Chemical composition of sediments in Baikal deep-water boreholes as a basis for reconstructions of climatic and environmental changes

Abstract

Earlier reconstructions of climatic and environmental changes from data of deep-water drilling on the Akademichesky Ridge in Lake Baikal were based both on the content of biogenic silica or the abundance of diatom valves and on the results of X-ray diffraction (XRD) analysis of the sediment mineralogy. It was established that clay minerals are the main carrier of information about climatic variations in a drainage basin. The content of biogenic silica strictly correlates with two chrystallochemical parameters: the abundance of smectite beds in illite–smectite and the abundance of illite. However, detailed analysis of clay minerals calls for exclusive XRD techniques without mass determination of minerals in the sediments of long Baikal cores. We propose a new approach to determine the mineral composition of bottom sediments, based on their chemical composition. We compared the average chemical compositions of Pleistocene, Pliocene, and Miocene core sediments from the boreholes BDP-96 and BDP-98 and sediments of the Paleo-Barguzin River avandelta and recognized groups of chemical elements marking warm and cold climatic periods. However, the difference in the chemical compositions of sediments in warm and cold periods is insignificant. Since an XRD analysis of mineral composition is usually performed for short time intervals, it was necessary to identify cold and warm intervals by the mineral composition calculated from the chemical composition of sediments. The mineral contents were estimated using the Selektor software. Based on the average contents of chemical elements, we computed the mineral composition of the bottom sediments throughout the BDP-98 section and studied its warm and cold periods. We have established that feldspars weakly respond to climatic changes, their contents show minor variations in warm and cold epochs, whereas the contents of mica minerals change seriously. Thus, clay minerals, together with biogenic silica, are a good indicator of paleoclimatic environmental changes.

Oxygen isotope composition of diatoms from sediments of Lake Kotokel (Buryatia)

“…Lithology, mineralogy, and chemistry of bottom sediments have important implications for the history of lakes, sediment provenance, and responses of lake systems to global change (Sklyarov et al, 2010;Kuzmin et al, 2014). Variations in oxygen isotope composition (δ 18 O) of limnic fossils found in sediments, such as foraminifera, ostracods, or gastropods, bear imprint of their environments and can be used as a climate proxy (Faure, 1986).…”

Mineral and geochemical composition of the Onega Ice Lake sediments

“…Number in brackets shows quantity of samples biogenic silica, are a good indicator of paleoclimatic environmental changes. The number of smectite layers in illite-smectite increased during the interglacials and reached a maximum in the Late Holocene (Kuzmin et al 2014).…”

“…According to the data from the article of academician Kuzmin M.I., knowledge of changes in the content of clay minerals within the bottom sediments of Lake Baikal is a crucial tool for climate reconstructions (Kuzmin et al 2014). Clay minerals, like Table 2 The chemical composition of the "pink horizon" relative to the varved clays above and below Content 10.10-10.14 m (layers above "pink horizon") 10.37-10.42 m ("pink horizon") 10.42-10.46 m (layers below the "pink horizon") The number of sheet silicates and Fe 3+ in the pink horizon is much higher than in other horizons of varved clays according to X-ray spectral fluorescence and X-ray diffraction analysis (Table 2).…”

Source Apportionment of Inorganic Solutes in Surface Waters of Lake Baikal Watershed

“…The metamorphic rocks rich in alkali and alkaline-earth metals, such as plagiogneisses, amphibolite shists, amphibolites, marbles, etc. [55], that condition high TDS content in water are more widespread in the northern and central parts of the western coast of Lake Baikal than in the southern Cisbaikalia or in the lower reaches of the Selenga River [56]. The differences in water chemistry among the rivers were also clearly visible in anionic composition of water.…”