Paleoenvironmental Changes during Holocene in the Darhad Basin in Mongolia

The Hodon outcrop is situated in the central Darhad Basin in northern Mongolia. Multiproxy analyses were performed to produce a high-resolution paleoenvironmental change from a 12 m section of the Hodon outcrop. According to the geochronological data of the study area, the sedimentary sequence formation started in the early Holocene and lasted up to approximately 2 cal kyr BP. Late Pleistocene glaciers around the Darhad Basin are closely linked to paleolake development. The Hodon outcrop sediments were mainly deposited by sedimentary-dammed lakes. Based on sedimentological (magnetic susceptibility, grain size, and thin section) and geochemical (major elements, X-ray diffraction, and total organic carbon) analyses, the sedimentary sequence of the Hodon outcrop can be divided into five units, units A-E. The sedimentation record and chronological data indicated two cycles of lake sedimentation (units B and D) divided by a thick sand layer in the middle (unit C). The lake sediments were deposited under deep-shallow water conditions (units B and C), with a dry and subaerial sedimentary environment in the uppermost part (unit E). The thick sandy layer (unit C) might have resulted from the catastrophic discharges of the lake caused by dam failures. Notably, the development and complete disappearance of the lake in the Hodon outcrop might have been caused by environmental changes during the Holocene.

This research was funded by the Korea Environment Industry & Technology Institute (KEITI) through the Measurement and Risk Assessment Program for the Management of Microplastics Program, funded by the Korea Ministry of Environment (MOE), grant number 2020003110010 and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (grant numbers 2019R1I1A2A01057002).