The Late Paleozoic Ice Age: Size and Duration of Glacial Events

The main phase of the late Paleozoic Ice age (LPIA) lasted ~90 million years beginning in western Gondwana (South America and possibly Africa) during the Mississippian (late Visean) and ending in eastern Gondwana (Australia) at the end of the Middle Permian (Capitanian). During this interval, discrete glacial events, which lasted from 1 to 8 million years and separated by ice free conditions of equal duration, shifted west to east across the supercontinent. New data compiled by researchers working in basins scattered across the supercontinent suggest that at no time was Gondwana completely covered by ice, but rather smaller glacial centers developed, expanded and contracted, and disappeared only to be later replaced by ice centers located farther east. Initiation of the main phase of Gondwana glaciation occurred in western South America with alpine glaciation in the Visean and Namurian. Small ice sheets developed later in the Pennsylvanian with the greatest extent of ice occurring during the Early Permian. At that time, numerous, discontinuous glacial centers were scattered across the supercontinent. Following the Sakmarian, glaciation shifted to Australia where a number of smaller ice centers continued into the middle Permian. Identification of the relationship between eustacy and glaciation during the LPIA is problematic. Ultimately, the relationship is a volume problem, as large changes in sea level require large changes in ice volume. Therefore, small glacial events produced only small changes in sea level, whereas, larger events had a more profound influence on eustacy.