以青藏高原腹地可可西里地区湖泊沉积钻孔BDQ06(35°13'05"N, 93°55'52"E;孔深106 m)为研究对象,基于古地磁测年建立的年代框架,通过对BDQ06孔沉积物粒度、总有机碳、有机碳同位素(delta~(13)Corg)及C/N值等气候环境代用指标的分析,重建了可可西里地区中更新世以来的古气候古环境演化序列。根据各环境指标的变化特征将中更新世以来古气候演化划分为5个阶段:929~660 ka B.P.,气候以暖湿冷干交替变化为主;660~480 ka B.P.,与前一阶段相比气候暖湿程度降低;480~ 360 ka B.P.,气候较为干旱;360~160ka B.P.,气候不稳定、波动幅度增大;160-5ka B.P.,气候再次转为暖湿冷干的变化特征。929~610 ka B.P.期间气候出现4次明显的冷干时期,时间上与MIS 22、MIS 20、MIS 18和MIS 16阶段相对应,此后气候表现出明显的趋冷、趋干特征,可能主要受全球变冷的中更新世革命(MPT)的影响;360kaB.P.开始出现频率增强的暖湿气候波动,说明气候不稳定,显示出明显的区域性特征;160ka B.P.左右出现的较为干冷的时段,与倒数第二次冰期气候相一致,之后环境温度呈现出快速上升的趋势,气候演化进入末次间冰期-末次冰期模式,表现出全球气候一致的特征。整体上,BDQ06孔记录的气候环境演变特征与全球气候变化在冷暖事件上保持一致,但在持续时间、变化强度上存在一定区域性差异。
英文摘要:
To understanding the Pleistocene climate changes in the Hoh Xil(HX) of the Tibetan Plateau, we retrieved a 106-m-long sediment core (BDQ06 : 35°13'05"N, 93°55'52"E) from a paleo-lake, which is located about 30 km apart from the Qingzang Road in the Qinghai Provence. We established the chronology frame of the core by paleomagnetic dating and by comparison paleoclimate index,namely total organic matter (TOC) and the clay particle percentage(<4 mum/%),with the LR04 benthic oxygen isotope stack curves. We reconstructed the regional paleoenvironmental changes based on multi-proxy indices records, including grain size, TOC, carbon isotope composition of bulk organic matter(delta~(13)Corg) and C/N ratios of the lacustrine sediments. Our results indicate that the basal age of the core is about 929 ka B.P., and the paleoclimate changes in the HX can be divided into five stages: (1)929 ~660 ka B.P.,characterized by alternations of warm-humid and colddry phases; (2)660 ~480 ka B.P., the warm-humid degree was weakened compared to stage 1; (3)480 ~360 ka B.P., the climate was drier than before ; (4)360 ~160 ka B.P., the climate was instability with higher amplitude; (5) 160~5 ka B.P., the climate was alternatively dominated by warm-humid and cold-dry again. In general, the fluctuating amplitudes of the climate are relatively higher in the HX, and there are three periods of abrupt climate transition occurred since 929 ka B.P. Among these periods, four obvious dry and cold climate events were observed from 929 ka B.P. to 610 ka B.P., corresponding to marine isotope stage (MIS) 22, 20,18 and 16,respectively. After that, the climate became colder and drier, which may be mainly related to the global cooling during the period of Mid Pleistocene Transition(MPT)". From 360~ 160 ka B.P., the frequency of warm-humid climate fluctuation increases gradually, indicating that climate is instability and has a greater regional character. Then, the relatively dry-cold climate pattern become to appear around 160 ka B.P., coinciding with the climate scenarios during the penultimate ice age. At the end of this stage, the environmental temperature shows a rapid increasing trend. The climate evolution enters into the last glacial-interglacial period pattern, which is coincides with the fluctuations of the global climate changes. In conclusion, characteristics of climatic evolution recorded by core BDQ06 keep pace with global cold and humid climate events, but there are a certain regional differences existed in duration and intensity of climate variation in the HX area.