HOLOCENE GEOLOGY AND MULTI-PROXY PALEOENVIRONMENTAL RECONSTRUCTION OF THE SUNDA SHELF OFF THE EAST COAST OF PENINSULAR MALAYSIA

Abstract

In May (2016), six 1.25 to 2.2 m long gravity cores were collected at water depths ranging from 68 m to 77 m along a transect crossing the incised Chao-Phraya paleo-river valley between Peninsular Malaysia and southern Vietnam, on the Sunda Shelf (southern South China Sea). The objective of this research is to use multiple proxies to make paleoenvironmental reconstructions of the cored sediments’ depositional environments. The six cores provided 130 samples selected for analysis of bulk sediment magnetic susceptibility (BMS), 66 for elemental analysis by means of x-ray fluorescence spectrometry (XRF), 52 for analysis of foraminiferal assemblages, and 10 for AMS radiocarbon dating. BMS data show that sediments near the base of the cores typically display higher magnetic susceptibility than sediments closer to the surface, although results vary between and within cores. Other studies show that variations in BMS magnitudes are a result of changes in terrestrial sediment flux during deposition. XRF data will help constrain origins on the cored sediment (e.g. terrestrial or marine). For example, aluminum is typically concentrated in aluminosilicates and can be used as a proxy for variations in grain size. Concentrations of calcium, when inversely correlated with aluminum, are commonly interpreted to derive from a different source (e.g., marine). Foraminiferal assemblages will be used as a proxy for environmental change in conjunction with BMS and XRF.