Environment Evolution Recorded By Eolian Deposit Since The Last Deglaciation In The Qinghai Lake Region

The Tibetan plateau is "the driver and amplifier of global climate change" and "the best natural laboratory of global change and earth system research". The Qinghai Lake region located in the northeast of Tibetan plateau is the correlation region of southeast monsoon, Indian monsoon and westerlies, meanwhile, it is also the correlation region of the west arid zone, east seasonal wind area and Tibetan plateau cold area, which is very sensitive to climate change, so it is an ideal area to study the evolution of Quaternary paleoclimate. For a long time, the Quaternary research about the Tibetan plateau focuses on lake sediments of the Tibetan plateau, however, due to existence of "hard-water effect" or "carbon pool effect", the chronological age of lake sediments obviously gets older, which results in that our understanding about past environmental changes may have some uncertainty. Therefore, using other environmental information carrier to reconstruct the ancient environment and palaeoclimate, and then supplementing and verifying each other with lake sediments is particularly important. So the eolian sediments such as loess, eolian sand and so on widely distributed in the Qinghai-Tibet Plateau become preferred research object of Quaternary researchers.This paper selects three loess-paleosol profiles which include JXG-1, JXG-2, and SNH in the south and the west bank of the Qinghai Lake, on the basis of stratigraphy and chronology(optical stimulated luminescence, thermo luminescence dating and 14C dating), combines with various environmental substitute index such as particle size, magnetic susceptibility, chromaticity, geochemical elements and so on, and analyzes the environment evolution recorded by eolian deposit since the last deglaciation in the Qinghai Lake region. Based on the analysis and discussion of various environmental indicators, we selected the less than 2 microns components, more than 63 microns components, redness, magnetic susceptibility, element as a substitute indicator of environment reconstruction in Qinghai lake area. Three profiles relatively consistently record that the Oinshai Lake area has exoerienced thrice significant climate chanse since the Last Deglaciation, the environment of Qinghai Lake area was dry and cold in general, the profile mainly grew eolian sand and loess during the Last Deglaciation-12 kaBP; The climate in the Qinghai Lake region was warm and moist, the profile mainly grew paleosoil during 12-5 kaBP; The brightness, organic matter and magnetic susceptibility all showed a trend of decreasing first and then increasing, the climate transformed from wet to dry in general, and its variation is great during 5-2 ka BP; The climate developed in the direction of drying during 2 ka BP-Comparing different palaeoenvironment-responsive, we found that three profiles’ redness presents the opposite trendand which compares with lake drilling QH2000 only about 50 km away.The reason of the situation may be during the warm phase the weak wind, high vegetation coverage, low intensity of dust storms, relatively less import of red varieties and low red degree of paleosoil; strong wind during the cold phase, low vegetation coverage, frequent dust storms, relatively more import of red varieties and high red degree of loess.