Relationship between middle Permian upwelling facies and hydrocarbon in lower Yangtze area

Acreage of the Lower Yangtze area is 177 020 km² including Jiangsu, Zhejiang, Anhui, Jiangxi provinces and most part of Shanghai, and it's a passive continental margin. Through analysis and correlation of some Paleozoic profiles across this area, it is considered that the upwelling in the Paleotethys caused deposition of danks, siliceous shale, silica rock, siliceous bands and nodules, phosphorite layers and nodules of middle Permian. Since upwelling water is rich in nutrient salt and SiO₂, high bioproductivity and anoxic events appeared in the southeastern margin of the low-latitude Paleozoic lower Yangtze block. The upwelling resulted in the deposition of organic-rich carbonaceous and phosphorite sediments such as source rocks, bone coal and phosphorite, etc. There are rich big fossil organisms in the sedimentary strata of the upwelling current. The biocoenosis belongs to benthonic and anchoring faunas in the shallow sea and siliceous radiolarite boomed. The positive relationship between the TOC content and strength of the upwelling current is evident.