ORGANIC GEOCHEMISTRY MARKERS OF CLIMATIC EVOLUTION IN LOESS REGION OF CHINA
Jia Rongfen Zhao Lin Liu Youmei Wen Qinzhong (Guangzhou Institute of Geochemistry, Academia Sinica, Guangzhou 510640)
The samples collected from Weinan loess section (L2-So) have been analysed by TOC(total organic carbon) and Rock-Eval.The curve of TOC with depth has been set up and compared well with other climatic markers. The main periods of TOC variation of the last 0. 14 Ma are 67. 08 Ka and 18. 29 Ka, which is near with the period of the variation of sunshine, showing that the TOC vari-ation may be controlled by the variation of 65°N sunshineThe distribution of pyrolysis hydrocarbon and its parameters have been researched in detail in the section. It shows that there are two kinds of hydrocarbon associated with cli-matic change. One is called biological reduce hydrocarbon (pHC2-1) which is in the range of Tmax 350℃ ~500℃, and associated with atmospheric water. The other is called car-bonate inclusion hydrocarbon (pHC2-2) which is in the range of Tmax 500~600℃ and formed by evaporation and associated with dry climate.The formula calculating humidity has been deduced: Qg = pHC2-1/(pHC2-1 + pHC2-2). The range of humidity of the section is 47%~77% and the reducing order is S1-3S1-2OS1-1L1-4L1-1L1-3L1-5. And the trend of the humidity is still in-creasing today.