TRANSBAIKAL HYDRAULIC SYSTEM OF THE PLEISTOCENE

Abstract

The Selengino-Manzurskaya hydrographic network represented arterial river system with valleys built from constratal alluvium of the Manzurskaya suite of the Pleistocene fi rst half. Nowadays it is uplifted and deformed by recent tectonic movements with the range from 620 m to 800 m, which went along with the Baikal cavity downwarping and uplift of the Primorsky range, the Baikal range and the Onotskiy and Olkhinskiy high plateaus of the Western Baikal Area. Ancient vallyes network was consisted of two branches: Anaysko-Sarminskaya and Buguldejsko-Goloustensko-Manzurskaya. Joining together they formed the Upper pre-Lena basin. The Manzurskiy alluvium is the formation of alluvial, shallow-water-lacustrine and deluvial deposits, represented by sandy varieties and lences of pebble gravels. The alluvium geological age, defi ned by study of small rodents bones found in it and thermoluminiscense dating, fluctuates from 1.700 to 78 thousands years. Hydrosystem’s beds bifurcation is connected with fuzzy relief in the period of its functioning. Its transbaikal nature is shown by the presence of exotic distant-transfered pebble of high-scale rounding; by high thickness of constratal alluvium on the modern interstream areas of the Primorskiy range; by alluvium occurences in the Obruchevskiy fault zone (above the lake water area) and in the South-Baikal hollow. We believe that these facts demonstrate the late-Pleistocene origin of the Lake Baikal deep trench.