A RECORD OF HOLOCENE PALEOCLIMATE FROM THE SUNDA SHELF, SOUTH CHINA SEA

The East Asian Monsoon (EAM), driven by differential heating between the continent and adjacent ocean, is a critical element of global atmospheric circulation and strongly influences wind patterns, precipitation, sea circulation, continental runoff, and nutrient transport to the South China Sea and surrounding land regions. Changes in EAM strength and duration can cause severe droughts and floods in these heavily populated areas. Late Pleistocene and Holocene monsoon patterns for the region have been reconstructed by applying various geochemical approaches to sediment cores from the deep South China Sea. However, this is one of the first studies to provide a record of Holocene climate from the shallow Sunda Shelf in the southern South China Sea.

Two mud-dominated sediment cores were collected from flooded, north-south trending fluvial paleochannels on the inner Sunda shelf north of Bintulu, Sarawak, Malaysia. Given the rarity of planktonic foraminifera in this shallow water (52–63 m water depth), AMS radiocarbon age estimates of the benthic foraminifer Cavarotalia annectens provide age control for the cores. A total of 19 samples, spaced 20 cm apart, were dated in core D42. This core, 3.8 meters in length, yields a detailed record of over 3000 years. Fifteen samples, ca. 16 cm apart, were dated in core D45, 2.6 meters in length. This core, collected from a slightly deeper location on the shelf, provides a record of over 7000 years. Contiguous, 2 cm samples provide a ca. 20-year resolution in D42 and a ca. 50-year resolution in D45. Mg/Ca ratios, δ¹³C and δ¹⁸O of planktonic foraminifera (Globigerinoides spp.) are being analyzed to define variations in sea surface temperature, salinity, and nutrients. These factors are related to changes in precipitation and runoff and thus provide information on past characteristics of the EAM.