NEW INSIGHT INTO THE TIMING, DYNAMICS, AND CONSEQUENCES OF LATE PALEOZOIC GLACIATION

The Late Paleozoic Ice Age was a prolonged “icehouse” phase of Earth's climate history that spanned the Late Devonian (~370 Ma) to Late Permian (~260 Ma). Although widely regarded as time of continuous, continental-scale glaciation in the southern hemisphere, recent studies favor a more dynamic interpretation with discrete “glacial” and “non-glacial” periods. Our examination of Carboniferous and Permian strata in eastern Australia reveals eight glacial intervals of 1-8 Ma separated by non-glacial periods of similar duration. Although some marked differences exist between the record in eastern Australia and that of the rest of Gondwana (Isbell et al, 2003, GSA Spec. Pub. 370, p. 5-24), the overall trend appears to record increasingly long-lived and widespread glacial ice from the onset of glaciation in the late Mississippian (~326 Ma) until peak glaciation in the Early Permian (~300-280 Ma), followed by an overall decrease in the duration and extent of glaciers until the ultimate collapse of the ice age in the Late Permian (~259 Ma). The long-term patterns described from eastern Australia match remarkably well with recent interpretations of climate change via the paleofloral and geochemical records as well as the far-field record of eustatic sea-level change. Shorter-term cyclicity within our glacial intervals likely record glacial-interglacial fluctuations similar to those of more recent ice ages, however it is not yet possible to accurately date the duration of these strata.

This study provides the first comprehensive overview and synthesis of the glacial record of eastern Australia. Although an important step forward in our understanding of the record of the Late Paleozoic Ice Age (particularly in this region), an improved global understanding of this important phase of Earth's climate history will require continued geochemical studies of the ancient ocean and atmosphere, improved correlation between paleopolar and paleoequatorial realms, and detailed sedimentological that refine the spatial and temporal distribution of ice in Gondwana.