Because Simp-son is the original source for the stratigraphic levelsof the two Torrejonian faunal zones at Mesa deCuba, his measurements at that locality are used inthis report.

The Puercan-Torrejonian boundary can thusbe placed fairly precisely in the lower part of theNacimiento Formation (Figure 42) between thelowest Torrejonian mammal level at the MDC local-ity and the highest Puercan mammal level at theGC locality. The age of this boundary is estimatedto be about 64.4 Ma because it is near the top ofchron C29n which has an age of 64.432 Ma (Grad-stein et al. 2004). Thus, the Puercan in the SanJuan Basin has a duration of about 1.1 m.y., rang-ing from the base of the Paleocene at 65.5 Ma tothe Puercan-Torrejonian boundary at 64.4 Ma (Fig-ure 42). The Torrejonian mammals identified in the

PERSISTENT LIGNITE

0

40 m

62 m

56 m

50

100

150

Meters

MAINLYCROSSBEDDED SANDSTONENOT MEASURED BASAL SAN JOSE FORMATION

MAINLY GREENISH TOYELLOWISH BANDED CLAYS,SOME SOMBER BEDS,INTERMITTENT LENTICULARSANDSTONES

DISCONFORMITY

(219)

CA 350’

INTERMITTENT BUTFREQUENT SANDSTONELENSES TO 20’

GREENISH ANDSOMBER CLAYSAND SILTS 70’

HEAVY, LENTICULAR PALESANDSTONE, IN SOMBERCLAYS 50-75’

GREENISH GRAY SILTSAND SOMBER CLAYS 65’

BASE OF EXPOSURE

OJO ALAMO SANDSTONE

APPROXIMATE TOP OF OJO ALAMO

VERTICAL SCALE(NO HORIZONTALSCALE)

NACIMIENTOFORMATION

222, 226 229

230

0’

50’

100’

Figure 43. Stratigraphic section at Mesa de Cuba locality modified from Simpson (1959). Metric scale on left andarrows and distances above base of section to Torrejonian fossil zones and Simpson’s “persistent lignite” have beenadded. Numbers 230 and 222, 226, and 229 represent Simpson’s Torrejonian mammal-fossil levels at Mesa de Cubaprojected into section from nearby locations.

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lower part of the Nacimiento Formation in the fivesections all appear to fall within magnetochronC28n. The lower of the two Torrejonian fossil locali-ties at the MDC site, however, appears to be inchron C28r or the uppermost part of chron C29n(Figure 42). A paleomagnetic survey of theNacimiento Formation at Mesa de Cuba wouldsupply a valuable data set to clarify these interpre-tations.

The level of the interpolated top of magneto-chron C29n at the MDC locality is higher than thetop of this chron at the DNZW, WFKW, and BTWlocalities (Figure 42). This anomaly must be theresult of different rates of deposition for the lowerNacimiento Formation at these widely separatedlocalities. (The apparent rate of deposition for thepart of the lowermost Nacimiento within chronC29n is estimated to be 102 m/m.y. at the DNZWlocality vs. 143 m/m.y. at the MDC locality.) ChronC28r is anomalously thin at the BTW locality andLindsay et al. (1981, p. 417) suggested that thisthinness is the result of present-day-normal over-printing of the lower part of normal interval C28ndue to weathering beneath recent sand dunes atthe BTW locality. Additional paleomagnetic studiesare clearly needed in the BTW area to help clarifythis paleomangnetic pattern.

Clemens and Williamson (2005) discussedthe Puercan fauna at the Betonnie Tsosie Wash(BTW) locality (Figures 11 and 42). They named anew species, Eoconodon ginibitohia, based on afragment of a left dentary collected at the lower-most level for Puercan mammal fossils at thatlocality (Figure 42). These authors asserted thatbased on correlations of this taxon with otherEoconodon species in the northern part of theWestern Interior, it, and the other mammals foundin the “Ectoconus zone” of the southern San JuanBasin, belong in the “Pu2 Interval Zone” (middlepart of the Puercan). They further stated that (p.208): “Earliest Paleocene, Pu1 Interval Zone fau-nas are unknown in the San Juan Basin.” It is heresuggested that part of the missing lower “PuercanPu1 Zone” in the San Juan Basin may be repre-sented by the Paleocene Ojo Alamo Sandstonemammals, discussed above. And, as discussedelsewhere in this report, as much as 300 k.y. ofearliest Paleocene time apparently is not repre-sented by rock strata in the San Juan Basin, thusat least the lowermost part of the “Pu1 IntervalZone” is missing for that reason.

Clemens and Williamson (2005, p 209) placedthe Ectoconus zone fauna in the lower part of mag-netochron C29n in the San Juan Basin. However,

as Figure 42 shows, Ectoconus-zone mammalsare present throughout the upper half of chronC29n at the four localities where it has been foundin the lowermost part of the Nacimiento Formation.The presence of the middle Puercan Pu2 IntervalZone (“Ectoconus zone”) in the lowermostNacimiento Formation at the DNW locality (within 5or 10 m of the top of the Ojo Alamo Sandstone;Lindsay et al. 1981 and Williamson 1996, respec-tively) suggests that the upper part of the “Pu1Interval Zone” may be within the Ojo Alamo Sand-stone providing additional strong evidence for con-tinuous deposition across the Ojo Alamo-Nacimiento contact and in agreement with thePaleocene age of the Ojo Alamo Sandstone.

GEOCHEMISTRY OFVERTEBRATE BONE SAMPLES

Original (2002) Study

Fassett et al. (2002) presented chemical anal-yses of 18 vertebrate-bone samples; nine from theCretaceous Kirtland Formation and nine from thePaleocene Ojo Alamo Sandstone. Two Kirtlandsamples were turtle bones; the other 16 sampleswere dinosaur bones. The Fassett et al. (2002)study showed that there are distinct differences inthe amounts of uranium (U), the sums of the rare-earth elements (REE), and the chondrite-normal-ized lanthanum/ytterbium ratios (La/Yb(n)) inPaleocene Ojo Alamo Sandstone bone samplescompared to Cretaceous Kirtland Formation bonesamples. Uranium abundances exhibited the larg-est differences between the two suites of samples.The mean value for U in Ojo Alamo bone samples(447 ppm) was found to be 18 times greater thanthe mean for Kirtland bone samples. REE exhibitedless striking, albeit consistent differences. Themean sum of REE was 1,587 for the Ojo Alamoand 3,196 for the Kirtland. The mean La/Yb(n) ratiofor Ojo Alamo samples was 6.2 whereas for theKirtland samples, the mean was 16.1. In summary,the Fassett et al. (2002) study showed that ura-nium is greatly enriched in Ojo Alamo bone sam-ples relative to Kirtland samples whereas REE aremore abundant and relative abundances of REEare more fractionated in Kirtland bone samples.

New Samples

Sample Descriptions. Ten of 14 new sampleswere collected by the author from newly discov-ered dinosaur-bone localities. The other four dino-saur bone samples were provided by R. B. Sullivan(The State Museum of Pennsylvania) and by S.G.

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Lucas (New Mexico Museum of Natural Historyand Science), as discussed below and noted onTable 2 (see Table Appendix, page 113). One of thesamples provided by Lucas was from a hadrosaurscapula that was one of 34 bones in the boneassemblage of Hunt and Lucas (1991; and see Fig-ure 38). This sample is number P-19147 (Tables 2,3 (see Table Appendix, page 114)) collected fromlocality I of Figure 4. The stratigraphic level of the34-bone assemblage was measured in the field bythe author in 2003 and found to be 6.1 m above thebase of the Ojo Alamo. A small lag deposit of verte-brate bone was discovered near this locality 4.6 mabove the base of the Ojo Alamo Sandstone and adinosaur bone fragment from that deposit was col-lected and analyzed (sample number 020103 ofTables 2, 3; locality H of Figure 4). Sample number35957-LUC (Tables 2, 3) was from a large sauro-pod femur (Alamosaurus sanjuanensis) 4.6 mabove the base of the Ojo Alamo at locality D, fig-ure 11. This bone was collected by Lucas who pro-vided a small sample for chemical analysis; Lucasstated (personal commun., 2004) that this bone“was much too massive and pristine to have beenreworked from older strata.”

Sample SMP VP-1625 was from a large A.sanjuanensis femur (Figure 37.2) collected by R.B.Sullivan who provided a small fragment for chemi-cal analysis. This specimen came from locality O ofFigure 4. The author determined that this localitywas 4.9 m above the base of the Ojo Alamo;numerous other dinosaur bones in the Ojo Alamowere observed in the same area, including thefragmented bone shown on figure 37.3. Samplenumber 051504, a fragment of ceratopsian frillbone (locality N, Figure 4) was found in the samearea 3.7 m above the base of the Ojo Alamo. Sam-ple SMP VP-1494 was from a sauropod vertebracollected by Sullivan from locality G of Figure 4.

Two samples were collected from a lagdeposit of abraded vertebrate-bone fragmentsfound on the surface of the Kirtland Formationnearly 11 m below the base of the Ojo Alamo(locality C, Figure 4). At the time of collection, itwas not known if these bone fragments had weath-ered out of the Kirtland Formation or had washeddown from a higher level. The two samples ana-lyzed from this assemblage were a fragment of tur-tle shell and a fragment of dinosaur bone. Thesesamples were collected primarily to determine ifthere were significant differences between thechemistry of dinosaur bone and turtle shell.New-Sample Analyses. The new set of 14 sam-ples was prepared by R.A. Zielinski (USGS, Den-

ver, Colorado) and analyzed by instrumentalneutron activation by J.R. Budahn (USGS, Denver,Colorado) using the same procedures described inFassett et al. (2002). The samples were taken, tothe extent possible, from the outermost (cortical)surface of the bones. The chemical analyses ofthese new vertebrate bone samples (six from theOjo Alamo Sandstone, six from the Kirtland Forma-tion, and two provenance uncertain) are shown onTable 3 (see Table Appendix, page 114). Thesesamples yielded elemental concentrations similarto the original 18 samples discussed above: OjoAlamo samples contained high levels of U and rel-atively low levels of REE; Kirtland samples con-tained low levels of U and relatively high levels ofREE. Table 2 shows the concentrations of U andREE for all 32 bone samples (old and new); Figure44 is a plot of the La/Yb(n) vs. U values for all sam-ples.

As Tables 2 and 3 and Figure 44 indicate, thesmall fragments of dinosaur bone (020203-B) andturtle shell (020203-T) collected from an erosionsurface on the Kirtland Formation exhibit similarchemistry. Despite their stratigraphic position,these two samples were more like Ojo Alamo bonewith somewhat high U and quite low La/Yb(n). Onthe other hand, these samples resembled Kirtlandsamples with very high values for their sums ofREE (Tables 2, 3). Based on their overall chemis-try, it might be inferred that these samples weath-ered out of the Ojo Alamo Sandstone and washeddown on top of the Kirtland erosion surface wherethey were found. Because of the uncertain prove-nance of these samples, they are not included inthe comparison of Cretaceous and Tertiary bonechemistry.

The fragmented dinosaur limb bone fromwhich sample 110803-B was obtained was at thecontact of the Kirtland Formation and the OjoAlamo Sandstone at the Pot Mesa locality(Figures1, 3). The sample was a fragment of aspecimen that had been collected by S.G. Lucas in1983 designated UNM-TOA-2. This specimen isdiscussed and illustrated in a photograph in Fas-sett et al. (1987, figure 11). (The stratigraphy of theKirtland Formation and Ojo Alamo Sandstone inthis area was discussed and the formation bound-ary between these rock units redefined in Fassettet al. 2002). This badly fragmented bone was origi-nally thought to be in the lowermost Ojo AlamoSandstone (Fassett et al. 1987, p. 29, figure 11;Fassett et al. 2002, p. 324, figure 17). Table 3shows this bone to have a relatively low concentra-tion of uranium and a relatively high sum of REE;

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chemical characteristics of a Cretaceous (KirtlandFormation) dinosaur bone. This bone was near thepre-Ojo-Alamo-Sandstone erosion surface whenthe Ojo Alamo was deposited on top of it. Despiteits proximity to the overlying Ojo Alamo, this bone(labeled PM on Figure 44) has retained chemicalcharacteristics of a Cretaceous bone sample;strong evidence that the U and REE concentra-tions were not appreciably modified when this bonewas immersed in mineralizing fluids with a differentchemistry nearly 8 m.y. later in Paleocene time.

The Figure 44 plot of La/Yb(n) vs. U for all ofthe bone samples analyzed for this study showsthe significantly higher U content for Ojo Alamosamples vs. Kirtland samples. (Samples (020203-B, and 020203-T) found loose on the surface of theKirtland Formation are shown in green.) The meanU content for all 15 Ojo Alamo samples is 422 ppm

vs. 20 ppm for 15 Kirtland samples (Table 2); morethan 20 times greater. The single anomalous Uvalue of 33 ppm is from the large hadrosaur femurcollected at the San Juan River locality (Figure 1).As Figure 44 shows, the U value for this sampleFBHF on this figure overlaps U values for KirtlandFormation bone samples. This was the most north-erly of the Ojo Alamo bone samples and is also thestratigraphically highest 15.2 m above the base ofthe formation. The northern setting could haveaffected this sample’s anomalously low U content.Uranium mineralization has been documented inthe Ojo Alamo Sandstone in the southeast part ofthe San Juan Basin at Mesa Portales (Fassett etal. 2002, p. 330) close to possible granitic sourcerocks in the incipient Nacimiento Mountains. Per-haps the U content of mineralizing fluids was lessin the northern part of the San Juan Basin, farther

0

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PM

Figure 44. Plot of chondrite-normalized lanthanum/ytterbium ratios [La/Yb(n)] vs. uranium abundances (U ppm) forfossil bone samples from Ojo Alamo Sandstone and Kirtland Formation. Sample localities shown on Figures 1, 4,and 11. Elemental abundances on Tables 2 and 3. PM is bone sample from Pot Mesa, FBHF is bone sample fromSan Juan River locality.

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from that possible source area, in Ojo Alamo time.One sample, however, provides insufficient data formore than speculation regarding this sample’s lowU content. The chemical analyses of dinosaurbones from the Animas Formation (when they arefound) in the northern part of the San Juan Basinwill provide a test of this hypothesis.

Except for the FBHF bone sample from theSan Juan River site, the range of U concentrationswithin Ojo Alamo samples is 89 to 834 ppm. Instark contrast, U values for Kirtland samples rangefrom 2 to 45 ppm (Table 4). Large variations in Uconcentrations within each of these bone popula-tions may have resulted from: 1) variations in dis-solved U concentrations in mineralizing fluids, 2)variations in host lithologies affecting permeabili-ties and thus volumes of mineralizing fluids thebones were exposed to, and 3) the progress ofbone mineralization that influenced the accessibil-ity of U-bearing ground water during fossilization.

Analytical data indicate generally higher sumsof REE in Kirtland Formation bones relative to OjoAlamo Sandstone bones (Tables 2, 4). Three OjoAlamo bone samples and one Kirtland sample con-tained particularly low “Sum REE” values (< 73ppm, Table 2). These low abundances of REE mayindicate samplings of bone further from the bone’scortical (outer) surface. When comparing samplesfrom the outer surface with deeper-bone levelsfrom 70 mm long cores within samples (051298-BB1 and FBHF), the sum of REE concentrations indeeper bone was lower by factors of 2-100,whereas uranium concentrations decreased onlyby factors < 2 ( Zielinski personal commun., 2007.)and Fassett et al. (2002, p. 329). Preferential con-centration of REE in outermost layers is unex-plained, but may indicate enhanced uptake of REErelated to early diagenetic alteration or recrystalli-zation of outermost fossilized bone. Such uptake isapparently more pronounced in Kirtland bones andmust be of limited duration in order to preserve the

apparent differences in REE patterns in the twosuites of bones.

Figure 45 shows chondrite-normalized rareearth element patterns for the 21 vertebrate-bonesamples that contained the greatest concentrationsof REE. The newly analyzed samples (dashedlines) show the same subsets of patterns as thesamples (solid lines) previously reported in Fassettet al. (2002); that is, more steeply sloped patternsfor Kirtland Formation bones and flatter slopes forOjo Alamo Sandstone bones. The steeper slope ofREE patterns in Kirtland samples is primarilycaused by a greater abundance of light REE (La,Ce, Nd). Steeper-sloped patterns are representedin the tables as a higher ratio of La/Yb(n).

The data plot for sample 110803-B in Figure45.2 (Kirtland samples) is plotted in a differentcolor because the slope for this sample is anoma-lous: it is noticeably flatter than the other Kirtland-sample plots and is more like an Ojo Alamo REEsample plot. As discussed above, sample 110803-B was collected less than 0.1 m below the Kirtland-Ojo Alamo contact and was originally thought to befrom the Ojo Alamo Sandstone. Based on its verylow U content (30 ppm) and relatively high SumREE of 2705 (Table 2) this bone has a Kirtlandgeochemical signature. The anomalously flat slopeof the REE plot for this bone (Figure 45.2) may bethe result of its proximity to the Kirtland-Ojo Alamocontact that may have allowed for some slightalteration in REE content by Paleocene mineraliz-ing fluids. If so, those fluids did not change theoverall Kirtland chemical signature for this bone oflow U and high REE (Figure 44). These data sup-port the thesis that the U content of bone samplesis fixed at the time of initial mineralization and is notsubject to significant change by being immersed inmineralizing-fluids with different chemistry at a latertime.

Sample 072598-6C also has a flatter slope onFigure 45 than other Kirtland bone samples andthe reasons for this anomaly are unknown. This

TABLE 4. Summary statistics for chemical parameters distinguishing Kirtland Formation bones from Ojo AlamoSandstone bones.

Note: n = chondrite-normalized abundance.

Ojo Alamo Sandstone (15 samples) Kirtland Formation (15 samples)Chemical parameter Min. Max. Median Mean

Standard deviation Min. Max. Median Mean

Standard deviation

U 33 834 436 447 298 2 45 25 24 16

Lan/Ybn 2 14 5 6 4 4 27 17 16 8

Sum REE 38 6174 1004 1587 1883 66 5626 2865 3196 2000

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69

070498-8C

090498-8Y 110803-A

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45.1 - Ojo Alamo Sandstone Bone Samples

Figure 45. Chondrite normalized rare-earth-element patterns of fossil bone samples, 45.1 Ojo Alamo Sandstone,45.2 Kirtland Formation, San Juan Basin, New Mexico. Values used in normalization: La = 0.311, Ce = 0.813, Nd =0.603, Sm = 0.196, Eu = .074, Gd = 0.26, Tb = 0.047, Ho = 0.0718, Tm = .0326, Yb = 0.21 and Lu = 0.0323, derivedfrom multiplying 1.32 times C1 values of Anders and Grevesse (1989) to correct to a volatile-free basis. Samplelocalities shown on Figures 1, 4, and 11. Specimen numbers keyed to Tables 2 and 3. Dashed lines show patterns fornew samples; solid lines show patterns for samples from Fassett et al. (2002). REE patterns for samples 110803-B(purple) and 072598-6C (green) are anomalous, as discussed in text. Colors are used to improve readability and tobroadly subdivide samples according to total REE content.


turtle-bone sample has a low U content (38 ppm)and very high Sum REE (Figure 2) clearly estab-lishing it as a Kirtland bone sample.

Significance of Vertebrate-Fossil Geochemistry

The REE composition of fossil bone has beenused to determine stratigraphic provenance and toidentify reworked bone in the Triassic of southwestEngland (Trueman and Benton 1997) and in thePleistocene in southern Kenya (Trueman et al.2006). In this study, differences in REE and U con-tents between two suites of dinosaur bones (table2) are preserved, despite their close stratigraphicproximity, and despite their largely shared post-Cretaceous alteration history (Table 4). These datastrongly suggest that the chemically distinct OjoAlamo Sandstone dinosaur bones were fossilizedin place during Ojo Alamo Sandstone (Paleocene)time and thus cannot be Cretaceous bonesreworked from the underlying Kirtland Formation.These facts, coupled with independent documenta-tion of the Paleocene age of the Ojo Alamo Sand-stone presented elsewhere in this paper, indicatethat some dinosaurs lived, died, and were pre-served in earliest Paleocene time in the San JuanBasin area.

AGE OF OJO ALAMO SANDSTONE BASED ON ALAMOSAURUS SANJUANENSIS

Sullivan, Boere, and Lucas (2005, p. 580)stated that the age of the sauropod dinosaur A.sanjuanensis is precisely 69 Ma throughout theWestern Interior of North America, including theSan Juan Basin. They stated that this finding wasbased on an abstract by McDowell et al. (2004)that reported a U/Pb age of 69 ± 1.0 Ma for a tuffbed found in about the middle of the Javelina For-mation in the Big Bend area of Texas. This asser-tion that Alamosaurus is exactly 69 Ma (near theCampanian-Maastrichtian boundary) represents aserious challenge to the findings in this report thatthe Ojo Alamo Sandstone is Paleocene in agebecause Alamosaurus fossils are found at severallocalities within the Ojo Alamo in the San JuanBasin. Because the McDowell et al. (2004) abstractis cited by Sullivan, Boere, and Lucas (2005, p.580), as the basis for their claim that Alamosaurusis 69 Ma, a careful evaluation of this abstract is crit-ical to an assessment of their claim.

McDowell et al. (2004) stated that Maastrich-tian vertebrates from the Western Interior occurredin two faunal provinces: the Triceratops fauna inthe north and the Alamosaurus fauna in the south.It is thus clear that they were stating that these two

faunas are the same age: Maastrichtian, or latestCretaceous. These authors go on to say that theirdated tuff bed is from the middle of the JavelinaFormation and that:

This position is within the local range of the sauropod Alamosaurus, below two sites that have yielded remains of the pterosaur Quetzalcoatlus, and above a site with petrified logs of the dicot tree Javelinoxylon. The range zones of all three taxa span the full thickness of the Javelina Formation elsewhere in the Big Bend region. The Alamosaurus Fauna is therefore Lancian to late Edmontonian in age. [My emphasis]It is thus clear that Sullivan, Boere, and Lucas

(2005) misinterpreted the McDowell et al. abstractwhen they concluded that it found that the 69 Matuff bed represented the exact age of A. sanjuan-ensis.

Sullivan, Boere, and Lucas (2005, p. 580)continued their discussion by stating that A. san-juanensis has been reported to have a long range—from late Campanian to late Maastrichtian—undermining its value as an index fossil. Followingthis accurate statement, these authors proceededto present arguments purporting to show that A.sanjuanensis in the North Horn Formation does notreally range to upper Maastrichtian but is “pre-lateMaastrichtian”. These arguments are unconvincingbecause they contradict a large body of data sup-porting a late-Maastrichtian age for the A. sanjuan-ensis-bearing part of the North Horn Formation(Cifelli et al. 1999, Difley and Ekdale 1999).

In Sullivan, Lucas, and Braman (2005), theconclusions of the Sullivan, Boere, and Lucas(2005) report, regarding the 69 Ma age of A. san-juanensis, were extended with the creation of the“Alamosaurus datum” (p. 401 and figure 7); theseauthors claim that this datum can be used to datethe Alamosaurus level precisely at 69 Ma through-out the Western Interior including within the NorthHorn Formation of southeast Utah, the lower partof the Ojo Alamo Sandstone in the San JuanBasin, and the Javelina Formation in the Big Bendarea.

Lehman et al. (2006) discussed the relationsof the 69 Ma tuff bed in the Javelina Formation andtheir “Alamosaurus vertebrate fauna.. Theseauthors stated (p. 922) that one of the reasons forpublishing their paper was to clarify “misinterpreta-tions” of the McDowell et al. (2004) abstract byrecent authors, including Sullivan, Boere, and

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71

Tuff-bed sample locality

Alamosaurus

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118

Big BendNational Park

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Paleocene vertebrates

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LEGEND

ceratopsid indet.paleosols

Aluvial flood-plain deposits

Alluvial channel deposits

Javelinoxylon

BLA

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Figure 46. Stratigraphic column showing Cretaceous-Tertiary strata and stratigraphic levels of key fossils in Big Bend,Texas area, modified from Lehman et al. (2006). Red color of some items has been added for emphasis.


Lucas (2005). The stratigraphic relations of thedated tuff bed and the principal fossil levels in theJavelina and overlying Black Peaks Formation areshown on figure 1 of Lehman et al. (2006), which isreproduced herein in modified form as Figure 46.The levels of collection sites of Alamosaurus andother upper Cretaceous index fossils are shown;Alamosaurus is shown to span the interval fromjust below the 69 Ma tuff bed to just below the K-Tboundary. The K-T boundary of Figure 46 is shownto be tightly bracketed by Alamosaurus just belowand “Paleocene vertebrates” just above.

Lehman et al. (2006, p. 925) discussed therange of Alamosaurus and stated:

Hence, introduction of the Alamosaurus fauna in southern North America must have occurred sometime after about 73 Ma but before 69 Ma, and so probably not coincident with the Edmontonian-Lancian faunal transition observed in northern locales. Furthermore, although it seems likely that the Alamosaurus fauna persisted to the end of Cretaceous time (ca. 65 Ma), this has yet to be demonstrated conclusively. Some evidence suggests that the Alamosaurus fauna may have persisted into Paleocene time (Fassett et al. 2002).The work of Lehman et al. (2006) thus contra-

dicts the assertion of Sullivan, Boere, and Lucas(2005) and Sullivan, Lucas, and Braman (2005)that there is an “Alamosaurus datum” with a pre-cise age of 69 Ma in the Big Bend area of Texas.Because the presence of Alamosaurus in the lowerpart of the Ojo Alamo Sandstone does not pre-cisely date the base of the Ojo Alamo at 69 Ma, assuggested by Sullivan, Lucan, and Braman (2005),the presence of this dinosaur in the Ojo Alamo inno way refutes the Paleocene age of this forma-tion.

CONCLUSIONS

This report presents new paleomagnetic andpalynologic data that confirm the Paleocene age ofthe Ojo Alamo Sandstone and its contained dino-saurs in the San Juan Basin as reported in Fassettand Lucas (2000) and Fassett et al. (2002). Inaddition, chemical analyses of new dinosaur bonesamples from the Cretaceous Kirtland Formationand Paleocene Ojo Alamo Sandstone expand theexisting geochemical data base for such samplesin the basin and confirm the findings in Fassett etal. (2002) that the dinosaur bone present in the Ojo

Alamo has not been reworked. Challenges to thePaleocene age of the Ojo Alamo by Sullivan,Lucas, and Braman (2005), when carefully ana-lyzed, have been found to be unsupported by data.

Fassett et al. (2002) estimated that dinosaurspersisted into early Paleocene time for about 1 m.y.That estimate was based on the assumption thatan 11 m thick paleomagnetic-normal interval in theOjo Alamo Sandstone represented the entire C29nmagnetochron. This report (as discussed in the“Paleomagnetism” section) extends the top of mag-netochron C29n to well above the top of the OjoAlamo Sandstone and into the lower part of theNacimiento Formation (Figure 42). The 11 m thickmagnetic-normal interval within the Ojo AlamoSandstone is now interpreted to be only the lower-most part of chron C29n and is designatedC29n.2n herein. Figure 42 shows that C29n is nowknown to range from about 68 to 98 m thick.

This increase in the length of magnetochronC29n required a revised estimate of how long dino-saurs lived in the Paleocene in the San JuanBasin. Dinosaur bone has been found to be 8.2 mabove the base of the Ojo Alamo in the southernSan Juan Basin (Table 2 and Figure 5) near theBarnum Brown Amphitheater locality (locality J ofFigure 4). At that locality, the base of chron C29n isclose to the base of the Ojo Alamo Sandstone. Thebase of C29n has an age of 65.118 Ma (Gradsteinet al. 2004), thus the age of the youngest Paleo-cene dinosaur fossil that can be linked directly topaleomagnetic data is now estimated to be about65 Ma. The stratigraphically highest, in-place dino-saur fossil in the entire basin was found at the SanJuan River locality (Figures 1.1, 34), 15.2 m abovethe base of the formation, however, with no geo-chronologic data available at that place to quantifythe time represented by this stratigraphic interval, itis not possible to say if this bone is younger thanthe youngest dinosaur bones in the southern partof the basin. Additional paleomagnetic studies ofthe Ojo Alamo Sandstone at this locality could helpresolve this problem.

ACKNOWLEDGEMENTS

The preparation of this paper benefited fromvigorous discussions with S.G. Lucas (New MexicoMuseum of Natural History and Science, Albuquer-que) and R.B. Sullivan (The State Museum ofPennsylvania, Harrisburg) over several decades.These colleagues generously provided dinosaurbone samples for chemical analyses, identifieddinosaur fossils, provided copies of their and otherpublications, and have been invaluable sources of

72


information about vertebrate paleontology. Lucasgraciously agreed to be one of the USGS review-ers of the manuscript, and his review is appreci-ated. T.E. Williamson (New Mexico Museum ofNatural History and Science), New Mexico, pro-vided help with information and publications relatedto fossil-mammal collection localities in the OjoAlamo Sandstone in the San Juan Basin. William-son also reviewed the Vertebrate Paleontologysection of this report, and his comments helped toimprove that section. K. Johnson (Denver Museumof Nature and Science) reviewed the paleobotanystudies of Knowlton (1924) and found them to bestill valid.

U. S. Geological Survey (USGS) colleagues,F. Peterson and R.B. O’Sullivan, at the DenverFederal Center, Colorado, provided invaluableassistance in researching publications in the USGSDenver Federal Center library that were critical forthis report. Peterson spent hours in the USGSfield-notebook archives searching for references todinosaur bones in the Animas Formation and suc-ceeded in locating the field-note reference to anAnimas dinosaur by J.H. Gardner, reproduced onFigure 40 of this report. Peterson, R. Keefer, andE.M. Brouwers (USGS Denver) conducted techni-cal edits of the manuscript and greatly improvedthe final product. USGS colleagues R.A. Zielinskiand J.R. Budahn performed the chemical analysesof the additional suite of 14 vertebrate-bone sam-ples included in this study. Zielinski’s constructivecomments regarding the structure of this reportand his careful review of the “Geochemistry of Ver-tebrate Bone Samples” section of the reportimproved it greatly. R.H. Tschudy (1908-1986) andD. J. Nichols, USGS palynologists, analyzed manyrock samples for the author over many decadesand a large part of the palynologic data base pre-sented in this report is based on their work. Nicholsalso reviewed the palynology sections of thisreport, and his suggestions were extremely helpful.USGS palynologist N. Frederiksen deserves spe-cial recognition for being the first palynologist toidentify Paleocene palynomorphs in Ojo AlamoSandstone samples at the important San JuanRiver locality.

M.,B. Steiner at the University of Wyoming inLaramie, provided the paleomagnetic data plot forthe Mesa Portales section that has proven to be apivotal data set for confirming the Paleocene ageof the Ojo Alamo Sandstone in the San JuanBasin. E.M. Shoemaker was responsible for initiat-ing the Mesa Portales paleomagnetic study andpersonally cored most of the rock samples there in

an intensive week of field work in 1984, assisted bySteiner and the author. Shoemaker’s encourage-ment and perceptive comments about the Creta-ceous-Tertiary interface problem in the San JuanBasin over the years were a constant and joyfulstimulus to the author in the pursuit of more andbetter data to help resolve this problem. K. Zeigler,Department of Earth and Planetary Sciences, Uni-versity of New Mexico, reviewed the paleomag-netism section of this paper and offered insightfulsuggestions that greatly improved this section.

Two anonymous reviewers for PalaeontologiaElectronica reviewed the manuscript and providedvaluable suggestions for improving the paper. C.N.Trueman reviewed the geochemistry section of themanuscript for Palaeontologia Electronica, and hiscomments and suggestions improved the clarity ofthat section. For permission to use figures andtables, I thank the following journals and institu-tions: form figures from Butler and Lindsay (1985)the Journal of Geology, for figures from Lindsay etal. (1981) the American Journal of Science, for useof table 3 of Flynn (1986) and figures of Simpson(1959) The American Museum of Natural History,for use of figures from Lehman (2006) The Societyof Vertebrate Paleontology.

The initial study of the paleomagnetism, radio-metric ages, palynology, and vertebrate paleontol-ogy of the rock strata adjacent to the Cretaceous-Tertiary interface in the San Juan Basin wasfunded by a USGS Gilbert Fellowship grantawarded to the author in 1987. Those first studiesprovided the foundation for the geochronologicwork that has continued since then by the authorand the colleagues mentioned above. BradleyScholar grants by the USGS in 2007 and 2008helped defray some of the expenses incurred forthe review and publication of this report.

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APPENDIXSYNTHESIS OF PUBLISHED AND UNPUBLISHED PALYNOLOGIC DATA FOR CRETACEOUS-

TERTIARY BOUNDARY STRATA; SAN JUAN BASIN, NEW MEXICO

INTRODUCTION

Palynology has been the most precise bio-chronologic tool for locating the stratigraphic posi-tion of the Cretaceous-Tertiary (K-T) boundary inthe Western Interior of North America. In the RatonBasin, 230 km east of the San Juan Basin, the K-Tboundary was located to within a few centimeterson the basis of the last occurrence of the Creta-ceous index palynomorph Tschudypollis (formerlynamed Proteacidites). The end-Cretaceous aster-oid-impact fall-out layer was subsequently discov-ered within that same centimeters-thick interval byOrth et al. (1981, 1982). The K-T fall-out layer hasnow been found at numerous localities throughoutthe Western Interior of North America just abovethe last occurrence of Tschudypollis and (or) otherCretaceous index palynomorphs, validating thevalue of these index fossils for determining the pre-cise location of the K-T interface. Nichols andJohnson (2002, p. 100) stated that:

In southwestern North Dakota, as elsewhere in the Western Interior region of the United States and Canada, the K-T boundary is defined by the disappearance (local or total extinction) of certain palynomorph taxa. . . . In this study, the K-T boundary was determined on the basis of palynology to be between the highest sample that yielded K taxa [Cretaceous index palynomorphs] and the next sample above that lacks K taxa.One of the key “K taxa” listed by Nichols and

Johnson (2002) was Tschudypollis. In the followingdiscussion, it is shown that the last occurrence ofthe Cretaceous index palynomorph Tschudypollisprecisely locates the stratigraphic level of the K-Tinterface at the base of the Ojo Alamo Sandstoneat several localities in the San Juan Basin. At a fewlocalities, rare specimens of Tschudypollis havebeen identified from Ojo Alamo Sandstone rocksamples. Nichols and Fleming (2002, p. 240) dis-cussed the reworking of palynomorphs from olderstrata into younger strata and concluded that “Theage of a contaminated [palynomorph] assemblage

is determined by the youngest species present,one that has a restricted stratigraphic range, anddoes not occur in older rocks.” In every instancewhere rare Tschudypollis specimens have beenfound in Ojo Alamo Sandstone samples, theyounger Paleocene guide fossil Momipites tenuipo-lus is also present. M. tenuipolus is a known Paleo-cene guide fossil in the Western Interior of NorthAmerica (Nichols and Johnson 2002) and hasnever been found in Cretaceous strata in thesouthern part of the Western Interior, thus the pres-ence of this palynomorph in the Ojo Alamo Sand-stone confirms the Paleocene age of these“contaminated” assemblages.

Obtaining outcrop rock samples productive ofpalynomorphs has been a difficult challenge in theSan Juan Basin. Commonly, samples that lookedpromising in the field that is, with evidence ofabundant organic material in them proved barren,when analyzed. For that reason, palynologic sam-pling from Mesa Portales, the Ojo Alamo Sand-stone type area, and other localities (discussedbelow), has been spaced out over decades. Forevery set of samples collected, more than half, typ-ically, turned out to be barren of palynomorphs, sorecollecting was necessary to try to find productivematerial to fill in gaps. This problem has beenespecially acute in the Ojo Alamo type area (Figure4), where abundant dinosaur bone is present in thelower part of the Ojo Alamo Sandstone. Numerousattempts to obtain rock samples productive ofpalynomorphs from dinosaur-bearing strata withinthe Ojo Alamo Sandstone in the type area, by vari-ous workers (including the author), have still notsucceeded. Productive samples yielding diversepalynomorph assemblages from dinosaur-bearingstrata would contribute greatly to the biochrono-logic data-base for the Ojo Alamo Sandstone in thesouthern San Juan Basin.

Good results, however, have been relativelyrecently obtained at the San Juan River site, wheremultiple palynomorph-productive samples wereobtained a few meters below a large hadrosaurfemur in the Ojo Alamo Sandstone (Fassett andLucas 2000) and at the Barrel Spring locality where

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the Paleocene index palynomorph Momipites tenu-ipolus was identified from samples just below thebase of the dinosaur-bearing Ojo Alamo Sand-stone (Fassett et al. 2002). Excellent results havealso been obtained from Cretaceous-Tertiary (K-T)strata at Mesa Portales where multiple, productive,palynologic sample sites closely bracket the Creta-ceous-Tertiary interface. Even though studies ofthe palynology of the Ojo Alamo Sandstone andadjacent strata have been conducted at numerouslocalities, no synthesis of all available data hasbeen published heretofore.

The aim of this appendix is to present, chrono-logically, all available published and unpublishedpalynologic data for rock strata adjacent to the K-Tinterface in the San Juan Basin.

Anderson (1960)

Anderson (1960) was the first to publishpalynologic data for strata adjacent to the Creta-ceous-Tertiary boundary in the San Juan Basin. In

his introduction, he summarized the conflictingpaleontologic data relating to the age of the OjoAlamo Sandstone in the southern San Juan Basin:paleobotanical data indicated that the Ojo Alamowas Paleocene and abundant dinosaur fossils indi-cated that this formation was Cretaceous. Ander-son wrote (p. 1): “One objective of this study is todetermine what bearing the pollen and spore evi-dence has on the controversy.” Anderson (1960)collected rock samples from the Ojo Alamo Sand-stone and adjacent strata at five localities in thesoutheastern part of the basin near Cuba, NewMexico (Figure 21): the Kirtland Shale, Ojo Alamo1 and 2, and Nacimiento 1 and 2 localities. (Ander-son’s palynomorph lists from these localities are inTable 5 (see Table Appendix, page 118).)

Figure 47 is a composite stratigraphic diagramshowing the relative stratigraphic positions ofAnderson’s Kirtland and Ojo Alamo sample sites.The sample locality for the “Kirtland shale florule” isin a badland amphitheater where the upper part of

meters

0

5

10

15

20

25

30

Kirtland shale florule

Ojo Alamo 2 florule

Ojo Alamo 1 florule

FRUITLAND FORMATION

upper sandstone bench

lower sandstone bench

middle shaly unit

Stratigraphy

PALEOCENECAMPANIAN

Proteacidites retusus, P. thalmanni, P. sp.(Tschudypollis spp. of Nichols, 2002)

no Proteacidites,Brevicolporites colpella

no Proteacidites

OJO ALAMO SANDSTONE

(Kirtland shale of Anderson, 1960)

Figure 47. Composite stratigraphic column showing levels of samples collected by Anderson (1960) for palynologicanalysis from Fruitland Formation and Ojo Alamo Sandstone near Cuba, New Mexico. Sample localities shown onFigure 21. Key index-palynomorph levels are shown. Proteacidites renamed Tschudypollis by Nichols (2002).

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the Kirtland Formation and Ojo Alamo Sandstoneare well exposed (Figures 21, 48). This locality is220 m west of County Road (CR) 11 (Figure 21)and is 4.0 km (2.4 mi.) south of the intersection ofCR 11 and US Highway 550. Anderson’s samplewas collected from “. . . the upper carbonaceouszone in a medium-gray micaceous mudstoneapproximately 37 feet [11.3 m] below the base ofthe Ojo Alamo Sandstone.” (Anderson 1960, p. 5).The key Cretaceous index palynomorphs identifiedby Anderson from this sample were Proteaciditesretusus, P. thalmani, and P. sp. (his tables 2, 3).(The genus name “Proteacidites” was recentlychanged to Tschudypollis by Nichols, (2002, p.443-444)). The complete list of Anderson’s palyno-morphs constituting the “Kirtland shale florule” is inTable 5.

Figure 48 is a photograph of the “Kirtlandshale florule” locality. The Ojo Alamo Sandstone isabout 18 m thick here and consists of two ledges ofwhite sandstone separated by a thin bed of silt-stone and mudstone. The Ojo Alamo is underlainby the “Kirtland shale” of Anderson; this rock unit

was mapped as Kirtland Shale and Fruitland For-mation, undivided, in this area by Baltz (1967),Fassett and Hinds (1971), Woodward et al. (1972),and Woodward et al. (1973). Fassett and Hinds(1971, figure 9, plate 2), however, show that theFruitland-Kirtland interval is beveled at the top fromnorthwest to southeast across the San Juan Basin,resulting in the Kirtland being absent along theeast side of the basin, including the area of Ander-son’s “Kirtland shale florule” (see Figure 21). Thus,the rock unit underlying the Ojo Alamo Sandstoneat Anderson’s localities is more properly named theFruitland Formation. (See Figure 1.2 for a basin-wide cross section depicting the convergence ofthe basal contact of the Paleocene Ojo Alamo withunderlying Cretaceous strata.) The base of thelower Ojo Alamo Sandstone bench is stratigraphi-cally higher on the right side (north) on Figure 48than on the left (south) side. The interface betweenCretaceous and Paleocene strata here is probablyat the base of the sandy interval just above the topof the carbonaceous zone in the Fruitland Forma-

Ojo AlamoSandstone

Ojo AlamoSandstone

11 meters

“Carbonaceous zone” Fruitland Formation

(Kirtland shale of Anderson)

Figure 48. Photograph of “Kirtland shale florule” locality of Anderson (1960) showing “carbonaceous zone” fromwhich Kirtland-shale-florule sample was collected. Locality about 4 km south of Cuba, New Mexico (Figure 21).

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tion and not at the base of the rock-stratigraphicOjo Alamo.

Anderson’s “Ojo Alamo 1 florule” was col-lected from “a thin carbonaceous layer within alight brownish-buff siltstone lens at the base of theOjo Alamo sandstone.” (Anderson 1960, p. 5). Hestated that “The siltstone lens from which the sam-ple was taken could be considered a part of eitherthe Ojo Alamo Sandstone or the Kirtland shale.”This locality is in a road cut in the Ojo Alamo justeast of CR 11, 1.5 km (0.95 mi.) south of the inter-section of CR 11 and US Highway 550 (Figures 21,49). Although Anderson stated that this samplecame from “the base of the Ojo Alamo Sandstone,”subsequent mapping by Baltz (1967) and Wood-ward et al. (1973) showed that Anderson’s OjoAlamo 1 florule was actually collected from a mud-stone and siltstone layer within the Ojo Alamo. TheOjo Alamo 1 florule from this locality does not con-tain the key Cretaceous index fossil: Tschudypollis

(Proteacidites). Anderson (1960, p. 5) stated that:“The florule is very different from the underlyingone in the Kirtland shale . . .” but concluded (p. 9)that “The Ojo Alamo 1 florule has a ‘Tertiary’ aspectbut is not necessarily Tertiary from the standpointof common forms.” Anderson’s complete list ofpalynomorphs from this locality is in Table 5.

Anderson’s (1960, p. 5) “Ojo Alamo 2 florule”(Table 5) was “. . . found in a carbonaceous zone atthe base of a middle shale unit within the OjoAlamo Sandstone.” Anderson’s road directions tothis locality cannot be literally followed to arrive atthis collection site; however, the placement of thissite on his map (figure 1) is accurate. (The map onFigure 21 of the present report clearly shows howto access this site via NM State Highway 126 andCR 13: go 0.86 km (0.54 mi) east of US Hwy 550on NM Hwy 126 and then 3.7 km (2.3 mi) north andeast on CR 13); the site is about 200 m west of CR13. This sample site is within a lower bench of the

Upper bench ofOjo Alamo Ss

Florule 1 bed

Middle shaly unitof Ojo Alamo Ss

Figure 49. Photograph of “Ojo Alamo 1 florule” locality of Anderson (1960). Locality about 1.5 km south of Cuba, NewMexico (Figure 21). Geologic pick in white circle is 0.33 m. Upper bench of Ojo Alamo nearly 3 m thick. Andersonstated that this sample locality was at base of Ojo Alamo Sandstone; however, locality is now known to be in middlemudstone to siltstone bed of the Ojo Alamo as seen on Figure 21.

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83

50.1

50.2

Ojo Alamo Sandstone

O.A. 2 florule

O.A. 2 florule

4.1 meters

Fruitland Formation

Figure 50. Photographs of “Ojo Alamo 2 florule” locality of Anderson (1960). Locality about 4.5 km northeast ofCuba, New Mexico (Figure 21). Photograph 50.1 shows location of florule 2 sample collection site in about center oflower sandstone bench of Ojo Alamo Sandstone (Figure 47); bench is about 9 m thick here. Photograph 50.2 showsclose-up view of 75-mm-thick black carbonaceous shale layer from which sample containing “Ojo Alamo 2 florule”was collected (hammer handle is scaled in inches). Paleocene index fossil Brevicolporites colpella was identifiedfrom this sample.


Ojo Alamo Sandstone about 4 m above the OjoAlamo Sandstone-Fruitland Formation contact.Figure 50 shows two photographs of the Ojo Alamo2 florule site: Figure 50.1 shows the position ofAnderson’s “carbonaceous zone” within the lowerbench of the Ojo Alamo; Figure 50.2 is a close-upview of the sample site. The lower bench of the OjoAlamo Sandstone here caps an east-trendingridge, but further west, this ridge merges with thenortheasterly trending Ojo Alamo Sandstone out-crop (Figure 21). There, the Ojo Alamo consists ofthis lower sandstone bench, a middle claystone-to-siltstone layer, and an upper sandstone bench.

Anderson did not find the Cretaceous indexpalynomorph Tschudypollis in this florule, howeverhe did find that it contained the Paleocene indexfossil Brevicolporites colpella. (See Nichols andJohnson 2002, for a comprehensive discussion ofthe palynology of Cretaceous-Tertiary boundaryrocks in the Western Interior of North America.)The disappearance of Tschudypollis (a “K taxon” ofNichols and Johnson 2002) going upward in astratigraphic section provides evidence that theCretaceous-Tertiary boundary has been crossed.Moreover, also finding the Paleocene index fossilB. colpella (Nichols and Johnson 2002) presentand K taxa absent from the same strata providesunequivocal evidence of the Paleocene age of thestrata in question (Nichols, personal commun.,2005).

Figure 47 shows the stratigraphic relations ofAnderson’s sample-collection sites near Cuba,New Mexico. The stratigraphically lowest sample(about 11 m below the base of the Ojo AlamoSandstone) yielded his “Kirtland shale florule”which is notable for the presence of the Creta-ceous index fossil Proteacidites thalmani (Tschudy-pollis) “as the dominant dicotyledon” plus otherProteacidites species (Anderson 1960, p. 5 andtables 2, 3). Anderson’s “Ojo Alamo 2 florule” isfrom a sample about 4 m above the base of the OjoAlamo; this florule contains no Proteacidites(Tschudypollis) species but does contain thePaleocene index fossil Brevicolporites colpella.Going up section to the middle part of the OjoAlamo and Anderson’s “Ojo Alamo 1 florule,” againthere are no Proteacidites (Tschudypollis) speciesand according to USGS palynologist D.J. Nichols(personal commun., 2006): “Anderson's OA florule1, which lacks Tschudypollis spp. as you note,does appear to be Paleocene in age.” It thusseems clear that the Ojo Alamo Sandstone inAnderson’s study area near Cuba, New Mexico, isPaleocene in age in its entirety.

Anderson (1960, p. 13) concluded that palyn-ologic data suggest that “most of the Ojo Alamosandstone is Tertiary, but the basal part may beeither Cretaceous or Paleocene. ” As for theabundant Ojo Alamo dinosaur fossils in the typearea, Anderson stated that they may have beenreworked, or “Alternatively, pre-Lance-type dino-saurs persisted into a Tertiary environment.”Anderson thus became the second geologist (afterReeside 1924) to suggest that dinosaurs may havelived on into the Paleocene in the San Juan Basin.

Anderson’s Nacimiento 1 and 2 florule locali-ties are shown on Figure 21 but are not discussedin detail in this report, because the Paleocene ageof the Nacimiento Formation has never been ques-tioned. Anderson (1960, p. 8) stated that the“Nacimiento 1 florule” was collected from a“medium-gray, micaceous, carbonaceous mud-stone, 1 foot above the Ojo Alamo sandstone”; the“Nacimiento 2 florule” was from “an 8-inch coal bedabout 115 feet above the Nacimiento 1 florule.”Palynomorph assemblages from these localitieswere determined by Anderson to be Paleocene inage. Anderson’s palynomorph lists from his twoNacimiento localities are included in Table 5.

Baltz et al. (1966)

Baltz et al. (1966) conducted a detailed studyof the Ojo Alamo Sandstone in the Ojo Alamo typearea (Figures 3, 4, 51). This study included collect-ing rock-samples from the uppermost Kirtland For-mation, upper part of the Ojo Alamo Sandstone,and the lowermost part of the Nacimiento Forma-tion for palynologic analysis. These authors alsoredefined the Ojo Alamo Sandstone in their paper(see Figure 2). Figure 52 shows the stratigraphiclevels of the three palynologic collections of Baltzet al. (1966); because these samples were col-lected from different localities, their placement onone column on Figure 52 is diagrammatic. Thepalynomorphs identified from these three collec-tions are listed in Table 6 (see Table Appendix,page 119).

Collection 3 of Baltz et al. was obtained from a“lignite” (carbonaceous mudstone) bed in theuppermost part of the Kirtland Formation (Figure52) just north of Alamo Wash in the extreme NW ¼Sec. 7, T. 24 N., R. 11 W. (BAA-3 on Figure 4).

Anderson, in Baltz et al. (p. D17) stated that:The florule of collection 3 from the Kirtland is strikingly different from collections 1 and 2 and from any of the Cretaceous and Tertiary florules described by Anderson (1960) from the

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85

Ojo Alamo Sandstone

Ojo Alamo Sandstone

N

J

J

K

L

BarrelSpring

Barrel Spring

8 9

17 16

Ojo Alamo tradingPost (ruins)

M

M

D6391

D6880

O

P4300,

D6901 (24-5),Archival split 24-5

D9156-BD9156-A




NacimientoFormation

Kirtland Formation

San Jua

n Coun

ty Road7500

De-na-zin

De-na-zin

Was

h

Wash

drainage

Alamo Wash

Ojo Alamo Sandstone

Ojo Alamo Ss dinosaur bonesample locality - chemical analysis

Kirtland Fm dinosaur-bonesample locality - chemical analysis

Ojo Alamo Ss dinosaurbone locality

LEGEND

Palynologic sample locality - palynomorphassemblage is Paleocene

Palynologic sample locality - palynomorphassemblage is late Campanian to earlyMaastrictian

T. 24 N., R. 11 W

BAA-1

82303-E, 82403-A

SGL 046

110303-D

Figure 51. Large-scale geologic map of Barrel Spring area showing USGS and other paleobotany localities dis-cussed in text. Dinosaur-bone localities also shown and geochemistry of bone samples from lettered localities shownon Tables 2 and 3. Geology modified from Brown (1982); base of Ojo Alamo remapped by author for this study. All ofarea, except south of San Juan County Road 7500, in Bisti - De-na-zin Wilderness Area.


eastern part of the basin. The dominant forms of collection 3 are polypodiaceous spores and a monosulcate grain with echinate-clavate sculpture. Pinaceous conifer pollen are [sic] common. Dicotyledon grains are much fewer than in any of the eastern florules, and the dominant form is a tricolpate, reticulate,

brevaxial grain with intersemiangular to intersemilobate outline. Smooth and warty trilete spores are present in collection 3, and there are many cystlike structures with hollow processes that resemble some hystrichosphaerids. The florule contains Liliacidites leei Anderson which occurs in the Kirtland, Ojo Alamo, and Nacimiento florules of the eastern part of the basin and Liliacidites hyalaciniatus? Anderson which occurs in the Kirtland and Ojo Alamo 1 florules of the eastern part of the basin. Proteacidites thalmani Anderson is the only really distinctive form in collection 3 that is found also in an eastern florule. It occurs in Anderson's (1960) Kirtland Shale and Lewis Shale florules and suggests a Cretaceous age for collection 3. Collection 1 was from a “lignitic shale” (carbo-

naceous mudstone) interbed in the upper part ofthe Ojo Alamo Sandstone (Figure 52). This localitywas reported to be “on the mesa about one-eighthmile [200 m] north of Barrel Spring” by Baltz et al.(p. D17). The location for this sample collectioncannot be correct because 200 m north of BarrelSpring is not “on the mesa” and not in the upper-most Ojo Alamo Sandstone, but rather is in thedrainage-way of De-na-zin arroyo in the upper Kirt-land Shale. The actual location for this localityappears to be in the west-central part of Sec. 16, T.24 N., R. 11 W. at the edge of the mesa about 70 mnorth of Barrel Spring (labeled BAA-1 on Figures 4,51).

Collection 2 was from an extensive bed of “lig-nite” (carbonaceous mudstone) in the lower part ofthe Nacimiento Formation (Figure 52) in the south-west part of Sec. 10, T. 24 N., R. 11 W. in BarrelSpring Arroyo (Figure 4). Barrel Spring Arroyo ofBaltz et al. (1966) is now named De-na-zin Wash(Alamo Mesa East, 1/24,000 USGS topographicquadrangle map); the collection 2 palynologiclocality is labeled BAA-2 on Figure 4.

Anderson (in Baltz et al., p. D17) stated that:Collection 1 from the Ojo Alamo and collection 2 from the Nacimiento are similar to each other and contain common to abundant grains of Ulmoideipites tricostatus Anderson and Podocarpus sp. These are the two dominant types of grains in Anderson's (1960) Ojo Alamo florules from the eastern part of the basin. Several kinds

Collection 1

Collection 2

Collection 3

Ojo AlamoSandstone (36 m)

KirtlandFormation


Figure 52. Stratigraphic column of Ojo Alamo Sand-stone and adjacent strata near Barrel Spring in OjoAlamo type area (Figures 3, 4). Column is modified fromBaltz et al. (1966, plate I, column 11). Stratigraphic lev-els for collections 2 and 3 projected into column; samplecollection 2 from west of Barrel Spring, sample collec-tion 3 from north of Ojo Alamo Arroyo (Baltz et al. 1966,plate I).

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of Momipites grains are present in collections 1 and 2; these also are common in Anderson's (1960) Ojo Alamo and Nacimiento florules from the eastern part of the basin. The florule of collection 1 contains many large inaperturate semihexagonal grains, some monosulcate grains, monolete and trilete spores, triporate pollen, and pinaceous conifer pollen. The florule of collection 2 contains Quercus? sp., Arecipites cf. A. reticulatus (Van der Hammen), Cupaneidites cf. C. major Cookson and Pike, Paliurus triplicatus? Anderson, and some spores, all of which are present in Anderson’s (1960) Ojo Alamo or Nacimiento florules from the eastern part of the basin.Complete palynomorph lists for the three

palynologic localities of Baltz et al. (1966) were notprovided.

Baltz et al. (1966, p. D17) concluded that:“The palynology does not directly fix the age of theRestricted Ojo Alamo Sandstone . . .” but thenadded the somewhat contradictory statement: “Insummary, the palynologic and physical-strati-graphic evidence of the [Paleocene] age of therestricted Ojo Alamo Sandstone are in agreement.”As for the differences in palynomorph assem-blages in the Ojo Alamo type area and in Ander-son’s (1960) collections near Cuba, New Mexico,on the east side of the basin, Baltz et al. (1966)suggested that the different florules:

. . . allow for the possibility that rocks equivalent in age to the upper shale member of the Kirtland (colln. 3) at Ojo Alamo may be absent from the eastern part of the basin. This interpretation would be consistent with the physical evidence for a hiatus between the deposition of the Kirtland and the Ojo Alamo.Subsequent work, demonstrating the pres-

ence of a nearly 8-m.y. hiatus at the Kirtland-OjoAlamo contact (Fassett and Steiner 1997; Fassett,2000), and the thinning of Cretaceous strata bymore than 650 m from northwest to southeastacross the San Juan Basin (Figure 1), shows thatthe upper Kirtland Formation strata sampled at OjoAlamo Arroyo indeed are not present east of Cuba,New Mexico. The stratigraphic cross sections ofFigures 33-35, conclusively show that the upper-most Kirtland Formation strata in the Ojo Alamotype area (drill-hole 2) are not present in the Cuba,

New Mexico, area (drill-hole 6). Thus, the differentpalynomorph assemblages at the two places arethe result of sampling of strata of different agesdeposited in quite different environments: relativelynear to the regressing Pictured Cliffs Sandstoneshoreline near Cuba vs. far inland from the paleo-shoreline at the Ojo Alamo Sandstone type area.

Fassett and Hinds (1971)

Fassett and Hinds (1971, table 1) published apalynomorph list for samples from eight localities inthe San Juan Basin. At a locality in the northeastpart of the basin in Colorado, the lowermost Fruit-land Formation was sampled; at another locality,south of Mesa de Cuba, the lower part of theNacimiento Formation was sampled. The other sixlocalities were in the Mesa Portales study area(Figure 21), where multiple samples were collectedfrom the undivided Fruitland-Kirtland Formationand from the Ojo Alamo Sandstone. All these sam-ples were collected by the author between 1964and 1968 and were analyzed by R.H. Tschudy, U.S. Geological Survey, Denver, Colorado; Tschudy’sdata were provided in written communications in1966, 1967, and 1968. Complete palynomorph listsfor these localities were presented in table 1 ofFassett and Hinds (1971); that table is reproducedherein as Table 7 (see Table Appendix, page 120).(The stratigraphic positions of the Mesa Portalessample localities of Fassett and Hinds are shownon Figures 22 and 23; the other palynologic samplelocalities shown on these figures were collectedlater and are discussed in a subsequent section ofthis appendix.) Palynomorph assemblages in Fas-sett and Hinds (1971) from Mesa Portales madeclear that the Cretaceous-Tertiary boundary therewas located below the base of the rock-strati-graphic Ojo Alamo Sandstone in the 13 m intervalbetween samples D3738-C and D3738-B (Figures22, 23).

All of the Fassett and Hinds samples from theundivided Fruitland-Kirtland interval in the MesaPortales study area contained abundant speci-mens of the Cretaceous index fossil Proteacidites(Tschudypollis). Table 7 lists Proteacidites retususAnderson from samples D3738-C, D4017-A,D4017-B, and D4017-C (Figures 22, 23). Tschudy-pollis spp. has come to be universally accepted asone of the premier index palynomorphs for upper-most Upper Cretaceous rocks throughout much ofthe Western Interior of North America. For exam-ple, Tschudy (1973, p. 133) wrote:

The genus Proteacidites throughout the Rocky Mountain region is limited to the

87


Late Cretaceous. In no place, except as isolated redeposited specimens, has it been found in the Paleocene.Samples D3738-A and D3738-B from the Ojo

Alamo Sandstone (Figures 22, 23) contained noProteacidites specimens. In his discussion of thesesamples in Fassett and Hinds (1971, p. 33)Tschudy wrote of sample D3738-A: “This assem-blage is clearly of Paleocene age and is equivalentto the assemblages found by Anderson [1960] inthe Ojo Alamo Sandstone.” And for sample D3738-B he wrote that it was “from the Tertiary.” Tschudyfurther wrote in Fassett and Hinds (1971, p. 33):

It is possible to postulate a hiatus between the Cretaceous and Paleocene at this locality. The genus Araucariacites (table 1) has not been found in rocks younger than Campanian in the Rocky Mountain Region. Moreover, the Cretaceous assemblages found in your samples are different from those found in the latest Cretaceous of the Raton Formation. However, it must be emphasized that we do not have enough control data from your area to do more than guess at a possible hiatus. For example, the closest area from which we have control on the occurrence of Araucariacites in the Upper Cretaceous is northern Colorado. Furthermore, we know that several floral provinces existed during Late Cretaceous time. Thus, the palynological data of Fassett and

Hinds (1971) from the Mesa Portales study areaestablished the presence of the Cretaceous-Ter-tiary interface below the base of the Ojo AlamoSandstone (Figures 22, 23), confirmed the age ofthe Ojo Alamo in its entirety as Paleocene, andsuggested the presence of a hiatus at the K-Tinterface representing all of post-Campanian(Maastrichtian) time.

Tschudy (1973), the Gasbuggy Core

The Gasbuggy project was initiated in Febru-ary 1967 with the drilling of the Gasbuggy 1 (GB-1)core hole in the east-central part of the San JuanBasin (Figure 1.1). The objective of the project wasto explode a nuclear device in the Pictured CliffsSandstone about 1,200 m (4,000 ft) deep as anexperiment to determine whether or not natural gasproduction from the Pictured Cliffs, a relativelyimpermeable rock unit in that part of the basin,could thereby be significantly increased. A continu-ous core was cut starting in the lower part of the

Nacimiento Formation, through 60 m of massiveOjo Alamo Sandstone, 73 m of the Fruitland For-mation, and 192 m of Pictured Cliffs Sandstoneand underlying Lewis Shale (Fassett 1968a, b).This continuous core offered an unprecedentedopportunity to obtain a large number of closelyspaced rock samples across the Cretaceous-Ter-tiary interface from unweathered core material.

Samples from core hole GB-1 were collectedat about 6m intervals by the author in 1968, fromthe Nacimiento Formation down through the upperpart of the Lewis Shale. Core chips from 52 levelswere collected and submitted to R.H. Tschudy foranalysis. Tschudy reported that: “Thirty-nine sam-ples yielded some palynomorphs and thirty ofthese yielded sufficient specimens for a percent-age count.” Figure 53 is a copy of figure 1 fromTschudy (1973) showing the distribution of the GB-1 core samples. Tschudy (1973, p. 142) alsoincluded a table listing all of the palynomorphsidentified from the GB-1 core samples; Table 8(see Table Appendix, page 121) is a modified ver-sion of Tschudy’s table showing palynomorphsidentified from the Fruitland, Ojo Alamo, andNacimiento Formations. It is interesting to note,that even in the unweathered core material, onlyslightly more than half of the samples yieldedmeaningful numbers of palynomorphs, and 12samples were barren of palynomorphs.

Tschudy’s GB-1 palynomorph list (Table 8)shows that the Cretaceous index fossil Tschudy-pollis spp. (Proteacidites spp. on Tschudy’s list)averages nearly fourteen specimens per FruitlandFormation slide. The two lowermost samples fromthe Ojo Alamo Sandstone; D4665-A and D4666-K(Figure 53, Table 8) yielded (Tschudy 1973, p. 133)“. . . very sparse specimens of Proteacidites . . .possibly . . . due to redeposition of Cretaceous pol-len in Tertiary rocks near the Cretaceous-Tertiaryunconformity.” Tschudy further stated that the sam-ple at 3515.6 feet [D4665-D, Figure 53] “containedMaceopolipollenites tenuipolus [now, Momipitestenuipolus], a fossil that elsewhere in the RockyMountain region is limited to the Paleocene but isnot present in the lowermost Paleocene.”

On the basis of palynologic data, Tschudyplaced the Cretaceous-Tertiary boundary in theGB-1 core between samples D4778-D and D4666-K (Figure 53, Table 8); essentially, at the base ofthe Ojo Alamo Sandstone.

Figure 54 (after Tschudy 1973, figure 3)shows the stratigraphic distribution of selectedpalynomorphs identified from samples of the Gas-buggy core. The hiatus at the Cretaceous-Tertiary

88


89

USGSPALEOBOTANICAL

LOCATION

Figure 53. Stratigraphic column of Gasbuggy 1 drill core (from Tschudy 1973, figure 1). Depths on left side of columnin feet below Kelly Bushing of drill rig (10 ft above ground level). Depths in feet on right side of column are levels ofsamples collected for palynologic analysis; USGS paleobotanic sample numbers for samples also shown.


(Campanian-Paleocene) boundary is marked bythe termination of the first 11 palynomorphs (orgroups) at the contact between the Fruitland For-mation and overlying Ojo Alamo Sandstone. Iso-lated specimens of Proteacidites spp.,Aquilapollenites spp., and Tricolpites sp. are pres-ent above this contact, but as articulated byTschudy, above, the presence of these isolatedspecimens is probably due to “redeposition of Cre-taceous pollen in Tertiary rocks.” The Ojo Alamowas deposited on a vast erosion surface that bev-eled Upper Cretaceous rocks across the entire SanJuan Basin (Figure 1). It is thus not surprising thata few, random, Cretaceous palynomorphs rede-posited from underlying Cretaceous strata arepresent in the lowermost part of the Ojo Alamo.

Lowermost Ojo Alamo sediments were depositedby high-energy streams flowing from the north ornorthwest across this widespread erosion surface,and it would indeed be more remarkable if a few,random, Cretaceous palynomorphs had not beentransported by wind or water into the lowermostOjo Alamo Sandstone’s channel-sandstone andover-bank deposits.

Figure 54 also shows the emergence of threenew species in the Paleocene Ojo Alamo: Peri-poropollenites sp., Tricolpites anguloluminosus,and Maceopolipollenites tenuipolus (now Momip-ites tenuipolus). In addition, Ulmipollenites sp.,identified in only three isolated samples in Creta-ceous strata, is found to be continuously present

EXPLANATION

Isolated specimens

Continuous occurrence

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

3436.6 NacimientoFormation

Ojo Alamo

Sandstone

PALEOCENE

CRETACEOUS (Campanian)

Fruitland

Formation

Pictured Cliffs

Sandstone

Pictured Cliffs

Sandstone

Fruitland Formation (lower tongue)

Lewis Shale

SPECIES OR GROUPS4252.7

Proteacidites spp.

Aquilapollenites spp.

Trudopollis meekeri

Camarozonosporites and lycopodiacidites

Ilexpollenites sp.

cf Triporopollenites rugatus

Tricolpites reticulatus

Accuratipollis spp.

Tricolpites sp.

cf Tilia wodehousei

Kurtzipites trispissatus

Ulmipollenites spp.

Nyssapollenites spp.

Periporopollenites sp.

Tricolpites anguloluminosus

Maceopolipollenites tenuipolus

FEET

ft00

m

30

Figure 54. Stratigraphic distribution of selected palynomorphs identified in samples from the Gasbuggy core (Figure1); modified from Tschudy (1973, figure 3). Hiatus at the Fruitland Formation-Ojo Alamo Sandstone (Cretaceous-Ter-tiary) contact is clearly indicated by the termination of the first 11 palynomorphs (except for probably reworked speci-mens) at the contact and the emergence of five new species just below or above the contact. Tick marks along leftside of diagram show levels of sample collections.

90


through most of the Ojo Alamo and into theNacimiento Formation.

Tschudy compared the Cretaceous palyno-morph assemblages in the GB-1 core with palyno-morph assemblages from uppermost Cretaceousrocks in northern Montana and Wyoming. On thebasis of those comparisons he concluded thatuppermost Upper Cretaceous palynomorphassemblages present in that region were missingfrom the GB-1 core. In addition, Tschudy comparedthe GB-1 palynomorph assemblages with those hehad identified from drill-core samples in the RatonBasin, only 230 km east of the San Juan Basin andconcluded that the uppermost-Cretaceous pollenassemblages in the Raton Basin were not presentin the GB-1 core hole. Tschudy (1973, p. 131)summed up this situation by stating:

A section of the Upper Cretaceous, present in the upper part of the

Cretaceous in the Raton Basin, is absent from the Upper Cretaceous of the Gasbuggy core. This confirms the presence of a marked hiatus at the top of the Cretaceous, as previously postulated in the San Juan Basin [in Fassett and Hinds 1971, p. 33].Figure 55, modified from Tschudy (1973, fig-

ure 5), is a cross section showing the correlation ofpalynomorph assemblages from the Raton Basinto the San Juan Basin. This diagram shows thatseveral palynomorph zones present in the upper-most Cretaceous strata of the Raton Basin aremissing in the San Juan Basin.

Fassett et al. (1987)

Fassett et al. (1987) surveyed all of the knownlocalities in the Ojo Alamo Sandstone where eitherdinosaur bone or palynomorphs had been docu-


Ojo AlamoSandstone

FruitlandFormation

Pictured CliffsSandstone Pictured CliffsSandstone

LewisShale Trinidad

Sandstone

VermejoFormation

RatonFormation

RatonFormation

RATON BASIN - COMPOSITE SECTIONP6.1 Core hole

Core holeP800

100

200

Feet

Landslide Section

Gasbuggy 1

Maceopolipollenites tenuipolus - bottom

Tricolpites angulaluminosus Thomsanipolis sp.

Accuratipolis spp., Ilexpollenites sp. - topTrudopollis meekeri - top

Tricolpites reticulatus Tricolpites sp. - bottom

(Momipites tenuipolis)

TERTIARYCRETACEOUS

TERTIARYCRETACEOUS

Tongue of FruitlandFormation

SAN JUAN BASIN

EAST

WEST

230 km

30

60

Meters

cf Tilia wodehousei Kurtzipites trispissatus

Figure 55. Palynologic correlation diagram based on core-hole data in the San Juan and Raton Basins; modifiedfrom Tschudy (1973, figure 5). Tick marks on drill-hole lines represent levels where core samples yielded identifiablepalynomorphs. All of Maastrichtian stage appears to be missing in Gasbuggy 1 core. Hiatus at Cretaceous-Tertiary(K-T) interface is nearly 8 m.y. in the southern San Juan Basin; no hiatus in Raton Basin at the K-T boundary.

91


mented. They discussed the palynomorphs thathad been identified from the Ojo Alamo Sandstoneby R.H. Tschudy at three places in the basin: 1)Near Barrel Spring, 2) At Mesa Portales, and 3) Inthe Gasbuggy 1 core. Barrel Spring Locality. The Barrel Spring localitywas sampled by C.J. Orth, Los Alamos NationalLaboratory, in 1982; Orth’s samples were submit-ted to R.H. Tschudy for analysis. According to Orthet al. (1982, p. 427), this locality is 2 km east ofBarrel Spring on De-na-zin Arroyo (probably in theSE1/4 SE1/4 Sec. 9, T. 24 N., R. 11 W., Figures 4,51). The sample, labeled USGS paleobotany local-ity number D6391 (Tschudy, personal commun.,1982) was collected from a claystone layer about 3m below the top of the Ojo Alamo Sandstone.Tschudy reported that:

This assemblage is clearly of Paleocene age. Several taxa including Momipites tenuipolus were not recorded by Anderson from the Ojo Alamo, but were recorded from the overlying Nacimiento. I have not seen M. tenuipolus in any basal Paleocene samples from the Western Interior. This occurrence suggests that the sample is not from the basal Paleocene but rather from the upper Lower or Lower middle Paleocene.

Mesa Portales locality. Fassett et al. (1987, p. 30,31) referred to a new Ojo Alamo Sandstone palyn-ologic sample locality on Mesa Portales (D6583-B,Figures 22, 23) but did not list all of the palyno-morphs identified from that locality. They did state,however, that R.H. Tschudy had reported the pres-ence of the Paleocene index palynomorph Momip-ites tenuipolus in that assemblage. (The completelist of palynomorphs from this locality is in Table 9(see Table Appendix, page 122), and Tschudy’scomments about this assemblage are given in fullin the “This Paper” part of the “Palynology” sectionof this report.)Gasbuggy Core. The results of Tschudy’s (1973)study of the palynomorphs identified from the Gas-buggy-core samples were summarized in Fassettet al. (1987), and the Ojo Alamo Sandstone part ofthe core was illustrated in a stratigraphic column.Tschudy’s comments to the effect that the palyno-morphs from the Ojo Alamo Sandstone in the Gas-buggy core indicated that it was Paleocene in itsentirety were cited. The complete list of palyno-morphs identified from the Gasbuggy core samplesis in Table 8.

Newman (1987)

K.R. Newman (1987) published a comparisonof the palynology of several Western Interior basinswith that of the San Juan Basin. Newman and C.Manfrino (1984) had conducted extensive palyno-logical studies of uppermost Cretaceous and low-ermost Tertiary strata in the northern San JuanBasin in the Animas River valley south of Durango,Colorado, and compiled a robust palynologic dataset there. The Ojo Alamo Sandstone is absent inthe northern part of the San Juan Basin and thelowermost Paleocene formation there is the Ani-mas Formation, thought by Reeside (1924), andmost subsequent workers, to be the same age asthe Ojo Alamo Sandstone in the New Mexico partof the basin. (The Animas Formation is discussedin separate sections of this paper.) Figure 56shows Newman’s interpretation of the strata adja-cent to the Cretaceous-Tertiary interface in thenorthern San Juan Basin based on palynology.

Newman also carried out detailed studies ofthe palynology of the Fruitland Formation in thesouthern part of the San Juan Basin. These studieswere based on core samples from the Fossil Forestarea (Figure 3); Newman (1987, p. 159) wrote:

Ten samples from 51 m of cored Fruitland Formation have yielded an excellent assemblage of palynomorphs including the guide fossils Trudopollis meekeri, Myrtaceoipollenitius peritus, and Pseudoplicapollis sp. . . . Therefore, the combination of the ammonite and palynomorph zones indicates late Campanian age for the upper Lewis, Pictured Cliffs, and Fruitland Formations in this area, just as at Durango.Newman did not publish a complete list of

identified palynomorphs from this core.Newman (1987, p. 159) discussed a rock

sample from the upper Kirtland Formation at PotMesa (Figure 1) and stated that it contained theMaastrichtian palynomorphs Proteacidites(Tschudypollis), Balmeisporites, Interpollis, Gun-nera, Kurtizipites, and Ulmoideipites spp. (New-man stated that this sample was from the OjoAlamo Sandstone, but subsequent studies (Fassettet al. 2002) now place this sample in the upper-most Kirtland Formation.) Fassett et al. (2002) pub-lished a list of palynomorphs identified by D.J.Nichols from a separate sample from this sameinterval; a comparison of that palynomorph assem-blage with Newman’s is discussed in the “Fassettet al. (2002)” section of this appendix.

92


Newman also reported on a sample heclaimed was from the Ojo Alamo Sandstone from alocality “near Farmington” (no more specific loca-tion was provided). The author had escorted New-man to the San Juan River Hadrosaur-bone site in1984 and was informed by Newman at that timethat he (Newman) had collected a rock sample“from a lower stratigraphic level” (well below thelevel of the Hadrosaur bone), but Newman was notspecific as to the exact stratigraphic level of thatsample. (It is assumed that Newman’s “near Farm-ington” locality is the San Juan River site of thisreport.) Newman (1987, p. 159) stated that hissample collected “near Farmington” yielded thesame Maastrichtian palynomorphs that he found atPot Mesa in the uppermost Kirtland Formation.Newman’s determination that the “Ojo Alamo”palynomorph assemblage “near Farmington” isMaastrichtian is not in agreement with the threeother palynomorph lists from the Ojo Alamo at theSan Juan River site (Table 10 (see Table Appendix,page 123)). Those palynomorph lists all containedthe Paleocene index palynomorph Momipites tenu-ipolus, and one of them also contained the Paleo-cene index palynomorph Brevicolporites colpella(Table 10). Three of the palynologists found theCretaceous index fossil Proteacidites (Tschudypol-lis) in their samples from the San Juan River site,however, D.J. Nichols did not find this index fossilin any of his three samples from that locality. The

presence of two Paleocene index palynomorphs insamples from this locality suggests that the Prote-acidites specimens found in some of them werereworked. Fassett and Lucas (2000) and Fassett etal. (2002) concluded that the Ojo Alamo Sandstonewas Paleocene in age at the San Juan River siteon the basis of palynologic data.

Newman (1987) concluded, (as did Tschudy1973), that the Ojo Alamo Sandstone rests on asignificant unconformity in the San Juan Basin andthat a hiatus representing most, if not all, of theMaastrichtian and possibly the lowermost part ofthe Paleocene separated Cretaceous from Tertiaryrocks throughout the San Juan Basin. Newman(1987, figure 10) also showed that more uppermostCretaceous strata were missing in the southernpart of the basin than in the northwestern part.

Fassett and Lucas (2000)

Fassett and Lucas (2000) published a paperfocused on the large hadrosaur femur that hadbeen discovered in the Ojo Alamo Sandstone atthe San Juan River site (Figure 1). They reportedthe results of palynologic studies of three samplescollected from a carbonaceous to coaly shale bedlocated 3.5 m stratigraphically below the level ofthe hadrosaur femur (Figure 57). (Those threesamples are shown as a composite list of samples6877-A, -B, and -C on Table 10.) These sampleswere processed and analyzed by D.J. Nichols who

Formations Guide Fossils Stages

Animas Fm.

McDermott Fm.

Upper Sh. mbr.

Farmington Ss. Mbr

Lower sh. mbr. Kirt

land

Form

atio

n

Fruitland Fm.

Pictured Cliffs Ss.

Lewis Sh.

Didymoceras cheyennense

Baculites scotti

(Trudopollis-Myrtaceoipollenites-Pseudoplicapollis zone)

Lower Paleocene

Lower Maastrichtian

Upper Campanian

Upper Campanian Palynomorphs

Lower Maastrichtian Palynomorphs

Lower Paleocene Palynomorphs

100

feet

300

m

? ?

Figure 56. Biostratigraphic diagram of uppermost Cretaceous-lowermost Tertiary strata in northern San Juan Basin(south of Durango, Colorado, Figure 1); modified from Newman (1987, figure 7). Ojo Alamo Sandstone not present innorthern San Juan Basin; lower part of Paleocene Animas Formation is time-equivalent of Ojo Alamo there.

93


94

3.5 mHadrosaur femur

Pollen samples

KirtlandFormation

Ojo Alamo Sandstone27 m

PaleoceneLate Cretaceous (Campanian)

Ojo AlamoSandstone(of Reeside, 1924)

120 meters

Section ofFigure 57.1

LEGEND

Hadrosaur femur

Conglomeratic sandstone

Mudstone

Coaly carbonaceous shalecontaining Paleocene pollen

KirtlandFormation

PaleoceneLate Cretaceous (Campanian)

15 m

(Brevicolporites colpella, Momipitestenuipolus, NO Tschudypollis spp.)

57.1

57.2

Figure 57. Stratigraphic columns of Ojo Alamo Sandstone at San Juan River site (Figure 1). 57.1 is expanded-scaleview of lower part of Ojo Alamo column of 57.2. Figures show relative positions of large (1.3m long) hadrosaur femur(Figure 37.1) collected from Ojo Alamo Sandstone at San Juan River locality and rock samples collected for palyno-logic analyses. Paleocene index palynomorphs identified by D.J. Nichols, (USGS) are shown. Modified from Fassettand Lucas (2000, figure 8).


found that the samples contained the Paleoceneindex fossils Momipites tenuipolus and Brevicolpo-rites colpella and no specimens of the Cretaceousindex fossil, Tschudypollis spp. (Nichols, personalcommun., 1994). Thus, the palynologic evidencefor the age of the Ojo Alamo Sandstone at the SanJuan River site showed it to be unequivocallyPaleocene. On the basis of this evidence, Fassettand Lucas (2000, p. 229) stated that the hadrosaurfemur found above this palynomorph assemblagemust have come from a dinosaur that lived duringearliest Paleocene time, and they concluded that:“some dinosaurs in the San Juan Basin survivedthe ‘terminal’ end-Cretaceous asteroid impactevent only to become extinct a few hundred thou-sand years (at most) later, in earliest Paleocenetime.”

As discussed above, Newman (1987) hadreported a palynomorph assemblage at his “nearFarmington” locality totally different from theassemblages identified by D.J. Nichols at the SanJuan River site. Table 10 shows that there are nopalynomorphs in common between the Nichols listand the Newman list. Because the palynomorphassemblages of Fassett and Lucas (2000, table 1)came from three separate samples and becausethose results have been independently replicatedtwo other times (Frederiksen personal commun.,1986, and Braman, personal commun., 2000 asdiscussed below in the “This Paper” section of thisreport) it seems evident that Newman’s (1987)palynomorph assemblage could not have comefrom the Ojo Alamo Sandstone at the San JuanRiver site. The base of the Ojo Alamo Sandstone iscovered by slope wash immediately below the had-rosaur-bone site, and thus its contact with theunderlying Kirtland Formation is masked, it may bethat Newman’s sample containing Cretaceouspalynomorphs “near Farmington” may actuallyhave been collected from the uppermost KirtlandShale and not from the Ojo Alamo Sandstone.Another possibility is that Newman’s sample camefrom a rip-up clast of Kirtland mudstone imbeddedin the lowermost part of the Ojo Alamo Sandstone.Such rip-up clasts are not uncommon in the lowermeter or two of the Ojo Alamo Sandstone in thisarea. A third possibility is that if Newman’s sampledid indeed come from the Ojo Alamo, the Maas-trichtian palynomorphs found therein werereworked from underlying Cretaceous strata. Andfinally, Newman’s sample may have come from theKirtland Formation at an entirely different site fromthe San Juan River site.

Fassett et al. (2002)

Ojo Alamo Type Area. Fassett et al. (2002)summarized the study of Fassett and Lucas (2000)and in addition discussed the palynology of Creta-ceous and Tertiary strata in the Ojo Alamo typearea (Figures 3, 4). These authors listed palyno-morphs identified by D.J. Nichols (personal com-mun., 1994) from rock samples in the Ojo Alamotype area. (Figures 4 and 51 show the locations ofthe palynologic collection sites in the Ojo Alamotype area; Figure 51 is a larger-scale map of theBarrel Spring area showing palynologic samplelocalities in more detail.) One sample (no. 24-5,D6901 of Figure 51) from a carbonaceous shalebed less than 1 m below the base of the Ojo AlamoSandstone yielded “a well-preserved assemblageof palynomorphs” including the Paleocene indexfossil Momipites tenuipolus (Nichols, personalcommun., 1994). (Table 6 contains the publishedpalynomorph lists from the Ojo Alamo type area.)Nichols reported that the palynomorph assemblagefrom this sample closely resembled the Paleoceneassemblage found in the Ojo Alamo at the SanJuan River site (Table 10). Sample D6901 alsocontained the Cretaceous index fossil Tschudypol-lis, however, Fassett et al. (2002, p. 318, 319)stated that:

The Proteacidites specimens in this assemblage must be reworked from underlying Cretaceous strata: the reworking of some Cretaceous palynomorphs into this Paleocene assemblage is not unexpected because the early Paleocene swamp in which indigenous Paleocene pollen was accumulating was located on an erosion surface (peneplain) on Kirtland Formation strata of Campanian age and Cretaceous pollen could easily have been transported laterally a few, to a few tens of meters across this surface in wind-blown dust and deposited in the Paleocene swamp.On the basis of the presence of the Paleocene

index fossil M. tenuipolus in this palynomorphassemblage and its similarity to the palynomorphassemblage from the Ojo Alamo Sandstone at theSan Juan River locality, Fassett et al. (2002) con-cluded that the Ojo Alamo Sandstone, including itscontained dinosaur fauna in the Ojo Alamo typearea, is Paleocene in age. Figure 58 is a compositestratigraphic column for the Ojo Alamo type area

95


showing the positions of palynologic samples col-lected there.

Nichols (1994, written commun.) identifiedand discussed palynomorphs from the upper OjoAlamo Sandstone at USGS locality D6880 (labeledsample 24-3C on table 2 of Fassett et al., 2002).This locality is about 0.6 km east of Barrel Spring(Figure 51) and about 30 m above the base andabout 5 m below the top of the Ojo Alamo Sand-stone. (Fassett et al. 2002, incorrectly stated thatthis sample was 15 m above the base of the OjoAlamo Sandstone.) This sample was from a darkgray mudstone pod completely enclosed within theupper conglomeratic sandstone bench of the OjoAlamo. Nichols listed the palynomorphs from thissample (Table 6) and stated that it “yielded abun-

dant cutinite as well as palynomorphs” and con-cluded that “Based on this assemblage, the sampleis Paleocene in age.”

Fassett et al. (2002) also reported palyno-morph identifications from samples collected fromthe uppermost Kirtland Formation in the vicinity ofBarrel Spring from a coaly, carbonaceous shalebed. This sample, numbered 043002 in Fassett etal., came from 3 m below the base of the OjoAlamo Sandstone less than 100 m west of BarrelSpring (Figure 51). D.J. Nichols (personal com-mun., 2000) reported that this sample (USGS num-ber P4300, Figure 51) contained a “well-preservedassemblage of palynomorphs indicating Late Cre-taceous age.” Nichols stated that:

The assemblage identified consists of 12

73.04 Ma

LEGEND

Dinosaur bones (Paleocene)

Dinosaur bones (Judithian)

Paleocene pollen -- M. tenuipolus

Cretaceous pollen -- Tschudypollis

Ar39

Ar40

single-crystal sanidine age Ash bed J with

Lowermost Paleocene mammal bones (Puercan)

NacimientoFormation

Ojo AlamoSandstone (35 m)

(late Campanian)

Paleocene

KirtlandFormation

Palynologic sample level and number

~65.2 MaD6901

D6391, BAA-1

D6880

D6880

BAA-2

83203-E, 82403-A, 110303-DP4300, SGL 046, D9156-A, B,BAA-3, D8179, D8180

Figure 58. Composite stratigraphic column for Ojo Alamo type area showing relative stratigraphic levels of samplescollected for biochronologic and 40Ar/39Ar sanidine-crystal dating from Ojo Alamo Sandstone and uppermost KirtlandFormation. Samples from different localities are projected into one column for ease of portrayal, however, localitiesare dispersed throughout Ojo Alamo type area as shown on Figures 4 and 51.

96


species, mostly fossil pollen, including three that are restricted to the Upper Cretaceous and none that are known to occur only in the lower Tertiary. The Cretaceous species are Tricolpites interangulus, Proteacidites retusus, and P. thalmannii. Tricolpites interangulus is the most common single species in the assemblage, and an estimated 300 specimens are present on the slide examined. This species is known from the upper Campanian-lower Maastrichtian interval in Colorado and New Mexico. The species of Proteacidites are well known Upper Cretaceous guide fossils throughout the Western Interior region.The complete list of palynomorphs from this

sample is in Fassett et al. (2002, table 2) and isshown on Table 6 of this report.

Fassett et al. (2002, p. 319) also stated that:Additional samples from the same level in this bed (a few meters below the base

of the Ojo Alamo) a few hundred meters northwest of the 043002 sample site also yielded Campanian to lower Maastrichtian palynomorphs (Nichols,personal commun., 2000).The locations and palynomorph lists obtained

from those samples are provided in the “ThisPaper” section of this report.Pot Mesa. At Pot Mesa (Figures 3, 59) the OjoAlamo Sandstone has been considered by someinvestigators to consist of just one sandstonebench and by others to contain two sandstonebenches, as discussed in Fassett et al. (2002, p.324). In that report, Fassett et al. concluded thatthe Ojo Alamo consisted only of the uppermost ofthe two benches in question at Pot Mesa. A rocksample collected for palynologic analysis fromabout 9 m below the base of the upper bench wasfound to be unquestionably Cretaceous in age(Nichols personal commun., 1994). Fassett et al.(2002) did not list the palynomorphs identified atthis site, but that listing is provided in the “ThisPaper” section of this report.

Dinosaur bone locality

A

B

8 9 10

1517 1618

7 Kirtland Formation

PPS

Ojo Alamo Sandstone

and younger rocks

USGS SL 10-1

C

Pot MesaNo. 2

Pipeline Road

Star Lake Pumping Station - 3.6 miles

T. 20 N., R. 6 W.

Palynologic-sample locality

Figure 59. Geologic map of Pot Mesa area; outcrop of Ojo Alamo Sandstone modified from Scott et al. (1980). Dino-saur bone sample-site letters keyed to Tables 2 and 3 that show abundances of selected elements from samples. Dot-ted line near bone-sample locality B is primitive road to edge of Pot Mesa. Blue arrowheads mark access route to topof Pot Mesa. Samples from drill hole USGS SL 10-1 analyzed by USGS palynologist R.H. Tschudy; PPS is location ofoutcrop palynologic sample site of Fassett et al. (2002) and Newman (1987). Topographic map from USGS 1:24,000-scale Star Lake and Pueblo Alto Trading Post Topographic Quadrangle maps.

97


Sullivan et al. (2005)

Sullivan et al. (2005) reviewed “the strati-graphic position of the Cretaceous-Tertiary (K/T)boundary in the San Juan Basin” and included apalynomorph list from the uppermost Kirtland For-mation in the vicinity of Barrel Spring from thesame coaly carbonaceous shale bed as the P4300sample of Figure 51. Their sample was given local-ity number SGL 00-046 (SGL 046 on Figure 51)and contained a list of palynomorphs identified byD.R. Braman (personal commun., 2006) as shownon Table 6. Braman commented as follows regard-ing these palynomorphs:

The above assemblage is made up of mostly species that span the Cretaceous-Tertiary boundary. The exception is Proteacidites retusus and Proteacidites thalmani which are thought to have been two species that went extinct at the boundary (Nichols 1994; Nichols et al. 1992; Nichols et al. 1990). Using this observation then would indicate that the sample is Cretaceous in age. The species occurs in Campanian and Maastrichtian deposits, but the presence of Pandaniidites typicus and Ulmoideipites krempii suggests a Maastrichtian age for the sample. The sample is dominated by bisaccate conifer pollen and the species Tricolpites reticulatus.

This Paper

This paper presents unpublished palynologicdata from Mesa Portales, Pot Mesa, the Ojo Alamotype area, the San Juan River site, and other local-ities.Mesa Portales. Rock samples were collected forpalynologic analyses from within and below the OjoAlamo Sandstone at Mesa Portales (Figure 21) byC.L. Pillmore (USGS) in 1983. These sampleswere submitted to R.H. Tschudy, and the produc-tive samples were given USGS paleobotany local-ity numbers D6582, D6583-A, and D6583-B.Localities 6583-A and B, from the Ojo Alamo Sand-stone are shown on Figures 22 and 23; localityD6582, from the uppermost Fruitland-Kirtland For-mation, is shown on Figure 21. The stratigraphi-cally lowest of the Ojo Alamo samples; D6583-A,was collected to try and narrow the gap in whichthe Cretaceous-Tertiary interface was located onMesa Portales. Tschudy (personal commun., 1983)reported that this sample:

. . . yielded abundant finely divided organic fragments plus fusinite. The sample appears to have been oxidized. Few palynomorphs, difficult to identify, were present. The following were tentatively identified: Tricolpites, Podocarpidites cf. P. sellowiformis, Arecipites, Periporopollenites, Ulmipollenites, Alnipollenites, Lycopodiacidites, Trilete fern spores. This sample did not yield any characteristic Late Cretaceous taxa.Sample D6583-B was collected from the

same bed as sample D3738-B (Figures 22, 23) ofFassett and Hinds (1971). Tschudy reported thatthis sample:

. . . was very poor. Very few palynomorphs were present. . . The presence of Momipites tenuipolus strongly suggests a Paleocene age. We have not observed this taxon in other than Paleocene rocks. Sample D3738-B (Fassett and Hinds [1971] P.P. 676, p. 22) was rechecked and bore some resemblance to this sample but D3738-B although also poor, did not exhibit as much evidence of oxidation.Sample D6582 was collected from a light-gray

claystone about 100 mm below the base of the OjoAlamo Sandstone on the east side of Mesa Por-tales (Figure 21). Tschudy stated that:

This sample was oxidized and very poor. Fusinite and oxidized organic material were present, but very few palynomorphs. . . The assemblage, though poor, indicates a Late Cretaceous age. Owing to the poor recovery and the condition of the sample, even though no evidence of Paleocene fossils was evident, one should consider the possibility that the Cretaceous fossils might have been redeposited in Paleocene rocks.The palynomorphs identified from localities

D6582, D6583-A, and D6583-B are listed on Table9 for easier comparison with palynomorph listsfrom other localities on Mesa Portales.

E. M. Shoemaker collected additional rocksamples from the lower part of the Kirtland andFruitland Formations, undivided, for palynologicevaluation in 1983. The samples were processedby R.H. Tschudy in 1984, and the three productivesamples were given USGS paleobotany locality

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numbers D6626-A, -B, and -C (Figures 22, 23).Table 9 lists the palynomorphs identified at each ofthese localities. In his commentary regarding thesignificance of these palynomorph assemblages,Tschudy (personal commun., 1984) stated:

The palynomorph assemblages from the above three samples were virtually identical. They indicate a Cretaceous age for the samples but not a latest Cretaceous age. The taxa Pristinuspollenites, Rugubivesiculites, Trudopollis, Accuratipollis, and Pseudoplicapollis in particular have not been observed in post-Campanian rocks from the Western Interior but are commonly found in rocks of that age. I am confident that these samples are no younger than Late Campanian. This evaluation is supported by the presence of Aquilapollenites spp., Proteacidites - large, abundant, Araucariacites, and Aequitriradites, taxa with a greater stratigraphic range, but uncommon in terminal Cretaceous rocks. The presence of Botrycoccus, Lecaniella, Pediastrum (algae) and Balmeisporites (a water fern) indicates lacustrine deposition. The few dinoflagellate and hystrichosphere cysts probably were redeposited from older marine rocks.In 1985, the author collected a sample from

USGS paleobotany locality D6878 from a thin coalbed in the lower part of the Nacimiento Formationabout 50 m above the top of the Ojo Alamo Sand-stone (Figure 21, Table 9). D.J. Nichols (personalcommun., 1994) reported that this sample “yieldedabundant sapropel and inertinite along with palyno-morphs.” Nichols concluded that: “Based on thisassemblage, the sample is Paleocene in age.”Palynomorphs identified from this sample are listedon Table 9.Pot Mesa. As discussed in a previous section ofthis report, palynomorphs from the uppermost Kirt-land Formation were identified at the Pot Mesalocality (Figures 3, 59). One set of samples wasdescribed by Newman (1987), a second set byNichols (in Fassett et al. 2002); and a third set wasanalyzed by R.H. Tschudy (personal commun.,1977). Tschudy’s 1977 list of palynomorphs is pub-lished here for the first time (Table 11 (see TableAppendix, page 124)). Although Newman (1987)did not provide the stratigraphic level or exact loca-

tion of his sample site, he did indicate to the authorin the field (Newman, personal commun., 1984) itsapproximate stratigraphic position and localitywhich is nearly identical to the sample locality ofFassett et al. (2002), 9 m below the base of the OjoAlamo, and labeled PPS on Figure 59. (As statedabove, Newman thought his Pot Mesa sample wasfrom the Ojo Alamo Sandstone at the time he col-lected it.)

R.H. Tschudy (personal commun., 1977) pro-vided palynomorph identifications from drill-coreand cuttings samples from a drill hole on top of PotMesa (Figure 59). The hole USGS SL 10-1 wasdrilled by the USGS in 1975 to evaluate FruitlandFormation coal resources in this area. (A geophysi-cal log and description of the lithology of the drillhole are in Jentgen and Fassett 1977.) An attemptwas made to core this drill hole from the depths of4.5 m to 30 m (15 to 97 ft), however, swellingshales between the depths of 10 m and 20 m (32and 65 ft) prevented that part of the hole frombeing cored. The drill hole started in the Ojo AlamoSandstone at the surface and ended in the Pic-tured Cliffs Sandstone (Figure 60). The basal con-tact of the Ojo Alamo was at a depth of about 10 m(32 ft). Unfortunately, samples from the Ojo AlamoSandstone part of the core were barren, and allpalynomorph-productive samples came from theKirtland and Fruitland Formations. The author waspresent at the time this hole was drilled and col-lected the samples from this drill core, which wereanalyzed by Tschudy.

Table 11 lists the palynomorphs identified byTschudy (personal commun., 1977) from samplesfrom drill hole USGS SL 10-1; this table is in theformat presented by Tschudy in his report. The fiveproductive samples were given USGS paleobotani-cal locality numbers; D5783-A, -B, -C, -D, and -E(Table 11, Figure 60); sample depths are providedon table 11. Samples D5783-A, -B, and -C werefrom drill core; the other two samples were fromdrill cuttings. The two uppermost samples and thelowermost sample were the most productive ofpalynomorphs; the two middle samples producedsparse numbers of palynomorphs. All five of thesamples were productive of the Cretaceous indexfossil Tschudypollis (Proteacidites on Table 11). Inhis discussion of these samples, Tschudy stated:

The genus Proteacidites is present in the Cretaceous but has not been found in the Paleocene in any samples from the Rocky Mountain region. On this basis I would place the Cretaceous-Tertiary boundary between 93.8 feet and 94.5

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feet. However, the samples from these two levels are so similar in their palynomorph recovery, that I suspect that the sample from 93.8 feet is also of Cretaceous age. Both of these samples yielded many taxa common to the Cretaceous, but generally foreign to the Paleocene. Furthermore, no clearly Paleocene taxa were found in the sample from 93.8 feet.At the author’s request, Tschudy later re-

examined his slides for the samples from the PotMesa drill hole and revised his earlier findings forthese samples stating the following (Tschudy, per-sonal commun., 1981):

At your request I re-examined the slides reported on in 1977 from Star Lake Drill hole 10-1. I made a serious error. On re-examination I found Proteacidites pollen on the original slides. The grains were few and light colored, but I shouldn’t have missed them, however, they are definitely present for all to see. Thus the uppermost sample from 93.8 feet (D5783-A) becomes palynologically Cretaceous.Furthermore, all but 3 taxa found in the uppermost samples were present in the next lower sample (D5783-B) which I originally designated as Cretaceous. The three taxa are Liliacidites, Azolla and Pterospermopsis, forms that we now know to exist in both the Cretaceous and Tertiary. Pollen grains that are present in the uppermost Cretaceous such as Gunnera and “Tilia wodehouseii” were not found in these samples. On the basis of the current information I believe that these samples are not near the Cretaceous-Tertiary boundary, but from lower in the Cretaceous, possibly as low as the upper Campanian.Thus, the total palynomorph assemblage from

drill-hole samples at Pot Mesa indicates that all ofthe Maastrichtian stage and possibly the upper partof the Campanian stage are missing from the Kirt-land Formation below the upper Kirtland sandstonebed shown on Figure 60.

Table 12 (see Table Appendix, page 125) liststhe palynomorphs identified by Tschudy, Nichols,and Newman from the Pot Mesa locality. Newman(1987, p. 159) stated that his Pot Mesa palyno-morph assemblage indicated a “. . . Maastrichtian

Merrion Oil and Gas Corporation Pot Mesa No. 2SWSWNE Sec. 10, T. 20 N., R. 6 W.

PicturedCliffs Ss tongue

PicturedCliffs Ss

USGS D6879 & Newman (1987),projected level of outcrop samples; “latest Cretaceous”

USGS D5783-A, B, C; drill-coresamples; “upper Campanian”

USGS D5783-D, E; drill-coresamples; “upper Campanian”

Kirtland Fm.

U. Kirt.Ss bed

OjoAlamo Ss

Naci-miento Fm.

coal beds

coal bed

Fruitland Fm tongue

HBB

LewisShale

Fruitland Fm.

1000

900

800

700

600

500

400

300

200

?

100

Figure 60. Geophysical log from drill hole Pot Mesa No.2, top of Pot Mesa (Figure 59), showing formationboundaries and relative levels of samples collected forpalynologic analyses; sample levels projected fromactual locations. Log depths in feet. HBB = HuerfanitoBentonite Bed.

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age. So far, it has not been possible to determinewhether the age is early or late Maastrichtian fromthese assemblages.” Nichols (personal commun.,1994) concluded that: “Based on this diverse andwell-preserved assemblage, the sample is clearlyof latest Cretaceous age.” Nichols and Newmanidentified Gunnera in their samples from Pot Mesaand Nichols also reported “Tilia” wodehouseii in hissample from that locality. According to Tschudy(above) both of these forms are “uppermost Creta-ceous” index fossils. In his comparison of Gas-buggy-core palynomorphs with palynomorphsidentified below the K-T boundary in the RatonBasin, Tschudy (1973) showed “cf Tilia woodhou-sei” was present in the uppermost Cretaceous ofthe Raton Basin but absent in the highest Creta-ceous strata of the Gasbuggy core (Figure 54).Thus, palynologic data at Pot Mesa indicate thepossible presence of an unconformity at the baseof the upper Kirtland sandstone bed (Figure 60)separating Campanian strata from Maastrichtianstrata. The existence of this unconformity is furtherevidenced by the fact that even though the strati-graphic levels of palynomorph samples above andbelow the upper Kirtland sandstone bed are only12 m apart (Figures 60, 33), only about 9 % ofthe palynomorph taxa are common to the palyno-morph lists for these two samples. These data sup-port the presence of the hiatus shown at the PotMesa locality at drill-hole 5 on Figures 34 and 35 atthe base of the upper Kirtland sandstone bed.Ojo Alamo Sandstone Type Area. Unpublishedlists of palynomorphs identified by R.H. Tschudyand D.J. Nichols in and near the Ojo Alamo Sand-stone type area are presented on Tables 13.1 and13.2. These USGS paleobotany localities areshown on Figures 1, 2, 4, and 51. Samples rangein stratigraphic position from the lowermost Fruit-land Formation (sample D6902, about 12 m abovethe base) to the uppermost Kirtland Formation forthe Moncisco Mesa sample (just below the KirtlandFormation—Ojo Alamo Sandstone contact); astratigraphic spread of about 370 m (Figure 33).Samples from localities D6900 and D6902 (Table13.1, Figure 3) (see Table Appendix, page 126)were collected by J.D. Obradovich (USGS) in 1984and analyzed by R.H. Tschudy (personal commun.,1985). The Moncisco Mesa sample (Table 13.1,Figure 3) was collected by C.J. Orth in 1982 andanalyzed by Tschudy for its palynologic content.The complete report for this sample is not avail-able, but a summary of Tschudy’s report is con-tained in an undated communication from Orth(1983?, written communication); the palynomorphs

listed in that summary are shown on Table 13.1.Tschudy concluded that the palynomorph assem-blage from the Moncisco Mesa sample was an:“Assemblage equivalent to those in Vermejo Fm [inthe Raton Basin]. Age represented is Campanianor early Maastrichtian.”

The sample from locality D9157 (Table 13.1,Figures 4, 33) is 55 m below the Kirtland Forma-tion—Ojo Alamo Sandstone contact. D.J. Nicholsanalyzed this sample and reported (personal com-mun., 2000) that its palynomorph assemblage wasearly Maastrichtian. Samples D8179 and D8180(Table 13.1, Figures 4, 33) were collected from theuppermost Kirtland Formation. Sample D8179-Awas from a carbonaceous shale bed about 0.6 mbelow the base of the Ojo Alamo; sample D8179-Bwas collected from the same bed, but about 10 meast of the D8179-A locality. Sample D8180 wascollected from an organic-rich mudstone bed about3 m below the D8179-sample level. Nicholsreported (personal commun., 1995) that thesesamples yielded sparse assemblages of palyno-morphs. Because so few palynomorphs were iden-tified from each of these samples. They are listedin a composite list on Table 13.1. Nichols con-cluded that this assemblage was Late, but not lat-est Cretaceous in age.

The palynomorph lists on Table 13.2 were allprovided by D.J. Nichols (personal commun., 2000,2003). Samples D9156-A and D9156-B (Figure 51)were collected from the same carbonaceous mud-stone bed about 2 m below the Kirtland—OjoAlamo contact. Nichols concluded that these twoassemblages indicate an early Maastrichtian age.Samples from localities 82403-A, 82303-D, and82303-E (Figure 51) were collected from a trenchexcavated through the base of the Ojo AlamoSandstone and into the uppermost Kirtland Forma-tion; the trench locality is shown on Figures 51 and61.

This trench was excavated to try to relocatethe bed from which the D6901 palynomorphassemblage (Table 6) had been collected in 1985in the same area. (An earlier attempt to locate thatbed by trenching in the vicinity of sample sitesP4300 and SGL 046 (Figure 51) was not success-ful, as discussed in Fassett et al. 2002, p. 318-321.) The D6901 sample locality (referred to as the24-5 locality in Fassett et al. 2002) is importantbecause it produced a Paleocene palynomorphassemblage that confirmed the Paleocene age ofthe Ojo Alamo Sandstone in the Ojo Alamo Sand-stone type area. Figure 61 is an annotated photo-graph of the Barrel Spring area showing the

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location of the trench on the left side of the photo-graph at the base of the Ojo Alamo Sandstone.The approximate location of the original D6901sample site is shown to the left of the trench on thisFigure.

Figure 62 is an annotated photograph of theentire trench, showing the stratigraphic level (4 mbelow the base of the Ojo Alamo Sandstone) ofsample 82403-A. (Palynomorphs identified fromthis sample are listed on Table 13.2.) This sampleis at about the same level as the coaly, carbona-ceous shale bed shown on Figure 61 from whichsamples P4300 and SGL 046 (Table 6) were col-lected further to the west (Figures 51, 61). The thin,coaly layer is not present in the trench because itpinches out to the east, as shown on Figure 61.Nichols (personal commun., 2003) concluded thatthe palynomorph assemblage from sample 82403-A was early Maastrichtian in age.

Figure 63 is a close-up view of the uppertrench of Figure 62 showing the locations of allsamples that were collected for palynologic studyhere. Sample 82303-E, according to Nichols con-

tained a “diverse and well-preserved assemblageof fossil pollen and spores.” (Table 13.2) He con-cluded that this assemblage indicated an earlyMaastrichtian age. Nichols reported that sample82303-D “appears to have been weathered inplace such that only a few robust palynomorphspecies survived; species identified have no bio-stratigraphic value; assemblage also includescysts of freshwater algae (also lacking biostrati-graphic value).” The three palynomorphs identifiedby Nichols from this sample are Ghoshispora sp.,Pityosporites sp., and Taxodiaceaepollenites hia-tus.

All of the other samples collected from theupper trench shown on Figure 63 were barren ofpalynomorphs, thus this attempt to relocate thebed from which the D6901 sample was collectedwas not successful. The level of that bed must bebetween sample 82303-E and the base of the OjoAlamo Sandstone and is probably within the thininterval between the yellow-dashed line and thebase of the Ojo Alamo. It is suggested that the Cre-taceous-Paleocene interface may be located at the

KIRTLAND FORMATION

De-na-zin Wash

P4300, SGL 046

Carbonaceous shale bed

Coaly layer

Base of Ojo Alamo SS

Pinch-out ofcoaly layer

D6901(aprox.)

Trench

OJO ALAMO SANDSTONE

Figure 61. Photograph of Barrel Spring locality on De-na-zin Wash, looking southwest. Figure 51 shows map loca-tions of paleobotany localities shown on photograph; localities 82303-E, 82403-A, and 110303-D are in trench on leftside of photograph. Basal contact of Ojo Alamo Sandstone shown with red line (solid where clearly exposed, dottedwhere covered).

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yellow-dashed line on Figure 63. The pre-Paleo-cene unconformity, which, as discussed above,represents a 7.8 m.y. hiatus, is probably on an ero-sion surface on top of the harder and more mas-sive blue-black strata shown beneath the yellow-dashed line on Figure 63. The squeeze-ups seenat the base of the Ojo Alamo Sandstone are a clear

indication that the sediments between the Paleo-cene interface and the base of the Ojo Alamo musthave been unconsolidated and at least somewhatfluid at the time that the first high-energy streamscarrying the gravels of the lower Ojo Alamo Sand-stone flowed across the pre-Ojo Alamo erosionsurface and rapidly built up to a thickness of sand

OJO ALAMO SANDSTONE

KIRTLAND FORMATION

Sample82403-A

Upper trench

Figure 62. Photograph of trench cut through base of Ojo Alamo Sandstone and uppermost Kirtland Formation at Bar-rel Spring locality. Figure 61 shows location of trench. Sample locality 82403-A is about 4 m below base of Ojo AlamoSandstone at about same stratigraphic level as coaly bed that pinches out east of here (Figure 61). Contact betweenOjo Alamo Sandstone and Kirtland Formation shown by red line (solid where clearly visible, dotted where covered).Geologic pick 0.33 m long.

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104

OJO ALAMO SANDSTONE

KIRTLAND FORMATION82303-AA

110303-B

110303-B

82303-A

82303-C

82303-D

82303-E

82303-B

Diverse palynomorphs Sparse palynomorphs Barren of palynomorphs

Figure 63. Photograph of upper part of trench of Figure 62; distance from base of Ojo Alamo Sandstone to samplelocality 82303-E is 1.7 m.; geologic-pick length 0.33 m. Note intense, soft-sediment deformation at base of Ojo AlamoSandstone, including distinct squeeze-up of uppermost Kirtland Formation mudstone forced up into basal Ojo AlamoSandstone conglomerate in top-center of photograph. Such rapid-loading features are also visible below base of OjoAlamo in center of Figure 61. Palynologic sample localities in carbonaceous mudstone bed in uppermost Kirtland areshown. All samples, except 82303-D and 82303-E, barren of palynomorphs. Yellow-dashed line is subtle contactbetween harder, more massive, blue-black shale below and softer, more thin-bedded, gray mudstone above. Yellow-dotted line is another subtle contact at base of blue-black shale bed. One of these contacts (probably upper one) isthe Cretaceous-Paleocene interface.


and gravel of sufficient weight to cause the bed dis-tortion seen on Figures 61, 62, and 63 at the baseof the Ojo Alamo.

The thin gray unit below the base of the OjoAlamo Sandstone (Figure 63) may be the bed fromwhich the D6901 sample was collected in 1985east of the trench in a place where palynomorphswere better preserved. This interval probably rep-resents a soil layer or swamp deposit that filled alow-lying area on the pre-Paleocene erosion sur-face in early Paleocene time. The few Cretaceouspalynomorphs found in the D6901 palynomorphassemblage could easily have been washed orblown into this layer from the adjacent Cretaceousland surface, as discussed in Fassett et al. (2002,p. 318-319). It is possible, although less likely, thatthe Cretaceous-Tertiary interface is at a lower levelin the upper trench, somewhere above sample82303-E (Figure 63). There is another (subtle) lith-ologic break at the base of the blue-black massiveshale bed marked by a thin greenish-gray siltylayer just below the level of sample 82303-C (yel-low-dotted line on Figure 63) and perhaps the baseof this unit represents the K-T interface. There areno other apparent lithologic breaks in the intervalbetween samples 82303-C and 82303-E in thestrata exposed in the trench.

Sullivan et al. (2005) disputed the presence ofPaleocene dinosaurs in the Ojo Alamo Sandstoneof the San Juan Basin. These authors argued thatthe Paleocene age of the Ojo Alamo Sandstone onthe basis of palynological data obtained in the Bar-rel Spring area (palynologic sample D6901, Table6), published in Fassett et al. (2002), was invalidbecause they could not replicate those data; theystated (p. 402) that their “processing of severalsamples yielded no identifiable palynomorphs.”Sullivan et al., however, did not specify whereexactly their sampling had been done, did not sup-ply photographs of their sample sites, or state howmany samples had been collected and analyzed. Itis here suggested that this vague reference tosampling from an unknown locality at an unknowndistance below the base of the Ojo Alamo Sand-stone with the results being samples barren ofpalynomorphs does not obviate the data reportedby Fassett et al. (2002). Those data contained theresults of palynologic analysis of a rock samplefrom a specifically identified locality, less than 1 mbelow the base of the Ojo Alamo, that contained adiverse palynomorph assemblage of Paleoceneage. As demonstrated in the discussion above,samples barren of palynomorphs have been frus-tratingly common throughout the San Juan Basin

(see Figure 63), however, rock samples barren ofpalynomorphs, from whatever locality, have nogeochronologic value to prove or disprove any-thing.

In addition, Sullivan, Lucas, and Braman(2005, p. 402) stated that they found “no physicalevidence of an unconformity . . . of at least 7.5 mil-lion years” in uppermost Kirtland Formation stratain the Barrel Spring area. Unconformities can besubtle, and it is here suggested that because theseauthors did not carefully trench the interval in theuppermost Kirtland up to the base of the Ojo AlamoSandstone in the Barrel Spring area, they did notobserve the subtle lithologic changes shown onFigure 63 and discussed in detail above. The rocksof the uppermost Kirtland Formation, immediatelybeneath the Ojo Alamo Sandstone in the OjoAlamo Sandstone type area, are 73.04 Ma basedon a 40Ar/39Ar single-crystal sanidine age. In addi-tion, palynomorphs identified from multiple rocksamples from within and immediately below theOjo Alamo Sandstone in the Barrel Spring areahave an early, but not earliest Paleocene age. (SeeFigure 58 for a depiction of these relations.) There-fore, an unconformity of about 7.8 m.y. must bepresent at or near the base of the Ojo Alamo in thisarea, even though this hiatus is not, at first glance,physically apparent.

Sample 110303-D was collected from a coaly,carbonaceous shale bed about 0.3 m below thebase of the Ojo Alamo Sandstone at a locality 225m east of the trench locality (Figure 51). Accordingto Nichols, this sample also yielded a diverse andwell-preserved assemblage (Table 13.2) of earlyMaastrichtian age. At this locality, the K-T interfaceis apparently at the base of the Ojo Alamo Sand-stone. This finding supports the suggestion abovethat the Paleocene rocks in the uppermost KirtlandFormation in the Barrel Spring area (Figure 63)represent sedimentation in an isolated bog or pondpresent on the Paleocene erosion surface justbefore deposition of the overlying Ojo Alamo Sand-stone conglomerates began. The squeeze-ups ofthis unconsolidated and somewhat fluid material(Figure 63) into the basal part of the Ojo Alamo arediagnostic of these Paleocene bog deposits thatfilled isolated low spots on the pre Ojo AlamoSandstone erosion surface.

The palynomorphs listed in the columnheaded: “Locality D6901” (“archival split 24-5”) onTable 14 (see Table Appendix, page 127), wereidentified by D.H. Nichols (personal commun.,2003) from a new analysis of a sample reported byNichols to be a split of USGS archival sample 24-5

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(from USGS Paleobotany Locality 6901, Figure56). The label “24-5” is from Fassett et al. (2002).The palynomorph assemblage from the “archivalsplit” appears to differ markedly from the assem-blage identified from the original analysis of thissample (column headed “Locality D6901 (sample24-5)” on Table 14). There are only 12 commonpalynomorphs (33%) out of the 36 palynomorphsidentified from these two sample preparations, and24 palynomorphs (67%) are not common. A com-posite list of palynomorphs from USGS localitiesD6877-A, -B, and -C from the San Juan Riverlocality (Figure 1) has also been added to Table 14for comparative purposes. This Paleocene assem-blage has a greater degree of commonality ofpalynomorphs with the original D6901 list thandoes the “archival split”: 15 common palynomorphsout of 36 (42%) vs. 19 not-common (58%). Thishigher percentage of common palynomorphs iseven more remarkable in consideration of the factthat these two sample localities are nearly 50 kmapart. The low percentage of commonality ofpalynomorphs (33%) from sample D6901 and“archival split 24-5” (reported to be from the originalD6901 sample) casts serious doubt as to whetherthese two palynomorph lists actually came fromsplits of the same sample. It is suggested that“archival split 24-5” may have come from a differ-ent USGS archival sample from Cretaceous strataand not from the original “24-5” sample.Northeast San Juan Basin. The locations of thefour palynologic samples from the northeast part ofthe San Juan Basin are shown on Figure 1.Palynomorphs identified by R.H. Tschudy from theD4119 locality were published in Fassett and Hinds(1971) and are listed on Table 7 (they are alsoshown on Table 15 (see Table Appendix, page 128)with the three other palynomorph lists from thenortheastern San Juan Basin). The other threesamples (D5393, D5394, and D5408) were col-lected by R.T. Ryder in 1975 and were reported onby Tschudy (personal commun., 1976). Two ofthese samples (D5393 and D5394) were collectedfrom the lowermost part of the Fruitland Formation:D5393 was from a mine dump from a coal bed 6 mabove the base of the Fruitland and D5394 wascollected from a bed 3 m above the base of theFruitland near an outlier (Klutter Mountain) of Pic-tured Cliffs Sandstone, Fruitland Formation, andOjo Alamo Sandstone (Figure 1) about 19 km eastof locality D5393. The D4119 locality, also from acoal bed a few meters above the base of the Fruit-land, is located about 9 km southeast of the D5393

locality (Figure 1). Tschudy wrote of the palyno-morph assemblage from locality D5393:

This assemblage is clearly of Late Cretaceous age. The estimation of lower Fruitland is consistent with the palynomorphs found. Kuylisporites has not been found in rocks younger than middle Campanian and is present in the lower part of the Fruitland Formation in the Gasbuggy core. For the D5394 assemblage, Tschudy reported

that:This assemblage is of Late Cretaceous Campanian age. All taxa have been found previously in the Fruitland Formation. The presence of Phaseolidites stanleyi suggests lower Fruitland, but I am unable to restrict the assemblage to the lower part of the Fruitland.Tschudy’s comments in Fassett and Hinds

(1971, p. 21) regarding sample D4119 are:Sample D4119 I believe to be Cretaceous. The coal yielded a poor corroded assemblage. I was able to find only two specimens of the marker genus Proteacidites. This assemblage appears to have a closer resemblance to the Trinidad and Vermejo of the Raton Basin than to the assemblage reported by Anderson from the southern San Juan Basin.As Table 15 indicates, the three palynomorph

lists for samples from the lowermost Fruitland For-mation in the northeastern San Juan Basin, all rela-tively close together, have remarkably few commontaxa. This would seem to indicate that local envi-ronmental conditions had a profound affect on theplant assemblages even at closely spaced locali-ties; at least in this part of the San Juan Basin.

The fourth palynomorph list on Table 15 is forsample D5408; this sample was collected from theAnimas Formation about 150 m above its base(Figure 1). Tschudy (personal commun., 1975)wrote that this sample:

. . . yielded a very sparse palynomorph flora . . . The presence of these two species of Momipites [Table 15] in an otherwise very poor assemblage, definitely indicates a Paleocene age for the sample.

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Composite Palynomorph Lists by Locality

Mesa Portales and Anderson’s Localities NearCuba, New Mexico. Table 16 (see Table Appen-dix, page 129) shows composite palynomorph listsfor the southeastern part of the San Juan Basin,including all of the palynomorphs identified at andnear Mesa Portales (Tables 7 and 9 ) and in Ander-son (1960, table 1), Table 5. These lists consist ofpalynomorphs identified from the Fruitland andKirtland Formations, the Ojo Alamo Sandstone,and the Nacimiento Formation. There are 144 taxalisted on Table 16; of these only 12 (9%) are com-mon to the Cretaceous Fruitland-Kirtland Forma-tions and the Paleocene Ojo Alamo Sandstone. Atfirst glance this evidence would seem to indicatean enormous die-off of plants at the K-T interface inthe southeastern part of the basin. However,because of the 7.8m.y. hiatus at the K-T boundary,representing all of Maastrichtian, part of Campa-nian, and also a small part of earliest Paleocenetime, this apparent sudden die-off actually repre-sents species that died off over a nearly 8 m.y.period and not suddenly at the end of the Creta-ceous. There are 72 taxa in Paleocene strata listedon Table 16; 22 taxa (31%) are common to the OjoAlamo Sandstone and Nacimiento Formation.There was apparently continuous depositionacross the contact between these formations (Fas-sett 1966), consequently this relatively small per-centage of common forms probably indicates adistinct change in depositional environments in thisarea from Ojo Alamo to Nacimiento time. There are37 taxa listed on Table 16 from the Nacimiento vs.57 for the Ojo Alamo, thus, this disparity in num-bers of taxa preserved and identified from thesetwo formations may be skewing this percentage.Pot Mesa Locality. The composite list of palyno-morphs identified from the Pot Mesa locality (Table17, Figures 59, 60) (see Table Appendix, page130) are all from the Cretaceous Kirtland Forma-tion. No samples collected for palynologic analysisfrom the Paleocene Ojo Alamo Sandstone at PotMesa were productive. There are 58 taxa shownon the palynomorph list on Table 17. Ojo Alamo Sandstone Type Area. Table 18 (seeTable Appendix, page 131) shows compositepalynomorph lists for the Ojo Alamo type area andnearby areas to the west (Figures 1, 3, and 4).Table 18 lists 112 taxa; of these, 11 of 81 taxa(14%) are common to the Fruitland and KirtlandFormations, 17 of 73 taxa (23%) are common tothe Kirtland and the Paleocene uppermost Kirtland,13 of 52 taxa (25%) are common to the uppermost

Kirtland and upper Ojo Alamo, and 5 of 37 taxa(14%) are common to the upper Ojo Alamo Sand-stone and lower Nacimiento Formation. Creta-ceous taxa total 81, and Paleocene taxa total 52.San Juan River Locality. The palynomorphs listedon Table 19 (see Table Appendix, page 132) fromthe San Juan River locality were all originallyreported to be from the Ojo Alamo Sandstone,however, as discussed above, the palynomorphsidentified by Newman (1987) from that localitywere probably not collected from the Ojo Alamo butwere probably from the underlying Kirtland Forma-tion. For this reason, Newman’s palynomorph list isshown to be from the Cretaceous Kirtland Forma-tion on Table 19. There are 48 taxa listed on thistable; six are from the Kirtland Formation, and 43are from the Ojo Alamo Sandstone. The only com-mon palynomorph to the two lists is Tschudypollisand because palynomorph assemblages identifiedfrom the Ojo Alamo Sandstone are Paleocene inage, the specimens of Tschudypollis in the OjoAlamo Sandstone are considered to be reworked.(See discussion of reworking of Cretaceouspalynomorphs into Paleocene strata in Nichols andFleming 2002.)Northeast San Juan Basin. Table 20 (see TableAppendix, page 133) lists the palynomorphs identi-fied from the northeastern part of the San JuanBasin from the lowermost Fruitland Formation andfrom the lower part of the Animas Formation. Ofthe 36 taxa listed, only two (6%) are common to theFruitland and Animas Formations. This low per-centage of commonality is clearly skewed by thesmall number (6) of palynomorphs identified fromthe Animas in this area.

Palynomorph Lists by Formation

Fruitland Formation. Table 21 (see Table Appen-dix, page 134) contains composite lists of palyno-morphs from four areas in the San Juan Basin.Two areas—the Ojo Alamo type area and the MesaPortales area—are in the southern part of thebasin, and two areas—the Gasbuggy core and thenortheastern San Juan Basin area are in thenorthern part of the basin. Of the 155 taxa listed onTable 21, there is a low percentage of commontaxa between these areas; the Ojo Alamo typearea and the Mesa Portales areas only have sixpalynomorphs in common (5%) out of 110 taxafrom those two areas. This low percentage is prob-ably skewed by the different numbers of taxa iden-tified from these two areas: 29 from the Ojo Alamotype area and 87 from the Mesa Portales area. TheMesa Portales and Gasbuggy core lists have 18 of

107


121 taxa in common (15%). The Gasbuggy coreand the northeast San Juan Basin lists have 12 of106 taxa in common (11%). These relatively lowpercentages of commonality of palynomorphs forFruitland Formation assemblages suggest thatdepositional environments were variable acrossthe basin during Fruitland Formation time. More-over, the time-transgressive nature of FruitlandFormation strata—becoming about 2 m.y. youngerfrom southwest to northeast across thebasin—probably contributed to the lack of com-monality for assemblages in the southwest andnortheast.Kirtland Formation. Palynomorphs collected fromthe Kirtland Formation were identified from only thetwo localities shown on Table 22 (see Table Appen-dix, page 135). The Pot Mesa area is 62 km south-east of the Ojo Alamo type area (Figure 3). TheFruitland-Kirtland interval is about 145 m thinner atPot Mesa than at the Ojo Alamo type area, thuspalynomorphs collected from the upper part of theKirtland Formation at Pot Mesa are about 145 mstratigraphically lower than the upper-Kirtland sam-ples from the Ojo Alamo type area. The Pot Mesasamples from upper Kirtland strata are thus consid-erably older than those from the Ojo Alamo typearea. That is probably the reason why there areonly 11 common taxa (10%) out of a total of 108palynomorphs identified from the two localities.Comparison of Fruitland and Kirtland Forma-tions Palynomorphs. Table 23 (see Table Appen-dix, page 136) lists 206 palynomorph taxaidentified from the Fruitland and Kirtland Forma-tions from all localities in the San Juan Basin. Ofthese, 46 taxa (22%) are common to the Fruitlandand Kirtland Formations. Of the 206 total taxa, 106are present only in the Fruitland, and 53 are pres-ent only in the Kirtland. The Cretaceous indexpalynomorph Tschudypollis spp. is ubiquitous andthe most abundant form in all Fruitland and Kirtlandsamples. A preliminary zonation of the Fruitland-Kirtland is presented in the “Cretaceous-Palyno-morph Zonation section” of this appendix, below.Ojo Alamo Sandstone. The Paleocene Ojo AlamoSandstone and the Paleocene (uppermost) parts ofthe Kirtland and Fruitland Formation have yielded101 palynomorphs in the San Juan Basin (Table24) (see Table Appendix, page 137). Table 25 (seeTable Appendix, page 138) shows that the OjoAlamo Sandstone and underlying Cretaceousrocks have yielded 243 taxa between them; ofthese taxa, 192 are restricted to Cretaceous strata,51 are common to Cretaceous strata, and 51 were

found only in Paleocene strata. (The two occur-rences of reworked Tschudypollis shown on Table24 are not included in these numbers.) A compari-son of Cretaceous and Paleocene palynomorphswithin the San Juan Basin and with other WesternInterior basins is presented in the section of thisreport labeled “Comparison of Palynomorphs,”below.

The guide palynomorphs, Brevicolporitescolpella and (or) Momipites tenuipolus have beenidentified from Ojo Alamo Sandstone samples atnumerous localities in the San Juan Basin.

These palynomorphs are known to berestricted to Paleocene-age strata throughout theWestern Interior of North America (Nichols andJohnson 2002). Nichols (2002) discussed the sig-nificance of M. tenuipolus as a Paleocene indexfossil throughout the Western Interior. Nichols (p.124), and in his discussion of biozone P1 in theRaton Basin, stated that:

Momipites tenuipolus and M. leffingwellii occur only in the middle to upper part of the biozone [P1], thereby delimiting a basal Paleocene subzone in which M. inaequalis is present but the other species of Momipites are absent. This basal Paleocene subzone of Zone P1 is recognizable in the Denver Basin, as well.This finding is in accord with statements by

R.H. Tschudy in numerous reports to the author(written communs. cited above) that M. tenuipolus“is limited to the Paleocene but is not present in thelowermost Paleocene” in the San Juan Basin. Inhis conclusions, Nichols (2003, p. 130-131)emphasized that:

With attention to the influence of paleolatitude, local zonations can be integrated into a comprehensive nonmarine biostratigraphy for the lower Cenozoic of the Rocky Mountains and Great Plains region.The Raton Basin of northeastern New Mexico

and southeastern Colorado is only 230 km east ofthe San Juan Basin and is at the same latitude. It isthus reasonable to conclude that in the San JuanBasin, M. tenuipolus is also restricted to the upperpart of biozone P1 and is absent from lowermostPaleocene rocks. M. tenuipolus has been identifiedfrom a sample less than a meter below the base ofthe Ojo Alamo Sandstone in the Ojo Alamo typearea and 8 m above the K-T interface at Mesa Por-tales. Because M. tenuipolus is only present in the

108


upper part of zone P1, it can thus be concludedthat the lowermost part of zone P1 (the lowermostPaleocene) is missing in the San Juan Basin. Thisfinding agrees with paleomagnetic data indicatingthat the base of the Ojo Alamo Sandstone has anage of about 65.2 Ma (see Figures 34 and 35) sug-gesting a 0.3 m.y. gap in the lowermost Paleocenein the southern part of the San Juan Basin.Nacimiento Formation. Palynomorphs identifiedfrom the Paleocene Nacimiento and Animas For-mations are listed in Table 26 (see Table Appendix,page 139). Samples from these formations at ninelocalities in the San Juan Basin yielded 69 identi-fied palynomorphs; sample collections ranged fromnear the base to 150 m above the base of theseformations. The two localities labeled “WNW2008—Kimbeto Arroyo” were discussed in William-son et al. 2008. These authors determined that (p.9): “Both palynomorph assemblages, which arereported here, contain palynomorphs that are char-acteristic of early Paleocene assemblages that arewidespread in the Rocky Mountain region.” Thetaxa identified from the samples collected fromstrata 19 m above the base of the Nacimiento For-mation (top of the Ojo Alamo Sandstone) werefound to contain “palynomorphs characteristic ofP1–P3 pollen zones” and the assemblage fromsamples 105 m above the base of the Nacimientocontained “palynomorphs characteristic of P3.” TheP1 through P3 pollen zones mentioned here referto the Paleocene pollen zonation established in thenorthern part of the Western Interior of North Amer-ica by Nichols (2003). The paper by Williamson etal. (2008) is the first to correlate the Paleocenepalynomorph zonation of the northern part of theWestern Interior with palynomorph assemblages inthe southern part in New Mexico.

Williamson et al. (2008, p. 3) identified thepalynomorph Momipites triorbicularis in their sam-ple 105 m above the base of the Nacimiento For-mation and stated that this taxa “is indicative ofpalynostratigraphic Zone P3.” Nichols (2003, figure2), however, shows this guide fossil’s first appear-ance as more specifically being at or near theboundary between the P3 and P4 zones with itsrange extending up into the middle of zone P5.This diagnostic fossil was also identified from asample collected 150 m above the base of the Ani-mas Formation at locality D5408 in the northernSan Juan Basin in Colorado (Table 26). The pres-ence of this palynomorph 45 m above its presencelower in the Nacimiento Formation would thus indi-cate that the strata at this higher level are in zone

P4, and that the P3-P4 boundary is just above thesample 105 m above the base of the Nacimiento.

Nichols (2003, figure 2) shows the boundarybetween biozones P2 and P3 to be between thelast occurrence of M. inaequalis and the first occur-rence of M. triorbicularis. M. inaequalis is present20 m above the base of the Nacimiento at theD3803 locality (Table 26), and M. triorbicularis ispresent at the Kimbeto Arroyo locality 105 m abovethe base of the Nacimiento (Table 26). The bound-ary between zones P2 and P3 must, therefore, bebetween these two stratigraphic levels in the SanJuan Basin—probably not far above the strati-graphic level of M. inaequalis.

Williamson et al. (2008) also pointed out thatthe Paleocene index fossil M. tenuipolus was foundin their lower sample, 19 m above the base of theNacimiento Formation, and Table 26 shows thatthis palynomorph was also found 150 m above thebase of the Nacimiento at the D5408 locality. Asthis table shows, M. tenuipolus is by far the mostcommon palynomorph identified from NacimientoFormation samples and is present in seven of thenine palynomorph lists shown.

Palynomorph lists from the Nacimiento For-mation and the Ojo Alamo Sandstone are com-pared in Table 27 (see Table Appendix, page 140).This table shows that 101 palynomorphs havebeen identified from the Ojo Alamo Sandstone, 69from the Nacimiento Formation, and 49 palyno-morphs are common to both formations. The totalnumber of palynomorphs from both formations is125. Fifty six palynomorphs are present only in theOjo Alamo Sandstone, and 24 are found only in theNacimiento Formation. The high percentage ofcommonality of palynomorphs for the Ojo Alamoand Nacimiento formations attests to uninterrupteddeposition across the boundary between these twoformations. These data thus further reinforce thefindings presented elsewhere in this report that theOjo Alamo Sandstone is Paleocene in age.

Cretaceous-Palynomorph Zonation

Table 28 (see Table Appendix, page 141)shows the zonation of palynomorphs from thelower and upper parts of the Fruitland Formationand the upper Kirtland Formation in the southernpart of the San Juan Basin. As the time-strati-graphic cross sections of Figures 34 and 35 show,Fruitland and Kirtland strata are late Campanian inage in the southwest part of the basin; the upper-most part of the late Campanian and all of theMaastrichtian are missing. Figure 64 shows thestratigraphic positions of these three palynomorph

109


110

c33N

3

5

6

7

8

C32r

C29n .2nC29r

C33n

9

11

12

10

4

29n.1r

C29n .1n

101010

Ash HBB75.76 Ma

13

14

15

A

Ash 274.56 Ma

B

Ash 474.55 Ma

C

D

Ojo Alamo type area

AcanthotriletesAccuratipollisAequitriraditesAlgal cystsAppendicisporites sp.Araucariacites commonAquilapollenites quadrilobusAquilapollenites senonicusAquilapollenites trialatus, var. uniformisArecipitesBalmeisporitesBisacaccate conifer pollenBotryococcusCamarozonosporites ambigensCicatricosisporites sp.CorollinaCupuliferoidaepollenites spp.Cyathidites minorDinoflagellates very fewEchinatisporis varispinosusEphedra sp.Equisetosporites parallel striaeEucommiidites sp.Foveosporites sp.GleicheniiditesHystrichospheres very fewIlexpollenitesInaperturopollenitesLecaniellaLiliacidites leeiMonocolopopollenites? s p.Monosulcites sp.Neoraistrickia sp.Nyssapollenites sp.PediastrumPlicapollis?PristinuspollenitesPseudoplicapollis?Quadripollis krempiiReticuloidosporites pseudomuriiRugubivesiculitesStereisporites spp.TaxodiaceaepollenitesTetracolpitesTschudypollis many, largeTschudypollis retususTschudypollis thalmanniiTilia wodehouseiTricolpopollenites sp.Tricolporites sp.Triporopollenites spp.TrudopollisUlmipollenites krempiiUlmoideipites tricostatusZonalapollenites sp.

Lower Fruitland palynomorphs

Upper Kirtlandpalynomorphs

HuerfanitoBentonite Bed

Lewis Shale

Pictured CliffsSandstone

Upper Fruitland palynomorphs

AbietineaepollenitesCamarozonosporites ambigensCicatricosisporites sp.Corollina torosaCupuliferoidaepollenites spp.Cyathidites spp.DinoflagellateEchinatisporis varispinosusEucommiidites minorGleicheniiditesKlukisporitesLaevigatosporites spp.Liliacidites sp.LycopodiaciditesMicrofoveolatosporisMicroreticulatisporites sp.Momipites sanjuanensisNyssapollenites spp.Pseudoplicapollis newmaniiPseudoplicapollisReticuloidosporites pseudomuriiRhoipites sp.RugubivesiculitesStereisporites spp.TaxodiaceaepollenitesTricolpites spp.Triporopollenites tectusTschudypollis spp.Tschudypollis retusus

FruitlandFormation

KirtlandFormation

Ash H73.37 Ma

Ash J73.04 Ma

Base of PmagSection

E

2

Puercanmammal bone

Drill-hole 2

NacimientoFormation

Ojo AlamoSandstone

AbietineaepollenitesAequitriraditesAraucariacites sp.Arecipites reticulatusAzollaBalmeisporitesCorollinaCupaneidites sp.Cyathidites sp.Cycadopites fragillisCycadopites sp.Dyadonapites reticulatusEquisetosporitesErdtmannipollis sp.Eucommiidites sp.ForaminisporisGhoshispora sp.Granabivesiculites sp.GunneraInterpollisKurtzipitesKurtzipites trispissatusLaevigatosporites sp.LiliaciditesLiliacidites hyalaciniatusLiliacidites leeiLiquidambarpollenites sp.LycopodiaciditesLycopodiumsporitesMonoporopollenites sp.MonosulcitesNyssapollenites albertensisOsmundaciditesPandaniidites typicusPeriporopollenitesPityosporites constrictusPityosporites spp.PterospermopsisQuercus explanataSchizosporis parvusTaxodiaceaepollenitesTaxodiaceaepollenites hiatusTricolpites interangulusTricolpites microreticulatusTricolpites reticulatusTricolpopollenites sp.TschudypollisTschudypollis retususTschudypollis thalmanniiTsugaepollenites sp.UlmipollenitesUlmipollenites krempiiUlmoideipites spp.Ulmoideipites tricostatusunidentified trilete sporescf Vitis affluensZlivisporis sp.

F

G

Dinosaur bone

Figure 64. Stratigraphic levels of palynomorph assemblages from Fruitland and Kirtland Formations in Ojo AlamoSandstone type area. Geophysical log from Figure 33, palynomorph lists from Table 28; log explanations on Figure33. Lower Fruitland palynomorphs approximately 75.1 Ma, upper Fruitland palynomorphs about 74.6 Ma, and upperKirtland palynomorphs; samples at D level about 73.0 Ma, and at C level about 73.8 Ma. Majority of upper Kirtlandpalynomorphs from D sample level, just above Ash J level. Palynomorph-assemblage ages interpolated from ash-bed ages shown.


assemblages projected into drill-hole 2 (see Fig-ures 33-35) near the Ojo Alamo Sandstone typearea. Table 28 shows that 34 palynomorphs fromlower Fruitland samples are not present in strati-graphically higher Cretaceous samples, 12 palyno-morphs are common to the lower and upperKirtland samples, and eight palynomorphs arepresent in the lower Fruitland and upper Kirtlandsamples. Eight palynomorphs are unique to theupper Fruitland samples, and 21 palynomorphsidentified from upper Fruitland samples are notpresent in upper Kirtland samples. Eight taxa arecommon to the upper Fruitland and upper Kirtlandsamples, and three are common to all three sam-ple lists. As for upper Kirtland samples, 40 taxa arefound only in these samples.

Table 28 clearly shows the progressive disap-pearance of palynomorphs and the appearance ofnew taxa going stratigraphically upward throughthe Campanian Fruitland and Kirtland Formationsin the San Juan Basin. Of the taxa present in thelower Fruitland palynomorph list of this table, onlytwo genera reappear in Paleocene strata: Araucari-acites as A. australis and Triporopollenites as T.plektosus and T. rugatus (Table 29) (see TableAppendix, page 142). Of the taxa present in thelower and (or) upper Fruitland but absent in theupper Kirtland of Table 28, five genera also appearin the Paleocene: Gleicheniidites as G. senonicus,Momipites sanjuanensis, Nyssapollenites spp asN. explanatus, Tricolpites spp., and Triporopollen-ites as T. tectus and T. plektosus (Table 29).

Comparison of Cretaceous and Tertiary Palynomorphs

Table 29 compares Cretaceous (Campanian)and Paleocene palynomorph assemblages in theSan Juan Basin; 244 palynomorphs are listed onthis table. Of these, 50 taxa (20%) are present onlyin Paleocene strata, 143 taxa (59%) are presentonly in Cretaceous strata, and 51 taxa (21%) arecommon to Cretaceous and Paleocene strata. The23 taxa shown in magenta are Cretaceous indexpalynomorphs in the Raton Basin (Fleming 1990)and (or) the Northern Great Plains (Nichols andJohnson 2002). The palynomorphs shown in blueare Paleocene index fossils in the Raton Basin orNorthern Great Plains. All but one of the Creta-ceous index palynomorphs of the Raton Basin andNorthern Great Plains Tricolpites spp. are absentin Paleocene strata of the San Juan Basin. Taxa,reported to be Cretaceous index fossils in theRaton Basin are present in Paleocene strata atthree different localities in the San Juan Basin.

As Table 29 shows, Brevicolporites colpellaand Momipites spp. are Paleocene index palyno-morphs in the Northern Great Plains (Nichols andJohnson 2002). Fleming (1990, p. 247) stated that:“in the Raton Formation [in the Raton Basin],Momipites tenuipolus first appears 16 m above theK-T boundary in the Momipites inaequalis zoneand ranges to near the top of the formation.” Flem-ing, however, indicated that B. colpella may havebeen identified in Cretaceous strata in the RatonBasin. It would appear that both B. colpella and M.tenuipolus are Paleocene index palynomorphs inthe San Juan Basin. A more detailed comparisonof palynomorph occurrences in the San Juan Basinand other Western Interior basins is made difficultby the fact that in those basins there was appar-ently continuous deposition across the Creta-ceous-Tertiary boundary, whereas in the southernSan Juan Basin, there is a nearly 8 m.y. hiatus atthe K-T interface with all of the Maastrichtian, theuppermost part of the Campanian, and a smallinterval of lowermost Paleocene absent. A compar-ison of palynomorphs found in Campanian strata inthe San Juan Basin (Table 28) with palynomorphassemblages of the same age from other WesternInterior basins would be instructive, but is beyondthe scope of this report.

Summary of Palynology

This appendix synthesizes all publishedpalynologic data for rocks adjacent to the Creta-ceous-Tertiary (K-T) interface in the San JuanBasin, and in addition, presents additional newpalynomorph lists to add to the basin’s publishedpalynologic database. Palynomorphs identifiedfrom the Upper Cretaceous Fruitland and KirtlandFormations are twice as abundant as those fromthe Paleocene Ojo Alamo Sandstone and theNacimiento and Animas Formations. This isbecause the collection sites for Cretaceous sam-ples are much more numerous, the samples fromthe Ojo Alamo have generally yielded far feweridentifiable palynomorphs, and because palyno-morph diversity is apparently less for the OjoAlamo, Nacimiento, and Animas formations.

Composite-palynomorph lists are presented inTables 16 through 25 synthesizing all availablepalynologic data for the San Juan Basin. Tables 16through 20 present composite palynomorph listsfor each locality where such data have beenobtained; Tables 21 through 24 compare palyno-morph lists for Cretaceous and Paleocene strata,and Table 25 lists all palynomorphs identified fromCretaceous and Paleocene strata for the entire

111


basin. Table 26 lists palynomorphs from theNacimiento and Animas Formations, and Table 27compares Ojo Alamo Sandstone with Nacimiento-Animas palynomorphs. Table 28 shows the palyno-logic zonation of uppermost Cretaceous strata, andTable 29 compares the total Cretaceous vs. Paleo-cene palynomorph lists.

The discussions above address the statisticalvariations in numbers of palynomorphs identifiedfrom the formations adjacent to the Cretaceous-Tertiary interface in the San Juan Basin, and repre-sent the empirical observations of a non-palynolo-gist. A much more nuanced interpretation of thesedata could, and should, be made by an experi-enced palynologist. These numbers are skewed bythe variable numbers of sample-collection localitiesin each formation and by variations in the diversityof palynomorphs present in these samples. In addi-tion, going upward in the stratigraphic section fromthe lower Fruitland Formation through the KirtlandFormation (upper Campanian) the depositionalenvironments change progressively from nearshore, swampy conditions, to coastal plane, andultimately to well-drained, continental, fluvial envi-ronments well inland of the Western Interior Sea-way’s regressive shoreline far to the northeast.These different environments undoubtedly contrib-uted to the stratigraphic variations in palynomorphassemblages in the Fruitland and Kirtland and, to adegree, may cloud the evolution, extinction, andfirst occurrences of palynomorphs going upward in

the section. The depositional environments forpalynomorph-sample localities within the OjoAlamo Sandstone and overlying Nacimiento For-mation were probably less variable across thebasin.

The last occurrences of 22 taxa in Cretaceousstrata of the San Juan Basin are in agreement withlast occurrences of these taxa in the Raton Basin(Fleming 1990) and the Northern Great Plains(Nichols and Johnson 2002). These last occur-rences unequivocally mark the Cretaceous-Tertiary(K-T) interface in the San Juan Basin. The lastoccurrence of the principle Cretaceous index fossil:Tschudypollis (formerly Proteacidites); sharplydefines the K-T interface in the southeastern SanJuan Basin at Mesa Portales, in Anderson’s (1960)collecting localities and in the Gasbuggy core. Inaddition, the Paleocene index palynomorphs Brevi-colporites colpella and Momipites tenuipolus havebeen identified in the Paleocene Ojo Alamo Sand-stone (and the Paleocene part of the uppermostKirtland Formation) at two localities in the SanJuan Basin. Because M. tenuipolus is restricted tothe upper part of biozone P1 and is not present inlowermost Paleocene strata in the Western Interiorof North America (Nichols 2003), the presence ofthis guide fossil in the lowermost part of the OjoAlamo Sandstone supports paleomagnetic evi-dence suggesting that as much as 0.3 m.y. are notrepresented by Paleocene rocks in the San JuanBasin.

112

TABLE 1. AGES OF SOME LATE CRETACEOUS WESTERN INTERIOR AMMONITE- ZONE BOUNDARIES OF GRADSTEIN ET AL. (2004) AND THIS REPORT

Gradstein et al. (2004) This reportW. Interior Ammonite Zone Age (Ma) Duration (m.y.) Age (Ma) Duration (m.y.)Baculites compressus 73.50 0.72 73.90 ?Didymoceras cheyennense 74.28 0.78 74.50 0.60Exiteloceras jenneyi 75.05 0.77 74.65 0.15Didymoceras stevensoni 75.74 0.69 74.98 0.33Didymoceras nebrascense 76.38 0.64 75.76 0.78Note: Ages are for base of ammonite zones.

FASSETT: PALEOCENE DINOSAURS PALAEO-ELECTRONICA.ORG

113 113

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Ala

mos

auru

s sa

njua

nens

is (f

rom

R.M

. Sul

livan

)A

lam

o M

esa

Eas

t65

76.

238

4-H

0201

03B

one

fragm

ent

4.6

NW

NW

7, 2

4N, 1

1W10

8.05

111

36.3

3376

Sm

all b

one

fragm

ent f

rom

lag

depo

sit

Ala

mo

Mes

a E

ast

190

11.6

5916

4-I

P-1

9147

Had

rosa

ur s

capu

la6.

1N

WN

W 7

, 24N

, 11W

108.

0494

636

.334

49S

ampl

e fro

m o

uter

cor

tical

sur

face

(fro

m S

.G. L

ucas

)A

lam

o M

esa

Eas

t68

112

.012

874-

J(1)

0227

99-B

1Li

mb

bone

8.2

SW

NW

17, 2

4N, 1

1W10

8.03

267

36.3

1647

Frag

men

t of l

arge

lim

b bo

neA

lam

o M

esa

Eas

t72

05.

014

174-

J(2)

0227

99-B

2Li

mb

bone

8.2

SW

NW

17, 2

4N, 1

1W10

8.03

267

36.3

1647

Frag

men

t of d

iffer

ent l

imb

bone

from

sam

e lo

calit

yA

lam

o M

esa

Eas

t82

210

.622

444-

K02

2799

-CLi

mb

bone

5.8

SW

NW

17, 2

4N, 1

1W10

8.03

267

36.3

1618

Frag

men

t of l

imb

bone

Ala

mo

Mes

a E

ast

436

7.7

6174

4-L

0227

99-A

Lim

b bo

ne5.

8S

EN

W 1

7, 2

4N, 1

1W10

8.02

990

36.3

1638

Frag

men

t of l

arge

lim

b bo

neA

lam

o M

esa

Eas

t23

21.

673

4-O

0515

04C

erat

ops

frill

3.7

SE

SE

17,

24N

, 11W

108.

0170

736

.307

54C

erat

opsi

an fr

ill fr

agm

ent

Ala

mo

Mes

a E

ast

312

4.9

1149

4-N

SM

P V

P-1

625

Sau

ropo

d fe

mur

4.9

SE

SE

17,

24N

, 11W

108.

0164

536

.307

53Fr

agm

ent o

f Ala

mos

auru

s sa

njua

nens

is (

from

R.M

. Sul

livan

)A

lam

o M

esa

Eas

t38

64.

014

4511

-B07

2598

-4C

Tyra

nosa

urid

fem

ur1.

8S

WS

W 4

, 22N

, 9W

107.

8018

536

.162

44Fr

agm

ent o

f fem

ur o

f Tyr

anno

saur

idae

, ind

term

inat

e (a

lso

SM

P V

P-1

113)

Kim

beto

166

1.6

5811

-C07

2598

-1C

Lim

b bo

ne2.

4S

WS

W 4

, 22N

, 9W

107.

8003

236

.163

40Fr

agm

ent f

rom

frag

men

ted

limb

bone

Kim

beto

247

4.7

541

11-D

P-3

5957

Sau

ropo

d fe

mur

4.6

SE

SW

4, 2

2N, 9

W10

7.79

382

36.1

6375

Larg

e fe

mur

of A

lam

osau

rus

sanj

uane

nsis

- (fr

om S

.G. L

ucas

)K

imbe

to89

5.2

247

Mea

n42

26.

616

24St

d. D

ev.

269

3.8

1920

Med

ian

386

5.2

1149

MIN

331.

638

MA

X83

414

6174

KIR

TLA

ND

FO

RM

ATI

ON

- C

RET

AC

EOU

SFi

gure

`M

eter

s B

elow

Loca

tion

desi

gnat

ion

Sam

ple

No

Sam

ple

of:

Bas

eof

OA

1/41

/4Se

cTs

pR

Long

itude

Latit

ude

Not

esQ

uadr

angl

eU

(ppm

)La

/Yb(

n)Su

mR

EEde

sign

atio

nSa

mpl

e N

o.Sa

mpl

e of

:B

ase

of O

A1/

41/4

Sec

., Ts

p, R

.Lo

ngitu

deLa

titud

eN

otes

Qua

dran

gle

U (p

pm)

La/Y

b(n)

Sum

REE

1-FS

S04

0403

Bon

e fra

gmen

t21

3.4

NE

NE

24,

30N

, 15W

108.

3633

836

.803

34S

ingl

e bo

ne fr

agm

ent (

colle

cted

by

L. K

alte

nbac

k an

d C

. Grif

fith)

Y

oung

s La

ke9

13.9

2882

4-A

(1)

0704

98-8

Cer

atop

s fri

ll9.

1S

WN

E 3

1, 2

5N. 1

2W10

8.14

788

36.3

5922

Bon

e fra

gmen

t fro

m la

g de

posi

tA

lam

o M

esa

Wes

t22

17.1

5231

4-A

(2)

0704

98-8

AV

erte

bra

9.1

SW

NE

31,

25N

. 12W

108.

1478

836

.359

22B

one

from

lag

depo

sit

Ala

mo

Mes

a W

est

1414

.239

344-

A(3

)07

0498

-8B

Lim

b bo

ne9.

1S

WN

E 3

1, 2

5N. 1

2W10

8.14

788

36.3

5922

Bon

e fra

gmen

t fro

m la

g de

posi

tA

lam

o M

esa

Wes

t2

20.9

955

4-A

(4)

0704

98-8

CTu

rtle

limb

bone

9.1

SW

NE

31,

25N

. 12W

108.

1478

836

.359

22B

one

from

lag

depo

sit

Ala

mo

Mes

a W

est

4527

.228

654-

A(5

)09

0498

-8X

Lim

b bo

ne9.

1S

WN

E 3

1, 2

5N. 1

2W10

8.14

788

36.3

5922

Bon

e fra

gmen

t fro

m la

g de

posi

tA

lam

o M

esa

Wes

t45

14.6

2070

4-A

(6)

0904

98-8

YLi

mb

bone

9.1

SW

NE

31,

25N

. 12W

108.

1478

836

.359

22B

one

fragm

ent f

rom

lag

depo

sit

Ala

mo

Mes

a W

est

2518

.256

264-

E02

2899

-ALi

mb

bone

54.9

SW

NE

31,

25N

. 12W

108.

1359

136

.347

27Fr

agm

ent o

f thi

n bo

ne p

rotru

ding

from

ss

ribA

lam

o M

esa

Wes

t2

22.4

2091

4-D

0202

03-A

Larg

e fe

mur

10.7

NW

NW

33,

25N

, 12W

108.

1251

136

.364

64Fr

agm

ent o

f lar

ge fe

mur

Ala

mo

Mes

a W

est

1411

.220

734-

OS

MP

VP

-146

8La

rge

fem

ur6.

1S

ES

E 1

7, 2

4N, 1

1W10

8.07

360

36.3

4083

Sm

all b

lack

to re

ddis

h fra

gmen

t (fro

m R

.M. S

ulliv

an)

Ala

mo

Mes

a E

ast

275.

626

14-

M02

2799

-DLi

mb

bone

6.1

SE

NW

17,

24N

,11W

108.

0260

236

.314

28B

one

fragm

ent

Ala

mo

Mes

a E

ast

276.

237

811

-A07

2598

-6C

Turtl

e-bo

ne18

.3N

EN

E 8

,22N

,9W

107.

8054

336

.160

04S

mal

l tur

tle-b

one

fragm

ent

Kim

beto

383.

956

1059

-A11

0803

-AH

adro

saur

met

atar

sal

39.6

SW

SW

8, 2

0N, 6

W10

7.50

146

35.9

7507

Had

rosa

urid

, ind

eter

min

ate

Sta

r Lak

e2

9.7

3010

59-B

0401

04Li

mb

bone

12.2

CN

E16

, 20N

, 6W

107.

4731

735

.967

81B

one

fragm

ent f

rom

lim

b bo

neS

tar L

ake

413

.166

59-C

1108

03-B

Frag

men

ted

fem

ur0.

1N

EN

E16

, 20N

, 6W

107.

4712

235

.970

08Fr

agm

ent o

f sp

ecim

en U

NM

TOA

-2 (o

rigin

ally

labe

led

from

Ojo

Ala

mo)

Sta

r Lak

e30

7.7

2705

Mea

n20

13.7

2650

Std.

Dev

.15

6.9

1912

Med

ian

2313

.723

98M

IN2

3.9

66M

AX

4527

.256

26

Rat

ios

of M

eans

Ojo

Ala

mo/

Kirt

land

210.

50.

6Sa

mpl

es fr

om c

olle

ctio

n si

te 0

2020

3 ar

e no

t inc

lude

d in

dat

a se

t bec

ause

they

wer

e fr

om v

erte

brat

e fr

agm

ents

that

may

not

be

in p

lace

4-C

(1)

0202

03-B

Bon

e fra

gmen

t10

.6N

WN

E32

, 25N

, 12W

108.

1300

536

.362

71B

one

erod

ed fr

om o

verly

ing

Ojo

Ala

mo

Ala

mo

Mes

a W

est

110

5.4

6428

4-C

(2)

0202

03-T

Turtl

e sh

ell

10.6

NW

NE

32, 2

5N, 1

2W10

8.13

005

36.3

6271

Turtl

e-sh

ell f

ragm

ent e

rode

d fro

m o

verly

ing

Ojo

Ala

mo

San

dsto

neA

lam

o M

esa

Wes

t86

6.0

7410

NO

TES:

Che

mic

al a

naly

ses

by J

.R. B

udah

n, U

SGS,

Den

ver;

che

mis

try

data

for 1

8 sa

mpl

es in

blu

e w

ere

publ

ishe

d in

Fas

sett

et a

l. 20

02; 1

4 sa

mpl

es in

bro

wn

publ

ishe

d he

re fo

r firs

t tim

e. S

ampl

es w

ith n

umbe

rs th

atar

e da

tes

colle

cted

by

J.E.

Fas

sett

(exc

ept f

or s

ampl

e 04

0403

) on

date

s sh

own;

oth

er a

naly

zed

sam

ples

from

R.M

. Sul

livan

and

S.G

. Luc

as, a

s sh

own;

sam

ples

ord

ered

from

wes

t to

east

.


114 114

TABLE 3. CHEMICAL COMPOSITION OF NEW VERTEBRATE-BONE SAMPLES FROM OJO ALAMO SANDSTONE AND KIRTLAND FORMATION, SAN JUAN BASIN, NM Kirtland Formation Ojo Alamo Sandstone Provenance uncertain

Sample number 040403 020203-A VP-1468 110803-A 040104 110803-B VP-1494 020103 P-19147 VP-1625 051504 P-35957 020203-B 020203-TDistance in m from 213 10.7 6.1 39.6 12.2 0.1 3.5 4.6 6.1 4.9 3.7 4.6 10.6 10.6base of Ojo Alamo below below below below below below above above above above above above below below

Major and minor elements (wt%)Ca 29.1 37.0 23.0 30.3 24.3 30.3 34.9 32.0 29.4 36.2 37.9 22.5 32.8 25.9Fe 0.26 0.37 18.40 1.15 0.46 1.15 0.50 0.38 0.289 0.66 0.37 0.33 0.66 10.60Na 0.55 0.24 0.43 0.50 0.02 0.504 0.24 0.38 0.738 0.32 0.30 0.29 0.35 0.33

Trace elements (ppm)Sc 2.5 1.9 0.4 8.6 0.8 8.6 0.6 3.2 3.2 5.3 0.7 1.2 4.3 19.7Co 0.9 0.9 5.2 4.2 7.2 4.2 6.3 38.2 3.9 27.4 15.3 137.0 2.9 6.2Zn 142.0 114.0 78.6 185.0 4.8 185.0 43.0 235.0 60.1 109.0 61.3 158.0 278.0 398.0As 0.7 2.3 14.7 5.2 21.5 5.2 13.2 11.3 2.7 13.5 10.6 3.6 6.1 31.0Sb 0.4 0.3 14.8 1.7 0.2 1.7 1.1 1.7 0.4 1.3 1.2 0.6 1.0 6.4U 9.0 13.9 26.6 2.0 3.9 29.6 657.0 190.0 681.0 386.0 312.0 89.0 110.0 85.5Th 0.38 0.35 0.10 3.8 0.04 3.8 0.20 0.94 1.5 0.43 0.21 0.16 0.66 0.88Hf 0.15 0.04 0.16 2.2 0.01 2.2 0.14 1.04 1.5 0.22 1.05 0.24 0.37 0.84Ta 0.02 0.03 0.05 0.27 0.02 0.27 0.01 0.06 0.12 0.02 0.02 0.03 0.05 0.07La 1228 1672 302 2122 35.7 660 86.5 3633 341 749 916 229 3441 3666Ce 1060 867 91.3 1080 29.4 1080 3.4 2410 549 525 409 88.6 2370 2710Nd 839 409 33.3 513 17.6 513 1.7 1380 224 361 203 40.6 1670 1870Sm 200 86.6 7.0 120 3.5 120 0 308 43.1 85.3 53.5 9.9 420 556Eu 46.5 18.8 1.8 30.9 0.72 30.9 0.14 75.6 12.6 20.7 16.1 2.2 79.5 95.1Gd 269 98.1 13.0 172 2.5 172 0.60 402 72 123 97.4 15.9 493 670Tb 39.1 15.1 2.2 24.7 0.37 24.7 0.13 60.5 9.1 18.9 15.4 2.5 74.7 103.0Ho 21.5 17.1 3.8 29.1 0.36 29.1 0.48 63.6 11.0 26.1 18.1 3.5 73.8 95.4Tm 4.1 5.3 1.7 10.3 0.11 10.3 0.44 12.5 3.4 7.1 7.4 1.6 21.3 21.9Yb 18.6 31.4 11.3 57.8 0.57 57.8 2.9 66.0 19.2 39.3 39.3 9.3 135 129Lu 2.2 4.6 1.7 7.0 0.07 7.0 0.55 7.8 2.8 5.2 5.1 1.4 20.5 19.8Sum REE 2882 2073 261 3010 66.0 2705 38.0 5916 1287 1445 1149 247 6428 7410La/Yb(N) 13.9 11.2 5.6 9.7 13.1 7.7 6.2 11.6 12.0 4.0 4.9 5.2 5.4 6.0Mean U 14.2 Mean U 386 Mean U 97.75Mean Sum Ree 1833 Mean Sum Ree 1680 Mean Sum Ree 6919Mean La/Yb(n) 10.2 Mean La/Yb(n) 7.3 Mean La/Yb(n) 5.7Notes: Chemical analyses by J. R. Budahn, USGS, Denver, CO; additional elements (K, Rb, Ca, Cr, Zr, W, Se, Ni, Au, Br, Mo) not tabulated because reported analytical precision resulting from interelement interferences, fission yield corrections, and/or counting statistics typically exceeds 15% (relative standard deviation). (n)--chondrite-normalized abundance


115 115

Chemical Standard Standardparameter deviation deviationU 33 834 436 447 298 2 45 25 24 16Lan/Ybn 2 14 5 6 4 4 27 17 16 8Sum REE 38 6174 1004 1587 1883 66 5626 2865 3196 2000 Note: n = chondrite-normalized abundance.

Maximum Median Mean

TABLE 4. SUMMARY STATISTICS FOR CHEMICAL PARAMETERS DISTINGUISHING KIRTLAND FORMATION BONES FROM OJO ALAMO SANDSTONE BONES

Ojo Alamo Sandstone (15 samples) Kirtland Formation (15 samplesMinimum Maximum Median Mean Minimum


116 116

TA

BLE

5. P

ALY

NO

MO

RPH

S ID

ENTI

FIED

BY

AN

DER

SON

(196

0, T

AB

LE 2

) FR

OM

KIR

TLA

ND

FO

RM

ATI

ON

, OJO

ALA

MO

SA

ND

STO

NE,

AN

D N

AC

IMIE

NTO

FO

RM

ATI

ON

, SO

UTH

EAST

SA

N J

UA

N B

ASI

N (F

IGU

RES

. 1 A

ND

21

Kirt

land

Sha

le fl

orul

eO

jo A

lam

o 2

floru

leO

jo A

lam

o 1

floru

leN

acim

ient

o 1

floru

leN

acim

ient

o 2

floru

leA

cer s

triat

a (P

flug,

195

9)A

lnus

? sp

.A

reci

pite

s m

icro

retic

ulat

us n

. sp.

Are

cipi

tes

retic

ulat

us (

Van

der

Ham

men

, 195

4)A

reci

pite

s re

ticul

atus

(V

an d

er H

amm

en, 1

954)

Are

cipi

tes

retic

ulat

us (

Van

der

Ham

men

, 195

4)B

omba

caci

pite

s na

cim

ient

oens

is n

. gen

. and

sp.

Bre

vico

lpor

ites

colp

ella

n. g

en. a

nd s

p.C

onfe

rtisu

lcite

s kn

owlto

ni n

. gen

. and

sp.

Con

ferti

sulc

ites

know

ltoni

n. g

en. a

nd s

p.C

onfe

rtisu

lcite

s sp

.C

upan

ieid

ites

aff.

C. r

etic

ular

is C

ooks

on a

nd P

ike,

195

4C

upan

ieid

ites

aff.

C. m

ajor

Coo

kson

and

Pik

e, 1

954

Cup

anie

idite

s af

f. C

. maj

or C

ooks

on a

nd P

ike,

195

4E

xtra

tripo

ropo

lleni

tes

sp.

Fove

otril

etes

scr

obic

ular

is (

Ros

s) R

. Pot

onie

, 195

6G

leic

heni

idite

s se

noni

cus

Ros

s, 1

949

Inte

rtrile

tes

retic

ulat

us n

. gen

. and

sp.

Kur

tzip

ites

trisp

issa

tus

n. g

en. a

nd s

p.Li

liaci

dite

s hy

alac

inia

tus

n. s

p.Li

liaci

dite

s hy

alac

inia

tus

n. s

p.Li

liaci

dite

s le

ei n

. sp.

Lilia

cidi

tes

leei

n. s

p.Li

liaci

dite

s le

ei n

. sp.

Lilia

cidi

tes

leei

n. s

p.Li

liaci

dite

s sp

.Ly

copo

dium

nov

omex

ican

um n

. sp.

Lyco

podi

um n

ovom

exic

anum

n. s

p.Ly

godi

ospo

rites

?sp

.M

onos

ulci

tes

pers

pino

sus

Cou

per,

1953

Mon

osul

cite

s sp

.N

avis

ulci

tes

mar

gina

tus

n. g

en. a

nd s

p.N

yssa

pue

rcoe

nsis

n. s

p.M

omip

ites

inae

qual

is n

. sp.

Mom

ipite

s in

aequ

alis

n. s

p.M

omip

ites

tenu

ipol

us n

. sp.

Mom

ipite

s te

nuip

olus

n. s

p.P

aliu

rus

tripl

icat

us n

. sp.

Pal

iuru

s tri

plic

atus

n. s

p.P

erip

orop

olle

nite

s sp

.P

erot

rilet

es c

uben

sis

n. s

p."P

inus

hap

loxy

lon

type

" Rud

olph

193

5"P

inus

hap

loxy

lon

type

" Rud

olph

193

5"P

inus

syl

vest

ris t

ype"

Rud

olph

193

5P

odoc

arpu

s no

rthro

pi n

. sp.

P

odoc

arpu

s se

llow

iform

is Z

aklin

skaj

a, 1

957

Pod

ocar

pus

sello

wifo

rmis

Zak

linsk

aja,

195

7P

odoc

arpu

s se

llow

iform

is Z

aklin

skaj

a, 1

957

Pod

ocar

pus

zuni

ensi

s n.

sp.

Pol

leni

tes?

sp.

Pol

ypod

iidite

s sp

p.P

olyp

odiid

ites

spp.

Pol

ypod

iidite

s sp

p.P

rote

acid

ites

retu

sus

n. s

p.P

rote

acid

ites

thal

man

nii

n. s

p.P

rote

acid

ites

sp.

Que

rcus

exp

lana

ta n

. sp.

Que

rcus

? sp

.R

ecto

sulc

ites

latu

s n.

gen

. and

sp.

Rug

ulat

ispo

rites

sp.

Sal

ix s

p.S

alix

sp.

Silt

aria

cf.

S. s

cabr

iext

ima

Trav

erse

, 195

5S

phag

num

sp.

Spo

rites

neg

lect

us n

. sp.

Spo

rites

? sp

. ATe

tradi

tes

sp.

Tilia

dan

ei n

. sp.

Tilia

wod

ehou

sei

n. s

p.Tr

icho

tom

osul

cite

s co

ntra

ctus

n. s

p.Tr

icol

pite

s an

gulo

lum

inos

usn.

sp.

Tric

olpi

tes

angu

lolu

min

osus

n. s

p.Tr

icol

pite

s sp

. ATr

icol

pite

s sp

. BTr

icol

porit

es rh

ombo

ides

n. s

p.Tr

icol

porit

es rh

ombo

ides

n. s

p.Tr

icol

porit

es tr

aver

sei

n. s

p.Tr

ilete

s? s

p. A

Trip

orop

olle

nite

s pl

ekto

sus

n. s

p.Tr

ipor

opol

leni

tes

plek

tosu

s n.

sp.

Ulm

oide

ipite

s kr

empi

n. g

en. a

nd s

p.U

lmoi

deip

ites

krem

pi n

. gen

. and

sp.

Ulm

oide

ipite

s pl

aner

aefo

rmis

n. g

en. a

nd s

p.U

lmoi

deip

ites

trico

stat

us n

. gen

. and

sp.

Ulm

oide

ipite

s tri

cost

atus

n. g

en. a

nd s

p.U

lmoi

deip

ites

trico

stat

us n

. gen

. and

sp.

Ulm

oide

ipite

s tri

cost

atus

n. g

en. a

nd s

p.N

ote:

Ojo

Ala

mo

2 flo

rule

in lo

wer

par

t of O

jo A

lam

o S

ands

tone

; Ojo

Ala

mo

1 flo

rule

from

mid

dle

of O

jo A

lam

o S

ands

tone

(Fig

ure

47);

Nac

imie

nto

1 flo

rule

is 3

0 cm

abo

ve b

ase

of N

acim

ient

o Fo

rmat

ion;

Nac

imie

nto

2 flo

rule

from

coa

l bed

35

m a

bove

bas

e of

Nac

imie

nto

Form

atio

n; P

rote

acid

ites

was

rena

med

Tsc

hudy

polli

s (N

icho

ls 2

002)

; Lyc

opod

ium

nov

omex

ican

um (

Nac

imie

nto

2 flo

rule

)is

now

Zliv

ispo

ris n

ovom

exic

anum

(N

icho

ls 2

005,

writ

ten

com

mun

.).


117 117

T

AB

LE 6

. PU

BLI

SHED

PA

LYN

OM

OR

PH L

ISTS

FR

OM

OJO

ALA

MO

SA

ND

STO

NE

TYPE

AR

EALo

calit

y S

GL

00-0

46Lo

calit

y P

4300

& B

AA-3

Loca

lity

D69

01Lo

calit

y D

6880

Loca

lity

D63

91 &

BAA

-1Lo

calit

y B

AA-2

Upp

er K

irtla

nd F

m.

Upp

er K

irtla

nd F

m.

Upp

erm

ost K

irtla

nd F

m.

Upp

er O

jo A

lam

o S

s.U

pper

mos

t Ojo

Ala

mo

Ss.

Low

erm

ost N

acim

ient

o Fm

.Al

gal c

ysts

Ara

ucar

iaci

tes

aust

ralis

Are

cipi

tes

retic

ulat

usA

reci

pite

s re

ticul

atus

Are

cipi

tes

retic

ulat

usA

reci

pite

s re

ticul

atus

Are

cipi

tes

cf.

A. m

icro

reti c

ulat

usA

reci

pite

s c

f. A

. ret

icu l

atus

Are

cipi

tes

spA

zolla

cre

tace

aA

zolla

cf.

A s

chop

fiB

revi

colp

orite

s c

olpe

lla

Cer

cidi

phyl

lites

sp.

Che

nopo

dipo

llis

sp.

Cor

ollin

a to

rosa

C

orol

lina

toro

sa

Cup

anie

idite

s sp

.C

upan

ieid

ites

sp.

Cup

anei

dite

s a

ff. C

. maj

orC

upan

eidi

tes

cf.

C. m

ajor

Cup

ulife

roid

aepo

lleni

tes

min

utus

Cup

ulife

roid

aepo

lleni

tes

min

utus

Cya

thid

ites

sp.

Cya

thid

ites

min

orC

ycad

opite

s fra

gilli

sD

yado

napi

tes

retic

ulat

usD

yado

napi

tes

retic

ulat

usD

yado

napi

tes

retic

ulat

usFr

axin

oipo

lleni

tes

varia

bilis

Gho

shis

pora

sp.

Laev

igat

ospo

rites

sp.

Laev

igat

ospo

rites

spp

.Li

liaci

dite

s hy

alac

inia

tus?

Lilia

cidi

tes

leei

Lilia

cidi

tes

leei

Lilia

cidi

tes

sp.

of A

nder

son

Mom

ipite

s in

aequ

alis

Mom

ipite

s in

aequ

alis

Mom

ipite

s in

aequ

alis

Mom

ipite

s sp

.M

omip

ites

sp.

Mom

ipite

s te

nuip

olus

Mom

ipite

s te

nuip

olus

Mom

ipite

s te

nuip

olus

Mom

ipite

sO

smun

daci

dite

s w

ellm

anni

iO

void

ites

sp

“Pal

aeoi

soet

es”

sp.

“Pal

aeoi

soet

es”

sp.

"Pal

iuru

s” t

riplic

atus

Pal

iuru

s tri

plic

atus

?P

anda

niid

ites

radi

cus

Pan

dani

idite

s ty

picu

sP

anda

niid

ites

typi

cus

Pan

dani

idite

s ty

picu

sP

anda

niid

ites

typi

cus

Pin

us s

p.P

ityos

porit

es c

onst

rictu

sP

ityos

porit

es s

pp.

Pity

ospo

rites

sp.

Pity

ospo

rites

sp.

Pod

ocar

pus

sp.

Pod

ocar

pus

sp.

Pol

ypod

iispo

roni

tes

sp.

Psi

last

epha

noco

lpite

s sp

.“Q

uerc

us” e

xpla

nata

Que

rcus

exp

lana

taQ

uerc

us s

p.P

rote

acid

ites

retu

sus

Pro

teac

idite

s re

tusu

sP

rote

acid

ites

retu

sus

Pro

teac

idite

s th

alm

anni

iP

rote

acid

ites

thal

man

nii

Pro

teac

idite

s th

alm

anni

iR

ecto

sulc

ites

latu

sR

ecto

sulc

ites

latu

sR

hoip

ites

sp.

Sch

izos

poris

par

vus

Syn

colp

orite

s m

inim

us

Taxo

diac

eaep

olle

nite

s hi

atus

Taxo

diac

eaep

olle

nite

s hi

atus

Tetra

colp

ites

2 s

p.Te

trapo

rina

sp.

Tric

olpi

tes

angu

lolu

min

osus

Tric

olpi

tes

fove

olat

eTr

icol

pite

s in

tera

ngul

usTr

icol

porit

es rh

ombo

ides

Tric

olpi

tes

scab

rate

Tric

olpi

tes

mic

rore

ticul

atus

Tric

olpi

tes

retic

ulat

usTr

icol

pite

s? s

p. c

f. G

unne

raTr

icol

pite

s sp

p.U

lmip

olle

nite

s kr

empi

iU

lmip

olle

nite

s U

lmip

olle

nite

s kr

empi

iU

lmip

olle

nite

s kr

empi

iU

lmip

olle

nite

s 3

and

4 p

ored

.("

Ulm

oide

ipite

s") t

ricos

tatu

sU

lmoi

deip

ites

trico

stat

usU

lmoi

deip

ites

trico

stat

usU

lmoi

deip

ites

trico

stat

usN

otes

: Pal

ynom

orph

s id

entif

ied

by th

e fo

llow

ing:

SG

L 00

-046

by

D. R

. Bra

man

in S

ulliv

an e

t al.

(200

5, p

. 401

); P

4300

, D69

01, a

nd D

6880

by

D. J

. Nic

hols

in F

asse

tt et

al.

(200

2, ta

ble

2); B

y R

. H.

Tsch

udy

in F

asse

tt et

al.

(198

7, p

. 27)

; BAA

-1, -

2, -3

by

R. Y

. And

erso

n in

Bal

tz e

t al.

(196

6, p

. D17

), co

mpl

ete

lists

of p

alyn

omor

phs

not a

vaila

ble

for t

he B

AA lo

calit

ies

and

the

few

spe

cies

iden

tifie

d at

BAA

-1 a

nd -3

loca

litie

s ar

e co

mbi

ned

with

list

s fo

r D63

91 a

nd P

4300

, res

pect

ivel

y; s

ampl

es P

4300

and

SG

L 00

-046

from

sam

e ca

rbon

aceo

us s

hale

bed

at s

ame

loca

lity;

sam

ple

loca

litie

s sh

own

on F

igur

es 4

and

51.


118 118

TABLE 7. LIST OF PALYNOMORPHS IDENTIFIED BY R. H. TSCHUDY IN FASSETT AND HINDS (1971, TABLE 1) AT MESAPORTALES AND TWO OTHER LOCALITIES IN SAN JUAN BASIN

U. S. Geological Survey paleobotany locality numbersPaleocene Cretaceous

Age Palynomorphs D3738-A D3738-B D3803 D3738-C D4017-A D4017-B D4017-C D4119P Momipites sp. (Momipites inaequalis And.) X XP Monosulcites sp. (Rectosulcites latus And.) X XP Triatriopollenites sp. A XP Triatriopollenites sp. B XP, K? Cupaneidites sp. (Cupaneidites aff. C. major And.) X X X

Laevigatosporites sp (Polypodiidites sp. And.) XP Tricolporites sp. (Tricolporites anguloluminosus And.) X XP, K Tricolpopollenites sp. (Quercus explanata And.) X X X X

Abietineaepollenites sp. (Podocarpus sellowiformis And.) X X XClassopollis sp. XAbietineaepollenites sp. (Podocarpus northrupi And.) X

P, K Zlivisporis sp. X XP, K Ulmipollenites sp. (Ulmoideipites tricostatus And.) X X X XP, K Liliacidites sp. X XP Pollyporopollenites sp. XP Tricolporites sp. (Tricolporites rhomboides And.) XP Tricolporites sp. X

Tricolporites sp. (?Eleagnaceae ) XOsmundacidites sp. X

P Tricolporites sp. XK Proteacidites (Proteacidites thalmannii And.) X X X XK Proteacidites (Proteacidites retusus And.) XK Monoporopollenites sp. XK Araucariacites sp. X X X

Erdtmannipollis sp. XK Granabivesiculites sp. XP, K Liliacidites sp. (Liliacidites leei And.) X X XP, K Liliacidites sp. (Liliacidites hyalaciniatus And.) X

Liquidambarpollenites sp. XK Tricolpites interangulus Newman X

Tricolpopollenites sp. X X XEucommiidites sp. X X XFoveosporites sp. cf. F. canalis Balme XInaperturopollenites cf. I. hiatus (R. Pot) Th. & Pf. X

K Ephedra sp. cf. E. voluta Stanley X XK Zonalapollenites sp. XK Neoraistrickia sp. XK Tricolpopollenites sp. A XK Monosulcites sp. XK Tricolporites sp. XK Tricolpopollenites sp. B XK Tiliaepollenites sp. (Tilia wodehousei And.) XP, K Tricolpopollenites sp. C XNote: Palynomorphs listed by age; generally youngest to oldest going down and left to right; Proteacidites was renamed Tschudypollis byNichols (2002); D3738-A, -B from Ojo Alamo Sandstone, D3803 from Nacimiento Formation, all other samples from Kirtland and (or)Fruitland Formation; sample locality for sample D4119 shown on Figure 1, all other sample localities shown on figure 21. In left columnP = Paleocene, K = Cretaceous


119 119

TABLE 8. LIST OF PALYNOMORPHS IDENTIFIED BY R. H. TSCHUDY (1973) FROM SAMPLES OF GASBUGGY CORE; MODIFIED FROM TSCHUDY (1973) APPENDIX TABLE

Nacimiento Ojo Alamo Formation Sandstone Fruitland Formation

Palynomorphs 3436

.6

3453

.5-3

455.

8

3515

.6

3574

.4

3584

3619

.6

3638

.1

3655

.8

3714

.7

3716

.5

3725

.8

3752

.5

3757

.5

3775

3790

.3

3805

3807

.5

3811

.9

3824

.6

3844

3851

-385

3

3869

-6-3

870

3879

.5-3

881.

4

3906

-390

7.8

3912

-391

3

Nyssa puercoensis X X 1 1Biretisporites sp. 1 2 1 X 1 X 1 1 1 XUnclassified triletes 2 2 x 13 11 3 12 5 19 10 5 5 9 1 1 10 7 XLaevigatosporites sp. 7 X 1 1 X 10 10 19 7 9 14 13 13 11 7 28 25 10 3 3 3 3Unclassified bisaccates 32 10 1 3 1 1 1 1 2 X 8 X X 2 1Classopollis sp. 28 1 X 60 3 21 1 5 X X 23 2Taxodiaceaepollenites sp. 1 2 4 1 X X 1 1 3 1Equisetosporites spp. 5 1 3 1 X X 1 2 3cf Ephedra voluta 4 5 1Liliacidites complexus 1 1 2 2 1 1 2 8 3 1 1 6 7 24Salixipollenites sp. 1Pandaniidites radicus 1 1 XEngelhardtia type 1 X 3 46 X X 1 XMomipites sanjuanensis 4 2 1 2 7 4 8 2 7 1 3 8 X 2 1 2 3 20 XPeriporopollenites sp. 2 2 X 4Ulmipollenites spp. 9 2 7 1Hystrichosphaerids & dinoflagellates X XCyathidites spp. X 1 X X X 3 1 4 9 3 8 2 2 1 1 1 2 1Stereisporites spp. X 1 X X 1 X X 1 4Cyrilla minima 98 X 1 2 1 1 1 4Maceopolipollenites tenuipolus 1Echinatisporis sp. 1 1 1 X X 1 1 6 18Arecipites spp. 3 4 22 4 2 4 1 2 3 5 1 3 2 1 18 1 2Aquilapollenites spp. 1 1cf. Triporopollenites rugatus 1 1 X X 3 X 1 2 X 56 1Deltoidospora spp. X XTricolpites anguloluminosus X XTricolpites vulgaris X 1cf. Cupanieidites XVitis? affluens X 35 X 1 X X X 2Quercus explanata 2 1 X X 1Unclassified triporates 1 3 1 X 2 3 3 1 4 1 2 6 1 4 7 6 4 2Tricolpites sp. 1 X X X X X 2 1Cupanieidites major XQuadrapollenites sp. X 1Tricolporites rhomboides X X 4Ericaceoipollenites sp. PALEOCENE 1 3 1 1 X X 1 X XProteacidites spp. CAMPANIAN 2 X 14 14 25 28 12 12 19 17 9 24 15 2 6 17 11 X 4Foraminisporis sp. X 1 3 X X X X Xcf. Concavisporites verrucosus X 1 2Ghoshispora spp. 2 1 2 X 1 2 2 2 5Cicatricosisporites spp. 1 X X X 4 2 X 2Liliacidites spp. 2 1 2 1 2Tricolpites reticulatus 18 1 X X 9 8 7 X X 1 X 1Accuratipollis spp. 2 1 X 8 1 6 6 3 X 1 1Ilexpollenites sp. 2 4 23 29 3 5 4 3 11 4 1 8cf Tilia wodehousei 1 1 X 1cf. Taurocusporites 1 X 2 XLycopodiacidites spp. 1 X X 2Camarozonosporites spp. X 1Lycopodiumsporites spp. 2 X XMicrofoveolatosporis canaliculatus 1 1 2 2 1 2 X 4 1 1 X XAraucariacites 1Zonalapollenites 1 1 5 Xcf. Radialetes costatus 1Aquilapollenites quadrilobus 1 X X XTriplanosporites sp. 1cf. Zlivisporis 1 X 1 1Tricolpites sp. 3cf. Minorpollis X 1Aequitriradites spinulosus 1 1Aquila 36 C 1 1Alsophilidites sp. 1Gleicheniidites spp. 1 X X 2 XPolypodiidites sp. 1 X 1Vitis ? affluens (C3-r 43) 1 X 1 1Aquilapollenites turbidus 1 X X 1Aquilapollenites attenuatus X X XLeptolepidites major 1 XAquilapollenites 18 XKuylisporites sp. 1 XKlukisporites spp. X 1 XPhaseoliidites stanleyi 2 X 3 1Aquilapollenites 4E X XToroisporis sp. 1 X XAquilapollenites 17 1Aquilapollenites delicatus 1Aquilapollenites senonicus XTrudopollis sp. X X XLycopodiacidites kuepperi XAppendicisporites spp. XKurtzipites trispissatus 1Trudopollis meekeri X 1 XPolypodiisporites amplus XPolypodiisporites sp. XEucommiidites sp. XTricolpites hians 2Aquilapollenites 42 XSubtriporopollenites sp. X 1Microreticulatisporites sp. X XAequitriradites sp. 2Notes: Base of Ojo Alamo Sandstone is at drilled depth of 3,680 ft; Maceopolipollenites tenuipolus is same species as Momipites tenuipolus


120 120

TAB

LE 9

. UN

PUB

LISH

ED P

ALYN

OM

OR

PH L

ISTS

FR

OM

USG

S PA

LEO

BO

TAN

Y LO

CAL

ITIE

S IN

MES

A PO

RTA

LES

AREA

- ST

RAT

IGR

APH

IC L

EVEL

S SH

OW

N O

N F

IGU

RES

22

AND

23

C

reta

ceou

s

Pal

eoce

neLo

calit

y D

6626

-ALo

calit

y D

6626

-BLo

calit

y D

6626

-CLo

calit

y D

6582

Loca

lity

D65

83-A

Loca

lity

D65

83-B

Loca

lity

D68

78Lo

wer

Kirt

.-Fru

it. F

m.

Low

er K

irt.-F

ruit.

Fm

.Lo

wer

Kirt

.-Fru

it. F

m.

Upp

er K

irt.-F

ruit.

Fm

.U

pper

mos

t Kirt

.-Fru

it. F

m.

Upp

erm

ost K

irt.-F

ruit.

Fm

.N

acim

ient

o Fm

.A

cant

hotri

lete

sA

cant

hotri

lete

sA

cant

hotri

lete

sA

ccur

atip

ollis

Aeq

uitri

radi

tes

Aeq

uitri

radi

tes

Alg

al c

ysts

Aln

ipol

leni

tes

4 po

red

Aln

ipol

leni

tes

Ara

ucar

iaci

tes

com

mon

Ara

ucar

iaci

tes

Ara

ucar

iaci

tes

Are

cipi

tes

Are

cipi

tes

Are

cipi

tes

sp.

Aqu

ilapo

lleni

tes

quad

rilob

usA

quila

polle

nite

s se

noni

cus

Aqu

ilapo

lleni

tes

trial

atus

, var

. uni

form

isB

alm

eisp

orite

sB

isac

acca

te c

onife

r pol

len

Bis

acac

cate

con

ifer p

olle

nB

isac

acca

te c

onife

r pol

len

Bom

baca

cipi

tes

naci

mie

ntoe

nsis

Cic

atric

osis

porit

esB

otry

ococ

cus

Bot

ryoc

occu

s

Cor

ollin

aC

orol

lina

Cor

ollin

aC

orol

lina

com

mon

Cup

ulife

roid

aepo

lleni

tes

min

utus

Din

ofla

gella

tes

very

few

Din

ofla

gella

tes

very

few

Din

ofla

gella

tes

very

few

Equ

iset

ospo

rites

par

alle

l stri

aeE

quis

etos

porit

es p

aral

lel s

triae

Equ

iset

ospo

rites

spi

ral

Fern

spo

res

not a

bund

ant

Frax

inoi

polle

nite

s va

riabi

lisG

leic

heni

idite

sH

ystri

chos

pher

es v

ery

few

Hys

trich

osph

eres

ver

y fe

wH

ystri

chos

pher

es v

ery

few

Ilexp

olle

nite

sK

luki

spor

ites

Leca

niel

laLe

cani

ella

Kur

tzip

ites

Lilia

cidi

tes

com

plex

usLi

liaci

dite

sLy

copo

diac

idite

sM

omip

ites

sanj

uane

nsis

Mom

ipite

s sp

.M

omip

ites

tenu

ipol

usM

omip

ites

tenu

ipol

usM

onol

ete

fern

spo

res

Nys

sapo

lleni

tes

sp.

Ped

iast

rum

Ped

iast

rum

Per

ipor

opol

leni

tes

Pity

ospo

rites

sp.

Plic

apol

lis?

Pod

ocar

pidi

tes

cf. P

. sel

low

iform

isP

odoc

arpi

dite

sP

ristin

uspo

lleni

tes

Pris

tinus

polle

nite

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121 121

TABLE 10. COMPARISON OF PALYNOMORPH LISTS FROM FOUR PALYNOLOGISTS FOR SAN JUAN RIVER SITE SAMPLES, SAN JUAN BASIN, NMLocality R3508 - Frederiksen Localities 6877-A, -B, -C - Nichols Locality SGL 00-047 - Braman Locality "Near Farmington" - Newman

Alisporites bilateralis Arecipites reticulatus Arecipites reticulatus Arecipites sp.Azolla cretacea

BalmeisporitesBrevicolporites colpellaChenopodipollis sp.Cicatricosisporites spp.

Circulina parva Classopollis classoides

Corollina torosa (incl. monads and tetrads)Cupanieidites sp.

Cupanieidites cf. C. reticularis

Cupuliferoidaepollenites minutusCyathidites minor Cyathidites minor

Cycadopites fragilis Equisetosporites lajwantis

Fraxinoipollenites variabilisGunneraInterpollisKurtzipites

Laevigatosporites sp.Laevigatosporites haardtii

Lycopodium novomexicanumMomipites inaequalis Momipites inaequalisMomipites tenuipolus Momipites tenuipolus Momipites tenuipolus

Nyssapollenites sp.Nyssapollenites explanatus Ovoidites ligneolus

“Palaeoisoetes” sp.“Paliurus” triplicatus “Paliurus” triplicatusPandaniidites Pandaniidites typicus Pandaniidites typicus

Pityosporites sp.Proteacidites Proteacidites thalmannii ProteaciditesRectosulcites latus

Schizosporis parvus Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus

Taxodiaceaepollenites vacuipites Tricolpites sp.Triporoletes novomexicanum

Triporoletes simplex Ulmipollenites krempii Ulmipollenites krempiiU. tricostatus U. tricostatus

Ulmoideipites krempi Ulmoideipites spp. 3 and 4 pored smooth to verrucate forms

Note: Samples analyzed by Frederiksen and Nichols (USGS) and by Braman (Royal Tyrell Museum of Paleontology) from same bed of coaly-carbonaceous shale 15 m above base of Ojo Alamo Sandstone; sample analyzed by Newman (Colorado School of Mines, retired) from a stratigraphically lower mudstone bed of uncertain stratigraphicprovenance; palynomoph identifications in written communs. from: Frederiksen (1985), Nichols (1994), and Braman (2000) and in Newman (1987, p. 159); palynomorph listheaded "Localities 6877-A, -B, -C" was labeled "25Ga, b, c, composite list" in Fassett and others (2002, table 2); Lycopodium novomexicanum (Nacimiento 2 florule) is nowZlivisporis novomexicanum (Nichols 2005, written commun.).


122 122

TABLE 11. LIST OF PALYNOMORPHS IDENTIFIED FROM USGS DRILL HOLE SL 10-1, POT MESA LOCALITY (FIGURE 59) SOUTHERN SAN JUAN BASIN, NEW MEXICO

Depths in meters (feet) 28.6 m (93.8 ft) 28.8 m (94.5 ft) 29.4 m (96.6 ft) 65.5 m (215 ft) 66.6 m (218.5 ft)U. S. Geological Survey locality number D5783-A D5783-B D5783-C D5783-D D5783-E

Equisetosporites 5 X XCorollina X XAbietineaepollenites X X XPeriporopollenites X X XForaminisporis X XLycopodiumsporites X XZlivisporis X XAequitriradites X XBalmeisporites X XLycopodiacidites X X X XAzolla XLiliacidites XPterospermopsis XProteacidites X X X X Xcf Vitis affluens XUlmipollenites X X XMonosulcites XOsmundacidites XTaxodiaceaepollenites X X XKurtzipites trispissatus XQuercus explanata XNyssapollenites albertensis XMomipites sanjuanensis X XMicrofoveolatosporis XDinoflagellate XAlnipollenites XTricolpites vulgaris XRugubivesiculites XEchinatisporis XAquilapollenites XTricolporites rhomboides XGleicheniidites XPseudoplicapollis XCicatricosisporites XCamarozonosporites XKlukisporites XNote: Palynomorphs listed by age; generally youngest to oldest going down; identifications by R. H Tschudy (1977, written commun.); Proteacidites renamed Tschudypollis by Nichols (2002)


123 123

TABLE 12. COMPARISON OF PALYNOMORPH LISTS IDENTIFIED FROM POT MESA AREA SAMPLES (FIGURE 60) ALL SAMPLES FROM CRETACEOUS KIRTLAND FORMATION

Localities D5783-A, -B, -C, -D, -E Locality D6879 Newman locality Identification by R. H. Tschudy (1977) Identification by D. J. Nichols (1994) Identification by K. Newman (1987)

AbietineaepollenitesAequitriraditesAlnipollenitesAquilapollenitesAzolla Azolla cretaceaBalmeisporites BalmeisporitesCamarozonosporites

Chenopodipollis sp.CicatricosisporitesCorollina Corollina torosa

Cupanieidites sp.Cupuliferoidaepollenites minorCyathidites minor

DinoflagellateEchinatisporis

Ephedra multicostataEquisetosporites 5

Erdtmanipollis cretaceaForaminisporis

Fraxinoipollenites variabilisGleicheniidites

Gunnera microreticulata GunneraInterpollis

KlukisporitesKurtzipites trispissatus Kurtzipites trispissatus Kurtzipites

Laevigatosporites sp.Liliacidites Liliacidites complexus

Liliacidites leeiLycopodiaciditesLycopodiumsporitesMicrofoveolatosporisMomipites sanjuanensisMonosulcitesNyssapollenites albertensis

Nyssapollenites sp.Osmundacidites

“Palaeoisoetes” sp.Pandaniidites typicus

PeriporopollenitesProteacidites Proteacidites retusus Proteacidites

Proteacidites thalmanniiPseudoplicapollis

PseudoschizaeaPterospermopsisQuercus explanataRugubivesiculitesTaxodiaceaepollenites

"Tilia" wodehouseiTricolpites vulgarisTricolporites rhomboides

Triporoletes novomexicanumUlmipollenites

Ulmipollenites tricostatusUlmoideipites spp.3 and 4 pored smooth to verrucate forms

cf Vitis affluensZlivisporisNote: Proteacidites renamed Tschudypollis by Nichols (2002); list of palynomorphs identified by Tschudy is composite from five drill-hole samples from drill hole USGS SL 10-1 (Figure 59); palynomorph lists for each sample on Table 11


124 124

TABLE 11. LIST OF PALYNOMORPHS IDENTIFIED FROM USGS DRILL HOLE SL 10-1, POT MESA LOCALITY (FIGURE 59) SOUTHERN SAN JUAN BASIN, NEW MEXICO

Depths in meters (feet) 28.6 m (93.8 ft) 28.8 m (94.5 ft) 29.4 m (96.6 ft) 65.5 m (215 ft) 66.6 m (218.5 ft)U. S. Geological Survey locality number D5783-A D5783-B D5783-C D5783-D D5783-E

Equisetosporites 5 X XCorollina X XAbietineaepollenites X X XPeriporopollenites X X XForaminisporis X XLycopodiumsporites X XZlivisporis X XAequitriradites X XBalmeisporites X XLycopodiacidites X X X XAzolla XLiliacidites XPterospermopsis XProteacidites X X X X Xcf Vitis affluens XUlmipollenites X X XMonosulcites XOsmundacidites XTaxodiaceaepollenites X X XKurtzipites trispissatus XQuercus explanata XNyssapollenites albertensis XMomipites sanjuanensis X XMicrofoveolatosporis XDinoflagellate XAlnipollenites XTricolpites vulgaris XRugubivesiculites XEchinatisporis XAquilapollenites XTricolporites rhomboides XGleicheniidites XPseudoplicapollis XCicatricosisporites XCamarozonosporites XKlukisporites XNote: Palynomorphs listed by age; generally youngest to oldest going down; identifications by R. H Tschudy (1977, written commun.); Proteacidites renamed Tschudypollis by Nichols (2002)


125 125

TABLE 12. COMPARISON OF PALYNOMORPH LISTS IDENTIFIED FROM POT MESA AREA SAMPLES (FIGURE 60) ALL SAMPLES FROM CRETACEOUS KIRTLAND FORMATION

Localities D5783-A, -B, -C, -D, -E Locality D6879 Newman locality Identification by R. H. Tschudy (1977) Identification by D. J. Nichols (1994) Identification by K. Newman (1987)

AbietineaepollenitesAequitriraditesAlnipollenitesAquilapollenitesAzolla Azolla cretaceaBalmeisporites BalmeisporitesCamarozonosporites

Chenopodipollis sp.CicatricosisporitesCorollina Corollina torosa


DinoflagellateEchinatisporis

Ephedra multicostataEquisetosporites 5

Erdtmanipollis cretaceaForaminisporis

Fraxinoipollenites variabilisGleicheniidites

Gunnera microreticulata GunneraInterpollis

KlukisporitesKurtzipites trispissatus Kurtzipites trispissatus Kurtzipites

Laevigatosporites sp.Liliacidites Liliacidites complexus

Liliacidites leeiLycopodiaciditesLycopodiumsporitesMicrofoveolatosporisMomipites sanjuanensisMonosulcitesNyssapollenites albertensis

Nyssapollenites sp.Osmundacidites

“Palaeoisoetes” sp.Pandaniidites typicus

PeriporopollenitesProteacidites Proteacidites retusus Proteacidites

Proteacidites thalmanniiPseudoplicapollis

PseudoschizaeaPterospermopsisQuercus explanataRugubivesiculitesTaxodiaceaepollenites

"Tilia" wodehouseiTricolpites vulgarisTricolporites rhomboides

Triporoletes novomexicanumUlmipollenites

Ulmipollenites tricostatusUlmoideipites spp.3 and 4 pored smooth to verrucate forms

cf Vitis affluensZlivisporisNote: Proteacidites renamed Tschudypollis by Nichols (2002); list of palynomorphs identified by Tschudy is composite from five drill-hole samples from drill hole USGS SL 10-1 (Figure 59); palynomorph lists for each sample on Table 11


126 126

TABLE 13.1. UNPUBLISHED PALYNOMORPH LISTS FROM CRETACEOUS USGS PALEOBOTANY LOCALITIES IN AND NEAR OJO ALAMO SANDSTONE TYPE AREA; PALEOBOTANY LOCALITIES SHOWN ON FIGURES 1, 3, and 4

Locality D6902 Locality D6900 Locality D9157 Moncisco Mesa Localities D8179, D8180 (composite)Lowermost Fruitland Fm. Uppermost Fruitland Fm. Upper Kirtland Fm. Uppermost Kirtland Fm. Uppermost Kirtland Fm.

Appendicisporites sp.Aquilapollenites quadrilobus

Aquilapollenites 3 sp. Aquilapollenites sp.Arecipites sp.

Bisaccate coniferCamarozonosporites ambigens Camarozonosporites ambigensCicatricosisporites sp. Cicatricosisporites sp.

Corollina sp. Corollina sp.Corollina torosa

Cupuliferoidaepollenites minutusCupuliferoidaepollenites spp. Cupuliferoidaepollenites spp.Cyathidites minor

Cyathidites spp.Cycadopites sp.

Echinatisporis varispinosus Echinatisporis varispinosusEphedripites sp. D

Erdtmanipollis cretaceusEucommiidites minor

Ghoshispora sp.Gunnera Gunnera microreticulata

Laevigatosporites spp. Laevigatosporites sp.Larger fern tetrad

Liliacidites leei Liliacidites leeiLiliacidites reticulata

Liliacidites sp. Liliacidites sp.Loranthacites

Microreticulatisporites sp.Monocolopopollenites ? s p.

?Monosulcites perspinosus of Anderson (1966)Nyssapollenites sp. Nyssapollenites spp.

Pandaniidites Pandaniidites typicus

Pityosporites spp. Pityosporites spp.Proteacidites retusus Proteacidites retusus Proteacidites retusus

Proteacidites spp. Proteacidites spp. (many) Proteacidites sp.Proteacidites thalmannii

Pseudoplicapollis newmaniiPseudoplicapollis sp.Reticuloidosporites pseudomurii Reticuloidosporites pseudomurii

Rhoipites sp.Stereisporites spp. Stereisporites spp.

Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatusTricolpites spp. Tricolpites spp. Tricolpites sp.Triporopollenites spp.

Triporopollenites tectusTsugaepollenites sp.

Ulmipollenites Ulmipollenites krempii Ulmoideipites krempii

Ulmoideipites tricostatusunidentified trilete spores

Note: Palynomorphs from USGS paleobotany localities D6902, D6900, and Moncisco Mesa identified by R. H. Tschudy (1976, 1983, written communs.); palynomorphidentifications from other localities by D. J. Nichols (1995, 2000 written communs.); Proteacidites renamed Tschudypollis by Nichols (2002).


127 127

TABLE 13.2. UNPUBLISHED PALYNOMORPH LISTS FROM CRETACEOUS USGS PALEOBOTANY LOCALITIES IN AND NEAR THE OJO ALAMO SANDSTONE TYPE AREA (Cont.); PALEOBOTANY LOCALITIES SHOWN ON FIGURES 1, 3, 4, AND 51

Locality D9156-A Locality D9156-B Locality 82303-E Locality 82403-A Locality 110303-D Archival Split 24-5Uppermost Kirtland Fm. Uppermost Kirtland Fm. Uppermost Kirtland Fm. Uppermost Kirtland Fm. Uppermost Kirtland Fm. Uppermost Kirtland Fm.

Arecipites columellus Arecipites columellusArecipites microreticulatus Arecipites microreticulatus Arecipites microreticulatus Arecipites microreticulatusArecipites reticulatus Arecipites reticulatus Arecipites reticulatus Arecipites reticulatusAzolla circinata Azolla circinata Azolla circinata

Azolla cretacea (relatively abundant) Azolla cretacea Azolla cretacea Azolla cretaceaAzolla microspores

Cicatricosisporites sp.Cingulatisporites lancei

Corollina torosa Corollina torosa Corollina torosaCyathidites spp. Cyathidites spp. Cyathidites sp. Cyathidites sp.

Dyadonapites reticulatus Dyadonapites reticulatus Dyadonapites reticulatus Dyadonapites reticulatusForaminisporis undulatus

Ghoshispora spp. (relatively abundant) Ghoshispora sp. Ghoshispora sp. Ghoshispora sp. Ghoshispora sp.Ilexpollenites compactus

Inaperturopollenites sp. Inaperturopollenites sp.Inaperturotetradites scabratus Inaperturotetradites scabratus

Laevigatosporites spp. Laevigatosporites sp. Laevigatosporites sp. Laevigatosporites sp. Laevigatosporites sp.

Liliacidites leei Liliacidites leeiLiliacidites sp. cf. L. complexus Liliacidites sp. cf L. complexusMomipites inaequalis Momipites inaequalis Momipites inaequalis Momipites inaequalis

? Monosulcites perspinosus of Anderson (1966)Osmundacidites stanleyi Osmundacidites stanleyi Osmundacidites stanleyiPalaeoisoetes subengelmannii Palaeoisoetes subengelmannii Palaeoisoetes subengelmanniiPandaniidites typicus Pandaniidites typicus Pandaniidites typicus Pandaniidites typicus

Pityosporites spp. (relatively abundant) Pityosporites spp. (common) Pityosporites sp. Pityosporites spp. (common) Pityosporites sp.Pityosporites typicus

Proteacidites thalmannii Proteacidites sp. cf. P. retususProteacidites thalmanniiRetitriletes sp. ("Lycopodiumsporites")

Rhoipites sp. Rhoipites sp. Rhoipites sp.Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus

Tricolpites interangulus Tricolpites interangulus Tricolpites interangulus Tricolpites interangulus Tricolpites interangulus Tricolpites interangulusTricolpites sp. Tricolpites sp. Tricolpites sp. Tricolpites sp.

Tschudypollis retusus Tschudypollis retusus Tschudypollis retususTschudypollis thalmannii Tschudypollis thalmannii Tschudypollis thalmanniiTschudypollis sp. Tschudypollis sp. Tschudypollis sp. Tschudypollis sp.

Tsugaepollenites sp.Ulmipollenites sp. Ulmipollenites sp.

Ulmoideipites tricostatus Ulmoideipites tricostatusunidentified acritarchs

unidentified dinoflagellate cystsunidentified pollen tetrad unidentified pollen tetrad unidentified pollen tetradunidentified trilete spores unidentified trilete sporesUlmipollenitesNote: Palynomorphs identified by D. J. Nichols (2000, 2003 written communs.)


128 128

TABLE 14. COMPARISON OF PALYNOMORPH LISTS AT USGS PALEOBOTANY LOCALITY D6901 NEAR BARRELSPRING, A PURPORTED SPLIT OF THAT SAMPLE, AND THE D6877 SAN JUAN RIVER LOCALITY (FIGURES 1 AND 51)

Localities D6877-A, -B, -C Locality D6901 (sample 24-5) Locality 6901 ("archival split 24-5")Araucariacites australis

Arecipites microreticulatusArecipites reticulatus Arecipites reticulatusArecipites sp.Azolla cretacea Azolla cretacea Azolla cretaceaBrevicolporites colpellaCorollina torosa (incl. monads and tetrads) Corollina torosa Corollina torosaCupanieidites sp. Cupanieidites sp.Cupuliferoidaepollenites minutus Cupuliferoidaepollenites minutusChenopodipollis sp.Cicatricosisporites spp.Cyathidites minor Cyathidites minor

Cyathidites sp.Dyadonapites reticulatus Dyadonapites reticulatus

Fraxinoipollenites variabilisGhoshispora sp. Ghoshispora sp.

Laevigatosporites sp. Laevigatosporites sp. Laevigatosporites sp.Liliacidites leeiLiliacidites sp.

Momipites inaequalis Momipites inaequalis Momipites inaequalis Momipites sp.

Momipites tenuipolus Momipites tenuipolusNyssapollenites sp.

Osmundacidites stanleyiOsmundacidites wellmannii

“Palaeoisoetes ” sp. “Palaeoisoetes ” sp.“Paliurus ” triplicatus

Palaeoisoetes subengelmanniiPandaniidites typicus Pandaniidites typicus Pandaniidites typicusPityosporites sp. Pityosporites sp. Pityosporites sp.

Rhoipites sp. Rhoipites sp.Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus

Tetraporina sp.Tricolpites? sp. cf. Gunnera Tricolpites interangulus

Tricolpites sp.Proteacidites retusus Tschudypollis retusus

Tschudypollis sp.Proteacidites thalmannii

Tricolpites sp. Tricolpites spp.Triporoletes novomexicanum

Tsugaepollenites sp.Ulmipollenites krempii Ulmipollenites krempii

Ulmipollenites sp.Ulmipollenites tricostatus

unidentified pollen tetradNote: Localities D6877-A, -B, -C (Figure 1, San Juan River site) are the same localities labeled 25Ga, b, c by Fassett and others(2002), composite palynomorph list from Table 10; locality 6901 is same as locality 24-5 in Fassett and others (2002), palynomorph list from Table 10; palynomorphs in list headed Locality 6901 ("archival split 24-5") were identified from a sample reported by Nichols to be a split of original 24-5 sample (all palynomorphs identified by D. J. Nichols, 1994, 2003, writtencommun.); Proteacidites was renamed Tschudypollis by Nichols (2002).


129 129

TABLE 15. PALYNOMORPH LISTS FROM NORTHEAST PART OF SAN JUAN BASIN Locality D5393 Locality D5394 Locality D4119 Locality D5408

Lowermost Fruitland Fm. Lowermost Fruitland Fm. Lowermost Fruitland Fm. Lower Animas Fm.AccuratipollisAlnus 3 pored Alnus 3 pored

AnguloluminosusAquilapollenites senonicus

AppendicisporitesClavatipollenites Clavatipollenites

Cyrilla mimima

Echinatisporis EchinatisporisEngelhardtia typeGleicheniidites Gleicheniidites

IlexpollenitesInterporopollenites Kuylisporites

Liliacidites complexusMicrofoveolatosporis Microfoveolatosporis

MinorpollisMomipites sanjuanensis Momipites sanjuanensis

Momipites tenuipolisMomipites triorbicularis

Monosulcites sp.Phaseolidites stanleyiPolypodiisporites amplus

Proteacidites ProteaciditesStereisporites

Tilaepopollenites sp. (Tilia wodehousei And.)Tricolpites anguloluminosus Tricolpites anguloluminosus

Tricolpites reticulatusTricolpites

Tricolpopollenites sp. ATricolpopollenites sp. BTricolpopollenites sp. CTricolporites sp.

Triporopollenites rugatusTriporopollenites tectusUlmipollenites

Ulmipollenites Vitis affluens

Notes: Samples D5393, 5394, and D5408 (Figure 1) collected by R. T. Ryder, USGS in 1975; palynomorphs identified by R. H. Tschudy(1975 written commun.); palynomorph list by Tschudy for sample D4119 (Figure 1) from Fassett and Hinds (1971) reproduced on Table 7;Proteacidites renamed Tschudypollis by Nichols (2002).


130 130

TABLE 16. COMPOSITE PALYNOMORPH LISTS FOR SOUTHEAST PART OF SAN JUAN BASIN CRETACEOUS (CAMPANIAN) TERTIARY (PALEOCENE)

Fruitland-Kirtland Formation Ojo Alamo Sandstone Nacimiento FormationAbietineaepollenites sp. (Podocarpus northrupi )Abietineaepollenites sp. (Podocarpus sellowiformis)

AcanthotriletesAccuratipollis

Acer striata AequitriraditesAlgal cystsAlnipollenites 4 pored Alnipollenites

Alnus? sp.Aquilapollenites quadrilobusAquilapollenites senonicusAquilapollenites trialatus, var. uniformisAraucariacites sp.Arecipites microreticulatus n. sp.Arecipites Arecipites Arecipites sp.Arecipites reticulatus Arecipites reticulatusBalmeisporitesBisacaccate conifer pollen

Bombacacipites nacimientoensis Bombacacipites nacimientoensisBotryococcus

Brevicolporites colpellaCicatricosisporites

Classopollis sp.Confertisulcites knowltoni Confertisulcites knowltoni

Confertisulcites sp.Corollina

Cupaneidites aff. C. major Cupaneidites aff. C. majorCupaneidites aff. C. reticularis

Cupuliferoidaepollenites minutus Cupuliferoidaepollenites minutusDinoflagellates very few

Fraxinoipollenites variabilis Fraxinoipollenites variabilisEphedra sp. cf. E. volutaEquisetosporites parallel striaeEquisetosporites spiralErdtmannipollis sp.Eucommiidites sp.Extratriporopollenites sp.Fern spores not abundantFoveotriletes scrobicularisFoveosporites sp. cf. F. canalis Gleicheniidites

Gleicheniidites senonicusGranabivesiculites sp.Hystrichospheres very fewIlexpollenitesInaperturopollenites cf. I. hiatus

Intertriletes reticulatusKlukisporitesKurtzipitesKurtzipites trispissatus

Laevigatosporites sp. (Polypodiidites sp.)LecaniellaLiliacidites complexusLiliacidites hyalaciniatus Liliacidites hyalaciniatusLiliacidites leei . Liliacidites leei Liliacidites leeiLiliacidites sp. Liliacidites sp.Liquidambarpollenites sp.

LycopodiaciditesLygodiosporites? sp.

Monoporopollenites sp.Monosulcites perspinosusMonosulcites sp.Navisulcites marginatusNeoraistrickia sp.

Nyssa puercoensisMomipites inaequalis Momipites inaequalis

Momipites sanjuanensisMomipites sp.

Momipites tenuipolus Momipites tenuipolusMonolete fern sporesMonosulcites sp. (Rectosulcites latus )Nyssapollenites sp. Nyssapollenites sp.

Osmundacidites sp.Paliurus triplicatus Paliurus triplicatusPediastrumPeriporopollenites sp. PeriporopollenitesPerotriletes cubensis

"Pinus haploxylon type""Pinus sylvestris type"

Pityosporites sp. Pityosporites sp.Plicapollis?

Podocarpidites cf. P. sellowiformisPodocarpus northropi Podocarpus sellowiformis Podocarpus sellowiformisPodocarpus zuniensis

Pollenites? sp.Polypodiidites spp. Polypodiidites spp. Polypodiidites spp.

Pollyporopollenites sp.PristinuspollenitesPseudoplicapollis?

Psilastephanocolpites sp. Psilastephanocolpites sp.Quadripollis krempii

Quercus explanata "Quercus" explanataQuercus? sp.Rectosulcites latus

RugubivesiculitesRugulatisporites sp.

Salix sp. Salix sp.Siltaria cf. S. scabriextima

Sphagnum sp.Sporites neglectus

Sporites? sp. ATaxodiaceaepollenitesTetracolpites

Tetradites sp.Tilia danei

Tilia wodehouseiTrichopeltinites

Triatriopollenites sp. ATriatriopollenites sp. BTrichotomosulcites contractusTricolpites anguloluminosus Tricolpites anguloluminosus

Tricolpites interangulusTricolpites Tricolpites spp.

Tricolpites sp. ATricolpites sp. B

Tricolpopollenites sp.Tricolpopollenites sp. ATricolpopollenites sp. BTricolpopollenites sp. CTricolpopollenites sp. (Quercus explanata ) Tricolpopollenites sp. (Quercus explanata )

Tricolporites rhomboidesTricolporites sp. Tricolporites sp.

Tricolporites sp. (?Eleagnaceae )Tricolporites traversei

Trilete fern sporesTriletes? sp. A

Triporopollenites plektosus Triporopollenites plektosusTriporopollenites sp. (cf. Casiaromodotes ) Triporopollenites sp. (cf. Casiaromodotes )Triporopollenites tectus Triporopollenites tectus

TrudopollisTschudypollis many, largeTschudypollis retusus Tschudypollis thalmannii Tschudypollis sp.

UlmipollenitesUlmipollenites 3, 4 pored

Ulmipollenites sp. (Ulmoideipites tricostatus )Ulmoideipites krempi Ulmoideipites krempi Ulmoideipites planeraeformis

Ulmoideipites tricostatus Ulmoideipites tricostatus Ulmoideipites tricostatusZonalapollenites sp.Zlivisporis novomexicanum Zlivisporis novomexicanumZlivisporis sp. Zlivisporis sp.Note: Fruitland-Kirtland palynomorph list is composite of Kirtland Shale florule from Table 5, localities D3738-C and D4017-A, -B, and -C fromTable 7, and localities D6626-A, -B, -C and D6582 from Table 9; Ojo Alamo list is composite from Ojo Alamo florules 1 and 2 from Table 5,localities D3738-A, -B fromTable 7; and localities D6583-A, -B from Table 9; Nacimiento list is a composite of Nacimiento florules 1 and 2 fromTable 5, locality D3803 from Table 7, and locality D6878 from Table 9; palynomrph authorships not shown on this and succeeding tables.


131 131

TABLE 17. COMPOSITE LIST OF PALYNOMORPHS FROM KIRTLAND FORMATION, POT MESA AREA

AbietineaepollenitesAequitriraditesAlnipollenitesAquilapollenitesAzolla Azolla cretaceaBalmeisporitesCamarozonosporitesChenopodipollis sp.CicatricosisporitesCorollina Corollina torosa Cupanieidites sp.Cupuliferoidaepollenites minorCyathidites minorDinoflagellateEchinatisporisEphedra multicostataEquisetosporites 5Erdtmanipollis cretaceaForaminisporisFraxinoipollenites variabilisGleicheniiditesGunnera microreticulataKlukisporitesKurtzipites trispissatusLiliaciditesLiliacidites complexusLiliacidites leeiLycopodiaciditesLycopodiumsporitesMicrofoveolatosporisMomipites sanjuanensisMonosulcitesNyssapollenites albertensisNyssapollenites sp.Osmundacidites“Palaeoisoetes” sp.Pandaniidites typicusPeriporopollenitesProteaciditesProteacidites retususProteacidites thalmanniiPseudoplicapollisPseudoschizaeaPterospermopsisQuercus explanataRugubivesiculitesTaxodiaceaepollenites"Tilia" wodehouseiTricolpites vulgarisTricolporites rhomboidesTriporoletes novomexicanumUlmipollenitesUlmipollenites tricostatusUlmoideipites spp., 3 and 4 pored, smooth to verrucate formscf Vitis affluensZlivisporisNote: Palynomorphs represent a composite list of taxa fromCretaceous Kirtland Formation shown on Table 12.Proteacidites is now named Tschudypollis.


132 132

TABLE 18. COMPOSITE PALYNOMORPH LISTS FROM OJO ALAMO SANDSTONE TYPE AREA CRETACEOUS PALEOCENE

Fruitland Formation Kirtland Formation Uppermost Kirtland Formation Upper Ojo Alamo Lowermost Nacimiento Fm.Algal cysts

Appendicisporites sp. Appendicisporites sp.Aquilapollenites quadrilobusAquilapollenites 3 sp.

Araucariacites australisArecipites columellasArecipites microreticulatusArecipites reticulatus Arecipites reticulatus Arecipites reticulatus Arecipites cf. A. reticulatus

Arecipites sp. Arecipites spAzolla circinataAzolla cretacea [relatively abundant] Azolla cretaceaAzolla microspores

Azolla cf. A schopfiBissacate conifer

Brevicolporites colpellaCamarozonosporites ambigens

Cercidiphyllites sp.Chenopodipollis sp.

Cingulatisporites lanceiCicatricosisporites sp. Cicatricosisporites sp.

Corollina sp.Corollina torosa Corollina torosa Corollina torosa Corollina torosa

Cupaneidites aff. C. major Cupaneidites cf. C. majorCupanieidites sp. Cupaniedidites sp.

Cupuliferoidaepollenites minutus Cupuliferoidaepollenites minutus Cupuliferoidaepollenites minutusCupuliferoidaepollenites spp.Cyathidites minor Cyathidites minor

Cyathidites spp.Cycadopites fragillisCycadopites sp.Dyadonapites reticulatus Dyadonapites reticulatus

Echinatisporis varispinosusEphedripites sp. D

Erdtmanipollis cretaceusEucommiidites minor

Foraminisporis undulatusFraxinoipollenites variabilis

Ghoshispora sp. Ghoshispora sp.GunneraGunnera microreticulataIlexpollenites compactusInaperturopollenites sp.Inaperturotetradites scabratus

Laevigatosporites spp. Laevigatosporites sp. Laevigatosporites sp. Laevigatosporites spp.Larger fern tetradLiliacidites hyalacinatus?

Liliacidites leei Liliacidites leei Liliacidites leeiLiliacidites reticulata

Liliacidites sp. Liliacidites sp. Liliacidites sp.Liliacidites sp. cf L. complexusLoranthacites

Microreticulatisporites sp.Momipites inaequalis Momipites inaequalis Momipites inaequalis

Momipites sp. Momipites sp. MomipitesMomipites tenuipolus Momipites tenuipolus

Monocolopopollenites? sp.? Monosulcites perspinosus

Nyssapollenites sp.Osmundacidites stanleyi

Osmundacidites wellmanniiOvoidites sp

“Palaeoisoetes” sp. “Palaeoisoetes” sp.Palaeoisoetes subengelmannii

"Paliurus” triplicatus Paliurus triplicatus ?Pandaniidites

Pandaniidites radicusPandaniidites typicus Pandaniidites typicus Pandaniidites typicusPityosporites constrictusPityosporites spp. Pityosporites sp. Pityosporites sp.Pityosporites typicus

Podocarpus sp. Podocarpus sp.Polypodiisporonites sp.

Pseudoplicapollis newmaniiPseudoplicapollis sp.

Psilastephanocolpites sp.“Quercus” explanataQuercus sp.

Reticuloidosporites pseudomuriiRectosulcites latus

Retitriletes sp. ("Lycopodiumsporites")Rhoipites sp. Rhoipites sp.

Schizosporis parvusStereisporites spp.

Syncolporites minimusTaxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus

Tetracolpites 2 sp.Tetraporina sp.

Tricolpites anguloluminosusTricolpites foveolate

Tricolpites? sp.cf GunneraTricolpites interangulusTricolpites microreticulatusTricolpites reticulatus

Tricolpites scabrateTricolpites spp. Tricolpites sp. Tricolpites spp.

Tricolporites rhomboidesTriporopollenites spp.Triporopollenites tectusTschudypollis retusus Tschudypollis retusus Tschudypollis retussus (reworked)Tschudypollis sp. Tschudypollis spp. (many)

Tschudypollis thalmannii Tschudypollis thalmannii (reworked)Tsugaepollenites sp.Ulmipollenites

Ulmipollenites krempii Ulmipollenites krempii Ulmipollenites krempii Ulmipollenites krempiiUlmipollenites sp.

Ulmipollenites 3 and 4 pored.Ulmoideipites krempii("Ulmoideipites") tricostatus Ulmoideipites tricostatus Ulmoideipites tricostatusunidentified acritarchsunidentified dinoflagellate cystsunidentified pollen tetradunidentified trilete spores

Notes: Composite palynomorph lists are based on palynomoph lists on Tables 6, 13.1, and 13.2; the Paleocene Uppermost Kirtland Formation list is from locality D6901.


133 133

TABLE 19. COMPOSITE LIST OF PALYNOMORPHS IDENTIFIED FROM SAN JUAN RIVER LOCALITYKirtland Formation - Cretaceous Ojo Alamo Sandstone - Paleocene

Alisporites bilateralis Arecipites reticulatusArecipites sp.Azolla cretacea

BalmeisporitesBrevicolporites colpellaChenopodipollis sp.Cicatricosisporites spp.Lycopodium novomexicanumMomipites inaequalisMomipites tenuipolusCorollina torosa (incl. monads and tetrads)Cupanieidites cf. C. reticularis Cupuliferoidaepollenites minutusCyathidites minorCycadopites fragilis Equisetosporites lajwantis Fraxinoipollenites variabilis

GunneraInterpollisKurtzpites

Laevigatosporites sp.Laevigatosporites haardti Momipites inaequalisMomipites inaequalisMomipites tenuipolusNyssapollenites sp.Nyssapollenites explanatus Ovoidites ligneolus “Palaeoisoetes ” sp.“Paliurus ” triplicatusPandaniiditesPandaniidites typicusPityosporites sp.Rectosulcites latusSchizosporis parvus Taxodiaceapollenites hiatus Taxodiaceapollenites vacupites Tricolpites sp.Triporoletes novomexicanumTriporoletes simplex

Tschudypollis Tschudypollis (reworked)Tschudypollis thalmanni (reworked)Ulmipollenites krempiiU. tricostatusUlmoideipites krempi

Ulmoideipites spp. 3 and 4 pored smooth to verrucate formsZlivisporis novomexicanum

Note: Palynomorph lists are from Table 10


134 134

TABLE 20. COMPOSITE PALYNOMORPH LISTS FROM NORTHEAST SAN JUAN BASIN

Lowermost Fruitland Fm. (Cretaceous) Lower Animas Fm. (Paleocene)AccuratipollisAlnus 3 pored Alnus 3 poredAquilapollenites senonicusAppendicisporitesClavatipollenitesCyrilla mimimaEchinatisporisEngelhardtia typeGleicheniiditesIlexpollenitesInterporopollenites KuylisporitesLiliacidites complexusMicrofoveolatosporisMinorpollisMomipites sanjuanensis

Momipites tenuipolisMomipites triorbicularis

Monosulcites sp.Phaseolidites stanleyiPolypodiisporites amplusStereisporitesTilaepopollenites sp. (Tilia wodehousei And.)

Tricolpites Tricolpites anguloluminosus Tricolpites anguloluminosusTricolpites reticulatusTricolopopollenites sp. ATricolopopollenites sp. BTricolopopollenites sp. CTricolporites sp.Triporopollenites rugatusTriporopollenites tectusTschudypollisUlmipollenites Ulmipollenites Vitis affluensNote: Palynomorphs listed are from Table 15


135 135

TABLE 21. COMPOSITE PALYNOMORPH LISTS FROM FRUITLAND FORMATION, SAN JUAN BASIN, NEW MEXICO Ojo Alamo Ss Type Area Mesa Portales Area Gasbuggy Core Northeast SJ Basin

AcanthotriletesAccuratipollis Accuratipollis spp. AccuratipollisAequitriaradites Aequitriradites sp.

Aequitriradites spinulosusAlgal cystsAlnipollenites 4 pored

Alnus 3 poredAlsophilidites sp.

Appendicisporites sp. Appendicisporites spp. AppendicisporitesAquila 4 EAquila 17Aquila 18Aquila 36 CAquila 42Aquilapollenites attenuatusAquilapollenites delicatus

Aquilapollenites quadrilobus Aquilapollenites quadrilobusAquilapollenites senonicus Aquilapollenites senonicus Aquilapollenites senonicusAquilapollenites trialatus, var uniformis

Aquilapollenites turbidusAraucariacites sp. AraucariacitesArecipites microreticulatus Arecipites reticulatus

Arecipites sp. ArecipitesBalmeisporitesBisacaccate conifer pollenBotryococcus

Camarozonosporites ambigensCamarozonosporites spp.

Cicatricosisporites sp. Cicatricosisporites Cicatricosisporites spp.Clavatipollenites

cf. Concavisporites verrucosusConfertisulcites knowltoni Corollina

Corollina torosaCupaniedites aff. C. reticularis

Cupuliferoidaepollenites minutusCupuliferoidaepollenites spp.Cyathidites minor

Cyrilla mimimaDinoflagellates very few

EchinatisporisEchinatisporis varispinosus

Engelhardtia typeEphedra sp. cf. E. voluta

Ephedripites sp. DEquisetosporites parallel striaeEquisetosporites spiralErdtmannipollis sp.

Eucommiidites minorEucommiidites sp. Eucommiidites sp.Extratriporopollenites sp.Fern spores not abundant

Foraminisporis sp.Foveotriletes scrobicularisFoveosporites sp. cf. F. canalisGleicheniidites Gleicheniidites spp. Gleicheniidites

Ghoshispora spp.Granabivesiculites sp.Hystrichospheres very fewIlexpollenites Ilexpollenites sp. IlexpollenitesInaperturopollenites cf. I. hiatus

Interporopollenites Klukisporites Klukisporites spp.

Kuylisporites sp. KuylisporitesKurtzipitesKurtzipites trispissatus Kurtzipites trispissatus

Laevigatosporites spp.Lecaniella

Leptolepidites majorLiliacidites complexus Liliacidites complexusLiliacidites hyalaciniatus

Liliacidites leei Liliacidites leei Liliacidites sp. Liliacidites sp. Liliacidites spp.

Liquidambarpollenites sp.Lycopodiacidites kuepperiLycopodiacidites spp.Lycopodiumsporites spp.Microfoveolatosporis canaliculatus

MicrofoveolatosporisMicroreticulatisporites sp. Microreticulatisporites sp.

cf. Minorpollis MinorpollisMomipites sanjuanensis

Monocolopopollenites ? s p.Monoporopollenites sp.Monosulcites perspinosusMonosulcites sp. Monosulcites sp.Navisulcites marginatus Neoraistrickia sp.

Nyssapollenites sp.Momipites sanjuanensisMomipites sp.Paliurus triplicatus PediastrumPeriporopollenites sp.Perotriletes cubensis

Phaseoliidites stanleyi Phaseolidites stanleyiPlicapollis?Pollenites? sp.Polypodiidites spp. Polypodiidites sp.

Polypodiisporites amplus Polypodiisporites amplusPolypodiisporites sp.

PristinuspollenitesPseudoplicapollis?

Pseudoplicapollis newmaniiPseudoplicapollis sp.

Quadripollis krempiicf. Radialetes costatus

Reticuloidosporites pseudomuriiRhoipites sp.

RugubivesiculitesSphagnum sp.Sporites? sp. A

Stereisporites spp. StereisporitesSubtriporopollenites sp.cf. Taurocusporites

TaxodiaceaepollenitesTaxodiaceaepollenites hiatus

TetracolpitesTilaepopollenites sp. (Tilia wodehousei )

Tilia wodehousei cf. Tilia wodehouseiToroisporis sp.

TrichopeltinitesTricolpites anguloluminosus

Tricolpites hiansTricolpites interangulus Newman

Tricolpites reticulatus Tricolpites reticulatusTricolpites sp. A

Tricolpites spp. Tricolpites sp.Tricolpopolleinites sp.Tricolpopolleinites sp. A Tricolpopollenites sp. ATricolpopolleinites sp.B Tricolpopollenites sp. BTricolpopollenites sp. C Tricolpopollenites sp. CTricolpopollenites sp. (Quercus explanata )Tricolporites sp. Tricolporites sp.Tricolporites traverseiTriletes? sp. A

Triplanosporites sp.Triporopollenites rugatus

Triporopollenites spp.Triporopollenites tectus Triporopollenites tectus

Trudopollis meekeriTrudopollis Trudopollis sp.Tschudypollis many, large

Tschudypollis retusus Tschudypollis retususTschudypollis thalmanni

Tschudypollis sp. Tschudypollis sp. Tschudypollis sp. TschudypollisUlmipollenites

Ulmipollenites krempiiUlmipollenites 3, 4 poredUlmoideipites tricostatus

Vitis? AffluensZonalapollenites sp. ZonalapollenitesZlivisporis novomexicanumZlivisporis sp. cf. Zlivisporis

Note: Palynomorphs listed are from Tables 8, 16, 18, and 20


136 136

TABLE 22. COMPOSITE LISTS OF PALYNOMORPHS FROM KIRTLAND FORMATIONOjo Alamo Type Area Pot Mesa Locality

AbietineaepollenitesAppendicisporites sp.

AequitriraditesAlnipollinites

Aquilapollenites 3 sp. AquilapollenitesAquilapollenites quadrilobusArecipites columellasArecipites microreticulatusArecipites reticulatus

Azolla Azolla circinataAzolla cretacea (relatively abundant) Azolla cretaceaAzolla microspores

BalmeisporitesBissacate conifer

CamarozonosporitesChenopodipollis sp.

Cicatricosisporites sp. CicatricosisporitesCingulatisporites lanceiCorollina sp. Corollina Corollina torosa Corollina torosa


Cyathidites spp.Cycadopites fragillisCycadopites sp.

DinoflagellateDyadonapites reticulatus

EchinatisporisEphedra multicostataEquisetosporites 5

Erdtmanipollis cretaceus Erdtmanipollis cretaceaForaminisporis

Foraminisporis undulatusFraxinoipollenites variabilis

Ghoshispora sp.Gleicheniidites

GunneraGunnera microreticulata Gunnera microreticulataIlexpollenites compactusInaperturopollenites sp.Inaperturotetradites scabratus

KlukisporitesKurtzipites trispissatus

Laevigatosporites sp.Larger fern tetrad

LiliaciditesLiliacidites complexus

Liliacidites hyalacinatus?Liliacidites leei L. leeiLiliacidites reticulataLiliacidites sp.Liliacidites sp. cf L. complexusLoranthacites

Lycopodiacidites


137 137

LycopodiumsporitesMicrofaveolatisporis

Momipites inaequalis Momipites sanjuanensisMonosulcites

?Monosulcites perspinosusNyssapollenites albertensisNyssapollenites sp.Osmundacidites

Osmundacidites stanleyi“Palaeoisoetes ” sp.

Palaeoisoetes subengelmanniiPandaniidites Pandaniidites typicus Pandaniidites typicus

PeriporopollenitesPityosporites constrictusPityosporites spp.Pityosporites typicus

PseudoplicapollisPseudoschizaeaPterospermopsisQuercus explanata

Retitriletes sp. ("Lycopodiumsporites ")Rugubivesiculites

Schizosporis parvusTaxodiaceaepollenites

Taxodiaceaepollenites hiatusTilia wodehousei

Tricolpites interangulusTricolpites microreticulatusTricolpites reticulatusTricolpites sp.

Tricolpites vulgarisTricolporites rhomboidesTriporoletes novomexicanum

Tschudypollis retusus Tschudypollis retususTschudypollis spp. (many) Tschudypollis spp.Tschudypollis spp. Tschudypollis spp.Tsugaepollenites sp.Ulmipollenites UlmipollenitesUlmipollenites krempiiUlmipollenites sp.

Ulmipollenites tricostatus("Ulmoideipites") tricostatus

Ulmoideipites spp. 3 and 4 pored smooth to verrucate formsunidentified acritarchsunidentified dinoflagellate cystsunidentified pollen tetradunidentified trilete spores

cf Vitis affluensZlivisporis

Note: Palynomorphs listed are from Tables 17 and 18.


138 138

TABLE 23. COMPARISON OF PALYNOMORPHS FROM KIRTLAND AND FRUITLAND FORMATIONS FROM ALL S.J. BASIN LOCALITIESFruitland Formation Kirtland Formation Fruitland Formation (continued) Kirtland Formation (continued)

Abietineaepollenites Liquidambarpollenites sp.Acanthotriletes LoranthacitesAccuratipollis Lycopodiacidites kuepperiAequitriaradites Aequitriradites Lycopodiacidites spp. LycopodiaciditesAequitriradites spinulosus Lycopodiumsporites spp. LycopodiumsporitesAlgal cysts Microfoveolatosporis Microfoveolatosporis

Alnipollinites Microfoveolatosporis canaliculatusAlnipollenites 4 pored Microreticulatisporites sp.Alnus 3 pored cf. MinorpollisAlsophilidites sp. Momipites inaequalis Appendicisporites spp. Appendicisporites sp. Momipites sanjuanensis Momipites sanjuanensisAquila 4 E Momipites sp.Aquila 4 E Monocolopopollenites? sp.Aquila 18 Monoporopollenites sp.Aquila 36 C Monosulcites perspinosus Aquila 42 Monosulcites sp. Monosulcites

Aquilapollenites 3 sp. ?Monosulcites perspinosusAquilapollenites attenuatus Navisulcites marginatus Aquilapollenites delicatus Neoraistrickia sp.Aquilapollenites quadrilobus Aquilapollenites quadrilobus Nyssapollenites albertensisAquilapollenites senonicus Nyssapollenites sp. Nyssapollenites sp.Aquilapollenites trialatus, var uniformis OsmundaciditesAquilapollenites turbidus Osmundacidites stanleyiAraucariacites sp. “Palaeoisoetes” sp.Arecipites Palaeoisoetes subengelmannii

Arecipites columellas Paliurus triplicatus Arecipites microreticulatus Arecipites microreticulatus Pandaniidites Arecipites reticulatus Arecipites reticulatus Pandaniidites typicus

Azolla PediastrumAzolla circinata Periporopollenites sp. PeriporopollenitesAzolla cretacea (relatively abundant) Perotriletes cubensis Azolla microspores Phaseoliidites stanleyi

Balmeisporites Pityosporites constrictusBisacaccate conifer pollen Bissacate conifer Pityosporites spp.Botryococcus Pityosporites typicusCamarozonosporites ambigens Plicapollis ?Camarozonosporites spp. Camarozonosporites Pollenites? sp.

Chenopodipollis sp. Polypodiidites spp.Cicatricosisporites Cicatricosisporites sp. Polypodiisporites amplus

Cingulatisporites lancei Polypodiisporites sp.Clavatipollenites Pristinuspollenitescf. Concavisporites verrucosus Pseudoplicapollis? PseudoplicapollisConfertisulcites knowltoni Pseudoplicapollis newmaniiCorollina Corollina sp. Pseudoplicapollis sp.Corollina torosa Corollina torosa Pseudoschizaea

Cupanieidites sp. PterospermopsisCupaniedites aff. C. reticularis Quadripollis krempii

Cupuliferoidaepollenites minor Quercus explanataCupuliferoidaepollenites minutus cf Radialetes costatusCupuliferoidaepollenites minutus cf. Radialetes costatusCupuliferoidaepollenites spp. Reticuloidosporites pseudomuriiCyathidites minor Cyathidites minor Retitriletes sp. ("Lycopodiumsporites")

Cyathidites spp. Rhoipites sp.Cycadopites fragillis Rugubivesiculites RugubivesiculitesCycadopites sp. Schizosporis parvus

Cyrilla mimima Sphagnum sp.Dinoflagellates very few Dinoflagellate Sporites? sp. A

Dyadonapites reticulatus Stereisporites spp.Echinatisporis Echinatisporis Subtriporopollenites sp.Echinatisporis varispinosus cf. TaurocusporitesEngelhardtia type Taxodiaceaepollenites Taxodiaceaepollenites

Ephedra multicostata Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatusEphedra sp. cf. E. voluta TetracolpitesEphedripites sp. D Tilia wodehousei Tilia wodehousei

Equisetosporites 5 Toroisporis sp.Equisetosporites parallel striae TrichopeltinitesEquisetosporites spiral Tricolpites anguloluminosus

Erdtmanipollis cretaceus Tricolpites hiansErdtmannipollis sp. Tricolpites interangulus Newman Tricolpites interangulusEucommiidites minor Tricolpites microreticulatusEucommiidites sp. Tricolpites reticulatus Tricolpites reticulatusExtratriporopollenites sp. Tricolpites spp. Tricolpites sp.Fern spores not abundant Tricolpites sp. AForaminisporis sp. Foraminisporis Tricolpites vulgaris

Foraminisporis undulatus Tricolpopolleinites sp.Foveotriletes scrobicularis Tricolpopolleinites sp. AFoveosporites sp. cf. F. canalis Tricolpopolleinites sp.B

Fraxinoipollenites variabilis Tricolpopollenites sp. CGhoshispora spp. Ghoshispora sp. Tricolpopollenites sp. (Quercus explanata)Gleicheniidites Gleicheniidites Tricolporites rhomboidesGranabivesiculites sp. Tricolporites sp.

Gunnera Tricolporites traverseiGunnera microreticulata Triletes? sp. A

Hystrichospheres very few Triplanosporites sp.Ilexpollenites Triporoletes novomexicanum

Ilexpollenites compactus Triporopollenites rugatusInaperturopollenites sp. Triporopollenites spp.

Inaperturopollenites cf. I. hiatus Triporopollenites tectusInaperturotetradites scabratus Trudopollis

Interporopollenites Trudopollis meekeriKlukisporites Klukisporites Tschudypollis retusus Tschudypollis retususKlukisporites spp. Tschudypollis many, large Tschudypollis spp. (many)Kurtzipites Tschudypollis thalmanni Tschudypollis thalmanniiKurtzipites trispissatus Kurtzipites trispissatus Tsugaepollenites sp.Laevigatosporites spp. Laevigatosporites sp. Ulmipollenites Ulmipollenites

Larger fern tetrad Ulmipollenites 3, 4 poredLecaniella Ulmipollenites krempii Ulmipollenites krempiiLeptolepidites major Ulmipollenites sp.Liliacidites complexus Liliacidites complexus Ulmoideipites tricostatus ("Ulmoideipites") tricostatusLiliacidites hyalaciniatus Liliacidites hyalacinatus? Ulmoideipites spp.3 and 4 pored smooth to verrucate formsLiliacidites leei Liliacidites leei Vitis ? affluens (C3-r 43) cf Vitis affluens

Liliacidites reticulata Zlivisporis novomexicanumLiliacidites sp. Liliacidites sp. Zlivisporis sp. Zlivisporis

Liliacidites sp. cf L. complexus Zonalapollenites sp.Note: Palynomorphs listed are from Tables 21 and 22; Fruitland-Kirtland palynomorph zonation shown on Figure 64.


139 139

TABLE 24. COMPOSITE PALYNOMORPH LISTS FROM PALEOCENE OJO ALAMO SANDSTONE, SAN JUAN BASIN, NEW MEXICO San Juan River Locality Ojo Alamo Ss Type Area Southeast SJ Basin Gasbuggy Core

Abietineaepollenites sp. (Podocarpus northrupi )Abietineaepollenites sp. (Podocarpus sellowiformis )Acer striata

Algal cystsAlisporites bilateralis

Aquilapollenites spp.Araucariacites australis

Arecipites reticulatus Arecipites reticulatus Arecipites reticulatus Arecipites sp. Arecipites sp Arecipites sp. Arecipites spp.Azolla cretacea Azolla cretacea

Azolla cf. A schopfiBiretisporites sp.

Bombacapites nacimientoensis Brevicolporites colpella Brevicolporites colpella

Cercidiphyllites sp.Chenopodipollis sp. Chenopodipollis sp.Cicatricosisporites spp.

Classopollis sp.Corollina torosa (incl. monads and tetrads) Corollina torosa

Cupaneidites aff. C. major Cupaniedites aff. C. major Cupanieidites majorCupanieidites cf. C. reticularis

Cupaniedidites sp. cf. CupanieiditesCupuliferoidaepollenites minutus Cupuliferoidaepollenites minutus Cupuliferoidaepollenites minutusCyathidites minor Cyathidites minorCycadopites fragilis

Cyathidites spp.Cyrilla minimaDeltoidospora spp.

Dyadonapites reticulatusEchinatisporis sp.Engelhardtia type

Equisetosporites lajwantis cf Ephedra volutaEquisetosporites spp.Ericaceoipollenites sp.Formaminisporis spp.

Fraxinoipollenites variabilis Fraxinoipollenites variabilis Fraxinoipollenites variablisGhoshispora sp.

Gleicheniidites senonicusHystrichosphaerids & dinoflagellates

Laevigatosporites haardti Laevigatosporites sp. Laevigatosporites spp. Laevigatoporites sp.

Liliacidites leei Liliacidites leei Liliacidites sp.

Momipites inaequalis Momipites inaequalis Momipites inaequalisMomipites sanjuanensis

Momipites sp.Momipites tenuipolus Momipites tenuipolus Momipites tenuipolus Momipites tenuipolus Nyssapollenites explanatus Nyssapollenites sp. Nyssapollenites sp.

Nyssa puercoensis Nyssa puercoensis Osmundacidites wellmannii

Ovoidites ligneolus Ovoidites sp

“Palaeoisoetes” sp. “Palaeoisoetes” sp.“Paliurus” triplicatus "Paliurus” triplicatusPandaniidites

Pandaniidites radicus Pandaniidites radicusPandaniidites typicus Pandaniidites typicus

Periporopollenites sp.Pityosporites sp. Pityosporites sp. Pitysporites sp.

Podocarpus sellowiformisPodocarpus sp.

Polypodiidites spp.Polypodiisporonites sp.Psilastephanocolpites sp. Psilastephanocolpites sp.

Quadrapollenites sp.“Quercus” explanata Quercus explanata Quercus explanataQuercus sp.

Rectosulcites latus Rectosulcites latusSalix sp.

Schizosporis parvus Stereisporites spp.

Syncolporites minimusTaxodiaceaepollenites hiatus

Taxodiaceaepollenites sp.Taxodiaceaepollenites vacupites

Tetracolpites 2 sp.Tricolpites anguloluminosus Tricolpites anguloluminosus Tricolpites anguloluminosusTricolpites foveolateTricolpites scabrate

Tricolpites vulgarisTricolpites sp. Tricolpites spp. Tricolpites sp.

Tricolporites rhomboides Tricolporites rhomboides Tricolporites rhomboidesTricolporites sp.

Triporoletes novomexicanumTriporoletes simplex

Triporopollenites plektosus cf. Triporopollenites rugatus

Triporopollenites sp. (cf. Casiaromodotes )Triporopollenites tectus

Tschudypollis (reworked) Tschudypollis spp. (reworked)Tschudypollis thalmanni (reworked)Ulmipollenites krempii Ulmipollenites krempii

Ulmipollenites 3 and 4 pored. Ulmipollenites spp.Ulmoideipites krempi

Ulmoideipites tricostatus Ulmoideipites tricostatus Ulmoideipites tricostatusUnclassified bisaccatesUnclassified triletesUnclassified triporatesVitis? affluens

Zlivisporis novomexicanum Zlivisporis novomexicanumZlivisporis sp.

Note: Palynomorphs from San Juan River site from Table 19; from O.A. type area, Table 18; from S.E. San Juan Basin, Table 16, and from Gasbuggycore, Table 8


140 140

TABLE 25. COMPOSITE PALYNOMORPH LISTS FOR CRETACEOUS AND PALEOCENE STRATA, SAN JUAN BASINCretaceous - Campanian Lowermost Paleocene Cretaceous - Campanian (Cont.) Lowermost Paleocene (Cont.)

Abietineaepollenites Momipites sanjuanensis Momipites sanjuanensisAbietineaepollenites sp. (Podocarpus northrupi ) Momipites sp. Momipites sp.Abietineaepollenites sp. (Podocarpus sellowiformis ) Momipites tenuipolus

Acanthotriletes Monocolopopollenites? sp.Accuratipollis Monoporopollenites sp.

Acer striata Monosulcites perspinosusAequitriradites Monosulcites sp.Aequitriradites spinulosus Navisulcites marginatus Algal cysts Algal cysts Neoraistrickia sp.

Alisporites bilateralis Nyssapollenites albertensisAlnipollenites 4 pored Nyssapollenites explanatus Alnus 3 pored Nyssapollenites sp. Nyssapollenites sp.Alsophilidites sp. Nyssa puercoensis Appendicisporites spp. OsmundaciditesAquilapollenites attenuatus Osmundacidites stanleyiAquilapollenites delicatus Osmundacidites wellmanniiAquilapollenites quadrilobus Ovoidites ligneolus Aquilapollenites senonicus Ovoidites sp.Aquilapollenites sp. Aquilapollenites spp. “Palaeoisoetes” sp.Aquilapollenites trialatus, var. uniformis Palaeoisoetes subengelmanniiAquilapollenites turbidus Paliurus triplicatus “Paliurus” triplicatus

Araucariacites australis PandaniiditesAraucariacites sp. Pandaniidites radicusArecipites columellus Pandaniidites typicus Pandaniidites typicusArecipites microreticulatus PediastrumArecipites reticulatus Arecipites reticulatus Periporopollenites sp. Periporopollenites sp.Arecipites Arecipites sp. Perotriletes cubensis Azolla circinata Phaseoliidites stanleyiAzolla cretacea Azolla cretacea Pityosporites constrictusAzolla microspores Pityosporites spp. Pityosporites sp.

Azolla cf. A. schopfi Pityosporites typicusBalmeisporites Plicapollis?

Biretisporites sp. Podocarpus sellowiformisBisacaccate conifer pollen Podocarpus sp.

Bombacacipites nacimientoensis Pollenites? sp.Botryococcus Polypodiidites spp. Polypodiidites spp.

Brevicolporites colpella Polypodiisporites amplusCamarozonosporites ambigens Polypodiisporites sp.Camarozonosporites spp. Polypodiisporonites sp.

Cercidiphyllites sp. PristinuspollenitesChenopodipollis sp. Chenopodipollis sp. Pseudoplicapollis?Cicatricosisporites sp. Cicatricosisporites spp. Pseudoplicapollis newmaniiCingulatisporites lancei Pseudoschizaea

Classopollis sp. Pseudoplicapollis sp.Clavatipollenites Psilastephanocolpites sp.cf. Concavisporites verrucosus PterospermopsisConfertisulcites knowltoni Quadrapollenites sp.Corollina Quadripollis krempiiCorollina torosa Corollina torosa (incl. monads and tetrads) Quercus explanata “Quercus” explanata

Cupanieidites aff. C. major Quercus sp.Cupanieidites aff. C. reticularis Cupanieidites cf. C. reticularis cf. Radialetes costatus

Cupanieidites sp. Rectosulcites latusCupuliferoidaepollenites minor Reticuloidosporites pseudomuriiCupuliferoidaepollenites minutus Cupuliferoidaepollenites minutus Retitriletes sp. ("Lycopodiumsporites")Cupuliferoidaepollenites spp. Rhoipites sp.Cyathidites minor Cyathidites minor RugubivesiculitesCyathidites spp. Salix sp.Cycadopites fragillis Cycadopites fragilis Schizosporis parvus Schizosporis parvusCycadopites fragillis Cycadopites fragilis Schizosporis parvus Schizosporis parvus Cycadopites sp. Sphagnum sp.

Cyrilla minima Sporites? sp.Deltoidospora spp. Stereisporites spp. Stereisporites spp.

Dinoflagellates Subtriporopollenites sp.Dyadonapites reticulatus Dyadonapites reticulatus Syncolporites minimusEchinatisporis Echinatisporis sp. cf. TaurocusporitesEchinatisporis varispinosus Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus Engelhardia type Engelhardtia type Taxodiaceaepollenites Taxodiaceaepollenites sp.Ephedra multicostata Taxodiaceaepollenites vacuipites Ephedra sp. c f. E. voluta cf. Ephedra voluta Tetracolpites Tetracolpites 2 sp.Ephedripites sp. Tilaepopollenites sp. (Tilia wodehousei )

Equisetosporites lajwantis cf. Tilia wodehouseiEquisetosporites parallel striae Toroisporis sp.Equisetosporites spiral TrichopeltinitesEquisetosporites sp. Equisetosporites spp. Tricolpites anguloluminosus Tricolpites anguloluminosusErdtmanipollis cretaceus Tricolpites foveolateErdtmannipollis sp. Tricolpites hians

Ericaceoipollenites sp. Tricolpites interangulus NewmanEucommiidites minor Tricolpites microreticulatusEucommiidites sp. Tricolpites reticulatusExtratriporopollenites sp. Tricolpites sp. AFern spores not abundant Tricolpites scabrateForaminisporis sp. Foraminisporis spp. Tricolpites spp. Tricolpites spp.Foraminisporis undulatus Tricolpites vulgarisFoveotriletes scrobicularisFoveosporites sp. Cf. F. canalis Tricolpopollenites sp.Fraxinoipollenites variabilis Fraxinoipollenites variabilis Tricolpopollenites sp. (Quercus explanata )Ghoshispora spp. Ghoshispora sp. Tricolporites sp.

Gleicheniidites senonicus Tricolporites traverseiGleicheniidites spp. Tricolporites rhomboidesGranabivesiculites sp. Tricolporites sp. Gunnera microreticulata Triletes? sp. Hystrichospheres Hystrichosphaerids & dinoflagellates Triplanosporites sp.Ilexpollenites compactus Triporoletes novomexicanum Triporoletes novomexicanumInterporopollenites Triporoletes simplex Inaperturopollenites cf. I. hiatus Triporopollenites rugatusInaperturotetradites scabratus Triporopollenites plektosus Klukisporites cf. Triporopollenites rugatusKurtzipites Triporopollenites spp. Triporopollenites sp.Kurtzipites trispissatus Triporopollenites sp. (cf. Casiaromodotes )Kuylisporites sp. Triporopollenites tectus Triporopollenites tectus

Laevigatosporites haardtii Trudopollis meekeriLaevigatosporites spp. Laevigatosporites sp. Trudopollis sp.Larger fern tetrad Tschudypollis many, large Tschudypollis (reworked)Lecaniella Tschudypollis retususLeptolepidites major Tschudypollis sp.Liliacidites Tschudypollis thalmannii Tschudypollis thalmannii (reworked)Liliacidites complexus Tsugaepollenites sp.Liliacidites hyalaciniatus Ulmipollenites Ulmipollenites spp.Liliacidites leei Liliacidites leei Ulmipollenites krempii Ulmipollenites krempiiLiliacidites reticulata Ulmipollenites 3, 4 pored Ulmipollenites 3 and 4 pored.Liliacidites sp. Liliacidites sp. Ulmoideipites spp.3 and 4 pored smooth to verrucate formsLiliacidites sp. cf L. complexus Ulmoideipites tricostatus Ulmoideipites tricostatusLiquidambarpollenites sp. Unclassified bisaccatesLoranthacites Unclassified triletesLycopodiacidites kuepperi Unclassified triporatesLycopodiacidites spp. unidentified acritarchsLycopodiumsporites spp. unidentified dinoflagellate cystsMicrofoveolatosporis unidentified pollen tetradMicrofoveolatosporis canaliculatus unidentified trilete sporesMicroreticulatisporites sp. cf. Vitis affluens Vitis ? affluens

Zonalapollenitescf. Minorpollis Zlivisporis novomexicanum Zlivisporis novomexicanumMomipites inaequalis Momipites inaequalis Zlivisporis Zlivisporis sp.p q p q p p pNotes: Cretaceous strata include Kirtland, Fruitland, and Kirtland-Fruitland Formations undivided; Paleocene strata include the Ojo Alamo Sandstone and in places the Paleocene uppermost part of theKirtalnd and (or) Fruitland Formation. Palynomorphs listed are from Tables 23 and 24.


141 141

T

AB

LE

26

. P

AL

YN

OM

OR

PH

LIS

TS

FR

OM

TH

E N

AC

IMIE

NT

O A

ND

AN

IMA

S F

OR

MA

TIO

NS

, SA

N J

UA

N B

AS

INA

nde

rso

n 1

96

0 -

Na

cim

ien

to 1

flo

rule

Tsc

hu

dy 1

97

3 -

Ga

sbu

gg

y co

reW

NW

20

08

- K

imb

eto

Arr

oyo

An

ders

on

19

60

- N

aci

mie

nto

2 fl

oru

leT

sch

udy

(in

F&

H 1

97

1),

Lo

calit

y D

38

03

(M

DC

)N

ewm

an

19

87

- D

ura

ng

o,

CO

Nic

ho

ls W

C 1

99

4 -

Lo

calit

y D

68

78

(M

DC

)W

NW

20

08

- K

imb

eto

Arr

oyo

Tsc

hu

dy W

C 1

97

5 -

Lo

calit

y D

540

8 (

CO

)0

.3 m

AB

N2

sa

mp

les,

5 &

10

m A

BN

19

m A

BN

20

m A

BN

20

m A

BN

30

m A

BA

45

m A

BN

10

5 m

AB

N1

50 m

AB

AA

cer

stri

ata

An

gu

lolu

min

osu

sA

reci

pite

s re

ticu

latu

sA

reci

pite

s re

ticu

latu

s

Bo

mb

aca

cip

ites

na

cim

ien

toen

sis

Bo

mb

aca

cip

ites

na

cim

ien

toen

sis

Cu

pu

lifer

oid

aep

olle

nite

s m

inu

tus

Fra

xin

oip

olle

nite

s va

ria

bili

sG

leic

hen

iidite

s se

no

nic

us

Hys

tric

ho

sph

aer

ids

& d

ino

flag

ella

tes

Lili

aci

dite

s co

mp

lexu

sL

ilia

cidi

tes

leei

Lili

aci

dite

s le

eiL

yco

po

diu

m n

ovo

mex

ica

nu

m

Mo

mip

ites

ina

equ

alis

Mo

mip

ites

san

jua

nen

sis

Mo

mip

ites

cory

loid

esM

om

ipite

s te

nu

ipo

lus

Mo

mip

ites

ten

uip

olu

sM

om

ipite

s te

nu

ipo

lus

Mo

mip

ites

ten

uip

olu

sM

om

ipite

s te

nu

ipo

lisM

om

ipite

s te

nu

ipo

lus

Mo

mip

ites

ten

uip

olu

sM

om

ipite

s tr

iorb

icu

lari

s

Nys

sa p

uer

coen

sis

Nys

sa p

uer

coen

sis

Pa

nda

niid

ites

radi

cus

Po

doca

rpu

s se

llow

iform

is

Qu

ercu

s ex

pla

na

ta

Tili

a d

an

ei

Tri

atr

olo

po

po

llen

ites

trin

aT

rico

lpite

s a

ng

ulo

lum

ino

sus

Tri

colp

ites

an

gu

lolu

min

osu

sT

rico

lpite

s a

ng

ulo

lum

ino

sus

Tri

colp

ites

Tri

colp

ori

tes

rho

mb

oid

esT

rico

lpo

rite

s rh

om

bo

ides

Tri

po

rop

olle

nite

s p

lekt

osu

sT

rip

oro

po

llen

ites

rug

atu

s

`T

rip

oro

po

llen

ites

tect

us

Ulm

ipo

llen

ites

krem

pii

Ulm

ipo

llen

ites

krem

pii

Ulm

ipo

llen

ites

krem

pii

Ulm

ipo

llen

ites

tric

ost

atu

sU

lmip

olle

nite

s

Ulm

oid

eip

ites

tric

ost

atu

sU

lmo

idei

pite

s tr

ico

sta

tus

Un

cla

ssifi

ed b

isa

cca

tes

Aln

us 3

por

ed

Arec

ipite

s sp

.

Are

cipi

tes

sp.

Bire

tispo

rites

sp.

Cic

atric

osi

spo

rite

s sp

.C

lass

op

ollis

sp

.C

oro

llina

sp.

Co

rolli

na s

p. [c

omm

on]

Cup

anie

idite

s af

f. C

. maj

or

Eng

elha

rdtia

type

cf E

phe

dra

vol

uta

Equ

iset

osp

ori

tes

spp.

Lae

vig

atos

por

ites

sp.

Lae

vig

atos

po

rites

sp.

Lae

vig

atos

por

ites

sp.

Lyg

odi

ospo

rites

? sp

.M

omip

ites

sp. (

Mo

mip

ites

inae

qual

is A

nd.)

Mom

ipite

s tr

iorb

icul

aris

[com

mon

]M

ono

sulc

ites

sp. (

Rec

tosu

lcite

s la

tus

And

.)N

yssa

polle

nite

s sp

p.N

yssa

polle

nite

s sp

.

Osm

unda

cidi

tes

sp.

Per

ipor

opo

lleni

tes

sp.

"Pin

us h

aplo

xylo

n ty

pe"

Rud

olph

, 193

5"P

inus

hap

loxy

lon

typ

e" R

udo

lph,

193

5"P

inus

syl

vest

ris

type

" R

udo

lph,

193

5

Pol

ypod

iidite

s sp

p.P

olyp

orop

olle

nite

s sp

p.P

ityos

porit

es s

p.P

ityos

porit

es s

p.P

ityos

porit

es s

pp.

Psi

last

epha

noco

lpite

s sp

.

Rug

ulat

isp

orite

s sp

.S

alix

ipol

leni

tes

sp.

Sal

ix s

p.S

ynco

opo

rites

sp.

Tax

odia

ceae

pol

leni

tes

sp.

Tet

radi

tes

sp.

Tria

trol

opop

olle

nite

s sp

.

Tric

olp

ites

ang

ulol

umin

osu

s.T

rico

lpite

s sp

p.T

rico

lpite

s sp

p.T

rico

lpo

polle

nite

s sp

. (Q

uerc

us e

xpla

nata

And

.)T

rico

lpo

rites

sp.

(T

rico

lpo

rites

ang

ulo

lum

ino

sus

And

.)T

rico

lpo

rites

sp.

(?E

leag

nace

ae)

Tric

olp

orit

es s

p. (

Tri

colp

orit

es r

hom

boi

des

And

.)T

rico

lpo

rites

sp.

Trip

orop

olle

nite

s sp

. (c

f. C

asua

rini

dite

s)

Ulm

ipo

lleni

tes

spp

.U

lmo

idei

pite

s sp

.

Not

es:

AB

N =

abo

ve b

ase

of N

acim

ient

o F

orm

atio

n; A

BA

= a

bove

ba

se o

f A

nim

as F

orm

atio

n; W

C =

writ

tin c

om

mun

ica

tion;

WN

W =

Will

iam

son,

Nic

hols

, an

d W

eil;

F&

H =

Fa

sset

t an

d H

inds

; MD

C =

Mes

a d

e C

uba

; pa

lyno

mo

rphs

list

ed a

re fr

om T

abl

es 5

-9 a

nd T

able

15;

Lyc

opo

dium

nov

om

exic

anum

(N

aci

mie

nto

2 fl

orul

e)

is n

ow

Zliv

isp

oris

no

vom

exic

anum

(N

icho

ls 2

005,

WC

).


142 142

TAB

LE 2

7. P

ALY

NO

MO

RPH

S ID

ENTI

FIED

FR

OM

TH

E O

JO A

LAM

O S

AN

DST

ON

E A

ND

NA

CIM

IEN

TO F

OR

MA

TIO

NO

jo A

lam

o S

ands

tone

P P

alyn

omor

phs

Nac

imie

nto

Form

atio

n P

alyn

omor

phs

Ojo

Ala

mo

San

dsto

ne P

Pal

ynom

orph

s (C

ont.)

Nac

imie

nto

Form

atio

n P

alyn

omor

phs

(Con

t.)A

biet

inea

epol

leni

tes

sp. (

Pod

ocar

pus

north

rupi

)“P

aliu

rus”

trip

licat

usA

biet

inea

epol

leni

tes

sp.

(Pod

ocar

pus

sello

wifo

rmis

)P

anda

niid

ites

Ace

r stri

ata

Ace

r stri

ata

Pan

dani

idite

s ra

dicu

sP

anda

niid

ites

radi

cus

Alg

al c

ysts

Pan

dani

idite

s ty

picu

sA

lispo

rites

bila

tera

lis

Per

ipor

opol

leni

tes

sp.

Per

ipor

opol

leni

tes

sp.

Aln

us 3

por

ed"P

inus

hap

loxy

lon

type

" Rud

olph

, 193

5A

ngul

olum

inos

us"P

inus

syl

vest

ris t

ype"

Rud

olph

. 193

5A

quila

polle

nite

s sp

p.P

ityos

porit

es s

p.A

rauc

aria

cite

s au

stra

lisP

odoc

arpu

s se

llow

iform

isP

odoc

arpu

s se

llow

iform

isA

reci

pite

s re

ticul

atus

Are

cipi

tes

retic

ulat

usP

odoc

arpu

s sp

.A

reci

pite

s sp

.Ar

ecip

ites

sp.

P

olyp

odiid

ites

spp.

Pol

ypod

iidite

s s

pp.

Azo

lla c

reta

cea

Pol

ypod

iispo

roni

tes

sp.

Azo

lla c

f. A

. sch

opfi

Pol

ypor

opol

leni

tes

spp.

Bire

tispo

rites

sp.

Bire

tispo

rites

sp.

Pity

ospo

rites

spp

.B

omba

caci

pite

s na

cim

ient

oens

is

Bom

baca

cipi

tes

naci

mie

ntoe

nsis

Psi

last

epha

noco

lpite

s sp

.P

sila

step

hano

colp

ites

sp.

Bre

vico

lpor

ites

colp

ella

Qua

drap

olle

nite

s sp

.C

erci

diph

yllit

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alae

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etes

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ivis

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sp.

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es:

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Ala

mo

P" =

"Ojo

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mo

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dsto

ne P

lus"

- in

clud

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ampl

es fr

om th

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nder

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aleo

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age

.


143 143

TABLE 28. PALYNOLOGIC ZONATION OF UPPER CAMPANIAN STRATA, SOUTHERN S. J. BASINLower Fruitland Upper Fruitland Upper Kirtland

Corollina Corollina Equisetosporites parallel striae EquisetosporitesEucommiidites sp. Eucommiidites sp.Liliacidites leei Liliacidites leeiTaxodiaceaepollenites Taxodiaceaepollenites TaxodiaceaepollenitesTschudypollis many, large Tschudypollis spp. TschudypollisTschudypollis retusus Tschudypollis retusus Tschudypollis retususTschudypollis thalmannii Tschudypollis thalmannii

Abietineaepollenites AbietineaepollenitesAequitriraditesAraucariacites sp.Arecipites reticulatusAzolla BalmeisporitesCupaneidites sp.

Cyathidites spp. Cyathidites sp.Cycadopites fragillisCycadopites sp.Dyadonapites reticulatusErdtmannipollis sp.ForaminisporisGhoshispora sp.Granabivesiculites sp.GunneraInterpollisKurtzipitesKurtzipites trispissatus

Laevigatosporites spp. Laevigatosporites sp.Liliacidites hyalaciniatus

Liliacidites sp. LiliaciditesLiquidambarpollenites sp.

Lycopodiacidites LycopodiaciditesLycopodiumsporitesMonoporopollenites sp.MonosulcitesNyssapollenites albertensisOsmundaciditesPandaniidites typicus

Periporopollenites PeriporopollenitesPityosporites constrictusPityosporites spp.PterospermopsisQuercus explanataSchizosporis parvus

Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatusTricolpites interangulusTricolpites microreticulatusTricolpites reticulatusTricolpopollenites sp.Tsugaepollenites sp.

Ulmipollenites UlmipollenitesUlmipollenites krempiiUlmoideipites spp.Ulmoideipites tricostatusunidentified trilete sporescf Vitis affluensZlivisporis sp.


144 144

Camarozonosporites ambigens Camarozonosporites ambigensCicatricosisporites sp. Cicatricosisporites sp.

Corollina torosaCupuliferoidaepollenites spp. Cupuliferoidaepollenites spp.Dinoflagellates very few DinoflagellateEchinatisporis varispinosus Echinatisporis varispinosus

Eucommiidites minorGleicheniidites Gleicheniidites

KlukisporitesMicrofoveolatosporisMicroreticulatisporites sp.Momipites sanjuanensis

Nyssapollenites sp. Nyssapollenites spp.Pseudoplicapollis newmanii

Pseudoplicapollis? PseudoplicapollisReticuloidosporites pseudomurii Reticuloidosporites pseudomurii

Rhoipites sp.Rugubivesiculites RugubivesiculitesStereisporites spp. Stereisporites spp.Tricolpites spp. Tricolpites spp.

Triporopollenites tectusAcanthotriletesAccuratipollisAequitriraditesAlgal cystsAppendicisporites sp.Araucariacites commonAquilapollenites quadrilobusAquilapollenites senonicusAquilapollenites trialatus, var. uniformisArecipitesBalmeisporitesBisacaccate conifer pollenBotryococcusCyathidites minorEphedra sp.Foveosporites sp.Hystrichospheres very fewIlexpollenitesInaperturopollenitesLecaniellaMonocolopopollenites? s p.Monosulcites sp. Neoraistrickia sp.PediastrumPlicapollis?PristinuspollenitesQuadripollis krempiiTetracolpitesTilia wodehouseiTricolpopollenites sp.Tricolporites sp.Triporopollenites spp.TrudopollisUlmipollenites krempiiUlmoideipites tricostatusZonalapollenites sp.Note. Palynomorph lists from Tables 21, 22, 23.


145 145

TABLE 29. COMPARISON OF PALYNOMORPHS FROM CRETACEOUS (CAMPANIAN) AND PALEOCENE STRATA IN SAN JUAN BASIN, NEW MEXICO AND COLORADOPaleocene - Ojo Alamo Sandstone Plus Cretaceous - Fruitland and Kirtland Formations Cretaceous - Fruitland and Kirtland Formations (Cont.)

Abietineaepollenites sp. (Podocarpus northrupi ) BotryococcusAbietineaepollenites sp. (Podocarpus sellowiformis ) Camarozonosporites ambigens RB

Acer striata Camarozonosporites sppRB.Alisporites bilateralis Cingulatisporites lanceiAraucariacites australis ClavatipollenitesAzolla cf. A. schopfi cf. Concavisporites verrucosusBiretisporites sp. Confertisulcites knowltoni Bombacacipites nacimientoensis CorollinaBrevicolporites colpella NGP Cupuliferoidaepollenites minorCercidiphyllites sp. Cupuliferoidaepollenites spp.Classopollis sp. Cyathidites spp.Cupanieidites aff. C. major Cycadopites sp.Cupanieidites sp. DinoflagellatesCyrilla minima Echinatisporis varispinosusDeltoidospora spp. Ephedra multicostataEquisetosporites lajwantis Ephedripites sp.Ericaceoipollenites sp. Equisetosporites parallel striaeGleicheniidites senonicus Equisetosporites spiralLaevigatosporites haardtii Erdtmanipollis cretaceusMomipites tenuipolus RB&NGP Erdtmannipollis sp.Nyssapollenites explanatus Eucommiidites minorNyssa puercoensis Eucommiidites sp.Osmundacidites wellmannii Extratriporopollenites sp.Ovoidites ligneolus Fern spores not abundantOvoidites sp. Foraminisporis undulatus“Palaeoisoetes ” sp. Foveotriletes scrobicularisPandaniidites Foveosporites sp. Cf. F. canalisPandaniidites radicus Gleicheniidites spp.Podocarpus sellowiformis Granabivesiculites sp.Podocarpus sp. Gunnera microreticulata RB

Polypodiisporonites sp. Ilexpollenites compactus RB

Psilastephanocolpites sp. Interporopollenites Quadrapollenites sp. Inaperturopollenites cf. I. hiatusQuercus sp. Inaperturotetradites scabratusRectosulcites latus KlukisporitesSalix sp. Kurtzipites RB

Syncolporites minimus Kurtzipites trispissatus RB

Taxodiaceaepollenites vacuipites Kuylisporites sp.Tricolpites foveolate Larger fern tetradTricolpites scabrate LecaniellaTricolpites vulgaris Leptolepidites majorTricolporites rhomboides LiliaciditesTricolporites sp. Liliacidites complexus NGP

Triporoletes simplex Liliacidites hyalaciniatus Triporopollenites plektosus Liliacidites reticulatacf. Triporopollenites rugatus Liliacidites sp. cf L. complexusUnclassified bisaccates Liquidambarpollenites sp.Unclassified triletes LoranthacitesUnclassified triporates Lycopodiacidites kuepperiAlgal cysts Algal cysts Lycopodiacidites spp.Aquilapollenites spp. Aquilapollenites sp.RB Lycopodiumsporites spp.Arecipites reticulatus Arecipites reticulatus MicrofoveolatosporisArecipites sp. Arecipites Microfoveolatosporis canaliculatusAzolla cretacea Azolla cretacea Microreticulatisporites sp.Chenopodipollis sp. Chenopodipollis sp. cf. MinorpollisCicatricosisporites spp. Cicatricosisporites sp. Monocolopopollenites ? sp.Corollina torosa (incl. monads and tetrads) Corollina torosa Monoporopollenites sp.Cupanieidites cf. C. reticularis Cupanieidites aff. C. reticularis Monosulcites perspinosusCupuliferoidaepollenites minutus Cupuliferoidaepollenites minutus Monosulcites sp.Cyathidites minor Cyathidites minor Navisulcites marginatus Cycadopites fragilis Cycadopites fragillis Neoraistrickia sp.Dyadonapites reticulatus Dyadonapites reticulatus Nyssapollenites albertensisEchinatisporis sp. Echinatisporis OsmundaciditesEngelhardtia type Engelhardia type Osmundacidites stanleyicf. Ephedra voluta Ephedra sp. cf. E. voluta Palaeoisoetes subengelmanniiEquisetosporites spp. Equisetosporites sp. PediastrumForaminisporis spp. Foraminisporis sp. Periporopollenites sp.Fraxinoipollenites variabilis Fraxinoipollenites variabilis Perotriletes cubensis Ghoshispora sp. Ghoshispora spp. Phaseoliidites stanleyiHystrichosphaerids & dinoflagellates Hystrichospheres Pityosporites constrictusLaevigatosporites sp. Laevigatosporites spp. Pityosporites typicusLiliacidites leei Liliacidites leei Plicapollis ?Liliacidites sp. Liliacidites sp. Pollenites ? sp.Momipites inaequalis Momipites inaequalis Polypodiisporites amplusMomipites sanjuanensis Momipites sanjuanensis Polypodiisporites sp.Momipites sp. Momipites sp. PristinuspollenitesNyssapollenites sp. Nyssapollenites sp. Pseudoplicapollis ?“Paliurus” triplicatus Paliurus triplicatus Pseudoplicapollis newmaniiPandaniidites typicus Pandaniidites typicus PseudoschizaeaPeriporopollenites sp. Periporopollenites sp. Pseudoplicapollis sp.Pityosporites sp. Pityosporites spp. PterospermopsisPolypodiidites spp. Polypodiidites spp. Quadripollis krempii“Quercus” explanata Quercus explanata cf. Radialetes costatusSchizosporis parvus Schizosporis parvus Reticuloidosporites pseudomuriiStereisporites spp. Stereisporites spp. Retitriletes sp. ("Lycopodiumsporites")Taxodiaceaepollenites hiatus Taxodiaceaepollenites hiatus Rhoipites sp.Taxodiaceaepollenites sp. Taxodiaceaepollenites RugubivesiculitesTetracolpites 2 sp. Tetracolpites Sphagnum sp.Tricolpites anguloluminosus Tricolpites anguloluminosus Sporites? sp.Tricolpites spp. Tricolpites spp.RB Subtriporopollenites sp.Triporoletes novomexicanum Triporoletes novomexicanum cf. TaurocusporitesTriporopollenites sp. Triporopollenites spp. Tilaepopollenites sp. (Tilia wodehousei )Triporopollenites tectus Triporopollenites tectus cf. Tilia wodehousei RB

Ulmipollenites Ulmipollenites Toroisporis sp.Ulmipollenites krempii Ulmipollenites krempii Trichopeltinites RB

Ulmipollenites 3 and 4 pored. Ulmipollenites 3, 4 pored Tricolpites hiansUlmoideipites tricostatus Ulmoideipites tricostatus Tricolpites interangulus NewmanVitis ? affluens cf. Vitis affluens Tricolpites microreticulatus NGP

Zlivisporis novomexicanum Zlivisporis novomexicanum Tricolpites reticulatus RB

Zlivisporis sp. Zlivisporis Tricolpites sp. AAbietineaepollenites Tricolpopollenites sp.Acanthotriletes Tricolpopollenites sp. (Quercus explanata )Accuratipollis RB Tricolporites sp.Aequitriradites Tricolporites traverseiAequitriradites spinulosus Triletes? sp. Alnipollenites 4 pored Triplanosporites sp.Alnus 3 pored Triporopollenites rugatus RB

Alsophilidites sp. Trudopollis meekeriAppendicisporites spp. Trudopollis sp.Aquilapollenites attenuatus NGP Tschudypollis many, largeNGP

Aquilapollenites delicatus NGP Tschudypollis retusus RB&NGP

Aquilapollenites quadrilobus NGP Tschudypollis sp.NGP

Aquilapollenites senonicus NGP Tschudypollis thalmannii RB&NGP

Aquilapollenites trialatus, var. uniformis Tsugaepollenites sp.Aquilapollenites turbidus NGP Ulmipollenites RB

Araucariacites sp. Ulmoideipites spp.3 and 4 pored smooth to verrucate formsArecipites columellus unidentified acritarchsArecipites microreticulatus unidentified dinoflagellate cystsAzolla circinata unidentified pollen tetradAzolla microspores unidentified trilete sporesBalmeisporites ZonalapollenitesBisacaccate conifer pollen

Note: Blue = palynomorphs that occur only in the Paleocene througout Western Interior, magenta = palynomorphs extinct at end of Cretaceous: in Raton Basin (superscript RB) per Fleming (1990); in Northern Great Plains (superscript NGP) per Nichols and Johnson (2002); Paleocene Ojo Alamo Sandstone Plus includes Ojo Alamo Sandstone plus uppermostPaleocene part of underlying strata at some localities.


146 146

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