Diagenesis and diagenetic environments of the carbonate rocks from the Middle Jurassic Buqu Formation in the eastern Qiangtang Basin on the Qinghai-Xizang Plateau

The diagenesis types of the carbonate rocks from the Middle Jurassic Buqu Formation in the eastern Qiangtang Basin on the Qinghai-Xizang Plateau consist of micritization,cementation,compaction-pressure solution,fragmentation and dissolution,of which fragmentation,dissolution and micritization are more common than the others.Judged from diagenetic fabrics,the diagenetic environments comprise the sea water,meteoric and burial environments.The lower part of the depositional cycle II in the Buqu Formation is characterized by intragranular solution openings and submarine micritization,while the compaction-pressure solution in the burial diagenesis predominate in the middle and upper parts.The late meteoric dissolution occurs in response to the rapid falling of sea level following the maximum sea-level rise.The results of research in this paper show that the eastern Qiangtang Basin should be selected as the key prospective area for oil exploration.