第七届青年地学论坛

Palaeoflood records have provided the extended perspective required to understand linkages between extreme floods and climate variability. During our palaeohydrological investigations, two units of palaeoflood slackwater deposits (SWD) were found on the river banks in the Maqu-Oula reach along the mainstream of the Yellow River on the northeast (NE) Tibetan Plateau. A series of samples were taken from the sediment profiles at TWR/DEQ/DEQ-E sites  for laboratory analysis. Grain-size distribution and micro-morphological characteristics of quartz grains indicate that these well-sorted SWD units were derived from the suspended sediment load in floodwater. They have recorded two episodes of overbank flooding in the Yellow River source area. Using the optically stimulated luminescence (OSL) dating technique, the first episode of overbank flooding was dated to 13.6–13.0 ka and correlated with the Bølling–Allerød warm interval of the last deglaciation. The second episode occurred at 11.0–10.0 ka, that is, the early Holocene. In a warm-humid climate, these overbank flooding episodes may have resulted from the accelerated melting of mountain glaciers and snow over the headwaters of the alpine and subalpine regions on the NE Tibetan Plateau. These results are important in facilitating an in-depth understanding of the hydro-climatic response of the Tibetan Plateau to global climate warming occurring presently.