RECONSTRUCTION OF PREGLACIAL TOPOGRAPHY USING A POSTGLACIAL FLOODING SURFACE - UPPER PALEOZOIC DEPOSITS, CENTRAL TRANSANTARCTIC MOUNTAINS, ANTARCTICA

Upper Paleozoic glacial deposits in the central Transantarctic Mountai ns are the basal deposits within a late Paleozoic to early Mesozoic ba sin that formed along the margin of the East Antarctic Craton. This ba sin was a foreland basin throughout much of its his tory, and was part of a larger-scale basin that stretched across the paleo-Pacific margi n of Gondwanaland. Our reconstruction of the preglacial topography in the central Transantarctic Mountains suggests that deposition began wi thin two topographic depressions located on top of eroded rocks of the lower Paleozoic Ross Orogenic Belt. Isopach, paleocurrent, and lithof acies data support such a hypothesis, This interpretation implies that tectonic activity was not a factor in the formation of the deposition al basin, and that little or no tectonic activity was occurring along the adjacent continental margin during glacial deposition. Although gl acial deposits are present all along the paleo-Pacific continental mar gin of Antarctica and Gondwanaland, our findings suggest that initial sedimentation began within a series of discontinuous depocenters. A fl ooding surface that separates upper Paleozoic glacial deposits from ov erlying postglacial black shales in the central Transantarctic Mountai ns is used as a datum for reconstructing the preglacial topography. Th e postglacial flooding surface resulted from flooding of the depositio nal basin following collapse of the Gondwanide ice sheet. Results usin g this approach aided us in reevaluating the factors that controlled t he formation of the depositional basin in Antarctica and in determinin g the tectonic setting of the paleo-Pacific margin of Antarctica durin g deposition of the upper Paleozoic glacial rocks. The use of a floodi ng surface as a datum is a technique that may be useful for reconstruc ting paleotopography in other settings.