The Bottom Relief Features of the Basins of Lake Baikal

Based on analyzing bathymetric material obtained in different years by using high-precision geophysical equipment featuring multi-beam echo sounders, the main bottom relief features of the South, Middle, and North basins of the Baikal depression have been considered. It has been established that ridge-ravine forms and canyon valleys are well developed on the underwater slope of all depressions. The valleys of the canyons of the Middle and South basins reach their maximum maturity, which is associated with a longer history of the evolution of these basins. The canyon valleys are highly sinuous there, which is associated with the peculiarities of the underlying substrate and fault tectonics. The canyons of the western side of the Baikal depression are predominantly tectogenic in origin, are short, and show a significant steepness of the longitudinal profile; their valleys are mostly rectilinear. The underwater slope along the eastern coast of the North basin and its abyssal surface are complicated by a set of glacial landforms: moraine swells and fan cones formed by turbidite flows during interglacial periods. On the coast, they are continued by very extended swells of lateral and stadial moraines. Tectogenic scarps are widespread in the lower parts of the underwater slopes and usually run parallel to the coastline. It has been established that the flat-convex surfaces of the deltas, which sometimes reach the abyssal surface of the lake, are a very characteristic form of the sloping relief of the South basin. Numerous outcrops of Miocene–Pliocene limnic sediments on the eastern coast of the Middle basin, and the nature of their spatial arrangement suggests that the sedimentary strata of the underwater slope of this basin may be of the same age and be genetically homogeneous with terrestrial strata, which are Miocene–Pliocene in age. Similar deposits of the Tankhoi field on the southern coast of the depression also extend far into the water area of the lake, which supports the existing points of view about the similar history of the development of the South and Middle basins.