Geomorphological Evolution of the Andaman Sea Offshore Phang Nga Province (Thailand) during the Holocene: An Example for a Sediment Starving Shelf

Understanding the development of shallow seas is essential, as they provide a major environmental and economic resource. An investigation of the Holocene development and the present conditions of the Andaman Sea shelf was carried out based on hydroacoustic surveys and sedimentological sampling. The results show that the relative sea level in the offshore Phang Nga province (Thailand) was at a present-day water depth of approximately 63 m at 13 cal ka BP. This agrees with the sea level development of the Sunda Shelf. Since that time, the Andaman Sea continental shelf developed as a sediment-starved environment, with less than 2 m thickness of sediment deposited during the Holocene on the crystalline basement over large areas between 60 m and 20 m water depth. Between 28 and 17 m water depth, a series of moribund asymmetrical sand ridges exist. These ridges were formed around 9.0 ka cal BP. They strike oblique to the coastline. On the seaward side of the sand ridges, small NW-SE directed submarine dunefields developed, shaped by monsoon-induced currents.