Evidence for ca. 7‐ka maximum Holocene transgression on the Peninsular Malaysia east coast

Abstract

ABSTRACTIn situ fossil coral and shelly marine deposits occur up to 50 cm above mean sea level in north‐east Peninsular Malaysia. The fossil reef comprises over 15 coral species and associated molluscs. Radiocarbon ages of corals range from 7238 to 6909 cal a BP. The reef occurs adjacent to bedrock hills that formed a mainland peninsula when the coral was living. Abundant well‐preserved fossil molluscs with bivalves commonly articulated occur in ditch tailings from coastal plains flanking these hills. Landward, a sand ridge represents part of the maximum transgression shoreline. When alive, the fossil coral reef required clear water and full marine conditions seaward of the peninsula. The maximum transgression here occurred ca. 7 ka with stable environmental conditions persisting long enough for diverse coral reef development. Assuming a similar tidal range to today, relative sea level ca. 7 ka would have been between 1.4 and 3 m above present. Between then and ca. 6 ka, abundant sediment supply resulted in barrier‐beach construction seaward of the coral reef, converting the area to a lagoonal environment unsuitable for coral and burial by muddy deposits. Assuming that regional relative sea‐level data indicate maximum Holocene highstand up to +5 m between 6 and 4 ka are correct, then the maximum transgression preceded maximum sea level by at least 1000 years.