DEEP DRILING ON LAKE BAIKAL: MAIN RESULTS

Abstract

The paper presents the results of ten-years deep drilling on Baikal (joint Russian-American-Japanese Baikal Drilling Project). During the project run, five sets of boreholes were drilled in various geomorphic structures of the lake. Avalanche sedimentation has been established in deep basins of the rift lake. The sedimentation provides a great amount of plant producing methane in the sedimentary series. The physicochemical conditions at the bottom of deep basins favor formation of gas hydrates, which have been first found in the fresh-water lake. A precise age control of the Baikal sedimentary sections based on detailed paleomagnetic data as well as their continuity and a considerable length allowed us to obtain a unique paleoclimatic record, which may provide a reference model for Asia and the whole continental Northern Hemisphere. Boreholes on the Akademichesky Ridge yield a record of more than 10 Ma with the age resolution of 500 to 250 years. The boreholes on the Bugul'deika saddle spanned a section of 600 ka with the age resolution of 25 to 100 years. Distribution of diatoms and, hence, of biogenic silica, palynological data, and data on chemistry and mineralogy of sediments give insight into the paleoclimates of the Baikal region. The obtained continental climate record shows a perfect correlation with the oceanic oxygen isotope stratigraphy. At the same time, climate response in the continental cores is better pronounced. The Baikal paleoclimate record bears well-expressed evidence of cooling that occurred about 2.5-2.8 Ma ago, when ice sheets appeared in various regions of the Northern Hemisphere. Climate variations over the past 5 Ma are considered in detail.