here. The project was supported by National Science Founda-tion grants OPP 89-17348 and OPP 89-15429.

References

Barrett, P.J., D.H. Elliot, and J.F. Lindsay. 1986. The Beacon Super-group (Devonian-Triassic) and Ferrar Group (Jurassic) in theBeardmore Glacier area, Antarctica. In M.D. Turner and J.F.Splettstoesser (Eds.), Geology of the central Transantarctic Moun-tains (Antarctic Research Series, Vol. 36). Washington, D.C.: Ameri-can Geophysical Union.

Collinson, J.W., J.L. Isbell, D.H. Elliot, M.F. Miller, and J.W.G. Miller. Inpress. Permian-Triassic Transantarctic basin. In J.J. Veevers and C.McA. Powell (Eds.), Permian-Triassic Pangaean basins and fold-

belts along the Panthalassan margin of Gondwanaland. Boulder,Colorado: Geological Society of America.

Elliot, D.H. 1992. Jurassic magmatism and tectonism associated withGondwanaland break-up: An antarctic perspective. In B.C.Alabaster and R.J. Pankhurst (Eds.), Magmatism and the causes ofcontinental break-up (Special Publication No. 68). London: Geo-logical Society of London.

Elliot, D.H., and D. Larsen. 1993. Mesozoic volcanism in the centralTransantarctic Mountains, Antarctica: Depositional environmentand tectonic setting. In R.H. Findlay, R. Unrug, M.R. Banks, and J.J.Veevers, (Eds.), Gondwana Eight: Assembly, evolution anddispersal. Rotterdam: Balkema.

Larsen, D. 1988. The petrology and geochemistry of the volcaniclasticupper part of the Falla Formation and Prebble Formation, Beard-more Glacier area, Antarctica. (Unpublished master of science the-sis, Ohio State University, Columbus, Ohio.)

Stratigraphy of Upper Carboniferous and Permian rocksexposed between the Byrd and Nimrod Glaciers

JOHN L. ISBELL, GINA M. SEEGERS, and GREG GELHAR, Department of Geosciences, University of Wisconsin, Milwaukee,Wisconsin 53201

PETER MACKENZIE, Department of Geological Sciences, Ohio State University, Columbus, Ohio 43210

During the austral summers of 1992-1993 and 1993-1994,Upper Carboniferous and Permian rocks exposed

between the heads of the Nimrod and Byrd Glaciers wereexamined to identify the nature of strata exposed in thisregion. Rocks of this age were not previously known to existnorth of the Starshot Glacier (c.f., Laird, Mansergh, and Chap-pell 1971). The area between the Nimrod and Byrd Glacierswas believed to occupy a high which separated strata insouthern Victoria Land from strata in the central Transantarc-tic Mountains (c.f., Elliot 1975, pp. 493-536; Collinson et al. inpress). The purpose of this paper is the following:

to describe the late Paleozoic strata in this region,• to define the outcrop belts for rocks in the central

Transantarctic Mountains and southern Victoria Land,• to compare and contrast strata in the two areas, and• to define the extent of the depositional basin/basins for

late Paleozoic rocks in the Transantarctic Mountains.Late Paleozoic strata in the area between the Nimrod and

Byrd Glaciers were found to consist of the following, inascending order:• interstratified diamictite, coarse-grained sandstone, and

laminated siltstone;• interstratifled black shale and fine-grained sandstone;• thick fine-to-medium grained sandstone; and• interstratifled coarse-grained sandstone, shale, and coal.Respectively, these rocks are laterally continuous with strataof the Pagoda, Mackellar, Fairchild, and Buckley Formationsexposed in the Beardmore Glacier region. We propose thatthese formational names be extended into the Nimrod-Byrdarea. Upper Carboniferous and Lower Permian strata in thecentral Transantarctic Mountains are continuous from the

Byrd Glacier to the Ohio Range. Paleocurrent orientationsfrom these rocks display regional directions toward the pre-sent Weddell Sea (Collinson et al. in press); these orientationssuggest that the rocks were deposited within the same deposi-tional basin.

Late Paleozoic strata in the area between the Nimrod andByrd Glacier differ from rocks exposed in southern VictoriaLand to the north of the Byrd Glacier. In southern VictoriaLand, a discontinuous diamictite is overlain by interbeddedsandstone and coal-bearing shale (Bradshaw, Harmsen, andKirkbride 1990). Regional paleocurrent directions for thesestrata are toward northern Victoria Land, opposite of those inthe central Transantarctic Mountains (Barrett and Kohn 1975,pp. 329-332). Differences in strata on opposite sides of theByrd Glacier support the hypothesis that this glacier marksthe position of a major Cenozoic strike slip fault (c.f., Grindleyand Laird 1969) and that strata in the central TransantarcticMountains and southern Victoria Land were deposited in twoseparate basins.

Rocks of the Pagoda rest unconformably on Precambrianand lower Paleozoic rocks in the area between the Nimrodand Byrd Glaciers. The Pagoda is 180 meters (m) thick andlaterally continuous across the study area, except at MountCerberus, where it fills erosional depressions on the top ofthe Devonian Alexandria Formation. Lithofacies consist ofunstratified diamictite, crudely stratified diamictite, lenticu-lar sandstone within diamictite, coarse-grained sheet sand-stone, and laminated shale deposits. These are interpreted aslodgement till, melt-out till, sub- or englacial meltwaterchannel, outwash stream, and lacustrine deposits, respec-tively. These lithofacies and the presence of numerous stri-

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ated surfaces suggest deposition from wet-based terrestrialglaciers.

Black shales of the overlying Mackellar Formation are insharp contact with diamictite and sandstone of the PagodaFormation. Lonestones are extremely rare in these shales andwere observed only in the lower 1.5 m. Two coarsening-upwardsequences occur within rocks of the Mackellar Formation.These sequences consist of basal shales that grade upward intointerstratified cross-laminated sandstone (0.01-0.1 m thick)and shale (0.1-0.5 m thick); the shale in turn grades into hori-zontally and cross laminated sandstone (1-10 m thick). Sand-stone at the top of the lower sequences is in sharp contact withblack shale of the overlying sequence. The second sequencecoarsens upward into medium-grained sandstone of theFairchild Formation. Shales in the Mackellar were depositedfrom suspension in a basinal setting. Sandstones were intro-duced into this environment as underfiow currents in front of aprograding deltaic system. The sharp lower contact of theMackellar Formation is a flooding surface and suggests rapiddestruction of the late Paleozoic ice sheets followed by floodingof the depositional basin. The sharp contact separating the twocoarsening-upward sequences is also a flooding surface anddue to its widespread distribution across the Byrd-Nimrod areaindicates a rapid rise in basinal water levels.

Basal medium-grained sandstones of the 150-rn-thickFairchild Formation contain dipping foreset beds 1-5 rn thickThese foresets dip at 4-16 0 and grade downward into fine-grained sandstone that interfingers with shale in the underlyingMackellar Formation. Upward, the Fairchild is characterized bysandstone filled channel-form structures. Deltaic sedimenta-tion characterizes the lower Fairchild, whereas rocks in theupper portions of the unit were deposited by braided streams.

The 250(+) -m-thick Buckley Formation consists predomi -nantly of coarse-grained sandstone (5-40 m thick) interstrati-fled with shale (0.5-5 rn thick) and coal (0.05-0.3 m thick)beds. The sandstones occur as sheets, which contain numer-ous downstream accreting macroforms surfaces and sand-stone-filled channel structures. The Buckley was depositedwithin a braided stream depositional system.

Compression, impression, silicified peat, and silicifiedlogs were collected from the Buckley Formation in the Geolo-

gist Range and the All Black Nunataks and at Mount Cerberusand Turbidite Hill. Sandstones contain abundant silicifiedlogs, some of which are contained within large deformedmudstone clasts. The presence of mudstone clast suggestslumping of cutbanks into the adjacent channel. The associ -ated logs were probably transported only a few hundredmeters or less. Silicified peat and logs in the Nimrod-Byrdarea occur lower in the Buckley Formation than similar fossilsin the Beardmore Glacier region. These fossils may be the old-est silicified Permian plant material in the centralTransantarctic Mountains.

We are grateful to Nicholas Rowe, Shaun Norman, andMike Roberts for their help in the field. Dr. Rowe collectedmost of the plant fossils reported in this paper. These fossilsare being examined at the paleobotanical laboratory at theOhio State University. Logistics in Antarctica were providedby Antarctic Support Associates, the U.S. Navy Squadron VXE-6, Ken Bork Air Ltd., and the National Science Foundation.This research was supported by National Science Foundationgrant OPP 91-18495.

References

Barrett, P.J., and B.P. Kohn. 1975. Changing sediment transport direc-tions from Devonian to Triassic in the Beacon Supergroup ofsouth Victoria Land, Antarctica. In K.S.W. Campbell (Ed.), Gond-wana geology. Canberra: Australian National University Press.

Bradshaw, M.A., F.J. Harmsen, and M.P. Kirkbride. 1990. Preliminaryresults of the 1988-1989 expedition to the Darwin Glacier area.New Zealand Antarctic Record, 10(1), 28-48.

Collinson, J.W., J.L. Isbell, D.H. Elliot, M.F. Miller, and J.M.G. Miller.In press. Transantarctic Basin. In J.J. Veevers (Ed.), Paleo -Pacificmargin of Gondwana (Geological Society of America Memoir).New York: Geological Society of America.

Elliot, D.H. 1975. Gondwana basins in Antarctica. In K.S.W. Campbell(Ed.), Gondwana geology. Canberra: Australian National Univer-sity Press.

Grindley, G.W., and M.G. Laird. 1969. Sheet 15, Shackleton Coast geo-logic map of Antarctica, 1:1,000,000. In Antarctic Map Folio Series,Plate XfV Folio 12—Geology. New York: American GeographicalSociety.

Laird, M.G., G.D. Mansergh, and J.M.A. Chappell. 1971. Geology of thecentral Nimrod Glacier area, Antarctica. New Zealand Journal ofGeology and Geophysics, 14(3), 427-468.

Geodynamic links between the Transantarctic Mountainsand Tethys

RASOUL B. SoRIulArn and EDMUND STUMP, Department of Geology, Arizona State University, Tempe, Arizona 85287-1404

The Transantarctic Mountains, extending for approximately3,500 kilometers, constitute a major morphotectonic

boundary between the Precambrian craton of East Antarcticaand the continental "collage" of West Antarctica (figure 1;Elliot 1985, pp. 39-61). The genesis of the TransantarcticMountains has been attributed to an extensional regime in the

antarctic crust, with the mountains forming the shoulder of arift system on the east antarctic side (e.g., Fitzgerald et al. 1986;Stern and ten Brink 1989). Therefore, the TransantarcticMountains do not represent an "orogen" resulting from con-vergence of tectonic plates but, rather, a "taphrogen" relatedto fault-block uplifts of a thinning crust.

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