ABSTRACT

During Leg 184 we will core hemipelagic sediments in the South China Sea (SCS) to determine the evolution and variability of the East Asian monsoon during the late Cenozoic. Of the six primary proposed drill sites, five are located on the northern continental slope of the SCS in water depths ranging from 1265 m to 3190 m. In the southern SCS, one site will be located on the southern margin in 2830 m water depth.

The major goals of Leg 184 are to improve our knowledge about the variability of monsoonal climates, including millennial to possibly centennial variability from high-sedimentation rate records (SCS-1), orbital-scale variability from records at all SCS sites, and tectonic-scale variability from late Cenozoic sections (Sites SCS-4 and 5). The records from the SCS will be used to establish the links between the East Asian and Indian monsoons and to evaluate mechanisms of internal (climate system feedbacks) and external (orbital and tectonic) climate forcing. We seek to test a suite of hypotheses that link uplift of the Himalayan and Tibetan Plateau complex (HTC) to both the intensification of the Asian monsoon and late Cenozoic global cooling. The proposed drilling program in the SCS will enable comparison of the Chinese terrestrial record with the marine records of monsoonal climates and hence provide an additional regional constraint on the scenarios for monsoon evolution.

Leg 184 has a number of related major scientific objectives:

1. Obtain continuous sequences of hemipelagic sediments that record the East Asian climate history during the late Cenozoic;
2. Establish records of monsoonal proxies for the SCS, including the variability of sediment properties, the rates of sediment accumulation, and the chemical, isotopic, and species variability of flora and fauna;
3. Establish stratigraphic ties between the SCS marine record and the terrestrial records of China;
4. Establish the relationship of East Asian monsoon variability with orbital forcing, glacial forcing, and internal feedbacks within the climate system;
5. Compare the evolution of the East Asian monsoon in the SCS with the Indian monsoon in the Arabian Sea to identify common causality;
6. Test several proposed scenarios for the relationship between the Tibetan Plateau uplift, monsoon evolution, and global cooling; and
7. Improve our understanding of seasonality in the low-latitude SCS and how it relates to the stability of the Western Pacific Warm Pool and the strength and evolution of the winter monsoon.

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