T41 Insights from Microfossils, from Traditional to Novel Approaches (Posters)

Sunday, 1 November 2015
9:00 AM - 5:30 PM
Exhibit Hall

HOLOCENE SEDIMENTARY RECORD FROM THE SUNDA SHELF, OFF PENINSULAR MALAYSIA: INSIGHTS FROM ELEMENTAL, ISOTOPIC AND BULK SEDIMENT MAGNETIC SUSCEPTIBILITY ANALYSES

Paper number: T41-10
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

Sediments of the Sunda Shelf (South China Sea), off northeast peninsular Malaysia, potentially preserve a record of Holocene environmental changes, including climate change. In the summer of 2014, two ca. 2 m gravity cores were collected on the Sunda Shelf in 60 m of water ca. 52 km from the mouth of the Terengganu River. Both cores were sampled in 1cm contiguous intervals and analyzed for magnetic susceptibility of bulk sediment (BMS), elemental composition (X-ray fluorescence), and oxygen and carbon stable isotopes on carbonates (foraminifera). The chronology of the cores was based upon AMS radiocarbon analyses of the benthic foraminifer Cavarotalia annectens, and covers most of the Holocene (last 10,000 years). BMS results correlate positively with Al, Fe, Ti, K, Mn, Ni, and Zn, and negatively with Zr. Aluminum (and therefore BMS) correlates negatively with Ca, P, and Sr. BMS results are likely driven by clay content (Al is a potential proxy for grain size - silt/clay ratio -), as indicated by its correlation with elemental concentrations. During Holocene intervals of strengthened monsoonal rainfall, the Terengganu River carried greater suspended sediment load onto the Sunda Shelf, which resulted in higher BMS values. During intervals of weaker monsoons, less continental materials and a greater ratio of marine carbonates were deposited onto the shelf, which could have resulted in lower BMS values. This relationship indicates changes in energy levels and sediment load of mainly terrestrially-derived materials carried by the Terengganu River.

The BMS up-core profile reveals a shift from higher BMS values to lower BMS values at ca. 5,500 cal yr BP. This change is interpreted to represent a shift in the climate, from a warmer, wetter interval at the base of the core to a drier interval towards the top. In contrast, stable isotopic values, proxies for ocean water chemistry, do not indicate any significant changes.