Deep drilling on Lake Baikal: main results

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 th e lake. Avalanche sedimentation has been established in deep basins of the rift lake. The sedimentation provides a great amount of plant producing met hane in the sedimentary series. The physicochemical conditions at the botto m of deep basins favor formation of gas hydrates, which have been first fou nd 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 al lowed us to obtain a unique paleoclimatic record, which may provide a refer ence model for Asia and the whole continental Northern Hemisphere. Borehole s 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 sp anned 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 pa leoclimates of the Baikal region. The obtained continental climate record s hows a perfect correlation with the oceanic oxygen isotope stratigraphy. Al the same time, climate response in the continental cores is better pronoun ced. The Baikal paleoclimate record bears well-expressed evidence of coolin g that occurred about 2.5-2.8 Ma ago, when ice sheets appeared in various r egions of the Northern Hemisphere. Climate variations over the past 5 Ma ar e considered in detail.