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Journal of Geographical Sciences - This article describes the lake basins of the Jom-Bolok volcanic region in the East Sayan (the largest manifestation of the Holocene eruptions in Central Asia).... 相似文献
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Koji Shichi Hikaru Takahara Sergey K. Krivonogov Elena V. Bezrukova Kenji Kashiwaya Akihide Takehara Toshio Nakamura 《Quaternary International》2009,205(1-2):98
Climatically driven Late Pleistocene and Holocene vegetation changes were reconstructed based on pollen records from the sediments of Lake Kotokel and Cheremushka Bog, located on the eastern shore of Lake Baikal. The described paleoenvironmental record has higher resolution than records collected from Lake Baikal and unites individual events identified in prior studies of bottom and onshore cores. Remarkable shifts in landscapes and expansions of index plants are as follows. Forest tundra and/or forest steppe landscape with birch, spruce, Artemisia, and Poaceae prevailed at ca. 50–25 14C kyr BP. Tundra and/or steppe vegetation dominated by Artemisia and Poaceae was typical for the Last Glacial Maximum. The expansion of shrub birch and willow occurred at ca. 15.5 14C kyr BP. Two peaks of spruce expansion at ca. 47.5–42.4 14C kyr BP (Karginian time) and at ca. 14.5–13 ka (Bølling-Allerød warm intervals) suggest that the condition were more humid than today. A slight increase in Artemisia at ca. 11–10.5 14C kyr BP (13–12 ka) was indicative of the Younger Dryas event. An expansion of birch forests with fir at ca. 12–6.4 ka suggests higher humidity. The currently dominant Scots and Siberian pine forests with birch expanded since 6.4 ka. 相似文献
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Shchetnikov A. A. Bezrukova E. V. Kerber E. V. Belozerova O. Yu. Kuzmin M. I. Ivanov E. V. Krainov M. A. Filinov I. A. Nechaev I. O. 《Doklady Earth Sciences》2019,486(1):503-506
Doklady Earth Sciences - The first results of tephrochronological studies of Late Pleistocene–Holocene volcanic eruptions in the Zhom-Bolok River valley (Eastern Sayan) are reported. Based on... 相似文献
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E.P. Solotchina E.V. Bezrukova P.A. Solotchin O. Shtok A.N. Zhdanova 《Russian Geology and Geophysics》2018,59(11):1419-1432
We present integrated mineralogical, geochemical, and palynological data for Late Pleistocene-Holocene bottom sediments of Lake Arakhlei located in the Beklemishev tectonic basin in the southern Vitim Plateau (central Transbaikalia). The sediment samples were studied by X-ray diffractometry (XRD), Fourier-transform infrared (FTIR) spectroscopy, laser particle sizing, spore-pollen analysis, radiocarbon (14C AMS) dating, and XRF spectrometry. The cored 128 cm long section of lake sediments consists of two units: One is composed mainly of layered silicates (illite-smectite, illite, chlorite, chlorite-smectite, muscovite, and kaolinite) and organic matter (OM) but no carbonates from 0 to 80 cm and the other contains authigenic Ca-Mg carbonates (up to 30%) of Mg-calcite and excess-Ca dolomite from 80 to 128 cm. The sediments also contain a rare mineral weddellite CaC2O42H2O discovered for the first time in Transbaikalian lakes. The evolution of Lake Arakhlei and its drainage basin comprised four stages, with pollen zones that mark the Late Pleistocene and Holocene climate history of the Beklemishev basin. The reconstructed history of Lake Arakhlei for the past ~ 15,500 years followed general climatic changes in the Northern Hemisphere. Thus, integrated research, including detailed analysis of mineral components and spore-pollen assemblages in lake sediments, is a workable tool for studying climatic controls of continental sedimentation. 相似文献
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An assessment is made of the uniqueness of modern vegetation in Prebaikalia as a biogeographical entity. It is shown that its complex structural-cenotic diversity is represented on the new universal geobotanical map of vegetation at a scale of 1:500 000. The map legend, constructed on the principles of V. B. Sochava’s multidimensional and multistage structural-dynamical classification of plant communities, displayed more than 160 cenotic subdivisions of vegetation of Prebaikalia representing its different types. An analysis is made of the development paths of vegetation for assessing its evolutionary potential. The study revealed the main stages of philocenogenesis in the Late Cainozoic. Its main directions have been revealed, which are important for understanding the characteristics of the region’s modern vegetation cover. The heterogeneity and heterochronicity of modern cenotic diversity of vegetation is shown. Emphasis is placed on the evolutionary processes of vegetation of Prebaikalia in the Holocene which can last for at least 40 thousand years. In this connection, it is proposed to change interpretation of the Holocene Optimum as an optimum for the evolution of the dark-coniferous taiga of Siberia. It is shown that the genetic linkages of the cenotic structure of modern vegetation cover in Prebaikalia are clearly pronounced via regional-typological categories of vegetation reflecting profound links of modern vegetation with natural-geographical regions where its philogenetic processes were taking place in interaction with the general evolution of the natural environment. An analysis is made of the significance of the floristic and cenotic boundaries having an important biogeographical significance. Such boundaries, on the one hand, are the footprint of the past evolutionary processes in vegetation, and in the natural environment as a whole, and, on the other, indicate the dynamical potential of possible changes in vegetation under global climate change. 相似文献
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J. Platt Bradbury Ye. V. Bezrukova G. P. Chernyaeva S. M. Colman G. Khursevich J. W. King Ye. V. Likoshway 《Journal of Paleolimnology》1994,10(3):213-252
The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake. Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence. On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During glacial periods, the deep basin sediments of Lake Baikal are dominated by rapidly deposited clastics entering from large rivers with possibly glaciated headwaters. On the sublacustrine Academician Ridge (depth = 300 m), however, detailed analysis of the diatom biostratigraphy indicates that diastems (hiatuses of minor duration) and (or) highly variable rates of accumulation complicate paleolimnologic and paleoclimatic reconstructions from these records. 相似文献
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Bezrukova E. V. Reshetova S. A. Volchatova E. V. Kuzmin M. I. 《Doklady Earth Sciences》2022,506(1):687-692
Doklady Earth Sciences - The Central part of the Oka Plateau lying in the East Sayan Mountains is still a poorly studied area of southern Siberia as regards its paleogeography. This gap can be... 相似文献