We present the results of a comprehensive study of Holocene sediments from high-mountain Lake Sagan-Nur located in East Sayan. The lake is freshwater and has glacial origin. The sediments have been studied by X-ray diffractometry (XRD), IR spectroscopy, laser grain-size analysis, X-ray fluorescence analysis, AMS (14С) and 210Pb dating. The mineral composition of lake bottom sediments is dominated by phyllosilicates, quartz and feldspars. The method of mathematical modeling of their complex XRD profiles was used for correct identification of layered silicates. It has been established that the structural characteristics and quantitative ratios of these minerals change in response to climate changes in the region. The study of sediments composition and, especially, the precision mineralogical-crystallochemical analysis of layered silicates allowed us to reconstruct the climatic conditions of sedimentation.

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, SiO2 bio determination, AMS, and 210Pb 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.

––We present the results of comprehensive studies of Holocene bottom sediments from the shallow hypersaline (mineralization up to 282 g/L) Lake Bolshoi Bagan, located in the East Baraba lowland (south of Western Siberia). The research methods include X-ray diffractometry (XRD), IR spectroscopy, laser granulometry, scanning electron microscopy, elemental analysis of sediments and pore water, radiocarbon (14C AMS) dating. It has been found that during the Holocene an intensive authigenic mineral formation took place in the lake basin; gypsum, halite and carbonates of calcite-dolomite series dominate among the newly formed mineral phases. Mg-calcites with different Mg contents, excess-Ca dolomites, aragonite and occasionally Mg-siderite have been found in the assemblage of carbonate minerals by mathematical modeling of complex XRD patterns. Mineralogical and crystallochemical studies, supplemented by the results of geochemical analyses, allowed us to identify four stages of the evolution of Lake Bolshoi Bagan in the Holocene, due to regional climate variations. The boundaries of the stages in general correspond to the boundaries of the climatostratigraphic phases by the Blytt–Sernander system: Stage I (the end of the Boreal) – the lake formation, humid climate; Stage II (Atlantic) – climate aridization, shallowing of the lake; Stage III (Subboreal) – unstable climate, frequent change of conditions; Stage IV (Subatlantic) – moderately cool and dry climate.

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 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.

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.

Abstract. Our study of the Holocene sediments of shallow saline Lake Bolshoy Bagan located revealed the following stages of the lake evolution: (I) Appearance and maturing of the lake 9.1 5.8 ka BP; (II) rise in water level 5.8 2.3 ka BP; and (III) shallowed lake 2.3 0 ka BP.

Abstract. We present the results of the study of the Holocene sediments from two shal low lakes of different salinity located in the East Baraba lowland (Southwestern Siberia). The research methods: X-ray diffractometry (XRD), IR spectroscopy, laser particle size analysis, AMS dating, etc. By the mathematical modeling of complex XRD patterns Mg-calcites with different Mg contents, excess-Ca dolomite and aragonite have been established in the assemblages of carbonate minerals. Based on studies of mineralogical-crystallochemical features and quantitative ratios of Ca-Mg carbonates the evolution stages of lakes corresponding to the regional cycles of aridization/humidization were identified and the correlations with global climatic events were carried out. The obtained results is an important source of new information about the Holocene climate in the Southwestern Siberia.

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.

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 lacustrine sediments are unique natural archives that store records of environmental and climatic changes. We present results of study of the Late PleistoceneHolocene sediments of freshwater Lake Baunt, located in the permafrost zone in northern Transbaikalia. The sediments were studied by X-ray diffraction (XRD), IR spectroscopy, laser granulometry, elemental analysis, AMS dating, etc. The results of mineral analysis of the bottom sediments with an age of ~18 ka showed that they are mainly represented by phyllosilicates, quartz, and feldspars. By the mathematical modeling of complex XRD patterns chlorite, muscovite, illite, mixed-layer illitesmectite and chloritesmectite, and kaolinite identified among the phyllosilicates. It was established that variations of their structural features as well as quantitative proportions in the section are in high correlation with the climate changes and lake level fluctuations. The results obtained helped to reconstruct the evolution of the Lake Baunt basin controlled by the regional climate throughout the Late PleistoceneHolocene.

—The bottom sediments of lakes with different mineralization located in the basins of inland areas are high-resolution archives of climate and environmental changes. We present results of study of the Late Pleistocene–Holocene sediments of freshwater Lake Baunt, one of the lakes of the Baunt (Tsipa) depression in the permafrost zone in northern Buryatia. The sediments were studied by XRD, IR spectroscopy, laser granulometry, elemental analysis, AMS dating, etc. Mineral analysis of the bottom sediments with an age of ~18 ka has revealed predominant phyllosilicates, quartz, and feldspars. Mathematical modeling of complex XRD spectra made it possible to identify chlorite, muscovite, illite, mixed-layer illite–smectite and chlorite–smectite, and kaolinite among the phyllosilicates. We have determined their structural and crystal-chemical features and quantitative proportions in the section (800 cm long core), which vary in accordance with the climate cycles and lake level fluctuations. The results obtained helped to reconstruct the evolution of the Lake Baunt basin controlled by the regional climate throughout the Late Pleistocene–Holocene. This paper continues a series of our publications concerned with the reconstruction of the Late Pleistocene–Holocene climate in East Siberia by comprehensive studies of the mineral composition of sedimentary sections of small lakes.

Представлены результаты исследования карбонатсодержащих донных осадков малого минерального озера Иткуль (Западная Сибирь). Методы исследования - рентгеновская дифрактометрия (XRD), ИК‑спектроскопия, лазерная гранулометрия, элементный анализ и др. Моделированием XRD-профилей карбонатов функцией Пирсона VII идентифицированы карбонатные фазы, определены их количественные соотношения. Сопоставлением карбонатной записи с литологическими, геохимическими данными в датированном осадочном разрезе воссоздана эволюция озёрного бассейна в голоцене, обусловленная климатическими изменениями. Зафиксированы минералогические сигналы проявления на территории юга Западной Сибири глобального климатического события, известного как событие Бонда 4.

—We present results of research into the mineral composition of the Holocene sediments of Lake Malye Chany of the Chany lake system located in the Baraba steppe and comprising three lakes: Bol’shie Chany, Malye Chany, and Yarkul’, connected by channels. The sediments were studied by XRD, IR and Raman spectroscopy, laser granulometry, analysis of stable 18O and 13C isotopes, elemental analysis (XRF), etc. Mineral analysis has revealed predominant quartz, feldspars, and carbonates and subordinate gypsum, bassanite, pyrite, mica, chlorite, and kaolinite. Mathematical modeling of the XRD spectra of carbonates, using Pearson VII function, made it possible to identify the carbonate phases and determine their quantitative proportions. The obtained high-resolution carbonate record providing information about the stratigraphic distribution of carbonates in the dated section was compared with the available lithological, geochemical, and isotope data. Based on these data, we have reconstructed five stages of the Holocene evolution of the Malye Chany basin. It is shown that the proportions of minerals in the section vary in accordance with the lake level fluctuations in the alternating periods of the Holocene regional arid and humid climate. We compared the mineral compositions of the bottom sediments of Lake Malye Chany and Yarkovsky Pool of Lake Bol’shie Chany. The revealed mineral assemblages reflect the local specifics of the lake system and the influence of natural and climatic factors on the inland sedimentation processes.

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.