The genesis, evolution, and geomorphological significance of the Kangkong Paleolake in the PhungQu Basin of southern Tibet

Abstract

The southern Tibetan Plateau has nurtured numerous paleolakes. The formation and evolution of these paleolakes are intricately linked to factors such as tectonic activity, climatic fluctuations, and surface processes. Investigating paleolakes sheds light on the impact of tectonic activity and climate change on paleolakes in the southern Tibetan Plateau, as well as the influence of paleolake formation and outburst on geomorphology. This study conducts sedimentological and chronological analyses of the Kangkong Paleolake in the PhungQu Basin, revealing that the lake formed at least 42.6 ± 3.9 ka, most likely caused by moraines blocking the PhungQu under the combined influence of tectonic movements and climate change. Furthermore, the evolutionary history of the Kangkong Paleolake was reconstructed, indicating that the lake persisted for at least 38 ka and experienced two outburst events, approximately 15.9 ± 1.3 and 3.9 ± 0.5 ka. The combined effects of significant movements along the Kharta normal fault and climate change likely influenced glacier expansion and melting, thereby affecting the stability of the glacial dam and ultimately leading to the formation and outburst of the lake. Spatial comparisons of river longitudinal profiles, dam, and geomorphic parameters have revealed that the formation of the Kangkong Paleolake resulted in a distinct convexity in the river profile at the moraine dam site. The upstream channel continuously widened while the downstream channel deepened. Local areas experienced uplift due to isostatic rebound, creating steep terrain. These findings further demonstrate that damming events have significantly altered the geomorphology of the PhungQu basin while stabilizing the steep topography along the southern margin of the Tibetan Plateau. This study provides direct evidence of damming events in the PhungQu basin and confirms that the PhungQu had already connected with the Arun River before the formation of the paleolake.