BEZRUKOVA E., N. KULAGINA, P. LETUNOVA & S. KRAPIVINA

Limnological Institute SB RAS, 664033, Irkutsk, Ulan-Batorskaya St., 3, Russia. bezrukova@lin.irk.ru

A 5.0 Ma year record of vegetation and climate changes from Lake Baikal rift basin, East Siberia, Russia

Lake Baikal is an ancient lake and contains a long record of the Earth's environmental changes, covering several million years in the sediment. The Lake Baikal area is dominated by the continental high-pressure zone related to global climate. Knowledge of its vegetation history is very important for understanding the world's vegetation history and climate. In Eastern Siberia only a little pollen data is currently available for interpreting this history. Long cores from Lake Baikal's sediments are useful for palynological study of long-term changes in climate and vegetation. On the other hand, mire sediments from the lake's coastal areas record the local vegetation history over a relatively short period. As well, average sedimentation rates in the lake are very small. The whole Holocene corresponds to less than 1 m of the uppermost part of the cores, which sometime is disturbed by turbidities. The Holocene mire sediments are stratigraphically sequential and have a thickness of several meters. To understand the history of the ecosystem around the lake it is important to synthesize the results from it and from mires in the coastal areas of the lake.

Combined pollen record from the lake's sediments and from its near-shore peat bogs forms the basis for reconstructing the vegetation and climate history for the period covering the last 5 Ma. The sediment cores are time control based on sediment magnetic properties and on many AMS radiocarbon dates. The vegetation consisted of forest mainly with Tsuga spp., Picea sec. Eupicea, Pinus s/g Diploxylon and open herb-rich vegetation were persisted from 5 to 2.6 Ma. Climatic conditions were moist and mean annual temperatures some 6-8°C higher than compared to those of today. The observed succession from Tsuga spp., Picea sec. Eupicea, Pinus s/g Diploxylon dominated forest to Abies-Larix-Pinus s/g Haploxylon dominated forest, and finally to a forest with Pinus s/g Diploxylon, Pinus s/g Haploxylon, Larix and Betula indicates a progressive decrease of temperature and moisture during the period of 2.6 towards the Holocene.

The work is supported by the Baikal-RFBF Grant, Project N 01-05-97206