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Source rocks are the material basis of oil and gas generation and determine the potential resources of exploration blocks and have important research value.This paper studies the lithology,thickness,and geochemistry of Mesozoic source rocks in the southeaste East China Sea continental shelf.The results show that the Mesozoic source rocks are mainly dark mudstone and coal-bearing strata.The total thickness of Lower-Middle Jurassic source rocks ranges from 100 m to 700 m,and that of Lower Cretaceous source rocks ranges from 50 m to 350 m.The overall thickness of Mesozoic source rocks is distributed in the NE direction and their thickness center is located in the Jilong Depression.The Lower-Middle Jurassic source rocks are mainly developed shallow marine dark mudstone and transitional coal measure strata.Those of the Lower Cretaceous are mainly mudstone of a fan delta front.Lower-Middle Jurassic and Lower Cretaceous hydrocarbon source rocks are dominated by type Ⅲ kerogen,with Lower-Middle Jurassic hydrocarbon source rocks having high organic matter abundance and being medium-good hydrocarbon source rocks,while Lower Cretaceous hydrocarbon source rocks have relatively poor quality.From northwest to southeast,the vitrinite reflectance Ro of Mesozoic source rocks increases gradually.Source rocks in the study area are divided into three types.The first hydrocarbon-generating area is mainly located in the southeaste region of the study area,and the Jilong Depression is the hydrocarbongenerating center.The results of this study can provide a basis for exploration of Mesozoic oil and gas resources in the southeaste East China Sea continental shelf.