[U-05] Advanced understanding of Quaternary and Anthropocene hydroclimate changes in East Asia

[U05-P10] 210-lead Dating Method and Lacustrine Sediment Analyses of Tsagaan Lake, Valley of the Gobi Lakes, Mongolia to Understand the Past Environmental Changes

*Shuukhaaz Ganbat¹、Noriko Hasebe¹、Uyangaa Udaanjargal¹、Davaadorj Davaasuren²、Shinya Ochiai³、Yuma Shibuya¹ (1.Graduate School of Natural Science and Technology, Division of Natural System, Kanazawa University、2.School of Arts and Sciences, National University of Mongolia、3.Low level Radioactivity Laboratory, Institute of Environmental Technology, Kanazawa University)

キーワード：Paleoclimate, Lacustrine sediment, CRS model

One of the major environmental issues for us is climate change. Its effect varies from place to place and should be observed continuously in each region. Mongolia is one of the fastest-warming regions in the world, and climate change is inducing unpleasant environmental issues in the region. Paleoclimate study in this vulnerable region is crucial to understand climate oscillation in the past to predict future climate changes. In this research work, we aim to reconstruct the past environmental changes based on lacustrine sediment analysis and their age dating. Lacustrine sediment of a core /1.3 m depth/ was retrieved from the Tsagaan lake in 2018. Multiproxy analyses including parameters of water content, organic matter, carbonate, amorphous silica, and grain size were conducted. The proxies preserved in sediment sequence over time can reconstruct the changes in regional climatic and hydrological conditions. In addition, ²¹⁰Pb dating method was utilized to detect high-resolution sediment age in recent times /~150 years/. Sediment grain size is negatively correlated with the organic matter, carbonate, silica content in the sediment core. The coarse sand layers were likely to be deposited by the intensified wind activity under dry conditions in the past. Unsupported ²¹⁰Pb concentration was detectable between surface and 20 cm depth, an anomaly pattern of unsupported ²¹⁰Pb concentration was observed in 10-14 cm depth. Therefore, the CRS model can’t prove the potential age range (~150 years) for the analyzed core sample. The model of the ²¹⁰Pb dating result exhibit that 10 cm depth sediments in the upper layer have approximately accumulated in 70 years, the sediment accumulation rate fluctuates between 0.1 – 0.8 g/cm² year. The retrieved total core profile except for the uppermost layer is older than the potential age limit of the ²¹⁰Pb dating method.