Extraordinary hydro-climatic events during 1800-1600 yr BP in the Jin-Shaan Gorges along the middle Yellow River, China.

Paleoflood slackwater deposits (SWDs) of the Holocene were found at many sites along the Jin-Shaan Gorges in the middle Yellow River basin. A set of four paleoflood SWD beds was identified at the Pingduguan (PDG) sites and studied by field observations and laboratory analysis including particle-size distribution and Optically Stimulated Luminescence (OSL) dating. Hydrological reconstruction using the HEC-RAS model shows that the paleoflood peak discharges were between 39,000 and 50,220m³s-1. They are about double the largest gauged flood (24,000m³s-1) that has occurred since 1976 along the Jin-Shaan Gorges. These extraordinary flood events were OSL dated to between 1800 and 1600yr BP during which climatic deterioration and disasters were documented over the Yellow River basin. Various evidences show that severe flood and drought disasters during the episode resulted in frequent harvest failures, famines, social upheavals, and population reduction, invasions by nomads, and even the fall and replacement of the dynasties. Climate decline documented by proxy records such as tree-rings, stalagmites, ice-cores and lake sediments from over the world is in agreement with the paleoflood events identified along the Jin-Shaan Gorges. These mean that the extraordinary paleoflood events are closely related to increased climatic variability and instability. This result provides solid evidence for understanding the response of hydroclimatic system to global climate change in the semi-arid and sub-humid regions of the world. [ABSTRACT FROM AUTHOR]