Intermontane Depressions Research Articles

Geomorphological study of the origin of Mongolian Altai Mountains Lake depressions: implications for the relationships between tectonic and glacial processes

The lake depressions in the Mongolian Altai Mountains, and the issues related to their formation have yet to be thoroughly examined in previous research. Previous studies primarily focused on the paleogeographical evolution and glaciation dynamics of the Altai Mountains. This study presents relationships between tectonic and glacial processes that have formed the lake depressions, such asKhoton, Khurgan, Dayan, Khar (western), and Khar (eastern) in the Mongolian Altai Mountains. The depressions of Khoton, Khurgan, and Dayan lakes are situated along regional fault zones, extending in an northwest-southeast direction, forming intermontane depressions directly connected to the Mongolian Altai Mountains. However, the depressions of Dayan, Khar (western), and Khar (eastern) lakes have been dammed by moraine deposits in the near portion of the depression. The compliance matrix of tectonic geomorphological criteria indicates that the Khoton, Khurgan, Dayan Lake, and Khar (western) Lake depressions are more than 50% compatible. Similarly, the compliance matrix for glacial eomorphological criteria indicates more than 60% compliance for all lake depressions. The Mongolian Altai intermontane depressions are thus of tectonic origin, whereas the lakes have a glacial origin, resulting from dammed moraine sediments. The significanceof this work lies in demonstrating how geomorphological research can be employed to provide a detailed understanding of the pattern of lake depressions.

Irrigation Systems of the Altai: Results and Prospects of Archaeological Studies

We present the fi ndings of studies concerning the irrigation systems of the Altai and outline the directions of their further exploration. Irrigation canals, widely distributed in alpine valleys and intermontane depressions, are streams of the drift type. Most are found in central Altai and in the Chulyshman River valley of eastern Altai. Complex irrigation systems were recorded in the Bilgebash and Sarduma river mouths in the Chuya valley, in the Chulcha River mouth in the Chulyshman valley, and in Tötö, the Kurai basin. Pilot excavations of the main canals showed that wooden troughs had been placed on their bottoms. Radiocarbon analysis of wood from those troughs (Cheba and Oroktoi) suggests that they date to the Late Middle Ages, and a soil sample from the bottom of the canal of the Tenga irrigation system indicates early medieval age. In the 1800s and early 1900s, canals were used by the natives mainly for watering small plots of barley, but also of wheat and rye. Agriculture has been practiced in the Altai at least since the Early Iron Age, having fl ourished, apparently, during the Early Middle Ages. The fi rst irrigation systems must have appeared together with the fi rst farmers; however, taking into account the prolonged use and modifi cations of the main canals, assessing the time of their initial construction is diffi cult.

The role of lake basin history on palynological records from the Upper Kolyma region (northeastern Siberia)

AbstractPaleoecological and modern studies at Priyatnoye Lake, which is located within an intermontane depression in the interior of northeastern Siberia, indicate a similar paleovegetation record as has been documented for nearby mountain valleys, but a history of basin stability and instability that is uncharacteristic of the valley lakes. Analyses of a 385-cm-long core from the western basin of Priyatnoye Lake shows that sediment accumulation began in late Marine Oxygen Isotope Stage 3 (MIS 3), followed by a hiatus during MIS 2, and then continuous accumulation over the past ca. 14,000 cal yr BP. The eastern basin of the lake has a sediment thickness of ~35 cm, suggesting that it intermittently contained water and/or is younger than the western basin. A drop in lake levels between AD 2005 and AD 2009 resulted in the formation of two distinct lakes. This change was caused by the melting of underlying ice wedges and the formation of sinkholes through which the lake water drained. Although the northern coastal lowlands have been the geographic focus of permafrost global warming research, the Priyatnoye study draws attention to the intermontane depressions in northeastern Siberia. While less extensive, these depressions contain organic-rich deposits, are underlain by permafrost, and have the potential to affect future carbon budgets as global temperatures rise and permafrost melts.

Enhanced aridification across the Eocene/Oligocene transition evidenced by geochemical record in the Tajik Basin, Central Asia

The Tajik Basin is an intermontane depression between the mountain ranges of Tian Shan, Pamir, and Hindukush, which is located in the northwestern part of the India-Asia collision zone. Due to the westward retreat of the Neotethys Sea, the paleoenvironment of the Tajik Basin has underwent change from a shallow-sea to a continental semiarid land during the Cenozoic era. This implies that the long-term climatic record in the Tajik Basin can potentially reflect the environmental effects of the changed land-sea distributions controlled by plate collision and global eustatic sea-level changes. In this paper, we present new results of stable oxygen and carbon isotopes of carbonates and chemical weathering indices of bulk samples from the Eocene-Oligocene terrestrial strata (ca. 39–30 Ma) in the center of the Tajik Basin. The temporal variations of oxygen and carbon isotopes of carbonates indicate an isotopic shift across the Eocene-Oligocene transition (~34 Ma), characterized by a relatively positive shift due to the isotopic enrichment in authigenic carbonates in an enhanced aridification episode in the Tajik Basin. This shift was also mirrored by the weakened chemical weathering indicated by the ratios of major oxides across the Eocene-Oligocene transition. Such a regional climatic shift was generally coincident with a remarkable global scale sea-level drop. We suggest that the isolated Paratethys Sea, which was mainly driven by global cooling due to the initial formation of the Antarctica Ice-sheet, together with the decreased seawater evaporation due to lower sea surface temperature, reduced water vapor transport by westerlies to the downwind region, and thus intensified the aridification in the Tajik Basin began at ~34 Ma. • Reconstructed paleoclimatic record between ~39 and 30 Ma in Central Tajik Basin. • Stable isotopes and chemical weathering indices reveal enhanced aridity at ~34 Ma. • Regression of the Paratethys played a major role in reducing moisture transport.

Application of Methodology for Soil Quality Assessment in Intermontane Depressions of the Cis-Baikal Region

Application of Methodology for Soil Quality Assessment in Intermontane Depressions of the Cis-Baikal Region

Similarities and distinctions in the genesis of salt-affected soils in different regions of the south of Eastern Siberia

Soil salinization is determined by a set of factors, which can be subdivided into sources and mechanisms. The south of Eastern Siberia is characterized by the mountainous topography with numerous intermontane depressions, a large number of tectonic faults and springs. Hydromorphic surface-saline soils of sulfate and chloride-sulfate chemistry predominate. In Tuva, the share of chloride salinity increases, which is associated with the presence of salt rocks, and the percentage of soda-saline soils decreases sharply. In Buryatia, the percentage of soda salinity is higher than in other regions. In Khakasia, despite the gypsum deposits, the percentage of soda-saline soils is also significant, which is related to irrigation practices. Sharper differences are observed in individual basins of the regions, the salinity of which is determined by the presence of salinization sources in the given area, as well as by the mechanisms and conditions of soil salinization. For example, the presence of permafrost prevents the leaching of chlorides from the profile leading to the development of chloride salinization, or an increase in the alkalinity associated with the magnesium bicarbonate in slightly arid intermontane depressions of Buryatia and high–mountain depressions of Tuva.

Landscape-geochemical specifics of steppe geosystems in Baikal basin

Landscape-geochemical studies of the steppe geosystems of the Lake Baikal catchment area revealed the spatial regularities of matter differentiation of the geosystem components and the landscape-geochemical features of geosystems at different levels of organization. The steppe geosystems occupy mainly the piedmont plain and the bottoms of the submontane and intermontane depressions. Dry steppe geosystems are confined to the lowest belt in the altitudinal zonality system. Regional and local features of landscape-geochemical differentiation of matter are diagnosed by the ratio of radial and lateral heterogeneity of the distribution of chemical elements. The steppe calcium and subtaiga sour-calcium geosystems are characterized by a weak radial contrast ratio in the content of different chemical elements in soils against the background of a well-pronounced lateral contrast, and at the contact of steppe and subtaiga geosystems. Lateral differentiation of the content of chemical elements is practically absent. Thus, at the contact of many low-mountain and piedmont landscape-geochemical systems (LGS) in the Preolkhon region, ecotones have been formed, which determine very weak differences between the soil parameters of forest and steppe geosystems. This has necessitated the display of types of conjugations (TC) on landscape-geochemical maps for a more correct reflection of the nature of the matter differentiation. In connection with the predominance of heterolithic conjugations in mountainous conditions, for a correct assessment of the lateral migration of matter, it is advisable to single out individual links of conjugated rows of facies formed on homogeneous bedrocks.

DISTRIBUTION OF THE FORMS OF MERCURY OCCURENCE IN THE PROFILE OF TYPICAL SOILS OF SOUTH SIBERIA

The article presents original data on the gross concentration of Hg in typical soils of steppe and forest-steppe landscapes, lacustrine-accumulative plains, as well as systems of intermontane depressions in Southern Siberia. Quantitative estimates of the distribution of Hg in soil profiles in the Tomsk Region, Altai Territory, and the Republic of Buryatia. The features of the distribution of Hg concentrations in soil profiles depending on the particle size distribution, hydrogen index, electrical conductivity and magnetic susceptibility were revealed. The forms of occurrence of Hg in soil profiles of different types of soils have been determined. In the studied soil types, the largest proportion of Hg falls on forms that evaporate in the temperature range 170-4000C, i.e. highly volatile low molecular weight organomercury compounds, HgCH3, Hg (CH3) 2), HgCl2, HgS alkyl radicals, aryl radicals, as well as in organo complexes. These forms are the most accessible and toxic for living organisms, the proportion of inaccessible and inert forms is minimal.

Pliocene trace fossils from oyster substrates in the Nijar Basin, Betic Cordillera, southern Spain

The Almería-Níjar Basin is a Neogene, intermontane depression marginal to the Mediterranean in southern Spain in the vicinity of El Argamasón, Andalucia. The Pliocene Cuevas Formation rests unconformably on the Upper Messinian rock succession in the Carboneras Fault Zone. The Cuevas Formation is a coarse-grained, bioclastic-rich, calcarenite to calcirudite shoreface deposit. Oysters, namely Saccostrea cucullata (Born), are locally common and preserve a moderate diversity of borings: Caulostrepsis taeniola Clarke; Entobia isp.; Gastrochaenolites isp. aff. G. lapidicus Kelly and Bromley; Maeandropolydora isp. cf. M. sulcans Voigt; Oichnus paraboloides Bromley; and Talpina isp. aff. T. hirsuta Voigt. All represent domiciles except for the predatory O. paraboloides trace. This suite of ichnotaxa is assigned to the Entobia ichnofacies sensu Bromley and Asgaard; they are comparable, particularly, with the Boulder Assemblage of the Pliocene of Rhodes, Greece. Physical disturbance is an important parameter in favouring this pattern of infestation, whether the bored clasts are boulders or oyster valves.

Tectonic stress in the structures of the Northern Priokhotie (Magadan region) according to geological data

Tectonic fracturing of the Mesozoic and Cenozoic structures was studied in the Northern Priokhotie (Magadan region). The cataclastic analysis method and the statistical method of fracture density analysis were used to reconstruct their state of stress. It is revealed that the folded structures of the Arman’-Viliga synclinorium are subjected to horizontal shearing; the axis of maximum compression is sublatitudinal (azimuth 67°, angle 12°); extension is submeridional (azimuth 161°, angle 19°). In the Uda-Murgal volcanic arc, horizontal extension with shear takes place; the compression axis is directed to NW (azimuth 259°, angle 29°), and the extension axis to NE (azimuth 152°, angle 26°). In the Okhotsk-Chukotka volcanogenic belt, volcanic structures are in the field of varying tectonic stresses, from predominant horizontal extension to horizontal shear. The Cenozoic intermontane depressions of the Miocene – Pliocene ages are subjected to horizontal shear; the compression axis is directed to NE (azimuth 214°, angle 29°), and the extension axis to NW (azimuth 121°, angle 4°). The results of the comparative analysis of the stress states in the above-mentioned areas reliably show that the diversity of the stress state types is statistically related to the structural positions of the studies sites. Such diversity cannot be explained by an influence of active faults, or by any consecutive superposition of deformations at different stages, despite the fact that the deformations have complicated the observed pattern of the stress states. We conclude that each subsequent geodynamic stage only introduced additional elements into the previous structure, but did not completely transform it.

Mineralogy, geochemistry and U-Pb zircon age of the Karaotkel Ti-Zr placer deposit, Eastern Kazakhstan and its genetic link to the Karaotkel-Preobrazhenka intrusion

The Karaotkel deposit of fossil Ti-Zr placers is situated in the north-western edge of the Zaysan intermontane depression in Eastern Kazakhstan. The geological structure of the mineral sands is characterized by complex morphology and a two-layered assembly, formed as the result of long-term regional geodynamic processes during the Meso- and Cenozoic.Our study is aimed to establish a genetic model for the formation of the continental Karaotkel Ti-Zr placers by utilising novel data on geology, mineralogy, geochemistry and geochronology. Sedimentological facies analyses indicate an environment of coastal wave-built formation of the Late Cretaceous kaolin-dominated weathering crust and Paleogene sediments of the North Zaysan formation. A set of geochemical indices is applied on the base of key geochemical parameters of placer composition to allow quantitative and qualitative assessment and to establish genetic trends.Mineralogical composition of the heavy fraction of the productive sediments of the Ti-Zr placer (horizon “A” of the North Zaysan formation) was determined by XRD and microprobe-probe analyses. Microprobe analyses determined the elemental composition of mineral grains of zircon, ilmenite, monazite, staurolite, titanite, epidote and gold. Gold and monazite were found also as micro-inclusions in minerals. The sediments of the horizon “A” are characterized by elevated grades of light rare-earth elements (LREE) over heavy rare-earth elements (HREE).The weathering processes reveal a gradual transition from a moderately warm and humid climate to a cold and dry climate as the placer deposit was formed. The intercalations between horizontal- and crossbedding characterize the conditions of placers’ sedimentation by eluvial, eluvial-alluvial, alluvial-lacustrine and lacustrine environments. U-Pb dating of zircons from the productive horizon “A” of the Karaotkel placer deposit showed a crystallization age of 287 ± 1 Ma. This is identical with the age of the Karaotkel-Preobrazhenka multi-phase igneous intrusion suggesting that it can be considered as the source of the Karaotkel Ti-Zr placer. In addition, comparative analyses of elemental composition of zircons confirmed that monzonites and syenites of earlier phases of the Karaotkel-Preobrazhenka intrusion are the likely source rocks for the Karaotkel mineral sands.The formation of these Ti-Zr placers comprise the following stages: 1) establishment of the bedrock of the Karaotkel-Preobrazhenka multiphase igneous intrusion of the Permian Cisuralian epoch; 2) development of weathering crust during Upper Cretaceous period; 3) washing-out of the weathering crusts during the North Zaysan formation in the Paleogene, and 4) differential redeposition by temporary streams that resulted in the accumulation of Ti and Zr minerals.

Genesis of Water and Dissolved Matter in Soda Lakes of Nizhnii Kuitun of the Barguzin Depression

We examine the formation conditions for the resources and chemical composition of mineral lakes located in the vicinities to the unique natural site of the Barguzin intermontane depression, Nizhnii Kuitun. Presented are the results from studying the surface structure of this sand massif. It is shown that its formation is associated with peculiar features in the tectonic development of the Barguzin depression. It is pointed out that the block of rocks forming Nizhnii Kuitun is broken up by tectonic faults into several smaller parts, and this had a determining impact on its modern appearance. The lakes under study are situated in the northern part of Nizhnii Kuitun, in the Nukhe-Nur urochishche, in the topographically clearly pronounced drainless depression. The formation of this depression occurred during the uplifting stage of the block of rocks when intensively fragmented rocks, located at the interface of the faults, lagged behind in vertical movement. The depression receives the runoff of surface and underground waters which drain sedimentary deposits of Nizhnii Kuitun. Data are provided to demonstrate that the lakes are situated in the ablation funnels of sand-clay sediments. On the basis of a quantitative determination of the chemical composition of water and gases, it is proved that seepage waters of sandy sediments of Nizhnii Kuitun and nitrogenous fissure-vein waters play the main role in the formation of resources and chemical composition of the lake water in the area of the Nukhe-Nur urotshistshe. The hydrological-hydrogeological model of the formation of the lakes under study is suggested. In a dry period when the amount of water infiltrating through the sand deposits of Nizhnii Kuitun decreases, the proportion of deep fissure-vein waters increases; therefore, water mineralization increases in the lakes as well as fluorine, sodium, tungsten and molybdenum contents. In wet years, the contribution of drainage waters to the formation of the lake’s resources increases, and the concentration of these elements decreases.

ТИПЫ, РАЗМЕЩЕНИЕ И ПЕРСПЕКТИВЫ ПАЛЕОГЕНОВЫХ И НЕОГЕНОВЫХ РОССЫПЕЙ ЗОЛОТА В ЗАПАДНО-КАЛБИНСКОМ ЗОЛОТОНОСНОМ РАЙОНЕ (ВОСТОЧНЫЙ КАЗАХСТАН)

Актуальность исследования обусловлена необходимостью расширения сырьевой базы золотодобывающих предприятий Казахстана и научного обоснования перспектив вовлечения в эксплуатацию палеогеновых и неогеновых россыпных месторождений золота, условия формирования и закономерности размещения которых до настоящего времени не получили всесторонней оценки, хотя их продуктивность многократно превосходит потенциал россыпей четвертичного возраста. Цель: укрепление сырьевой базы россыпного золота Республики Казахстан и повышение эффективности ее освоения за счет изучения палеогеографических, палеоклиматических и неотектонических условий локализации россыпей кайнозойского возраста и уточнения критериев их поиска на площади Западно-Калбинского золотоносного района в Восточном Казахстане. Объекты: палеоген-неогеновые россыпи золота, древние россыпелокализующие элементы рельефа и вмещающие отложения. Методы: сбор и анализ имеющихся данных по россыпям золота палеогенового и неогенового возраста, распределению и формационной принадлежности золоторудных объектов; уточнение параметров древних долин и внутригорных впадин путем дешифрирования космических снимков; проведение геолого-геоморфологических наблюдений; составление карты россыпной золотоносности на геоморфологической основе и реконструкция геоморфологической зональности; картирование палеогеновых и неогеновых отложений, изучение их золотоносности, детальное комплексное изучение наиболее полных разрезов с отбором проб. Результаты. Установлено, что россыпи палеогенового и неогенового возраста локализуются в древних долинах и впадинах, период их формирования охватывал длительный промежуток времени – от олигоцена до плиоцена. По генезису среди них выделены аллювиальные, аллювиально-пролювиальные и пролювиальные, в том числе локализованные во впадинах большеобъемные аллювиально-пролювиальные россыпи с преобладанием мелкого и тонкого золота. Основной закономерностью размещения палеоген-неогеновых россыпей является их пространственно-парагенетическая связь с коренными источниками, локальная геоморфологическая зональность определяет геолого-геоморфологические типы россыпей.

Gully erosion of soils in intermontane depressions of the Selenga middle mountains (Republic of Buryatia).

Gully erosion of soils in intermontane depressions of the Selenga middle mountains (Republic of Buryatia).

Assessing the Geoecological Status of the Floodplain-Terrace Complex of the Tuul River Within Ulaanbaatar (Mongolia)

The paper gives characteristics of natural and anthropogenic factors responsible for the geoecological situation inside the boundaries of the floodplain-terrace complex of the Tuul river within Ulaanbaatar. Among them, the geological structure and orography (occurrence in the intermontane depression), the specific character of climate-forming (frequent temperature inversions) and hydrological (mainly summer feed by rain water) characteristics, the degree of economic development (high pressure on the central city zone) and population density in administrative districts, etc. have been distinguished. Results obtained from hydro- and geochemical analyses of the territory and published previously (during 2009–2013) were used in the typification of the areas of the floodplain-terrace complex of the Tuul river according to the intensity of anthropogenic impact. An analysis was made of the sources of pollution, primarily of large industrial enterprises and facilities of housing and communal services: combined heat and power plants, industrial, meat-packing and biological plants, the poultry farm, sewage treatment plants, etc. Based on a comparative analysis of average concentrations of the component composition of the river waters and floodplain soils, maximum exceedances of maximum and approximate permissible concentrations of pollutants were determined. Categories of the intensity of anthropogenic impact were identified to vary from decreased to very high. It is shown that, in spite of a high degree of geochemical understanding of the urban territory of Ulaanbaatar, no detailed investigations have been made within the floodplain-terrace complex of the Tuul river. The first-time assessment of the geoecological status of the sites across the study territory determined the migration routes of chemical substances and correlated their occurrence in natural environment with the sources of pollution. According to the intensity of anthropogenic impact, for each site of the floodplain-terrace complex we have suggested environmental and water protection measures. Results of the assessment are presented in the form of cartographic material.

Landscape-Ecological Approach in Identifying Distribution Patterns of Pollutants Within the Lake Baikal Drainage Basin

With a view to conducting a comprehensive assessment of pollution of the water bodies within the Lake Baikal drainage basin using dimensionless indicators of the water chemical composition, the problems of identifying and testing the indicators were dealt with, which are necessary for determining the sources and levels of pollution and assessing the contributions of the tributaries to lake pollution and the self-cleaning ability of the waters. The methodology of geoecological monitoring as suggested by these authors is based on identifying correlations between polluters and environmental sites by examining technogenic material of from the sites as mixtures, and material from the sources as their components. Identification of the spatio-temporal structure of pollution involves analyzing the landscape organization of the lake drainage basin and the distribution patterns of pollutants. Substantiation of the observation and monitoring network, extrapolation of monitoring results and display of real-time data used landscape mapping methods. An analysis was made of the landscape and geochemical differentiation of the Lake Baikal drainage basin, and the unified indicators of water composition relating water pollution to natural conditions were ranked. The study revealed areas of geosystems with different rates of organic matter decomposition, i. e. the water areas of the lake with a different self-cleaning ability of the waters, and the areas of the drainage basin, the soils of which are responsible for the formation of waters of different types. The resulting contours were generalized in accordance with the scale of the map for the spatial differentiation of biogeochemical parameters of the landscape organization of the drainage basin. The highest decomposition rate of organic matter is characteristic for taiga dark-coniferous geosystems of optimal development, submontane and intermontane depressions and valleys of Khamar-Daban Range, and the lowest rate is typical for goletz and subgoletz geosystems as well as for taiga forests along the western coast of Lake Baikal.

Soil Formation in the Taiga–Steppe Ecotone of the Selenga Mountains, Western Transbaikal Region

A new view on the genesis and properties of soils in landscapes of the taiga–steppe ecotone in the Selenga Mountains of western Transbaikalia is suggested with due account for the modern approaches toward soil classification in Russia. The specific environmental conditions—dry and sharply continental climate, mountainous topography with pronounced intermontane depressions, and predominantly coarse-textured parent materials—affect the pedogenesis. Soddy-podzolic soils (Albic Retisols) are formed on the interfluves, and raw-humus burozems (brown taiga soils), including residual-calcareous burozems (Eutric Cambisols) are developed on the upper parts of slopes. Eutric Cambisols are characterized by the high base saturation, a sharp drop in the humus content down the profile, and a pronounced pedogenic structural organization of the mineral mass. Albic Retisols display textural differentiation. Gray-humus and dark-humus soils are characterized by the immediate transition from the humus-accumulative part to the parent material as evidenced by the physicochemical properties. Fine sand and coarse silt fractions predominate in these soils, and second (Ca-bound) fractions of humic and fulvic acids predominate in the composition of their humus. These are base-saturated loamy sandy or light loamy soils with a neutral of slightly alkaline reaction. The middle-profile horizons are poorly pronounced. These soils compose a genetic series in the landscape-geochemical catena of the northern macroslope of the Tsagan-Daban Range.

Landscape-typological mapping of the Baikal region (within the boundaries of the Irkutsk region)

The aim of the work is to create a landscape-typological map of the territory to study the territorial differentiation of recreational activities. The variety of landscapes of the Baikal region is determined by a large number of landscape-forming factors, as well as the heterogeneity of the conditions in which geocomplexes are formed. A landscape-typological map of the territory was created on a scale of 1: 500 000. As an input data for creating the map, electronic topographic maps of the territory, space images of Landsat 5, 7, 8 for different seasons and years (including mosaic of MrSID for 2000 and Hansen mosaic for 2016), digital elevation models, landscape, geological, soil and geobotanical maps of different scale were used. A total of 56 landscape units were identified: 13 highland (goltzy, sub-mountain, reduced development mountain-taiga), 6 medium-mountain (limited development taiga), 14 lowland (optimal development mountain-taiga, steppe), 13 foothill (limited development taiga, optimal development taiga, subtaiga, steppe), 10 - intermontane depressions and valleys (limited development taiga, optimal development taiga, steppe). The conclusions drawn about the landscape structure and recreational properties of the territory are generalized. More detailed landscape research is needed, including comprehensive field work to clarify the landscape map and assess the recreational significance of landscapes.

Proglacial damlakes in eastern Transbaikalia: New insight into the Pleistocene paleogeography

Paleogeographic reconstructions for the Samarovo, Taz, Murukta, and Sartan glaciations reveal the formation conditions of proglacial lakes dammed by ice in intermontane depressions and valleys of large rivers in eastern Transbaikalia. Middle-Late Pleistocene climate change is reconstructed using spore-pollen spectra from Pleistocene sediments in northern Transbaikalia. The age and lifetime of proglacial lakes are constrained by radiocarbon, thermoluminescence, and varve chronology of their bottom sediments in the periglacial zone. The lake levels remain recorded in sediments produced by deposition and erosion along the former lake shores, as well as in morphology and lithology variations of terminal moraines. A large proglacial lake, with a maximum level of 1020 m, occupied vast areas in Transbaikalia and its surroundings during the Samarovo glaciation. After the glaciers degraded, the Amur River system expanded into the area of closed lake basins in the southeastern Baikal region, including North China and Mongolia. The obtained results have implications for the Middle-Late Pleistocene history of lake deposition.

The Neogene Ostracod Genus Advenocypris from the Intermontane Depressions of the Southeastern Altai

This paper presents new data on ostracods of the genus Advenocypris. The distribution of these ostracods in the Neogene deposits of the intermontane depressions of Central Asia is analyzed. Species of this genus were selective regarding their habitats. This habitat specificity can be used to reconstruct the paleogeography of the depositional environments, origin and connections of water bodies in Central Asia. A new species of the genus Advenocypris is described. The previously known species of this genus are illustrated.