Bulletin of the Geological Society of Malaysia, Volume 19, April 1986, pp. 481 – 494
Comparative Sedimentology Division, Utrecht State University 1983.
Abstract: Beach placers and associated relatively flat unconformities, thought to be abrasion surfaces, have been reported from areas off Billiton, Indonesia, off the west coast of Thailand, and off West Malaysia. A succession with a quartz pebble conglomerate overlying a bedrock surface with animal borings, exposed in coastal plain tin mines on Phuket, is described. It is interpreted to have formed in a gravel beach environment. The conglomerate has abrupt upper and lower boundaries, shows inclined layering, and has sorting characteristics similar to those of modern gravel beaches. The bedrock is saprolitic, forms the lower part of a weathering profile of which the upper part has been eroded. Overlying the conglomerate is an about 1 m thick poorly sorted sandy to gravelly layer. The layer contains many plant remains, and festoon-shaped gravel strings and channel fill structures are common. The deposit is interpreted to have formed in secluded intertidal to supratidal terrain. The top of this unit is peaty and samples for Carbon-14 datings were taken from it. Where the layer occurs at about 9 m below sea-level the 14C concentrations were below reliability, i.e. ages over about 50,000 yrs. BP. The dating of a similar layer in a similar setting at a level of 6 m below sea-level gave an age of 31,050 yrs. BP. Available data on abrasion surfaces in the region come from too few areas which are located too far apart to allow for regional correlation yet.