Based on cores and well logs, the analyses of tectono-sedimentary setting and facies show that F4 unit formed by submarine fan located in the continental rise. Lower Devonian F4 unit can be divided into upper cycle and lower cycle by a correlating fan-wide marine mud datum called “middle mud”, which correspond individual the two-stage of the submarine fan evolution. This study provides not only correlation strategy of submarine fan, but also a reliable geological model for the further development of F4 unit.