Impact of faulting on the depression morphology of Ulaagchinii Khar Lake in Mongolia

The geomorphology of the Ulaagchinii Khar Lake depression is predominantly governed by tectonic faulting. Morphometric analysis identifies a distinct network of orthogonal faults that are prominently manifested in both topographic and bathymetric patterns. These fault systems primarily trend northwest-southeast and north-south, intersecting near the lake’s central region. This central zone is characterized by pronounced linear formations and abrupt shifts in elevation, as depicted in isobath profiles, indicative of tectonic subsidence along fault zones. The lake depression exhibits strong tectonic control, supported by a high hypsometric integral (HI=0.91) and a notably elongated basin shape index (Bs=2.81). Further evidence for a tectonic origin includes a major east-west oriented fault extending 40.8 km with a steep inclination of 35°, and a vertical relief energy of 274 m. Significant depth variations, reaching up to 47 m in the lake’s western sector, further reinforce the influence of faulting on its morphological configuration. Complementary geomagnetic anomaly data also correspond with these structural features, affirming the presence of active tectonic processes within the depression. The orthogonal fault systems have not only shaped the physical structure of the depression but have also influenced its hydrological regime by enhancing groundwater infiltration, thereby contributing to the lake’s freshwater characteristics. This research underscores that the current morphology and hydrological compartmentalization of Ulaagchinii Khar Lake are the result of an interplay between tectonically controlled fault activity and Late Quaternary dune deposition.