2020 年 41 巻 3 号 p. 261-275
Mongolia is located in the northern Central Asia, and provides an important key archive for research on the past environment in the region. To assess the regional paleoenvironment, this study analyzed a 10.5 m sediment core retrieved from Olgoy Nuur (Lake) in the west central part of Mongolia. The sedimentary features are investigated as environmental proxies, including whole and mineral grain size, water, organic matter, carbonate, amorphous silica contents, and variations in elements analyzed by X-ray fluorescence. The core was divided into three units based on lithology and analytical results: Unit I with clayey sediment, Unit II with silty sediment, and Unit III with sand and gravel. Principal component analysis (PCA) was applied to the 18 major and trace elements, and they were divided into terrigenous (Al, Si, K, Rb, Zr, Cd, and Pb as the first principal component, and Cr, Fe, Zn, and Ti as the second principal component), authigenic (Ca, Mn, and Sr), and melting (S and Br) inputs. PCA provided insight on the correlation between the sediment characteristics and elemental data. PCA variables demonstrated that lithogenic elements transported by the alluvial or aeolian processes are the principal component through the whole core. The PCA score showed a significant difference between Units I and II. In-lake chemical productivity, indicated by elements found in authigenic materials, was most active during the middle Holocene (upper part of Unit II) in the Olgoy Lake sediment.
