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•The largest endorheic Siberian Lake Chany appeared only 3.6 cal ka BP.•The basin of the lake was a swampy landscape ca. 9–3.6 ka BP with a very low rate of sedimentation.•The lake ...was shallow 3.6–1 ka BP, and then became deep, similar to the modern one.•Development of the lake was controlled by climate and specific topography of its catchment.
Lake Chany is the largest endorheic lake in Siberia whose catchment is entirely on the territory of Russia. Its geographical location on the climate-sensitive boundary of wet and dry landscapes provides an opportunity to gain more knowledge about environmental changes in the West Siberian interior during the Holocene and about the evolution of the lake itself. Sediment cores obtained from the Yarkov sub-basin of the lake in 2008 have been comprehensively studied by a number of approaches including sedimentology and AMS dating, pollen, diatom and chironomid analyses (with statistical interpretation of the results), mineralogy of authigenic minerals and geochemistry of plant lipids (biomarker analysis.). Synthesis of new results presented here and published data provides a good justification for our hypothesis that Lake Chany is very young, no older than 3.6 ka BP. Before that, between 9 and 3.6 ka BP, the Chany basin was a swampy landscape with a very low sedimentation rate; it could not be identified as a water body. In the early lake phase, between 3.6 and 1.5 ka BP, the lake was shallow, 1.2–3.5 m in depth, and it rose to its modern size, up to 6.5 m in depth, during the last millennium. Our data reveal important changes in the understanding of the history of this large endorheic lake, as before it was envisioned as a large lake with significant changes in water level since ca. 14 ka BP. In addition to hydrology, our proxies provide updates and details of the regional vegetation and climate change since ca. 4 ka BP in the West-Siberian forest-steppe and steppe. As evolution of the Chany basin is dependent on hydroclimatic changes in a large region of southern West Siberia, we compare lake-level change and climate-change proxies from the other recently and most comprehensively studied lakes of the region.
Five samples of modern mineral sediments were collected during hydrogeochemical study of the Mogoiskii thermal spring in Northern Transbaikalia. Two of them contain opal as the major component of ...geyserite; carbonates, fluorides, and sodium sulfates predominate in the other three. Calculations of deep temperatures showed that the formation of geyserite was associated with low-temperature hydrotherms and was explained by a decrease in their temperatures upon discharge. Precipitation of easily soluble brine minerals occurs on the evaporation barrier, and they may dissolve completely and disappear in the rainy periods.
The results of lithological and mineralogical studies of the Holocene bottom sediments from the shallow hypersaline (mineralization up to 282 g/L) Bolshoi Bagan Lake, located in the East Baraba ...Lowland (southwestern Siberia), are presented. The research methods included X-ray diffractometry (XRD), infrared spectroscopy, laser grain size analysis, scanning electron microscopy, elemental composition study, and radiocarbon (
14
C AMS) dating. It was found that intensive authigenic minerogenesis occurred in the lake basin during the Holocene. Halite, gypsum, and carbonates dominate among the newly formed mineral phases. Mg-calcites with different Mg contents, excess-Ca dolomites, aragonite, and occasionally Mg-siderite have been established in the assemblage of carbonate minerals by the mathematical modeling of complex XRD patterns. The mineralogical and crystallochemical studies, supplemented by the results of other analyses, allowed us to identify four stages of the evolution of Bolshoi Bagan Lake in the Holocene, due to variations in the regional climate. The boundaries of the stages generally correspond to the boundaries of the climatic stratigraphical phases by the Blytt–Sernander classification: stage I (the end of the Boreal), lake formation, humid climate; stage II (Atlantic), climate drying, shallowing of the lake; stage III (Subboreal), unstable climate, frequent change of conditions; stage IV (Sub-Atlantic), moderately cool and dry climate. The mineralogical signals of the global climatic Bond events in southwestern Siberia have been identified.
We present the results of a comprehensive study of Late Pleistocene–Holocene sediments from Khikushka Lake located in the high-mountain Zhom-Bolok volcanic area (East Sayan Mountains). The lake is ...freshwater, endorheic, and of glacial origin; the age of sediments is ~13.8 ka. The sediments have been studied by X-ray diffractometry (XRD), IR spectroscopy, laser grain-size analysis, scanning electron microscopy, X-ray fluorescence analysis, and AMS dating. Detailed mineralogical studies of the Khikushka Lake sediments have been conducted for the first time. It is shown that feldspars, quartz, phyllosilicates, and amphibole prevail in them. Mathematical modeling of complex XRD patterns allowed us to identify chlorite, illite, illite–smectite, chlorite–smectite, muscovite, vermiculite, and kaolinite among layered silicates. The quantitative ratios of these minerals change significantly from the Pleistocene to the Holocene. Despite the close proximity of the volcanoes and multistage Late Quaternary eruptions in the Zhom-Bolok area, only indirect indications of the presence of pyroclastic material were found in the lacustrine sediments studied. Based on the mineralogical, crystallochemical, lithological, and geochemical studies, five evolutionary stages of the Khikushka Lake basin have been identified. Sedimentation in this basin occurred under the influence of both climatic (glacier activity, lake level fluctuations, lake bioproductivity) and geological (composition of rocks within the catchment, Late Quaternary volcanism) factors.
The results of study of the composition of Quaternary subaerial slope sediments of the new Ulan-Zhalga reference section, 30 m thick (West Transbaikalia), using X-ray diffratometry (XRD), IR ...spectroscopy, laser granulometry, and elemental analysis are presented. The sediments contain quartz, feldspars, clay minerals, carbonates, hematite, and traces of amphibole. It is shown for the first time for the subaerial section that the composition and structure of carbonates indicate climate changes in the Pleistocene and Holocene. The correct identification and determination of the amount of carbonates is based on modeling of their XRD patterns using the Pearson VII function. The sections host two thick units of subaerial sediments with different lithological–mineralogical characteristics, which correspond to two large sedimentation stages. The lower unit formed under moderate wind activity and relatively high moisture, which is evident from a wide occurrence of soil horizons and the presence of low-Mg carbonates. The upper unit, which formed in colder and drier conditions with a higher dynamic of aeolian processes, contains calcite, high-Mg calcite, and excess-Ca dolomite.
We present the results of studying the Holocene sediments of Bolshie Toroki Lake, a shallow brackish lake with carbonate sedimentation and high bioproductivity, located in the eastern part of Baraba ...lowland (southwestern Siberia)
.
The mineral component of bottom sediments was studied by such methods as X-ray diffraction (XRD) analysis, IR spectroscopy, laser granulometry, elemental analysis, and others. By the mathematical modeling of complex XRD patterns, Mg-calcites with different Mg contents and aragonite have been established in the assemblage of carbonate minerals. Their structural and crystallochemical features and quantitative ratios were determined. The obtained high-resolution carbonate record was compared in the dated section with the distribution of the ash content, which is determined by the bioproductivity of the basin, and with a number of geochemical indicators of climate changes. The use of such a complex approach allowed us for the first time to recognize four stages in the evolution of Bolshie Toroki Lake; these stages were caused by cycles of drying/wetting of the regional climate and fluctuations of the lake level in the second half of the Holocene. Stage I (middle of the Atlantic) corresponded to the formation of the lake; stage II (second half of the Atlantic) was characterized by shallowing of the lake in a dry and warm climate; stage III (most of the Subboreal), shallow basin in a dry and cool climate; and stage IV (from the end of the Subboreal until the present) was marked by an increase in the water level of the lake and climate humidization.
The results of studying bottom sediments taken from the high-mountain lake Sagan-Nur located on the Oka plateau (East Sayan Mountains), which is insufficiently studied, are presented. The lake is ...freshwater and has a glacial origin. Comprehensive investigations of the mineral composition of the lake sediments accumulated over the past ~8600 cal. years have been carried out for the first time. The research methods include X-ray diffraction (XRD), infrared spectroscopy, laser granulometry, SiO
2 bio
determination, AMS, and
210
Pb dating. The mineral composition of the bottom sediments is dominated by layered silicates, quartz, and plagioclase; furthermore, the X-ray amorphous component consisting of biogenic silica and organic matter is present. The method of mathematical modeling of their complex XRD patterns is used for correct identification of the layered silicates. It is established that the layered silicate assemblage is stable and is represented by muscovite, chlorite, illite, mixed-layer illite–smectite and chlorite–smectite, and kaolinite. At the same time, the structural characteristics and quantitative ratios of these minerals in the deposits changed significantly in response to changes in the natural environment of the region, which reveals the potential of a number of phyllosilicates (illite, mixed-layer minerals) as indicators of the paleoclimate in the bottom sediments of freshwater basins. The results of studying the sediment composition and, especially, the precision mineralogical–crystallochemical analysis of layered silicates have made it possible to reconstruct the paleolandscapes and climatic conditions of sediment accumulation and to assign them to the respective Holocene sub-stages.
New research results are presented on the processes of carbonate sedimentation in shallow saline lakes of Western Transbaikalia by the example of the Holocene bottom sediments of Sul’fatnoe Lake (the ...Selenga Dauria). The techniques of X-ray diffractometry (XRD), IR spectroscopy, laser granulometry, and isotope and elemental analyses were used. By means of decomposition the XRD profiles using the Pearson VII function, the carbonate phases were identified and their quantitative ratios were determined. The evolution of the lake basin caused by climate changes in the Holocene was reconstructed by comparing the carbonate record to the concentrations determined for the
18
O and
13
C stable isotopes and to lithological, geochemical, and palynological data in the dated sedimentary section.
The results of this study on carbonate-containing bottom sediments of the shallow brackish Lake Itkul, West Siberia, are presented. The study methods applied included X-ray diffractometry (XRD), ...infrared spectrometry, laser granulometry, element analysis, and others. Carbonate phases are identified, and their quantitative relationships are determined by modeling of the XRD carbonate profiles using the Pearson VII function. The comparison of the carbonate record and lithological anf geochemical data on the dated sedimentary section has allowed us to reconstruct the climate-driven Holocene evolution of the lake basin. Mineralogical signals of the global climatic event known as Bond 4 are found in the territory of western Siberia.
The high degree of the influence of regional climatic and natural factors on sedimentation in intracontinental water reservoirs necessitates a comprehensive study of their bottom sediments during ...paleoclimatic reconstructions. Shallow lake basins of the arid and semiarid zones with intense carbonate accumulation are quite promising in the world practice for reconstruction of the climate in the Holocene. The small sizes of lakes determine their exclusive sensitiv ity to environmental changes impacted in sedimentary records. It is considered that deposition of one car bonate or another proceeds from waters oversaturated in carbonate and is controlled by a number of factors: Mg2+/Ca2+ in water, carbonate alkalinity (concentrations of HCO , CO , and H2CO3), salinity, pH, temperature, and organic productivity of the lake, which are controlled by the water balance depending on the climatic conditions. In recent years, we have worked out a new approach to paleoclimatic recon structions based on detailed mineralogical and crystal chemical studies of endogenic carbonates from lake sediments. Identification of an association of carbon ate minerals, their crystal chemical and structural peculiarities, and regularities in the distribution of individual carbonate phases in dated sedimentary sequences of shallow lakes allowed us to obtain a number of high resolution records of the Holocene climate in the Baikal region. This study is aimed at understanding the relationship between associations of newly formed endogenic carbonate minerals and their crystal chemical characteristics in modern sediments of shallow saline and brackish lakes without an outlet occurring closely to each other and under the same climatic conditions with the geochemical specifics of lake waters.
