Gas phase, liquid phase and solid phase material composition and physicochemical parameters of oceanic surface sediments reflect the distribution of deep oil and gas accumulations and thus can serve as indices for oil and gas geochemical prospecting. This paper deals with liquid hydrocarbon in interstitial water of surface sediments in the East Sea, diasenetic environmental index Fe³⁺/Fe²⁺, heat-release carbonates (△C) and fractionation of fine-grained sediment samples. Major parameters and referential indexes of surface geochemical pros-pectins for oil and sas in the East Sea have been chosen. Mineral composition of △C is mainly of ferromanganese carbonate series, and △C mineral composition of sediments in the East Sea is dominated by siderite. The existence of multiple solutions for the origin of △C results in the limitation of △C as an index of oil and gas geochemical prospecting.