Research on Short-chain Steranes in Source Rocks from Upper Permian, Eastern Xinjiang

Key words: 
• short-chain steranes /
• source rock /
• biodegradation /
• Upper Permian /
• Eastern Xinjiang

Abstract: In order to understand the organic geochemistry feature of the source rocks, GC-MS analyses on saturated hydrocarbons in the Upper Permian Lucaogou & Pingdiquan Formation source rocks from the Junggar and Santanghu Basins in Eastern Xinjiang were performed. Complete short-chain steranes with C_19-21~C₂₆ R were detected in mass chromatograms at m/z217. The detection of these compound series indicates that a flourish of sponges, algae (e.g., red algae and Gloeocapsomorpha prisca) and other lower aquatic organisms existed in saline waters under arid  conditions. These original organic materials experienced severe bacterial biodegradation during the early deposition stage; the original organic matter and the products of microbial degradation were preserved together and became precursors of hydrocarbon generation.