Neogene tectonics, geomorphological processes, and Quaternary climate change control landscape evolution in the internally drained basins of the Basin of Great Lakes (BGL), western Mongolia. The interplay of aeolian, fluvial, and lacustrine processes has resulted in a variety of landforms, such as large dune fields, beach bars, and alluvial fans. Their associated sedimentary archives and sediment transport pathways reflect mid-to-late Quaternary landscape evolution. The ongoing project analyzes geomorphological processes and sedimentary records. Different dating methods constrain the timing of landforms and deposits.(1) Aeolian and fluvial dynamics: Mongolia's three largest dune fields, resulting from a long-term Quaternary sediment cycle, are located in the BGL. Rivers transport sediment into endorheic lakes. During lake-level low stands, winds transport the sand eastwards along the dune fields. The lakes exhibit different paleolake levels, and sandy plains with mobilized sand at their eastern ends exist. Three climatic and paleoclimatic implications are derived from a mapping approach1. (i) The fundamental west-east orientation of the dune fields is a result of the westerly winds that prevailed during the arid periods of the Quaternary. (ii) The highest lake levels occurred during pluvial phases caused by increased moisture supply. (iii) In the modern semi-arid climate, wind systems from north to northwest predominate, while in the southernmost dune field, minor winds from the southeast occur. Preliminary dating results give mid-Pleistocene dates for the core of the dune fields and Holocene dates for the youngest and smaller dunes.(2) Lake level fluctuations: The first comprehensive late Quaternary chronology of lake level variations for the Khyargas Lake in the BGL is presented. The data is based on a geomorphological approach supported by luminescence dating. The lake is the ultimate sink of a sequential water and sediment cascade from the adjacent Mongolian Altai and Khangai Mountains. Several intercalated lakes repeatedly merged to form a large paleolake, as evidenced by various shoreline features. Twelve paleolake levels between +7m and +188m above the modern lake level (a.m.l.) are identified from well-preserved paleoshoreline sequences. Calculations of paleolake extent and water volumes emphasize times of enhanced inflow and gradual capture and subsequent reduced inflow and abandonment of upstream-located lakes. Three distinct phases of lake level dynamics can be differentiated: (i) A transgression to a maximum level of +129m (a.m.l.) during Marine Isotope Stage 5c primarily controlled by enhanced atmospheric moisture supply. (ii) A post-Last Glacial Maximum lake expansion to a level of +118m (a.m.l.) around 14 ka, ultimately controlled by glacial meltwater pulses. This period was followed by a rapid lake level drop during the Late Glacial–Holocene transition in response to decreasing meltwater supply and a drier climate. (iii) Small-scale lake level fluctuations throughout the Late Holocene reflect a hydro-climatically controlled equilibrium between ~ 2.6 and 0.7 ka.The final project phase will obtain TCN dating of paleoshorelines and alluvial fan activity.1 Lehmkuhl, F. et al. Aeolian sediments in western Mongolia: Distribution and (paleo)climatic implications. Geomorphology 465, 109407 (2024).