云南楚雄盆地上三叠统沉积及地球化学的海相特征

楚雄盆地为中生代形成的典型前陆盆地。三叠纪是其形成的主体阶段和盆山转换的重要时期,也是由海相向陆相沉积环境的转折期,同时上三叠统是楚雄盆地最重要的油气资源层系。通过对楚雄盆地上三叠统进行系统的沉积学、层序地层学和波动地质学分析,在上三叠统识别出3个三级层序,建立了层序地层格架和高频波动曲线。对层序地层格架内的碳、氧同位素和微量元素的特征进行分析,发现楚雄盆地晚三叠世诺利晚期—瑞替期沉积具有海相沉积环境的地球化学特征,同时综合多学科的研究成果,指出楚雄盆地该时期为一与海域相接的近海湖盆,并受到间歇性海侵的影响。而海相烃源岩与陆相烃源岩在生烃能力、分布规律等方面均具有较大的差异。因此,这一认识对于重新评价楚雄盆地晚三叠世烃源岩具有重要意义。

The Marine Character of the Sedimentation and Geochemistry of the Upper Triassic in the Chuxiong Basin,Yunnan

The Chuxiong Basin is a typical foreland basin formed in the Mesozoic. The Triassic is the main stage in the formation of the basin, and is an important age of a conversion from basin to mountain, and the transition period of sedimentary environment from marine facies to continental facies. At the same time, the Upper Triassic series is a significant source of oil and gas in the Basin. Based on a systemic study and analysis on the sedimentary, sequence stratigraphy, undulation geology and geochemistry of the Upper Triassic in the basin, three sequences are recognized, and sequence framework and high-frequency undulation curve of the Upper Triassic are reconstructed. The analysis of carbon and oxygen isotopes and trace elements reveals that the Chuxiong Basin had a marine environment during the late Norian to Rhaetian. The multi-disciplinary research results indicated that the Chuxiong Basin was a lake basin adjacent to sea in this period, and was affected by intermittent transgressions repeatedly. But the marine-facies hydrocarbon source rock and the continental-facies hydrocarbon source rock are different in hydrocarbon productivity and distribution. This understanding will have a vital significance in assessing the hydrocarbon source rock of the Chuxiong Basin.