Dating of multiple debris flow stages in the Sandaoqiao gully, Kangding, Eastern Tibetan Plateau: implications for regional tectonic and climate changes

Chronology of debris flow deposits (DFD) is crucially important in understanding fan evolution and assessing the risks of future extreme disaster events. To establish the debris flow history in a long-term temporal framework, multiple debris flow and flash flood events were examined from the Sandaoqiao (SDQ) gully near the large-scale active Xianshuihe faults, eastern Tibetan Plateau. The rough and discontinuous structures indicate DFD are characterized by “linear stone structure” and boulders enclosed by clayey silts in the SDQ gully. On the basis of debris flow sedimentary characteristics, we develop a valid sampling strategy involving ¹⁴C and OSL dating methods (13 radiocarbon and 3 OSL ages) on the debris flow fan. The major stages of debris flow aggradation were identified at ~ 35 kyr B.P., 23‒22 kyr B.P., ~ 13 kyr B.P. and 3.9‒1.4 kyr B.P. since the Last Glacial (last ~ 35 kyr B.P.). And gully-fill deposits were more abundant during the latest Pleistocene (35‒13 ka) than current phase. Late Holocene debris flow and flash flood events recur in the mid-channel from 3.9‒3.8 to 1.9‒1.4 kyr B.P., which was probably triggered by palaeo-earthquake events associated with active faults. The current phase is dominated by debris flood events and the maximum discharge is estimated as ~ 290 m³/s. This study provides key chronology for understanding multiple debris flow stages associated with regional tectonic activity and climatic change in the eastern Tibetan Plateau.