HOLOCENE PALEOENVIRONMENTAL RECONSTRUCTION OF THE SUNDA SHELF, OFF NORTHEASTERN PENINSULAR MALAYSIA

Paleoenvironmental studies of the Holocene sedimentary record from the western Sunda Shelf (southern South China Sea) off peninsular Malaysia suggest changes in the terrigenous component reflected mainly by the coastal development during the Holocene sea-level highstand. To better understand monsoonal evolution during the Holocene, two new gravity cores TER15-GC10A and TER15-GC9A were collected (2015) in 56 m of water 33 and 37 km offshore of Kuala Terengganu, Malaysia. Both cores are composed almost entirely of greenish-grey marine sandy mud. The cores were analyzed at high resolution for bulk sediment magnetic susceptibility (BMS), elemental analysis by x-ray fluorescence spectrometry, and foraminiferal assemblages. C-14 age estimates indicate that the sedimentary record encompasses at least 8,200 to 1,200 cal. yr. BP. BMS values decrease up-core, which correlates with a decrease up-core for Al, Fe, and Ti and an increase in Ca concentrations. These patterns are in agreement with data from an adjacent transect of six cores and are interpreted to reflect a decrease in the amount of terrestrial material supplied to the shelf since 8,200 cal. yr. BP or a dilution of detrital material by local productivity of marine carbonates. Preliminary planktonic foraminiferal data suggest the study area was under 50 to 60 m of water during the entire interval of sediment accumulation, in agreement with published sea-level curves for this region. Percent planktonics (although varied) generally increases up-core. Shallow shelf benthic foraminifera are present and abundant throughout, with a slight up-core increase in the ratio of calcareous to agglutinated foraminifera in both cores. This work expands our current understanding of Holocene paleoenvironmental evolution on the western Sunda Shelf.