Dalong Formation of Matan is mainly composed of pyroclastic rocks and siliceous rocks. Microscopic analysis shows : (1) pyroclastic rocks can be divided into three subtypes, namely tuffs, sedimentary-tuffs and tuffaceous sedimentary rocks, and further into seven types of microfacies, (2) siliceous rocks can be divided into two subtypes, namely biogenic siliceous rocks, biogenic and volcanogenic siliceous rocks, and further into five types of microfacies. These microfacies comprise twelve types of main lithofacies,which can vertically be grouped into six types of sedimentary succession. These successions indicate there are two types of turbidity current. One is low-density turbidity current which is evolved from high-density turbidity current generated by pyroclastic debris current induced by subaqueous volcanic eruption, the other is that is induced by slumps and brings early sediments of tuffaceous grains and siliceous biogenic grains. Our research into sedimentary successions and geomorphology of Matan area at this stage demonstrates that there do not exist submarine fans. On the contrary, it accepts low-density tuffaceous turbidity current readily, resulting in extensively and relatively thin-bedded deposits Dalong Formation of Matan is mainly composed of pyroclastic rocks and siliceous rocks. Microscopic analysis shows: (1) pyroclastic rocks can be divided into three subtypes, including tuffs, sedimentary-tuffs and tuffaceous sedimentary rocks, and further into seven types of microfacies, ( 2) Siliceous rocks can be divided into two subtypes, both biogenic siliceous rocks, biogenic and volcanogenic siliceous rocks, and further into five types of microfacies. Which microfacies include twelve types of main lithofacies, which can vertically grouped into six types of sedimentary succession One is low-density turbidity current which is evolved from high-density turbidity current. Currently, one of the two types of turbidity current is evolved from high-density turbidity current. sediments of tuffaceous grains and siliceous biogenic grains. Our research into sedimentary successions and geo morphology of Matan area at this stage demonstrates that there do not exist submarine fans. On the contrary, it accepts low-density tuffaceous turbidity current readily, resulting in extensively and relatively thin-bedded deposits