A set of"black rock series"mainly composed of siliceous rocks,siliceous shales and carbona-ceous shales was deposited in the Lower Yangtze region of the Late Permian,which is widely distribu-ted and is considered to have a good prospect of hydrocarbon exploration and development.Based on measured profiles and organic geochemical data,this paper explores the sedimentary environment and hydrocarbon potential of Dalong Formation in central and southern Anhui Province.The results show that the thickness of the Dalong Formation can reach 40-70 m at the periphery of the Chaonan,An-qing-Tongling,Jingxian and Ningguo sedimentary depressions,and it gradually decreases to the north and south.The Dalong Formation is a relatively complete transgressive-regressive sedimentary se-quence,which formed deep basin facies in the early period,and then transformed into submersible shelf facies in the late period.The region is successively composed of deep basin facies,shallow shelf facies and open carbonate platform facies sedimentary assemblages from northwest to southeast.The mass fraction of total organic carbon(TOC)of Dalong Formation is 1.46％-15.80％,and the Rovalue is higher than 2.00％,which belongs to high-quality source rocks,and the thermal evolution is in the early stage of over-maturity.The marginal area of sedimentary depression is the key investigation ob-ject for shale gas exploration.
Lower Yangtze regionLate PermianDalong Formationsedimentary environmentshale gas
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