SEDIMENTATION IN PROVAL BAY (LAKE BAIKAL) AFTER EARTHQUAKE-INDUCED SUBSIDENCE OF PART OF THE SELENGA RIVER DELTA
E.G. Vologina1, I.A. Kaluginb, Yu.N. Osukhovskayac, M. Sturmd, N.V. Ignatovaa†, Ya.B. Radziminovicha, A.V. Dar'inb, and M.I. Kuz'minc
1Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
b V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
c A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
d Swiss Federal Institute for Environmental Science and Technology (EAWAG), P.O. Box 611, CH-8600 Dubendorf, Switzerland
Keywords: Earthquake, bottom sediments, magnetic susceptibility, diatoms, rate of recent sedimentation, elemental composition, Proval Bay
Pages: 1275-1284
Abstract
The paper presents the results of a comprehensive investigation into the recent sediments of Proval Bay. This bay formed during catastrophic flooding of a big block of land as a result of an earthquake in 1862. Comparison of the sketch map of the bay for 1862 with its modern map shows that the boundary of the Selenga River delta has shifted considerably eastward. The sedimennts of Proval Bay are sands, silty pelite, and pelitic silt. Terrigenous material is predominant and consists of mineral grains and land plant remains admixed with diatom frustules and sponge spicules. In the southwestern part of the bay, turbidites and a soil layer have been found. The latter was buried when the water level in Lake Baikal rose after the construction of the Irkutsk dam in 1959-1964. In the northeastern part of the bay, a peatlike layer has been found in the bottom sediment core. It formed in Lake Beloe, which existed in the Tsagan steppe before the 1862 earthquake. According to diatom analysis, this lake was shallow and eutrophic. The sedimentation rates in different parts of Proval Bay differ greatly and depend directly on proximity to the Selenga River. Variations in the geochemical indicators which reflect the ratio of organic to clastic components in the bottom sediments of the bay are controlled by temperature and water level variations in Lake Baikal.
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