High Revolution Sedimentary Record Of Environmental Evolution Since 7 Cal Ka BP In Shuangchi Maar Lake,North Hainan Island

This study presents the record of paleoenvironmental evolution results with 210Pb,137Cs and radiocarbon-dated from a approximate 8.04-m-long lacustrine sediment core in Shuangchi maar lake,North Hainan Island.Measurements of grain size,water content,dry density,magnetic susceptibility(MS),total nitrogen(TN),total organic carbon(TOC),atomic TOC/TN(C/N),organic carbon and nitrogen isotope(?13C and ?15N),dry and wet color reflectance values were carried out in order to reconstruct the climatic-environmental evolution during the past 7 cal ka BP.Two distinct depositional environment period can be well identified according to variation of proxies values.7.0?1.4 cal ka BP,Lake basin sedimentary environment is the swamp phase.This period can be divided into two stages:7056?6615 cal a BP:Lake relatively shallow under a relatively mild climate.6615?cal a BP:Hot-dry climate dominated this area.Effective precipitation earlier reduce and latter increase.Swamp environment was transformed into a shallow lake environment since 1.4 cal ka BP.relatively cold-dry climate dominated this area in this period.Precipitation earlier increase and latter reduce.Increasing magenetic susceptibility indicates increased human activity.During the past 1500 years,cold-dry climate in MWP(900?1200 AD)and warm-humid climate in LIA(1300?1750 AD)could be detected according to the variation of proxies,which was consistented with the record in surrounding lakes.The trend of gradual drought is controlled by solar radiation and the ITCZ shift during 7 ka BP to 3 ka BP.Climate change was associated with ENSO during late holocene.Red noise spectrum analysis of some proxies shows the cycle of 6?8 a,18?20 a,88 a,103 a,215 a in past 1500 years,which indicate that high resolution climate changes was influenced by solar activity and ENSO.