Boulder, here. The project was supported by National Science Founda- belts along the Panthalassan margin of Gondwanaland. Colorado: Geological Society of America. tion grants OPP 89-17348 and OPP 89-15429. Elliot, D.H. 1992. Jurassic magmatism and tectonism associated with Gondwanaland break-up: An antarctic perspective. In B.C. Alabaster and R.J. Pankhurst (Eds.), Magmatism and the causes of References continental break-up (Special Publication No. 68). London: Geo- logical Society of London. Barrett, P.J., D.H. Elliot, and J.F. Lindsay. 1986. The Beacon Super- Elliot, D.H., and D. Larsen. 1993. Mesozoic volcanism in the central group (Devonian-Triassic) and Ferrar Group (Jurassic) in the Transantarctic Mountains, Antarctica: Depositional environment Beardmore Glacier area, Antarctica. In M.D. Turner and J.F. and tectonic setting. In R.H. Findlay, R. Unrug, M.R. Banks, and J.J. Gondwana Eight: Assembly, evolution and Splettstoesser (Eds.), Geology of the central Transantarctic Moun- Veevers, (Eds.), tains (Antarctic Research Series, Vol. 36). Washington, D.C.: Ameri- dispersal. Rotterdam: Balkema. can Geophysical Union. Larsen, D. 1988. The petrology and geochemistry of the volcaniclastic Collinson, J.W., J.L. Isbell, D.H. Elliot, M.F. Miller, and J.W.G. Miller. In upper part of the Falla Formation and Prebble Formation, Beard- press. Permian-Triassic Transantarctic basin. In J.J. Veevers and C. more Glacier area, Antarctica. (Unpublished master of science the- McA. Powell (Eds.), Permian-Triassic Pangaean basins and fold- sis, Ohio State University, Columbus, Ohio.)

Stratigraphy of Upper Carboniferous and Permian rocks exposed 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

uring the austral summers of 1992-1993 and 1993-1994, Byrd Glacier to the Ohio Range. Paleocurrent orientations D Upper Carboniferous and Permian rocks exposed from these rocks display regional directions toward the pre- between the heads of the Nimrod and Byrd Glaciers were sent Weddell Sea (Collinson et al. in press); these orientations examined to identify the nature of strata exposed in this suggest that the rocks were deposited within the same deposi- region. Rocks of this age were not previously known to exist tional basin. north of the Starshot Glacier (c.f., Laird, Mansergh, and Chap- Late Paleozoic strata in the area between the Nimrod and pell 1971). The area between the Nimrod and Byrd Glaciers Byrd Glacier differ from rocks exposed in southern Victoria was believed to occupy a high which separated strata in Land to the north of the Byrd Glacier. In southern Victoria southern Victoria Land from strata in the central Transantarc- Land, a discontinuous diamictite is overlain by interbedded sandstone and coal-bearing shale (Bradshaw, Harmsen, and tic Mountains (c.f., Elliot 1975, pp. 493-536; Collinson et al. in press). The purpose of this paper is the following: Kirkbride 1990). Regional paleocurrent directions for these to describe the late Paleozoic strata in this region, strata are toward northern Victoria Land, opposite of those in • to define the outcrop belts for rocks in the central the central Transantarctic Mountains (Barrett and Kohn 1975, Transantarctic Mountains and southern Victoria Land, pp. 329-332). Differences in strata on opposite sides of the • to compare and contrast strata in the two areas, and Byrd Glacier support the hypothesis that this glacier marks • to define the extent of the depositional basin/basins for the position of a major Cenozoic strike slip fault (c.f., Grindley late Paleozoic rocks in the Transantarctic Mountains. and Laird 1969) and that strata in the central Transantarctic Late Paleozoic strata in the area between the Nimrod and Mountains and southern Victoria Land were deposited in two Byrd Glaciers were found to consist of the following, in separate basins. ascending order: Rocks of the Pagoda rest unconformably on Precambrian • interstratified diamictite, coarse-grained sandstone, and and lower Paleozoic rocks in the area between the Nimrod laminated siltstone; and Byrd Glaciers. The Pagoda is 180 meters (m) thick and • interstratifled black shale and fine-grained sandstone; laterally continuous across the study area, except at Mount • thick fine-to-medium grained sandstone; and Cerberus, where it fills erosional depressions on the top of • interstratifled coarse-grained sandstone, shale, and coal. the Devonian Alexandria Formation. Lithofacies consist of Respectively, these rocks are laterally continuous with strata unstratified diamictite, crudely stratified diamictite, lenticu- of the Pagoda, Mackellar, Fairchild, and Buckley Formations lar sandstone within diamictite, coarse-grained sheet sand- exposed in the Beardmore Glacier region. We propose that stone, and laminated shale deposits. These are interpreted as these formational names be extended into the Nimrod-Byrd lodgement till, melt-out till, sub- or englacial meltwater area. Upper Carboniferous and Lower Permian strata in the channel, outwash stream, and lacustrine deposits, respec- central Transantarctic Mountains are continuous from the tively. These lithofacies and the presence of numerous stri-

ANTARC11C JOuRNAL. - REVIEW 1994 35 ated surfaces suggest deposition from wet-based terrestrial gist Range and the All Black Nunataks and at Mount Cerberus glaciers. and Turbidite Hill. Sandstones contain abundant silicified Black shales of the overlying Mackellar Formation are in logs, some of which are contained within large deformed sharp contact with diamictite and sandstone of the Pagoda mudstone clasts. The presence of mudstone clast suggest Formation. Lonestones are extremely rare in these shales and slumping of cutbanks into the adjacent channel. The associ- were observed only in the lower 1.5 m. Two coarsening-upward ated logs were probably transported only a few hundred sequences occur within rocks of the Mackellar Formation. meters or less. Silicified peat and logs in the Nimrod-Byrd These sequences consist of basal shales that grade upward into area occur lower in the Buckley Formation than similar fossils interstratified cross-laminated sandstone (0.01-0.1 m thick) in the Beardmore Glacier region. These fossils may be the old- and shale (0.1-0.5 m thick); the shale in turn grades into hori- est silicified Permian plant material in the central zontally and cross laminated sandstone (1-10 m thick). Sand- Transantarctic Mountains. stone at the top of the lower sequences is in sharp contact with We are grateful to Nicholas Rowe, Shaun Norman, and black shale of the overlying sequence. The second sequence Mike Roberts for their help in the field. Dr. Rowe collected coarsens upward into medium-grained sandstone of the most of the plant fossils reported in this paper. These fossils Fairchild Formation. Shales in the Mackellar were deposited are being examined at the paleobotanical laboratory at the from suspension in a basinal setting. Sandstones were intro- Ohio State University. Logistics in Antarctica were provided duced into this environment as underfiow currents in front of a by Antarctic Support Associates, the U.S. Navy Squadron VXE- prograding deltaic system. The sharp lower contact of the 6, Ken Bork Air Ltd., and the National Science Foundation. Mackellar Formation is a flooding surface and suggests rapid This research was supported by National Science Foundation destruction of the late Paleozoic ice sheets followed by flooding grant OPP 91-18495. of the depositional basin. The sharp contact separating the two coarsening-upward sequences is also a flooding surface and due to its widespread distribution across the Byrd-Nimrod area References indicates a rapid rise in basinal water levels. Barrett, P.J., and B.P. Kohn. 1975. Changing sediment transport direc- Basal medium-grained sandstones of the 150-rn-thick tions from Devonian to Triassic in the Beacon Supergroup of Fairchild Formation contain dipping foreset beds 1-5 rn thick south Victoria Land, Antarctica. In K.S.W. Campbell (Ed.), Gond- These foresets dip at 4-16 0 and grade downward into fine- wana geology. Canberra: Australian National University Press. grained sandstone that interfingers with shale in the underlying Bradshaw, M.A., F.J. Harmsen, and M.P. Kirkbride. 1990. Preliminary Mackellar Formation. Upward, the Fairchild is characterized by results of the 1988-1989 expedition to the Darwin Glacier area. New Zealand Antarctic Record, 10(1), 28-48. sandstone filled channel-form structures. Deltaic sedimenta- Collinson, J.W., J.L. Isbell, D.H. Elliot, M.F. Miller, and J.M.G. Miller. tion characterizes the lower Fairchild, whereas rocks in the In press. Transantarctic Basin. In J.J. Veevers (Ed.), Paleo -Pacific upper portions of the unit were deposited by braided streams. margin of Gondwana (Geological Society of America Memoir). The 250(+) -m-thick Buckley Formation consists predomi- New York: Geological Society of America. nantly of coarse-grained sandstone (5-40 m thick) interstrati- Elliot, D.H. 1975. Gondwana basins in Antarctica. In K.S.W. Campbell (Ed.), Gondwana geology. Canberra: Australian National Univer- fled with shale (0.5-5 rn thick) and coal (0.05-0.3 m thick) sity Press. beds. The sandstones occur as sheets, which contain numer- Grindley, G.W., and M.G. Laird. 1969. Sheet 15, Shackleton Coast geo- ous downstream accreting macroforms surfaces and sand- logic map of Antarctica, 1:1,000,000. In Antarctic Map Folio Series, stone-filled channel structures. The Buckley was deposited Plate XfV Folio 12—Geology. New York: American Geographical within a braided stream depositional system. Society. Compression, impression, silicified peat, and silicified Laird, M.G., G.D. Mansergh, and J.M.A. Chappell. 1971. Geology of the central Nimrod Glacier area, Antarctica. New Zealand Journal of logs were collected from the Buckley Formation in the Geolo- Geology and Geophysics, 14(3), 427-468.

Geodynamic links between the Transantarctic Mountains and Tethys RASOUL B. SoRIulArn and EDMUND STUMP, Department of Geology, Arizona State University, Tempe, Arizona 85287-1404

he Transantarctic Mountains, extending for approximately antarctic crust, with the mountains forming the shoulder of a T3,500 kilometers, constitute a major morphotectonic rift system on the east antarctic side (e.g., Fitzgerald et al. 1986; boundary between the Precambrian craton of East Antarctica Stern and ten Brink 1989). Therefore, the Transantarctic and the continental "collage" of West Antarctica (figure 1; Mountains do not represent an "orogen" resulting from con- Elliot 1985, pp. 39-61). The genesis of the Transantarctic vergence of tectonic plates but, rather, a "taphrogen" related Mountains has been attributed to an extensional regime in the to fault-block uplifts of a thinning crust.

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