Glaciations: Mid-Quaternary Glaciations in the Southern Hemisphere

Abstract

The Middle Pleistocene glaciations in the Southern Hemisphere are poorly known, because of the relative lack of emergent land in an ocean-dominated hemisphere and because of the technical problems of absolute dating during this period. The Patagonian glacial sequence in Southern Argentina is the most complete and relatively well dated in that hemisphere. It includes two to three major glaciations, the extent of which is represented by several stages of substantial morainic arcs. Some of these units are inter-bedded with lava flows, which have allowed their 40Ar/39Ar dating and paleomagnetic studies. Erratic boulders on the youngest moraines of this period (late Illinoian/Saalian) have been dated using cosmogenic isotope dating techniques. Their age is estimated to extend over Marine Isotope Stages (MIS) 6 to 22–26 (?). All of the Middle Pleistocene glaciations were less extensive than the maximum glaciation (Great Patagonian Glaciation, GPG), which probably took place during MIS 30–34 (Early Pleistocene). Other regions from which glaciations of the same age are known, include the Northern and Central Andes, Tropical Africa, Tasmania, New Zealand, and Antarctica, as well as and several sub-Antarctic islands, but their record is generally poorly dated.