A MULTIPROXY PALEOENVIRONMENTAL RECONSTRUCTION OF MARINE SEDIMENTS FROM TWO INTERGLACIALS: WESTERN SUNDA SHELF, SOUTHERN SOUTH CHINA SEA

Two marine gravity cores from ~60 m water depth were collected from the western Sunda Shelf (southern South China Sea) to characterize Quaternary paleoenvironments. The cores were dated to the current and previous interglacial periods. Cores, TER15-GC11B and TER15-GC8A, located ~40 km and ~90 km offshore of Kuala Terengganu, peninsular Malaysia, are composed of sandy mud. They yielded radiocarbon age estimates (from benthic foraminifera) of 10,600–5,800 cal years BP and 47,000–43,000 cal years BP, respectively, although the latter dates are likely minimum ages. Direct comparison of both cores indicates subtle but significant differences. Bulk sediment magnetic susceptibility (BMS) data indicate higher values for the older material. This correlates with a ca. 1% higher iron (based on X-ray fluorescence spectrometry) content in the older sediments that could potentially explain the higher BMS values. Other elements have similar values for both cores. It is interesting to note that Ca content is slightly higher in the younger core, which inversely relates with the BMS data. This might suggest stronger terrestrial influence in the older core. However, the older materials present a significantly higher ratio of planktonic foraminifera, which suggests a strong marine influence. Differences in BMS values may be explained, perhaps due to dissolution of carbonates in the older sediments that could increase BMS values artificially in agreement with lower Ca concentrations in the older core. An ongoing study of the benthic foraminiferal assemblages will help resolve this question.