The topographical development history of the continental shelf and coastal zone in the South Central Vietnam from Da Nang to Phan Thiet

Abstract

The topographical forms had been generated in the Quaternay period belonging to 8 main original groups: alluvial, marine, alluvialmarine, marine-aerial, lake and swamp, biology, tectonics, and volcanoes. In the Pleistocene and Holocene interval, topography was clearly differentiated according to the Neotectonics and East Sea level changing activites. On the continent, the authors had found 6 sea shelf levels including: 75-80 m (Pliocene), 40-65 m (EarlyMiddle Pleistocene), 20-30 m (Late Pleistocene), 10-15 m (Late Pleistocene), 4-5 m (4,500 years BP) and 1.5-3 m (2,120 - 3,100 years BP). On the sea bed, some more levels were detected at the depths of: 0-5 m, 10-15 m, 20-25 m, 35-50 m, 50-65 m, 70-80 m, 90-130 m, 130-150 m, and 180-200 m; while paleosandunes located at the depths of: 170-200 m, 120-150 m, 90-110 m, 30- 50 m, 20-35 m, and 15-20 m. During the low stand system tract, five estuarial deltaic bands were formed in corresponding depths. The research results also showed that the sea level variation curve of South Central Vietnam tended to be coincided with the global sea levels but different in each glacial and interglacial period.