Pleistocene to Holocene transition in the central basin of the Gulf of Thailand, based on geoacoustic survey and radiocarbon ages

Record of the Last Glacial Maximum and postglacial sea-level rise in the central Gulf of Thailand, some 140 km offshore of the Malay Peninsula, was studied along a NW-striking section (water depth 55–82 m below the present MSL) by means of geoacoustic surveys, shallow gravity coring, and radiocarbon dating. The record comprises evidence of valley incision followed by estuarine to marine transgression, which was interrupted by deltaic progradation. The valley incision and delta formation are attributed to the Kelantan River draining the Malay Peninsula. The delta growth was halted at 10.4 cal kyr BP by transgressive ravinement followed by emplacement of a thin, condensed mantle of modern marine muds. Such age is compatible with the fast but diachronous nature of this transgressive event that, according to previous estimates, began in the central Sunda Shelf at 11–11.5 cal kyr BP and reached the head of the Thailand Bay at 8–7 cal kyr BP. The presence of deltaic deposits within postglacial transgressive systems tract is uncommon on extremely wide and accommodation-dominated shelves (such as the Sunda Shelf), and is here interpreted to reflect a combination of decelerating sea-level rise (13–10 cal kyr BP) with increased precipitation and sediment yield, coupled with the reactive nature of the Kelantan River catchment.