The determination of 230Th in the sediments: sediment accretion in the Mangrove Forests of Tanjung Piai, Johore , Malaysia

Abstract

Accumulation of element Th with depth was determined in a 150 em core sediment obtained from the mangrove forest of Tanjung Piai, Johore, Malay­sia. In this study, a 230Thexcess method was used where the element relies on a constant production rate of 230Th from the radioactive decay of dissolved 234U in the water column. Applying the 230Thexcess and 230Thexcess/232Th method, average sedimentation rates of 0.84 cmyr-1 and 0.88 cmyrl were obtained, respectively. If this sedimentation rate is applicable to the core, the mangrove forest in the study sites was probably in immature stage with an estimated age of about 120 years. This finding suggests that the mangrove forests are not just passive colonizers of mud banks, but actively capture mud to create their own environments. Mangroves are thus an important sink for the fine sediment from rivers and coastal waters.