DIATOM ASSEMBLAGES RESPONSE TO SEDIMENT FACIES CHANGE DURING THE LAST 3000 YEARS IN TV1 CORE, MEKONG RIVER DELTA

Abstract

Diatom data from the boring core TV1, located at Duyen Hai district, Tra Vinh province in the Mekong River Delta is one of good tools to research on sediment facies change in Holocene. There are five diatom ecological groups: marine plankton, marine-brackish, brackish, fresh-brackish and fresh water groups. The stratigraphical change of these groups is divided into four diatom divisions, namely DI, D2, D3 and 14. Each diatom divisions is closely related to the sedimentary environment caused by Holocene sea-level change. Deltaic sediment is characterized by marine plankton and brackish water groups. The six depositional facies were recognized in ascending order: Late Pleistocene deposits, regressive lag deposit, prodelta mud, delta front sandy silt, sub-to intertidal flat silty sand, subaerial delta plain sand and sandy silt facies. There is not any evidence of marine facies from this core. The sedimentary succession of sea-level regression suggests that the Mekong River Delta has prograded to the site since 2,719 yr. BP.