Abstrak
Microorganism analysis have been used to study environmental and sea level changes at Kepulauan Riau site, Malaka Strait. Four cores were taken for microorganism as foraminifera, nannoplankton and palynomoph analysis. Samples were taken about 5 cm interval from these cores. A cross section reconstructed based on the core description. The sediment from the core base are grey clay and greenish sand with mollusk, foraminifera and nannoplankton. The site was a shallow marine environment at Early Holocene (0.01 Ma). The middle part is marked by higher abundancy and diversity of marine species indicated deep marine environment. They suggest this sediment were deposited during the Holocene transgression, perhaps in response to sea level rise in mid-Holocene. The period following mid-Holocene, sea level stabilization is marked by coastline progradation. Marine species decrease in upper level suggesting seaward shifting of deposited environment due to relative sea level fall. Sea level fall and accretion of sediment might have altered the environment to shallower. This establishment then promoted further sedimentation at the site. During the deposition of upper part, minor relative sea-level rise and fall frequently occurred, altering depositional environment of the study slightly deeper and shallower. The Kepulauan Riau site was at or close to the low sea level due to increased fluvial activities.
