Late Holocene relative sea-level records from coral microatolls at Sentosa, Singapore

Late Holocene relative sea-level (RSL) data are important to understand the processes driving RSL change, but there is a lack of precise RSL data from the Sunda Shelf. Here, we produced the first Late Holocene RSL record from coral microatolls at Siloso Point in Sentosa, Singapore, demonstrating for the first time the utility of Diploastrea heliopora microatolls as sea-level indicators. We produced 12 sea-level index points and three marine limiting data. The precision of the RSL data (< ± 0.2 m, 2σ, and < ± 26 yrs uncertainties, 95% highest density region), combined with the surface profiles of the coral microatolls, reveal small RSL fluctuations superimposed on a net RSL fall of 0.31 ± 0.18 m between 2.8 kyrs BP and 0.6 kyrs BP, at background rates between -0.1 ± 0.3 mm/yr and -0.2 ± 0.7 mm/yr. There are fluctuations in the rate of RSL fall, with periods of stable (between 2.8 and 2.5 kyrs BP), rising (at ~1.8 kyrs BP) and stable (from 0.8 to 0.6 kyrs BP) RSL. The Siloso RSL record shows good agreement with published, high-quality RSL data within the Sunda Shelf, except at 0.8 kyrs BP when data from Merang, Malaysia indicate a lower RSL lowstand than suggested by the Siloso record. Comparison to a suite of glacial isostatic adjustment (GIA) models indicate preference for lower viscosities in the mantle. However, more high quality and precise Late Holocene RSL data are needed to evaluate the drivers of RSL change in the region, the existence of a regional Late Holocene RSL lowstand, and to better constrain the GIA model parameters for the region.