LATE HOLOCENE PALEOCLIMATE RECONSTRUCTION OF THE SUNDA SHELF (SOUTH CHINA SEA) OFF KUALA TERENGGANU, PENINSULAR MALAYSIA BASED ON MAGNETIC SUSCEPTIBILITY OF BULK SEDIMENT

The East Asian monsoon (EAM) system affects precipitation and continental runoff into the shallow waters of the Sunda Shelf (South China Sea). Given the importance of the EAM to agricultural activities in SE Asia, it is important to understand past changes in the strength of the monsoon so that the range of future changes can be understood. Paleoclimatic records are lacking from the Sunda Shelf due to the generally thin Holocene sedimentary record but flooded and in-filled paleoriver valleys can provide a thicker sedimentary record.

Three ca. 2m gravity cores were taken 52 km off the coast of Kuala Terengganu, peninsular Malaysia at approximately 60m water depth in the flooded, sediment-filled valley of the Terengganu River. Two of the three cores selected for further analysis, TER14-GC5 and TER14-GC7, comprise an offshore extension of a previously collected suite of cores. Both cores were sampled at 1 cm intervals. A chronology for the cores is based upon AMS radiocarbon analysis of the benthic foraminifer Cavarotalia annectens. Based upon results from cores taken several km to the west, sedimentation rates for the area average ca. 0.06 cm/yr. Thus core TER14-GC5 contains a ca. 7,000 year record. The downcore profile of bulk sediment magnetic susceptibility (BMS) reveals a net change at ca. 4,000 yr BP that might be related to an increase in continental run-off and hence precipitation. The timing of this change suggests a possible relation with global climatic changes reported elsewhere. X-ray fluorescence (XRF), oxygen stable isotopic analysis of the planktonic foraminifer Globigineroides ruber, and additional carbon-14 ages will be performed in order to support these inferences of late Holocene paleoclimate in the Sunda Shelf.