GEOLOGICAL STRUCTURE OF CENTRAL LAKE BAIKAL ( according to data of deep-water investigations with manned submersibles, “Pisces” )

A geological section made during deep-water investigations on the southeastern slopes of the island of Olkhon is described and analyzed. In the process of underwater investigations of the Baikal bottom, the greatest lake depth (1,637 m) in this region was reached and, in addition, new important data were obtained permitting a different estimation of the geological nature of the island. A schematic geological map of central Lake Baikal and its stratigraphic column have been devised for the first time. This has permitted us to establish a region of collision interaction between the Precambrian Siberian Plate and Vitim-Barguzin microcontinent and subsequent metamorphism taking place within 520–400 Ma. Deep-water study of the bottom was carried out with the help of manned submersibles “Pisces-VII” and “Pisces-XI” in correspondence with the International Program on Global Changes in Inner Asia on the Basis of Complex Investigations of Lake Baikal.