PALAEOCLIMATIC FLUCTUATION FASHION OF QARHAN SALT LAKE IN QAIDAM BASIN IN THE PAST 730 000 YEARS
Huang Qi Chen Kezao (Qinghai Institute of Salt Lakes, Chinese Academy of Sciences)
Qarhan salt lake is the largest one on the Qinghai-Xizang (Tibet) Plateau. With its unique geographic position and Quaternary lacustrine sediments of about 3 000 m thick, Qarhan salt lake is of importance in studying the Quaternary climate variation in China. For a sedimentary profile, especially an uninterrupted lacustrine sedimentary section, the content of organic material in the sediments will be influenced by the variation of sedimentary environment. Organic geochemistry study has shown that under wet and warm environment, the larger the area and the depth of the lake, the more easily the organic material is enriched and preserved, and the higher the content of organic material is. Based on the organic carbon data obtained from Core CK-6 of Qarhan salt lake, the authors recognized that the content of organic carbon in the sediments changes alternatively in relatively higher and lower way, with very clear cycles. Thus, several stratomeres of organic carbon can be divided in accordance with the cyclic change of organic carbon content in the sediments. In Core CK-6, for example, the organic carbon content of odd number stratomeres varies from 0.34％ to 1.44％, with average 0.87％; while in even number stratomeres the content is 0.14％—0.34％, with average 0.25％, 3.4 times lower than the former one. It shows that the cyclic change of organic carbon content in time sequence may reflect the variation of sedimentary environment, including the change of palaeoclimate. we can take the change of organic carbon in different stratomeres as a reference for studying the variation of palaeoclimate. The palaeoclimatic fluctuation fashion reflected by the organic carbon content in Core CK-6 is comparable with the climate variation curve obtained through the study of Luochuan Loess and the deep sea sediment, and the changes in different stages are generally synchronous. In the past 730 000 years, the global climate event has also been reflected clearly within the Qinghai-Xizang (Tibet) Plateau.