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The freshwater Buir Lake in Khalkh Gol soum, Dornod aimag, is located (47° 51' 47° N, 117° 51' 29° E) on the border of Mongolia and Inner Mongolia, China. The northwest and northeast part of the lake is swampy, and is flat in the rest part. This research paper reveals the lithology and some major elements content (SiO2, Al2O3, TiO2, Fe2O3, MgO, K2O, Na2O, MnO and P2O5) of the core sediments and their distribution along the depth and the Chemical Index of Alteration (CIA), which will be a significant factor in restoring environmental change. According to the data of analysis of major elements of Buir Lake sediments, the concentration of SiO2 ranges from 42.92 to 58.29%; Al2O3 = 9.25-12.83%; Fe2O3 = 3.66-4.79%; TiO2 = 0.46-0.62%; MnO = 0.08-0.13%; CaO = 5.73-11.56%; MgO = 1.34-1.81%; Na2O = 0.72-1.50%; K2O = 1.58-2.31%; and P2O5 = 0.14-0.26% respectively. The chemical index of alteration is basically the same as the distribution of SiO2, Al2O3, TiO2, Fe2O3, MgO, K2O and Na2O in the sediments of the lake, but their content at 32.5 cm interval of the core sharply decreases and also increases. This is perhaps due to global climate change. The content and distribution patterns of water-soluble elements, such as CaO, MnO, and P2O5, are negatively correlated with the chemical index of alteration. These lead to conclude that major elements of Buir Lake sediment and Chemical Index of Alteration are closely related to climatic changes in eastern Mongolia pertaining to the Upper Pleistocene and the Holocene epochs. [ABSTRACT FROM AUTHOR]

The Tarvagatai Nuruu National Park, situated in the northern Khangai Mountains in central Mongolia, is dominated by a forest-steppe ecosystem. An extreme continental and semi-arid climate is characteristic for forest-steppe ecosystems in Central Asia and their vegetation is very sensitive to climatic changes and human impacts by pastoralism and tree-logging. In the selected study area, nowadays human impact is exceptionally low, and it has potentially also been in the past. The focus of this paper was to reconstruct vegetation variability, climate dynamics, intensity of human impact and fire dynamics by applying a broad multi-proxy approach on a lacustrine sediment core from a small closed lake in the study area. The analyses include reconstructions of pollen, spores, non-pollen palynomorphs, and charcoal distribution as well as XRF-scanning. Overall, the radiocarbon-dated lacustrine sediment core reveals stable, long-term environmental conditions since the early Holocene (9570 cal yr BP). Palynological results indicate that vegetation varies on a comparably low level. We assume that nomadic pastoralism played a tangential role on the vegetation changes in the study area. Higher values of coprophilous fungi between 9570 and 8350 cal yr BP suggest the highest wildlife activity during the early Holocene. Hence, our multi-proxy data reveal a surprisingly stable vegetation composition and only slight climatic changes in north-central Mongolia for the entire Holocene. An initial moist and warm period from 9570 to 4180 cal yr BP was followed by a period of slightly drier and potentially cooler conditions from 4180 until 430 cal yr BP. The latest period from 430 cal yr BP to present was moist and warm. Fires were in general relatively rare except from a strong phase of fire activity between 3550 and 2960 cal yr BP. • A new multi-proxy record (pollen, NPPs, macro charcoal, XRF-data) from north-central Mongolia. • Detailed high-resolution Holocene palaeoecological record covering the last 9600 cal yr BP. • Reconstructed stable vegetation reflects limited human impact on the vegetation dynamics since the Early Holocene. • Values of coprophilous fungal spores during the early Holocene provide a baseline of wildlife activities. • Extensive fire episode from 3550 to 2960 cal yr BP. [ABSTRACT FROM AUTHOR]