Surface Process and Environment Change Since Last Deglaciation in Western Margin of Zoige Basin, Eastern Tibetan Plateau, China

The Zoige Basin, located in the eastern region of the Tibetan Plateau of China, is characterized by its climate sensitivity and complex surface environment. It is vital to understand the response of the surface processes to environmental changes in the Zoige Basin since the last deglaciation, as well as the response of environmental changes and surface processes on the Tibetan Plateau relate to global changes. In August 2020, a field investigation was conducted in the Zoige Basin. A complete set of stratigraphic profile from the high platform at the front of the glacial-diluvial fan in the Maqu reach of the western basin was selected as the research subject. Optically stimulated luminescence (OSL) dating samples and sedimentary samples were collected from key layers and brought back to the laboratory for experimental analysis, and the surface processes and environment changes since the last deglaciation in the Zoige Basin were investigated through particle size analysis and OSL dating. The results showed that during the last glacial period before 14.5 kyr, a substantial glacial-alluvial fan composed of sand and gravel layers was formed by flash flood processes triggered by glacial meltwater and heavy precipitation. In the Bølling-Allerød warm period of 14.5–11.7 kyr, a warm and humid climate prevailed, with the formation of silty bog environments in the shallow depressions at the glacial-alluvial fan’s forefront and the development of gray-green bog soil deposits. However, during the Younger Dryas period, an abrupt climate deterioration occurred, with the upper section of the gray-green bog soil layer in the shallow depression to experience folding and deformation due to surface freeze-thaw actions. During the early Holocene period from 11.7 kyr to 8.5 kyr, the climate was relatively dry, resulting in prevalent aeolian sand activitities. Coarse silt accumulated in the shallow depression, and sedimentary facies alternating between aeolian sand and bog soil deposits developed owing to strong wind patterns on the plateau surface. In the warm and humid period from 8.5 kyr to 3.1 kyr, increased weathering and pedogenesis enhanced clay content in sediments, which developed into the paleosol. In the late Holocene, starting from 3.1 kyr, the climate became relatively dry once more, with aeolian sand activity prevalent. The coarse silt that accumulated during the late Holocene transformed into subalpine meadow black soil because of rising temperature and humidity levels. These findings indicated that the developmental process of the high platform in the Maqu reach of the Zoige Basin, which was significant for understanding the environmental changes and surface processes in the source region of the Yellow River since the last deglaciation.