Quaternary Geomorphic Characteristics of the Dangxiong- Yangbajing Fault-Depression Basin,Tibet

Gulu-Dangxiong-Yangbajing Fault-Depression Zone in Central Tibet as the core structural unit of the northern segment of the Yadong-Gulu Rift, completely records the sedimentary sequence and geomorphic evolution since the Pliocene. Geological surveys indicate that its typical sedimentary assemblage, including lacustrine mudstone, alluvial-proluvial gravel layers, and travertine deposits, provides an important carrier for studying late Cenozoic environmental changes in central Tibet. Pliocene lacustrine deposits, mainly distributed in the southern margin of Jidaguo, consist predominantly of gray-black mudstone containing ostracods, sporopollen, and other microfossils, indicating a stable lake basin environment. Middle Pleistocene glacial-outwash deposits developed extensively on the southern foot of the Nyainqentanglha Mountains, with moderately sorted and rounded gravels, reflecting glacial modification of the sedimentary system. Late Pleistocene fluvial incision formed multi-level terraces and alluvial fans, revealing episodic tectonic uplift. The Yangbajing hot spring travertine terraces exhibit zonal distribution, with isotopic dating indicating formation during the Middle-Late Pleistocene. Peat sequences in swamp deposits preserve Holocene climate fluctuation records, showing comparability with Tibetan Plateau ice core records. Studies on tectonic-climatic coupling mechanisms reveal that: stable Pliocene lacustrine deposits correspond to a tectonically quiescent period; Middle Pleistocene glacial sedimentary events were synchronous with global glaciations; and Late Pleistocene terrace sequences reflect dynamic processes where tectonic uplift rates exceeded erosion base level decline rates. As a “tectonic-climatic sensitive zone” in central Tibet, the sedimentary response of this fault-depression zone provides critical constraints for revealing the remote response to plate collision and climate synergistic effects.