۳۶Cl and OSL Chronologic and Geomorphic constraint on the evolution of Terkhiin Tsagaan Lake, central Mongolia, using interactions with multiple volcanic lava flows

Terkhiin Tsagaan Lake (TTL), located in the Tariat Basin in the northern part of the Khangai Mountains in central Mongolia, is lava dammed lake formed by Khorgo Volcano (KV). The age of formation of KV and TTL using the ۱۴C dating was reported ۸۷۸۰–۷۷۱۰ yr BP. However, all ۱۴C dates were from lake sediments which were deposited after the initial formation of the lake. Therefore, to overcome these limitations, we applied two numerical dating methods, ۳۶Cl cosmogenic surface exposure dating directly to the lava flow and Optically Stimulated Luminescence (OSL) dating to the lacustrine terrace sediment. ۳۶Cl age was derived as ۹-۸ ka, and the formation period of Khorgo lava flow was similar to the existing age value of ۸۷۸۰–۷۷۱۰ BP. However, the OSL age was derived as ۶۵-۳۳ ka, suggesting the possibility that paleo lake already existed before the last eruption of KV. The difference in elevation distribution between the Khorgo Volcanic Area (KVA) and Pleistocene lava flow area, the shifted channel pattern at the multiple Pleistocene lava flow margin, and the existence of lava water interaction features in KVA, strongly support the possibility of the existence of a paleo lake. Geomorphic evolution of this area can be explained in three stages. (i) A lava flow erupted in the Pleistocene and formed a lava dam in the mainstream and tributaries of the Tariat Basin, forming a lava-dammed lake. (ii) The water level of the paleo lake fluctuated, leaving a flight of lacustrine terraces and the lake experienced the decrease. (iii) Khorgo volcano erupted in the Holocene, whose lava flowed over the paleo lake, forming the current TTL.

کلیدواژه ها:

cosmogenic ۳۶Cl ، OSL ، lava dammed lake ، lava water interaction ، paleo lake