HOLOCENE RELATIVE SEA-LEVEL HIGHSTAND PATTERNS, PENINSULAR MALAYSIA EAST COAST

Understanding the vertical components of crustal motion is critical to interpreting the relative sea-level (RSL) history and predicting future RSL trends for a particular region. The Holocene RSL curve pattern for Peninsular Malaysia is fairly typical for far-field tropical regions that are relatively tectonically stable. These RSL curves are generally characterized by mid-Holocene highstand of up to several meters above present following cessation of major meltwater inputs and subsequent descent to around modern levels in response to hydro-isostatic adjustment (HIA). Previous Holocene RSL curves that have been prepared for the Peninsular Malaysia region indicate RSL highstand of up to +5 m between 6 and 4 ka with subsequent either gradual or oscillatory descent to near modern level. These curves have been considered representative of the region although regional variability in HIA on the order of several meters are predicted by geophysical models. This study used both previously reported and new age and elevation data for RSL indicators from the islands and mainland of the Peninsular Malaysia east coast to refine previous RSL curves and to construct a RSL curve applicable for reference as well as detect potential variability along the east coast. Because RSL evidence in the form of raised fossil calcareous marine encrustations (mainly oysters) and in situ corals is especially common around the islands, the coasts of essentially all east coast islands were extensively surveyed and sampled. All age estimates were determined using radiocarbon analyses and calibrated appropriately. Data from the northern study area suggest RSL between +3 and +3.5 m from ca. 6 to 3 ka with a possible RSL increase to as much as +4.4 m ca. 4.5 ka. This pattern corresponds well with age data for cross-cutting strandplain deposits on the NE peninsula mainland. In the southern study area, RSL indicators above +3 m have not been observed suggesting the possibility of north-south HIA variability.