Collaborative Research: Permian-Triassic Basin History of Southern Victoria Land and the Darwin Mountains

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

9909749 Askin This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative sedimentological, palynological, and paleomagnetic study of Permian and Lower Triassic strata in southern Victoria Land (SVL) and the Darwin Mountains (DM), Antarctica. Results of the study will help constrain the paleoenvironmental, tectonic, biotic, and paleogeographic histories of southern Pangea and provide a unique polar view of the world during an icehouse to greenhouse transition. The assembly and drift of Pangea resulted in heightened orogenic activity and associated development of numerous depositional basins. One of the largest basins was the 10,000+ km long "Gondwanide foredeep" that extended across southern South America, South Africa, the Falkland Islands, Antarctica, and Australia. Antarctica's centralized location between South Africa and Australia, make SVL and DM key areas for testing paleogeographic and paleoclimatic models. Upper Paleozoic and Lower Mesozoic rocks in SVL and DM were deposited during Gondwanaland's drift across the south pole. Based on present plate reconstructions, SVL and DM were located higher than 75 degrees south latitude from 320 to 210 Ma. Despite the putative high latitude position, SVL and DM sedimentary successions record a change from Lower Permian glacial deposits, to Permian fluvial coal measures, to Lower Triassic non-carbonaceous fluvial deposits, and finally to Middle and Upper Triassic fluvial coal measures, with well-developed vegetation during much of this time. Present climatic simulations suggest seasonal climatic extremes within Pangea's polar interior. Discrepancies between the geological evidence and the climate simulations need to be resolved, and may be magnified by incomplete understanding of the influence of paleotopography, large lakes, and river systems at the time of deposition, as well as by incomplete documentation of paleoenvironmental conditions. Furthermore, Late Permian and Triassic mean pole positions for Gondwanaland are not tightly constrained. Paleomagnetic signatures will be recovered from Permian and Triassic petrified wood, silicified peat, and coal, which were cemented during early diagenesis (preliminary results indicate stable remnant magnetizations). Palynological analyses will provide time control for the succession. Objectives of this study include: 1) Determination of a late Paleozoic glacial/deglaciation history for SVL and DM as Gondwana drifted over the south pole, 2) Documentation of Permian strata as a means to better understand the environments of high latitude fluvial coal-bearing deposits, 3) Documentation of Triassic lithofacies as a means to better understand high latitude conditions during the Early to Middle Triassic "coal gap" interval, 4) Providing a well-constrained stratigraphic framework for the Permian to lower Triassic succession, 5) Testing the diachronous and inversion tectonic models for the Panthalassan Margin of southwestern Pangea, and 6) Constructing better paleogeographic models for Gondwana by obtaining new Gondwana reference poles for the Permian and Triassic.