Abstract:

Neotectonic activity which includes recently tectonic activity is the basic period of time to form the types of terrain, landforms that we can see nowadays. Many evidences of tectonic activity have been found in the river valley, to allow us inferences about the stages of tectonic activity has undergone. One of the most important evidence was the existence of the Quaternary sediments that relate to Da river. These sediments are studied, analyzed in this paper as a basis tool for explaining the tectonic activity that occurred in the downstream of Da river valley. Accordingly this river is divided into 3 sections with different in tectonic activity. The first section from Hoa Binh hydroelectric dam to Tan Thinh commune with 10 km long, river’s meandering, thick Quaternary sediments, are related to tectonic subsidence activity. The second section is from Tan Thinh commune to Hop Thinh commune with 15 km long, straight river in morphology, thin Quaternary sediments, are governed by tectonic uplift activities. The third section is from Hop Thinh to where Da river that intersects with Hong river, this section is meandering river, thick Quaternary sediments, are governed by tectonic subsidence activities.