Tectonic Activities and Evolution of the Red River Delta (North Viet Nam) in the Holocene

The Red River delta with an area of about 12 620 km 2 is one of the largest deltas of Viet Nam and it also is one of the remarkable deltas of Asia. The delta was formed during the Holocene, mainly from 9000 years ago to the present. The Red River delta belongs to the NW tip of the large tertiary basin that is the Red River basin (Song Hong basin). The NW tip of the Red River basin presents as Ha Noi graben, which is controlled by the Chay River fault in the SW and the Lo River fault in the NW. Both faults are belonging to the regional Red River fault zone that is a boundary between the South China block and the Indochina blocks. The Red River delta was formed on the top of tectonic active area. Due to tectonic activity the Red River bed is differentiated and revealed as in-uniform distribution of the Quaternary sediments. Evolution of the Red River delta has been closely connected with the Pliocene‒Quaternary tectonics, specifically during transgression period after the last glacial maximum. The submarine area advanced along the NE and SW subsidence zones of the Red River delta area and created two remarkable lagoons, meanwhile the central part it had resisted transgression process and created a protrusive zone. Our study recognized that there were at least two tectonic movements occurred in the region since the Late Miocene, after a cessation of left-lateral strike slip of the Red River fault zone: those are NE‒SW compression and then NE‒SW extension under the general right-lateral strike slip of the Red River Fault Zone.