Skip to Main Content
Book Chapter

Reconstruction of a high-latitude, postglacial lake: Mackellar Formation (Permian), Transantarctic Mountains

By
Molly F. Miller
Molly F. Miller
Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA
Search for other works by this author on:
John L. Isbell
John L. Isbell
Department of Geosciences, University of Wisconsin, Milwaukee, Wisconsin 53201, USA
Search for other works by this author on:
Published:
August 01, 2010

The Lower Permian Mackellar Formation is well exposed in a 10,000 km2 outcrop belt in the Nimrod, Beardmore, and Shackleton Glacier areas of the Transantarctic Mountains. This formation directly overlies glacial deposits and provides a unique glimpse of high paleolatitude conditions during the last icehouse to greenhouse transition. The unit records deposition in the Mackellar Lake or Inland Sea (MLIS), a fresh-water body at ~80° S paleolatitude that was broadly analogous to Glacial Lake Agassiz and was filled by fine-grained turbidites. Low total organic carbon (TOC) content and predominant vitrinite and inertinite are consistent with a low influx of organic matter from a sparsely vegetated, recently deglaciated terrain. A widespread but low-diversity ichnofauna and variable (although low overall) levels of bioturbation suggest oxic conditions and a bottom fauna restricted to areas of low sedimentation. Integration of sedimentologic, organic geochemical, and paleobiologic information with results of climate models and characteristics of modern lakes enhances reconstruction of parameters that controlled the functioning of the lake as an ecosystem. Regression equations relating mean annual temperature and mean depth of modern lakes to the number of ice-free days applied to the MLIS indicate ice cover from two to five months a year. Estimates of the depth of mixing and depth to the thermocline, based on maximum length, maximum width, and area, suggest a mixing depth of ~50 m and a thermocline of ~20 m. The MLIS probably was stratified during the summer and was dimictic, with overturns occurring after fall cooling and after ice melt; mixing was enhanced by turbidity currents. Productivity was low, as recorded by the low TOC, but organic matter fixed in the surface water of the lake may have been degraded and not recorded in the sediments. In spite of its high paleolatitude, the MLIS as reconstructed was dynamic and biologically active; the same probably was true of other Permian postglacial lakes.

You do not currently have access to this article.

Figures & Tables

Contents

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
Search for other works by this author on:
Luis A. Buatois
Luis A. Buatois
Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada
Search for other works by this author on:
Geological Society of America
Volume
468
ISBN print:
9780813724683
Publication date:
August 01, 2010

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal