Drainage geomorphic evolution in response to paleoclimatic changes since 12.8 ka in the eastern Kunlun Mountains, NE Qinghai-Tibetan Plateau

Investigation of the geomorphologic evolution of drainage basins can provide insight into the response of mountain-basin systems to paleoclimate fluctuations. This study investigates the evolution of geomorphic units and their connectivity, from upstream piedmont to downstream salt lake, since the late Quaternary in the Golmud River catchment of the eastern Kunlun Mountains (KLM). The study aims to elucidate the debate over linkages between: (1) landform evolution and paleoclimatic change and (2) dynamic geomorphic processes and lake evolution in the lower basin. Based on geomorphic and sedimentological observations and an optically stimulated luminescence (OSL) chronology, we show three main phases of geomorphic processes: (1) upstream piedmont alluvial fans and an alluvial delta fan at the salt lake margin have surface sediment OSL ages of 12.8-11.4 ka, suggesting a valley aggradation stage in which mass periglacial detritus were eroded and redeposited in the drainage basin; (2) incision terraces in alluvial valley fills provide ages between 11.4 and 8.8, 8.1-6.2, and 4.9-3.9 ka. Incision is ascribed to the reduction in supply of detritus owing to glacial recession and enhanced precipitation in the early to middle Holocene; and (3) widely distributed swamp sediments in the distal delta fan date to 3.2-1.8 ka, suggesting a wetter stage within the late Holocene climatic deterioration. Loess, indicative of aridity, was deposited intermittently during the middle to late Holocene. We reconstructed a wetness index, based on wetness scores of drainage geomorphic units, which is consistent with published moisture proxies. This association implies that (1) landform processes in KLM responded well to precipitation fluctuations in Indian summer monsoon (ISM) dominant regions, indicating their climatic forcing and (2) precipitation variations in the eastern KLM have been mainly controlled by ISM intensity since 12.8 ka. Linking the geomorphologic evolution of mountain-basin systems to downstream arid basin evolution shows that the periods of fluvial terrace incision (early to middle Holocene) were probably important sources of lake salt mineral enrichment. The landscape evolution patterns of mountain-basin systems in the eastern KLM offer a model for assessing the linkages between geomorphic processes, paleoclimatic changes, and lake evolution in other arid regions.