NEOGLACIATION IN CENTRAL ASIA

Glaciation in Central Asia, with a continental climate, appears to be out of phase with glaciation in maritime Europe and western North America. Radiocarbon dates suggest that glaciers in the Sayan Range, on the border of Siberia and Mongolia west of Hovsgol Lake (51°N; 99°E), last advanced during the early Holocene, probably 7000-9000 14C yr B.P. Glaciers of the Tingis River impounded a lake (Lake Dood-Tsagaan Nur) to a depth of at least 150m within the Darhad Depression. Tingis moraines are massive till terraces pocked with kettles and other stagnant ice features. These appear to be from the local LGM. However, a date of 10,500±130 14C yr B.P. was found for a clam shell from the uppermost preserved lake sediments near the ice dam. Corrected for a reservoir effect of 3550 years (Peck et al., 2000), the date may actually be closer to 7000 14C yr B.P. New 14C dates support this preliminary finding. A woody fiber, possibly a root, from near-shore sands deposited at a high stand of the lake gave an age of 5700±50 14C yr B.P. and bulk sediment dates from peaty, possibly aqueous plant remains, yielded 11,090±60 14C yr B.P. before correction for the reservoir effect. Charcoal fragments of larch wood, from the same sample, gave an age of 9200±4014C yr B.P., and charcoal from 90cm depth in a soil on the Tingis moraine gave an age of 7750±40 14C yr B.P. We conclude that the ?LGM? glaciers advanced during the early Holocene in southern Siberia, when Izzyk Kul, a large lake 2000 km to the southwest, was in a pluvial period. It is likely that increased moisture is responsible for the Tingis advance during this relatively warm period. The apparently missing late Pleistocene global LGM and earlier advances are puzzling. Possibly southern Siberia was too dry then to form large glaciers, but more likely the glaciers were cold-based and debris-impoverished, leaving little trace. In either case, it appears that some late Quaternary glaciations in southern Siberia were asynchronous with those in Europe and North America.