Geochronological (36Cl and OSL) and geomorphic insights into the formation of Terkhiin Tsagaan Lake and Khorgo Volcano in Central Mongolia: Unravelling a pre-Holocene paleolake

Abstract

Multiple lava flows have profoundly shaped the landscape of Terkhiin Tsagaan Lake (TTL) in central Mongolia, influencing its level and extent over the Quaternary. Optically Stimulated Luminescence (OSL) dating of terraces unveils ages ranging from 65 to 59 ka at 2073 m, 54–51 ka at 2069 m, and approximately 46 ka at 2065 m. Additionally, cosmogenic 36Cl dating of a lava flow provides insights into the timing of the most recent volcanic eruption, dating it to 7.2 ka ago. The integration of geomorphic and geochronological evidence, along with observations of Lava-Water-Interaction features, suggests the presence of a paleolake preceding the last Holocene eruption of Khorgo Volcano. The geomorphic evolution unfolds in three stages: (i) A Pleistocene lava flow formed multiple dams across the Tariat Basin, creating temporally successive lava-dammed lakes. (ii) The paleolakes underwent fluctuations, leaving lacustrine terraces, and experiencing lower levels. (iii) Holocene eruption of Khorgo, which is one of the youngest in Central Asia, shaped the current TTL by releasing lavas over the eastern margin of the paleolake. The study contributes valuable insights into the paleoenvironmental dynamics, shedding light on the interplay between volcanic activity, climate, and landscape evolution.