Causes of glaciation in Siberia on transition from Kasantzevo climate optimum to Zyrjanian ice age (from climate records in Baikal bottom sediments)

We discuss stratigraphic and correlational age modeling of the Baikal sedim ent record and summarize studies of paleoclimate records in cores from vari ous regions of Lake Baikal. The available paleoclimate reconstructions atte st to an abrupt strong Early Wurm glaciation in the Baikal region at the ox ygen isotope substage 5d, (117-105 ka BP). This confirms the existence of a n "additional" glaciation predicted for Siberia from paleoclimate modeling and suggests a regional mechanism responsible for the intensity of this gla ciation, which was better pronounced in Siberia than elsewhere in the North ern Hemisphere. The available data on the Early Zyrjanian glaciation in Siberia provide an insight into the space-time dynamics of the origin of the Early Wurm glacia tion and can account for the discrepancy between a considerable (about 40%) increase in global ice volume at the substage 5d and the lack of physical evidence for glaciation from other regions of the Northern Hemisphere. Cata strophic events of the 5e/5d transition revealed in the Baikal sediment rec ord and in other Siberian data indicate a significant role of Siberia in cl imate-forming processes in the Northern Hemisphere.