DETAILED HOLOCENE CLIMATE RECORD FROM THE CARBONATE SECTION OF SALINE LAKE TSAGAN-TYRM ( West Baikal area )
E.V. Sklyarova, , E.P. Solotchinab, E.G. Vologinaa, N.V. Ignatovaa†, O.P. Izokhb, N.V. Kulaginaa, O.A. Sklyarovac, P.A. Solotchinb, V.N. Stolpovskayab, N.N. Ukhovaa, V.S. Fedorovskiid and O.M. Khlystove
a Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, 128 ul. Lermontova, Irkutsk, 664033, Russia
b V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3 prosp. Koptyuga, Novosibirsk, 630090, Russia
c A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, 1a ul. Favorskogo, Irkutsk, 664033, Russia
d Geological Institute, Russian Academy of Sciences, 7 Pyzhevskii per., Moscow, 109017, Russia
e Limnological Institute, Siberian Branch of the Russian Academy of Sciences, 3 ul. Ulan-Batorskaya, Irkutsk, 664033, Russia
Keywords: Saline lake, carbonates, modeling of XRD profiles, diatoms, pollen, stable isotopes, geochemistry, paleoclimate, Holocene, West Baikal area
Pages: 237-258
Abstract
We present results of a complex study of evaporite sediments from one of the small saline lakes with carbonate sedimentation in the Ol’khon area and substantiate their high significance for paleoclimatic reconstructions. The mineral composition of the bottom sediments was studied by XRD analysis, IR spectroscopy, scanning electron microscopy, elemental analysis (SR-XFA), etc. By decomposition of the complex XRD profiles of carbonate minerals into individual peaks by Pearson VII function, we identified carbonate phases in each sample and determined their proportions. A high-resolution carbonate record has been obtained for the first time for the lacustrine sediments. It bears the information about the stratigraphic distribution of Mg-calcites (a continuous series of structurally disordered low- to high-Mg calcites, up to Ca-dolomites), in which the amount and proportions of phases with different Mg contents are controlled by Mg/Ca, salinity, and total alkalinity of the lake water changing depending on the climatic cycles and lake level fluctuations. Comparison of the carbonate record for the Holocene section dated by the radiocarbon (14C) method with results of lithological, diatom, and palynological analyses, data on stable isotopes (δ18 O and δ13 C), and the distribution of some geochemical indicators of climatic changes permitted the reconstruction of the intricate evolution of the Lake Tsagan-Tyrm basin, which was controlled by the regional climate from the Atlantic period to the present time. The directed change in various characteristics of essentially carbonate sediments evidences that the Ol’khon regional climate has become more arid in recent 6.5 kyr. Moreover, drastic frequent changes of climate and, correspondingly, the Lake Tsagan-Tyrm water level in different periods of its existence have been revealed. The widespread saline and brackish lakes in southern East Siberia, Mongolia, and North China and the highly informative (in terms of paleoclimate and paleolimnology) carbonate sediments might help to recognize the general tendencies of paleoclimate changes and local fluctuations in Central Asia.
|
