Late Pleistocene lake overspill and drainage reversal in the source area of the Yellow River in the Tibetan Plateau

The source area of the Yellow River (SAYR) in the northeastern Tibetan Plateau (TP) has a series of lakes with an outflowing stream that crosses an active left-lateral strike-slip fault. How and when these lakes began to flow into the Yellow River remains an open question. Here, using geologic maps and a digital elevation model (DEM), we map the drainage network and relate it to tectonically active structural features to explore the role of tectonic processes in drainage integration. We also date paleo-shorelines and other geomorphological features around the modern Gyaring Lake and Ngoring Lake using optically stimulated luminescence (OSL) to illuminate the climate-driven processes leading to lake overspill. Our results show that: (1) drainage reversal in Duoshi Gorge was driven by subsidence in a pull-apart basin, likely during Marine Isotope Stage (MIS) 3; (2) Gyaring Lake and Ngoring Lake experienced two simultaneous overspill highstand periods: one during the last deglaciation (∼14-12 ka) and a second during the early Holocene (∼9 ka), similar to records from closed-basin lakes in the northeastern TP; (3) alluvial fan aggradation was likely enhanced during cold-to-warm transitions, including MIS 5b-a, MIS 4-3, and the last deglaciation; (4) aeolian sediments blanketing the landscape accumulated since the middle Holocene (∼6 ka), consistent with the interpretation of improved trapping efficiency due to increasing moisture availability and denser vegetation. Based on the geomorphic features and dating results, we propose a lake overspill model to explain the land surface processes, reconciling our new observations with previous data on the SAYR. Together, our results indicate a complex history of drainage integration, initiated by a tectonic-driven capture event likely during MIS 3 and punctuated by episodic climate-driven lake overspill and river incision. The lake overspill model may be widely applicable across the Tibetan Plateau, and potentially to Mars in the high plateau of its southern hemisphere. © 2022 Elsevier B.V.