HOLOCENE SEA LEVELS AND PALAEOENVIRONMENTS, SOUTHEAST SULAWESI, INDONESIA: APPLICATION OF MANGROVE PALYNOLOGY AND THE TRANSFER FUNCTION APPROACH

A full understanding of sea-level, ice sheets, ocean circulation, tectonics and regional climate requires observations of relative sea-level change from far-field locations (regions distant from the major glacial centres). The coastline of Southeast Sulawesi, Indonesia is a particularly important far-field location as relative sea-level reconstructions give information on the nature and response of materials of the crust. Reconstructions through the Holocene allow modellers to quantify lithospheric thickness and mantle viscosity and establish lateral variations in mantle structure across the continental/oceanic margin; aims not achieved using long records from other far-field locations. These variables are important to modelling the earth's response to future climate and sea-level change and can be applied to locations where Holocene relative sea-level reconstructions are hard to obtain. The study area is located within the Wakatobi Marine National Park, which is 13,900km2 in size and consists of raised Quaternary coral atolls attached to the submerged continental crust of the Tukang Besi block.

We have developed a microfossil transfer function to reconstruct former sea level. We have collected contemporary pollen samples from three mangrove transects in Southeast Sulawesi, Indonesia. The Family Rhizophoraceae and particularly the genus Rhizophora dominate the mangroves of S.E. Sulawesi in line with previous studies from Southeast Asia and Northern Australia. 16 mangrove pollen species were identified within the contemporary samples. The transfer function demonstrates that reconstructions using this dataset can achieve predictions accurate to ± 11 cm.

Sea-level observations from Southeast Sulawesi reveal an upward trend of Holocene relative sea level from a minimum of -4.85m 7300 cal yrs BP to the present elevation. Relative sea-level rises rapidly; greater than 1.7 m between 7300 – 6750 cal yrs BP with a further 1.5m rise between 6750 and 4650 cal yrs BP. Thereafter, sea level continues to rise at a steady but reduced rate (equivalent to 0.37mmyr-1). Relative sea-level never rises above present.