LAUSR

Abstract The Mekong River, which has high economic and ecological importance, has an extensive floodplain and delta plain that extends from Cambodia to Vietnam. Understanding the Holocene evolution of the fluvial system is needed in order to predict the future development of the system and develop a strategy to guide the sustainable management. This paper reconstructs the Holocene sedimentary evolution of the Mekong River floodplain, Cambodia, from 12 auger cores and 69 optically stimulated luminescence ages, and compares the reconstructed floodplain history with that of other large river systems. Rapid deposition of thick crevasse splays implies floodplain aggradation in response to sea-level rise before 6.5 ka. After 6.5 ka, when the sea-level reached a stillstand, the rapid aggradation ceased and levee and crevasse-splay deposition were localized near the anastomosing river channels. The rate of levee accretion was very low in the anastomosing river system (