LATE PALEOZOIC GLACIATION IN ANTARCTICA: ARE MODELS DEPICTING AN IMMENSE ICE SHEET CORRECT?

Although Gondwana glaciation has long been recognized as an important force driving evolution of Earth systems during the Paleozoic, key questions remain. Many paleogeographic reconstructions for the Mississippian through Early Permian depict a massive ice sheet covering Antarctica and extending outward over much of Gondwana. In these models, ice is shown to have flowed radially outward from a glacial spreading center located over Victoria Land, and to have extended, in one direction, to glacimarine margins in the Ellsworth Mountains and South Africa. In the other direction, models show ice covering northern Victoria Land with glacimarine margins located in Tasmania. Throughout Antarctica, early workers identified diamictites as subglacial tillites deposited from the terrestrial portions of the ice sheet as it waxed and waned across Gondwana.

Reexamination of the glacigenic units in southern Victoria Land, the Darwin Mountains, and the central Transantarctic Mountains reveals that glacilacustrine or glacimarine sediments were deposited within basins, and that subglacial diamictites were deposited only locally along basin margins. Ice free areas were also common. Re-correlation of fossil spores and pollen with Australian palynomorph zones indicate that the Antarctic glacigenic strata are restricted to the Lower Permian. These findings indicate that glaciation was less widespread (temporally and spatially) than previously hypothesized. It is also unlikely that a single ice sheet covered Antarctica throughout the Carboniferous and Permian. Instead, available data are better explained by a short-lived Early Permian glacial interval consisting of multiple ice sheets, or perhaps even consisting of ice caps and alpine glaciers.

Thick glacigenic deposits that are widespread throughout the mountain ranges in Antarctica (e.g., Pensacola Mtns, Ellsworth Mtns, Wisconsin, Range, Scott and Amundsen Glacier areas and northern Victoria Land) have not been examined in the field in the last 25 to 40 years. Significant advances in linking glacial deposits to glacial and glacimarine processes have been made during this time. Reexamination of the glacigenic deposits in these areas may lead to new models of late Paleozoic glacial history, a history that recent studies have begun to clarify.