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Environmental and paleogeographic implications of glaciotectonic deformation of glaciomarine deposits within Permian strata of the Metschel Tillite, southern Victoria Land, Antarctica

By
John L. Isbell
John L. Isbell
Department of Geosciences, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin 53021, USA
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Published:
August 01, 2010

Popular reconstructions of late Paleozoic glaciation depict a single massive ice sheet centered over Victoria Land and extending outward over much of Gondwana. This view is untenable, as interpretations presented here indicate that glaciogenic strata in southern Victoria Land were deposited in a glaciomarine setting, and that ice entered the area from at least two different ice centers on opposite sides of the depositional basin. Reports from other areas also reveal that multiple ice sheets, ice caps, and alpine glaciers diachronously waxed and waned across Gondwana during the Carboniferous and Permian.

Glaciogenic rocks of the Lower Permian Metschel Tillite contain glaciotectonic structures and glaciogenic deposits that include (1) sheared diamictites, (2) thrust sheets, (3) massive and stratified diamictites, and (4) sheet sandstones. These features formed as subglacial deforming beds, thrust moraines at glacial termini, and as glaciomarine deposits associated with temperate glaciers. A glaciomarine setting, rather than a glaciolacustrine setting, is suggested, owing to the abundance of meltwater plume deposits. A wedge-shaped sandstone body at the base of the overlying Weller Coal Measures was deposited as a grounding-line fan. Results of this study imply deposition in ice-marginal glaciomarine settings from ice radiating out of multiple glacial centers. These findings are significant because multiple glaciers, covering a given area, contain considerably less ice volume than a single massive ice sheet. Therefore, the waxing and waning of multiple ice masses during the late Paleozoic would have influenced global climate and eustatic sea level much differently than would have a single massive Gondwanan ice sheet.

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GSA Special Papers

Late Paleozoic Glacial Events and Postglacial Transgressions in Gondwana

Oscar R. López-Gamundí
Oscar R. López-Gamundí
Hess Corporation, Houston, Texas, USA
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Luis A. Buatois
Luis A. Buatois
Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada
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Geological Society of America
Volume
468
ISBN print:
9780813724683
Publication date:
August 01, 2010

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