Abstract:

Evaluating conditions of source rock development by geobiological approaches is an important supplement for the traditional evaluation method of source rocks based on analyses of remnant organic matter. This method is especially suitable for source rock evaluation in areas with highlymatured marine carbonate rocks. Our study is based on observation of outcrops and focused on a systematic analysis of the depositional environment, fossil organism, trace element data and total organic carbon in the Lower Cambrian of the Yangba area in Nanjiang County, Sichuan Basin. The forming conditions for the Lower Cambrian source rocks are recognized through a study on the habitat types, oceanic paleoproductivity, paleooxygenation facies and burial efficiency by using geobiolgical principles. The results show that the lower part of the Qiongzhusi Formation has the most favorable conditions for development of highquality hydrocarbon source rocks as it has higher original organic content, anaerobic sedimentary environment and higher burial efficiency of organic carbon. In contrast, the lower part of the Shilongdong Formation possesses basic geobiological conditions for development of ordinary source rocks.

Key words: geobiology, paleoproductivity, paleooxygenation facies, marine source rock, Yangba area of Nanjiang County, Sichuan Basin