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 μm/%), 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(δ¹³C_org.) 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 cold-dry 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.