【摘要】 通过有机碳同位素(δ¹³C_crg),磁化率和粒度的测定和分析,结合光释光年龄标定,对新疆巴里坤湖区滨湖相沉积物14ka B.P.以来δ¹³C_crg值变化的影响因素及其反映的气候特征进行了研究。结果表明:在巴里坤湖区植被类型主要以C₃植被为主,干湿变化是导致δ¹³C_crg值波动的主要因素,在末次冰消期至早全新世阶段（14.0⁸.4ka B.P.）,巴里坤湖区周围冰川尚未融化,剖面δ¹³C_crg值最为偏正,在-22‰到-21‰之间变化,暗示剖面处在干-旱的气候条件下;进入全新世后,随着巴里坤山冰川的融化,湖区湿度增加,同位素值持续偏负,达到23.5‰,同时中值粒径和磁化率同步降低;在中全新世阶段（7.2⁵.0ka B.P.）出现高湖面,同位素值达到-24‰左右,为剖面同位素值最低阶段;中晚全新世阶段（5.0¹.5ka B.P.）δ¹³C_crg值开始逐渐偏正,表明气候开始变干;1.5ka B.P.至今的δ¹³C_crg值则是在-24‰^-23‰间频繁波动,反映了该时段气候的不稳定性。更多还原

【Abstract】 In this study,we reported the records of isotopic compositions of total organic carbon（¹3Corg"）,media grain size and magnetic susceptibility in BLK-1 core（43³7’09.4"N,92⁴2’13.I"E）,taken from the ancient shoreline of Lake Barkol,Xinjiang,Northwest China.About 100 samples with a thickness of 2cm spanning the past14 ka B.P.were analyzed in this paper.The chronology was built on five Optically Stimulated Luminescence（OSL）dates from different depth using the 38⁶3μm quartz particles.The ages of sampled horizons were derived by liner interpolation,which were 0.14±0.02 ka B.P.at 0.lm,0.28±0.02 ka B.P.at 0.2m,4.08±0.26 ka B.P.at0.6m,8.43±0.58 ka B.P.at 1.6m,and 13.9±0.89 ka B.P.at 2m,respectively.The δ¹³C_org.values of BLK-1 section vary from-21.6‰^-24.3‰,its mean value was-23.3‰,indicated that the vegetation in the study area was dominated by C3 plants.According to the analyses of the chronology,theδ¹³C_org,the media grain size and the magnetic susceptibility.The vegetation type in this region could be considered as pure C₃ plants Therefore,the variation of δ¹³C_org.values corresponded to wet/dry climate.The paleoclimate history of the Lake Barkol region during the last 14 ka B.P.was revealed as 5 stages:1)14.0 8.4ka B.P.,the δ¹³C_org,media grain size and magnetic susceptibility values were the highest(-21.5‰,300⁵00μm,and 25× 10^-7m³/kg respectively),suggesting an extremely dry regional climate condition.2)8.4⁷.2ka B.P.,theδ¹³C_orgvalues suddenly decreased about 2‰ compared with stage 1,indicating a short dry to wet transition period as indicated by the significantly decreasing of all proxies.3)7.2⁵.0ka B.P.,theδ¹³C_org.values slightly fluctuated around-24‰,the lake level expanded to the site of core BLK-1,suggesting a stable high lake level during this period,which is in good accordance with those of the adjacent region.4)5.0¹.5ka B.P.,the wet to dry climate transition period,the δ¹³C_orgvalues increased slightly,indicating that the Lake Barkol was gradually shrinking.5)1.5ka B.P.to present,the δ¹³C_org,grain size and magnetic susceptibility values fluctuated frequently,reflecting rapid climate changes in this period.The lake level dropped below the core site at 1.5ka B.P.,as a result of continuously enhanced evaporation.Overall,our research confirms that the variations of δ¹³C_org.values in a lakeshore profile can be used for inferring paleoclimate information.更多还原