Indexed on: 01 Apr '91Published on: 01 Apr '91Published in: Chinese Journal of Geochemistry
The present paper deals with the biomarker characteristics of crude oils and source rocks from different environments (fresh, fresh-brackish and salt waters) of nonmarine depositional basins of different ages in China. Their characters are summarized as follows: 1 ) Source rocks and crude oils derived from fresh-water lacustrine facies have an odd / even predominance of n-alkanes and high pristane / phytane ratios. Oils from the fresh-water lacustrine fecies differ from typical marine oils in the relative contents of total steranes and terpanes, the concentrations of hopanes and organic sulphur compounds and the values of methylphenanthrene indices and C, H, S stable isotopes. 2) The source rocks and crude oils derived from saline lacustrine fecies possess an even / odd predominance of n-alkanes and high phytane / pristane ratios. There are also some differences between saline lacustrine oils and freshwater lacustrine oils in the concentrations of steranes, tricyclic terpanes and organic sulphur compounds, as well as in the values of methylphenanthrene indices and C, H, S stable isotopes. 3) Oils derived from fresh-brackish water lake facies differ from oils from fresh-water lacustrine or saline lacustrine environments in respect of some biomarkers. According to the various distributions of these biomarkers, a number of geochemical parameters can be applied synthetically to differentiating and identifying the nature of original depositional environments of crude oils and source rocks and that of organisms — primary source materials present in those environments.