Holocene elevated sea levels on the north coast of Vietnam

We present evidence of elevated Holocene sea levels on the north coast of Vietnam, comprising radiocarbon dating of raised coastal geomorphological and palaeobiological features at localities on the margins of the Bac Bo (Red River) Plain. This evidence indicates that by ca. 5500 cal yr B.P. mid-tide lay approximately 5.4 m above national datum, that is 3.25 m above present local mid-tide. By c. 3500 cal yr B.P., sea level was lowering and, by ca. 2000 cal yr B.P., mid-tide lay at or above 1.5 m above present local mid-tide. It is not yet possible to infer patterns of sea-level fluctuation other than an overall lowering of elevation, although the separation of the raised and modern erosion notches does suggest two dominant mid to late Holocene periods of erosion — probably periods of sea-level still-stand or relatively slow sea-level change. The intervening period of relatively rapid sea-level change and associated reduced erosion probably dates to after ca. 2000 cal yr B.P.