A RESEARCH ON PALEOENVIRONMENTAL CHANGES DURING THE HOLOCENE IN THE HODON OUTCROP, CENTRAL DARHAD BASIN, MONGOLIA

A multi-proxy analysis was performed to investigate the paleoenvironmental changes in the Hodon outcrop located in the center of the Darhad Basin in northern Mongolia, Central Asia. According to geochronological data, sedimentary layers were deposited from about 10 cal kyr BP (Early Holocene) to about 2 cal kyr BP. The Darhad Basin has one outlet, and is characterized by the formation of a large lake due to that outlet being closed by an ice dam or a sediment dam. Late Pleistocene glaciers around the Darhad Basin had a major impact on the development of paleo lakes, and Hodon outcrop sediments were mainly deposited by sediment dam lakes. Based on sedimentological (magnetic susceptibility, grain size, and thin section) analysis and geochemical analysis (major elements, X-ray diffraction, and total organic carbon), the sedimentary layers of the Hodon outcrop were divided into 5 units (Units A–E). Unit A (1002-1237 cm) represents a fluvial environment, Unit B (548-1002 cm) represents a lake environment, and Unit C (319-548 cm) denotes an environment where a sediment dam, which blocked the outflow, suddenly collapsed, resulting in a decrease in lake water level and the deposition of sediments from the edges of the lake into the study area. Unit D (60-319 cm) represents a relatively smaller lake environment compared to Unit B, while Unit E (0-60 cm) represents a rich environment where sedimentary conditions have undergone a transformation. The development and disappearance of lakes at Hodon outcrop could have been influenced by environmental changes during the Holocene.

This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (grant numbers 2019R1I1A2A01057002 and 2019R1A6A1A03033167) and the Korea Ministry of Environment as "The SS(Surface Soil conservation and management) projects; 2019002820004”.