Climate Changes Recorded By The Sediments In Northeast Qaidam Basin Since Miocene

It is record that a series of extensive geographical events occurred on the earth since Cenozoic, resulted in the corresponding climatic and environmental dramatic variations. Recently, many attentions have focused on the study of influences of environment and climate change on the global ecosystem in geographic science. Aridification is one of the most serious problems, substantially threatens the human livelihood, its occurrence, evolution processes greatly attracted the scientist’s attentions. However, the key issue is to obtain the large scale climate variation records for the research of aridification in Asia continent.As one of the giant basin in north of Qinghai-Tibet Plateau, Qaidam Basin has developed continuous, intact and thick Cenozoic layers. This study selected the continuous and have precise stratigraphic control sediments, found in the northeast Qaidam Basin, as the study objects, Quantitative analysis was performed to the sediment samples, and measured the samples’color, Cl-, SO42-, hematite and goethite concentrations, to achieve the high-resolution, multi-indicator and continuous records, combining samples’lithology and sedimentary facies, discussed the characteristics environmental evolution in Miocene and the relationships among the Asian aridification, Qinghai-Tibet Plateau’s uplift, as well as the global temperature reduction. Finally, concluded the following points.1) Through the correlation analysis, results show that in Naoge profile, the red degree values were positively correlated with the hematite concentrations, and reflected that the hematite concentration is the main factor affecting the red degree of this profile. In addition, the variation trend of red degree corresponding to the global temperature change trend. Account for that, it is sensitive to temperature change.2) This study constructed the long term variation sequence (18.4-6.9Ma) of Naoge profile’s indicators of color, hematite, goethite, Cl-, SO42-, and divided the whole profile into three stages in time sequence, the boundary values are14.2Ma and8.1Ma.3) Through the comprehensive analysis of various climate-indicators, combining samples’ lithology and sedimentary facies that the Miocene climate change of northeast Qaidam Basin was that warm and wet period at18.4-14.2Ma, relative cold and wet period at14.2-8.IMa, cold and dry period at8.1-6.9Ma. There exists three drought events at11.4Ma,10Ma and8.1Ma at Naoge region.4) All kinds of index analysis shows that, mainly climate transformation of Qaidam basin happened in14.2Ma and8.1Ma, through the comparative analysis of the results of previous studies that14.2Ma climate transition event by global climate change, while8.1Ma climate transformation may be due to the uplift of Qinghai-Tibet Plateau during this period.