VXE-6 and the ITT/Antarctic Services, Inc., personnel at theBeardmore Camp. We would also like to thank Richard Arculusfor his assistance with the X-ray fluorescence analyses whichwere performed at the University of Michigan. Support for thisproject was provided by National Science Foundation grantDPP 84-19529.

References

Barret, P.J., D.H. Elliot, and J.F. Lindsay. 1986. The Beacon Super-group (Devonian-Triassic) and the Ferrar Group (Jurassic) in theBeardmore Glacier area, Antarctica. In M.D. Turner and J.F. Splett-stoesser (Eds.), Geology of the central Transantarctic Mountains. (Ant-arctic Research Series, Vol. 36.) Washington, D.C.: American Geo-physical Union.

Elliot, D.H. 1971. Manor oxide chemistry of the Kirkpatrick Basalt. InR.J. Adie (Ed.), Antarctic geology and geophysics. Oslo: Universitets-forlaget.

Elliot, D.H., L.M. Jones, M.A. Haban, and M.A. Siders. 1984. Iron-rich tholeiitic lavas, Mesa Range, Northern Victoria Land, Antarc-tica. Los, 65, 1154.

Elliot, D.H., and K.A. Foland. 1986. K-Ar age determinations of theKirkpatrick Basalt, Mesa Range. In E. Stump (Ed.), Geological inves-tigations in northern Victoria Land. (Antarctic Research Series, Vol.46.) Washington, D.C.: American Geophysical Union.

Fleming, T.H. 1986. The role of fractional crystallization in the pet rogenesisof the Kirkpatrick Basalt, northern Victoria Land, Antarctica based on major

element, trace element and mineral chemistry. (Unpublished master ofscience thesis, Ohio State University, Columbus, Ohio.)

Faure, G., J.R. Bowman, D.H. Elliot, and L.M. Jones. 1974. Strontiumisotope composition and petrogenesis of the Kirkpatrick Basalt, QueenAlexandra Range, Antarctica. Contributions to Mineralogy and Petrol-ogy, 48, 153-169.

Faure, G., K.K. Pace, and D.H. Elliot. 1982. Systematic variations of87Sr/86Sr and major element concentrations in the Kirkpatrick Basaltof Mount Falla, Queen Alexandra Range, Transantarctic Mountains.In C. Craddock (Ed.), Antarctic geoscience. Madison, Wisconsin: Uni-versity of Wisconsin Press.

Haban, M . A. 1984. The mineral chemistry and petrogenesis of the FerrarSupergroup north Victoria Land, Antarctica. (Unpublished master ofscience thesis, Ohio State University, Columbus, Ohio.)

Kyle, P.R. 1980. Development of heterogeneities in the subcontinentalmantle: Evidence from the Ferrar Group, Antarctica. Contributionsto Mineralogy and Petrology, 73, 89-104.

Mensing, TM., G. Faure, L.M. Jones, J.R. Bowman, and J . Hoefs.1984. Petrogenesis of the Kirkpatrick Basalt, Solo Nunatak, NorthernVictoria Land, Antarctica, based on isotopic compositions of stron-tium, oxygen and sulfur. Contributions to Mineralogy and Petrology,87, 101-108.

Siders, M.A. 1983. Intraflow variability, chemical stratigraphy andpetrogenesis of the Kirkpatrick Basalt from the Mesa Range Area,north Victoria Land, East Antarctica. (Unpublished master of sciencethesis, Ohio State University, Columbus, Ohio.)

Siders, MA., and D.H. Elliot. 1985. Major and trace element geo-chemistry of the Kirkpatrick Basalt, Mesa Range, Antarctica. Earthand Planetary Science Letters, 72, 54-64.

Weathering profilesin the Jurassic basalt sequence,

Beardmore Glacier region

D. H. ELLIOT

Byrd Polar Research Centerand

Department of Geology and MineralogyOhio State University

Columbus, Ohio 43210

J. BIGHAM and F.S. JONES

Department of AgronomyOhio State UniversityColumbus, Ohio 43210

Basaltic lavas of Jurassic age are exposed in two separateareas in the Beardmore Glacier region (figure 1). The lava se-quences have a maximum thickness of a little over 500 meters.A small number of widespread thick flows, generally fewerthan 10, are accompanied by a variable number of thin flowsof limited extent. The lavas are typical flood basalts with in-dividual distinctive flows being identifiable over distances of30 kilometers. A general description of the lavas is given inBarrett, Elliot, and Lindsay (1986).

Most flows have a thin lower contact zone with amygdales(zeolite tilled vesicles), a massive but irregularly jointed inte-rior, and an amygdaloidal upper contact zone of variable thick-ness. The uppermost parts of some of the upper contact zonesare intensely altered and are overlain by up to 1.5 meters offine-grained structureless rock (figure 2) which is interpretedto be the result of weathering processes and, in a few cases,soil formation. These units of structureless rock carry dispersedangular to rounded clasts of amygdaloidal basalt similar to theunderlying altered lava. The clasts are randomly distributed,show an overall decrease in size upwards, and occur to withina few centimeters of the upper surface. The margins of theclasts range between sharp and diffuse. The upper surface isgenerally planar and horizontal, although disturbance by theoverlying flow is seen at some localities. The contact with theunderlying amygdaloidal basalt varies between sharp and hor-izontal, diffuse and horizontal, and highly irregular. In thelatter case, the structureless rock fills crevices and hollows inthe amygdaloidal upper contact zone of the underlying lava.The crevices are wedge shaped and as much as 1 meter deep,and the upper surface of the flow may have a rounded orbulbous form. The upper surfaces of some of these zones ofstructureless rock carry woody-plant impressions. A few of theunits exhibit networks of tube-like bodies that branch down-wards. These networks span a depth of 25 centimeters andstart 20-30 centimeters below the upper surface.

Microscopically, the structureless rock units consist of scat-tered angular quartz and less common sodic plagioclase ingrains up to 0.1 millimeters across, set in a micro- to crypto-crystalline siliceous matrix in which phyllosilicate shreds are

1988 REVIEW 17

widely, but sparsely, distributed. Only quartz has been iden-tified by X-ray diffractometry. A few of the units contain abun-dant hematite and are brick red. Small irregular areas of acoarse-grained zeolite (clinoptilolite) occur in a few samples.A few of these units contain tricuspate (bubble wall) shards inthe upper 60 centimeters and many contain straight to slightlycurved rods of similar appearance throughout most of theirthickness. The rods are probably fragments of larger shards.The shards are replaced by zeolite or cryptocrystalline material.The branching tube-like structures in one instance consist ofan unoriented orange-brown vermiculite. Other irregular torounded bodies of vermiculite and zeolite may represent crosssections of the tubes.

The branching networks of tube-like bodies are similar toroot structures and suggest that soil-forming processes haveaffected these rocks (Retallack 1988). Orientation of phyllos-ilicates around the tubes (or roots) has not been detected mi-croscopically; however, a weak blocky texture in one thin sectionsuggests the possibility of ped structure. In general, the fea-tures to be expected in paleosols (Retallack 1988; Fastovskyand McSweeney 1987) have not been observed. Titanium andzirconium abundances in the one section analyzed so far donot show the distribution commonly found in soils. Never-theless, the plant remains on the upper surface, the branchingroot-like structures, and the randomly distributed amygdaloi-dal clasts are not inconsistent with these rock units being pa-leosols. Those which lack the root-like structures are describedas weathering profiles even though they were probably af-fected by soil-forming processes.

The delicate tricuspate shards are associated with scatteredquartz, uncommon plagioclase, and very sparse hornblendeand point to contemporaneous silicic volcanism. This com-ponent of silicic ash occurs with amygdaloidal basalt clasts upto tens of centimeters across in these unbedded rock units,which might suggest deposition of the ash on a weatheredlava rubble and redeposition by mass-flow processes. The pres-ervation of delicate shards and the wide area over which atleast one of these rock units is preserved would argue againstthat mechanism. Rather, a process of vertical mixing of silicicash that was deposited on an already weathered basalt wouldseem a more likely process. Such vertical mixing is character-istic of vertisols in which surface material is washed down atthe beginning of the rainy season into the vertical cracks formedin soils during the dry season.

Other processes must have affected the rocks, because thematrix to the shards, mineral fragments, and basaltic clasts ishighly siliceous. Even those basalt clasts which are clearlybreaking down are not being replaced, as would be expected,by clays and hydrated iron oxides but rather are apparentlyreplaced by siliceous material. A secondary silicification hasprobably affected these rocks and replaced most of the normalproducts of weathering.

Figure 1. Locality and geologic sketch map for the Beardmore Gla-cier region.

Figure 2. A 1.5-meter-thick unit of structureless rock overlying highlyweathered amygdaloidal basalt at Mount Block. The structurelessrock, interpreted as a weathering profile, has a sharp and nearhorizontal contact with the underlying flow (white arrow) and car-ries amygdaloidal basalt clasts (indicated by black arrows) up to30 centimeters across. Silicic shards are observed microscopicallythroughout much of the thickness of the profile.

18 ANTARCTIC JOURNAL

The wood impressions, the occurrence of fossilized logs upto 40 centimeters in diameter, and the presence of tree stumpscaught up in the flows (Barrett, Elliot, and Lindsay 1986), allpoint to a climate suitable for the growth of vegetation. Theapparent growth rings in the wood have not been confirmedmicroscopically (E.L. Taylor personal communication) and noinferences can be drawn about the paleoclimate. On the otherhand, if the paleosols are in fact vertisols, then a stronglyseasonal climate with alternating wet and dry seasons is im-plied.

The weathering profiles and paleosols are associated withlacustrine interbeds and tuffs (Elliot, Bigham, and Jones inpress). They mark the longer intervals of time between lavaeruptions during which new drainage was established, shal-low lakes formed in depressions on the lava plain, and weath-ering proceeded to soil formation. The silicic ash shows thatthe bimodal volcanism which is represented in the underlyingPrebble Formation (Larsen 1988) continued into KirkpatrickBasalt time. The bimodal volcanism is associated with Gond-wanaland breakup (Elliot in press).

Fieldwork on which this report is based was supported byNational Science Foundation grant DPP 84-19529. Assistancein the field was provided by D. Buchanan, T. Fleming, and D.Larsen.

References

Barrett, P.J., D.H. Elliot, and J.F. Lindsay. 1986. The Beacon Super-group (Devonian-Triassic) and Ferrar Group (Jurassic) in the Beard-more Glacier area, Antarctica. In M.D. Turner and J.F. Splettstoesser(Eds.), Geology of the central Transantarctic Mountains. (Antarctic Re-search Series, Vol. 36.) Washington, D.C.: American GeophysicalUnion.

Elliot, D.H. In press. Triassic to early Cretaceous evolution of Ant-arctica. In M.R.A. Thomson, J. A. Crame, and J. W. Thomson (Eds.),Geological evolution of Antarctica. Cambridge: Cambridge UniversityPress.

Elliot, D.H., J . Bigham, and F.S. Jones. In press. Interbeds and weath-ering profiles in the Jurassic basalt sequence, Beardmore Glacierregion, Antarctica. Proceedings of the Seventh Gondwana SymposiumSao Paulo, Brazil, August 1988.

Fastovsky, D.E., and D. McSweeney. 1987. Paleosols spanning theCretaceous-Paleogene transition, eastern Montana and western NorthDakota. Geological Society of America Bulletin, 99, 66-77.

Larsen, D. 1988. The petrology and geochemistry of the volcaniclastic upperpart of the Falla Formation and Prebble Formation, Beardmore Glacier area,Antarctica. (Master of science thesis, Ohio State University, Colum-bus, Ohio.)

Retallack, G.J. 1988. Field recognition of paleosols. Geological Society ofAmerica Special Paper, 216,

Taylor, E.L. 1988. Personal communication.

Geochemical record of provenancein fine-grained Permian clastics,central Transantarctic Mountains

L.A. KulssEK and T.C. H0RNER

Byrd Polar Rt'ca rcli Ccii tcrand

Department of Geology and MineralogyOhio State UniversityColumbus, Ohio 43210

During the austral summer of 1985-1986, we collected ap-proximately 310 samples of fine-grained clastics from 24 mea-sured sections in the Permian sequence of the centralTransantarctic Mountains (figure). Our fieldwork and our col-laborative efforts with other sedimentologists from Ohio StateUniversity and Vanderbilt University were summarized byKrissek and Homer (1986). Our ultimate objective is to extractprovenance and paleoclimatic information from these fine-grained sediments, using their mineral and chemical compo-sitions and principles established by other workers (e.g., Grif-fin, Windom, and Goldberg 1968; Keller 1970; Nesbitt andYoung 1982). Because the Permian sequence in the centralTransantarctic Mountains records the transition from a glacialregime (Pagoda Formation), through subaqueous clastic de-posits (Mackellar Formation), to fluvial sequences (FairchildFormation) with coals (Buckley Formation), such an exami-nation promises to provide valuable insight into the timingand nature of this paleoenvironmental change.

Krissek and Homer (1987) described the criteria used to iden-tify samples that have experienced minimal post-depositionalalteration, and presented mineralogic data for 19 samples iden-tified as least-altered." These samples are distributed bothstratigraphically and geographically throughout the study area,and their compositions suggest that:• Pagoda sediments throughout the study area were derived

from physically weathered source rocks;• Mackellar sediments in the northern portion of the study

area were derived from a chemically weathered source, whileMackellar sediments in the southern portion of the studyarea continued to originate from a physically weatheredsource; and

• Buckley sediments throughout the study area were derivedfrom chemically weathered sources.An alternate indicator of weathering effects (the chemical

index of alteration, or CIA) can be calculated from the majorelement geochemistry of fine-grained sediments (Nesbitt andYoung 1982), and our efforts during the past year have con-centrated on using this approach to examine further the prove-nance patterns outlined by the mineralogic data. The CIA isproposed to be unaffected by post-depositional alteration (Nes-bitt and Young 1982), and the lack of covariation betweenvitrinite reflectance and CIA values in samples from the centralTransantarctic Mountains supports that interpretation.

To date, CIA values have been calculated for 27 samples;these data are summarized in the table. A general increase inthe importance of chemically weathered sediments is recordedby the upsection increase in average CIA values, supportingthe interpretation made earlier from mineralogic data. The in-crease in CIA values is especially notable between the Mack-ellar and the Fairchild formations, when sediment inputapparently shifted from a combination of physically and chem-

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