GUIDEBOOK 24

TertiaryAnd Quaternary Stratigraphy

And Vertebrate Paleontology

Of Parts Of Northwestern TexasAnd Eastern New Mexico

T. C. Gustavson, Editor

Contributors

T. C. Gustavson,V. T. Holliday, W. R. Osterkamp,G. E. Schultz, and D. A. Winkler

Bureau of Economic Geology " W. L. Fisher, DirectorThe University ofTexas at Austin " Austin, Texas 78713

Cover:

Illustrations, symbolic of the range of research described in thisvolume, are (clockwise from top left): paleontology representedby the fossil mammal Synthetoceras tricornatus\ depositionalprocesses and eolian stratigraphy represented by a dust storm;stratigraphy, hydrology, and geomorphology represented byplayas incised into the High Plains; and hydrology represented bya windmill on the High Plains. Line drawings by JamieH. Coggin.

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Contents

Introductionby T. C. Gustavson, V. T. Holliday, and G. E. Schultz 1Regional geologic setting 1

Structural development 1Stratigraphy 1Hydrogeology 4Geomorphology and physiography 4

Climate 5Middle Tertiary erosional surface 6Ogallala Formation 6Blanco Formation 10Blackwater Draw Formation 11Tule Formation 13The Clarendon Fauna and the Clarendonian Land Mammal Age 13

Establishment of "Provincial" and "Land Mammal" Ages 13Introduction, historical background, and type locality 14Age and correlation 17

The Hemphillian Land Mammal Age, Texas Panhandleand adjacent Oklahoma 17

Introduction 17Age and correlation 17Faunal turnover in the Hemphillian 17

Blanco Formation 18History of investigations and interpretations 18

STOP 1: Blackwater Draw Formation type localitybyV. T. Holliday 22

STOP 2A: Gentry playa: origin by hydrologic processesby W. R. Osterkamp 32

STOP 2B: Gentry playa: origin by geomorphic processesbyV. T. Holliday 36

STOP 3: Ogallala Formation (Group) exposed at Janes Quarryby D. A. Winkler 38

STOP 4: Type section of the Couch andBridwell Formations (Ogallala Group)at Blanco Canyon, Silver Falls areaby D. A. Winkler 41

STOP 5: Blanco Local Fauna and the Blancan LandMammal Ageby G. E. Schultz 44

IV

STOP 6: Age of the lower Blackwater Draw Formationat Blanco CanyonbyV. T. Holliday 52

STOP 7: Age of the Blackwater Draw Formation exposedat Tule Creek, Texas PanhandlebyV. T. Holliday 56

STOP 8: Biostratigraphy and volcanic ash deposits of theTule Formation, Briscoe County, TexasbyG. E. Schultz 60

STOP 9: Upper Tertiary Ogallala Formation eolian strataat the Caprock Escarpment, east of Silverton, TexasbyT. C. Gustavson 65

STOP 10: Upper Tertiary Ogallala Formation strata at theCaprock Escarpment, Palo Duro CanyonState Park, TexasbyT. C. Gustavson 69

STOP 11: Upper Tertiary Ogallala Formation at theCaprock Escarpment, Buffalo LakeNational Wildlife Refuge, Texas PanhandlebyT. C. Gustavson 72

STOP 12: Upper Tertiary Ogallala Formation at theCaprock Escarpment, north of Bellview, New MexicobyT. C. Gustavson 75

STOP 13: UpperTertiary Ogallala Formation at theCaprock Escarpment, Ragland, New MexicobyT. C. Gustavson 79

STOP 14: The Clarendonian faunas of the Texas andOklahoma PanhandlesbyG. E. Schultz 83

STOP 15: Early Hemphillian faunas of the Texas andOklahoma PanhandlesbyG. E. Schultz 95

STOP 16: Late Hemphillian faunas of the Texasand Oklahoma Panhandlesby G. E. Schultz 104

STOP 17: Latest Hemphillian faunas of the Texas Panhandleby G. E. Schultz 112

V

Acknowledgments 115References 115

Figures1. Location of field trip stops 22. Major structural elements, Texas Panhandle 33. Physiography ofparts of Southern and Central High Plains 54. Structure-contour, or paleotopographic, map on base of Ogallala Formation 75. Geologic map ofparts of eastern NewMexico and northwestern Texas 86. View ofnortheast rim of Palo Duro Canyon 107. Distribution of Blackwater Draw Formation 128. Map of Lubbock, Texas, area 239. Generalized soil-stratigraphic relationships exposed at Blackwater Draw

Formation type section 2810. View of type section of Blackwater Draw Formation 2911. Ladder structure where CaCO3 nodules follow joints between peds 3012. Quarryface in central part of Gentrypit 3213. Photomicrograph ofBlackwater Draw Formation sample 3414. Map of Slaton, Texas, area 3815. Coarse-grained gravels of upper Tertiary OgallalaFormation 3916. Structure-contour map ofapproximate altitude ofbase of High Plains aquifer 4017. Map of Crosbyton, Texas, area 4118. Geologic map of type area of Couch and Bridwell Formations 4319. Map showing locations of Blanco Local Fauna sites, Crosby County, Texas 4420. Mount Blanco, view toward southeast 4521. Blanco Formation, Crosby County, Texas 4522. Blanco Formation showingBlanco volcanic ash, Crosby County, Texas 4523. View ofBlackwater Draw Formation overlying Blanco Formation 4924. Schematic drawing of upper Cenozoic strataexposed atBlanco Formation

type section and generalized stratigraphy 5225. Map of Silverton, Texas, area 5626. View of Quaternary Blackwater Draw and TuleFormations 5727. Schematic drawing showing soil-stratigraphic relationships of

Blackwater Draw and Tule Formations 5728. Geologic map ofparts of Cope Creekand Rock CreekQuadrangles 6129. Biostratigraphic section ofTule Formation 6230. View of upperTertiary OgallalaFormation east ofSilverton, Texas 6631. Composite profile of OgallalaFormation east of Silverton,Texas 6732. Symbols used in descriptive sections in figures 31, 34, 35, 38, and 40 6833. Map of Canyon, Texas, and vicinity 6934. Composite profile of OgallalaFormation at CaprockEscarpment,

Palo Duro Canyon State Park 7035. Composite profile of OgallalaFormation, Buffalo Lake National Wildlife Refuge 7336. View to north across valley ofTierra Blanca Creek, Buffalo Lake

National Wildlife Refuge 7437. Map ofparts of Quay and Curry Counties, NewMexico, and Deaf Smith County, Texas 7538. Composite profile of OgallalaFormation at CaprockEscarpment

north of Bellview, New Mexico 7639. Map ofTucumcari, New Mexico, area 7940. Composite profile of OgallalaFormation at Caprock Escarpment,

Ragland, NewMexico 8041. Location of Clarendonian, Hemphillian, Blancan, and post-Blancan faunas,

Texas and Oklahoma Panhandles 8442. Location ofClarendonian fauna! sites in Donley County, Texas 85

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43. Rowe-Lewis Ranch Quarry 4, view 1 8644. Rowe-Lewis Ranch Quarry 4, view 2 8645. Gidley's 3-Toed Horse Quarry, Donley County, Texas 8746. Location of late Clarendonian and early Hemphillian faunal sites,

Lipscomb County, Texas, and Ellis County, Oklahoma 9447. Early Hemphillian Frick Laboratory Port-of-EntryPit (=ArnettLocal Fauna) 9648. OgallalaFormationmortar beds outcrop west ofSebits Ranch 10049. Sebits Ranch near Higgins, Texas, in 1937, view to west 10150. Sebits Ranch in 1937, view to east 10151. Box TLocal Fauna Pit No. 1, Lipscomb County, Texas 10352. Topographic map of Coffee Ranch Quarry, Hemphill County, Texas 10453. Coffee Ranch Quarry, Hemphill County, Texas, in 1936 106

Tables1. Correlation chart of Clarendonian and Hemphillian faunas of the Great Plains 162. Soil descriptions, Blackwater Draw type section 243. Soil description, B. F. Gentry Pit 374. Faunal list of Blanco Local Fauna, Crosby County, Texas 465. Soil descriptions, Blanco Formation type section nearMount Blanco 546. Soil descriptions, Tule Basin type section 587. Composite faunal list—Clarendon Fauna, Donley County, Texas 888. Faunal lists of early Hemphillian chronofaunal sequence of local faunas in the Texas

Panhandle and adjacent Oklahoma 979. Faunal lists of late Hemphillian local faunas of the Texas and Oklahoma Panhandles 107

10. Faunal lists of latest Hemphillian local faunas of the Texas Panhandle ; 114

1

IntroductionT. C. Gustavson, V. T. Holliday, and G. E. Schultz

This field guide summarizes recent inter-pretations of the upper Cenozoic stratigraphy ofparts of the Southern High Plains and RollingPlains in northwestern Texas and eastern NewMexico. Processes that formed lacustrinebasins,which pond surface water on the High Plainsthat is recharged to the Ogallala aquifer, arealso described. Field trip stops were selected toillustrate the depositional facies and paleosolsof Cenozoic formations, Cenozoic local faunas,and lacustrine basins. Eolian facies (loess andsheet sands) and calcic paleosols that char-acterize the Quaternary Blackwater DrawFormation and the upper part of the NeogeneOgallala Formation (Group) are emphasized(Stops 1, 2, 4, 6, 7, 9, 11, 12, and 13) (fig. 1).Fluvial facies in the Ogallala Formation aredescribed from exposures at both the east andnorthwest erosional limits of the unit (Stops 3,6, 10, 12, and 13). Sections in the Ogallala,Blanco, and Quaternary Tule Formations con-taining local vertebrate faunas of Clarendonianage (Stops 6 and 14), Hemphillian age (Stops 3,6, 15, 16, and 17), Blancan age (Stop 5) andIrvingtonian age (Stop 8) are described (locationsof Stops 14-17 are given on separate maps).Evidence of the geomorphic processes of sub-sidence induced by piping and subsidencerelated to dissolution of CaCO3

, which led tothe development of lake basins on the HighPlains, is discussed at Stop 2.

Keywords: Blackwater Draw, field tripguidebooks, High Plains, New Mexico,Ogallala, paleosols, playas, Quaternary,stratigraphy, Tertiary, Texas, vertebratepaleontology

Regional Geologic SettingStructuralDevelopment

The Palo Duro Basin, which underlies part ofthe Texas Panhandle and eastern New Mexicois bounded by the Amarillo Uplift-WichitaMountains trend on the northeast and by theMatador Arch-Roosevelt Uplift on the south

(fig. 2). To the west the Palo Duro and TucumcariBasins are bounded by the Pedernal and SierraGrande Uplifts. To the north the Dalhart andAnadarko Basins are separated by the CimarronArch. These positive structural elementsresultedfrom faulting and uplift that began during thePaleozoic, perhaps as early as theLate Cambrian(Birsa, 1977).

During the Pennsylvanian and Early Permian,tectonic movement along theAmarillo Uplift andMatador Arch controlled sedimentation andfacies distribution in the Palo Duro Basin(Dutton and others, 1979). Epeirogenic upliftduring the Triassic resulted in the terrestrialbasin that contains the Dockum Group(McGowen and others, 1979). By Cretaceoustime the region had subsided below sea level.Epeirogenic movements continued into theTertiary and resulted in uplift of Cretaceousmarine strata to more than 940 m (3,100 ft)above sea level in the study area (Eifler, 1968;Gable and Hatton, 1983; Budnik, 1984).

Nontectonic deformation, in the form ofregional subsidence induced by extensive dis-solution of Permian bedded salt, has occurredbeneath large parts of the Southern High Plainsand surrounding areas (Gustavson and others,1980, 1982; Johnson, 1981; Gustavson andBudnik, 1985; Gustavson and Finley, 1985;DeConto and Murphy, 1986; Gustavson, 1986a,b; Reeves and Temple, 1986; Boyd and Murphy,1987; McGookey and others, 1988). Several ofthe lacustrine basins on the High Plains mayhave formed partly from dissolution-inducedsubsidence during the late Tertiary or Quater-nary (Baker, 1915; Gustavson and Budnik,1985; Gustavson and Finley, 1985; Reeves andTemple, 1986). Other arguments suggest thatdissolution beneath the High Plains occurredduring the Triassic and could not have affectedTertiary or Quaternary lacustrine basins(DeConto and Murphy, 1986).

Stratigraphy

During the early Paleozoic, episodes of depo-sition on shallow marine shelves alternatedwith periods of erosion in the vicinity of the

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Figure 1.Location of FieldTrip Stops 1 through 17 inTexas and eastern New Mexico.

Texas Panhandle and eastern New Mexico.Terrigenous elastics, informally called granitewash, were derived from, and deposited as fandeltas near, the Matador Arch and AmarilloUplift during the Pennsylvanian and EarlyPermian as a result of uplift of these features(Handford and Dutton, 1980). Marine sed-imentation during the Late Pennsylvanian and

Early Permian was dominated by shelf-margincarbonates while the deeper parts of the basinwere being filled by fine-grained terrigenousclastic sediments. During the middle and LatePermian a wide, low-relief marine shelfdeveloped, and salt, anhydrite, dolomite,limestone, and red beds were deposited (Presley,1979a, b, 1980a, b; McGillis and Presley, 1981;

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Figure 2. Major structural elements, Texas Panhandle and surrounding areas. After Nicholson (1960).Limits of Permian bedded salts are closely associated with structural margins of Palo Duro Basin; linesillustrate updip limit of Permian bedded salt. Each of these units (Salado-GlorietaFormations) has lostsubstantialthicknesses of salt. Collectively, the salt-limit lines approximatea zone of salt dissolution thatrims west, north, and east margins of Palo Duro Basin. Structurally high salt units are most likely to beaffected by salt dissolution(Gustavson andFinley, 1985).

Hovorka and others, 1985; Fracasso andHovorka, 1986).

Fluvial, deltaic, and lacustrine sandstones andmudstones of the Triassic Dockum Group un-conformably overlie Permian strata (McGowenand others, 1979). Locally in easternNewMexicoJurassic marine strata unconformably overliethe Dockum Group. In the Texas Panhandleand parts of eastern New Mexico, Lower Creta-ceous Edwards Limestone also unconformably

overlies the Dockum Group. During the LateCretaceous and early Tertiary, extensiveerosionexposed Triassic, Jurassic, and Lower Creta-ceous strata. Fluvial and eolian sediments ofthe Neogene Ogallala Formation overlie theTertiary erosional surface (Seni, 1980; Winkler,1984, 1985, 1987; Gustavson and Holliday,1985; Gustavson and Winkler, 1988; Wilson,1988). Locally, upper Pliocene lacustrinedeposits of the Blanco Formation and Cita

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Canyon lake beds overlie the OgallalaFormation(Holliday, 1988). The Quaternary BlackwaterDraw Formation, which is composed primarilyof eolian sediments, overlies the Ogallala For-mation as well as the Pliocene lacustrineformations (Holliday, 1984, 1988; Gustavsonand Holliday, 1985; Machenberg and others,1985). Lacustrine sediments of the Tule For-mation are interbedded with sediments of theBlackwater Draw Formation (Gustavson andHolliday, 1985; Schultz, 1986). Thick, wide-spread Quaternary eolian, fluvial,and lacustrinedeposits, containing sediments eroded fromthe Caprock Escarpment, overlie Triassic andPermian strata on the Rolling Plains at the footof the Caprock Escarpment (Caran andBaumgardner, 1990).

HydrogeologyStudies of the hydrology of the Palo Duro

Basin indicate that the lower, or Wolfcampianbrine, aquifer is separated from aquifers in theoverlying OgallalaFormation and Dockum Groupby an aquitard containingUpperPermian evap-orites and salt-cemented terrigenous elastics.Regional flow of the Wolfcampian aquifer istoward the northeast (Smith and others, 1983).Ground-water movement through the evaporiteaquitard is minimal; flow is to the east andsoutheast (Dutton, 1983). Ground water in theunconfined Ogallala aquifer and in the Dockumaquifer also flows toward the east and south-east (Dutton and Simpkins, 1986; Nativ, 1988).Recharge of the Ogallala is primarily fromsurface water ponded in small playa-lakebasins on the High Plains (Osterkamp and Wood,1987; Wood and Osterkamp, 1987; Nativ, 1988).Numerous fresh-water springs, which mark dis-charge points of the Ogallala and Dockum aqui-fers, lie along the Caprock Escarpment at thebase of the Ogallala Formation and to a lesserextentat the base of sandstones in the DockumGroup (Brune, 1981). A preliminary model ofground-watermovement from west to east acrossthe eastern Caprock Escarpment suggests thatfresh water from the Ogallala Formation leaksdownward into the zone of salt dissolution inPermian strata (fig. 2) and eastward beneaththe Rolling Plains (Simpkins and Fogg, 1982).Springs discharge brines derived from dis-solution of halite in several areas east of theescarpment (U.S. Army Corps of Engineers,1975; Richter and Kreitler, 1986). Na-Cl groundwaters from the salt dissolution zone beneath

the Southern High Plains have 14C ages of lessthan 16,200±3,500 yr and 23,500+1,000 yr andsalinities of95,000 to 68,000 ppm (Dutton, 1987).

Geomorphology and PhysiographyField trip stops are located on the High Plains,

Canadian River Breaks, Rolling Plains, andeastern Caprock Escarpment, which separatesthe High Plains from the Rolling Plains (fig. 3).Regional physiography is largely controlled bysubsidenceresulting from dissolution of Permiansalt. For example, the Canadian and Pecos Rivervalleys overlie areas where as much as 200 m(660 ft) of Permian salt has been dissolved(fig. 2). These valleys were probably formed bydiversion of Tertiary drainage due to dissolutionand subsidence (Gustavson and Finley, 1985;Gustavson, 1986a).

The Southern High Plains, which is primarilyunderlain by the Blackwater Draw Formation,has a flat, low-relief surface partly covered withsmall playa-lake basins. Playa-lake basins aswell as some of the larger lake basins havebeen variously attributed to deflation, dissolutionof salt or soil carbonate, compaction, or animalactivity (Gilbert, 1894; Baker, 1915; Evans andMeade, 1945; Reeves, 1972; Gustavson andothers, 1980; Reeves and Temple, 1986;Osterkamp and Wood, 1987). Drainage of theHigh Plains is mostly internal into these lakebasins. Widely separated draws having narrowdrainagebasins slope to the east and southeast.Adjacent draws do not have common drainagedivides but are separated by broad interfluvescontainingnumerous playa-lake basins.

The relief of the Caprock Escarpment ismaintained by resistant calcretes and silicifiedzones of the Ogallala Formation and resistantsandstones of the Dockum Group and PermianQuartermaster Formation. The escarpment par-allels and overlies the west margin of the zoneof extensive dissolution of Permian bedded salt(Gustavson and others, 1981; Gustavson andFinley, 1985).

The Rolling Plains is developed primarily oneasily eroded Permian strata of the Quarter-master andWhitehorse Formations (Bath, 1980;Gustavson and others, 1981; Gustavson, 1986b;Simpkins and Gustavson, 1987), and is locallyhighly dissected by modern streams. In mostupland areas, however, topography is rolling;hence the name Rolling Plains. Drainage on theRolling Plains tends to parallel the margins ofsubsurface salt units undergoing dissolution,

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Figure 3. Physiography of parts of Southern and Central High Plains and surrounding area in Texas andNew Mexico.

and karst features resulting from dissolution-induced subsidence are common (Simpkinsand others, 1981; Gustavson and others, 1982;Gustavson and Finley, 1985).

ClimateClimate in the Texas Panhandle and eastern

NewMexico is continental semiarid to subhumid(30 to 55 cm [12 to 22 inches] annual precipi-tation), and mean annual precipitation varieswidely (Orton, 1964; U.S. Department of Com-

merce, 1978a, b). Approximately 75 percent ofthe annual precipitation occurs between the endof March and the beginning of October. Annualpan evaporation is approximately 158 cm (62inches) (Kler and others, 1977). Rapid temper-ature changes and large ranges in daily andannual temperature are characteristic of theregion (Orton, 1964). The calcic soils that aredeveloping in the Texas Panhandle and easternNew Mexico are caused partly by the climaticconditions of the area and partly by the influxof CaCO3 contained in eolian dust and rainfallsolutes (Jenny, 1941; Machette, 1985).

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Middle Tertiary ErosionalSurface

Permian, Triassic, and Cretaceous strataunderlie the middle Tertiary erosional surfacebeneath the High Plains. A structure-contourmap on the base of the OgallalaFormation (HighPlains aquifer) (fig. 4) can closely approximatethis surface because in most areas the base ofthe High Plains aquifer is thebase of the OgallalaFormation. However, small parts of the TriassicDockum Group are locally included in the HighPlains aquifer.

Paleotopographic elements are clearly dis-cernible in many areas, and aligned groups ofV-shaped contour lines that point upslopeindicate a system of major paleovalleys (fig. 4).These relationships are clear on the part of theerosional surface that underlies the SouthernHigh Plains; however, much of the area thatunderlies the Central High Plains, which liesnorth of the Canadian River Valley, has beenaffected by subsidence resulting from salt dis-solution, and pre-Ogallala erosional topographyis no longer identifiable (Gustavson and Finley,1985). In the Southern High Plains, paleostreamsegments appear to have flowed to the south-east over parts of the paleosurface. In northernHale, southern Swisher, and southern CastroCounties, a major paleovalley contained streamsthat flowed west to east. This paleovalley extendsnorthwestward into southeast Quay County,New Mexico. In southeast Deaf Smith and south-west Randall Counties, Texas, a paleostreamdivide lies 150 m (500 ft) above the paleostreamvalley innorth Hale County (fig. 4). Other dividesare in southeast Hale and central FloydCounties.

Ogallala Formation (Stops 3,4, and 9 through 17)

The Miocene-Pliocene Ogallala Formationcovers much of the Great Plains, extending morethan 1,200 km (800 mi) from South Dakota toTexas, including most of northwestern Texasand parts of eastern New Mexico (fig. 5). InTexasand eastern NewMexico, the Ogallalawasdeposited unconformably on Permian, Triassic,Jurassic, and Cretaceous strata. Thickness ofthe Ogallala reflects the paleotopography on theunderlying middle Tertiary erosional surface and

varies from less than 30 m (100 ft) to morethan 150 m (500 ft) beneath most of the South-ern High Plains. Locally, above subsidencebasins induced by salt dissolution (Gustavsonand others, 1980; Gustavson and Finley, 1985),thicknesses may exceed 235 m (800 ft). Typi-cally, however, areas of thick accumulations liein paleovalleys, and thin accumulations overliepaleotopographic divides.

The Ogallala Formation was first describedby Darton (1899) in Nebraska. Baker (1915)recognized that the upper Cenozoic deposits ofthe Texas Panhandle resulted from uplift anderosion of the Rocky Mountains to the west andthat these depositswere primarily fluvial and toa lesser extenteolian.

Most authors, including Johnson (1901),Sellards and others (1932), Smith (1940), Bretzand Horberg (1949a, b), Frye and Leonard(1964), Frye (1970), Sen! (1980), and Reeves(1984b), thought that the Ogallala FormationinTexas and New Mexico contained primarilyfluvial sediments and that the fluvial partoriginated either as a series of deposits fromephemeral streams or as a great alluvial plain(bajada). It was commonly accepted that an ero-sional surfacecontaining deep, wide valleys wasburied during the late Tertiary and that thepresent High Plains surface was a reflection ofthe depositional slope of the Ogallala. In general,the importanceof eolian sedimentation has notbeen recognized. However, Evans and Meade(1945), Reeves (1972), Hawley (1984), Gustavsonand Holliday (1985), Winkler (1987), andGustavson and Winkler (1988) described sub-stantial eolian sections in the Ogallala.

Some recent studies in the Texas Panhandleemphasize that the depositional environment ofthe Ogallala Formation was similar to that ofboth modern and ancient wetalluvial fans. Seni(1980) compared the Ogallala to the Kosi Riverfan in Nepal and India (Gole and Chitale, 1966).The distal portion of theKosi fan is fine grained,consisting mostly of sand and fine sand. Seni(1980) thought the texture of the Kosi fan andits large size (15,400 to 20,500 km2 [6,000 to8,000 mi2]) made it a suitable modern analogof the OgallalaFormation. Reeves (1984b) sug-gested several ancient analogs including thesandstone deltaic facies of the Van Horn For-mation, Texas (McGowen and Groat, 1971), theEast Rand fan of theWitwatersrand Basin, Africa(Pretorius, 1974), and the Salt Wash Member ofthe Morrison Formation (Mullens and Freeman,

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Figure 4. Structure-contour, or paleotopographic, map onbase of Ogallala Formation. Derived from Knowlesand others (1982) for Texas part and Cronin (1969) for New Mexicopart. Paleostreams are interpretedfromcontour Vs pointing upslope. Modern drainage superimposed to show similarity between modern andpaleodrainage.After Gustavsonand Finley (1985).

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Figure 5. Geologic map of parts of eastern New Mexico and northwestern Texas showing distribution ofupperTertiary OgallalaFormation (Group) and QuaternaryBlackwater Drawand lingosFormations. Mappingderived from Caran and others (1985), Eifler (1969, 1976), Eifler and others (1967, 1968, 1974, 1983,1984), Eifler and Fay (1970), and Eifler and Reeves (1974, 1976, 1977).

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1957), as well as an additional modern analog,the Riverine Plain, Australia (Schumm, 1968).

Gustavson and Holliday (1985), Winkler(1985), and Gustavson and Winkler (1988) sug-gested that fluvial facies of the Ogallala weresimilar to deposits of recent intermittent high-energy braided streams of variable water andsediment discharge (McKee and others, 1967)and that the fine-grained eolian part of theOgallalaresembled eolian sand sheets (Frybergerand others, 1979; Kocurek and Neilson, 1986).

Fluvial sections of the Ogallala, commonlyoverlain by eolian sections, lie along the axes ofbroad pre-Ogallala paleovalleys that trendsoutheastward across the middle Tertiary ero-sional surface. Upland sections, consisting pre-dominantly of eolian sediments, are high on theflanks or crests of paleodrainage divides. Calcicpaleosols are present throughout much of theOgallala, and vertebrate fossil assemblagesindicate a savannalike environment (Winkler,1985; Gustavson and Winkler, 1988). Theserelationships indicate that the Ogallala For-mation was not deposited as a wet alluvial fan(Seni, 1980) but rather as a series of alluvialvalley fills, which are interbedded with andoverlain by eolian sediment (Gustavson andWinkler, 1988) laid down in an arid to semiaridclimate.

The abrupt cessation of fluvial sedimentationin the OgallalaFormation suggests a diversionof streams flowing across the Ogallalalandscape.This interpretation is consistent with thesuggestionsby Gustavson and Finley (1985) andGustavson (1986a) that most Ogallala drainagesystems were diverted during the Tertiary toform the Pecos and Canadian Rivers.

The thick eolian sections overlying paleo-stream divides represent a long period of inter-mittent eolian sedimentation. The eoliansediments in the lower parts of these sectionsmay have been derived from ephemeral sandy,braided Ogallala streams. However, the upperparts of the eolian sections overlying the inter-fluves, as well as the eolian portions overlyingthe paleovalley fills, may have had differentsource areas. Streams on the High Plains hadbeen diverted to form the Pecos and CanadianRivers, and the floodplains of these riversbecame sources of eolian sediment.

The end of deposition of the Ogallala For-mation is marked by the development of themassive Ogallala Caprock caliche (calcrete)

(fig. 6). According toDarton (1899), the Caprockcaliche "is clearly a secondary deposit, formedafter the deposition of the sediments that itbinds together, by the precipitation of . . .calcium carbonate dissolved in ground water."Darton (1899) thought that caliches were theproduct of carbonate deposition by evaporationofshallow groundwaters drawn near the surfaceby capillary action. Although his interpretationof the process by which caliche forms is nowrecognized as incorrect, Darton (1899) correctlyobserved that caliches form only in arid andsemiarid areas and, therefore, that climatic con-ditions during the late Cenozoic were like thoseof the present.

Elias (1931) asserted that the Caprockcalichein Wallace County, Kansas, contained an alga{Chlorellopsis bradleyi Elias) that required apermanent body of waterfor its growth. On thebasis of the presence of the alga, he postulateda lacustrine environment for the deposition ofthe Caprock caliche. Many objected to thishypothesis, including Smith (1940), who arguedthat a widespread lake on the High Plains wasimprobable because it would have requiredreducing the tilt of the High Plains to nearlyhorizontal during deposition of the lake bedsand thenreturning the High Plains to an easterlytilt of 2 to 2.5 m/km (10 to 12 ft/mi).

Bretz and Horberg (1949a, b) identified anddescribed the formation of caliche as a pedogenicprocess. On the basis of petrographic analysesof pisolitic parts of the Caprock caliche,Swineford and others (1958) established that itpredominantly developed by soil-forming pro-cesses. The work of Smith (1940), Bretz andHorberg (1949a, b). Brown (1956), and Swinefordand others (1958) essentially ended the contro-versy over the origin of the Caprock caliche.Although many authors have discussed thevarious attributes of the Caprock caliche, pedo-genic and ground-water calcretes and silcreteswithin the Ogallala, especially those at the baseof the formation, have been either ignored ormentioned onlybriefly. The developmentof thick,laminated, brecciated, and recemented pisoliticcalcretes such as the OgallalaCaprock calicherequires extended periods of landscape stabil-ity, at least several hundred thousand years(Bachman and Machette, 1977; Gile and others,1981). Apparently neither extensive depositionnor erosion occurred in the High Plains duringformation of the Ogallala Caprock.

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Figure 6. View towardnorth ofnortheastrim of Palo Duro Canyon. The Caprock Escarpment is partlysupported by erosionally resistantunits including Caprock caliche (calcrete),which is present neartopof escarpment. Figure is standingon lower oftwo calcretes, which locallymake up Caprockcaliche.

Blanco Formation (Stop 5)

The upper Pliocene Blanco Formation isexposed in the walls of Blanco Canyon inCrosbyCounty, Texas, where it rests unconformablyon the OgallalaFormation (Bridwell Formationof the Ogallala Group of Evans, 1956, 1974,and Winkler, 1985). Similar units exposed alongthe valley of Yellow House Draw in Lubbock,Texas, have been correlated with the BlancoFormation at Blanco Canyon. Blanco depositsare a localized lacustrine-basin accumulationaccording to Evans and Meade (1945), althougha fluvial origin was advocated by Gidley (1903a),Matthew (1924a), and Frye andLeonard (1957).More recently both lacustrine and fluvial facieshave been identified (Pierce, 1973). Near the

center of the basin, Blanco strata mostly con-tain very fine sand, primary dolostone, andmagnesium-rich clays (attapulgite and sepiolite)and only minor amounts of sheetwash gravel.Near the margin of the basin, limestone andcoarser elastics, including caliche gravel andcobbles in arroyo fans, are found, whereas dolo-stone and magnesium-rich clays become rarer.The Blanco Formation is capped by a Stage IVcalcrete (see Machette, 1985, for descriptions ofcalcrete stages) and is in turn overlainunconformably by the Quaternary BlackwaterDraw Formation (Holliday, 1988).

Although the Blanco Formation in BlancoCanyon is overlain unconformably by theBlackwater Draw Formation, elsewhere it maybe interbedded with that formation. A 1-m-thicklens ofpinkish-orange very fine silty sand that

11

appears similar to sediment of the BlackwaterDraw Formation is interbeddedwith the BlancoFormation (?) in a quarry approximately 10kmnorthwest of Lubbock and on the north side ofU.S. Highway 84. If this material is in fact alens of Blackwater Draw sediments interbeddedwith the Blanco Formation, then the lower partof the Blackwater Draw is coeval with at leastpart of the Blanco Formation.

The age of the Blanco Formation is basedmainly on fossil vertebrates, tephrochronology,and magnetic stratigraphy. Vertebrate remainsthat make up the Blanco Local Fauna arethought to be a fauna of late Blancan (latePliocene) age. The Blanco Formation strata areoverlain by the Blackwater Draw Formation,which contains the Guaje Volcanic Ash (~1.4Ma old [Izett, 1977], 1.77 Ma old [Boellstorff,1976]) near the base of the formation. TheBlanco Ash lies near the middle of Blanco strataand has been dated at 2.8±0.3 Ma (Boellstorff,1976). Paleomagnetic studies of the MountBlanco section including both ash beds havedetermined that the entire section is reverselymagnetized (Lindsay and others, 1975), indi-cating that the Mount Blanco section and theBlanco Local Fauna lie in the lower Matuyama(reversed) magnetic interval and are between1.4 and 2.4 Ma old. Consequently, althoughthe Blanco Local Fauna is late Pliocene, theuppermost strata of the Blanco Formation mayin fact be Pleistocene in age.

Blackwater Draw Formation(Stops 1, 6, and 7)

The Blackwater Draw Formation is the prin-cipal surficial deposit of most of the High Plainsof Texas and New Mexico and supports thelucrative agricultural industry of the region(fig. 5). The unit is a sheetlike body of sedimentthat varies in texturefrom sandy in the south-west to clayey in thenortheast (fig. 7) and variesin thickness from a feather edge in the southand southwest to at least 27 m in the northand northeast (Reeves, 1976). Given the extent(roughly 100,000 km2) and economic importanceof the Blackwater Draw Formation, the relativelylittle research on its age and depositional originis surprising. Frye and Leonard (1957) were thefirst to study these deposits formally. They

used the informal term "cover sands" for thissediment, considering it to be of "Illinoian" agebecause it apparently was stratigraphically abovelacustrine sediments of "Kansan" age (the TuleFormation) and below lacustrine sediments of"Wisconsinan" age (the Tahoka Formation). Theyacknowledged that the "cover sands . . . mayinclude more than one age of deposit" (Frye andLeonard, 1957, p. 28). They identified the eolianJudkins Formation (Huffington and Albritton,1941), which lies adjacent to the southwest partof the Texas High Plains, as part of the complexcalled "cover sands," concluding that the coversands were of eolian origin, probably derivedfrom the Pecos River valley to the west andsouthwest. Frye and Leonard (1964, 1965) alsoidentified a strongly developed soil formed inthe upper part of the cover sands as a"Sangamon soil."

Reeves (1976) proposed that the informalterm "cover sands" be replaced by the formaldesignation "Blackwater Draw Formation"; hethought the unit had been deposited duringthe Illinoian. Reeves also noted that the term"Sangamon soil" should not be applied to theregional surface soil because of evidence ofmultiple soil-formation periods. Reeves (1976,p. 222) also identified a "thin cover of loess"overlying the Blackwater Draw Formation in thenortheast portion of the Llano Estacado (South-ern High Plains).

Several other investigations shed new lighton the physical properties, age, and origin ofthe Blackwater Draw Formation. The mineral-ogy of selected soils at the surface of theBlackwater Draw Formation was studied byAllen and others (1972). The coarse fraction ofthe sediments contains primarily quartz andsome feldspar, and the clay minerals are dom-inantly smectite and illite. Seitlheko (1975)provided the first quantitative data on texturalvariation of the surface soil of the BlackwaterDraw Formation and presented several signifi-cant conclusions. He clearly showed, for ex-ample, that the Blackwater Draw Formationfines from southwest to northeast, which sup-ports the hypothesis that the sediments origi-nated in the Pecos Valley and were depositedby wind. Furthermore, Seitlheko showed thatthe silty and clayey sediments in the northeastportion of the areaare the result of this down-wind fining and not a separate "loess cover."Allen and Goss (1974) and Hawley and others

12

Figure 7. Distribution of BlackwaterDraw Formation, showing fining of surface soils to the northeast. AfterChepil and others (1964) and Godfrey and others (1973). Coarsest soils occur east and north of the Pecosand Canadian Rivers, suggesting that these may be the source areas for at least the upper part ofBlackwaterDrawFormation. Modern dominantwind directionsshown.

13

(1976) recognized that, locally, the BlackwaterDraw Formation may contain as many as sevenwell-developed soils, including the surface soil,indicating that the formation contains a numberof individual layers, each deposited episodically.Limited absolute age control, discussed morefully at the individual stops and in Holliday(1989, in press) suggests that deposition tookplace throughoutmuch of the Pleistocene.

A preliminary paleomagnetic study of thelowermost of five buried soils in the BlackwaterDraw Formation near Bushland, Texas (approxi-mately 66 km [10 mi] west of Amarillo), dem-onstrates that the remnant magnetization,apparently acquired during pedogenesis, isdominantly reversed. This suggests that the soilformed during the last reversed-polarity epoch,which ended about 0.79 m.y. B.P. (E. E. Larson,personal communication, 1984).

Tule Formation (Stop 8)The Pleistocene Tule Formation is exposed

around the margin of Mackenzie Reservoir atthe boundary of Swisher and Briscoe Counties,Texas. These strata occupy a large erosionalbasin and unconformably overlie both theTriassic Dockum Group and the Miocene-Pliocene OgallalaFormation. Stratigraphy of theTule Formation was discussed by Evans andMeade (1945), Frye and Leonard (1957), Reeves(1976), and Schultz (1986). Tule Formationsediments generally have been interpreted aslacustrine deposits, although Frye and Leonard(1957) thought they were fluvial. The presenceof thin limestone and dolostone beds andlaminated, horizontally bedded mudstonesstrongly suggests that the Tule Formation islacustrine.

Evidence of the age of these beds recentlyhas been reviewed by Schultz (1977c; 1986;Stop 8, this guidebook, p. 60). On the basis ofvertebrate remains and the presence of LavaCreek B Ash near the top of theTule Formationand the Cerro Toledo-X Ash near the base ofthe formation (Izett, 1977; Izett and Wilcox,1982), Schultz suggested that the Tule bedsspan most of the Irvingtonian Mammal Age (earlyand middle Pleistocene). Previously, Evans andMeade (1945) referred to these beds as middlePleistocene, whereas Frye and Leonard (1957)thought theywere Kansan in age.

The Clarendon Fauna andthe Clarendonian LandMammal Age (Stop 14)

Establishment of "Provincial" and"Land Mammal" Ages

The Texas Panhandle is significant in Tertiaryvertebrate paleontology and biostratigraphybecause it contains the type localities of faunasupon which the Wood and others (1941) com-mittee based three of the Provincial Ages fortheTertiary: the Clarendonian (Stop 14), theHemphillian (Stops 15 through 17), and theBlancan (Stop 5). The first two were identifiedon the basis of fossils collected from the OgallalaFormation, whereas the Blancan is based onthe local fauna from thewhite lacustrine basin-fill deposits at "Mt. Blanco" and the adjoiningdraws, near the "old rock house," north ofCrawfish Draw, Crosby County, Texas (Woodand others, 1941, p. 12).

These Provincial Ages, like the others for theTertiary, were based on first and last appear-ances of mammalian genera in North Americaas well as on "index" genera restricted to theage and on other genera common during orcharacteristic of the age. The ages were notdefined in relation to epochs or the Europeanstandard, although approximate equivalentswere indicated. Stirton (1936a) thought the agesof the threetype faunas from Texas were early,middle, and late Pliocene, respectively. A studyof the European Tertiary (Berggren and VanCouvering, 1974) indicates correlations differentfrom those of Stirton (1936a) and Wood andothers (1941). It now appears that theClarendonian is late Miocene, the Hemphillianis latest Miocene to earliest Pliocene, and theBlancan is equivalent to most of the Pliocene;the views of earlier workers (for example, Gidley,1903a; Osborn and Matthew, 1909) have thus

been vindicated.Savage (1962) and Evernden and others

(1964) redesignated the original "Provincial Ages"as "North American Land Mammal Ages." Theyalso argued against the use of the term "ages"inreferring to the equivalent continental depositsor "stages," as had originally been allowed bythe Wood and others (1941) committee. Thecommittee did not have substantial or explicit

14

lithostratigraphic or biostratigraphic controlincluding measured and described sections,vertical ranges, and geographic distribution oftaxa.

Wilson (1967) noted that, whereas the tax-onomic criteriafor each age as proposed by theWood committee were thought to be generallyapplicable throughout North America, thecurrent basis for correlation was largely thedegree of evolutionary advancement,migrationof Old World mammals into North America, andthe negative evolutionary criterionof extinction.Tedford and others (1987) later used firstappearances of immigrant genera, as well asextinctionof certain taxa, to refine and subdividethe "Land Mammal Ages" of the late Tertiary.

Introduction, HistoricalBackground, and Type Locality

The Clarendonian Provincial Age was origi-nally described by Wood and others (1941, p. 12)as "based on the Clarendon local fauna (andmember?) near Clarendon, Donley County, Pan-handle of Texas" (fig. 1). The name "Clarendonlocal fauna" (ClarendonFauna, this guidebook),in turn, has been applied to an aggregate offossil vertebrate species, mostly mammalian,collected since 1892 from a number of local-ities scattered over a 100-km2 (40-mi2) areaimmediately north of the Salt Fork of the RedRiver and north and east of the town ofClarendon, Texas (fig. 42) (Stop 14). Clarendonlies on the east edge of theSouthern High Plains(Llano Estacado) at an elevation of 816 m(2,719 ft) above sea level. Fossils from this areawerefirst collected and reported by Cope (1893),who referred to the beds containing them asthe "Loup Fork," an obsolete term once appliedto upper Tertiary strata inNebraska (see Osbornand Matthew, 1909, p. 84, and Simpson, 1933,p. 101, for a summary of the history of theterms "Loup River" and "Loup Fork").

The term "Clarendon beds" was proposed byGidley (1903a, p. 632), who made extensivecollections of vertebrate fossils for the AmericanMuseum of Natural History from 1899 through1901, but the name never gained general appli-cation. The fossil beds are now recognized asfacies of the Ogallala Formation, having beenplaced in this formation by Stirton (1936a,p. 181), who thought they were lower Pliocene.

Unfortunately, no comprehensive study or de-scription of the Clarendon Fauna has ever beenpublished, although single species have beendescribed inshort papers or in largepublicationsdealing with certain taxonomic groups. Inaddition, papers on other "early Pliocene" (nowMiocene) faunas have occasionally referred tofossils from the Clarendon Fauna. At present,about 30 fossil-producing sites areknown fromthe area just north of the Salt Fork of the RedRiver (fig. 42). Detailed biostratigraphic analyseshave not been done on most of these sites, butavailable faunal evidence indicates that most ofthem are about the same age, a few slightlyyounger.

Webb (1969a) attempted to revise theClarendonian Mammal "Age" and to establishthe biostratigraphic basis for its identificationas a time-rock unit (stage)by selecting a sectiondescribed by Cummins (1893) as the type sec-tion. The following description and section arequoted from Cummins (1893, p. 204):

On the ranch of Mr. Stanton, twelvemiles west of the town of Clarendon onthe Mobeetie road is a very favorablelocality for the collection of characteristicvertebrate fossils of this bed. Prof. Copeand myselfvisited that locality and madea very interesting collection, which have[sic] been described and figured by him,providing beyond question that the bedsare Loup Fork. They are underlaid bythe Triassic [Permian, actually]. Theupper part of the section [which is givenbelow] is probably the Goodnight beds.No fossils were found at the place wherethe section was made, but I concludethat they are later, upon stratigraphicand lithological reasons.

The Loup Fork is composed ofalternating beds of bluish and almostpure white sand. The fossils were in afine state of preservation and were easilyobtained. Most of the samples we col-lected were picked up on the surface, asat only one place did we attempt tosecure any by excavation and that onlyin a small way, but were well paid forour labor in finding excellently preservedspecimens.

The following sectionwas made at thisplace, showing the relation of the LoupFork beds to the overlying strata:

15

1. Whitish sandyclay 20 feet2. Sandy clay,with manyrounded

siliceous pebbles of differentsizes 20 feet

3. Yellowish sand 40 feet4. Indurated whitesand 40 feet5. Yellowsandy clay, with the

sand moreor less predom-inating in places. In places thesand is hardened,whileinothers the clay is moreor lessconcretionary 250 feet

6. Alternatingbeds ofbluish clayandwhite sand (Loup Fork) 30 feet

400 feetUnfortunately, Webb did not (and, in fact,

could not) present a detailed biostratigraphicanalysis of this section but instead gave acomposite fauna! list of mammals known fromthe various localities north and northeast ofClarendon and west of Goldston, a small ghosttown 14km (9 mi) north of Clarendon. This listwas incomplete, however, because several pub-lished records, including that of Paratocerasmacadamsi (Frick, 1937) and TeleocerasfossigerCope (Johnston, 1937a), were omitted, not tomention the unpublished specimens in the largercollections from the areathat would have addedmore taxa to the list. Finally, the faunal listdoes not take into account the possibility thatthe fossils may have come from differentstratigraphic levels or zones.

Cummins' locality fails to meet the criteria ofa type section on several counts. The preciselocation at which he measured his sectioncannot be determined from the published data,and the beds were not described adequately tobe recognized in the field. The Stanton Ranchapparently covered a large areaat the time andthe reference to "twelve miles west of the townof Clarendon on the Mobeetie road" is certainlyin error because Mobeetie is northeast ofClarendon. The old Mobeetie road probablyfollowed the route of State Highway 70 northacross the Salt Fork at least as far as theintersection with the Country Club Road atGoldston. Fossil-producing sites are commonin the vicinity of the old Goldston schoolhouse,and it is likely that Cummins actually meant19 km (12 mi) "north" and not "west." The localrelief around Goldston is less than 60 m (200 ft),and Cummins' 122-m (400-ft) section musteither represent an error in measurement or bea composite made over a considerable distance.

Whereas it seems impossible to refine orredescribe Cummins' "type section" in terms ofrecent stratigraphic knowledge of the area, thedesignation of a "type locality" based on thefauna collected by Cummins and Cope andreported by Cope (1893) is possible. Examinationof thesefossils at the Texas Memorial Museum,The University ofTexas at Austin, indicates thatmost, if not all, were collected at the adjacentDilli and Charles Risley ranch localities nearthe head of Turkey Creek, 1.6 km (1 mi) northand 1.6 km (1 mi) east of Goldston, and about16 km (10 mi) north of Clarendon. Character-istics such as the preservation and dark browncolor of the bone as well as the concretionarymatrixenclosing it are similar to thoseof fossilscollected later from these localities by workersfrom the University of California and WestTexasState University.

At present, the Clarendon Fauna is used asa biostratigraphic zone in correlation, althoughit lacks proper characterization (Tedford, 1970,p. 693) and is among the poorest known ofClarendonian faunas. Precise biostratigraphicanalysis is difficult in the region because rocksequencesare too sparselyfossiliferous and tooincomplete to determine local range zones ofspecies. There are about 30 fossil sites known,but many are too widely separated to be easilycorrelated. Fossiliferous beds often cannot betraced laterally because of poor exposures,removal by erosion, rapid changes in channeland floodplain facies, or complete isolation insinkhole deposits. Nevertheless, physical cor-relation between some sites is possible; faunalsimilarities may aid in the correlation of others.Recent stratigraphic and faunal studies basedon the large quarry samples in the Frick col-lection in New York indicate that most of thereported faunas come from the more fossiliferouslower levels in the region (for example,MacAdams, Grant, Risley, Farr and Bromleylocalities), although a few sites (for example,Gidley's 3-Toed Horse Quarry) appear to repre-sent slightly younger stratigraphic levels (Tedfordand others, 1987).

Another difficulty encountered in definingthe Clarendonian Stage is the lack of directsuperpositional relationship with subjacent orsuperjacent stages in the type area (Tedford,1970, p. 693). In addition, the original defini-tion of the Clarendonian as a Provincial Agedepended heavily on the first occurrence of

16

Table 1. Correlation chart of Clarendonian and Hemphillian faunas of the Great Plains

taxa, many of which are not known from thetype Clarendon Fauna. Webb (1969a, p. 15)stated, however, that this situation, althoughnot ideal, presents no real problem becausethe Clarendon Fauna is diversified enough topermit correlation elsewhere in the same bio-logical province with sections in which relevantsuperpositional relationships can be established.In north-central Nebraska, for example, theequivalent of most of the Clarendon Fauna isthe Minnechaduza Fauna (early Clarendonian),which includes all local faunas from the lower

part of the Ash Hollow Formation (CaprockMember). In this region, subjacent and super-jacent faunas are present, and Webb (1969a)extended the concept of the Clarendoniandownward to include the Burge Fauna (nowconsidered late Barstovian) in the Burge SandMember of the Valentine Formation and up-ward to include the Leptarctus Quarry (lateClarendonian) in the high stream channels thatcut into the Caprock Member of the Ash Hollow(table 1). Beneath the Burge Sands are oldersediments in the Valentine Formation that also

LANDMAMMAL AGE KANSAS- SOUTHEPOCH (Ma) TEXAS OKLAHOMA NEBRASKA DAKOTACOLORADOAGE

PLIOCENELU

Axtel,Christian Ranch,and Currie Ranch

VirgilClark, etc.,GravelPits

CoffeeRanch (=Miami),Goodnight

Optima (=Guymon) Edson and Rhino Hill(Kansas)

<_J

XCL2LUI

BoxT Wray (Colorado) Cambridge (=Ft. 40)Oshkosh

hre■-<:LU

Higgins (=Sebits Ranch)Feltz Ranch

V. V. Parker Pits Arnett (=University ofOklahomaAdair RanchQuarry=Port of Entry)

3u.

1LU■z.LUOQ Cole Highway Pit

Clarendon (Gidley's3-Toed-Horse Quarry)

Capps = Neu = PrattDurham Leptarctus Quarry

and Xmas-Katchannels

o

I<zOQs:LUtr

o

Lil

510 Exell and Coetas Creek

Laverne (=Beaver) Minnechaduza

Big SpringCanyon,

Mission, &Wolf Creek>1

DC<LU

Clarendon (MacAdams,Grant, Risley, Farr,

Bromley)

WaKeeney (Kansas)

11 Lapara Creek(from Gulf Coast)

<ItoDCm

12Burge

LU

5QA13282c

17

contain late Barstovian faunas (see Skinner andJohnson, 1984, for a review of the Tertiarystratigraphy and fossil vertebrates from north-central Nebraska).

Age and CorrelationThe Clarendonian Land Mammal Age repre-

sents a span of late Miocene time from about11.7 to about 9 Ma ago; the division between"early" and "late" Clarendonian occurs at about10 Ma (table 1; Tedford and others, 1987). At

present, the Clarendon Fauna is thought toinclude taxa and sites of both early and lateClarendonian age, thus correlating with earlierAsh Hollow faunas of north-central Nebraskaand south-central South Dakota (Skinner andothers, 1968, p. 404; Skinner and Johnson,1984). Most of the Clarendon faunal localitiesappear to be early Clarendonian and to representMinnechaduza age equivalents, whereas a few,such as Gidley's 3-Toed Horse Quarry, are some-what younger and seem to correlate best withthe late Clarendonian Leptarctus Quarry andthe Xmas-Kat channel assemblages (Tedfordand others, 1987). Other Clarendonian faunasin the Great Plains Province include the BigSpring Canyon (Gregory, 1942), Mission(Macdonald, 1960), and Wolf Creek (Green,1956) Local Faunas of South Dakota, the UpperSnake Creek Faunas (in part) of Nebraska(Matthew, 1924b; Skinner and others, 1977),the Wakeeny Local Fauna of Kansas (Wilson,1968), the Laverne (=Beaver) Local Fauna ofOklahoma (Hesse, 1936a), the Exell (Dalquestand Hughes, 1966) and Coetas Creek (Patton,1923; Schultz, 1977a, b) Local Faunas from thenorth Texas Panhandle, and the fauna of theCouch Formation from the south part of theTexas Panhandle (Evans, 1949, 1956; Winkler,1985, 1987). The Lapara Creek Fauna of theTexas Gulf Coastal Plain (Patton, 1969) is earlyClarendonian. Correlation of these faunas and,hence, of their respective provinces is madepossible by a high degree of similarity betweentheir respective taxa, especially of the horses.Refined correlation of Clarendonian faunas ofthe Great Plains or Gulf Coastal Plain with theCerrotejonian and Montediablan MammalianStages of the Pacific Coast Province (Savage,1955a) is more difficult because of greater geo-graphic differences and distances and becausethere are fewer shared taxa. In general, however.

the early and late Clarendonian faunas of theGreat Plains and Gulf Coastal Plain correlatewith the Cerrotejonian and Montediablan Stages,respectively fTedford and others, 1987).

The Hemphillian LandMammal Age, TexasPanhandle and AdjacentOklahoma(Stops 15 through 17)

IntroductionThe Hemphillian Provincial Age was originally

described by Wood and others (1941, p. 122) asbeing "based on the Hemphill member of theOgallala,which includes both the Hemphill LocalFauna from the Coffee Ranch Quarry and theHiggins Local Fauna, Hemphill County, Pan-handle of Texas" (the Higgins Local Fauna isactually in Lipscomb County, Texas [fig. 1]). The"Hemphill Member" is not recognizable as a dis-tinctbthologic unit, however, and is an obsoleteterm. It represents an upgrading of the term"Hemphill beds" proposed by Reed andLongnecker (1932, p. 20): "Since these beds,according to the fauna, represent a heretoforeundescribed formation of the Lower Pliocene,the name HemphUl beds is here given to themtobe applied as a faunal horizon." They thoughtthe fauna was intermediate in age betweenClarendon and Blanco Faunas and describedabout two dozen fossil sites from various levelswithin the section, most of which producedonly a few specimens. Their Locality 20 at theCoffee Ranch was the most productive site andlater became the type faunal locality for theHemphillian Land Mammal Age (Evernden andothers, 1964).

Age and CorrelationThe Hemphillian represents a span of time

from about 9 toabout 4.5 Ma ago, and it is nowpossible to distinguish between early and lateHemphillian faunas. This division, which occursat about 6 Ma, is marked by the extinction ofmany genera characteristic of the Clarendonianchronofauna and by the appearance of new

18

immigrant taxa, as described in the followingsection. Early Hemphillian faunas may be fur-ther subdivided into "early early" (approximately9 to 7 Ma ago) and "late early" (approximately 7to 6 Ma ago). The Coffee Ranch (=Miami) LocalFauna (type Hemphillian) dates to the beginningof the "late" Hemphillian, however.

Until recently the Hemphillian Land MammalAge was thought to be of middle Pliocene age(Wood and others, 1941). According to correla-tions by Berggren and Van Couvering (1974),the Hemphillian ended about 4.5 Ma ago andtherefore straddles the Miocene-Pliocene bound-ary at about 5 Ma.

In Lipscomb County, Texas, in the northeastcorner of the Panhandle and in adjacent EllisCounty, Oklahoma, a sequence of faunas rang-ing in age from late Clarendonian to latestHemphillian can be placed in stratigraphic suc-cession. These and other important Hemphillianfaunas of the region are described in Stops 15,16, and 17, this guidebook, p. 95 through 114.

Faunal Turnover in theHemphillian

The Texas Panhandle and adjacent areas ofOklahoma provide an excellent sequence of LateTertiary faunas that document the significantchanges in the vertebrate faunas of the SouthernHigh Plains from early Clarendonian to latestHemphillian time. Many of the taxa cited byWood and others (1941) as characteristic ofthese ages are present in the faunas of theregion.

Wood and others (1941) thought the generaAgriotherium, Dipoides, Ringoceros, and Plesio-gulo were index fossils of the HemphillianProvincial Age, which also saw the first appear-ance of ground sloths, Lutravus, Machairodus,and Taxidea [Pliotaxidea), and the last appear-ance of Aphelops, Blastomeryx, Mylagaulus,Osteoborus, Pliauchenia, Pliohippus, Prosthen-nops, Sphenophalos, and Teleoceras. Hypolagus,Megatylopus, Nannippus, and Neohipparionwerealso thought to be characteristic of this age.

Recent work in vertebrate paleontology hastended to downplay the importance of indexfossils and has extended or restricted the geo-logical range of certain taxa. For example,Dipoides, Nannippus, and Hypolagus are knownfrom the Blancan, and the latter genus, as well

as Megatylopus and Neohipparinn, are known tooccur in the Clarendonian. Blastomeryx haddisappeared by the end of Clarendonian time,whereas Osteoborus is now restricted to theHemphillian. The most current analysis ofNeogene land mammal ages and their charac-teristic taxa and evolving chronofaunas is thatof Tedford and others (1987). Because theHemphillian lasted about 4 to 5 Ma, it is possibleto identify important differences between earlyand late Hemphillian faunas. Early Hemphillianfaunas (for example, Arnett of Oklahoma,Higgins and Box T of Texas, and Cambridge[=Ft. 40] of Nebraska) include an admixture ofClarendonian holdover genera such as Epicyon,Leptarctus, Barbourqfelis, Procameliis, Aepy-camelus, Cranioceras, Pseudoceras, Coiippus,Cormohipparion, and Pliohippus and newgenerasuch as Amebelodon, Nimravides, Osteoborus,Indarctos, Eomellivora, Machairodus, Pliometa-nastes, and Thinobadistes. Late Hemphillianfaunas (for example, Coffee Ranch andGoodnight of Texas, Optima (=Guymon) ofOklahoma, and Edson and Rhino Hill ofKansas)lack many of these Clarendonian and earlyHemphillian genera and are marked by the firstappearance of Megalonyx, Plesiogulo, Agriothe-rium, Rhynchotherium, Alforjas, and Dinohippus.Latest Hemphillian faunas (for example, Axteland Christian Ranch of Texas and Yepomeraand Ocote of Mexico) have more advancedspecies of Dinohippus, Astrohippus, Agriotherium,and Osteoborus, as well as the first appearanceof genera more typical of theBlancan.

Blanco Formation (Stop 5)

History ofInvestigations andInterpretations

The earliest work in the Blanco Canyon areais that of W. F. Cummins, who in 1890 appliedthe name Blanco Canyon Beds (shortened byhim to "Blanco Beds" in 1892) to all the post-Cretaceous deposits of the High Plains ofTexas(see Cummins, 1890, 1891, 1892, 1893).Cummins thought these deposits had been laiddown in a great inland "sea" or lake. Fossils hecollected were sent for identification to E. D.Cope, who later accompanied Cummins in thefield. In 1900 and 1901, J. W. Gidley (1903a)made extensive fossil collections from theBlanco

19

for the American Museum of Natural Historyand concluded that the beds were of limitedextent and that theyrepresented a valley depositofan aggrading stream. He wrote that "theocca-sional beds of diatomaceous earth are easilyaccounted for by supposing that there were inthis ancient valley occasional ponds filled withclear water, enduringfor various periods of time,partially or totally isolated from the stream thatran through the valley." Matthew (1924a) alsothought the Blanco was a stream valley depositbut thought that the light-colored, fossil-bearingstrata were a channel facies that interfingeredwith the bordering, reddish-brown Pliocenesands and clays that he took to be a floodplainfacies of the Blanco: "The Blanco beds weredeposited in a broad and shallow slowly aggrad-ing stream valley with a slow-flowing, probablyintermittent stream of about the type of thepresent Blanco Creek. The valley would be partlyoccupied then as now by abandoned streamchannels forming ponds and muck holes."

Evans and Meade (1945, p. 492) believed theBlanco beds (Stop 5, this guidebook, p. 44) "tobe lacustrine deposits laid down in broadshallow basins rather than deposits of a largestream valley." Their main lines of evidencewere

(1) The coarser elastics of the Blanco bedsare of indigenous origin, consisting ofpebbles derived from the hard calichecap rock of the surrounding Pliocene.These coarser materials occur on theshallow-lying marginal slopes, whilethe finer-grained sediments occupythe central and deeper-lying parts ofthebasin. This arrangement is the sameas in existing playas of the region andis the reverse of the condition found instream-laid deposits.

(2) The main body of exposed beds is well-stratified, some of the beds beingtraceable across most of the exposedareas.

(3) The types of sediments, particularly thebentonitic clays, fresh-water limestones,and the more localized beds of diatomiteare indicative of quiet water deposition.

(4) No evidenceexists along Blanco Canyonor its tributaries of a connecting filledvalley segment between the two areasof Blanco beds or of an extension ofsuch a valley either above or belowthese areas.

The geologic history of the Blanco basin asinterpretedby Evans and Meade (1945, p. 492)and Evans (1948, p. 617-619) can be summar-ized as follows:

(1) After an alluvial plain developed in middleor late middle Pliocene time, a period ofnondeposition occurred during whichclimatic conditions were dry enough tofavor the development of an extensivecaliche zone near the surface of the HighPlains.

(2) Following thecaliche development, basinsformed to depths of 18 or 21 m (60 or70 ft), possibly as a result of deflation,which would require a dry climate andappreciable time. That a caliche caprockexisted before basins developed is sub-stantiated by the presence of calichepebbles and boulders in thebasal memberof the Blanco section.

(3) The essentially unbroken sequence oflacustrine strata composing the Blancobeds indicates nearly continuous deposi-tion in permanent or nearly permanentbodies of water for a period long enoughfor the basins to fill almost to the level ofthe surrounding plains. Such permanentlakes would seem to require a sustainedperiod of moistclimate.

(4) After the filling of the Blanco basins, orperhaps during the last stages of filling,thin deposits of eolian silt, sand, and vol-canic ash were laid down, which were latereroded and largely removed by wind. Awidespread mantle of windblown sandsand silts was then laid down over thesurrounding plains and across the erodedsurface of the basin deposits to form thepresent-day plains surface. The wind-eroded remnants of unaltered ash andloess as well as the overlying, probablyeolian sands indicate the return of morearid conditions following the relativelyhumid Blancan stage.

Frye and Leonard (1957, p. 20-21) arguedagainst Evans and Meade's interpretation of theenvironmental history of the Blanco beds, citingas evidence the conspicuous absence of aquaticmollusks and certain types of vertebrate fossilssuch as fish and amphibians, all ofwhich wouldhave been present had a large permanent lakeexisted underhumid climatic conditions for anyextendedperiod. They argued that "all theknown

20

facts . . . point to alluviation by streams of verylow gradient flowing across a semiarid terrain."

Frye and Leonard (1957, p. 20-21} thenwenton with theirclaim:

That the Blanco was deposited byfluviatile mechanisms is attested by localchannel deposits, including largeabraded cobbles of Ogallalacaprock, butthe general fine texture of the sedimentspoints with equal clarity to stream regi-men of low gradient. Such a stream orstreams, shifting, anastomosing, andwith extremely unstable bottom condi-tions seems to account for the absenceof fossil aquatic mollusks, which areunable to surviveunder such conditions.An unstable stream regimen likewisewould account for the lack of fishes,amphibians, and aquatic turtles, theextreme paucity [absence] of beaverremains, and the lack of rodents withaffinities to the muskrats.

Contemporary semiaridity of the localclimate seems almost self-evident. Hada humid local environment prevailedduring deposition of the Blancan beds,whether by lacustrine or by fluviatilemechanisms, the surrounding plainwould certainly have supported somekind of terrestrial molluscan fauna, theshells of which would have been carriedinto the Blancan sediments by tributarystreams. The absence of such molluscanremains, the lack of fossil amphibiansor fossil microtine rodents—animalsthat might be expected to have thrivedon the plains under humid climaticconditions—sustain the deduction of asemiarid,rather than a humid, contem-porary environment.

Pierce (1974), on the basis of his mineralogicaland sedimentological studies supplemented bya study of pollen, diatoms, and ostracodes,concluded that the Blanco beds were depositedin a large playa lake during an arid to semiaridclimatic interval. Deposition, which occurredduring latest Pliocene or earliest Pleistocene (pre-Nebraskan) time, was marked by two episodes,one very short, of semipermanent to permanentwater accumulation in a closed basin. This basinmay have originated in the shallow depressionof an abandoned Pliocene drainage channel andmay have been enlarged by deflation.

Palynological studies by Pierce (1974) revealabimodal flora containing a few aquatic or ripar-ian species such as hazel,willow, and pondweed,and a larger, more diverse, semiarid flora com-posed of grasses, cactus, saltbush, ragweed,juniper, Mexican chokecherry, and salt cedar.Diatoms from the Blanco Ash/diatomite unitare generally tolerant of alkaline environmentsand include species that can tolerate a subaerial(above water)habitat and that, while preferringcalcium-rich environments,are capable ofwith-standing extreme drought and great variationsinmineral concentrations. Invertebrates are rare;only one species of ostracode, Candona para-caudata, has been identified. No mollusks wererecovered from the Blanco by Pierce, althoughDalquest (1975, p. 45) mentions that a fewaquatic snails are found in the sandy mud be-neath the diatomite along with abundant fos-sils of reeds and aquatic plants.

Pierce (1974, p. 16) concluded thatthe flora and fauna strongly support asemiarid to arid climatic interpretation.The apparent absence of fishes, aquaticturtles and mollusks suggests that wateraccumulation was generally intermittentand transitory. While thebasal sand andcyclic units suggest seasonal wateraccu-mulation, only very rare diatoms havebeen recovered from this unit. Thelacustrine sands of the main bone bedzone, below the diatomite, can be inter-preted as at least seasonal water on thebasis of the ostracode species recovered.Candonid ostracodes are normally springbloomers. Their occurrence suggests anearly spring precipitation maximum. Theflora of the diatomite unit also suggestsonly seasonal water accumulation,although semipermanent watermay haveaccumulated at this time. The absenceof an invertebrate fauna in the diatomiteis not surprising, considering the highlyleached character of this unit. Above thediatomite, there is little indication ofother than intermittent ponding, withsepiolite-rich immature paleosols com-prising the dominant lithology. . . . Theabsence of the pollen of conifers,apparently übiquitous during all pluvialperiods of the Pleistocene, and therestricted invertebrate fauna suggestsstrongly that the Blanco beds accumu-

21

lated during latePliocene or earliest (pre-Nebraskan) Pleistocene time. Thedistinctive climatic reversal of theNebraskan Glaciation marked by a sig-nificant floral change, is not indicated.

Studies by Dalquest (1975) support theconcept of deposition under arid or semiaridconditions and contradict Evans and Meade'sconcept of a permanent or partly permanentlake occupying a closed depression of consider-able extent. Dalquest also observed, among otherthings, the discontinuity of some of the minorstrata, which is in strong contrast to the even,uniform sediments typical of the deflation basinsofWestTexas, as described by Evans and Meade(1945). He stated (p. 5-6) that

the bentonitic clays and freshwaterlimestones indicate still waters, but thesemight have occupied low areas or small,temporary depressions after floods orheavy rains. This type of depositionoccurs today inarid areas. The diatomite,however, definitely is a lacustrinedeposit. The sandy mud depositbeneaththe diatomite beds can often be tracedlaterally for 100yards or more awayfromthe diatomite itself. The deposits areclearly recognizable as pond deposits bytheir evenness and uniformity of sedi-ments, and by their contained fossils.Remains of aquatic plants are abundant,

and some few fossil aquatic snails alsooccur. The ponds, however, were shallowand apparently limited to areas of a fewacres. No fish or aquatic turtle remainshave been found, and fossil wood andhackberry seeds are usually as abundantas fossils of emergent vegetation. Itshould be emphasized that thesedeposits within theBlanco sediments arereadily recognized as lacustrine. . . . Theabsence of fossils of aquatic vertebratesand the varied nature of the sedimentsin theBlanco Formation argue against aclosed depression occupied by a lake. Itseems more likely that the depositsaccumulated in a shallow, drained ratherthan closed basin, formed by streamerosion or deflation. Coarser materialswere deposited on the valley slopes, butfloods or mudflows carried some gravelsfar out into the valley. Slope wash andwind-blown materials filled thebasin, thematerials being sorted and reworked bywandering shallow streams during wetintervals. Heavy rains, perhaps seasonal,carried clay materials that accumulatedin low areas. Dry intervals permittedaccumulation and leaching ofcarbonatesinto sands and clay deposits to form thecalcareous limestones and caliche.

22

Stop 1: Blackwater Draw Formation TypeLocalityV. T. Holliday

The Quaternary Blackwater Draw Formation type section, northwest ofNew Deal Texas, containsfour buried soils plus the surface soil The buried soils are similar to, but better developed than, thesurface soils of the central Southern High Plains: Paleustalfs and Paleustolls of the Amarillo-Acuff-Mansker soil association.

The type section of the Blackwater Draw For-mation lies in a roadcut northwest of New Dealin north Lubbock County on the west side ofBlackwater Draw 8 km (5 mi) north of farm-to-market road (FM) 1294 and approximately3.5 km (2.2 mi) west of Interstate Highway 27(figs. 1 and 8). The section is about 10 m (30 ft)thick—the modern High Plains surface at thetop and the Ogallala Caprock caliche at thebase (fig. 9, table 2). The Blackwater DrawFormation is the "Illinoian cover sand" of Fryeand Leonard (1957). Reeves (1976) proposed theformation name for the deposits, and Gustavsonand Holliday (1985), Holliday (1989, in press),and Holliday and Gustavson (in press) showedthat the sediments accumulated throughoutmost of the Quaternary.

Thereare two striking features about the typesection: (1) its general homogeneity and (2) thenumber of strongly developedburied soils (fig. 9).The overall color, texture, and structure of thesection arerelatively uniform. Close inspection,however, reveals that the section contains atleast four buried soils in addition to the modernsurface soil (fig. 10). The overall homogeneity ofthe section is due to the soils having about thesame degree of pedologic expression: reddish-brown color (2.5YR to SYR hues), moderate tostrong prismatic structure containing commonfilms of illuvial clay on the ped faces, andStage II to 111 calcic horizons (after Gile andothers, 1966). No A or C soil horizons areapparent other than theA horizon of the surfacesoil, and no primary sedimentary structures arepreserved.

The buried soils are similar to the well-developed, regional surface soils of the centralportion of the Southern High Plains: Paleustalfsand Paleustolls of the Amarillo-Acuff-Manskersoil association (Godfrey and others, 1973). Atthis stop the surface soil has a thick, reddish-brown (SYR hues) argillic horizon (50 to 149 cm;table 2) and a dominantly coarse prismatic

structure. Clay films are apparent on ped facesand are common in thin section. Below theargillic horizon is a Stage 111 calcic horizon(149 to 290 cm). The boundary between theargillic and calcic horizons is abrupt and sub-horizontal, similar to a depositional contact.Such an abrupt boundary is typical of theregional surface soils, however, and is pedogenic.All characteristics of this soil indicate that it iswell developed.

Morphologically, the buried soils are morestrongly developed than the surface soil (table 2).At least some parts of each profile exhibit(1) 2.5YR hues, (2) more continuous and thickerclay films on ped faces, (3) a higher percentageof clay films in thin section, and (4) an angularblocky structure. The blocky structure appar-ently is due to higher illuvial clay content, sug-gested by the abundant clay films.

The morphologies of the calcic horizons inthe buried soils are somewhat similar to oneanother but distinctly different from those inthe surface soil. The buried calcic horizons areexpressed either as patchy films and coats onped faces, generally the vertical faces, or asvertically oriented, rootlike nodules about 1 to3 cm thick. These nodules appear to follow thejoints between prismatic peds, and this mor-phology is sometimes informallyreferred to as"ladder structure" (McGrath, 1984, p. 131)(fig. 11). Some think ladder-matrix carbonatehorizons represent recalcified argillic horizons(for example, McGrath, 1984). Some evidenceshows that these horizons represent formerlyextensive calcic horizons that underwent dis-solution. The upper boundaries of the ladder-matrixcalcic horizons are commonly horizontaland abrupt. This suggests that the horizons wereoriginally similar to the surface-soil calcichorizon but were subsequentlysubjected to dis-solution, carbonate concentrating along veins(ped faces?) and forming nodules. Illuvial clayis common in and on peds between carbonate

23

Figure 8. Map of Lubbock, Texas, area showing Field Trip Stops 1, 2A, and 28. Derived from LubbockSheet, U.S. GeologicalSurvey (1:250,000 series). See figure 1 for location.

nodules in the ladder-matrix horizons, but suchclay is not apparent in the surface-soil calcichorizon. This -would further suggest that clayilluviation accompanied or followed carbonatedissolution.

Two X horizons (zones dominated by CaCO3accumulation)are exposed at the bottom of thesection (table 2). The Klb4 (upper X horizon ofthe fourth buried soil) horizon is a massive,nonindurated calcic horizon, probably repre-

senting a buildup of carbonate that was theresult of the impermeable nature of the under-lying calcrete. The K2mb4 (lower X horizon,indurated, of thefourth buried soil) is a silicifiedcalcrete, probably the Caprock caliche at thetop of the OgallalaFormation.

One exception to the strong pedologic expres-sion in the type section of the Blackwater DrawFormation exists. At the east end of the road-cut (fig. 9; table 2), on the floor of Blackwater

24

Table2.Soil

descriptions,BlackwaterDraw

Formationtype

section(fig.I).*

Profile1**

Depth

Coor

Consistence

Horizon(cm)

Dry

Moist

TextureStructureDryMoist

ReactionBoundary

Remarks

Fill

0-33A

33-505YR3/4

5YR3/3SC

(SCL+)2csbk

f

non

cw

BAt

50-635YR3/45YR3/3SC

(SCL+)lcpr

h

non-secw

2csbk

Btkl63-95

5YR3.5/65YR3/4SCL

2cpr

h

se

cwCommonveryfine

carbonatefilms

5YR7/45YR4/4

2cabk

es

andthreads;manythinclay

films.

(pedfaces

withcarbonate)

Btk295-1275YR3/65YR3.5/4SCL

2cpr

h

non-secw

Fewcarbonatethreads

andfilms;

2cabk

es

manythinclay

films.

Btk3127-149

5YR3/85YR3/6SCL

3cpr

h

non-seaw

Veryfewthreads

andfilms;

common

2cabk

ev

thinclay

films.

Bkl

149-2155YR6/45YR5/6

m

h

ev

gw

(matrix)

StageIII;60%

carbonatebodies

and

7.5YR8/27.5YR7/4

ev

concretions;fewburrows.

(max.carbonate)

Bk2

215-2427.5YR5/85YR5/7L

lcsbk

f

cw

(matrix)

30%carbonate

bodies(nothin

7.5YR8/37.5YR7/4

ev

sections).

(carbonate)

Bk3

242-2907.5YR5/8

5YR5/7L

lcsbk

f

es

gw

Fewerthan20%carbonate

bodies

(matrix)

andconcretions;

groupsofcarbonate

7.5YR8/37.5YR7/4

bodiesand

concretionsoccurin

(carbonate)

distinctzones.

*Abbreviationsfor

softprofiledescriptions:

Texture:S=

sand,SC=

sandyclay,SL=

sandyloam,SCL=

sandyclay

loam,L=loam,C=

clay,Si=

silty,f=fine,and+=

clayey.Structure:Grade:1=

weak,2=

moderate,and3-strong.

Type:sbk=subangidar

blocky,abk=angular

blocky,pr=

prismatic,pi

=platy,m=

massive,sg=single

grain,g=

granular,part=

parting,c=

coarse,andf=Jine.Consistence:

Dry:h=hard,sh=slightly

hard,vh=very

hard,xh=extremely

hard,andso=soft

MoistJ=

friable.Reaction:

(tv/diluteHCl):

non=noncalcareous,se=slightly

effervescent,e=effervescent,es=stronglyeffervescent,andev=violently

effervescentBoundary:

Distinctness:a=abrupt,c=clear,g- gradualondd=diffuse.

Topography:s=smoothw=wavy,i=

irregular.Remarks:

carbonate-calciumcarbonate,

vert.-

vertically,horiz.=

horizontally,cont.=

continuous,max.=

maximum,and

diam.=

diameter.

**NOTE:5-10meastof

titisprofile;

carbonatein

Bk2and

Bk3occursasdistinct

bodies5-10cmverticaland

3-5cm

horizontalBodies

equalin

20-30%of

horizon.

25

Table2.

(cont.)Profile2

Depth

Color

Consistence

Horizon(cm)

Dry

Moist

TextureStructureDryMoist

ReactionBoundary

Remarks

0

depthequivalentto

Bk2,Bk3(180-290

cm)of

Profile1.

Btklbl110-155

2.5YR3/62.5YR3/4SC

3cabkh

e

ci

Max.carbonate

119-121cm;

(matrix)

(SCL+)

w/tonguesofmax.carbonate

5YR8/35YR7/4

m

ev

producingirregular

boundaries;

(carbonate)

StageIII.Carbonateismassive

(samearea);

commonthinclay

films.

Btk2bl155-200

2.5YR3/62.5YR3/4

SC

lmpr

h

e

cw

StageII—III.Carbonate

(50%)as

(matrix)

(SCL+)

5YR8/35YR7/4

2mabk

ev

large(50-70

mm)patchesand

bodies;manyfineclay

films;very

(carbonate)

few1-to2-mm

Mn?patches.

Btk3bl200-220

5YR4/85YR3/6SCL

2cabkh

e

ci

StageII.

Carbonateoccursas

30-50%

(matrix)

(20-50mm)

patchesand

bodies.

5YR8/25YR7/4

ev

(carbonate)

Btkb2220-2952.5YR3/62.5YR3/6

SC

3mabkh

non-seaw

Carbonateoccursasveins

5-15cm

(matrix)

(SCL+)

wideandasmuchas

50cmdeep

5YR8/25YR7/4 (carbonate)

m

fromoverlying

horizons;also

few

subhorizontalveins1cm

thick;mas-

sivecarbonate;manycont.clay

films;few1-to4-mm

dendriticMn?

Profile3

0depth

equivalentto

baseof

Profile2.

Btklb30-275YR5/85YR5/8SCL

lmpr

h

e-escw

(matrix)

2msbk

5YR8/45YR7/4

ev

(carbonate)

Btk2b327-572.5YR4/82.5YR4/8

SCL

lmpr

h

e-escw

(matrix)

2msbk

5YR8/35YR7/4

ev

(carbonate)

Btk3b357-1105YR8/45YR8/4SCL

lmpr

h

e-escs

(matrix)

2msbk

5YR9/15YR7/6

ev

(carbonate)

26

Table2.

(cont.)Profile3

(cont.)

Depth

Color

Consistence

Horizon(cm)

Dry

Moist

TextureStructureDryMoist

ReactionBoundary

Remarks

Btk4b3110-164

5YR5/85YR5/8SCL

lmpr

h

s-es

cs

(matrix)

Imsbk

5YR8/35YR7/4

ev

(carbonate)

Btk5b3164-195

5YR5/85YR5/8SCL

lmpr

h

s-es

gw

(matrix)

Imsbk

5YR8/45YR8/4

ev

(carbonate)

Bktb3195-250

5YR9/17.5YR8/3SCL

m

h

ev

cw

StageIII;only

locallypresent.

(carbonate)

Btb4250-315

5YR4/85YR4/8SCL

lmpr 2sbkh

pedfaces

s

Veryfew

carbonatebodies2.5cm

diam.RareMn

nodulesonped

faces.

pedint.

Thinsection

collected.

none

Profile4

0depthis

probablyequivalentto

Btb4(250cm)of

Profile3.

Mostcarbonatecoatsand

filmsare

onped

faces.

Btklb40-755YR4/85YR3/6SCL

Icpr

h

non-secw

30%carbonate

filmsand

coatings,

(matrix)

fewnodules1-5

cmindiam.StageII.

5YR8/25YR7/3

2cabk

ev

Manytocont.thinclay

filmson

(carbonate)

pedfaces.

Btk2b475-1105YR4/85YR3/6SCL+

2cpr

h

non-secw

20%patchesand

threadscarbonate.

(matrix)

StageI—IIcont.thinclay

films.

5YR8/15YR7/3

3cabk

ev

(carbonate)

Btk3b4110-155

5YR4/85YR3/6SCL+

2cpr

h

non-secw

10%carbonate

filmsonped

faces.

(matrix)

Manythinclay

filmsonped

faces.

5YR8/15YR7/3

2csbk

ev

(carbonate)

Btk4b4155-225

5YR4/85YR3/6SCL

Icpr

h

non-seFewerthan

10%carbonatefilms

2csbk

andthreads

onped

faces.

27

Table2.

(cont.)Profile5

Depth

Color

Consistence

Horizon(cm)

Dry

MoistTextureStructureDryMoist

ReactionBoundary

Remarks

A

0-267.5YR3/4

7.5YR2/3fSL

lmsbk

e

cs

g

so

2mg

BA

26-517.5YR3.5/47.5YR3/4

fSL+lcsbksh

e

cs

Someveryweak

prisms.

Bw

51-757.5YR4/47.5YR3/4

fSL+

lmpr

sh

es

cw

Few1-to2-mm

clastsof

carbonate,

2msbk

probablyslopewash.

Btkl75-1015YR5/65YR4/6SCL

lmsbksh

ev

cw

10%carbonatethreadscommon1-to

3-mmcarbonateclasts;

somewith

coatingof

secondaiycarbonate;

weakStageI.

NOTE:5YR5/6(above]

and5YR4/6{belowlmaybeonethick

horizon.

Btk2101-120

5YR4/65YR4/6SCL

lmsbksh

ev

ci

WeakStageI.10%

carbonatethreads;

(matrix)

common1-to3-mmcarbonate

clasts,

somew/coatingsof

secondary

carbonate.

2Btk3120-155

5YR4/65YR4/6SCL+lmsbk

f*

ev

ci

Manycarbonate

filmsand

threads;

(matrix)

verycommon

pocketsand

lensesof

5YR8/35YR6/4

1-to5-mmcarbonateclasts,com-

(carbonate)

monlycoated

and/orcementedby

secondarycarbonate;

weakStageII.

NOTE:Horizons75-155cmdipto

east(towardBlackwaterDraw).Soil0-155cmisprobably

HoloceneValleyJill.

~LuhbockLake

soil.

3Btkb4155-225

5YR4/85YR3/6SCL+lcpr

firmnon-seaw

BlackwaterDraw

Formation;StageI

(matrix)

carbonate,-20%

films,threads

along

5YR9/15YR8/3

2csbk

ev

pedfaces.

(carbonate)

Klb4225-385

5YR9/15YR8/2

m

ev

ai

Upper±10cmhassomelaminar

structure;common2-to5-mm

carbonateconcretions.

K2mb4385+

OgallalaCaprock?

28

Figure 9. Generalizedsoil-stratigraphic relationships exposedat BlackwaterDrawFormation typesection,Lubbock County, Texas (fig. 8). Profiles described in table 2 are at west end (profile 1), near match line(profiles 2, 3, and 4), and at eastend (profile5).

Draw, the surface soil is weakly developed,exhibiting an A-Bw-Btk profile (A = surfacehorizon of organic matter accumulation; Bw =weak B horizon, subsurface zone of leaching orilluviation, or both; Btk = B horizon contain-ing illuvial clay and carbonate). Some clay filmsare apparent in thin section. Although the huesin this soil are 7.5YR to SYR, the soil is notthought to be as well developed as others in thesection because there are no clay films on ped

faces, and the structure is weak and subangularblocky. On the basis of stratigraphic positionand pedologic expression, this deposit is thoughtto be a middle Holocene valley fill commonlyfound in the draws in the region (Holliday,1985a, b).

As yet, there is no firm age control on thesoils or sediments at the section. Two thermo-luminescence (TL) ages are available: 118±14Ka B.P. (Alpha 1750) from the Btklbl horizon

ft3330

'est

> rAmarillo |series soil < ■(surface soil)

'Ti in'}, t \ ,

jMf iPftWlSTdt'I T f- ■+> r»74 iJ u' r T^f

>oD

llTr7^tTMM?OBTS"' '/T7777TT7T7It I*111

Location of sample for ' ' 'f / / 1 l/Tnthermoluminescence datingbl =118,000 ± 14,000b2 = 270,000

F I :':O

>UJ

3300- 3> If i/i* IFJ7T

'u1)4

3290-

3280- East m-1015

Blackwater Draw - ioio\ 1

-1010

E3 01

e ■til ob2

2 IT JSr I.-..f^TMV-

tL ll 1 DED n Lt

■*■'■—.J n mi 7

r^frrarB^TT -1005 $" I Holocene o

-j valley fill or g_ colluvium ■=riogallala |- jcaprock/ caliche

EXPLANATION ''T^SSoil horizons ''/(

I I Moderately developed ]> Bt

111$ Strongly developed J 0 50 100ft

11 Calcic (± Stage HT)k honzon ,'° \ ' m-'r-'-l Vertical exaggeration 2.5 X-I-I- Petrocalcic (Stage+ H>km horizon

-995

QA 6647

29

Figure 10. View of type section of Blackwater Draw Formation(profile 4), Lubbock County, Texas (fig. 8). Note presence of severalwell-developedburied soils.

(table 2, profile 2) and greater than 270 Ka B.P.(Alpha 1751) from the Btkb2 horizon (table 2,profile 2). Stratigraphic studies from otherlocalities (Gustavson and Holliday, 1985;Holliday, 1990) suggest that these ages arewithin the correct order ofmagnitude of the ageof the respective deposits.

A number of inferences can be made con-cerning the depositional history and soil stra-tigraphy of the Blackwater Draw Formation on

the basis of observations at this section andthe sedimentological data of Seitlheko (1975)discussed in the Introduction (p. 11). TheBlackwater Draw Formation is clearly composedof a number of individual eolian deposits, finingdownwind from southwest to northeast, eachstrongly modified by pedogenesis, but theoriginal thickness and total number of theseunits are difficult to determine. At the type sec-tion there are at least five layers, and at the

30

Figure 11.Ladder structure where CaCO3 nodulesfollow jointsbetweenpeds (McGrath, 1984).

Bushland site, near Amarillo, there are at leastseven layers (Allen and Goss, 1974; Holliday, inpress). Erosion prior to burial of each layer issuggested by thevarying number of buried soilsin each section, the absence of buried Ahorizons, and the presence of unconformablecontacts.

Available data indicate that the generaldepositional model for development of theBlackwater Draw Formation is cyclic. Each cycle,which began with an interval ofeolian deposition

followed by nondeposition, landscape stability,and soil formation, may have ended with aninterval of erosion. Wind has probably been thedominant geomorphic and sedimentologic agentof the region throughout late Cenozoic time,although at any given time wind erosion andsedimentation probably operated concurrentlywith pedogenic processes, as is happening today.During the course of a single cycle, however,different processes dominated from time to time.During depositional periods, material derived

31

from the Pecos Valley would blow onto theHigh Plains at a rate faster than erosion orpedogenesis, resulting in deposition of a moreor less continuous sheet of eolian sedimentacross the area. Sedimentation would then slow,erosionwould remain minimal, and a soil wouldform in the eolian sheet. Enough time wouldelapse to allow formation of a well-developedsoil similar to the surface soil of the area.Erosion by wind deflation would then follow,destroying the lateral continuity of the eoliansediment in many areas. In other places themore easily eroded A horizon would be removeddown to the more resistant Bt horizon. The

erosion would occur immediately before, orperhaps be coeval with, early stages of thesubsequent depositional event. After severalsuch cycles the result would be a stack ofsedimentary units disconformably overlying oneanother, varying in number from one section tothe next, but each unit exhibiting similarpedologic properties. Given the similaritiesbetween the buried soils and surface soil, thepaleoenvironment associated with the buriedlandscapes probably was similar to that ofthe late Quaternary: a generally semiarid en-vironment dominated by grasslands.

32

Stop 2A: Gentry Playa: Origin byHydrologic ProcessesW. R. Osterkamp

Thefloor of a playa-lake basin exposed in Gentry Pit 3 km (2 mi) north ofthe Lubbock airport haspersisted and expanded largely through hydrologic processes, especially by piping and dissolution ofsoil carbonate adjacent to and beneath theplayafloor.

One of the finest cuts exposing near-surfacerocks in the central Southern High Plains is atGentry Pit, about 3 km (2 mi) north ofLubbockInternational Airport and immediately northeastof the intersection of FM Road 1294 andInterstate Highway 27 (figs. 1, 8). Gentry Pit isone of several large borrow pits that suppliedfill from playa areas for construction of Interstate27. The pit is U-shaped inplan viewand thereby

provides exposures of the uppermost OgallalaFormation and overlying rocks along eightdifferent quarry faces in the playa basin. In aregion where topographic relief is low and roadcuts are uncommon, the walls of Gentry Pit(fig. 12) provide (1) exceptional exposures of localgeology and (2) insights into the hydrologic andgeomorphic processes active beneath and adja-cent to playa floors.

Figure 12. Quarryface in centralpart of GentryPit. (A) Randall Clay, (B) Blackwater Draw Formation,(C) OgallalaFormation Caprock caliche (calcrete), and (D) erosionsurface on Caprock caliche.

33

GeologySeveral interpretations of stratigraphy at sites

such as Gentry Pit have been proposed. (Forexample, see the description by V. T. Hollidayof Stop 28, p. 36, this volume.)A section at thesouthwest corner of Gentry Pit measured byC. C. Reeves (personal communication, 1983,1984) contains, in descending order: (1) about1 m (3 ft) ofRandall Clay, a dark organic lacus-trine deposit typical of playa bottoms in thispart of the Southern High Plains, (2) 1 m (3 ft)of eolian sand, probably blown into the playafrom the southwest, (3) about 3 m (10 ft) ofgenerally light colored sand, silt, and clay ofthe TahokaFormation (Evans and Meade, 1945),and (4) about 2.5 m (8 ft) of sand, silt, and clayof the Double Lakes Formation, commonlycemented with carbonates and iron oxides(Reeves, 1976).

Stratigraphers further divided the PleistoceneTahoka and Double Lakes Formations into oneor more members (see summary by Reeves,1976). Most of these divisions were based atleast partly on differentiation of evaporitedepositional environments of playa bottoms orofvariations in geochemical environmentswithinplaya basins. For simplicity, thebeds at GentryPit are here assigned only to the Randall Clayand underlying playa deposits, the BlackwaterDraw Formation, and the Ogallala Formation(fig. 12); lithologic variations within the forma-tions are considered here in terms of inferredhydrologic and geochemical processes.

Randall Clay and UnderlyingPlayaDeposits

The fine-grained, dark organic sediments thatoccupy playa bottoms, including that of Gentryplaya, are mapped as a Vertisol (Udic Pellustert),but are actually Pleistocene to Recent lacustrinefills of the playa depressions (Holliday, 1983,p. 110). Samples collected at playas west andnortheast of Lubbock contained an average of49 percent clay, mostly as montmorillonite andillite and smaller amounts of kaolinite; 23 per-cent silt; and 28 percent sand (Allen and others,1972). Found mostly in the clay-size fraction,organic material near the surface may be asmuch as 5 percent of sample weight. Com-parisons of particle-size distribution and chemi-cal analyses of playa deposits with those ofupland soils (Allen and others, 1972) suggest

that the Randall Clay is derived from localsources by eolian deposition and overland trans-port during storm runoff.

At Gentry Pit the Randall Clay and underly-ing playa deposits (fig. 12) reached a thicknessof about 8 m (26 ft) in the excavated center ofthe playa. Carbon-isotope analyses indicatethat ages of the deposit range from about 1 Kanear the surface to about 10 Ka near the base.Presence of latePleistocene horse and mammothteeth from a leached zone at the base of theplaya deposits (Tahoka equivalent of Evansand Meade, 1945) supports these dates. Pollenanalyses of the deposits (T. A. Ager, U.S. Geolog-ical Survey, personal communication, 1982)suggest relatively persistent dry grasslandconditions. A lack of corrosion on pollen grainsfrom the playa deposits indicates that reducingconditions prevailed through much or all of thelast 10Ka.

BlackwaterDraw Formation

At Gentry Pit and other playas in the area,the Randall Clay and related lacustrine bedsare inset into iron-oxide-stained eolian sandand silt of the Blackwater Draw Formation(Reeves, 1976) that are as much as 27 m (90 ft)thick. At Gentry Pit, exposures of theBlackwaterDraw Formation (fig. 12)range from about 1 to5 m (3 to 16 ft) in thickness, a result of depo-sition on the irregular erosion surface of theunderlying Ogallala Formation. On the basis ofexposures about 100 km (60 mi) north ofLubbock that contain Lava Creek B Ash, thebasal Blackwater Draw Formation seems toexceed 0.6 Ma in age, but the presence of atleast four buried soils containing pedogeniccaliche zones in the type section near GentryPit (fig. 8) suggests that deposition continuedinto the Holocene (Gustavson and Holliday,1985).

OgallalaFormation

The OgallalaFormation, containing the largestaquifer of the Southern High Plains (Knowlesand others, 1982), formed principally during theMiocene from detritus eroded from the South-ern Rocky Mountains. Accumulation of fluvialOgallala sediment ceased following piracy ofmountain runoff by the Pecos and CanadianRivers at about the end of the Miocene(Gustavson and Finley, 1985; Gustavson,

34

Figure 13. Photomicrograph(50x) of BlackwaterDrawFormation sampleshowing microfabrics and linings of manganese oxides within opentubes (pipes?), evidence that these structures are probablypathwaysfor infiltrating ground water. Photographby R. G. Deike.

1986a), but substantial eolian sand and silt inthe upper Ogallala Formation suggest thatlimited deposition may have continued aftercutting by the Pecos and Canadian Rivers. Themassive, 1- to 3-m-thick (3- to 10-ft) OgallalaCaprock caliche (calcrete) (fig. 12, C), which inmost places caps the OgallalaFormation, prob-ably formed during an extended period of land-scape stability after the cutoff of water andsediment from the west.

The Ogallala Formation varies in thicknessfrom about 30 to 150 m (100 to 500 ft) andgenerally fines upward. Calcretes are presentthroughout the formation, those in the lowerpart having possibly resulted from depositionby ground water (Gustavsonand Holliday, 1985)and those in the upperunsaturated part havingformed pedogenically.

HydrologyOn the Southern High Plains most recharge

to the High Plains aquifer (principally theOgallala Formation) occurs by infiltration ofwater ponded in playas; it is chiefly throughhydrologic processes that the floors of playabasins are inferred to persist and expand

(Osterkamp and Wood, 1987; Wood andOsterkamp, 1987). At Gentry Pit the effects ofwater movement can be seen at different scalesof space and time.

Downward movement of water through theunsaturated zone beneath Gentry playa is indi-cated by (1) geochemical zonations in andbeneath the lowermost Randall Clay, (2) micro-fractures in the uppermost Blackwater DrawFormation, and (3) carbonate dissolution in theBlackwater Draw and Ogallala Formations. Thenearly white leached zone at the base of theplaya deposits typically contains less than40 percent clay, as well as iron and manganeseoxides. At the base of the leached zone is 1 to2 cm (0.4 to 0.8 in) of platy iron oxide. In theuppermost Blackwater Draw Formation con-cretions containing large amounts of manga-nese are common, especially at the southwestcorner of Gentry Pit. Petrographic studies ofthe Blackwater Draw Formation (R. G. Deike,U.S. Geological Survey, written communication,1984) show that beneath the edges of GentryPit playa, conduits less than a millimeter (0.04inch) in diameter are probably pathways forinfiltrating ground water. Conduit linings ofmanganese oxides and iron-rich authigenic claysuggest relatively long-term unsaturated-zone

35

movement of ground water through the micro-fractures (fig. 13). Extensive caliche dissolutionis apparent in exposuresof the Caprock calichein north-central Gentry Pit (fig. 12). Near thecenter of the playa, excavation failed to cut anyidentifiable Caprock caliche.

Short-term indications of infiltration fromGentry or other playas that have not beenexcavated include the following: (1) Lack ofevaporites in the Randall Clay and lack of highdissolved-solids content in pondedplaya water.If ponded water did not infiltrate, evaporationwould concentrate salts in the Randall Clay and

lake water; however, none of the small playasin the Lubbock to Amarillo area, includingGentryplaya, exhibit salt buildup. (2) Relativelyrapid water-level declines dwringponding. Whenplayas fill following precipitation, lake levelstypically decline much faster than can beexplained by evaporation alone (Wood andOsterkamp, 1984a, b). (3) Piping. The capacityfor piping is demonstrated by numerous pipesat the walls of Gentry Pit. Natural pipes thatare inferred to transmitwater downward fromthe edges of natural playas have been foundnorthwest ofAmarillo.

36

Stop 2B: Gentry Playa: Origin byGeomorphic ProcessesV. T. Holliday

Erosional contacts between the Blackwater Draw Formation and playa sediments and the lack ofevidence of subsidence indicate that a playa basin exposed in Gentry Pit was formed by surfaceerosion, most likely deflation.

The small shallow basin of an ephemeral lakeor playa, which is exposed inGentry Pit, appearsto be one of the thousands of similar basinsthat dot the Southern High Plains (figs. 1 and8). The origins of these basins have long beenthe subject of debate. Some may be polygenetic,but Reeves (1966) presented a convincing casethat the basins are primarily the result ofwinddeflation. More recently Wood and Osterkamp(1984a, b), Osterkamp and Wood (1987), andOsterkamp (Stop 2A, this guidebook, p. 32)proposed that some of the basins may havebeen caused by eluviation, micropiping, andcarbonate dissolution in the Blackwater Drawand Ogallala Formations.

However, as in any scenario of basin devel-opment, the following field observations mustbe considered: (1) at Gentry Pit and other lakebasins, the Blackwater Draw Formation is notdeformed below the basin; beds are horizontalto subhorizontal; (2) calcic and petrocalcic zoneswithin and below the Blackwater DrawFormation may have been removed or altered,but the sediments and other pedologic featuresshow no evidence of significant deformation;(3) the contact between the lake sediments andthe Blackwater Draw Formation, moreover, isclearly disconformable; and (4) the lake sedi-ments rest in a basin cut into the BlackwaterDraw Formation. Erosion thus seems to havebeen a significant agent in the development ofthe basins, and wind erosion the most likelymechanism.

The playa sediments are the typical clayeydeposits high in organic matter found in mostof the smaller lake basins in the region. Thesoil formed in the deposits is mapped as theRandall Clay, the only Vertisol mapped in thearea (Udic Pellustert). In about the middle ofthe Randall Clay section, on the southwest

(upwind) side of the basin {and exposed in thesouthwest corner of the pit), is a wedge of red-dish, sandy, apparently eolian sediment thatpinches out toward the center of the basin.

Osterkamp (Stop 2A, this guidebook, p. 32)secured radiocarbon ages of about 10 Ka and1 Ka B.P. on organic matter from the lower andupper portions of the Randall Clay, respectively,on the south wall of the pit. An assay of5,730±60 yr B.P. (SMU-1375) is also availableon organic-rich sediments from about the middleof the section, just below the wedge of eoliansand. These dates demonstrate that the basinslowly filled with organic-rich clay throughoutthe Holocene, although a brief interval of eoliansedimentation occurred in the middle Holocene.A similar episode of eolian activity is recordedin draws and dunes in the region (Gile, 1979;Holliday, 1985a).

Older lake sediments containing interbeddedolive-green clay and sand, well-exposed alongthe south wall of the pit, underlie the darkclay.Fragments of mammoth tusk and late Pleis-tocene horse were found in the sand. The olderlake sediments are probably the Tahoka For-mation, judgingfrom their lithology and strat-igraphic position. The assignment of suchstratigraphic terminology can be misleading,however, because olive-hued lacustrine clays arealso abundant in the Pliocene Blanco Formationand lower Pleistocene Tule Formation.

The sediments and soils of the BlackwaterDrawFormation at the north end of the pit aretypical of the region (see Stop 1, p. 22).Postdepositional and postpedogenic alterationsof the Blackwater DrawFormation are apparentunder the playa sediments, however. There issome gleying; manganese nodules are abundant(table3), and thecalcic horizons have undergonesolution and reprecipitation.

37

Table3.Soil

description,GentryPit

(southendof

"peninsula").Seetable2(p.24)for

definitionofsymbols.

Depth

Color

Horizon(cm)

Dry

MoistTextureStructure

ConsistenceReaction

Boundary

Remarks

Ap

0-17

10YR3/1C

lmpl

f

non

cw

0-to94-cm,

moist.

ACl

17-54

10YR3/1C

lmsbk

f

non

awCommon

slickensides.

AC2

54-94

10YR4/2C

lmpr&

f

non

cs

Wettingfrontboundary?

3csbk

AC3

94-12910YR5/210YR4/2

C

3cabk

vh

non

d

AC4

129-16910YR5/210YR4/2

C

lmpr&

xh

non

d

Colorsapproach2.5Y.

3cabk

AC5

169-22610YR5/210YR4/2

C

lmpr&

xh

non

d

Commonslickensides.

3cabk

AC6

226-27910YR5/210YR4/2

C

lmpr&

xh

non

cs

3cabk

Bg

279-309

2.5Y5/2C

2msbk

f

non

cs

2C1

309-3285Y6/25Y6/3

SCL

lmsbk

f

non

aw

part.

2C2

328-3785Y7/35Y6/2

SCL

lmpr

sh

non

aw

Manydendritic,

thinMn-Fecoatsonped

part,to

surfacesinupperthird;

mid.third

com-

2mpl

mon;lowerthird

many(w/metallic

luster).

2C3

378-3805Y7/35Y6/3

SCL

lpl

h

non

aw

3Btgcbl380-4345Y7/35Y6/3

SC

2mpr&

h

non

dw

BlackwaterDraw

Formation;gleyingalong

2mabk

pedsurfacesand

channels;upper12cm

dominatedbyMn-Fe

stainingthroughout

peds;manysplotches

havemetallic

luster—this

grad.deer,w/depth;atabout

30cm

beginpickingup

few1-cm

Mn

concretions(5PB3/1).

3Btgbl434+

5YR5/65YR4/6SCL

2mpr&

h

es

Gleyingalongped

facesand

channels,gen-

(5Y7/2)(5Y6/3)

2msbk

erallyorientedvertically;

fewto

common

coarseredmottlesingleymatrixto

com-

mongleymottlesinred

matrix.

NOTE:0-279cmhave

dryweather

crackfillings;long,

sinuous2-3cmwide;

7.5YR5/6(d),4/6(m);also

commonorganic

coatingsonped

faces&

alongcrack

fillings.

38

Stop 3: Ogallala Formation (Group)Exposed at Janes QuarryD. A. Winkler

Coarse-grained fluvial sediments of the upper Tertiary Ogallala Formation (Group), deposited bybraided streams, subsequently JUled the Slaton paleovalley near Slaton, Texas. These sedimentscontain an early Hemphillian Land Mammal Agefauna.

Janes Quarrycontains evidence of one of themost interesting episodes in the faunal anddepositional record of the Ogallala on theSouthern High Plains (figs. 1 and 14). Earlymapping inYellow House Canyon by Glen Evans(19405, 19505) and Carl Chelf (personal com-munications, 1984) identified a band of gravelsalong the south edge of the canyon east of thecity of Slaton. These sediments were bestexposed in the area now occupied by the JanesGravel Company quarry. Outcrops at JanesQuarry contain interbedded massive and troughcrossbedded sand toboulder gravel at least 18 m

(60 ft) thick (figs. 14 and 15). Many troughs areon the order of 1 m (3.3 ft) high and severalmeters wide. Megaclasts of paleovalley wall rockweighing many tons and as much as 3 m (10 ft)long lie within the gravel deposit (Reeves, 1984a).Evans (1949, 1956) identified two mappableformations within the Ogallala Group inYellowHouse and Blanco Canyons: the CouchFormation and the overlying Bridwell Formation(Winkler, Stop 4, this guidebook, p. 41). Thesediments at Janes Quarrydiffer markedly fromthose in most of the other Ogallala deposits inthese canyons and are not clearly assignable to

Figure 14. Map of Slaton, Texas, area showing Field Trip Stop 3. Derived from Lubbock Sheet, U.S.GeologicalSurvey, (1:250,000 series). See figure 1 for location.

39

Figure 15. Coarse-grained, imbricated gravels of the upper Tertiary Ogallala Formation (Group)exposedat Janes Quarrynear Slaton, Texas. Pencil is 14 cm (5.5 inches) long.

either formation on the basis of lithology.Hydrologic studies have shown that the gravelsat Janes Quarry can be traced for miles in thesubsurface (figs. 4, 16) and pass near the cityof Slaton (Cronin, 1969; Knowles and others,1984). Thefluvial channel fades at Janes Quarryfill a deeply incised sinuous paleovalley termed"the Slaton paleovalley" (Reeves, 1984b; Winkler,1985; Gustavson and Winkler, 1988). Thestratigraphic placement of the valley-fillfaciescannot be clearly determined only by theirsuperposition.

During his initial work in Yellow HouseCanyon, Carl Chelf noted vertebrate fossils inthe gravels and commented that the deposit,though in contact with Triassic rocks, may notrepresent the earliest Ogallala deposits in thearea (Chelf letter on file, 1959, Texas MemorialMuseum, Austin). Work on a new part of thequarry in the late 1970's led to the discovery ofa productive bone bed near the top of the valley-fill deposit. Proctor (1980) described an unusualconcentration of fossils representing a popula-tion of gomphotheres (primitive relatives of

elephants), estimated to number in the hun-dreds. Gomphotheres are most abundant in thebone bed, but the fauna also includes horses{Cormohipparion, Nannippus), camels, and largecarnivores [Epicyon, cat), as well as aquaticturtles (Winkler, 1985). Fossils appear domi-nantly as isolated, rounded bones and teeth ina unit of sandy pebble gravel. The suite ofanimals found at Janes Quarry is restricted tothe early Hemphillian Land Mammal Age (lateMiocene, or 6-9 Ma) (Winkler, 1985). This isthe only confirmed representation of that timein the Yellow House and Blanco Canyon areas(and, in fact, south of Lipscomb County, Texas[Schultz, 1977b]).

The Slaton channel is topographically lowerthan any other Ogallala sediments in YellowHouse Canyon. However, the presence of earlyHemphillian mammals in the deposit, as wellas superposition of reddish, finer grainedBridwell Formation sediments (upper Ogallala)in the channel fill, indicates that this valleyprobably was incised and certainly was filledduring the middle of the time that the Ogallala

40

Figure 16. Structure-contour map of approximate elevation of base of High Plains aquifer for parts ofCrosby, Garza, Lubbock, and Lynn Counties, Texas. From Knowles and others (1982). This surfaceessentiallycoincides with erosional surface that underlies Ogallala Formation. Janes Quarry lies withinSlatonpaleochannel.

was being deposited (Winkler, 1985). Thesediments that the valley is cut through includethe upper Couch Formation, which containsearly Clarendonian Age mammals (10-11 Ma)in Blanco Canyon (Winkler, 1985). Only the topof the Slaton channel fill has produced age-diagnostic fossils, so its base is not directlydated.

The Slaton channel represents a time ofvalleyincision through older Ogallala sediments thatwas followed by vigorous filling and thenabandonment. Such valley cutting contrastssharply with more widespread and continuousaggradation by smaller ephemeral streams and

eolian processes indicated in the rest of theOgallala on the Southern High Plains (Winkler,1985). This unusual geomorphic situation is

reflected in the unusual fauna dominated bygomphotheres. Previous models identified theSlaton channel deposits and two or three otherlarge valleyfills thatcross the Texas Panhandleas deposits of major trunk streams that fedsediment to areas of the High Plains through-out Ogallala deposition (Seni, 1980; Reeves,1984b). Biostratigraphic evidence indicates thatthe Slaton paleovalley was a source of sedimentfor only part of the time during which theOgallalawas deposited.

41

Stop 4: Type Section of the Couch andBridwell Formations (Ogallala Group) atBlanco Canyon, Silver Falls AreaD. A. Winkler

In the Blanco Canyon area the lower Couch Formation, which contains Clarendonian mammalremains, consists of sandy sediments ofJlashy-discharge braided streams. The overlying BridwellFormation, which contains Hemphillian mammal remains, records deposition by flashy-dischargebraided streams and eolian processes.

Ogallala deposits in the area of Blanco andYellow House Canyons received little attentionfrom pioneering geologists working in thePanhandle (figs. 1 and 17). In contrast, thedeposits andfossils of the Blanco beds inBlancoCanyon were described as early as the late1800's (Cope, 1892a, 1893). The first attentiongiven to the Ogallala in this areawas related to

the search for vertebrate fossils. In the early1940's Porter Montgomery and Grayson Meade

from TexasTech University and Glen Evans fromthe Texas Memorial Museum, University ofTexas, Austin, made the first recorded collec-tions of fossils and began stratigraphic work inthe canyon areas. Other collections of fossilswere made for the University of California from

Figure 17. Map of Crosbyton, Texas, area showingField Trip Stops 4 through 6.Derived from Lubbock Sheet, U.S. Geological Survey (1:250,000 series). See figure 1for location.

42

Yellow House Canyon (Johnston and Savage,1955). Carl Chelf also collected fossils fromYellow House Canyon that are now in the TexasMemorial Museum.

Pioneering stratigraphic work on the Ogallalain the canyons was reported by Evans (1949,1956, 1974) in a series of field guides. Frye andLeonard (1957, 1959) measured sections in thearea for their regional work on the Ogallala ofthe Panhandle. Reeves (1972, 1984b) and Seni(1980) described general depositional historiesof the Ogallala including the southern canyonarea. Evans (1949, 1956) proposed that twoformations composed the Ogallala Group inBlanco Canyon—the Couch and Bridwell For-mations (see Winkler, 1985). The type area ofthe two formations was designated along thesouth side of U.S. Highway 82 approximately4 km (2.5 mi) east of Silver Falls in BlancoCanyon (Evans, 1949, 1956). The CouchFormation contains a lower fluvial-dominatedsection in Blanco Canyon and an upper unit ofmassive pink silty sand (fig. 18). The lowerCouch is dominated by greenish gray and buffsands. Only the upper part of the Couch For-mation is found in Yellow House Canyon. TheBridwell Formation is redder in outcrop thanthe Couch because ofdeepred clays intercalatedwith buff sands.

The Ogallala Group in Blanco and YellowHouse Canyons has produced vertebrate fossilsfrom the Clarendonian and Hemphillian LandMammal Ages. The age of the deposits is, there-fore, bracketed between approximately 11 and5 Ma (Winkler, 1985). Like much of the Ogallalain Texas, the fauna was dominated throughoutthat time by large, savanna-adapted animals,especially horses and camels (Schultz, 1977b).

The fluvial sediments of the lower CouchFormation unconformably overlie the TriassicDockum Group in outcrops along the south sideof U.S. 82, 4 km (2.5 mi) east of the Silver Fallscrossing (fig. 18). Clarendonian mammals havebeen found in nearby outcrops of the lowerCouch and appear as isolated, transportedbonesand teeth. The sediments are dominated byhorizontally bedded sand containing subordinate

large-scale trough crossbedding. The lowerCouch represents basal valley fills of flashy-discharge to sandy ephemeral streams.

The upper Couch Formation is clearly visiblealong the south side of U.S. 82 west of SilverFalls. Here the upper Couch consists of aboutllm (36 ft) of massive pink silty sand thatcontains abundant pedogenic carbonate nodules(Winkler, 1985). At the type section a thicklaminar carbonate lies at the top of the upperCouch; however, northward in Blanco Canyon,the carbonate layer is overlain by at least 10more meters of massive pink silty sand.Outcrops along U.S. 82 and farther north alongFM 2591 contain vertebrate skeletons. Many ofthe specimens areisolated, articulated skeletonsthat show signs of desiccation and subaerialweathering before burial. The bedding of theupper Couch, thepresence of carbonate nodules,the fine grain size, and the mode of vertebrate-fossil preservation all support an eolian originfor the unit (Winkler, 1987). Deposition resultedfrom bed-load saltation of sand and suspen-sion transport of finer particles. Thus the unithas characteristics of both loess and eoliansand sheets.

Bridwell Formation sediments overlie theupper Couch on anerosive contact. The Bridwellcontains lenticular packages of horizontallybedded and trough crossbedded sands con-taining armored mud balls. These lenses alter-nate with massive silty sands and red clays.The formation is 51 m (168 ft) thick at the typesection, inclusive of the caprock (Winkler, 1985).Paleosols are common in theBridwell Formation,as shown by carbonate development, and theformation is bounded above by the Caprockcaliche. Remains of Late Hemphillian mammalshave been found at several Bridwell sites inBlanco Canyon, including the roadcut on thenorth side of U.S. 82 on the west descent intothe canyon. The Bridwell Formation recordsalternating episodes of deposition by high-energy, variable-discharge streams and by eolianprocesses. No fossils have been found in theBridwell that are younger than late Miocene(approximately5.0 Ma old).

43

Figure 18. Geologic map of type area of Couch and Bridwell Formations (Ogallala Group) in BlancoCanyon, Texas. From Winkler (1985).

44

Stop 5: Blanco Local Fauna and theBlancan Land Mammal AgeG. E. Schultz

The Blanco Local Fauna of Crosby County, Texas, which is the typefauna of the Blancan LandMammal Age, existed underconditions that are similar to those oftheSouthern High Plains atpresent

The Blanco Local Fauna, named for MountBlanco, a small erosional remnant and locallandmark, is the typefauna of the Blancan LandMammal Age of North America (Wood andothers, 1941) (figs. 1, 17, and 19 through 22;table 4). Most of the vertebrate fossils have come

from deposits exposed in the upper canyon wallson the north side of Crawfish Draw 3.2 km(2 mi) west of its junction with the White Riverand 16 km (10 mi) north of Crosbyton. Thequarries or fossil localities are on the J. S.Bridwell Ranch southwest of the junction of

Figure 19. Map showing locations of Blanco Local Fauna sites and volcanic ash beds, Crosby County,Texas (Field Trip Stop 5). Small x's and circled area indicate known fossil sites; large x's are ash beds.Scale 1:24,000. See figure 1.

45

Figure 20. Mount Blanco, view towardsoutheast. Blanco Canyon and HighPlains surface in distance. CrosbyCounty, Texas.

Figure 21. Blanco Formation, CrosbyCounty, Texas. High Plains surface indistance.

Figure 22. Blanco Formation showingBlanco volcanic ash, Crosby County,Texas. Ash bed (arrow) about 8 m(25 ft) belowGuajeAsh.

46

Table 4. Fauna! list ofBlanco Local Fauna, Crosby County, Texas.

Class ReptiliaOrder Chelonia

Family Testudinidae* Geochelone campester Hay - tortoise* Gopherus pertenuis (Cope) - tortoise

Class Ayes

Order RalliformesFamily Rallidae

** Creccoides osbomii Shufeldt - railClass Mammalia

Order InsectivoraFamily Soricidae

Sorex tayloriHibbard - shrewFamily Talpidae

* Scalopus {Hesperoscalops) blancoensis Dalquest - moleOrder Chiroptera

Family MolossidaeBat near Tadarida

Order EdentataFamily Megalonychidae

* Megalonyx leptostomus Cope - ground slothFamily Mylodontidae

Glossotherium near chapadmalensis Kraglievich - ground slothFamily Glyptodontidae

** Glyptotherium texanum Osborn - glyptodontOrder Rodentia

FamilySciuridaePaenemarmota barbouriHibbard and Schultz - marmotSpermophiliissp. (large) - ground squirrelSpermophilussp. (small) - ground squirrelSpermophiluscf. S. howellt (Hibbard) - ground squirrel

Family GeomyidaeGeomys sp. - pocket gopher

Family HeteromyidaePerognathus cf. P. rexroadensis Hibbard - large pocket mousePerognathuscf. P. pearlettensisHibbard - small pocket mouseProdipodomys cf. P. centralis (Hibbard) - kangaroo rat

Family CricetidaePeromyscus nearkansasensis Hibbard - deer mouseRetthrodontomyssp. - harvest mouseBaiomyssp. - pygmy mouseCalomys {Bensonomys) sp. - neotropicalmouseOnychomys sp. - grasshopper mouseNeotoma cf. N. quadriplicatus(Hibbard) - woodratSigmodonmediusGidley - cotton rat

Order LagomorphaFamily Leporidae

PewelagusdawsonaeWhite - rabbitHypolagus sp. - rabbitSylvilaguscf. S. hibbardiWhite - cottontail rabbit

"Holotypeofgenus

"Holotype ofspecies

Class ReptiliaOrder Chelonia

Family Testudinidae* Geochelone campester Hay - tortoise* Gopherus pertenuis (Cope) - tortoise

Class AvesOrder Ralliformes

Family Rallidae** Creccoides osbomii Shufeldt - rail

Class MammaliaOrder Insectivora

Family SoricidaeSorex tayloriHibbard - shrew

Family Talpidae* Scalopus {Hesperoscalops} blancoensis Dalquest - mole

Order ChiropteraFamily Molossidae

Bat near TadaridaOrder Edentata

Family Megalonychidae* Megalonyx leptostomus Cope - ground sloth

Family MylodontidaeGlossotheriumnear chapadmalensisKraglievich - ground sloth

Family Glyptodontidae** Glyptotherium texanum Osborn - glyptodont

Order RodentiaFamily Sciuridae

Paenemarmota barbouriHibbard and Schultz - marmotSpermophiliissp. (large) - ground squirrelSpermophilussp. (small) - ground squirrelSpermophiliiscf. S. howelli (Hibbard) - ground squirrel

Family GeomyidaeGeomys sp. - pocket gopher

Family HeteromyidaePerognathus cf. P. rexroadensis Hibbard - large pocket mousePerognathuscf. P. pearlettensisHibbard - small pocket mouseProdipodomys cf. P. centralis (Hibbard) - kangaroo rat

Family CricetidaePeromyscus nearkansasensis Hibbard - deer mouseRetthrodontomys sp. - harvest mouseBaiomyssp. - pygmy mouseCalomys {Bensonomys) sp. - neotropicalmouseOnychomys sp. - grasshopper mouseNeotoma cf. N. quadriplicatus(Hibbard) - woodratSigmodonmedius Gidley - cotton rat

Order LagomorphaFamily Leporidae

PewelagusdawsonaeWhite - rabbitHypolagus sp. - rabbitSylvilaguscf. S. hibbardiWhite - cottontail rabbit

47

Table 4. (cont.)

OrderCarnivoraFamily Hyaenidae

?Chasmaporthetesjohnstoni(Stirton and Christian) - hyenaFamily Felidae

?Homotheriumsp. - saber-toothed cat* Felis {Dinofelis) palaeoonca Meade - large cat

Felis cf. F. lacustris Gazin - small catFamily Canidae

** Borophagus diversidens Cope - bone-eating dogCanis lepophagus Johnston - coyote

Family Mustelidae* * Canimartes cumminsii Cope - extinct mustelid

SpilogalerexroadiHibbard - spotted skunkTaxideasp. - badger

Order ProboscideaFamily Gomphotheriidae

Stegomastodon mirificus (Leidy) - short-jawed mastodon* Rhynchotheriwnpraecursor (Cope) - gomphothere mastodon

Order ArtiodactylaFamily Tayassuidae

* Platygonus bicalcaratus Cope (including P. texanus Gidley) - peccary (holotypes)Family Camelidae

* * Blancocamelus meadei Dalquest - long-legged camelCamelopscf. C. traviswhiteiMooser andDalquest - camel

* Gigantocamelus spatulus (Cope) - giant camel* Hemiauchenia blancoensis (Meade) - llama

Family CervidaeOdocoileus cf. O. brachyodontus Oelrich - deer

Family AntilocapridaeAntilocaprid sp. - pronghorn

Order PerissodactylaFamilyEquidae

* Nannippusphlegon (Hay) - small 3-toed horse* Equus {Dolvchohippus) simplicidens (Cope) - zebrine horse* Equus {Asinus) cwnminsiCope - small asslike horse

FM 651 and FM 193 in Blk. 3, Eastland C.S.L.(Capital School Lands) Survey No. 1, CrosbyCounty, Texas (U.S. Geological Survey[USGS], Floydada S.E. 7.5-minute topographicquadrangle) (fig. 19). Two other fossil sites areon the R. B. Smith Ranch on the slopes of thefirst reentrant north of FM 193 (same topo-graphic map). Another exposure of Blancodeposits, somewhat smaller and less fos-siliferous, lies 13 km (8 mi) to the southeast onthe east side of White River Canyon about

9.7 km (6 mi) northeast of Crosbyton (USGSCrosbyton 7.5-minute quadrangle). No dis-cernible stratigraphic tie exists between depositsin this area and those on the Bridwell Ranch.Meade (1945, p. 519) gives more detailed loca-tions for these fossil quarry sites, although hismap (Meade, 1945, p. 510) is in error. The maingroup of quarries is actually about 0.4 km(0.25 mi) west of their plotted positions on hismap. These locations have been corrected on amap by Dalquest (1975, p. 8).

OrderCarnivoraFamily Hyaenidae

?Chasmaporthetesjohnstoni(Stirton and Christian) - hyenaFamily Felidae

?Homotheriumsp. - saber-toothed cat* Felis {Dinqfelis) palaeoonca Meade - large cat

Felis cf. F. lacustrisGazin - small catFamily Canidae

** Borophagus diversidens Cope - bone-eating dogCanis lepophagus Johnston - coyote

Family Mustelidae** Canimartes cwnminsii Cope - extinct mustelid

Spilogale rexroadiHibbard - spotted skunkTaxideasp. - badger

OrderProboscideaFamily Gomphotheriidae

Stegomastodon mirificus (Leidy) - short-jawed mastodon* Rhynchotheriumpraecursor (Cope) - gomphothere mastodon

Order ArtiodactylaFamily Tayassuidae

* Platygonus bicalcaratus Cope (including P. texanus Gidley) - peccary (holotypes)Family Camelidae

** Blancocamelus meadeiDalquest - long-legged camelCamelopscf. C. traviswhiteiMooser and Dalquest - camel

* Gigantocamelus spatulus (Cope) - giant camel* Hemiauchenia blancoensis (Meade) - llama

Family CervidaeOdocoileus cf. O. brachyodontus Oelrich - deer

Family AntilocapridaeAntilocaprid sp. - pronghorn

Order PerissodactylaFamily Equidae

* Nannippusphlegon (Hay) - small 3-toed horse* Equus {Dolvchohippus) simplicidens (Cope) - zebrine horse* Equus {Asinus) cwnminsi Cope - small asslike horse

48

GeologyAccording to Evans and Meade (1945), the

Blanco deposits are a localized basin accumu-lation and are predominantly of lacustrine origin,although a fluviatile origin has been advocatedby Gidley (1903a), Matthew (1924a), and Fryeand Leonard (1957). The best exposures of thesewhite beds are along the upper walls of WhiteRiver Canyon (Blanco Canyon) and CrawfishDraw for a distance of about 4 km (2.5 mi),where they unconformably overlie the reddish-brown sands and clays of theBridwell Formation(locally defined equivalent of the upper part ofthe Ogallala Group). The Blanco Formation isin turn overlain by eolian sands, silts, andcaliche of the Blackwater Draw FormationQuaternary age (Reeves, 1976).

Evans and Meade (1945, p. 491) stated that"theBlanco beds consist mainly ofwell-bedded,light gray, calcareous sands and clays with somefresh-water limestones, tufa, diatomite, andcoarse gravels. Thefiner-grained materials makeup the main body of the deposits but grademarginally to coarser sand and gravel." Theydescribed the following section, located 1,067m(3,500 ft) south of FM 193 and near the mouthof Crawfish Draw: fi,«~ir«««Thickness

in feet10 . Bentonitic clay, greenish gray,

sandy in upper part 10.09. Sands, gray to light greenish gray,

containing calcareous nodules 4.7

8. Diatomaceous earth, light gray;varies in thickness from 1 foot tomore than 5 feet at this section 1.0

7. Bentonitic clay, sandy 9.46. Caliche, gray, jointed 6.85. Bentonitic clay, calcareous and

sandy 6.2

4. Fresh-water limestone, thinflaggy beds, reeflike tufa masseslocally present 6.0

3. Clay, gray, calcareous 2.0

2. Sand, light greenish gray,massive 12.5

1. Clay, light tan to greenish 2.060.6

In this and six other sections measured atintervals over an outcrop distance of about2.4 km (1.5 mi), Evans and Meade identified10 to 12 beds and noted a range in thickness of

17 to 22 m (56 to 74 ft) for the Blanco sequence.Changes in thickness and facies of individualbeds are visible along the outcrop.

Recent geological studies of the BlancoFormation by Pierce (1974) detailed clay,carbonate, and silicate mineralogy by X-raydiffraction and use of thin sections, along withsupplementary textural analysis of insolubleresidues. Pollen, diatoms, and invertebrates werealso studied. Pierce found that near the centerof the basin, the Blanco beds mostly containvery fine sand, primary dolomite or dolostone,and magnesium-rich clays (attapulgite andsepiolite)and only small amounts of sheetwashgravel. Near the margin of the basin, limestoneand coarser elastics, including caliche graveland cobbles in arroyo fans, are found, whereasdolostone and magnesium-rich clays becomerarer. Pierce also discovered that the BlancoAsh (Izett and others, 1972; Boellstorff, 1976)(fig. 22), which is restricted to the northwestpart of the basin, can be traced laterally intothe prominent diatomite unit that overlies someof the main fossiliferous strata in the lowerpartof the formation. This diatomite unit and itslateral facies equivalent, a dense, laminated lime-stone, provide a useful marker bed throughoutthe west part of the basin, where they form aboundary between dolomitic carbonates belowand highly contorted laminated calcitic carbon-ates above. Pierce noted a disconformitybetweenthese laminated caliches and the overlying eoliancover sands, which contain the Guaje Ash (Izettand others, 1972) that is exposed in the roadcutofFM 193 (fig. 23).

The vertebrate fauna reported by Dalquest(1975) and earlier workers is dominated by graz-ing herbivores such as glyptodonts, gomphotheremastodons, camels, antilocaprids, and horses,although some browsers are represented, includ-ing ground sloths and deer. Peccary probablyrequired some brush or woodland cover, whichmay have grown along streams and ponds andin shaded valleys. Aquatic vertebrate remainsare absent, with the exception of one alligatortooth. Rodents include pocket mice, kangaroorats, ground squirrels, cotton rats, andgophers—indicating semiarid grassland habitats.No arvicoline rodents are present. Dalquest(1975, p. 46) concluded that "the Blanco localfauna represents one rather uniform habitat:grassy plains with narrow belts of trees fringingwatercourses and in the shaded parts ofvalleys.Conditions were almost identical to those of theHigh Plains and Texas Panhandle today wherenot modified by agriculture."

49

Figure23. View of BlackwaterDraw Formation (BD) overlyingBlanco Formation (B) at type sectionof Blanco Formation. The 1.4-Ma-oldGuaje volcanic ash (V) is underlainby approximately 1 m (3 ft)of BlackwaterDraw Formation sediments.

History of Fossil CollectingA number of institutions have collected from

the Blanco beds, and many new species havebeen described (table 4). The first specimens,now at the Texas Memorial Museum, The Uni-versity of Texas at Austin, were described byCope (1892a, b, c, d, c, f, g; 1893). They includethe type specimens of a land tortoise, a groundsloth, a bone-crushing dog, a small mustelid, amastodon, a peccary, a giant camel, and twohorses. The American Museum of Natural His-tory expeditions under Gidley obtained addi-tional material, including a nearly completecarapace of Glyptotherium texanum described byOsborn (1903) and restudied by Gillette andRay (1981) and a peccary, Platygonus texanus,described by Gidley (1903b) but later syn-onymized with P. bicalcaratus Cope (Hibbard andRiggs, 1949, p. 843).

Most of the fossil material consists of isolatedbones, teeth, and jaws that are commonly frag-mentary. Notable exceptions include the glypto-dont carapace just mentioned, as well as twopartial skeletons of the zebrine horse Equus{Dolichohippus) sunpUcidens (formerly Plesippus)collected from awhite clay bed by Matthew andSimpson for the American Museum in 1924(Matthew, 1924c, 1926; Simpson, 1951). Thesmall 3-toed horse, Nannippusphlegon, is knownfrom articulated leg bones as well as from partialskulls, lower jaws, and teeth (Dalquest andDonovan, 1973; MacFadden and Waldrop, 1980;MacFadden, 1984a). Nannippus phlegon appar-ently was a highly cursorial, antelopelike grazer.

During the early 19405, Meade collected arepresentative sample of the fauna for the Uni-versity ofTexas, Austin (Meade, 1945). Of inter-est are the type skull and jaws of a large cat,Felis {Panthera) polaeoonca, which Meade con-

50

sidered to be a jaguar but which Kurten (1972)assigned to the Old World genus Dinofelis. Ofinterest, too, are the remains of about 18 indi-viduals of the giant camel, Gigantocamelusspatulus, which Meade collected from onequarry. Although no articulated skeletons werefound, therewere several articulated skulls andjaws and a number of articulated leg bones.According to Meade (1945, p. 514), these fossilsmay represent a herd of camels that venturedinto the shallow waters of an ancient lake andwere trapped or were overcome by carnivoresat the edge of the water. Gigantocamelus hasbeen reviewed recently by Breyer (1976) andHarrison (1985). Meade also described a newspecies of llamalike camel, Tanupolama blan-coensis, now assigned to the genus Hemiau-chenia (Webb, 1974; Breyer, 1977, 1983). Andhe collected a jawfragment of the giant groundsquirrel, Paenemarmota, later described byHibbard (1950, p. 137) and Repenning (1962).An incisor of this rodent was misidentified byMeade (1945) as that of a beaver, Procastoroid.es.There is no beaver in the Blanco Fauna.

Errors in identification of taxaand much con-troversy and speculation have occurred, in part,because some of Cope's type specimens werelost for a time. A proper understanding of thenature ofBorophagus, for example, was not pos-sible until the type of B. diversidens was relo-cated (VanderHoof, 1936) and a complete skullwas found and described by Dalquest (1969a).Of note also is the varied treatment given themastodons, which include the rather commonshort-jawed Stegomastodon, which lacks lowertusks, and the much less common lower tuskedmastodons assigned to various genera includ-ing (currently) Rhynchotherium (Osborn, 1923,1924, 1936; Savage, 1955b). Another problem

concerns the proper identification of the severalcamels present and the correct association be-tween limb and foot elements and dentitions.Dalquest (1969a, 1975) dealt admirably withthese and other problems. For example, hecoined the genus Blancocamelus for the large,long, slender metapodials to which Meade hadapplied the name Leptotylopus percelsus—anomen nudum borrowed from an unpublishedmanuscript by Matthew. Meade was not awarethat Matthewhad intended the name for a smallspecies of camel now recognized as Hemiau-chenia blancoensis. Blancocamelus was reviewedby Harrison (1985).

The most recent additions to the Blanco LocalFauna are the microvertebrates collected by

Dalquest (1975) from several quarry sites. Thesefossils, though few in number, include a shrew,a mole, a bat, tworabbits, and a variety of ro-dents. The rodents are primarily grasslandprairie forms such as gophers, kangaroo rats,pocket mice, ground squirrels, cotton rats, andother cricetines. Arvlcoline rodents, beavers,otters, fish, amphibians, small pond turtles,and other forms indicative of aquatic or moistenvironments are absent except for a singletooth ofa large alligator. Turtles are representedonly by the large land tortoise, Geochelone.

Dalquest placed most of his collection in themuseum at Texas Tech University in Lubbock,which also has some of the material describedby Meade. There is also a small collection atWest Texas State University and one in thePanhandle-Plains Historical Museum in Canyon.

Age of the Blanco FaunaThe Blanco beds disconformably overlie

deposits of the Ogallala (Bridwell) Formation,which locally have produced late Hemphillianfossils, and they are disconformably overlainby unfossiliferous eolian silts and sands ofthe Quaternary Blackwater Draw Formation.The age of the Blanco Local Fauna has beenbased mainly on the evidence of the fossil verte-brates supplemented more recently by studiesof volcanic ash petrography and magneticstratigraphy.

The fauna is a mixture of typical Blancangenera such as Borophagus, Stegomastodon,Gigantocamelus, and Dolichohippus, as well aslonger ranging genera such as Camelops, Platy-gonus, and Hemiauchenia, which survivedthrough most or all of the Pleistocene, and alsoa few carryovers from the Hemphillian such asNannippus, Rhynchotherium, and Hemiauchenia(table 4). Earlyworkers such as Gidley, Matthew,and Osborn assigned a Pliocene age to thefauna.Meade (1945) identified typical Pleistocenegenera and assigned an early Pleistocene age tothe fauna. Meade's conclusion, along withevidence that the deposits presumably formedin a humid climate (probably during a glacialstage), indicated to Evans and Meade (1945)that the Blanco beds were of Nebraskanage.

The apparent absence of a molluscan faunain the Blanco led Hibbard (1958) to concludethat the age of the fauna was Aftonian inter-glacial because, in his experience, faunas thatlived insouthwest Kansas during glacial periods

51

under moist climatic conditions commonlyincluded abundant mollusks. Frye and Leonard(1957) accepted a Nebraskanage for the BlancoLocal Fauna but ascribed the absence of mol-lusks as well as fish, amphibians, and aquaticturtles to an unstable streamregimen.

Meade (1945, p. 516-519) argued that notonly the Blanco Local Fauna, but Blancanfaunas in general, were of early Pleistocene age.Later authors, for a time, thought the BlancanAge had spanned the late Pliocene through theearly Pleistocene. They accepted Meade's assign-ment of an early Pleistocene age for the BlancoLocal Fauna, but not, as he had intended, forall Blancan faunas (Dalquest, 1975, p. 46).

Recent studies indicate that warm Blancanfaunas such as the Sand Draw Local Fauna ofNebraska (Skinner and others, 1972) and thosefrom southwest Kansas studied by Hibbard,which were once thought to be interglacial, areof pre-Nebraskan age. Thus, the current con-sensus is to return the Blancan wholly to thePliocene, which, according to current datingtechniques, probably extended from about 5 Maago to less than 2 Ma ago.

Although precise zoning of faunas within theBlancan probably is not attainable on faunalevidence alone, most workers think the BlancoLocal Fauna is a late Blancan fauna, consider-ably younger than the Rexroad Fauna ofKansasor the Hagerman Fauna of Idaho and moreclosely related to the Red Light and Cita CanyonFaunas of Texas. This age assignment is sup-ported by the presence in all three faunas ofthe ground sloth Glossotherium and theglyptodont Glyptotherium, both ofwhich are lateBlancan immigrants from South America (seeLundelius and others, 1987, for correlationchart). Dalquest (1975, p. 46) noted that "theabsence of microtine (arvicoline) rodents andaquatic mammals from the Blanco makes cor-relation with otherBlancan local faunas difficult,for most known Blancan local faunas are frommore northern areas, where microtines areabundant and beavers and otter are present."He assigned an early Blancan age to theBlancoLocal Fauna, however, and stressed the simi-larity between it and the Rexroad Fauna ofKansas, yet recognized that Hesperoscalops andStegomastodon are represented in each faunaby different species. Savage (1955b) thought theRexroad Stegomastodon was more primitive thanS. mirificiLs from Blanco and Cita Canyon. TheBlanco mole, on the other hand, may or maynotbe more primitive than the Rexroad species.

A 30-cm-thick (1-ft) volcanic ashbed exposedin the roadcut just northwest of Mount Blancohas been dated at 1.4±0.2 Ma using the fission-track method on glass shards and has beencorrelated with the Guaje Pumice Bed of theJemez Mountains,New Mexico (Izettand others,1972; Izett, 1981). This ash bed, however, liesnear the surface in the upper part of theBlackwater Draw Formation that disconformablyoverlies theBlanco Formation (Holliday, Stop 6,fig. 23, this guidebook, p. 52; Holliday, 1988).The ash is separated from the lower fossiliferouspart of the Blanco Formation by 9 m (30 ft) ormore of partly calichified strata. The Guaje Ashthus furnishes a minimum date for the under-lying Blanco Formation and, hence, for theBlanco Local Fauna.

Another ash bed, the Blanco Ash, is about10 cm (4 inches) thick and lies about 7.5 m(25 ft) below the Guaje Ash; both ashes areexposed in the first large reentrant south ofFM 193 justwest of Mount Blanco (fig. 22). Theuraniumcontent of the Blanco Ash is too low topermit fission-track dating by means ofzircons(G. A. Izett, personal communication, 1976), butBoellstorff (1976, p. 65) obtained a glass shardfission-track date of 2.8±0.3 Ma for this ash.Boellstorff (1976, p. 57) obtained a date of1.77±0.44 Mafor the Guaje Ash using the samemethod. The Blanco Ash overlies the fossil-bearing unit of the Blanco Formation and thussuggests an age in excess of 2.8 Ma for theBlanco Local Fauna.

Lindsay and others (1975, p. 114) determinedfrom paleomagnetic studies that the entireMount Blanco section, including both ash beds,is reversely magnetized. The 1.4-Ma age of theGuaje Ash and the absence of a normal magneticpolarity zone beneath the ash in the Blancosection indicated to them that the Blanco LocalFauna must appear in the lower Matuyama(reversed) magnetic chron, which dates between1.4 and 2.4 Ma inage.

Additional references to the geology or faunaat Mount Blanco may be found in Gidley (1901,1907), Hay (1908), Osborn (1918). Matthew(1925), Matthew and Stirton (1930a, b), Stirtonand VanderHoof (1933), Stirton (1936a), Gazin(1937), VanderHoof(1937), Evans (1949, 1956),Johnston and Savage (1955), Auffenberg(1962b), Webb (1965), Hirschfeld and Webb(1968), Schultz (1977a, c), Richey (1979), Kurtenand Anderson (1980), Holliday (1988), andHolliday (Stop 6, this guidebook, p. 52).

52

Stop 6: Age of the Lower Blackwater DrawFormation at Blanco CanyonCanyonV: T. Holliday

The 1.4-Ma-old Guaje Ash is interbedded with sediments of the lowerBlackwater Draw FormationatBlanco Canyon. A buried soil in the Blackwater Draw Formation separates the Guqje Ashfrom theunderlying Pliocene Blanco Formation.

In north Crosby County the BlackwaterDraw Formation is exposed on the west side ofBlanco Canyon in a roadcut of FM 193, about1.2 km (0.8 mi) west of the intersection with

FM 651 (figs. 1, 17). The Blackwater Draw For-mation is about 5 m (17 ft) thick and rests onthe lacustrine sediments of the Blanco Forma-tion. The 1.4-Ma-old Guaje Ash, derived fromthe Jemez volcanic field in New Mexico (Izettand others, 1972), is exposed about 4 m (13 ft)below the surface "within sediments of theBlackwater Draw Formation (Holliday, 1988)(fig. 23).

The Blanco Formation comprises the lower4 m (13 ft) of the section exposed in the roadcut(fig. 24). Locally, the Blanco Formation is asmuch as 14 m (46 ft) thick, and near the centerof the ancient Blanco basin the unit is as much

as 27 m (90 ft) thick (Pierce, 1973). In the road-cut, the upper Blanco Formation is a highlycontorted olive clay that has common verticaland horizontal joints. The sediments are foldedinto a series of broad anticlines and synclines.Within the trough of each downwarp is a pocketofreddish sand as much as 1 m (3 ft) thick.

A subhorizontal, strongly developed pedogeniccalcrete (Km horizon) has formed across the topsof the upfolds in the Blanco clay and across thetops of the pockets of reddish sand (table 5).The calcrete is apparent at the top of the BlancoFormation throughout the area. TheKm horizonis as much as 1 m (3 ft) thick, is locally pisolitic,and has sporadic thin carbonate laminae at thetop. This calcrete is, therefore, a Stage IV calcichorizon (Gile and others, 1966), probably relatedto a soil formed in the overlying sediments.

Figure 24. Schematic composite drawing of upper Cenozoic strata exposed at Blanco Formation typesection (not to scale) and generalized soil stratigraphy. Detailed soil descriptions given in table 5; symbolsidentified in figure 9. See figure 17 for location.

53

The entire section above the calcrete isthought to be the Blackwater Draw Formationbecause it is a reddish-brown sandy depositdisconformably overlying theBlanco Formation,as described by Frye and Leonard (1957) andReeves (1976). Furthermore, it is identical strat-igraphically, lithologically, and pedologically tothe type section of the Blackwater Draw For-mation (Holliday,Stop 1, this guidebook, p. 22).

The Blackwater Draw Formation at MountBlanco contains three buried soils (bl, b2, b3,top to bottom) plus the present surface soil,and it can be subdivided using the soils andthe Guaje Ash. The ash lies about 1 m (3 ft)above the base of the Blackwater Draw For-mation. Below the ash is the lowermost buriedsoil (b3), which lies below the ash in many otherexposures in the area. The soil includes a Bthorizon exhibiting SYR hues, well-expressedprismatic to subangular-blocky structure, andthe previously described Km horizon formed atthe top of the Blanco Formation (table 5). In theBt horizon films of illuvial clay are common onped (an individual aggregate of soil) faces andare common in thin section as coats on quartzsand grains and the walls of voids (table 5).Opaque material, probably illuvial opal, is com-mon in thin section. Silica derived from weather-ing of overlying ash was probably translocatedinto theBt horizon.

The ash zone includes a layer of pure ash asmuch as 30 cm (1 ft) thick overlying a zone ofmixed ash and sand as much as 50 cm (1.6 ft)thick. The ash rests disconformably on the b3soil. The thickness of the ash layer varies con-siderably throughout the areaand is absent atthe west end of the roadcut.

Above the ash are two buried soils (bl, b2)and the present surface soil. The number andcontinuity of buried soils in the Mount Blancoarea are unknown. The surface soil (not de-

scribed) at the west end of the roadcut, awayfrom the edge of Blanco Canyon, is typical ofthe strongly developed surface soil of the region,having a Bt-K or Btk profile and being classifiedas a Paleustalf. The Bt horizon is about 1 m(3 ft) thick, exhibiting SYR hues, a prismatic tosubangular-blocky structure, and clay filmscommon on ped faces. Illuvial clay is also com-mon in thin section, clay films coating quartzsand grains. The upper portion of the zone ofcarbonate accumulation is a laminar X horizon(X [lam]) about 10 cm (4 inches) thick. Belowthe X horizon is a Btk horizon with ladder-matrixmorphology (fig. 11). The K-Btk horizoncrops out as a ledge at the east end of the road-cut (fig. 23) where erosion along the walls ofBlanco Canyon have removed the upper part ofthe profile.

The two buried soils above the ash are eachabout 1.2 m (4 ft) thick and contain Bt hori-zons having morphologies identical to that ofthe surface soil (table 5). The bl soil also has aladder-matrix Btk horizon, which appears tohave formed in the upper part of the b2 soil.The b2 soil has a Stage 111-IV X horizon formedjust above the zone of pure Guaje Ash. Theparent material for the X horizon may have con-tained some reworked ash, judgingfrom its lowbulk density, fine sand texture,and the gradualboundary between the X horizon and the ashlayer. Both carbonate horizons crop out asledgesat the east end of the roadcut.

This section has clearly shown that eolianaccretion of the Blackwater Draw Formationbegan before 1.4 Ma ago and was episodicthroughout the Quaternary, as indicated at thetype section (Holliday, Stop 1, this guidebook,p. 22). As also indicated at the type section, themorphologies of the buried soils are similar tothat of the surface soil and are therefore indic-ative of a generally semiarid grassland.

54

Table5.Soil

descriptions,Blanco

Formationtype

sectionnearMount

Blanco(figs.1,10).Seetable2(p.24)

fordefinitionofsymbols.

Profile1

Depth

Color

Consistence

Horizon(cm)

Dry

MoistTextureStructureDryMoist

ReactionBoundary

Remarks

A&BO-257.5YR4/4

7.5YR3/4SCL

lcpr&

aw

Holocene?Remnant

ofAmarillolike

soil?

2msbk

Undivided;thinA

(fewcm).

K(lam)25-35

5YR8/25YR7/3

m

xh

ev

awLaminar

zone.

K

35-855YR8/45YR7/5

m

h

ev

cs

StageIII;common,veryhardcarbonate

segregationsasmuchas3

mmdiam.

Btk

85-1025YR6/45YR6/6SCLm

sh

ev(k)

cw

StageII—III;commonthreads,bodies,&

hardcarbonateconcretions.

Btklbl102-159

5YR5/65YR4/6SCLlfsbksh

ev(k)

awCommon

areasasmuchas15cmwideof

softcarbonate

andhard

carbonatebodies;

fewMn

splotcheson

carbonate;colors

for

Bt;BthasfewMn

splotches,commonthick

clayfilms;

structuredisruptedby

areasof

carbonate.

Btk2bl159-195+

5YR5/65YR4/6SCLlfsbksh

ev(k)

Thishorizonisverydistinctiveasit

weathers,forminga

"calichebench"in

outcrop;inthis

sectionitis2d

benchdown

(lst=K);commonveryhardcarbonate

bodiesasmuchas15cmwide;

fewMn

patches.

Profile2

0-70

Thisis

equalto

beveled-offBtk2bl.

Bkbl70-120

5YR8/25YR7/4

m

vh

ev(k)

cw5YR8/2

=ped

interiors;5YR8/3=

exteriors;

5YR8/35YR7/4

onweathering

zonefracturesin

vertical

sectionsasmuchasseveralcminwidth&

NOTE:"ev(k)"indicates

reactionof

carbonatebodies;

matrixis

otherwisenoncalcareous.

blocksasmuchasseveralcmin

height;

almostplaty;

commonMnpatches;Bt

materialfew

mmwideand

fewcm

high.

55

Table5.

(cont.)Profile3

Depth

Color

Consistence

Horizon(cm)

Dry

MoistTextureStructureDryMoist

ReactionBoundary

Remarks

Btklb2120-180

5YR8/25YR7/4

m

vh

ev(k)

cw

VerysimilartoBkb1;

carbonatebodies

are

5YR8/35YR7/4

elongate,several

cmwide,spaced

5-10cmapart;

carbonateweathering

intoveryhard

"pillars"common,thick

clayfilms.

Btk2b2180-240

5YR8/25YR7/4

m

vh

ev(k)

cwAs

above;fewer

clayfilms.

Kb2

5YR8/35YR7/4

MassiveStageIII—IV

w/nolaminar

zone;

well-expressedtoleft(E)of

Profile2;as

muchas

50cmthick.

2Clb2

N8

N8

mpl

vh

nonawCleanash

(Guaje);0-30cmthick.

3C2b20-205YR8/45YR7/6

m

vh

e

awReworked

ash;asmuchas

50cm

thick;

fewMn

patches.

3Btklb320-40

5YR7/45YR6/6

fSCLlfpr&

vh

ev(k)

cs

Carbonatebodies

asmuchas1cmthick

3msbk

formedalongvert,and

horiz.ped

faces=

"ladderstructure."

3Btk2b320-100

5YR6/65YR5/8

fSCL2fpr&vh

ev(k)

awLowerburied

soil?Thickness

varies— 3msbk

locallyasmuchas1

cm;carbonateas

coatsonped

faces;some"ladder

structures."

3Kmb3

7.5YR8/17.5YR6.5/3

xh

cwMassiveStageIV;asmuchas1m

thick;

locallyseeeffectsofdissolution;

formedin

Blancoclayand

locallypinksand

(3Ckb3).

3Ckb3

5YR8/25YR6/4S

m

xh

ev

awFoundin

troughsof

foldedBlanco

clay;

locallyasmuchas1m

thick.

4Rb3

N9

5YR8/1C

m

xh

ev

BlancoFormation;

secondarycarbonate

locallycommon;highlycontorted;

considerableverticaland

horizontal

jointing.

56

Stop 7: Age of the Blackwater DrawFormation Exposed at Tule Creek, TexasPanhandleV. T. Holliday

Eolian sediments of the Blackwater Draw Formation exposed along Tide Creek in east SwisherCounty, Texas, are interbeddedwith the 0.62-Ma-old Lava CreekB volcanic ash.

Another exposure of the Blackwater DrawFormation lies in Swisher County, 19km (12 mi)east-southeast of Tulia, on the south side ofTule Canyon (figs. 1, 25). The locality is in aroadcut of FM 2301, 2 km (1.2 mi) north ofState Highway 86. In the exposure are fine-grained eolian sediments containing the 0.62-Ma-old Lava CreekB (=Pearlette Type O) volcanicash (Izett and Wilcox, 1982), which is overlainby lacustrine sediments of the Tule Formation.The eolian sediments containing the ash areBlackwater Draw Formation (fig. 26) because,by definition, the Blackwater Draw Formationincludes eolian sediments overlying the TuleFormation (Frye and Leonard, 1957; Reeves,1976).

The Blackwater Draw Formation is morethan 4 m (13 ft) thick in this exposure (table 6,fig. 27). The upper 1.47 m (4.9 ft) of the sectioncontains the well-developed modern surface soilexhibiting A-Bt-Bk horizons, reddish-brown

(7.5YR) hues, a moderate structural develop-ment, and a Stage 111 calcic horizon. From 67 to147 cm (2.2 to 4.9 ft) (Btk2 horizon) there iswell-expressed Bt material below the calcichorizon at 40 to 67 cm (1.3 to 2.2 ft) (Btkl hori-zon), suggesting either aburied soil ora formerlydeeper surface profile. Soil development in the170- to 275-cm (5.6- to 9.2-ft) zone, relatedeither to the surface soil or to thepossibly buriedsoil noted previously, occurred in material thatprobably contained abundant volcanic ash. Thisis indicated by low bulk density, massivestructure, and some silica coatings. The zone ofpure ash underlies the soil and varies in thick-ness from a feather edge to about 30 cm (1 ft).Theash buried about 90 cm (3 ft) of BlackwaterDraw Formation, which also has a well-developed soil exhibiting a Bt horizon, 7.5YRhues, moderate structural development, and athin Stage IV calcic horizon (table 6).

Figure 25. Map of Silverton, Texas, area showing Field Trip Stops 7 through 9. Derived from PlainviewSheet, U.S. Geological Survey (1:250,000 series). See figure 1 for location.

57

Figure 26. View of Quaternary Blackwater Draw (B) and Tule (T) Formations. See figure 25 forlocation. In this exposure BlackwaterDraw Formation contains 0.62-Ma-old Lava Creek B volcanicash (L) and overliesTule Formation. (Scale bar = 1 m.)

Figure 27. Schematic drawing showing soil-stratigraphic relationships of BlackwaterDraw and Tule Formations in a roadcut onthe east side of State Highway2301 south ofTule Creek, SwisherCounty, Texas.

58

Table6.Soil

descriptions,Tule

Basintype

section(fig.1).Seetable2(p.24)for

definitionofsymbols.

Profile1

Depth

Color

Consistence

Horizon(cm)

Dry

MoistTextureStructureDryMoist

ReactionBoundary

Remarks

A

0-17

7.5YR5/37.5YR3/3SiCLlmsbksh

es

cs

10-20%granules

arepinkishincolorasif

3fgr

broughtup

fromtheBhorizon.

(Bioturbation?)

B/A

17-407.5YR6/37.5YR4.5/4SiClmsbksh

es

cs

Veryweak

prismsevident;granulesseemto

3fgr

bea

mixtureofoverlyingA

andunderlying

B.

Btkl

40-677.5YR5/67.5YR4/6 (matrix)

SiC

lmpr 2msbksh

es

ci

20%1-20cmbodiessoft

CaCO3

;

CaCO3

films

onped

facesand

liningrootchannels

(profile

7.5YR9/17.5YR7/4

ev

isbenchedat67cm).

(carbonate)

Btk2(b?)67-1477.5YR4/67.5YR4/6CL

lmsbkh

e

cwMassive

StageIIIcarbonate

withtonguesofB

(matrix)

materialoccurringin

zones10-30cmwide

7.5YR9/17.5YR8/3

m

sh

ev

andasmuchas

70cm

deep;in

someareasof

(carbonate)

(pocketsof

roadcut,massive

calichebeginsas

highas

granular

B/Ahorizon;tonguesofB

materialbeginat

material)

Btkl;few

verythinclay

films.-50%

tonguesof

Bmaterial

connectw/underlyingBhorizon.

Btk3(b?)

147-1707.5YR5.5/47.5YR4/4 (matrix)

2mpl

vh

non

ai

SimilartoBhorizon

abovebut

only30-40%

carbonatehere,in

massesasmuchas40cm

7.5YR9/17.5YR8/2

m

xh

ev

across;commonthinMncoats.

30-40%1-to

(carbonate)

2-mmgranulesof

carbonatethroughoutB

horizon.

Bk(b?)

170-2087.5YR6/4

7.5YR5/6

3cpl

eh

non

ai

Carbonateoccursas

continuouslens

(matrix)

1-2mmthickallacrossplate;

lowbulk

densitymaterial

(ash).

2Bw(b?)208-275

7.5YR7/37.5YR4/6

fSLin

sh-

non

ai

Lowbulk

density,contains

somevolcanicash;

noclay

h

veryweaklysbk.10%silica

threadsalong

root

channelsandasveins.

Profile2

platyzones

togetheroccuracrosstheoutcrop

faceina

broadlyundulatingzone.

59

Table6.

(cont.)Profile2

Depth

Color

Consistence

Horizon(cm)

Dry

MoistTextureStructureDryMoist

ReactionBoundary

Remarks

2C

7.5YR8/17.5YR7/3

m

Ashlayer,

variesinthickness

froma

feather

edgeto

-30cm.Ashoccursin

irregular

masses;weathered.

3Btlb0-50

7.5YR6/37.5YR4/4SiL

lcpr

h

noncs

Structureis

coarsestnearthe

top.Few

very

3cabk

thinclay

filmsonped

faces(maybebleached

outA?).

3Bt2b50-757.5YR5/57.5YR4/6SiL

lfpr

h

noncw

Fewerthan10%

threadsand

filmofsilicaon

3msbk

pedfaces

andliningrootchannels.

Probablya

mixtureof

TuleFormation

lakebeds

and

secondarycarbonate.Commonthinclay

films

onped

faces.

3Ckb75-907.5YR7/47.5YK7/4SiCm

h

ev

d

StageVI.

60

Stop 8: Biostratigraphy and Volcanic AshDeposits of the Tule Formation, BriscoeCounty, Texas*G. E. Schultz

Along the East Fork of Rock Creek, on the Mayfield, McDaniel and Martin Ranches, the TaleFormation ofearly and middle Pleistocene age is well exposed in a 45-m (150-ft) thick section. Nearthe base of theformation, which rests disconformably on Triassic red beds, a reversely magnetized1.2- or 1.3-Ma-old volcanic ash bed derivedfrom the JemezMountains inNew Mexico lies at a levelwhere Blancan and Irvingtonian vertebrates coexist (Martin RanchLocal Fauna). In the upperpart ofthe section, the classic Rock Creek Local Fauna and the Equus scotti Quarry are overlain by aCudahy molluscan and microvertebratefauna (MayfieldRanchLocal Fauna) covered by the normallymagnetized 0.6-Ma-old Lava CreekB (=Pearlette Type O) volcanic ash A younger molluscanfaunaappears in sediments above this ash.

Vertebrate fossils of Pleistocene (Irvingtonian)age have been found at scattered localities inthe Tule Formation for many years. Most ofthem have been collected near the head of theEast Fork of Rock Creek, a north-draining trib-utary ofTule Canyon (figs. 25, 28). The earliestcollections were made by W. F. Cumminsbetween 1889 and 1892 and by E. D. Cope in1892. Cope (1893) referred to the fossil-bearingstrata as "EquusBeds" and described numeroussignificant forms, including the holotypes ofwhat are now known as Gopherus hexagonata,Gopherus laticaudata, Camelops sulcatus, Hem-iauchenia macrocephala, and Equus semiplicatus.J. W. Gidley collected fossils for the AmericanMuseum of Natural History from 1899 through1901 and described the first specimen of Equusscotti. from the now-famous horse quarry (Gidley,1900, 1901). He thought the fauna belonged tothe "Sheridan Beds" of Pleistocene age (Gidley,1903a).

At present, two principal quarries or fossilsites are recognized:

(1) The Sloth-Camel Quarry (Rock CreekLocal Fauna) is on the west bank of theEast Fork of Rock Creek near its head,0.4 km (0.25 mi) northof the Rock Creekstore at the junction of State 86 andFM 378; 11 km (7 mi) west of Silvertonand 3.2 km (2 mi) east of the west countyline in the NW 1/4, SW 1/4, sec. 208,Blk. G-M, Denison and SE Ry. Co. Survey;

*Modified from Gustavson (1986b)

Briscoe County, Texas (fig. 28) (Troxell[1915a, p. 614] erroneously gave the loca-tion as sec. 207). The quarry is on landowned by Mrs. Roy Mayfield.

(2) The Equus scotti (=Horse) Quarry is onthe south side of a short east-drainingtributary of the East Fork of Rock Creek,1.2 km (0.75 mi) north of the Rock Creekstore in the center, NE 1/4, sec. 213,Blk. G-M, Denison and SE Ry. Co. Survey;Briscoe County, Texas (fig. 28) (Troxell[1915a, p. 614] erroneously gave thelocation as sec. 208). The site is onland ownedby Bill McDaniel. Locationsof both quarries are depicted on theUSGS Rock Creek7.5-minute topographicquadrangle map.

At the Sloth-Camel Quarry, which is fre-quentlyflooded by waters ofa stock tank, fossilsare found mainly in a 1.2-m-thick (5-ft-thick)bed ofyellowish-gray, semi-indurated sandstonethat forms a small knoll on the west side ofRock Creek just west of the Mayfield Ranchhouse and south of the earth dam. A smalleroutcrop of the same bed lies across the creekbedto the east. The quarry was worked extensivelyin 1912 by Lull and Troxell for Yale University.The Rock CreekLocal Fauna (Cope, 1893, 1895;Hay, 1908, 1924; Lull, 1915; Troxell, 1915a, b;Johnston, 1937b; Hibbard, 1953; Quinn, 1957;Dalquest, 1964; Kurten, 1967; Nowak, 1979;Kurten and Anderson, 1980; Schultz, 1986) is

61

Figure 28. Geologic map of parts of Cope Creek and Rock Creek Quadrangles. Stop 8 is at Sloth-CamelQuarry and Horse Quarry. See figures 1, 25, and 41 for location withinTexas Panhandle.

62

Figure 29. Biostratigraphic section of Tule Formation along East Fork of Rock Creek,MayfieldRanch, Briscoe County, Texas.

dominated by large- and medium-sized grazersbut includes a few browsers and semibrowsersand several carnivores. The following taxa arepresent: Testudinidae (giant land tortoises),including possibly Geochelone campester andCope's holotypes of Gopherus hexagonata andGopherus laticaudata; Glossotherium harlani(ground sloth); Sylvilagus sp. (cottontail rabbit);Cards armbrusteri (extinct wolf); Cards hatrans(coyote); Protocyon texanus (a dog of SouthAmerican affinities and origin); Arctodus simus(giant short-faced bear); Mammuthus imperator(mammoth); Platygonus sp. (extinct peccary);Camelops sulcatus (large extinct camel); Hem-iauchenia macrocephala (extinct llama); Hayo-cerosfalkenbachi (extinctpronghorn); Soergelia

(formerly Preptoceras) mayfieldi (primitivemuskox of Old World affinities and origin);and the horses Equus scotti and E. calobatus.E. calobatus (holotype based on long slendermetapodials) is probably referable to Cope'sE. semiplicatus (holotype based on teeth).

Upstream to the southeast, the sloth-camelbed is overlain by reddish-buff silts andgreenish-grayclays. Less than 0.4 km (0.25 mi)to the southeast, just south of the Mayfieldhouse, in a small tributary draw that entersRock Creek from thesouth (fig. 28), the greenish-gray clay is overlain by a normally magnetized1-m-thick (3-ft) bed of Lava Creek B (=PearletteType O) volcanic ash derived from the Yellow-stone region and dated at 0.62 Ma (Izett, 1977;

63

Izett and Wilcox, 1982). The base of the ashlies nearly 5 m (15 ft) above the top of theSloth-Camel Quarry (fig. 29). Greenish-grayclays justbeneath the ash contain a molluscanand microvertebrate fauna (MayfieldRanch LocalFauna) similar to that described by Hibbardand Dalquest (1966) (Vera Local Faunule) inKnox and Baylor Counties, Texas, and similarto the Cudahy Fauna in southwest Kansas de-scribedby Hibbard (1944, 1976), Paulson (1961),and others. Cudahy-type faunas, which containnumerous microtine and cricetine rodents, aswell as shrews, have been collected at a numberof sites in the High Plains from sedimentsbeneath the Lava Creek B Ash and are, there-fore, older than 0.62 Ma. At the Mayfield Ranch,a thin caliche unit, which directly overlies theash bed, can be traced downstream to a pointabout 5 m (15 ft) above the Sloth-Camel Quarrywhere the ash is absent, thus demonstratingthat the Rock Creek Local Fauna is somewhatolder than the Mayfield Ranch Local Fauna.Green- and rust-colored sands above the calicheunit contain a few snails of late Pleistocene age.

The Equus scotti Quarry is 0.8 km (0.5 mi)northwest of the Sloth-Camel Quarry and nearly5 m (15 ft) lower in the section (fig. 29). SinceGidley first described this horse in 1900, anumber ofmore or less complete skeletons havebeen collected and are now in the AmericanMuseum of Natural History, Yale PeabodyMuseum, and Panhandle-Plains HistoricalMuseum, Canyon, Texas. Johnston (1937c,p. 460) stated that the skeletons "were found ina fine consolidated white cross-bedded sand con-taining granules of calcium carbonate and ly-ing about 75 cm (30 inches) below a 2.5-cm(1-inch) continuous horizontal stratum of bluish-green clay, which underlies several feet of com-pact, semiconsolidated gray sand showing nosigns of crossbedding. This bed is overlain by arather tough layer of green shale, which formsthe surface."

About a mile north of the Equus scotti Quarry,on the M. G. Martin Ranch, in the NE 1/4,sec. 66, and the SE 1/4, sec. 71, Blk. A, Arnoldand Barrett Survey, in Briscoe County, Texas(fig. 28 and USGS Cope Creek 7.5-minutetopographic quadrangle map), Izett (1977) iden-tified a reversely magnetizedvolcanic ash (CerroToledo X) that was dated at about 1.2 or 1.3 Maon the basis of correlation with the Cerro Toledorhyolite in the Jemez Mountains source areanear Santa Fe, New Mexico (Izett, 1977, 1981;Izett and others, 1981; Izett and Wilcox, 1982).

This ash, which lies about 36 m (120 ft) belowthe Lava Creek B Ash, lies at or near the baseof the Tule Formation and, in places, restsdirectly on Triassic red beds of the TrujilloFormation (fig. 29). Blancan and Irvingtonianvertebrates including Equus {Dolichohippus)simplicidens, Equus semiplicatus, Camelops sp.,Stegomastodon barbouri (Madden, 1986), Mam-muthus sp., Glossotherium sp., and Glyptother-ium sp. coexist below, at, or slightly above thelevel of the ash, and the fauna (Martin RanchLocal Fauna) is similar to the Gilliland Faunafrom the Seymour Formation inKnox and BaylorCounties, Texas (Hibbard and Dalquest, 1966).The lower part of the Tule Formation is wellexposed on the Martin Ranch and consistsprimarily ofbuff to pale reddish-brown, fine siltysands locally cemented by calcium carbonateand containing lenses of caliche pebbles nearthe base. The lower half of the formation in thisarea contrasts strongly with the upper half,which is dominated by greenish-gray to pale-yellow silty sands and clays.

In addition to the fossils collected from theimmediate Rock Creek drainage, several othersignificant discoveries have been made in thearea. Gidley (1903a) reported a partial skeletonof Mammuthiis from the head of Tule Canyonabout 11 km (7 mi) west of the Equus scottiQuarry in Swisher County. This specimen waslater described by Osborn (1942). Matthew(1920) reported the discovery of the hind partof the skeleton of a giant short-faced bear{Arctodus stmus) 3.2 km (2 mi) north of thehorse quarry. This specimen, now in theAmerican Museum of Natural History, wasdescribed by Kurten (1967). An undescribedhumerus and some upper teeth of this bearfrom the Sloth-Camel Quarry are in thePanhandle-Plains Historical Museum, Canyon,Texas. G. E. Schultzcollected a diverse Cudahy-type microvertebrate and molluscan fauna froma diatomite bed beneath a thick deposit of LavaCreek B Ash in Deadman's Creek, a tributary ofTule Canyon in Swisher County, 8 km (5 mi)northwest of the Equus scotti (=Horse) Quarry.

On the basis of fossil evidence, it is possibleto draw some conclusions about the paleo-environment of the Tule Basin during a part ofthe Irvingtonian Land Mammal Age from about1.3 to about 0.6 Ma ago. The predominance oflarge and medium-sized grazers such as horses,camels, proboscideans, and muskoxen at oneor more levels in the section indicates anabun-dance of grasses in the vicinity, whereas the

64

presence of browsers and semibrowsers (pec-cary, pronghorn, and possibly the large camel)indicates the presence of shrubs and, possibly,scattered small trees. Taller grasses may havedominated the lower slopes, and shorter grassesmay have dominated better drained high ridgesand divides. The structure of the teeth ofPlatygonus, thepeccary suggests a diet of coarsevegetation or browse, whereas the pronghornprobably roamed the open grassy upland,feeding on forbs, shrubs, browse, and somegrass. Although primarily a grazer, Camelops,having a long neck and long legs, was probablyan occasional browser (Rurten and Anderson,1980, p. 305). The ground sloth, Glossotherium,generally considered a grassland species, prob-ably fed on grass and small shrubs and mayhave used its claws to dig up roots (Kurten andAnderson, 1980, p. 144). Arctodus simus, thegiant short-faced bear, and Protoqjon texanus,the South American dog, were highly predaceouscarnivores; the former undoubtedly preyed upon

the sloth and other large herbivores. Todaycursorial (running) canids such as thewolf andthe coyote range successfully through a varietyof habitats; the Rock Creek species probablyroamed through broken, open country orgrasslands.

Vegetation now in the region could not sustainthe abundant and diverse fauna that lived inthe Rock Creek area during IrvLngtonian time.Development of grasslands, indicated by abun-dance of herbivores, required greater and moredependablerainfall than the unpredictable andsporadic amounts received in this semiaridregion today. More abundant rainfall is clearlyindicated by the numerous fresh-water mollusks,rodents, and shrews of the MayfieldRanch LocalFauna, remains ofwhich are found in the clayeyand diatomaceous pond deposits. Mild, frost-free winters are suggested by the presence ofthe giant land tortoises (Hibbard and Dalquest,1966, p. 12-13).

65

Stop 9: Upper Tertiary OgallalaFormation Eolian Strata at the CaprockEscarpment, East of Silverton, TexasT. C. Gustavson

Approximately 38 m (125ft) ofeolian sediment ofthe OgallalaFormation is exposed in the CaprockEscarpment near Silverton, Texas. Eolian sediments were deposited as loess and sand sheets andcontain numerous calcic paleosols.

The OgallalaFormation is exposed in a road-cut, herein called the Silverton section, on StateHighway 256 between 18.5 and 19.3 km (11.5and 12 mi) east of Silverton, Texas (figs. 1, 25).The base of the section is at an elevation ofapproximately 907 m (2,975 ft), and the for-mation extends 38 m (125 ft) to an elevation ofapproximately 945 m (3,100 ft). Ogallalasediments in the Silverton section (fig. 30)unconformably overlie weathered and fracturedmudstones of the Triassic Dockum Group.

Stratigraphic DescriptionsLocally, narrow channels (1 to 1.5 m [3 to

4.5 ft] deep) are filled with sandy carbonate-cemented gravel at the base of this section ofthe Ogallala Formation (fig. 31 [Note that sym-bols used in this figure, as well as in figures34, 35, 38, and 40, are described in figure 32]).Gravel clasts as much as 13 cm (5 inches) longare mostly quartzites and other metamorphics,vein quartz, and fine-grained igneous rocks.Primary sedimentary structures are not pre-served, and gravel clasts appear to float in afine-grained matrix. Carbonate cement in thisunit has been silicified locally.

The remaining 36 m (119 ft) of the Silvertonsection consists of grayish-orange-pink (SYR7/2), fine to very fine sand that appears similarto fine and very fine sand sequences in theBuffalo Lake section and in the upper parts ofthe Bellview and Ragland sections (Gustavson,Stops 1, 2, and 3, this guidebook, p. 22, 32,and 38, respectively). No primary sedimentarystructures were identified in this section. Well-rounded frosted sand grains and pinkish-graycarbonate (calcrete) nodules as much as 5 cm(2 inches) in diameter are present throughout

much of the section. At least four massive(Stage IV?) pedogenic calcretes (Bachman andMachette, 1977) are present in the lower 17 m(56 ft) of this section. The upper 19 m (63 ft) ofthis exposure includes numerous paleosols pre-served as concentrations of carbonate nodulesor as slightly darker (moderate-red-brown[10R4/6] to pale-red-brown [10R5/4]) andslightly clay-rich Bt horizons. Only afew of thesepaleosols are illustrated in figure 31.

The top 3.5 m (11.6 ft) of the Silverton sectionis a massive pinkish-gray (SYRB/1) to grayish-orange-pink (SYR7/2) Stage VI calcrete, theOgallala Caprock caliche. The calcrete is lami-nated but does not appear to be brecciated orpisolitic. Large areas of dense carbonate fractureconchoidally.

Facies InterpretationsThe shallow, widely separated gravel-bearing

channels at the base of the Silverton sectionrepresent fluvial deposition, but the lack of pre-served sedimentary structures and the sparse-ness of these deposits precludes additionalinterpretation.

The upper 36 m (119 ft) of the Silvertonsection is similar to the Buffalo Lake section(Stop 11, p. 72) and probably represents eoliandeposition, judging from the texture of thesesediments and from the presence of rounded tosubrounded frosted grains. Primary sedimentarystructures were destroyed partly by bioturbationand partly by the disruption of sediments duringsoil-forming processes, mainly precipitation ofcarbonate. The numerous preserved paleosolsrepresent periods of landscape stability followedby influxes of additional eolian sediment.Although few root structures are preserved in

66

Figure 30. View of upper Tertiary Ogallala Formation exposed alongState Highway 256 at Caprock Escarpment, approximately 19 km(12 mi) east of Silverton, Texas. The Ogallala contains numerousburied calcic soil horizons in additionto Caprockcaliche that markstop of OgallalaFormation. Section is approximately20 m (65 ft) high.

this section, the landscape stability indicatedby development of paleosols also suggests thatthe Ogallala surface was vegetated.The Caprockcaliche that marks the top of the OgallalaFor-mation is a Stage VI (see Machette, 1985, fordescriptions of stages of development for cal-cretes) pedogenic calcrete and represents anextended period of landscape stability.

CementationThe lower 1.5 to 2 m (4.5 to 6 ft) of the

Silverton section is a calcrete composed ofcarbonate-cemented sand and gravel. Gravelclasts appear to float in the fine-grained car-bonate matrix. The lack of brecciation andlamination of carbonate deposits, characteristics

67

Figure 31. Composite profile of Ogallala Formation exposed along State Highway 256, approximately19km (12 mi) east of Silverton, Texas. Symbols for sedimentary structures describedin figure 32. Fieldobservationsnotedto right of column.

68

Figure32. Symbols used in descriptivesections in figures 31, 34, 35, 38, and 40.

generally attributable to pedogenic calcretes,suggests that this is a ground-water calcrete.Locally, this carbonate cementhasbeen replacedby silica. Theremainder of the section is moder-ately to slightly carbonate cemented. Thiscement is mostly the result of pedogenic pro-cesses and consists of carbonate films along

ped faces, carbonate nodules, and pedogeniccalcretes.

AgeNo datable materials were observed at the

Silverton section.

69

Stop 10: Upper Tertiary OgallalaFormation Strata at the CaprockEscarpment, Palo Duro Canyon StatePark, TexasT. C. Gustavson

The upper Tertiary OgdLlala strata exposed in the Caprock Escarpment atPalo Duro Canyon StatePark contain eolian sediments deposited as sheet sands and loess andjluvial sediments deposited bybraided streams. Pedogenic calcretes lie within the eolian section and ground-water calcretes liewithin thefluvial section.

The OgallalaFormation is exposed in a road-cut, herein called the Palo Duro Canyon StatePark section, along the park entranceroad wherethe road crosses and begins to descend theCaprock Escarpment (figs. 1, 33). The OgallalaFormation unconformably overlies TriassicDockum Group mudstone at an approximateelevation of 1,015 m (3,330 ft) (fig. 34). Beneaththe middle Tertiary erosional surface thatseparates these twounits, Dockum Group light-olive-gray (5Y6/1) mudstone is weathered toyellowish gray (5Y7/2) to a depth of 1.5 m (5 ft).

Stratigraphic DescriptionBasal Ogallala sediments in the Palo Duro

Canyon State Park section contain roundedpebble- to cobble-sized, partly carbonate cement-ed gravel composed of quartzite and igneousand various fine-grained metamorphic clasts.These gravels lie inshallow narrow channels 1 to2 m (3 to 6 ft) deep. Neither volcanic clasts norprimary sedimentary structures were identifiedin this unit. Calcium carbonate (caliche) nodulesare preserved in thecemented zones.

Figure33. Map of Canyon, Texas, andvicinity, showing FieldTrip Stops 10 and 11. Derivedfrom PlainviewSheet, U.S. Geological Survey (1:250,000 series). See figure 1 for location.

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Figure 34. Vertical compositeprofile of OgallalaFormation exposed at Caprock Escarpment along entranceroad to Palo Duro Canyon State Park, 26 km (16 mi) east of Canyon, Texas. Symbols for sedimentarystructures described in figure 32. Field observationsnotedto right ofcolumn.

Overlying the basal gravel is 4 m (13 ft) offine to very fine sand containing dispersedsiliceous pebbles. No preserved sedimentarystructures are present within this section. Cal-cium carbonate (caliche) nodules as much as3 cm (1.2 inch) in diameter are common. Thelowest 1 to 1.5 m (3 to 5 ft) is carbonate

cemented and contains caliche nodules. Thebasal cemented zone forms an erosionallyresistant layer that can be seen throughout thePalo Duro Canyon area. Locally this basal unitcontains siliceous nodules or is entirely silicified.Silicified parts are nodular to massive, moderatebrown (10R4/6), and they fracture conchoidally.

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Ghosts ofcaliche nodules are identifiable withinthe silicified zone, but the nodules also havebeen silicified. The silicified zone is fractured,and locally fracture faces are partly covered withopal films.

The upper 2 m (6 ft) of this unit is stronglycarbonate cemented, forming a massive con-choidally fracturing calcrete. Uncemented enclo-sures of fine sand and carbonate nodules arepresent. Ghosts of carbonate nodules remain,along with rare dispersed siliceous pebbles.

Above the calcrete lies 12 m (40 ft) ofhorizontally bedded, crossbedded, and ripple-laminated sand. This sectionfines upward frommedium sand at the base to fine sand near thetop; the thickness of crossbeds also diminishesupward from 20 to 30 cm (8 to 12 inches) atthe base to 2 to 10 cm (0.8 to 4 inches) nearthe top of the exposure. Silty clay drapesshowing evidence of desiccation overlie upward-finingripple-laminated sequences. This sequencedoes not contain calcium carbonate (caliche)nodules.

This part of the section is poorly cemented,although local case hardening occurs where thesurfaces of some strataare carbonate cemented.Lenses of carbonate-cemented sand (ground-water calcretes) are also present.

Overlying the fluvial section described pre-viously is a 3.5-m (12-ft) section covered withcolluvium. The top of the section exposes aweathered and extensively fractured part of theCaprock caliche.

Facies InterpretationsThe lack of preserved primary sedimentary

structures in the lower 6.75 m (22.3 ft) of thePalo Duro Canyon State Park section (fig. 34)makes interpreting the environments of depo-sition difficult. The channel-filling roundedgravel clasts at the base of the section wereprobably deposited by small, possibly braided,streams. Except for a few dispersed gravel-sizedclasts, the 4 m (13 ft) of fine to very fine sandoverlying the gravel is similar in grain size toeolian material described in the Silverton,Buffalo Lake, Bellview, and Ragland sections(Gustavson, Stops 9, 11, 12, and 13, this guide-book, p. 65, 72, 75, and 79, respectively). Theabsence of primary sedimentary structures andthe presence of caliche nodules indicate thatthe section has been altered by pedogenic pro-cesses and perhaps has been bioturbated. Thepresence of pedogenic caliche nodules in this

part of the section suggests that a stable land-scape and a slow rate of accumulation of sedi-ment prevailed when the nodules were beingformed.

The lower part of the 5.5-m-thick (18-ft) se-quence of fluvial sediments in the middle of thePalo Duro Canyon State Park section consistsprimarily of planar and trough crossbeds andhorizontal beds. Ripple cross-stratification andsilt/clay drapes are missing. The sedimentarystructures present probably represent super-imposed bars similar to those preserved in aPlatte River type (Smith, 1970) of sandy braidedstream.

The upper part of the fluvial sequence of thePalo Duro Canyon State Park section includesnumerous upward-fining sequences capped byripple cross-stratification and silt/clay drapesshowing evidence of desiccation. These struc-tures suggest deposition during repeated floodevents by high-energy, shallow sandy braidedstreams exhibiting highly variable water andsediment discharge, similar to the flood eventsat Bijou Creek, Colorado (McKee and others,1967).

CementationSeveralepisodes of cementationhave probably

affected thePalo Duro section. Two ground-watercalcretes are present near the base of the sec-tion. The base of the Ogallala section is stronglycarbonate cemented to a thickness of about 2 m(6 ft). Ground-water calcretes do not displayany of thecharacteristics of pedogenic calcretes.Although ghosts of pedogenic carbonate nodulesare present, the basal calcrete is not laminatedand does not appear to be fractured andrecemented. Clasts of the original sediment inthis section may have been slightly dispersedby the cementationprocess but are not excludedfrom the calcrete. Locally this calcrete has beensilicified. A second calcrete lies about 2 m (6 ft)above the basal calcrete and is similar in char-acter. In addition, numerous individual bedswithin the fluvial section are cemented by cal-cium carbonate to form thin, discontinuousground-water calcretes.

AgeNo datable materials were observed in this

section.

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Stop 11: Upper Tertiary OgallalaFormation at the Caprock Escarpment,Buffalo Lake National Wildlife Refuge,Texas PanhandleT. C. Gustavson

About 25 m (83ft) of Upper Tertiary OgallalaFormation eolian sediments are exposed at theBuffaloLake National Wildlife Refuge, Texas. These strata were extensively modified by pedogenicprocessesthatformed calcic soils.

The Ogallala Formation is exposed in aroadcut, herein called the Buffalo Lake section,on the southeast side of FM 168, in the BuffaloLake National Wildlife Refuge, approximately 5km (3 mi) south of Umbarger, Texas (figs. 1,33). The base of the section is at an elevation ofabout 1,103 m (3,620 ft), 0.3 km (0.25 mi) eastof the Buffalo Lake dam. Triassic Dockum Groupstrata exposed at thebase of the section containbrecciated sandstones and mudstones that dipapproximately 20° SW (fig. 35). Fractures arefilled with carbonate-cemented fragments ofDockum strata. The upper 1 to 1.5 m (3 to 5 ft)contains brecciated mudstones partly displacedby laminated calcium carbonate (calcrete). Thismay be a remnant of a pedogenic calcretedeveloped at the middle Tertiary erosional sur-face on Dockum strata.

Stratigraphic DescriptionA massive, 2.2-m-thick (7-ft) calcrete lies at

the base of the OgallalaFormation (fig. 35). Thecalcrete is locally brecciated and silicified,silicification boundaries cutting across brecciaclasts. Rare quartzite pebbles are dispersed inthe calcrete.

Overlying the calcrete is 21 m (70 ft) of fineto veryfine pinkish-gray (SYRB/1) to light-brown(SYR6/4) sand and silt. No primary sedimen-tary structures are preserved in this sequence,although numerous white carbonate (calcrete)nodules are present throughout the section. Acrude vertical columnar structure is presentthroughout most of this sequence that appar-ently reflects differential carbonate cementationalong soil ped faces. The slightly resistant areasare more heavily carbonate cemented. Opalized,

downward-branching tubules, apparently repre-senting silicified root traces, arepresent locally.Several paleosols are present as pedogenic car-bonate horizons near the top of the section(fig. 36), where the number and size of calcretenodules increase. The pedogenic Ogallala Cap-rock caliche, approximately 2.5 m (8.2 ft) thick,lies at the top of the section. The upperpart ismassive and intensely fractured. No secondarylaminations were observed.

Facies InterpretationDockum strata below the middle Tertiary

erosional surface appear to have undergonepedogenesis, whichresulted in the developmentof pedogenic calcrete. If so, then the middleTertiary erosional surface in this locale wasstable long enough for a mature soil profile todevelop.

There is no evidence of fluvial deposition atthe Buffalo Lake section. The 21 m (70 ft) ofOgallala Formation sediments exposed at theBuffalo Lake section is predominantly fine toveryfine silty sand. Some sand grains are frostedand well rounded. The presence of frosted, well-rounded sand grains and the texture of thesesediments suggest that the entire section wasdeposited by eolian processes in a way similarto the deposition of the upper parts of theRagland and BelMew sections (Stops 12 and13). The large percentage (commonly 40-70%)of fine to very fine sand is too coarse for loess,but the presence of a significant proportion ofsilt- and clay-sized (30-60%) material supportsa premise of loess deposition. Preserved roottraces, paleosols, and caliche nodules, as wellas the absence ofpreserved primarysedimentary

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Figure35. Compositeprofile of OgallalaFormation exposedalongFM 168 in Buffalo Lake NationalWildlifeRefuge, 5 km (3 mi) southofUmbarger, Texas. Symbols for sedimentary structures describedin figure 32.Field observationsnoted to right of column.

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Figure 36. View to north across valleyofTierra Blanca Creek, Buffalo Lake NationalWildlife Refuge. Threeresistant buried calcretes are exposed in valleywall ofTierra Blanca Creek; two are almost continuousneartop of valleyside, and the thirdis discontinuouslyexposed. See arrows.

structures, suggest slow accumulation of sedi-ment on a stable landscape. The combinationof sand-, silt-, and clay-sized material suggeststhat mixed eolian processes account for depo-sition of this section. Examples of modernanalogs are loess deposition (Miller and others,1984) and deposition as sand sheets (Frybergerand others, 1979;Kocurek and Neilson, 1986).

CementationThe entire Buffalo Lake section is weakly

cemented by calcium carbonate. Carbonatenodules, probably resulting from pedogenic

processes, are scattered throughout the section.Near the base of the section lies a 2-m-thick(6-ft) calcrete that is partly silicified and mas-sive. Although there is little evidence of brec-ciation and recementation of carbonate clasts,no other characteristics suggest that this basalOgallala calcrete is pedogenic in origin. Thecalcrete is apparently the result of precipita-tion of calcium carbonate from ground water.

AgeNo datable materials were found in this

section.

75

Stop 12: Upper Tertiary OgallalaFormation at the Caprock Escarpment,North of Bellview, New MexicoT. C. Gustavson

Upper Tertiary Ogallala Formation strata exposed at the Caprock Escarpment 13km (8 mi) north ofBellview, New Mexico, consist of a lowerfluvial section overlain by eolian sediments. The eoliansediments have been modified by the development of numerous calcic paleosols, and the fluvialsediments were deposited by high-energy ephemeral braided streams.

The OgallalaFormation is exposed in a road-cut, herein called the Bellview section, at theCaprock Escarpment approximately 13km (8 mi)north of Bellview, New Mexico, on New MexicoState Highway 93 (figs. 1, 37). About 29 m (96 ft)of OgallalaFormation strata is exposed at theCaprock Escarpment (fig. 38). The OgallalaFormation at the Bellview section rests uncon-formably on weathered and faulted Triassic

Dockum Group strata. Clastic dikes in theDockum are filled with basal Ogallalasediments.

Stratigraphic DescriptionOverlying the middle Tertiary unconformity

is a 1-m-thick (3.3-ft) sequence of angular tosubangular gravel overlain by a light-brown

Figure 37. Map of parts of Quay and Curry Counties, New Mexico and Deaf Smith County, Texas, showingField Trip Stop 12 at Caprock Escarpment. Derived from Clovis Sheet, U.S. GeologicalSurvey (1:250,000series). See figure 1 for location.

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Figure 38. Composite profile of Ogallala Formation exposed at Caprock Escarpment along New MexicoState Highway 93, 13 km (8 mi) north of Bellview, New Mexico. Symbols for sedimentary structuresdescribedin figure 32. Fieldobservationsnoted toright of column.

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(SYRS/6), sandy clay loam (fig. 38). Color andtexture suggest that this is a buried B soilhorizon. No primary sedimentary structures arepreserved in this unit. Most of the gravel claststherein are angular to subangular fragments ofplinthite (iron-cemented sand) or siliciiied valvesof the Cretaceous pelecypod Gryphaea.

Unconformably above the paleosol lies 10 m(33 ft) of flatbedded and crossbedded pebblysands (fig. 38). Channel cutbanks at 7 and 12 m(23 and 40 ft) are preserved in this sequence.Blocks of collapsed bank material, lithoclasts,and armored mud balls lie in the channel fills.Overlying this sequence of pebble sands is athird channel (at 15 m [49 ft]) filled by 0.75 m(2.5 ft) of laminated carbonate-cementedmudstone. In turn this channel fill is overlainby numerous 20- to 40-cm-thick (8- to 16-inch)sequences of horizontally bedded pebble gravelor pebbly sand that fine upward to horizontallybedded or crossbedded sand. Generally thesesequences are capped by thin silt/claydrapes.Curled edges along mudcracks through thedrapes indicate that desiccation occurred afterdeposition of the sand. Clay drapes arecommonly overlain by beds of amorphous,nodular, calcium-carbonate nodules that canreach as much as 10 cm (4 inches) in thickness.No clastic sedimentary material is in thesenodules.

The upper 14.8 m (49 ft) of the Bellview sec-tion differs markedly from the underlying strataand predominantly contains fine to very finepinkish-gray (SYRB/1) sand capped by the4-m-thick (13-ft) Caprock caliche. The fine andvery fine sand section has a crude verticalcolumnar structure, apparently the result ofdifferential carbonate cementation. Carbonatenodules are scattered throughout this part ofthe section. At about 13 m (43 ft) below thesurface, two slightly darker (SYRS/6), light-brown zones preserve a higher clay content andapparently are buried B horizons. At least sixburied pedogenic calcretes are indicated by dif-fuse zones of increased carbonate cement orcarbonate nodules. No primary sedimentarystructures were preserved in this material.

The massive Caprock caliche that caps theBellview section is pinkish gray (SYRB/1) and isnearly 4 m (13 ft) thick. The base of the Cap-rock caliche displays an upward increase in sizeand number of carbonate nodules. Toward thesurface the calcrete becomes more massive. Theupper part is a laminated, brecciated, pisoliticStage VI calcrete (Bachman and Machette, 1977).

Numerous chalcedony veins are exposed atabout 2 m (6 ft) below the surface.

Facies InterpretationThe fine-grained, clay-rich paleosol overlying

a thin zone of angular fragments at the base ofthe section represents a weathering and soil-forming horizon. The angularity of the coarsefragments suggests accumulation without sig-nificant transport. This unit preserves a thincolluvial deposit, modified by pedogenesis, thatformed on the middle Tertiary erosional surfacebefore deposition of Ogallala Formation fluvialsediments.

The fluvial sands and gravels exposed at theBellview section make up channel fills andseveral upward-fining sequences within a largerupward-fining unit. Horizontally bedded andcrossbedded pebbly sands fine upward and arecapped by desiccated silt/claydrapes. Channel-fill sequences begin at erosion surfaces andinclude armored mud balls and rotated slumpblocks near the channel floors. These sedimentswere deposited by streams, the sediment andwater discharge of which were highly variable.Each upward-fining sequence capped by a silt/clay drape represents a flood event followed bysubaerial exposure. The Bijou Creek and SouthSaskatchewan River types of sandy, braided,ephemeral streams appear tobe modern analogsfor these deposits (McKee and others, 1967; Cantand Walker, 1978).

Midway through the Bellview section atapproximately 14 m (46 ft), a fundamentalchange in depositional processes is preservedin the sedimentary record. The upper part ofthe Bellview section primarily contains fine tovery fine sand having no preserved primarysedimentary structures. The development ofpaleosols in this part of the section is indicatedby several preserved pedogenic calcretes andtwoB horizons. Carbonate nodules (caliche) areabundant throughout the upper part of thesection. Grain-size distribution and uniformityof grain size throughout the upper part of thesection resemble those of eolian beds of theupper part of the Ragland section (Stop 13, thisguidebook, p. 79) and those of the eolian sec-tions of the Ogallala described by Winkler(1985). The stacked paleosols show no evidenceof erosion between them, indicating that thesurface ofaccumulation was a stable landscape.The absence of sedimentary structures also

78

suggests bioturbation. The development ofpedo-genic calcretes andB horizons results from long-term landscape stability during which pedogenicprocesses have a chance to operate. The pres-ence of both sand and silt fractions suggeststhat deposition was mixed and probably includedeolian sand sheets and loess deposited on astable grass-covered landscape (see Frye andLeonard, 1957, for discussions of Ogallala flora).As suggested by Fryberger and others (1979)and Kocurek and Neilson (1986), vegetation,particularly grasses, probably plays a significantrole in stabilizing eolian sand sheets. Clearly,vegetation would also act as a baffle to stabilizewindblown dust.

Ogallalafluvial sediments at the Bellview sec-tion differ from those at the Ragland section(Stop 13, this guidebook, p. 79) in several signifi-cant ways. The Bellview section is primarilysand, whereas the Ragland section is sand andcoarse gravel, especially at the base of thesection. Gravel clasts at the Bellview sectionare mostly fragments of an iron-cemented sand(plinthite), Gnjphaea, and quartzite pebbles.Plinthite fragments are absent at the Raglandsection, and Gryphaea are rare. Basic volcaniccobbles are common at the Ragland section butdo not appear at the Bellview site. These dataindicate that the fluvial systems operating atthese two sites during the late Tertiary had sig-nificantly different flow regimes and that thesources of sediment available to the two streamsystems may also have been significantlydifferent.

CementationCarbonate cementation is widespread but

variable within the fluvial and colluvial sedi-ments that make up the lower part of theBellview section. Most of the section is poorlycemented, but some finer grained sand and mudunits are moderately well cemented.

Beds of calcium carbonate as much as 10 cm(4 inches) thick have accumulated above thin,mud-cracked silt/claydrapes, which may haveretarded the downward flow of ground water.The carbonate beds are nodular and have notincorporated any of the adjacent clastic material.The mechanism by which CaCO3 accumulatedis not understood. Pedogenic carbonate nodulesform at shallow depths in soils by precipitationfrom soil waters and in the process of forma-tion exclude most soil particles. Perhaps a sim-ilar process accounts for the carbonate beds inthis section, but the precipitation of calciumcarbonate is apparently from ground water thathas percolated somewhat deeper than normalsoil-formingdepths of 1 to 2 m (3.3 to 6.6 ft).

AgeNo datable material was observed at the

Bellview section. No basic volcanic clasts wereidentified at the Bellview section, so the relativeage of the sectioncannot be determined.

79

Stop 13: Upper Tertiary OgallalaFormation at the Caprock Escarpment,Ragland, New MexicoT. C. Gustavson

The upper Tertiary OgallalaFormation exposedat the CaprockEscarpment atRagland, NewMexico,has a lowerfluvial section containingcoarse gravel deposited by high-energy braided streams. Eoliansediments deposited as loess and sand sheets overlie the Jluvial section. Eolian sediments areextensively modified by pedogenesis toform calcicpaleosols.

The Ogallala Formation is exposed in aroadcut, herein called the Ragland section, atRagland, New Mexico, along New Mexico High-way 18, approximately 37 km (23 mi) south ofTucumcari, New Mexico, in a north-facingsegment of the Caprock Escarpment (figs. 1,39). This section exposes approximately 25 m(85 ft) of the OgallalaFormation (fig. 40), whichwas deposited unconformably on TriassicDockum Group strata. The base of the sectionlies at an elevation of approximately 1,458 m(4,785 ft).

Stratigraphic DescriptionThe lower 1.5 m (5 ft) of the Ogallala For-

mation exposed in theRagland section is a clast-supported, carbonate-cemented siliceous gravelcontaining primarily well-rounded volcanics,quartzite, and other fine-grained metamorphicclasts. Intermediate axis lengths of 7 cm(3 inches) are common. Rare angular clasts ofDockum sediment as much as 20 cm (8 inches)long are present, but their angularity, relativesoftness, and large size indicate they have notbeen transported any great distance. These basalgravels are horizontally bedded and imbricated,and they compose at least three upward-finingsequences. Calcium carbonate cement occupiesmost original pore space.

Overlyingthebasal conglomerate is 7 m (23 ft)of interbedded clast-supported, carbonate-cemented siliceous conglomerates and pebblysandstones. Conglomerates are horizontallybedded, and clasts are well rounded and imbri-cated. Upward-fining sequencesrange in thick-ness to 0.8 m (2.3 ft). Sandstones are composedof pinkish-gray, pebbly coarse sand preservedas low-angle tangential cross sets. This section

Figure 39. Map ofTucumcari, New Mexico, area(QuayCounty) showing Field Trip Stop 13. Derived fromClovis andTucumcariSheets, U.S. GeologicalSurvey(1:250,000 series). See figure 1 for location.

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Figure 40. Composite profile of Ogallala Formation exposed at Caprock Escarpment along New MexicoState Highway 18 at Ragland, New Mexico. Symbols for sedimentary structures described in figure 32.Field observationsnoted to right of column.

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is capped by 0.75 m (2 ft) ofpinkish-gray, cross-bedded, vuggy weathering, carbonate-cementedsandstone. The apparent paleofiow direction asdetermined from cross-set orientations was tothe southeast.

Overlying approximately 2.4 m (7.9 ft) ofsection obscured by slope wash is 4 m (13 ft) ofinterbeddedpebbly sand and gravel. No primarysedimentary structures are identifiable. Originalsediment appears to havebeen a pebbly mediumsand interbedded with medium gravel (inter-mediate axis as much as 5 cm [2 inches]). Atleast two and possibly three zones of pedogeniccalcrete (caliche) formed within these sediments.Calcrete development, or carbonate cementation,increasesupward. Initially, vertical zones of dis-persed carbonate cement resulted in a crudevertical prismatic structure in coarse sands, thecarbonate becoming nodular and then massivenear the top of this section. The original clasticground mass is generally excluded from thecarbonate nodules. Individual nodules extendin diameter to approximately 2 cm (0.75 inch),increasing upward in number and size. Massivecarbonate near the top of this section is partlybrecciated, recemented, and pisolitic, and it con-tains chalcedony inveins. These are the featuresthat characterize calcic soils and pedogenic cal-cretes (Bachman and Machette, 1977).

Massive calcium carbonate is present as hori-zontal beds of crude moundlike structureshaving relatively sharp upper boundaries.Clastics that are part of the original sedimentsare excluded from the massive carbonate,although minor sand and gravel clasts float inthe carbonate mass. The spaces between themounds are filled with structureless, poorlycemented sand or gravel. The massivecarbonatehorizons represent at least one Stage IV or Vpedogenic calcrete (Bachman and Machette,1977). The spaces between the mounds probablyresulted from carbonate solution forming pitlikefeatures in the calcrete. Later fluvial sedimen-tationfilled thepits, and pedogenesis alternatedwith carbonate solution to form the second setof calcrete mounds.

The style of sedimentation changes abruptlyapproximately 16.5 m (55 ft) above the base ofthis Ogallalaalluvial section. The clastic materialthat comprises the upper 6 m (20 ft) of theRagland section is primarily pinkish-gray, fineto very fine sand. Many sand grains are roundedand frosted, and no primary sedimentary struc-tures are preserved. Carbonate content increasesupward. Carbonate cement deposited prefer-

entially along vertical infiltration pathways hasproduced a crude vertical or columnar structure.Carbonate nodules increase in size and num-ber upward, grading to a massive 2.2-m-thick(7.3-ft) pedogenic calcrete, the Caprock caliche,at the top of the section. This massive pinkish-gray calcrete is complexly brecciated and rece-mented at the surface. The upper part is deeplyweathered, and thepreserved portion is probablyequivalent to the Stage VI pedogenic calcrete ofBachman and Machette (1977).

Facies InterpretationThe fluvial sands and gravels exposed in the

Ragland section were deposited in a major chan-nel system that contained streams that flowedsoutheastward across the middle Tertiary land-scape (fig. 4). The fluvial deposits fine upwardfrom mostly gravel near thebase of the channelto mostly sand near the top. Upward-finingsequences ofhorizontally bedded gravels overlainby crossbedded sands suggest deposition ofsuperimposed bars by high-energy, high-sediment-load, braided, and flashy-dischargestreams. The change from gravel-dominant tosand-dominant facies suggests that at least twomodern analogs may apply. These are the ScottRiver type, coarse-gravel, braided-stream modelfor the gravel sequences (Boothroyd and Ashley,1975) and the Donjek River type, sand-and-gravel, braided-stream model for the entiresection (Williams and Rust, 1969; Rust, 1972).

The upper 6 m (20 ft) of the Ragland sectionconsists of fine to very fine sand containingrare floating granules or small pebbles. Somesand grains are frosted. The lack of preservedsedimentary structures and the pervasive devel-opment of calcic soils and pedogenic calcretemake it difficult to interpret the process by whichthis part of the sectionwas deposited. However,the presence of frosted grains and the grainsize of these sediments suggest deposition byeolian processes.

These fine to very fine sands probably are toocoarse to have been deposited entirely fromsuspension as loess. However, the presence ofas much as 50 percent silt- and clay-sizedmaterial makes it likely that eolian dust con-tributed to these sediments. The coarser fraction,especially fine and very fine sand, either movedprimarily as material in saltation or becametemporarily suspended within a meter or two ofthe surface. Modern and Wisconsinan analogs

82

are loess or dust deposits (Pewe, 1981; Millerand others, 1984) and sand sheets as describedby Fryberger and others (1979) and Kocurekand Neilson (1986). Winkler (1985) describedsimilar silty, fine sand facies southeast ofLubbock, Texas, in his studies of the Ogallalaand also attributed their deposition toprocessessimilar to those that deposit loess and sandsheets.

CementationCarbonate cementation in the lower, fluvial

part of the section increases downward and isirregularly expressed as erosionally resistantlenses in sandy facies. Carbonate cement fillsvoids between gravel clasts near the contactwith the underlying Dockum and partly coatsclasts higher in thesection. Because no evidenceof clast displacement by carbonate cementexists, and because no structures characteristic

of pedogenic calcretes were identified, calcretesin the lower part of the fluvial section probablywere deposited from ground water.

AgeBecause the Ragland section containsneither

fossil material nor tephra, the age of thesedeposits cannot be determined with accuracy.Numerous large, rounded, amygdaloidal basaltcobbles are present in the basal gravels. Basicvolcanic flows northwest of the Ragland sectionin the Ocate and Raton volcanic fields have beendated as 8.3 Ma or younger (Stormer, 1972;O'Neil and Mehnert, 1980). These flows are thenearest extrusive basic volcanics up paleoslopefrom this section. Either field may be the sourceof the basic volcanic clasts in the Raglandsection; thus the basal portion of the Ogallalahere is no older than 8.3 Ma.

83

Stop 14: The Clarendonian Faunas of theTexas and Oklahoma PanhandlesG. E. Schultz

The Clarendoninnfaunas ofthe Texas and Oklahoma Panhandle region are dominated by mediumto large grazingmammals. The Exell, Coetas Creek, and Cole Highway Pit Local Faunas ofTexas andthe Laverne and Durham Local Faunas of Oklahoma also contain a large number ofgrazing animals,suggesting aparkland or woodland savanna.

Geology and TaphonomyMost of the Ogallala sediments in the

Clarendon, Texas, region (figs. 41, 42) are theunfossiliferous, massive, structureless buff tobrown silty eolian sheet sands that are char-acteristic of the Ogallalaelsewhere in the GreatPlains. A few places have exposures of coarse,fairlywell sorted and loosely consolidated yel-low to gray to brown sands and some gravelsrepresenting stream-channel deposits. Moreextensive exposures of fine greenish-gray tobrown clay and silt, commonly containing thinflaggy lenses of fresh-water limestone and repre-senting overbank fioodplain, backswamp, and"oxbow lake" deposits can also be found. Thesefluvial deposits are scattered for an east-westdistance of about 24 km (15 mi) along ridgesand divides and in small tributary draws northof the Salt Fork of the Red River. They dem-onstrate that eastward-flowing meandering andbraided streams flowed here during Claren-donian time.

Some fossils apparently accumulated inponds, lakes, or marshy areason grass-coveredfloodplains (for example, fossils found atMacAdams, Dilli, Risley, Farr, Noble, andBromley localities [figs. 41, 42]), whereas others,which are broken and waterworn, were buriedin the coarser ferruginous sands of streamchannels (Quarries 1 through 5 on the Rowe-Lewis Ranch) (figs. 41 through 44). Completelyarticulated skeletons are rarely found except insinkhole deposits on the Rowe-Lewis Ranchnortheast of Clarendon.

The sinkholes developed as a result of sub-surface dissolution of evaporite minerals in thePermian red beds, followed by collapse of theoverlying sediments. These sinks were steepwalled and filled rapidly with the water andsand that washed into them. Animals that were

trapped in them were buried intact. The FrickLaboratory excavated about two dozen horseskeletons and a number of other mammals fromthe largest of the sinks exposed on the northside of Petrified Creek (Rowe-Lewis RanchQuarry 7) (fig. 42, site 19). The skeletons, al-though complete, are difficult to remove fromthe ferruginous concretionary sandstone matrixthat surrounds them. The deposits are easilyidentified in the field as yellow to brown sandin sharp contact with Permian red beds, whichmay bend sharply downward around the edgeofa sink. Along the south side ofPetrified Creek,the sinkhole fillings were more resistant thanthe surrounding Permian red beds, which haveeroded away leaving the sinkhole deposits ashigh, flat-topped hills capped by flaggy, fresh-water limestones. These have been termed the"Leaf Hills" (fig. 42, sites 14 and 15) becausefossil leafimpressions have been found there.

Volcanic ash beds are rare in the Clarendonregion. One deposit can be found on the TomD'Spain Ranch, adjacent to the Rowe-LewisRanch. Unfortunately, it does not overlie anyfossil-bearing strata but is exposed in the bedof Petrified Creek 0.8 km (0.5 mi) north ofGidley's 3-Toed Horse Quarry (fig. 42, site 16;fig. 45). It is reported (M. F. Skinner, personalcommunication, 1976) to have contained a skullof Pseudhipparion. A sample of volcanic glassfrom this deposit yielded a glass fission-trackdate of 8.1±0.5 Ma (J. D. Boellstorff, personalcommunication, 1977).

FaunaFossils have been collected from the

Clarendon region for nearly a century. The firstcollections were made by Cope and Cumminsin 1892 for the Texas State Geological Survey

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Figure 41. Location of principal Clarendonian, Hemphillian, Blancan, and post-Blancan faunas in theTexas and OklahomaPanhandles. Clarendonian: (1) Laverne (=Beaver), (2) Exell, (3) Coetas Creek, (4)Clarendon (Shannon Ranch, MacAdams, and Grant Quarries), (5) Clarendon (Dilli, C. Risley, A. Risley,Noble=Farr, Bromley Ranches), (6) Clarendon (Lull Quarries), (7) Clarendon (Rowe-Lewis Ranch, SpadeFlats, Gidley's 3-Toed Horse Quarry), (8) Clarendon (Whitefish Creek: Pliohippus Jossulatus skull), (9)Clarendon (Skillet Creek Divide: Gidley's 1901 Mastodon and Dinocyon skull), (10) Durham. EarlyHemphillian: (11) Arnett (=Port-of-Entry Pit) and Capps=Neu=PrattPits, (12) Higgins (=Sebits Ranch) andCole Highway Pit (Late Clarendonian or Early Hemphillian), (13) Box T and V. V. Parker Pits. LateHemphillian: (14) Optima (=Guymon), (15) Coffee Ranch, (16) Goodnight, (17) Christian Ranch, (18) Axtel,(19) Currie Ranch, (20) Rita Blanca Creek, (24) Smart Ranch. Blancan: (18) Cita Canyon, (20) Rita BlancaCreek, (21) Red Corral, (22) Blanco. Post-Blancan: (23) Rock Creek andEquus scotti Quarries, (24) Slaton.

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Figure 42. Location of Clarcndonian faunal sites in Donley County, Texas. (1) Shannon Ranch, (2) Grant(=Littlefield), (3) MacAdams (=Porter), (4) Dilli (=Cope's loc.?), (5) Charles Risley, (6) Adam Risley [Pliocyonwalkeraeskull), (7) Ward's Creek BluffPit, (8) Noble (=Farr), (9) Bromley [Synthetoceras type and Gidley's1899 Mastodon), (10) Lewis (=Rowe) Quarry 1, (11) Lewis Quarries 2 and 3, (12) Lewis Quarries 4 and 5,

(13) Lewis Quarry 6, (14) Vaughn Quarry and Leaf Hills 1, 2, and 3, (15) LeafHills 4 and 5, (16) Gidley's 3-ToedHorse Quarry (=D'Spain), (17) Lewis Quarry 11, (18) Lewis Quarry8, (19) Lewis Quarry 7, (20) Stirtonand Chamberlain 1939 Pliohippusfossulatus skull, (21) Lewis Quarries 9 and 10, (22) Lull Mastodon, (23)Lull Quarry. Skillet Creek Divide (Gidley's 1901 Mastodon and Dinocyon skull) not shown on map.Unpublished locality information courtesyofWill Chamberlainof Clarendon, Texas.

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Figure 43. Rowe-Lewls Ranch Quarry 4 (Clarendonian), Donley County,Texas. Quarry produced abundant rhinoceros. Photo courtesy ofPanhandle-PlainsHistoricalMuseum, Canyon, Texas.

Figure 44. Rowe-Lewis Ranch Quarry 4 (Clarendonian), Donley County,Texas. Photo courtesy of Panhandle-Plains Historical Museum, Canyon,Texas.

(Cope, 1893); these materials are now at theTexas Memorial Museum, The University ofTexas at Austin. Gidleycollected twomastodons,a large bear-dog skull, and numerous 3-toedhorses for the American Museum of NaturalHistory in 1899 and 1901 (Gidley, 1903a). Lull

made a small collection for Yale University about1912. The University of California recovered asizable collection from several localities in theearly 19305. Works Progress Administration(WPA) crews under the supervision of C. StuartJohnston collected from several sites for West

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Figure 45. Gidley's 3-Toed Horse Quarry (late Clarendonian),DonleyCounty, Texas.

TexasState University and the Panhandle-PlainsHistorical Museum, Canyon, Texas. The largestcollections from the region were obtained bythe Frick Laboratory from about 1929 to 1960under the supervision of Will Chamberlain,C. H. Falkenbach, and N. Z. Ward. These mate-rials are now part of the American Museum ofNatural History collections. Midwestern StateUniversity at Wichita Falls, Texas, has a repre-sentative collection from several sites, and thereis a small collection at Harvard University.

The fauna from the Clarendon region (table 7)is dominated by medium to large grazing mam-mals. Perissodactyls are the most abundantorder and consist of a variety of pliohippine andhipparionine horses having hypsodont teeth andslender legs and ranging in size from a pony-sized Pliohippus down to the goat-sized Calippusregulus. Also present but rare is Hypohippus,last of the browsing horses. The Clarendonhorses have been described, discussed, andrevised in an extensive literature (Cope, 1893;Gidley, 1907; Osborn, 1918; Johnston, 1937d,1938; Stirton and Chamberlain, 1939; Quinn,1955; Webb, 1969a; Forsten, 1975; Skinner andMacFadden, 1977; MacFadden, 1980, 1984a;Webb and Hulbert, 1986; Hulbert, 1987, 1988).According to MacFadden (1984a), the MacAdamsQuarry (fig. 42, site 3) contains the largest fossilpopulation of Hipparion inNorth America; thereare more than 100 skulls from this quarry in

the Frick Collection of theAmerican Museum ofNatural History in NewYork City. Rhinocerosesare represented by Teleoceras, a short-legged,robust, hippolike amphibious variety with high-crowned teeth commonly found in stream-channel deposits on the Rowe-Lewis Ranch(fig. 42, sites 11 and 12) (Johnston, 1937a). Thisanimal probably lived around pools and marsheson the floodplains and grazed on adjacentgrasslands.

Artiodactyls, the second most abundant order,include a diversity of forms. Camel remains arefairly common, but the group is poorly knownand largely unstudied. Thereare several varietiesincluding large and small species of Procamelus,probably a grazer, and the giraffe-camel Aepy-camelus, a browser with a long neck and anestimated shoulder height of 3.5 m (11.5 ft)(Breyer, 1983; Webb, 1983a; Harrison, 1985).Less abundant but of considerable interest areseveral ruminants, including dromomerycids andmoschids (Frick, 1937), and protoceratids(Stirton, 1932; Frick, 1937; Patton and Taylor,1971, 1973). One of the most unusual animalsis Synthetoceras tricomatus,a protoceratid com-monly referred to as the "slingshot deer"becauseof its strange forked rostral horn in addition toits two strongly curved frontal horns. This "deer"was first reported by Stirton (1932) from theBromley Ranch (fig. 42, site 9), but it is alsoabundant at the MacAdams Quarry (fig. 42,

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Table 7. Composite fauna! list—ClarendonFauna, Donley County, Texas.

Class OsteichthyesOrder Semionotlformes

Family LepisosteidaeLepisosteus sp. - gar (Shannon and Bromley Ranches)

Class ReptiliaOrder Chelonia

Family TestudinidaeGeochelone sp. - large tortoise(Shannon, Bromley, and Rowe Ranches)Gopherus sp. - tortoise

Family TrionychidaeTrionyxsp. - soft-shell turtle (Shannon and Bromley Ranches)

Family EmydidaeEmydid sp. - unidentified pond or river turtles (Shannon, MacAdams, and Noble=Farr

Ranches)Order Crocodilia

Family CrocodilidaeAlligatorsp. - alligator(Shannon and Rowe Ranches)

Class Ayes

Order AnseriformesFamily Anatidae

Anatid sp. - goose (Noble=Farr Ranch)Class Mammalia

Order RodentiaFamily Mylagaulidae

Mylagaulussp. - burrowing rodent (Noble=Farr, Rowe Ranches)OrderCarnivora

Family NimravidaeBarbowofelis cf. B. whitfordi (Barbour and Cook) - small, short-legged saber-toothedcat

(Rowe Ranch Quarry7)Family Felidae

Pseudaelurug? sp. - cat (Adam Risley Ranch)Family Canidae

AelurodontaxoidesHatcher - large, wolflike dog (MacAdams Quarry; Grant, Noble=Farr,Bromley, Rowe Ranches)

Epicyon saevus (Leidy) - medium-sized dogTomarctus euthos (McGrew) - small dog (Noble=Farr, Rowe Ranches)

* Cynarctusfortidens Hall andDalquest - raccoonlike dog (holotype from Fair Ranch; alsoat AdamRisley and Rowe Ranches)

Family Amphicyonidae* Ischyrocyongidleyi(Matthew) - bear dog (holotype from Skillet Creek) (includes Hiocyon

walkeraeJohnston and Christian holotypefrom AdamRisleyRanch)Family Mustelidae

Brachypsalis sp. (Bromley Ranch)Leptarctus sp. (Noble=FarrRanch)Mionictis sp. (MacAdams Quarry)Sthenictis sp. (Shannon Ranch)

Order ProboscideaFamily Gomphotheriidae

Gomphotherium productus (Cope) (Bromley Ranch) (includes the holotype of G. serridensfrom Skillet Creek)

* Tetralophodonfricki Osborn (holotype from Rowe Ranch)

" " Holotype ofgenus* Holotypeofspecies

Class OsteichthyesOrder Semionotlformes

Family LepisosteidaeLepisosteus sp. - gar (Shannon and Bromley Ranches)

Class ReptiliaOrder Chelonia

Family TestudinidaeGeochelone sp. - large tortoise(Shannon, Bromley, and Rowe Ranches)Gopherus sp. - tortoise

Family TrionychidaeTrionyxsp. - soft-shell turtle (Shannon and Bromley Ranches)

Family EmydidaeEmydid sp. - unidentified pondor river turtles (Shannon, MacAdams, and Noble=Farr

Ranches)Order Crocodilia

Family CrocodilidaeAlligatorsp. - alligator(Shannon and Rowe Ranches)

Class AvesOrder Anseriformes

Family AnatidaeAnatid sp. - goose (Noble=Farr Ranch)

Class MammaliaOrder Rodentia

Family MylagaulidaeMylagaulussp. - burrowingrodent (Noble=Farr, Rowe Ranches)

OrderCarnivoraFamily Nimravidae

Barbowofelis cf. B. whitfordi (Barbour and Cook) - small, short-legged saber-toothedcat(Rowe Ranch Quarry 7)

Family FelidaePseudaelurusf? sp. - cat (Adam Risley Ranch)

Family CanidaeAelurodon taxoidesHatcher - large, wolflike dog (MacAdams Quarry; Grant, Noble=Farr,

Bromley, Rowe Ranches)Epicyon saeuus (Leidy) - medium-sized dogTomarctus euthos (McGrew) - small dog (Noble=Farr, Rowe Ranches)

* Cynarctus Jortidens Hall and Dalquest - raccoonlikedog (holotype from Fair Ranch; alsoat Adam Risley and Rowe Ranches)

Family Amphicyonidae* Ischyrocyongidleyi(Matthew) - bear dog (holotype from Skillet Creek) (includes Pliocyon

walkeraeJohnston and Christian holotypefrom AdamRisleyRanch)Family Mustelidae

Brachypsalis sp. (Bromley Ranch)Leptarctus sp. (Noble=FarrRanch)Mionictis sp. (MacAdams Quarry)Sthenictis sp. (Shannon Ranch)

Order ProboscideaFamily Gomphotheriidae

Gomphotherium productus (Cope) (Bromley Ranch) (includes the holotype of G. serridensfrom Skillet Creek)

* Tetralophodonfricki Osborn (holotype from Rowe Ranch)

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Table 7. (cont.)

Order ArtiodactylaFamily Tayassuidae

Prosthennops sp. - peccary (MacAdams Quarry; Noble=Farrand Rowe Ranches)Family Merycoidodontidae

Ustatochoerus prqfectus var. studeriSchultz and Falkenbach - oreodont (MacAdamsQuarry; Rowe Ranch)

Family CamelidaeAepycamelus sp. - giraffe camelProcamelus grandis Gregory - medium-sized camel (many localities)

* "Procamelus" leptognathusCope - small camel (holotype from Dilli or Charles RisleyRanch on Turkey Creek)

Protolabissp. - small camel?Hemiauchenia sp. - small llamalike camel

Family ProtoceratidaeParatoceras macadamsiFrick - horned ruminant (holotype from MacAdams Quarry)Synthetoceras tricornatus Stirton - horned ruminant (holotype from Bromley Ranch; also

at MacAdamsQuarry)Family Dromomerycidae

* Cranioceras clarendonensisFrick - horned deerlike ruminant (holotype from MacAdamsQuarry)

Family Moschidae* LongirostromeryxclarendonensisFrick - small ruminant (holotype from MacAdams

Quarry)Order Perissodactyla

Family EquidaeCalippus (Grammohippus)martini Hesse (many localities)Calippus {Calippus) placidus (Leidy) (Shannon Ranch)

* Calippus {Calippus) regulus Johnston (holotype from Grant Quarry; also at ShannonRanch)

Cormohipparion sphenodus (Cope) (earlyClarendonian from MacAdams Quarry)Cormohipparion occidentale(Leidy) (late Clarendonian from Gidley Horse Quarry)Hipparion tehonense (Merriam) (MacAdams Quarry)Neohipparionajfine (Leidy) (MacAdams Quarry)Pliohippus pemix Marsh (includes holotypes of Pliohippus Jossulatus Cope and Pliohippus

pachyops Cope fromDilli site onTurkeyCreek)Protohippus supremus Leidy

* Pseudhipparion hessei Webb and Hulbert (holotype from MacAdams Quarry)Hypohippus ajftnis Leidy - browsing horse (MacAdams Quarry; Grant and Rowe Ranches)

Family RhinocerotidaeTeleoceras cf. T. Jossiger (Cope) - short-legged hippolikerhinoceros?Aphelopssp. - rhinoceros

Order ArtiodactylaFamily Tayassuidae

Prosthennops sp. - peccary (MacAdams Quarry; Noble=Farrand Rowe Ranches)Family Merycoidodontidae

Ustatochoerus prqfectus var. studeriSchultz and Falkenbach - oreodont (MacAdamsQuarry; Rowe Ranch)

Family CamelidaeAepycamelus sp. - giraffe camelProcamelus grandis Gregory - medium-sizedcamel (many localities)

* "Procamelus" leptognathusCope - small camel (holotype from Dilli or Charles RisleyRanch on Turkey Creek)

Protolabis sp. - small camel?Hemiauchenia sp. - small llamalike camel

Family Protoceratidae** Paratoceras macadamsiFrick - horned ruminant (holotype from MacAdams Quarry)* * Synthetoceras tricornatus Stirton - horned ruminant (holotype from Bromley Ranch; also

at MacAdamsQuarry)Family Dromomerycidae

* Cranioceras clarendonensisFrick - horned deerlikeruminant (holotype from MacAdamsQuarry)

Family Moschidae* LongirostromeryxclarendonensisFrick - small ruminant (holotype from MacAdams

Quarry)Order Perissodactyla

Family EquidaeCalippus (Grammohippus) martini Hesse (many localities)Calippus {Calippus) placidus (Leidy) (Shannon Ranch)

* Calippus {Calippus} regulus Johnston (holotype from Grant Quarry; also at ShannonRanch)

Cormohipparion sphenodus (Cope) (earlyClarendonian from MacAdams Quarry)Cormohipparion occidentale(Leidy) (late Clarendonian from Gidley Horse Quarry)Hipparion tehonense (Merriam) (MacAdams Quarry)Neohipparionaffine (Leidy) (MacAdams Quarry)Pliohippuspemix Marsh (includes holotypes of Pliohippusfossulatus Cope and Pliohippus

pachyops Cope fromDilli site onTurkeyCreek)Protohippus supremus Leidy

* Pseudhipparion hessei Webb and Hulbert (holotype from MacAdams Quarry)Hypohippus ajftnis Leidy - browsing horse (MacAdams Quarry; Grant and Rowe Ranches)

Family RhinocerotidaeTeleocerascf. T. fossiger (Cope) - short-legged hippolikerhinoceros?Aphelopssp. - rhinoceros

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site 3) (Patton and Taylor, 1971). Although it isnot known from the northern Great Plains, ithas been reported from the early ClarendonianLapara Creek Fauna of the Texas Gulf CoastalPlain and from the early Hemphillian McGeheeLocal Fauna of Florida (Patton andTaylor, 1971).Other, relatively rare artiodactyls in the faunainclude Cranioceras, a giraffelikehorned brows-ingruminant; Longirostromeryx, a small chevro-tainlike ruminant; Ustatochoerus, one of the lastoreodonts (Schultz and Falkenbach, 1941); andthe peccary Prosthennops. The oreodont andpeccary, as well as some of the camels andruminants, were probably mixed feeders that,together with browsers such as Aepycamelus,Hypohippus, Cranioceras, and gomphotheres,inhabited the wooded areas along streams. Theywere rarely fossilized (Webb and others, 1981;Webb, 1983a).

Other mammalian orders are less abundantin the fauna. Proboscideans arerepresented byseveral skulls, jaws, and teeth of sublongiro-strine gomphothere mastodons (Cope, 1884,1889, 1893; Frick, 1933; Osborn, 1936). Car-nivores include several reported skulls and jawsof Ischyrocyon, a bone-crushing, carrion-eatingbear dog (Matthew, 1902; Johnston andChristian, 1941; Webb, 1969a); a raccoonlikedog, Cynarctus (Hall and Dalquest, 1962); pluslargely undescribed felids (Baskin, 1981,p. 131),mustelids (Harrison, 1981, p. 25), and canids,including Aelurodon, a hyenalike dog, andEpicyon, a wolflike predator. Small mammalsare conspicuously absent, although rodents arerepresented by the genus Mylagaulus.

Lower vertebrates are represented by largeland tortoises (Dalquest, 1962) and aquaticturtles, alligators, and gar fish. A few bird bones,such as goose, have been found.

In summary, thefauna seems to be dominatedby hypsodont (high tooth-crowned)grazers, somemixed feeders, and a few browsers and preda-tors. Lower vertebrates are mainly aquatic forms.

Paleoecology and ClimateSedimentological and faunal evidence suggests

that the habitat of the Clarendon Fauna wasprimarily a stream-border environment domi-nated by medium to large grazing mammals.Occasionallyhigh-energyflow or flood conditionsoccurred, as indicated by coarse channel depos-its, broken, waterworn bone fragments in thechannels, and thinly bedded overbank deposits.As a rule, however, quiet-water flow prevailed.

Adjacent to the streams were broad, grass-covered floodplains and scattered marshes,ponds, and oxbow or floodplain lakes in whichfossils accumulated. Deciduous trees grewmainly along stream borders, but the habitat isbest considered a parkland savanna.As a resultof salt dissolution in the Permian red beds inthe subsurface, sinkholes developed locallywhere overlying sediments collapsed. These sink-holes served as waterholes but became death-traps for the animals.

The climate of the region during Clarendoniantime probably was mild, subhumid, and some-what subtropical as indicated by the browsinggomphotheres and by the lowland, floodplain-dwelling, amphibious rhinoceros Teleoceras. Thepresence of alligators implies the existence ofwarm temperatures, permanent water, and suf-ficient vegetation for their nests. Permanent freshwater is also indicated by aquatic turtles andthe garLepisosteus. The presence of large landtortoises suggests mild winters (Hibbard, 1960).

Floral evidence from the Clarendon area islimited but supports theclimatic model providedby the vertebrates. Cottonwood leaf impres-sions were collected by the author from the LeafHills on the Rowe-Lewis Ranch. From the oldShannon Ranch (fig. 42, site 1) northwest ofGoldston, Stirton collected several palm seedsas well as a seed of Arctostaphylos (bearberry)and some wood of the ash tree Fraxinus. Thesewere reported by Chancy and Elias (1936, p. 13),who also described several other late Tertiaryfloras from the Great Plains. Comparing thelimited Clarendon flora with the extensive onefrom theLaverne (=Beaver) assemblage inBeaverCounty, Oklahoma, 217 km (135 mi) farthernorth (fig. 41, site 1), they concluded that theclimate of the Clarendon region was somewhatwarmer and less humid than that of theOklahoma Panhandle during Clarendonian time.

Hibbard (1960, p. 13), considering all availableevidence from late Tertiary faunas and floras ofthe interior Great Plains, concluded that "themajority of the areafrom southern South Dakotato Texas was a moist, subhumid, subtropicalsavanna with forests and tall grasses along theriver valleys, with chiefly shrubs and tall grasseson the valley walls and on the low divides. Someshort grasses may have occurred on the higherand well-drained divides." More recent studiesindicate drier conditions for the southernGreat Plains than the ones proposed by Hibbard(1960). Webb, largely on the basis of the ungu-late fauna, characterized the environment ofthe Great Plains during late Miocene time as a

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woodland savanna similar to that of centralAfrica today (Webb, 1977, 1983a).

The ClarendonianChronofauna

The Clarendon Fauna is representative ofwhat has been termed the Clarendonian chrono-fauna (Webb, 1969a, 1977, 1983a; Tedford,1970). It is a coherent association of species

lineages dominated by ungulates that emergedin North America during the late BarstovianLand Mammal Age, about 15 Ma ago, reachedits peak in the Clarendonian, and declined bythe end of the Hemphillian, around 5 Ma ago.The rise and fall of this late Miocene chrono-fauna apparently were controlled by a lateCenozoic trend toward cooler and drier climatesat temperate latitudes (Webb, 1983a). As forestbiomes gave way to parkland savanna, theabundance and diversity of ungulates and theratio of grazers to browsers increased. Later,the trend toward increasing aridity and thespread of steppe conditions led first to theextinction of virtually all browsers, then to thedecimation of grazers, and finallyto the whole-sale destruction of the chronofauna by the endof Hemphillian time. Hemphillian faunas, espe-cially later ones, show a marked decrease indiversity compared with the Clarendonianfaunas. There is a remarkable resemblance be-tween the late Miocene ungulate fauna of NorthAmerica and the Recent ungulate fauna of theAfrican savanna despite their entirely indepen-dent origins (Webb, 1983a).

Exell Local Fauna (=Frick's4-Way Locality)

The Exell Local Fauna is a small Clarendonianfauna reported by Dalquest and Hughes (1966)from ahigh cutbank in the headwaters of SouthPlum Creek, 6.4 km (4 mi) east-northeast of thecommunity of Exell in Moore County, Texas(fig. 41, site 2), about 56 km (35 mi) north ofAmarillo in the SW 1/4, sec. 2, Blk. B-26, E. L.and R. R. Ry. Co. Survey. Here the creek hascut into the flanks of several small hills to forma cliff or cutbank 3 to 9 m (10 to 30 ft) highand about 360 m (1,200 ft) long. The exposedrocks include massive sandstones and laminatedsandstones and shales varying in color fromgray torusset to yellowish brown. The nature of

the strata and thewaterworn condition of mostof the bones indicate a stream-channel andfloodplain environment.

The fossils are well preserved and consistmainly of waterworn bone fragments, isolatedteeth, and a few jawfragments of several generaof horses, including Pseudhipparion, Cormohip-parion, Pliohippus, and Calippus. Other mam-mals represented by one or two lower jawseachinclude the hyenoid dog Aelurodon; a peccary,Prosthennops; an oreodont, Ustatochoems; asmall ruminant, Longirostromeryx; and a rhinoc-erosreferred to the genus Peraceras. Other fos-sils include remains of toads and large and smallturtles and a number of sandstone casts ofcamel tracks that have come loose from theunderside of one of the beds. Collections fromthe site havebeen made by the Panhandle-PlainsHistorical Museum, by West Texas StateUniversity, and by the Frick Laboratory.

Coetas Creek FaunaThe Coetas Creek Fauna, an assemblage of

Clarendonian-age vertebrates,was collected froma small area south of the Canadian River ineast Potter County 32 km (20 mi) northeast ofAmarillo (fig. 41, site 3). Fossils are found inwhat was described by Patton (1923, p. 80) asthe Coetas Formation, a unit composed ofslightly consolidated sands and flaggy, sandylacustrine limestone that caps the high dividesand dips into the valleys of Coetas, Chicken,and Bonita Creeks. Beneath the Coetas For-mation lies the Potter Formation, a unit ofcoarse, partly consolidated sands and gravelslocally cemented with calcium carbonate (Patton,1923, p. 78). Both formations canbe consideredfacies of, or, at best, members of the OgallalaFormation. No vertebrates have been reportedfrom the Potter sands and gravels, but Patton(1923, p. 83) reported Hipparion teeth from theCoetas. During the early 19305, the Universityof California obtained a small collection fromthe area (Bivins Ranch Locality V-3103), and inthe late 19305, the Frick Laboratory collecteda small but varied fauna including the holotypespecimens of two oreodonts, Ustatochoerus pro-Jectus studeri and 17. major texanus (Schultz andFalkenbach, 1941). More recent collectionshavebeen made by West Texas State University.The largely undescribed fauna consists of oreo-donts, camels, small antilocaprids, peccaries,gomphotheres, several horses, including Pliohip-pus, Cormohipparion, and Pseudhipparion, rhi-

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noceroses, fellds, canids, shore birds, tortoises,and small turtles. The geology of the area wasdescribedby Wilson (1988).

Laverne (=Beaver) LocalFauna

The Laverne (=Beaver) Local Fauna is aClarendonian fauna identified originally (Hesse,1936a) in several localities on the south side ofthe Beaver River about 14.5km (9 mi) east and4.8 km (3 mi) south of Beaver, Beaver County,Oklahoma (fig. 41, site 1). The fossiliferous bedslie in the "Laverne member" of the Ogallala For-mation (Schoff, 1956). They first came to theattention of paleontologists in the 1890's whenfossil leaves,diatoms, and afew vertebrateswerecollected by Cragin (1891) and Case (1894) fromnorthwest-dipping beds of diatomaceous marlon the east bank of Gyp Creek, a north-drainingtributary of the Beaver River. The Beaver florawas described by Berry (1918) and Chancy andElias (1936). Fossil fish remains are found inthe diatomaceous marls, and fossil mammalswere collected by the University of California inthe 1930's and by the University of Kansas inthe 1930's and 1940's from gray sandy claysabove and below the marls. The sediments weredeposited in lakes and ponds and acquired theirnorthwest dip as a result of local structural col-lapse or subsidence brought on by subsurfacesalt dissolution in the underlying Permian redbeds. Among the more significant vertebrate dis-coveries are the type specimens of the beaverEucastorplanus (Stirton, 1935), the horse Calip-pus martini (Hesse, 1936a), and the turtle Chry-semys limnodytes (Galbreath, 1948), as well asahorn core of the antilocaprid Cosoryx(Hibbard,1951). Newer localities about 26 km (16 mi)farther east have yielded fossil fish (Smith,1962), an alligator (Woodburne, 1959), and mol-lusks (Leonard and Franzen, 1944;Taylor, 1954;Herrington and Taylor, 1958) now in the Uni-versity of Michigan collections. More recentlythe Laverne horses were discussed by Webb(1969a).

The flora described by Chancy and Elias(1936) includes box elder, ash, hackberry, per-simmon, sycamore, cottonwood, willow, and elm,as well as cattails and sedges. This variety sug-gests a grassy floodplain environment with treesconfined to the stream borders. The cattails andsedges grew in lakes or ponds on the floodplain.Modern equivalents of the arboreal species live

incentral to eastern Oklahoma, 290 km (180 mi)or more to the east, where the annual precipi-tation exceeds 76 cm (30 inches). The annualprecipitation in the Beaver area of the OklahomaPanhandle probably was about 76 to 89 cm (30to 35 inches) and probably was concentratedduring the warmer months, judging from theabsence of oak and evergreen trees in the fossilflora. The temperature may havebeen somewhatwarmer than now. The present annual precipi-tation is about 48 to 51 cm (19 to 20 inches),and the mean annual temperature is 14°C(57°F)(0rt0n,1964).

Durham Local FaunaThe Durham Local Fauna is a relatively lim-

ited fauna of late Clarendonian age from alocality 3.2 km (2 mi) northwest of the com-munity of Durham south of the Canadian Riverin the center, SE 1/4, sec. 15, T. 16 N, R. 26 W,Roger Mills County, Oklahoma (fig. 41, site 10).The site was discovered by David Kitts of theUniversity of Oklahoma in 1955 and was workedby that institution the following year.

The geology of Roger Mills County was dis-cussed by Kitts (1959), and the fauna wasdescribed by Kitts and Black (1959), with anadditional description of Aelurodon made laterbyKitts (1964). The fauna includes isolated teethof Pseudhipparion and other horses. Mylagaulusis represented by several teeth and some limbbone fragments. Most of the remaining taxaareknown from jaw fragments and include camel,antilocaprid, oreodont, rodent, and several car-nivores. Remains of turtle and snake are alsoknown.

Kitts and Black (1959, p. 27-30) stated thatthe strata from which the fossils wereobtainedare exposed in ablowout whichis about 5,000 square yards in area . . .along the east bank of an intermittentstream which drains north into the SouthCanadian River at a point about twomiles distant. . . . The fossils . . .are contained in two beds, a lower buffsand and lying directly above it a cross-bedded channel sand. Thecontained fos-sils do not reveal any age difference inthe two beds. . . . The lower bone-bearing bed consists of reddish-buff,fine- to medium-grained massive sandcontaining calcium carbonate concre-tions. The deposit is probably offloodplain origin. The abundance of

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concretions and the lack of beddingindicate that for a prolonged period inits history the deposit was located at ornear the surface and subjected toweathering. The fossil bone recoveredfrom this layer is poorly pre-served. . . . The upper bone-bearingbed, which lies unconformably on thebuff sand layer, consists of uncemented,crossbedded sand. The sand grains varyin size between fine and very coarse. Thedeposit contains lenses of clay and clayballs and is locally iron-stained . . . thefossils are rather evenly and sparselydistributed throughout much of thedeposit. Almost all of thebone occurs assmall fragments which showevidence ofhaving been transported over a con-siderable distance. About 10 percent ofthe fossils recovered from this depositwere found in place, the remainderhaving been picked up on the surface.The channel in which the sand was

deposited apparently trended east andwest since the degree of crossbeddingdecreases and the material becomes finerto the north and south. The channelmust have been over a hundred feet inwidth since the deposits are exposed overan area about 100 by 150 feet.

Cole Highway Pit FaunaThe Cole Highway Pit Fauna was recovered

from a crossbedded sand and gravel depositexposed just south of Commission Creekon theeast side of FM 1453 about 6.4 km (4 mi) southof Higgins, Lipscomb County, Texas (fig. 46,site 1). The site was quarried by the FrickLaboratory and yielded a limited late Claren-donian or early Hemphillian fauna (unpub-lished). Fossils at West Texas State Universityinclude tortoise, gomphothere, camel, horse,rhinoceros, and a mylagaulid lower jaw.

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Figure 46. Location of principal late Clarendonianandearly Hemphillianfaunal sites in Lipscomb County,Texas, and Ellis County, Oklahoma. Late Clarendonian: (1) Cole Highway Pit. Early Hemphillian: (2)Higgins (Sebits Ranch Locality 24-A), (3) Higgins (Sebits Ranch Locality 24-B), (4) Amett (University ofOklahomaAdair Ranch Quarry and Frick Laboratory Port-of-Entry Pit), (5) Capps=Neu=Pratt Quarries, (6)V. V. Parker Pits, (7) Box T (Pit 1). Unpublished locality information courtesy of R. H. Tedford and M. F.Skinner, American Museum of NaturalHistory.

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Stop 15: Early Hemphillian Faunas of theTexas and Oklahoma PanhandlesG. E. Schultz

Early Hemphillian faunas include the Capps=Neu=Pratt Pits Fauna, the Arnett (=Port-of-Entry Pit)Local Fauna ofEllis County, Oklahoma, and the Higgins (=Sebits Ranch) Local Fauna, V. V. ParkerPits Fauna, and the Box TLocalFauna ofLipscomb County, Texas. Thesefaunas suggest thepresenceofparkland or woodland savanna.

Capps=Neu=Pratt Pits FaunaSeveral shallow excavations were made by

the Frick Laboratory in greenish-gray toyellowish-brown clays and silts of an old lakebed. These beds are exposed on the dividebetween Corn Creek and West Hog Creek about3.2 km (2 mi) north of Lake Vincent, 4.8 km(3 mi) south of U.S. Highway 60, and 6.4 km(4 mi) east of the Texas-Oklahoma state line inEllis County, Oklahoma (fig. 46, site 5). Thefossil-bearing zone lies low in the local Ogallalasection and has produced an earliest Hemp-hillian fauna of completely articulated skeletonsand partial remains ofhorses such as Pliohippus(R. H. Tedford, personal communication, 1977)and Neohipparion leptode (MacFadden, 1984a,p. 102) and remains of camels such as Aepy-camelus, Procamelus, Hemiauchenia, and Mega-tylopus (Breyer, 1983). Although it has notbeen published, the fauna apparently is olderthan that of Port-of-Entry Pit, Sebits Ranch(=Higgins), or V. V. Parker Pits (fig. 46). A partiallist is given in table 8.

Arnett Local Fauna(=University of OklahomaAdairRanch Quarry and theFrick Laboratory Port-of-Entry Pit)

The Arnett Local Fauna (Kitts, 1957, 1965) isan early Hemphillian fauna collected by theUniversity of Oklahoma during the 19305, 1955,and 1956.The site is located on the L. H. AdairRanch, 4 km (2.5 mi) east of the Texas-Oklahoma state line and 16km (10 mi) west ofthe town ofArnett in the NW 1/4, NW 1/4, sec.14, T. 19 N, R. 26 W, Ellis County, Oklahoma

(fig. 41, site 11; fig. 46, site 4). Excavationsextend for several hundred feet along the eastwall of a small canyon, East Branch of CornCreek, which drains south into the valley of theSouth Canadian River. The Frick LaboratoryPort-of-Entry Pit is a continuation of the samedeposit, extending for several hundred yardsalong the east wall of the canyon in the south-west quarter of the same quarter section. The"Hopewell fauna" of Hesse (1936a, p. 68) isprobably synonymous with the Arnett LocalFauna, because the old Hopewell schoolhousewas only a mile or two from theArnett locality.

Kitts (1957, p. 7) stated thatthe section at Arnett consists of un-consolidated fine clayey and silty sandsand layers of calcareous "caliche" or"mortar beds" which contain largeamounts of fine sand. There are nocoarse channel sands or gravels exposedin the area, the coarsest material beinga few well rounded caliche fragments ofpebble size contained in the sands. Thesands were presumably deposited inlakes or upon floodplains. The calichesare probably of secondary origin.

The fossils are sparsely distributedin a bed of fine clayey, silty sand aboutthree feet in thickness. The bones arewell mineralized and are hard. All of thespecimens are fragmentary and thebroken edges are sharp. No articulatedspecimens were found. After the softparts had decomposed, the bones wereapparently broken and scattered, per-haps by carnivores and scavengers. It ispossible that thebones were transporteda short distance and deposited in pondsor playa lakes.

Deposits which accumulated in themanner suggested above would certainlynot contain the remains of a represen-

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Figure 47. Early HemphilHan Frick Laboratory Port-of-Entry Pit(=Arnett Local Fauna), Ellis County, Oklahoma. Fossils are present atbase of exposedsection. Note thinwhitevolcanic ash layer markedbyarrow inmidsection.

tative sample of the fauna living in thearea at the time. Mastodonts and largecarnivores are by far the most abundantfaunal elements preserved, a fact whichsuggests that the carnivoreswere preyingupon the mastodonts or, particularly inthe case of the hyaenoid dogs, feedingupon the carcasses of mastodonts whichhad died on the flood plain.

There is a striking scarcity of limbbones in the collection, which may beat least partly the result of selectivecollecting.

At some places a thin calcareous layeroverlies the bone-containing sand, anditselfcontains bone. Where the thin layerof caliche is absent, the base of themassive caliche layer contains bone,which is in some instances surroundedby a thin layer of unconsolidated sand.These facts strongly suggest that thecaliche is of secondary origin.

The geologic profile at the Port-of-Entry Pit(fig. 47) is similar to that given by Kitts (1957,p. 6) for the Adair Ranch Quarry. Fossils arefound at the base of a 1.2-m-thick (4-ft) graycaliche-cemented sandstone. This is overlainby about 2 m (7 ft) of fine, loosely consolidatedbrown sand containing a 15-cm-thick (6-inch)

bed of white to bluish-gray volcanic ash about0.6 m (2 ft) from the base. This ash, which hasnot been dated, also lies above the fossiliferousbeds in the Adair Ranch Quarry but was notmentioned by Kitts. Capping the Port-of-EntryPit strata is a 30-cm-thick (1 -ft) gray caliche-cemented sandstone. The slopes above bothquarriesfor about 12 m (40 ft) are mostly grass-covered, gray to tan unconsolidated sands andsilts. The canyon rim, however, is composed of1.5 to 2.4 m (5 to 8 ft) of tan sandy caliche,which weathers into prominent, resistant ledgesalong most of the valleys in the region.

Among the most interesting elements in thefauna (table 8) are the remains of carnivores,which include lower jaws and other skeletalparts of the large pseudaelurin cat, Nimravidescf. N. thinobates (Kitts, 1958; Martin andSchultz, 1975; Baskin, 1981). This long-leggedpredator probably pursued its prey in opencountry and may have been a scavenger as well(Webb and others, 1981). Also present is theprimitive, short-legged, saber-toothed catlikecarnivore, Barhowofelis lovei (Baskin, 1981){=uAlbanosmilus? sp." of Kitts, 1957), inter-mediate in size between the smaller B. morrisifrom thelate ClarendonianAsh Hollow Formationof Nebraska and the larger B. fricki from thelate earlyHemphillian CambridgeLocal Faunaof

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Table 8. Faunal lists of the early Hemphillian chronofaunal sequence of local faunas in theTexas Panhandle and adjacent Oklahoma.

A B C DClass Reptilia

Order CheloniaFamily Testudinidae

Geochelonesp. - large tortoise ? X XGopherus sp. - tortoise ? ? X ?Small pond orriver turtle ? X

OrderSquamataFamily Boidae

CharinaprebottaeBrattstrom - extinct boa XFamily Colubridae

Paleoheterodon tiheniHolman - extinct hog-nosed snake XMiocoluber dalquestiParmley - extinct racer * *Coluberor Masticophis - racer or coachwhip XThamnophiscf. T. sirtalis (Linnaeus) or T. proximus (Say) -

extinct gartersnake XClass Mammalia

Order ChiropteraFamily Vespertilionidae

PizonyxwheeleriDalquest and Patrick - bat *Order Edentata

Family MegalonychidaePliometanastes cf. P. prottstus Hirschfeld and

Webb - ground sloth XMegalonychidsp. - groundsloth X

Family MylodontidaeThinobadistes wetzeliWebb - ground sloth X

Order RodentiaFamily Mylagaulidae

Mylagaulussp. - burrowing rodent XFamily Eomyidae

Kansasimys dubiusWood Xundetermined genusand species X

Family SciuridaeSpermophilussp. - ground squirrel X

Family GeomyidaePliosaccomys higginsensisDalquest and Patrick - pocket gopher *

Family HeteromyidaePerognathus sp. - pocket mouse X

** Holotype ofgenus* Holotypeof species

X Occurrence in fauna? Possible occurrence in faunaA Capps=Neu=Pratt Pits Local Fauna (Early early Hemphillian—list incompleteB Port-of-Entry Pit=Arnett Local FaunaC Higgins=SebitsRanch Local FaunaD Box T Local Fauna (Late early Hemphillian)

A and B are in Ellis County, Oklahoma. C and D arein LipscombCounty, Texas.

A B C DClass Reptilia

Order CheloniaFamily Testudinidae

Geochelonesp. - large tortoise ? X XGopherus sp. - tortoiseSmall pond orriver turtle

??

? X ?X

OrderSquamataFamily Boidae

CharinaprebottaeBrattstrom - extinct boa XFamily Colubridae

Paleoheterodon tiheniHolman - extinct hog-nosed snake XMiocoluber dalquestiParmley - extinct racer **Coluberor Masticophis - racer or coachwhip XThamnophiscf. T. sirtalis (Linnaeus) or T. proximus (Say) -

extinct gartersnake XClass Mammalia

Order ChiropteraFamily Vespertilionidae

PizonyxwheeleriDalquest and Patrick - bat *OrderEdentata

Family MegalonychidaePliometanastescf. P. prottstus Hirschfeld and

Webb - ground sloth XMegalonychidsp. - ground sloth X

Family MylodontidaeThinobadistes wetzeliWebb - groundsloth X

Order RodentiaFamily Mylagaulidae

Mylagaulussp. - burrowingrodent XFamily Eomyidae

Kansasimys dubiusWood Xundetermined genus and species X

Family SciuridaeSpermophilussp. - ground squirrel X

Family GeomyidaePliosaccomys higginsensisDalquest and Patrick - pocket gopher *

Family HeteromyidaePerognathus sp. - pocket mouse X

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Table 8. (cont.)

A B C DOrder Lagomorpha

Family LeporidaeHypolagus vetus (Kellogg) - rabbit X

Order CarnivoraFamily Nimravidae

BarbourofeUs lovei Baskin {=uAlbanosmilus"ofKitts, 1957) - short-leggedsaber-toothed catlike carnivore X

Family FelidaeNimravides cf. N. thinobates (Macdonald)

(=JV. catocopis [Cope] ofBurt [ 1931] -cat) XXXMachairodus sp. - saber-toothedcat X

Family CanidaeEpicyon validus (Matthewand Cook) - large dog XXXEpicyon mortifer (Cook) - large dog XOsteoborus sp. - large bone-eating dog X XOsteoborussp. (small O. cyonoidesofHesse [1940]) XOsteoborus cf. O. pugnator (Cook) - bone-eating

dog XFamily Mustelidae

Eomellivorasp. XLeptarctus sp. XSthenictis sp. X

Family UrsidaeIndarctos sp. - large bear X

Order ProboscideaFamily Gomphotheriidae

Gomphotheriumor Amebelodonsp. X XAmebelodon hicksi (Cook) - long-jawed form XAmebelodon cf. A. JHckiBarbour - shovel tusker X

Order ArtiodactylaFamily Tayassuidae

Prosthennops sp. - peccary XProsthennops [Macrogenis) grqffhami Schultz and

Martin - peccary XFamily Camelidae

Aepycamelussp. - giraffe camel X XProcamelus sp. - medium-sized camel XX XMegatylopussp. - large camel X X X XHemiaucheniasp. {=Pliauchenia of Hesse

[1940]) - llamalikecamel X X X XFamily Dromomerycidae

Pediomeryx {Yumaceras) cf. P. jigginsi (Frick) -giraffelike horned ruminant XXX

Family GelocidaePseudoceras sp. - small hornless ruminant X

Family AntilocapridaeAntilocaprinesp. - pronghorn XXXPlioceros or Texoceros sp. - pronghorn XOsbornocerosl? sp. - pronghorn X

A B c DOrder Lagomorpha

Family LeporidaeHypolagtis vetus (Kellogg) - rabbit X

Order CarnivoraFamily Nimravidae

BarbourofeUs lovei Baskin {="Albanosmilus"ofKitts, 1957) - short-leggedsaber-toothedcatlike carnivore X

Family FelidaeNimravides cf. N. thinobates (Macdonald)

(=JV. catocopis [Cope] ofBurt [1931] - cat) X X XMachairodus sp. - saber-toothed cat X

Family CanidaeEpicyon validus (Matthewand Cook) - large dog X X XEpicyon mortifer (Cook) - large dog XOsteoborus sp. - large bone-eating dogOsteoborussp. (small O. cyonoidesofHesse [1940])Osteoborus cf. O. pugnator (Cook) - bone-eating

XX

X

dog XFamily Mustelidae

Eomellivorasp. XLeptarctus sp.Sthenictis sp.

XX

Family UrsidaeIndarctos sp. - large bear X

Order ProboscideaFamily Gomphotheriidae

Gomphotheriumor Amebelodon sp.Amebelodon hlcksi (Cook) - long-jawed form

X XX

Amebelodon cf. A.fricki Barbour - shovel tusker XOrder Artiodactyla

Family TayassuidaeProsthennops sp. - peccaryProsthennops (Macrogenis) graffhami Schultz and

X

Martin - peccary XFamily Camelidae

Aepycamekissp. - giraffe camel X XProcamelus sp. - medium-sized camel X X XMegatylopussp. - large camelHemiauchenia sp. {=Pliauchenia of Hesse

X X X X

[1940]) - llamalike camel X X X XFamily Dromomerycidae

Pediomeryx {Yumaceras) cf. P. Jigginsi (Frick) -giraffelike horned ruminant X X X

Family GelocidaePseudoceras sp. - small hornless ruminant X

Family AntilocapridaeAntilocaprinesp. - pronghorn X X XPlioceros or Texoceros sp. - pronghorn XOsbornoceros? sp. - pronghorn X

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Table 8. (cont.)

A B C DOrder Perissodactyla

Family EquidaeAstrohippus sp. - 1-toedhorse XCalippus sp. - small 1-toed horse XCormohipparioncf. C. occidentale (Leidy) XXXHipparionsp. - 3-toed horse X XHipparionJorcei Richey - 3-toed horse XNeohipparion leptodeMerriam - 3-toed horse X X ? XPliohippussp. - 1-toed horse X X X XPseudhipparionsp. - small 3-toed horse ?

Family RhinocerotidaeAphelops malacorhinusCope - rhinoceros XAphelops sp. - rhinoceros X XTeleoceras cf. T. Jossiger (Cope) - short-legged

hippolike rhinoceros X ?

Nebraska (Schultz and others, 1970).This short-legged carnivore probably ambushed largeungulates from deep cover (Webb and others,1981). Canids include the large, massive-jawed

Epicyon validus and a smaller hyenoid dog,Epicyon mortifer (Kitts, 1957). The latter is char-acterized by reduced but uncrowded premolars,which retain their accessory cusps.

The Arnett Local Fauna includes taxa thatare similar or closely related to those in thenearby Higgins (=Sebits Ranch) Local Fauna inLipscomb County, Texas, 4.8 km (3 mi)southwest of the Arnett locality (for example,Nimravides,Epicyon validus,Pediomeryx [Yuma-ceras], and Aphelops) (fig. 46, sites 2 and 3).However, at the Sebits Ranch localities, Bar-bourofelis and Epicyon mortifer are absent,whereas Osteoborus makes its first appearancein the southern Great Plains, represented hereby a large and a small species (R. H. Tedford,personal communication, 1977). According toBaskin (1980), Osteoborus evolved from a smallspecies of Epicyon {saevus group) in the earlyHemphillian, whereas the genus Aelurodonbecame extinct at the end of the Clarendonian.

The gomphothere in the Arnett Local Faunahas lower incisors that are narrower thanthose of Amebelodon hicksi from Sebits Ranch.

The Arnett gomphothere may be similar tothe narrow-tusked species from the lateClarendonian Love Bone Bed of Florida, whichWebb and others (1981) referred to Amebelodoncf. A. barbourensis. It possibly represents anundescribed species of Gomphotherium.

Among the ungulates, antilocaprines appearfor the first time in the southern Great Plainsin the Arnett Local Fauna and are present atSebits Ranch. The camel genera Aepycamelusand Procamelus make their last local appearanceat the Amett site and are absent at SebitsRanch (R. H. Tedford, personal communication,1977; Tedford and others, 1987), althoughBreyer (1983) assigned to Procamelus ametatarsal from the younger Box TLocal Fauna.Horses arenot abundant in either the Arnett orHiggins (=Sebits Ranch) Local Faunas butinclude Pliohippus, Cormohipparion, andNeohipparion leptode (Hulbert, 1987).

Stratigraphic evidence suggests that theArnett Local Fauna is slightly older than theHiggins (=Sebits Ranch) Local Fauna. The inter-mediate size ofBarbourqfelis lovei compared withthat of B. morrisi and B. fricki of Nebraska sug-gests that the Arnett Local Fauna is youngerthan late Clarendonian and older than late earlyHemphillian and is therefore early Hemphillian—

A B C DOrder Perissodactyla

Family EquidaeAstrohippus sp. - 1-toedhorse XCalippus sp. - small 1-toed horse XCormohipparioncf. C. occidentale (Leidy) X X XHipparionsp. - 3-toed horseHipparionJorcei Richey - 3-toed horseNeohipparion leptodeMerriam - 3-toed horse X

X

X

X

?XX

Pliohippussp. - 1-toed horse X X X XPseudhipparionsp. - small 3-toed horse ?

Family RhinocerotidaeAphelops malacorhinusCope - rhinoceros XAphelops sp. - rhinoceros X XTeleoceras cf. T. Jossiger (Cope) - short-legged

hippolike rhinoceros X ?

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Figure 48. Ogallala Formation mortar beds outcrop in Sleepy Hollowwest of Sebits Ranch Locality 24-B (fig. 46, site 3) near Higgins,Lipscomb County, Texas. Photo courtesyof Panhandle-Plains HistoricalMuseum, Canyon, Texas.

probably dating at about 7.5 Ma (table 8). Thepresence of Epicyon mortifer, Epicyon validus,Gomphotherium (or a primitive Amebelodon),thecamels Aepycamelus and Procamelus, as wellas the limited horse fauna, supports this ageassignment.

Higgins (=Sebits Ranch)Local Fauna

The Higgins (=Sebits Ranch) Local Fauna(early Hemphillian) is known from two localitieson the old Sebits Ranch southeast of Higgins,Lipscomb County, in the northeast corner ofthe Texas Panhandle (fig. 41, site 12; fig. 46,sites 2 and 3). The two sites were discovered in1928 by Reed and Longnecker (1932), whodesignated them Localities 24-A and 24-B.Locality 24-A is 2.4 km (1.5 mi) south and1.6km (1 mi) east of Higgins on the west sideof a south-draining tributary of CommissionCreek, 0.8 km (0.5 mi) west of the Oklahomastate line near the center, SE 1/4, NE 1/4,sec. 176, Blk. 43, Houston and Texas CentralRailroad Survey. Locality 24-B is 0.8km (0.5 mi)south of Locality 24-A on the south side ofSleepy Hollow, an east-draining tributary ofCommission Creek in the center, S 1/2, SE1/4, sec. 176, Blk. 43. Both sites lie at the

same stratigraphic level in gray, unconsolidatedto cemented fluvial sands that vary in thick-ness from 0.9 m (3 ft) at Locality 24-B to 1.8 m(6 ft) at Locality 24-A. The section is betterexposed at Locality 24-B (figs. 48 through 50)where the fossil bed is underlain by about 7 m(23 ft) of loose brown silty sand and calicheresting on a cemented brown sand, or mortarbed. The fossil bed is overlain by 1.8 m (6 ft) ofloose brown sand capped by another cementedbrown sand, or mortar bed about 3 m (10 ft)thick, which, at the quarry, lies 7.5 m (25 ft)below the upland surface. This upper cementedsand forms a prominent ledge along the sidesof the primarily grass-covered slopes of thevalleys in the region. Locally this ledge occursat or near the top of the valley walls, whereaselsewhere it slopes downward to crop out atlower elevations on the valley slopes. This ledgeis not the true Caprock caliche that occurs atthe top of the Ogallala Formation in the LlanoEstacado farther west. The areaaround Higginslies at a lower elevation in the breaks, or tran-sitional zone between the High Plains and theLow Rolling Plains. The Ogallala here is trun-cated. The mortar beds are highly cementedsandstones that are found at several differentlevels in the stratigraphic section in this area.

Fossils were first collected from the twoHiggins localities by Reed and Longnecker (1932)

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Figure 49. SebitsRanch Locality24-B (fig. 46, site 3) (earlyHemphillian)nearHiggins, Lipscomb County, Texas, in 1937. View to west showingexcavationof fossil bed. Photo courtesy of Panhandle-Plains HistoricalMuseum, Canyon, Texas.

Figure 50. Sebits Ranch Locality 24-B (fig. 46, site 3) in 1937. View toeast showing excavation of fossil bed. Photo courtesy of Panhandle-Plains Historical Museum, Canyon, Texas.

and by the University of California in 1928,1929, and 1930. Later collections were madeby the Panhandle-Plains Historical Museum ofCanyon, Texas, in the late 19305. The fossilsfrom the two localities are similarly preserved,incomplete, and frequently specifically indeter-

minate. The fauna (table 8) was described byHesse (1940). It is dominated by jaws andother skeletal elements of the rhinocerosAphelops (Matthew, 1932) and of the long-jawedgomphothere Amebelodorh Less common are car-nivores, including the large, massive-jawed

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canid, Epicyon validus (Johnston, 1939a; Webb,1969b; Richey, 1979) and the large pseudaelurincat tentatively referred to Machairodus by Burt(1931), but later shown to belong to the genusNimravides (Kitts, 1958; Martin and Schultz,1975). Horses and camels make up a smaller

part of the fauna. Of note is the earliest regionaloccurrence of a megalonychid sloth—its iden-tification based on a single tooth now in thePanhandle-Plains Historical Museum. The largetortoises were mentioned by Brattstrom (1961,p. 550). Five species of snakes (one new) weredescribed by Parmley (1988). A small micro-mammal fauna was reported by Dalquest andPatrick (1989).

The Higgins Local Fauna includes species thatare similar or closely related to species in thenearby Arnett Local Fauna in Ellis County,Oklahoma, 4.8 km (3 mi) northeast of theHiggins localities (for example, Nimravides,Epicyon validus, Pediomeryx [Yumaceras], andAphelops). However, the small canid in theHiggins Local Fauna identified by Hesse (1940)as Osteoborus cyonoides is absent from theArnett Local Fauna. A larger member of thesame genus has been identified from the Higginssite (R. H. Tedford, personal communication,1977). The gomphothere in the Higgins Local

Fauna is Amebelodon, whereas that in the ArnettLocal Fauna may bereferable to Gomphotherium.Stratigraphic evidence suggests that the HigginsLocal Fauna is slightly younger than theArnettLocal Fauna, although the fauna is still clearlyof early Hemphillian age, probably equivalent totheFeltz Ranch Local Fauna of Nebraska (Hesse,1935a) (table 1). The presence of Epicyon validusin the Arnett and Higgins Local Faunas indi-cates a correlation with part of the Upper SnakeCreek locale of Nebraska, which produced the"type" of that species.

V. V. Parker PitsSeveral exposures of gray silty sand lie along

the south valley wall of Wolf Creek about14.5 km (9 mi) north of Higgins, LipscombCounty, Texas (fig. 46, site 6). Some of theseexposures, which probably represent a singlechannel deposit, arefossiliferous and were quar-ried by the Frick Laboratory. The fauna (largelyunpublished) includes turtle, large cat, gompho-there, camel, small ruminant, rhinoceros, andseveral kinds of horse. MacFadden and Skinner(1979) described a lower jaw of the one-toedhorse Hippidion, the first North American record

of this South American genus. The fauna isearly Hemphillian and appears to correlate strat-igraphically with the fauna from the Arnett(=Port-of-Entry) site.

Box T Local FaunaThe Box T Local Fauna (table 8) is known

from several localities 1.6 km (1 mi) south ofWolf Creek on the Vester Smith Box T Ranch,approximately 14.5 km (9 mi) northwest ofHiggins, Lipscomb County, Texas (fig. 41, site13; fig. 46, site 7). The principal quarries arewest of theranch house in the SE 1/4, SE 1/4,sec. 611, Blk. 43, Houston and Texas CentralRailroad Survey. Fossils were collected by theFrick Laboratory from unconsolidated stream-channel sands containing abundant clasts ofscoriaceous basalt derived from the volcanichighlands of northeastern New Mexico. Theseclasts may represent the oldest basalts fromRaton-Clayton field, which have been dated atabout 7.2 Ma B.P. (Stormer, 1972), or theymaybe derived from the earliest eruptions in theOcate field west of Springer, New Mexico,whichhave been dated between 8.1 and 5.5 Ma B.P.(Nielsen and Dungan, 1985). The channel depos-its containing these clasts disconformably over-lie a massive cemented buff sandstone thatpresumably is equivalent to the brown sand, ormortar bed, overlying the bone-bearing beds atthe Higgins quarries. The fossiliferous beds atthe Box T quarriesare overlain by 9 to 10.5 m(30 to 35 ft) of rubbly buff sand locally cementedinto thin mortarbeds near the top (fig. 51).

The fauna is large (table 8), although it isundescribed except for the sloths Pliometanastescf. P. protistus (Hirschfeld and Webb, 1968,p. 284) and Thinobadistes wetzeli (Webb, 1989),and it is similar to the Higgins (=Sebits Ranch)Local Fauna because it contains Nimravides,Epicyon validus, Osteoborus (large and smallspecies), Amebelodon, Pediomeryx [Yumaceras),and Aphelops (R. H. Tedford, personal communi-cation, 1977). However, certaintaxacharacteristicof the Arnett or Higgins Local Faunas, such asBarbourqfelis, Epicyon mortifer, Aepycamelus,andpossibly Procamelus, are absent. Immigrantgenera, such as Machairodus, Indarctos, andEomellivora, appear for the first time (Tedfordand others, 1987), indicating that the fauna isyounger than the Higgins (=Sebits Ranch) LocalFauna and thusbelongs to the laterpart of theearly Hemphillian (table 8). The Box T LocalFauna probably dates between 6 and 7 Ma ago.

103

Figure 51. Box T Local Fauna Pit No. 1 (late early Hemphillian),Lipscomb County, Texas. Fossils arepresentatbase of exposedsectionof Ogallala sediments. Photo courtesy of Panhandle-Plains HistoricalMuseum, Canyon, Texas.

Whereas a complete description of the Box TLocal Fauna has not been published, many ofthe taxa present have been mentioned in theliterature, such as the immigrant ground sloths,Pltometanastes and Thinobadistes from SouthAmerica (Hirschfeld and Webb, 1968; Marshalland others, 1979; Webb, 1989); the giant bearIndarctos (Harrison, 1983, p. 25); the giraffelikebrowsing ruminant Pediomeryx [Yumaceras) cf.P.Jigginsi (Webb, 1983b); the camel Procamelus(Breyer, 1983); and the horses Hipparinn forcei(MacFadden, 1984a) and Neohipparion leptode(Hulbert, 1987). Breyer (1981) recorded thepresence of Osteoboms, Sthenictis, Prosthennopsgrqffhami, and Neohipparion leptode. The Box TLocal Fauna, despite the presence of new im-migrant genera and the absenceof certain oldertaxa, demonstrates the persistence of a Claren-donian chronofauna (Webb, 1969a).

The Box T Local Fauna is older and lower inthe Ogallala section than the late HemphillianCoffee Ranch Local Fauna (fig. 41, site 15) andcontains the last occurrence of Nimrauides, Lep-tarctus, Amebelodon cf. A. fricki, Calippus,Pliohippus, Pediomeryx {Yumaceras), and thestrange Clarendonian immigrant Pseudoceras,a small hornless ruminant of the gelocid family.

This fauna lacks, however, taxa that appear forthe first time in the Coffee Ranch and equivalentfaunas, such asRhynchotherium, Plesiogulo, andAgriotherium (Tedford and others, 1987). TheBox T Local Fauna correlates closely with oneof the "Kimball faunas" (Cambridge=Ft-40 LocalFauna) of Nebraska and with the Wray LocalFauna ofColorado, both ofwhich are consideredto be late early Hemphillian (Tedford and others,1987).

The climate in the Texas Panhandle duringthe time in which the Higgins and Box T LocalFaunas lived continued to be mild, and grass-land savanna conditions prevailed. The presenceof large tortoises suggests a frost-free environ-ment (Hibbard, 1960) and some mammals suchas the rhinoceroses {Aphelops and Teleoceras)and the shovel-tusked gomphothere Amebelodonbecame quite large and apparently fed on theabundant vegetation growing along broad grassyfloodplains of the larger river valleys. Amebelo-donprobably used its large lower tusks to shovelup succulent water plants and perhaps rootsand bulbs, as suggested by Osborn (1936,p. 333). A well-preserved lower jawof this gom-phothere is recorded from Roberts County, Texas(Gregory, 1945).

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Stop 16: Late Hemphillian Faunas of theTexas and Oklahoma PanhandlesG. E. Schultz

The Coffee Ranch and Goodnight Local Faunas ofTexas and the Optima Local Fauna ofOklahomaare dominated by mammals adapted to grazingon agrassland savanna or steppe.

Coffee Ranch (=Miami)Local Fauna

The Coffee Ranch Quarry, type locality forthe Hemphillian Land Mammal Age, is about13km (8 mi) northeast of Miami, 1.6km (1 mi)east of the Roberts-Hemphill county line andabout 150 m (500 ft) north of a county road inthe SE 1/4, NE 1/4, NE 1/4, sec. 59, Blk. A-2,H. and G. N. Ry. Co. Survey, Hemphill County,Texas (USGS Lora 7.5-minute topographicquadrangle map) (fig. 41, site 15; fig. 52). Thequarry is high in the Ogallala section, and the

fauna is thought to be of late Hemphillian age.The sitewas discoveredby Reed andLongneekerin 1928while they were investigating the geologyof Hemphill County for the Rio Bravo OilCompany (Reed and Longneeker, 1932). TheUniversity of California obtained specimens col-lected by them and made additional collectionsat the site from 1928 to 1930 (UCMP LocalityV-2823). The sitewas worked during the 1930'sby the Frick Laboratory, the Denver Museumof Natural History, and West Texas StateUniversity. In 1963 and 1964, Midwestern StateUniversity began extensive excavations thatincluded screenwashing matrix for microfauna.

Figure 52. U.S. Geological Survey topographic map (Lora, Texas, 7.5-minute quadrangle) of Coffee RanchQuarry (type Hemphillian), Hemphill County, Texas. Quarry at gravel pit marked??. Scale 1:24,000. Seealso figure 41, site 15.

105

During the past 50 yr or so, an extensiveliterature has developed on the fauna. Earlyfaunal lists based on the University of Californiacollections appeared in papers by Matthew andStirton (1930a, p. 367), Reed and Longnecker(1932, p. 66), and Plummer (1932, p. 775). Var-ious papers have dealt with certain taxa in thefauna. Matthew and Stirton (1930b) describeda bone-eating dog, Borophagus cyonoides,later referred to Osteoborus by Stirton andVanderHoof (1933). This was followed by a study(Matthewand Stirton, 1930a) of thefossil horsesthat includes a description of the type of Astro-hippus ansae and the referral of three otherhorse taxato species described by Cope (1893)from Mulberry Canyon south of Goodnight,Texas. Burt (1931) described the saber-toothedcat now identified as Machairodus cf. M. colorad-ensis (the type ofM. catocopis is properly referredto Nimravides, according toMartin and Schultz,1975). After Matthew's death, Stirton completedan account of the rhinoceroses (Matthew, 1932).Stirton described the type lower jaw of aruminant, Pediomeryx hemphillensis (Stirton,1936b; Webb, 1983b), gave measurements of ajaw of the antilocaprid Capromeryx altidens(Stirton, 1938) and mentioned the rarercarnivores in an abstract (Stirton, 1939). Othercontributions include the descriptions of somefragmentarygomphothere material (Frick, 1933,p. 606), duck (Compton, 1934; Brodkorb, 1964,p. 225), bird, and carnivore tracks from the vol-canic ash overlying the quarry beds (Johnston,1937e), the horse Dinohippus (Quinn, 1955,p. 43), the camel Megatylopus matthewi (Webb,1965; Harrison, 1985), and the carnivores(Dalquest, 1969b, 1986; Webb, 1969b; Wagner,1976; Richey, 1979; Harrison, 1981, 1983). Thesmall camels, first mentioned by Gregory (1942),were described by Harrison (1979), Dalquest(1980), and Breyer (1983). The horses weredescribed or reviewed by Dalquest and Donovan(1973), Dalquest (1978, 1981), MacFadden andWaldrop (1980), MacFadden (1984a), andHulbert (1987). Schultz (1977a) presented a listof the mammals along with a description of thesite and comparisons of the fauna with otherHemphillian faunas from Texas and Oklahoma.A recent summary of the fauna including adescription of the micromammals was given byDalquest (1983). Additional micromammals weredescribed by Dalquest and Patrick (1989). Thesloth Thinobadistes was identified by Webb(1989). The herpetofauna was described byParmley (1984, 1987). The fauna as currentlyrecognized is listed in table 9.

An important paleoecological analysis of thefauna was done by Shotwell (1955, 1958) usingspecimens in the University of California col-lection. From data on abundance of species,minimumnumber of individuals,and complete-ness of skeletal representation, he constructeda faunal analysis model by which he assignedtaxa to proximal, intermediate, and distal com-munities. He concluded that the proximalcommunity at the Hemphill site lived in agrassland habitat and was dominated by largegrazing herbivores such as horses, camels,rhinoceroses, and deer and by large predatorssuch as the saber-toothed cat and the bone-eating dog. He believed that a more distal com-munity at the site was one of less abundantmammals such as peccary, mastodon, and wol-verine inhabiting brush or open woodland.

The climate during the late Hemphillianapparently was somewhat drier than during theClarendonian or early Hemphillian. The absenceofbrowsers and the reduced diversity of grazersreflect the progressive trend from woodlandsavanna to steppe that had culminated by theend of Hemphillian time (Webb, 1977, 1983a).

Geology

According to Dalquest (1969b, p. 2), the fossilsat Coffee Ranch accumulated in a lake or bogof moderate but unknown area. The lacustrinesediments were then buried under about 9 m(30 ft) of eolian material and are now exposedfor about 90 m (300 ft) along the east face of asteep hillside at the head of a northward-draining valley that runs into Red Deer Creek(figs. 52 and 53). The original areal extent ofthe fossil-bearing strata is uncertain becausethe east portion has beeneroded away, whereasthe west margin lies buried in the hillside. Fossilquarrying over the years has undercut theoverlying strata, causing large blocks to collapseand obscure much of the outcrop.

The present exposure is lenticular in profile.The following section near the center of thedeposit was measured by Dalquest (1969b, p. 2).

ThicknessBed Description in feet8. Overburden of buffy, sandy

clay and soil 25.07. Volcanic ash 9.06. Compact bentonitic clay 2.0

106

Figure 53. Coffee Ranch Quarry, Hemphill County, Texas, in 1936.(Type localityfor HemphillianLand MammalAge.) Fossils are presentin lowerpart of section belowoverhangingledgeof volcanic ash. Photocourtesy of Panhandle-PlainsHistorical Museum, Canyon, Texas.

ThicknessBed Description in feet5. Greenish gray sand with

some clay 2.04. Reddish brown, sandy clay,

variable in thickness in thedeposit and with sharp butcontorted contact with bedsabove and beneath 1.0

3. Greenish sand and sandy claywith some pebble bands andthin calcareous sandstonelayers 5.5

2. Slick, hard reddish brown claywith calcareous crusts andnodules 0.2

1. Buff-colored aeolian sandysediments of the OgallalaFormations; bottom notexposed in the area

Although vertebrate fossils appear in all bedsof the lake deposit (Beds 2 through 7), the bulkof the fossils and most of the complete boneshave been found in the semiconsolidated green-ish sand of Bed 3. Most early collecting seemsto havebeen concentrated in this bed. Thebonesare white to cream colored, chalky, light andporous but generally well preserved. The densegreenish bentonitic clay (Bed 6) also containsabundantbones, but many are broken. Dalquest

(1983) recovered a small but important micro-vertebrate fauna by screenwashing the clay.

Some concentrations of bone were found inthe volcanic ash, but for the most part bonesare few and scattered. The ash is thinly bedded,and many of the bedding planes show distinctripple marks; several contain abundant birdand mammal tracks. Most of the excellent ani-mal tracks described by Johnston (1937e) arefound on a single bedding plane that lies approx-imately 20 cm (8 in) above the base of the vol-canic ash and approximately 2.4 m (8 ft) abovethe main fossil-bearing horizon, which is nearthe base of the greenish sand of Bed 3. A fewtracks have been found above this level. Theyare unusually clear and well preserved and thuscan be easily and accurately measured. Thevolcanic ash apparently was deposited in shallowwater and was in a damp, slightly plastic con-dition when the tracks weremade. Because thereis no evidence of erosion or desiccation on thissurface, it appears that the tracks were coveredby a protecting layer of water-laid ash shortlyafter they were made. Samples of the ash takenfrom the base ofthe deposit were radiometricallydated by Izett (1975, p. 202) using the fission-track method on zircon and hydrated glassshards. Glass-mantled zirconmicrophenocrystsyielded an age of 6.6±0.8 Ma, and glass shardsgave an age of 4.7±0.8 Ma. Boellstorff (1976,p. 65) obtained a glass fission-track date of5.3±0.4 Ma on glass from this ash.

107

Table 9. Fauna! lists of late Hemphillian local faunas of theTexas and Oklahoma Panhandles

ABCClass Osteichthyes

Order SemionotiformesFamily Lepisosteidae

Lepisosteus sp. - gar XClass Amphibia

OrderUrodela (=Caudata) - salamandersFamily Ambystomatidae

Ambystoma cf. A. minshalliTihen and Chantell XClass Reptilia

Order CheloniaFamily Testudinidae

Geochelone sp. - large tortoise XXXSmall pond turtle X

Order SquamataFamily Boidae

Erycinae genus et sp. indet. XOgmophis pliocompactus Holman X

Family ColubridaeElaphenebraskensis Holman - rat or black snake XLampropeltis similisHolman - king snake XPaleoheterodon tiheni Holman - hog-nosed snake XParacoluber storeri Holman - racer XSalvadorapaleolineata.Holman - patch-nosed snake X

Order CrocodiliaFamily Crocodilidae

Crocodilid sp. - crocodile XClass Ayes

Order FalconiformesFamily Accipitridae

Accipitrid sp. - hawk XOrder Anseriformes

Family AnatidaeNettion bunkeri Wetmore - pond duck X

Class MammaliaOrder Insectivora

Family SoricidaeSoricid sp. - shrew X

Family TalpidaeScalopus {Hesperoscalops)ruficervus Dalquest - mole *

Order ChiropteraFamily Vespertilionidae

Eptesicus hemphillensisDalquest - brown bat *

* * Holotype ofgenus* Holotypeof speciesX Occurrence in fauna? Possible occurrence in faunaA Optima (=Guymon), Texas County, OklahomaB Coffee Ranch (=Miami), Hemphill County, TexasC Goodnight, Armstrong County, Texas

A B cClass Osteichthyes

Order SemionotiformesFamily Lepisosteidae

Lepisosteus sp. - gar XClass Amphibia

Order Urodela (=Caudata) - salamandersFamily Ambystomatidae

Ambystoma cf. A. minshalliTihen and Chantell XClass Reptilia

Order CheloniaFamily Testudinidae

Geochelone sp. - large tortoise X X XSmall pond turtle X

Order SquamataFamily Boidae

Erycinae genus et sp. indet. XOgmophis pliocompactus Holman

Family ColubridaeX

Elaphenebraskensis Holman - rat or black snake XLampropeltis similis Holman - king snake XPaleoheterodon tiheniHolman - hog-nosed snake XParacoluber storeri Holman - racer XSalvadorapaleolineata.Holman - patch-nosed snake X

Order CrocodiliaFamily Crocodilidae

Crocodilidsp. - crocodile XClass Aves

Order FalconiformesFamily Accipitridae

Accipitrid sp. - hawk XOrder Anseriformes

FamilyAnatidaeNettionbunkeri Wetmore - pond duck X

Class MammaliaOrder Insectivora

Family SoricidaeSoricid sp. - shrew X

Family TalpidaeScalopus {Hesperoscalops)ruficervus Dalquest - mole *

Order ChiropteraFamily Vespertilionidae

Eptesicus hemphiLlensis Dalquest - brown bat *

108

Table 9. (cont.)

ABCOrderEdentata

Family MegalonychidaeMegalonyxsp. - ground sloth X

Family MylodontidaeThinobadistes sp. - ground sloth X

Order RodentiaFamily Mylagaulidae

Mylagavluscf. M. monodon (Cope) - burrowing rodent XMylagaulussp. X

Family CastoridaeDipoides sp. - beaver X

Family EomyidaeComancheomys rogersi Dalquest **

Family SciuridaeSpermophilussp. - ground squirrel X

Family GeomyidaeProgeomys sulcatus Dalquest - pocket gopher

Family HeteromyidaeCupidinimus sp. XPerognathus sp. - pocket mouse XProdipodomys(?) sp. - kangaroo rat X

Family CricetidaeParonychomys(?) sp. - grasshopper mouse XCalomys {Bensonomys) cojfeyi Dalquest - neotropicalmousePeromyscus sp. - deer mouse XProsigmodon sp. - cottonrat XNeotoma(Paraneotoma) minutusDalquest - wood rat

Order LagomorphaFamily Leporidae

Hypolaguscf. H. vetus (Kellogg) - rabbit X XOrder Carnivora

Family FelidaeMachairodus cf. M. coloradensisCook - saber-toothed cat X XFelis proterolyncis Savage - lynx * XPseudaelurus hibbardiDalquest - cat *AdelphaiLurussp. - cat X

Family CanidaeOsteoborus cyonoides(Martin) - bone-eating dog XXXCanis dauisi Merriam - coyote X XVulpes stenognathus Savage - slender-jawed fox * X

Family MustelidaePlesiogulomarshalli(Martin) - wolverine X XPliotaxideacf. P. nevadensis(Butterworth) - smallbadger X X

Family ProcyonidaeArctonasua JrickiBaskin - coati "Family UrsidaeAgriotheriwn cojfeyorum Dalquest - large bear X *

Order ProboscideaFamily Gomphotheriidae

Rhynchotherium (?) sp. - gomphothere XFamily Mammutidae

Pliomastodon sp. - mastodon X

A B cOrderEdentata

Family MegalonychidaeMegalonyxsp. - ground sloth

Family MylodontidaeThinobadistes sp. - ground sloth

X

XOrder Rodentia

Family MylagaulidaeMylagavluscf. M. monodon (Cope) - burrowing rodentMylagaulussp. X

X

Family CastoridaeDipoides sp. - beaver

Family EomyidaeComancheomys rogersi Dalquest

X

**Family Sciuridae

Spermophilussp. - ground squirrel XFamily Geomyidae

Progeomyssulcatus Dalquest - pocket gopherFamily Heteromyidae

Cupidinimus sp.

**X

Perognathus sp. - pocket mouseProdipodomys(?) sp. - kangaroo rat

Family CricetidaeParonychomys(?) sp. - grasshopper mouseCalomys {Bensonomys) cojfeyi Dalquest - neotropicalmouse

XX

X*

Peromyscus sp. - deer mouse XProsigmodon sp. - cotton rat XNeotoma {Paraneotomd) minutusDalquest - wood rat *

Order LagomorphaFamily Leporidae

Hypolagus cf. H. vetus (Kellogg) - rabbitOrder Carnivora

X X

Family FelidaeMachairodus cf. M. coloradensisCook - saber-toothed cat X XFelis proterolyncis Savage - lynxPseudaelurus hibbardiDalquest - cat

* X

AdelphaHurus sp. - cat XFamily Canidae

Osteoborus cyonoides(Martin) - bone-eating dogCanis dauisi Merriam - coyote

XX

XX

X

Vulpes stenognathus Savage - slender-jawed foxFamily Mustelidae

Plesiogulomarshalli(Martin) - wolverine X

X

XPliotaxideacf. P. nevadensis(Butterworth) - smallbadger X X

Family ProcyonidaeArctonasuafricki Baskin - coati *

Family UrsidaeAgriotheriwncojfeyorum Dalquest - large bear

Order ProboscideaX *

Family GomphotheriidaeRhynchotherium (?) sp. - gomphothere

Family MammutidaePliomastodon sp. - mastodon X

X

109

Table 9. (cont.)

ABCOrder Artiodactyla

Family TayassuldaeProsthennopscf. P. grqffhami Schultz and Martin - peccary XProsthennops sp. - peccary X

Family CamelidaeMegatylopusmatthewiWebb - large camel X *Alforjas taylori Harrison - medium-sized camel X XHemiauchenia vera (Matthew) - Uamalike camel X X

Family DromomerycidaePediomeryx{Pediomeryx) hemphillensisStirton -

giraffelikeruminant X **Family Antilocapridae

Texoceros cf. T. altidens(Matthew) - pronghorn X XAntilocaprid sp. - pronghorn X

Order PerissodactylaFamily Equidae

Dinohippus interpolatus (Cope) - large 1-toed horse X X *Astrohippus ansae(Matthew and Stirton) - 1-toed horse X XNeohipparioneurystyle (Cope) - 3-toed horse X XNeohipparion leptodeMerriam - 3-toed horse XNeohippariongidleyiMerriam - 3-toed horse XNannippus lenticularis (Cope) - small 3-toed horse

or Nannippus ingenuus (Leidy) X X *Nannippus minor (Sellards) - small 3-toed horse X

Family RhinocerotidaeAphelops cf. A. kimballensis Tanner (or A. mutilus

Matthew) - rhinoceros XAphelops sp. - rhinoceros XTeleoceras sp. - short-legged hippolikerhinoceros X X

The geologic history of the lake deposits asinterpreted by Dalquest (1969b, p. 3) is brieflysummarized as follows:

(1) Deposition of sand and dust in the basinof a shallow seasonal lake, forming asandy mud (Bed 3). Bones of animals thatdied in or near the lake settled throughthe mud to rest near the bottom. Whenthe lake was dry, heavy rains washedcoarse-grained debris from the nearbycaprock hills and cliffs out onto a firmsandy flat, forming layers of pebbles andgravel. These later served as traps thatcaught bones sinking down through thesoft sediments above them.

(2) Deposition of thereddish-brown sandy clay(Bed 4) under somewhat different climatic

conditions, when moresubaerial exposureof the sediments was occurring.

(3) A brief return to conditions prevalent dur-ing Bed 3 timewith the deposition ofaddi-tional greenish sand (Bed 5).

(4) Development of a meadow or bog wheresmall rodents, shrews, and rabbits livedand whose remains became preserved inthebentonitic clay (Bed 6).

(5) Volcanic activity somewhere to the west,which produced a fallout ofvolcanic dustthat settled on slopes and hills about thelake basin. Heavy rains washed the ashinto the shallow lake, where it settled toform mud. When the lake periodicallybecame dry, the mud retained ripplemarks and footprints of wading animals.

A B cOrder Artiodactyla

Family TayassuldaeProsthennops cf. P. grqffhamiSchultz and Martin - peccary XProsthennops sp. - peccary X

Family CamelidaeMegatylopus matthewi Webb - large camelAlforjas taylori Harrison - medium-sized camelHemiauchenia vera (Matthew) - Uamalike camel

XXX

XX

Family DromomerycidaePediomeryx{Pediomeryx) hemphillensisStirton -

giraffelikeruminantFamily Antilocapridae

Texoceros cf. T. altidens(Matthew) - pronghorn

X

X

**X

Antilocaprid sp. - pronghornOrder Perissodactyla

X

Family EquidaeDinohippus interpolatus (Cope) - large 1-toedhorseAstrohippus ansae(Matthew and Stirton) - 1-toed horse

XX

X"

*X

Neohipparioneurystyle (Cope) - 3-toed horseNeohipparion leptodeMerriam - 3-toed horseNeohippariongidleyiMerriam - 3-toed horseNannippus lenticularis (Cope) - small 3-toed horse

or Nannippus ingenuus (Leidy)Nannippus minor (Sellards) - small 3-toed horse

Family RhinocerotidaeAphelopscf. A. kimballensisTanner (or A. mutilus

Matthew) - rhinoceros

X

X

XX

XX

X

X

Aphelops sp. - rhinocerosTeleocerassp. - short-legged hippolikerhinoceros X X

X

110

More ash fell and washed into the basin,refilling the lake and covering the hard-ened layers of ash with new layers ofmud,thus preserving bones and footprints.Additional ash and dust washed into thelake until 2.7 m (9 ft) had accumulatedand the basin was filled. The fossiliferousdeposits were thus sealed beneath theash.

(6) Deposition of eolian silts and clays anddevelopment of soils that overlie the vol-canic ash.

Age and CorrelationAccording to Dalquest (1983), the Coffee

Ranch Local Fauna is a unit fauna and repre-sents animals that lived at the site during arelatively brief interval, perhaps a few centuries,during which a closed depression formed andthen filled with sediment. The zircon fission-track date of 6.6±0.8 Mafor the ash immediatelyoverlying the fossil-bearing unit may representa more reliable age for the fauna than do theglass fission-track dates of 5.3±0.4 Ma(Boellstorff, 1976, p. 65) and 4.7±0.8 Ma (Izett,1975, p. 202), which may be too low because ofannealing of the tracks (Izett, personal com-munication, 1976). Lindsay and others (1975,p. 114; 1984, p. 460) determined that the fossil-bearing sands and the overlying ash are in athick, normally magnetized polarity zone. Theythought the zone represented the lower part ofmagnetic chron 5 (approximately 5.9 Ma ago)because the ash date indicates that it is olderthan the Gauss chron (3.3 to 2.4 Ma ago).

Some of the principal late Hemphillian cor-relative faunas (table 1) include the Optima(=Guymon) Local Fauna of Oklahoma (Hesse,1936b;Savage, 1941), the Rhino Hill and EdsonLocal Faunas of Kansas (Harrison, 1983), theZX Bar Local Fauna in the Upper Snake Creekfaunal sequence of northwest Nebraska (Skinnerand others, 1977), the Camel Canyon,Redington, Wikieup, and White Cone LocalFaunas ofArizona, and the Chamita Local FaunaofNew Mexico (Lindsayand others, 1984).

Goodnight FaunaThe term Goodnight Fauna has been used to

refer to a small assemblage of fossil mammalsof late Hemphillian age discovered by Cummins

(1893) and described by Cope (1893) from theupper part of Mulberry Canyon on the CharlesGoodnight Ranch in Armstrong County, Texas(fig. 41, site 16). Mulberry Creek is a tributaryof the Prairie Dog Town Fork of the Red River.The exact locality from which the fauna wascollected has never been recorded and cannotbe determined satisfactorily from availableaccounts of early expeditions in the area.Thereis some indication that the locality may beabout 6.4 or 8.0 km (4 or 5 mi) south or south-west of the town of Goodnight on the north sideof Mulberry Canyon. Cummins (1893, p. 201)designated the fossil-bearing strata the"Goodnight beds" and attempted to show strat-igraphically that they overlay the "Clarendonbeds" farther east. He had distinctly differentgeologic sections for the north and south sidesof the canyon. Gidley (1903a, p. 628) showedthat Cummins had misidentified or misinter-preted certain gravel beds in the Clarendon andMulberry areas and that the strata were essen-tially the same on both sides of MulberryCanyon. He then equated the Goodnight andClarendon beds both faunally and stratigraph-ically. Later work has shown, however, that theGoodnight Fauna is definitelyyounger than theClarendon Fauna, although the Goodnight bedsdo not represent a distinct lithologic unit in theOgallala.

The fauna described by Cope (1893) includesisolated horse teeth that are the type specimensof Dinohippus interpolatus and Nannippus lentic-ularis as well as specimens referred to Neohip-parion eurystyle. The lectotype specimen of thelatter is actually from the "Falls of the PaloDuro south of Amarillo," which is at the lowerend of Lake Tanglewood in Randall County—probably the Currie Ranch Local Fauna site(fig. 41, site 19).A fourth horse in the GoodnightFauna is apparently Astrohippus ansae, de-scribed by Matthew and Stirton (1930a) fromthe Hemphill (=Coffee Ranch) locality. Therhinoceros, Aphelops, was also listed in thefauna by Cope. The Cope specimens are now atthe Texas Memorial Museum at The UniversityofTexas at Austin.

The Goodnight Fauna is late Hemphillian and,although small, is specifically identical to theCoffee Ranch Local Fauna in Hemphill County(table 9). Subsequent collecting by the FrickLaboratory from several quarries on theMcGehee and Hubbard Ranches near Goodnightduring the early 1950's enlarged the fauna, butthefossils obtained have not been published.

111

Optima (=Guymon)Local Fauna

The Optima Local Fauna is a late Hemphillianfauna identified in several localities about 2.4 km(1.5 mi) southwest of Optima, 12 km (7.5 mi)northeast of Guymon, and 90 m (300 ft) northof the Rock Island Railroad right-of-way insees. 6 and 7, T. 3 N, R.16 E, Texas County,Oklahoma (fig. 41, site 14). According to Savage(1941, p. 692), the fossiliferous deposits areexposed in an escarpment eroded by severalsmall intermittent streams draining southwardinto the Beaver River. These escarpments arenot prominent but are steep, talus-coveredslopes and rolling grass-covered hills, probablyresulting from loose cementation in the calichecaprock.

The stratigraphic sequence in the small areaof the University of Oklahoma quarries con-sists, according to Savage (1941, p. 693), of morethan 0.6 m (>2 ft) of brownish-red sand, grit,and gravel overlain by 1.2 to 2 m (4 to 7 ft) ofwhite quartz sand that grades into grits andgravel in places and contains fossil vertebrates.This unit is overlain by 2 or 2.4 m (7 or 8 ft) ofbuff to gray clay and silt that is also fossiliferous,and this is capped by 1 to 2 m (3 to 7 ft) of soiland caliche. The coarser deposits are stream-channel deposits. Most of the fossils have beenfound in small pockets in thewhite sand, which,according to Hesse (1936b, p. 58), is loose andcoarse or cemented into a calcareous grit. Manyof the coarse, gravelly pockets are surroundedby a fine reddish-brown fluvial sand. The fossilsare buff towhite and heavily silicified,but theyshow traces of calcification and are unusuallylight and porous. Although incomplete, thespecimens show no evidence of being heavilywaterworn. Apparently deposition of the fossilswas rapid but with little transportation.

Fossils were discovered by the landowner,James English, and reported to the Universityof California, which collected there in 1929.Additional collections were obtained by the Uni-

versity of Oklahoma and the Frick Laboratoryduring the 19305. The California collection wasdescribed by Hesse (1936b). The Oklahomacollection was studied by Savage (1941), whodescribed the type specimens of a fox, Vulpesstenognathus, and a lynx, Felis proterolyncis. Adromomerycid ruminant, Yumacerasfalkenbachi{=Pediomeryx hemphillensis), and an antilo-caprld, Texocerosguymonensis (=cdtid.ens), werereported by Frick (1937). In addition, variousmembers of the fauna have been mentioned,described, or revised by other workers in papersdevoted to particular taxa such as antilocaprids(Hesse, 1935b; Stirton, 1938), sloths (Hirschfeldand Webb, 1968, p. 245, 286), badgers (Hall,1944, p. 15; Wagner, 1976, p. 110), wolverines(Harrison, 1981),procyonids (Baskin, 1982), cats(Martin and Schultz, 1975; Harrison, 1983,p. 31), camels (Harrison, 1979; Breyer, 1983),dromomerycids (Webb, 1983b), and horses(MacFadden, 1984a).

Grazing mammals dominate the fauna(table 9), horses forming 80 percent of theOklahoma collection. Several hundred isolatedteeth and numerous jaws and other remains ofDinohippus interpolatus and Astrohippus ansaeare included. Second in importance are the arti-odactyls; camels and the antilocaprid, Texocerosaltidens, are the most numerous. Carnivoresare less abundant but varied.

The Optima Local Fauna is similar to thatfrom Coffee Ranch in Hemphill County, Texas.Both are thought tobe late Hemphillian (table 9),and the two faunas share many common taxa.The abundance of grazing ungulates in theOptima Local Fauna, as compared with brows-ing types, indicates that the region was pre-dominantly a broad, open, short-grass country(Savage, 1941, p. 705). The existence of deer,bear, beaver, sloth, fox, and lynx indicates thepresence of forested areas, probably on flood-plains. Alligator remains suggest that the climatewas warmer and more humid than now andthat the streamswere deeper and more sluggishthan present-day streams in the area becausealligators prefer quiet, deep waters.

112

Stop 17: Latest Hemphillian Faunas ofthe Texas PanhandleG. E. Schultz

TheAxtelLocal Fauna ofRandall County, Texas, and the Christian RanchLocal Fauna ofArmstrongCounty, Texas, are dominated by grazing mammals adapted to a semiarid grassland savanna orsteppe.

Axtel Local FaunaThe Axtel Local Fauna is one of the latest

Hemphillian faunas in the Southern High Plains.The site is a quarry located on a promontory ofthe east wall of Woody Draw, a south-drainingtributary of North Cita Canyon about 5.6 km(3.5 mi) south and 19 km (12 mi) east of thetown of Canyon and just outside Palo DuroCanyon State Park, Randall County, Texas, inthe SE corner, SW 1/4, SW 1/4, sec. 165,Blk. 6, I. and G.N. R.R. Co. Survey (fig. 41,site 18).

Fossils were discovered in 1936 by Donald E.Savage near the bottom of a 1.5-m-thick (5-ft)brown fluviatile sand of limited areal extent.The sand bed rests on red shales of the TriassicDockum Group and is overlain in turn by 1.8 m(6 ft) of brown caliche-cemented sandstone, 0.3to 0.6 m (1 to 2 ft) of resinous opal, and a capof nearly 9 m (30 ft) of massive white caliche(Johnston and Savage, 1955, p. 28).

The fauna, collected by WPA crews for thePanhandle-Plains Historical Museum, was firstreported by Johnston (1939b), who describedthe type specimens of Osteoborus hilli, a bone-crushing dog (see also Webb, 1969b; Richey,1979). Most of the fauna is undescribed, al-though Johnston and Savage (1955, p. 28) pub-lished a faunal list (table 10) and a stratigraphicsection of the quarry. Horses are the most abun-dant forms; there are numerous isolated teeth,jaws, and limb bones of Dinohippus cf. D. mexi-canus and Astrohippus cf. A. stockt Mawby(1965, p. 574) described a machairodont andOelrich (1957, p. 236) and AufTenberg (1962a,p. 630) reported a tortoise, Geochelone cf.G. turgida.

The Axtel Local Fauna is latest Hemphillian(table 10) but younger than the Coffee RanchLocal Fauna, as indicated by the moreadvancedhorses, camels, and Osteoborus (Johnston and

Savage, 1955, p. 29) (compare tables 8 and 9).The fauna is equivalent in age to the ChristianRanch Local Fauna (table 10) and several othersmaller ones in the Palo Duro Canyon region(fig. 41). Lindsay and others (1975, p. 117)determined that the fauna lies in a zone ofnormal magnetic polarity, which probablyrepresents chron 5 because of the similarity ofthe fauna to that from Coffee Ranch. The CoffeeRanch Local Fauna is assigned to chron 5 be-cause the fossil-bearing strata exhibit normalmagnetic polarity and because of the radiometricdates obtained on the overlying volcanic ash(Izett, 1975; Boellstorff, 1976).

The climate of theregion by latest Hemphilliantime already was semiarid as evidenced by along history of calcic soil development thatproduced the caliche caprock that underlies theHigh Plains surface. This caliche overlies thefossil bed at the Axtel site, but at a nearbylocality (Currie Ranch, fig. 41, site 19) a smalllate Hemphillian fauna is sandwiched betweentwo massivecaliche beds. Waterworn cobbles ofthe lower caliche are present in the fossil bed,indicating that caliche formation had alreadycommenced by the time these latest Hemphillianfaunas appeared (Johnston and Savage, 1955,p. 33). The absence of rhinoceros from latestHemphillian faunas and the greatly reducednumber of mastodons [Rhynchotherium) alsosuggest a shift toward a drier climate in theregion.

Christian Ranch Local FaunaThis latest Hemphillian faunal site is on the

Terrell Christian Ranch 15 km (9.5 mi) southand 12 km (7.5 mi) west of Claude, ArmstrongCounty, Texas (fig. 41, site 17) in the SE 1/4,NW 1/4, sec. 4, Blk. 1, I. R.R. Co. Survey.Johnston and Savage (1955, p. 30) gave the fol-lowing description of the site and its origin:

113

Fossiliferous exposures lie on a smallerosional remnant hill atop a ridge thatconnects a prominent intracanyon butte,called "Big Mountain" locally, to the eastwall of Horseshoe Canyon. HorseshoeCanyon is a large, deep, amphitheater-like southward-draining tributary and isone of the most spectacular sights inthe Palo Duro system.

The fossiliferous stratum is a 3- to10-foot bed of gray sand overlain by a6-inch to 3-foot bed of gray to whiteresistant sandy limestone. These twobeds constitute a lens 300 feet widewhich grades laterally into brown mud-stones and sands or sandstones.

The supra-Triassic section found atHorseshoe Canyon is the thickest (about260 feet) seen at any fossil site in thePanhandle. The brown-colored beds areinterpreted as river-floodplain or playaaccumulations. Phases of deposition orprecipitation of limey material arerepre-sented by the light-colored laminae inthe lower part of the section and by themassive sandy or silty caliche beds atthe top. The gray fossil-bearing lens isbelieved to have been formed in a springfed pond or bog area where the finerelastics (silts and clays) were flushedaway by some sort of churning action.The gray color was probably developedby the reduction of ferric oxides (thebrown and red coloration in the sur-rounding sediments).This reduction mayhavebeen brought about by the accumu-lation of plants and resultant organicacids in the environs of this more per-manent water supply. And in the latestinterval of existence of this water hole,calcareous matrixwas concentrated and

deposited. The aggregation of bones inthe gray lens also suggests that herewas a spot where animals congregatedto drink and feed.

The supra-Triassic section at the site is about78 m (260 ft) thick. The fossil quarry is abouthalfway up, or 39 m (130 ft) below the surfaceof the surrounding plains. Fossils were dis-covered here in 1930 by Floyd V. Studer, whocollected and prepared most of the specimensnow in the Panhandle-Plains Historical Mu-seum. The collection, largely undescribed, con-sists mainly of teeth and jaws of Astrohippuscf. A. stocki with a smattering of other horses,camels, antilocaprids, peccaries, and carnivores(table 10). Richey (1979) described a lower jawof Osteoborus. An excellent lower jawof a gom-phothere, probably Rhynchotherium, was de-scribed by Savage (1955b). Additional specimenswere obtained by the University of Californiaand the Frick Laboratory in 1953 and by WestTexas State University in more recent years.

No paleomagnetic data exist for this site. Thefauna, which is latest Hemphillian, resemblesthat from theAxtel site and other small sites inthe Palo Duro area and is more advanced thanthe one from Coffee Ranch (table 9). The horsessuggest a correlation with the late HemphillianYepomerafauna of Mexico (MacFadden, 1984b).

Latest Hemphillian Gravel PitsSeveral gravel pits in Ellis County, Oklahoma

(Miller, Nations, Campbell, and Virgil Clark),occupy deep channels cut into the top of theOgallala. These have yielded horse teeth {Astro-hippus stocki and Neohipparion cf. N. eurystyle)of latest Hemphillian age (Tedford and others,1987).

114

Table 10. Faunal lists of latest Hemphillian local faunas of the Texas Panhandle.Modified after Johnston and Savage (1955).

ABCClass Reptilia

Order CheloniaFamilyTestudinidae

Geochelone turgida (Cope) - tortoise XGeochelonesp. - large tortoise X XTestudinid sp. - small tortoise X

Class MammaliaOrderEdentata

Family MegalonychidaeMegalonyxsp. - ground sloth X

Order RodentiaFamily Mylagaulidae

Mylagaulussp. - burrowing rodent XFamily Geomyidae

Geomys sp. - pocket gopher XOrder Carnivora

Family FelidaeMachairodus {Heterofelis) sp. - saber-toothedcat XMachairodont? - saber-toothed cat X

Family CanidaeOsteoborus hilli Johnston - bone-eating dog *Osteoborus sp. - bone-eating dog X XCanis sp. - coyote-sized form XCanid sp. - small form X

Family MustelidaePliotaxideasp. - badger XMephitinesp. - skunk X

Family UrsidaeAgriotheriumsp. - bear X

Order ProboscideaFamily Gomphotheriidae

Rhynchotherium? sp. - gomphothere X XOrderArtiodactyla

FamilyTayassuidaeProsthennops sp. - peccary X X

Family CamelidaeMegatylopus? - large camel XXXHemiauchenia sp. - llamalike camel X X

Family AntilocapridaeHexobelomeryx? sp. - medium-to-large pronghorn X X

Order PerissodactylaFamilyEquidae

Dinohippuscf. D. mexicanus(Lance) - 1-toedhorse XXXAstrohippus cf. A. stocki (Lance) - 1-toed horse XXXNeohipparion cf. N. ewystyle (Cope) - 3-toed horse XXXNannippuscf. N. lenticularis (Cope) = Nannipus ingenuus (Leidy) X

- 3-toed horse

* Holotypeof speciesX Occurrence in faunaA Axtel, Randall County, TexasB Christian Ranch, Armstrong County, TexasC Currie Ranch, Randall County, Texas

A B cClass Reptilia

Order CheloniaFamilyTestudinidae

Geochelone turgida (Cope) - tortoiseGeochelonesp. - large tortoiseTestudinid sp. - small tortoise

XXX

X

Class MammaliaOrderEdentata

Family MegalonychidaeMegalonyxsp. - ground sloth

Order RodentiaX

Family MylagaulidaeMylagaulussp. - burrowing rodent

Family GeomyidaeX

Geomys sp. - pocket gopher XOrder Carnivora

Family FelidaeMachairodus [Heterqfelis) sp. - saber-toothedcatMachairodont? - saber-toothed cat

XX

Family CanidaeOsteoborus hilli Johnston - bone-eating dog *Osteoborus sp. - bone-eating dog X XCanis sp. - coyote-sized form XCanid sp. - small form

Family MustelidaePliotaxideasp. - badgerMephitinesp. - skunk

Family Ursidae

X

X

X

Agriotheriumsp. - bear XOrder Proboscidea

Family GomphotheriidaeRhynchotherium? sp. - gomphothere X X

OrderArtiodactylaFamily Tayassuidae

Prosthennops sp. - peccary X XFamily Camelidae

Megatylopus!? - large camelHemiauchenia sp. - llamalike camel

XX

XX

X

Family AntilocapridaeHexobelomeryx? sp. - medium-to-large pronghorn X X

Order PerissodactylaFamily Equidae

Dinohippuscf. D. mexicanus (Lance) - 1-toedhorseAstrohippus cf. A. stocki (Lance) - 1-toed horse

XX

XX

XX

Neohipparion cf. N. ewystyle (Cope) - 3-toed horseNannippuscf. N. lenttcularis (Cope) = Nannipus ingenuus (Leidy)

- 3-toed horse

XX

X X

115

AcknowledgmentsFunding for research conducted by T. C.

Gustavson and V. T. Holliday was provided bythe Department of Energy, Salt RepositoryProject Office, under contract number DE-AC97--83WM46651. D. A. Winkler's workwas supportedby Sigma Xi, American Association of PetroleumGeologists, and the Geology Foundation, TheUniversity of Texas at Austin.

Figures for this guidebook were prepared byJamie H. Coggin, Wade Kolb, Richard Platt,

Donald Thompson, and Tari Weaver, underthe supervision of Richard L. Dillon. Wordprocessing was by Melissa Snell, and typesettingwas by Susan Lloyd, both under the super-vision of Susann Doenges. T. C. Gustavson,R. W. Baumgardner, Jr., J. A. Raney, M. R.Voorhies, and K. T. Barrow reviewed the guide-book, which was edited by Lana Dieterich anddesigned by Jamie H. Coggin. T. F. Hentz wasthe technical editor.

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