第九届青年地学论坛

The northeastern (NE) Tibetan Plateau is located in the transitional zone between seasonal frozen soil and permafrost. This region exhibits a heightened sensitivity to global changes and serves as a focal point for exploring permafrost development, climate change, and environmental evolution. Through extensive field investigations in the Yellow River source area on the NE Tibetan Plateau, typical paleo-periglacial involution phenomena was identified in the Zoige Basin and the Maqu valley. Based on the newly discovered NYQ-A profile and integrating findings from previous studies, this study conducts a multidisciplinary investigation encompassing geomorphology, sedimentology, and chronology. It provides an in-depth analysis of paleo-periglacial involutions, focusing on morphological characteristics, stratigraphic chronology, and formation reasons in the region. The results show that: (1) Morphological characteristics: the folds correspond to the typical types of periglacial involutions, including the individual undulating type, symmetrical undulating fold type, pocket type, and diapir type; (2) Stratigraphic chronology: two phases of paleo-periglacial involution events were documented, occurring at 27.53±1.26–14.66±0.54 ka and 13.10±0.88–11.06±0.88 ka, temporally corresponding to the Last Glacial Maximum (LGM) and the Younger Dryas (YD) event, respectively. (3) Formation reasons: the formation of periglacial involutions involve the coupling of multiple factors including climate, geomorphology, and lithology. In a cold climatic background, the Yellow River source area, characterized by low-lying, flat, and humid conditions, is predisposed to permafrost development. With a slight temperature increase, the upper part of the seasonal active layer, comprising fine-grained (low permeability) and horizontally stratified lithology, undergoes thawing. Subjected to repeated frost-action processes, deformation is induced, ultimately leading to the formation of periglacial involutions. The study holds paramount significance in enhancing the scholarly understanding of periglacial phenomena on the Tibetan Plateau. It also contributes substantially to elucidating the developmental patterns of paleo-periglacial involutions and their consequential impact on global environmental changes.

Tibetan Plateau,Last Glacial Maximum,Climatic background,Environmental significance,Paleo-periglacial involution