Identification of Fatty Acid Biomarkers in Quaternary of Qaidam Basin and Their Geological Significance

Key words: 
• Qaidam basin /
• biogenic gas source rock /
• unsaturated fatty acid /
• xenobioticbranched fatty

Abstract: To study the biomarker parameters that indicate bacteria activities, fatty acids of three Quaternary mudstone samples from the north of the Sebei area of the Qaidam basin were analyzed by GCMS. A series of unsaturated and abundant xenobioticbranched fatty acids,and isoprenoid acid were identified and discussed in detail. Based on the constitutes of the unsaturated and the xenobiotic branched fatty acids of the two samples, and the geological background of the samples, we think that the unsaturated fatty acids, especially the xenobioticbranched fatty acids and isoprenoid acid were most probably derived from bacteria. The occurrence of these fatty acids in the main biogenic gas production layers indicates that there exist favourable conditions for bacteria upgrowth. The unsaturated and abundant xenobioticbranched fatty acids and isoprenoid acid could be used as indictors that estimate the growth of bacteria in biogenic gas source rocks.