Palaeoclimate Reconstruction Of The MIS2 And The Holocene Based On A Lake Sediment Core From The Linhe Depression

Variation in the vegetation and environment at the margin area of the Asian monsoon is sensitive to the globle climatic change.The paper presents data from a continuous lacustrine core record reaching back to 29,200 years B.P.obtained from the Hetao basin near the marginal area of the Asian monsoon.Accelerator Mass Spectrometry(AMS)radiocarbon and Optically Stimulated Luminescence(OSL)dating methods were applied to establish the age-depth model.The past climatic and environmental changes were reconstructed depanding on the lake sediments research through variety of proxies,such as grain size,magnetic susceptibility and pollen.The vegetation and climatic variation can be divided into 4 parts in the section.From the bottom of section to 18.3cal.kaB.P.the lake basin was dominated by temperate desert steppe vegetation,which suggests a cold and dry climate.The pollen analysis of the core sediments shows that there is lack of pollen grains in sand layer during the Last Glacial Maximum(LGM)period(20.7?19.2cal.kaB.P.).Between 18.3 and 14.6cal.kaB.P.the temperate steppe expanded which mainly consited of Artemisia,Chenopodiaceae and Gramineae et al.The mild warm-dry climate with a little more precipitaton possibly responded to the B(?)lling/Aller(?)d during 14.6?14.0cal.kaB.P.During the Lateglacial to early Holocene interval between 14.0 and 9.5cal.kaB.P.the climate was cool and a little dry.Then the landscape was temperature desert steppe.The absence of multi-proxy evidence for a strong climate reversal during the Younger Dryas from T2 core sediments contrasts with some paleorecords showing cooler temperatures and/or dry conditions at the time of 12.4cal.kaB.P.The rainfall and temperature increased apparently during the period of9.5?4.0cal.kaB.P.It suggested a relative warm and humid condition.The vegetation was dominated by temperature forest-steppe.At this stage of 9.5?6.3cal.kaB.P.the level of“Holocene Optimum period” maybe reached in early Holocene.Since the time of 4.0 cal.kaB.P the climate became dryer then before.The paleoclimate records over the past 29,200 years from T2 core were compared to the climatic records from the East Asia monsoon area,the arid area around the North-west China,and the other margin of Asia monsoon area.Most research showed climate variability in the margin area of the Asia monsoon is mainly in fluenced by the Asia monsoon.At the other hand the solar activity has contributed to the regional cold and warm events.The insolation has significant influences on the climate in the northern hemispheres at scale in 10 thousand.