Late holocene sea level changes in the east coast of the Malay-Peninsula

Abstract

The relative sea level (RSL) history of Terengganu, east coast of the tectonically stable Malay-Peninsula, of the last 2500 years was reconstructed from dated mangrove sediments. Microfossils, particularly pollens, were used for estimating the indicative meaning of each sea-level index point.

Pollen assemblages representing the top end of mangrove zone and the low end of swamp zone have an indicative meaning of 0.26±0.23 m and 0.33±0.26 m above local mean sea level respectively. The sea-level index points produced have all shown negative tendency of change, as the pollen assemblages have revealed a general environmental change towards a more freshwater condition. The more saline mangrove vegetation was graded into lagoon/riverine Nypa frusticans, or freshwater swamp Myrtaceae or Cyperaceae, depending on the distance of sampling sites from the palaeo-beach ridges.

The reconstructed RSL has indicated a RSL fall to below the present mean sea level roughly since the last 1500 years, reaching a lowstand with a minimal value of -1.28±0.26 m at 920-750 cal. year BP, before a transgression took place between 920-280 cal. year BP, for RSL to return back to the present level. This observation departs from the steady RSL decline to present as predicted by geophysical model.

This RSL fall suggests that, in addition to ocean siphoning and continental levering, the late Holocene RSL change in the far-field regions is also influenced by climatic driving forces such as Neo-glacial ice sheet expansion. The effects of these climatic factors have been recorded in some near- and intermediate- field regions. This is the first time that these effects are reported from a far-field region, the Malay-Peninsula.