The Preliminary Result of 10.5M Core from Lake Olgoy, Valley of the Lake in Mongolia

Mongolia is located in center of the Central Asia and it provides an important key archive for the research of climate characteristics inside continents. Lake sediments are an excellent archive to study long-term fluctuations of environmental conditions (Gunten et al. 2009). Lake is the subject to a variety of extrinsic and intrinsic forcing variables that regulate the history of the lake, such as climate, watershed bedrock geology and geomorphogy, tectonic and volcanic activity, vegetation, aquatic biota, and human activities (Gierlowski-Kordesch, 2004). Numerous studies have been conducted in a different part of Mongolia to reconstruct the past climate and environmental changes.

The Olgoy lake is one of the thermokarst lake, located in the southern edge of the Khangai mountains in the valley of the lakes where is characterized by an extreme climate, and environmental issues are very severe for nomadic people living there. The study with 10.5 m long sediment core retrieved from Olgoy lake is expected to assess the regional reconstruction of paleo environment.

The sedimentary features are investigated along the core and include whole and mineral grain size, water content, organic matter, carbonate, amorphous silica contents and variation in elemental concentration scanned by the ITRAX. Sedimentary ages were estimated by OSL (~10.5 ka) measurement. Organic carbon rich layers are found at 1 m and 4 m depths. Carbonate content is high at depths of around 6.5 till 8.5 m and show increasing trend in upper 4m. The whole and mineral grain size is getting fine in upper part. The comparison between sediment characteristics and climate condition using short cores reveals that calcium carbonate concentration, amorphous silica concentration, and whole and mineral grain size correlate to temperature in Olgoy lake (Uyangaa et al., submitted). Based on this understanding, analytical results of the long core are interpreted, and we identify increasing trend of temperature after mid -Holocene.