EXTRACTION OF SENSITIVE GRAIN-SIZE COMPONENT FROM THE KE PEAT DEPOSIT OF THE GONGHE BASIN AND ITS IMPLICATION FOR HOLOCENE CLIMATIC AND ENVIRONMENTAL CHANGE

Grain size versus standard deviation was applied to extract sensitive grain size from the grain size distribution data of the Holocene KE peat deposit of the Gonghe Basin, northeastern Qinghai-Tibetan Plateau. We found that the sensitive grain size component of 63~252 μm(63~112 μm and112~252 μm) can reflect the intensity variation of the regional winter monsoon, upon which we reconstructed the history of the regional winter monsoonal evolution. Our results suggest that the intensity of winter monsoon declined in the period of 10.0~8.5 cal.kaBP, and obviously increased in 8.5~7.1 cal.kaBP. The weakest winter monsoon emerged in 7.1~3.8 cal.kaBP, and it became stronger in the period between 3.8 cal.kaBP and 0.5 cal.kaBP. Afterwards, the winter monsoon rapidly weakened. Comparative study demonstrates that the evolution of regional winter monsoon is correlated well with the climatic change records of the Qinghai-Tibetan Plateau and the marginal monsoonal zone and monsoonal zone in eastern China from different research sources. We also found seven phases of the stronger winter monsoon, which are apparently coincident with the cold events found in the polar ice core and North Atlantic Ocean, probably indicating the inherent relationship of the dynamic mechanism between the regional and the global climatic changes.