Palynological Evidence of Late Pleistocene Soft-sediment Deformation Event in the Northeastern Margin of the Tibetan Plateau

The northeastern margin of the Tibetan Plateau is the youngest part of the Tibetan Plateau where tectonic activity is intense and climate change is complex. In this study, combined with field investigations, we explored accelerator mass spectrometry C-14 and optically stimulated luminescence dating and palynological analysis of the sedimentary sequence in the Qingshuihe Basin to explain the origin of soft-sediment deformation layer. Dating and palynological results from the Sanchahe section in the basin revealed a detailed history of vegetation variation and associated climate change from & SIM;18 to & SIM;5 ka BP. The results indicate that the permafrost developed at & SIM;18-11.7 ka BP, and the soft-sediment deformation structures formed at & SIM;11.7-5 ka BP. Together with the characteristics of the deformation (meter-scale, continuous symmetrical wave) and paleoclimate, we suggest that the soft-sediment deformation layer in the late Pleistocene was cryoturbated under climatic conditions. The discovery of a series of cryoturbations in the Qingshuihe Basin has further enriched the regional distribution of periglacial phenomena in the west of the Ordos Plateau, expanded the distribution range of periglacial phenomena, and provided evidence for exploring the temporal and spatial changes in permafrost in northern China at the end of the late Pleistocene.