Abstract

65 genera and 51 diatom species are discriminated from the samples of BT2 and VLI cores. Together with sedimentary characteristics, sedimentary structure and absolute 14C age, the change of diatom assemblages contributes considerably to study sedimentary environments in relation to Late Pleistocene-Holocene relative sea-level change in Ben Tre and Vinh Long. Estuarine sediment is characterized by an intermixture of fresh water and marine plankton diatom assemblages. Embayment or open bay sediment is characterized by marine plankton diatom assemblages. The predominance of Thalassiosira eccentrica and Thalassionema nitzschioides, Coscinodiscus radiatus, C. nodulifer is the clear evidence of maximum Holocene transgression dated ca. 5,000-6,000 yr. BP in the Mekong River Delta. Deltaic sediment is characterized by marine plankton - brackish water diatom assemblages.