论羌塘含油气盆地关键地层划分对比问题OA北大核心CSTPCD

Due to lower exploration degree,the stratal pattern and correlation is still controversial in the oil-bearing Qiangtang Basin,one of the largest sedimentary archives with thick organic carbon-rich strata in the Tibetan Plateau,which impacting the basin evaluation of petroleum conditions and oil-bearing systems.Based on investigations of biostratigraphy,chronostratigraphy,sequence stratigraphy and basin evolution of the Qiangtang Basin,we conduct a comprehensive data compilation to analyze the depositional history and ages of the basin rock record.The results reveal that:(1)New isotopic chronology data confirm that there is a Precambrian metamorphic crystalline basement in the Qiangtang Basin.The Paleozoic basement fold system is buried at a depth of 7-15 km,which is overlaid unconformably by the Mesozoic deposits.(2)The proposed age of the Nadikangri Formation is the Upper Triassic,contradicting previous suggestion of Lower-Middle Jurassic.(3)The dolomites of the paleo-reservoir in the southern Qiangtang Basin belong to the Late Triassic rather than the Middle Jurassic in age,and the dolomites are probably"allochthonous root-less"and tectonic contact with the Buqu Formation.(4)The Bilong Co oil shales in the southern Qiangtang Basin belong to the Lower Jurassic rather than the Middle Jurassic.(5)The Quemo Co Formation has an age not younger than the Middle to Lower Jurassic rather than the original suggestion of the Middle Jurassic.(6)Facies changes and paleontological analysis combined with isotopic data indicate that the Shenglihe-Changsheshan oil shale was deposited in a marine environment during the Early Cretaceous.(7)Isotopic chronology and field geological survey confirm that the Kangtuo and Suonahu Formations comprise simultaneous strata with different sedimentary facies.The data synthesis and progress in stratigraphic research of the Qiangtang Basin provide a new basis for the development of the stratigraphic division and correlation scheme of the basin,as well as the analysis of its petroleum system and potential.