Академическое издательство «Гео»

Keywords: lacustrine morphogenesis, Holocene volcanism, lava-dam lakes, environmental changes, Eastern Sayan.


Lacustrine morpholithogenesis in the Valley of Volcanoes (Eastern Sayan)

A.A. Shchetnikov, E.V. Bezrukova, I.A. Filinov, E.V. Ivanov, and E.V. Kerber

*shch@crust.irk.ru, filinov@crust.irk.ru
**bezrukova@igc.irk.ru, bezrukova@igc.irk.ru, eivanov@igc.irk.ru, kerber62@mail.ru

We examine the lacustrine morpholithosystems of the Zhombolokskii volcanic area in Eastern Sayan. The geomorphological position, the origin and the characteristics of structure and development of the lake depressions are characterized in conjunction with their sedimentary configuration. We developed a morphogenetic classification of the lakes and described the representatives of each variety. It is ascertained that of the most widespread occurrence in the area are the limnetic morpholithosystems of volcanic and glacial-nival origins. They form the basis of the local lake landscapes. Of secondary significance are the water bodies of the fluvial and composite genesis. They were all formed in the postglacial period and in the Holocene. The limnetic morpholithogenesis here is evolving dynamically in conditions of contrasting topography, and a high energy of endogenic and exogenic processes. The sedimentation rates have been calculated. In the lakes of a glacial origin within the goletz belt, the sedimentation rates usually average 7–10 cm/ka, and they reach 20 cm/ka in water bodies of the volcanic genesis. The sedimentation rates approach the avalanching indicators (up to 45,87 cm/ka) in floodplain water bodies of the Sentsa valley that experienced a temporal rise of its local base level of erosion in connection with the formation of the lava-dam Zun-Ukhergei paleo-lake. It is established that the present configuration of Lake Khara-Nur that formed as a result of the damming of the Zhom-Bolok river valley by a lava-flow dates back to about 5500–5000 ka. The lacustrine deposits with the age of 800–700 ya show high concentrations of microparticles of coals giving evidence of an intensification of fire phenomena in the lake’s drainage basin, which appears to record one of the last intensification phases of volcanic activity in the Zhom-Bolok valley.

Keywords: lacustrine morphogenesis, Holocene volcanism, lava-dam lakes, environmental changes, Eastern Sayan.

DOI: 10.21782/GiPR0206-1619-2016-3(37-48)