选择位于新疆孔雀河北岸的LX01湖相沉积剖面作为研究对象,根据14个ESR年代结果,建立了塔里木盆地东部中更新世湖泊沉积地层的年代序列。此外,采用ESR测年法得到了剖面的沉积速率,在727~93 ka BP期间,研究区域平均沉积速率介于0.429~3.895 cm·ka~(-1),表现为沉积速率不稳定,发生了较大变化,不但有长期缓慢的变化,还有短期的急剧变化,总体呈现波动特征。具体表现为:727 ~ 278 ka BP期间,波动幅度逐渐增大;278 ~ 93 ka BP期间,沉积速率阶段性降低。在此基础上,通过对比分析罗布泊地区中更新统沉积速率和罗布泊及周边区域中更新世期间的气候变化,发现位于孔雀河北岸LX01剖面沉积物的沉积速率可在一定程度上揭示罗布泊地区中更新世期间的古气候变化特征,表现为:沉积速率速率高的278~200 kaBP、306 ~ 325 ka BP、389 ~ 410 ka BP、530 ~ 568 ka BP、638 ~ 679 ka BP为温暖湿润气候;沉积速率低的93~200 ka BP、278~306 ka BP、325~389 ka BP、410~ 530 ka BP、568~638 ka BP、679~727ka BP为冷干气候。该研究为中更新世地层沉积速率的空间分布特征和古气候变化研究提供科学依据。
英文摘要:
In this paper, a 7.88-m-thick section of lake sediments (89°53' E, 40°41N) was discovered in the northern margin of Kongqi River, which is located at Tarim Town, Yuli County, eastern Xinjiang, northwestern China. From up to bottom,fourteen Electron Spin Resonance (ESR) ages were achieved, dated in 9319 ka BP at0.29 m,20025 ka BP at 0.89 m,248;24 ka BP at 1.46 m,27840 ka BP at 2.28 m,30634 ka BP at 2.40 m,32532 ka BP at 3.14 m,38938 ka BP at 3.48 m,41055 ka BP at 4.03 m,44944 ka BP at 4.61 m,53053 ka BP at 5.12 m,568108 ka BP at 5.90 m,63863 ka BP at 6.55 m,67975 ka BP at 7.12 m,and 72772 ka BP at7.56 m. This data suggests that the section spans Mid-Pleistocene and a reliable chronological framework is established for this region. Meanwhile,sedimentation rate is calculated with ESR method. Results show that sedimentation rate presented long-term slow changes and short-term rapid changes, which fluctuated between 0.429 and3.895 cm · ka~(-1). And sedimentation rate increased gradually in fluctuations during 727278 ka BP, while decreased periodically during 278-93 ka BP. The results underlie for the study of spatial distribution characteristics of sedimentation rate in mid-Pleistocene sedimentary strata and paleoclimate changes in this area. On this foundation,contrastively analysis of the sedimentation rate in mid-Pleistocene sedimentary strata and the Mid-Pleistocene climate of Lop Nor and its surrounding areas exposes that the sedimentation rate of LX01 section in the northern margin of the Kongqi River can reflect the climate change characteristics of Lop Nor during Mid-Pleistocene. Specific performances are: when the sedimentation gets high rate during the period of 278-200 ka BP,306-325 ka BP,389-410 ka BP,530-568 ka BP and 638-679 ka BP,the climate show a humid-warm pattern; when the sedimentation gets low rate during the period of 93-200 ka BP, 278-306 ka BP, 325-389 ka BP,410-530 ka BP,568~638 ka BP and 679-727 ka BP,the climate show a dry-cold pattern.