Late Quaternary Planktic Foraminifer Fauna andMonsoon Upwelling Records from the Western South China Sea, Near the Vietnam Margin (IMAGESMD012394)

Abstract

Marine sediment core MD012394 from the Vietnam coastal upwelling area in the western South China Sea was investigated in order to reconstruct the last Quaternary monsoon upwelling based on planktic foraminifer fauna assemblages and fauna-based sea surface temperature (SST) estimates. The age model of core MD012394 was constructed using oxygen isotope stratigraphy of the planktic foraminifer G. sacculifer, with 10 accelerator mass spectrometry (AMS) 14 C dating of planktic foraminifers from the sediment samples. Our studies on the relative and absolute abundances of planktic foraminifer assemblages reveal eight dominant species in core MD012394: N. dutertrei + N. pachyderma (right coiling), G. ruber, G. glutinata, G. sacculifer, P. obliquiloculata, G. menardii + G. tumida, G. calida, and G. inflata. In a Q-mode factor analysis of the fauna abundance data, the fauna factors show variations that do not parallel the glacial/interglacial changes throughout the last 135 kyr. The relative abundance patterns of G. inflata and N. dutertrei (including N. pachyderma-R) are interpreted as hydrographic proxies for East Asian summer and winter monsoon, respectively, in the current study. We calculated the fluctuations in the SST using the Revised Analog Method (RAM) in MD012394 and found that the abundance changes of the summer monsoon upwelling indicator G. inflata were similar and nearly synchronous. This suggests that the summer monsoon-driven upwelling signal was strong near the local summer insolation maximum, which induced low SSTs, particular around~11, 33, 59, and 83 kya. Our studies support the view that the strengths of both summer insolation and the East Asian summer monsoon have determined the relative abundance of planktic foraminifers and the SSTs in the western SCS during the last 135 kyr.Key words: South China Sea, Planktonic foraminifer fauna, Sea surface temperature, East Asian monsoon, Summer insolation Citation: Yu, P. S., H. S. Mii, M. Murayama, and M. T. Chen, 2008: Late quaternary planktic foraminifer fauna and monsoon upwelling records from the

Fluctuations in the late Quaternary East Asian winter monsoon recorded in sediment records of surface water cooling in the northern Japan Sea

“…South China Sea sediments provide some information on fluctuations in the intensity of the EAWM. A number of micropaleontological, sedimentological, and geochemical proxies for the EAWM have been proposed (Jian and Tian, 2009), such as surface productivity, winter SST, and clay mineralogy in the South China Sea (Wang et al , 1999; Jian et al , 2001; Zhao et al , 2006; Yu et al , 2008; Shiau et al , 2008). High productivity related to enhanced upwelling and low SST during winter in the northern South China Sea occurs when the EAWM is more intense.…”

“…High productivity related to enhanced upwelling and low SST during winter in the northern South China Sea occurs when the EAWM is more intense. The proxy records in the South China Sea (Jian et al , 2001; Zhao et al , 2006; Yu et al , 2008; Shiau et al , 2008) indicate that the intensity of the EAWM is enhanced during periods of low summer insolation.…”

Introduction to the Special Section “Proxy Records and Mechanistic Studies of the Late Quaternary Paleoceanography of the Western Pacific Marginal Seas Using IMAGES Cores”

“…It is evident that more records and more novel approaches such as these are needed to resolve questions regarding the relationship and phases of the winter and summer monsoons. Yu et al (2008) reported planktonic foraminiferal assemblage and SST records of the last 135 kyr for core MD012394 from the Vietnam coastal upwelling area in the southwestern SCS, and they focused their discussion on summer monsoon variability. Using a Q-mode factor analysis of the fauna abundance data, Yu et al (2008) found that the relative abundance of G. inflata (Factor 3) can be used as a summer monsoon proxy.…”

“…Yu et al (2008) reported planktonic foraminiferal assemblage and SST records of the last 135 kyr for core MD012394 from the Vietnam coastal upwelling area in the southwestern SCS, and they focused their discussion on summer monsoon variability. Using a Q-mode factor analysis of the fauna abundance data, Yu et al (2008) found that the relative abundance of G. inflata (Factor 3) can be used as a summer monsoon proxy. High loadings of this summer proxy were recorded around 11, 33, 59, and 83 ka when the local summer insolation was near the maximum.…”