FY99 Science Program Summary

Abstract

Leg 184 will core hemipelagic sediments in the South China Sea (SCS) to determine the evolution and variability of the East Asian monsoon in the late Cenozoic. Of the six proposed drill sites (Fig. 1), five are located on the northeastern continental slope southeast of the Dongsha Islands, and one is on the southern slope south of the Nansha Islands near the Sunda Shelf, with water depths ranging from 625 m to 3190 m. The main goal of Leg 184 is to improve our knowledge of the link between climate and tectonics. Land-based studies in China and other parts of East Asia have developed a four-stage model of monsoon evolution. The proposed drilling will calibrate the terrestrial record with that of the global ocean. It is suggested that uplift of the Tibetan Plateau is responsible for both the late Cenozoic global cooling and for the intensification of the Asian monsoon; therefore, a comparison between records of monsoons, denudation rates, and climate cooling in the SCS will test this hypothesis. Drilling of high-sedimentation-rate hemipelagic deposits in the SCS will provide the proxy records for this test. There are four major scientific objectives for the leg: (1) to obtain a continuous marine record of East Asian climate history for the late Cenozoic and to compare the evolution of the East Asian monsoon system with the South Asian or Indian monsoon system; (2) to examine the possible relationship between the Tibetan Plateau uplift, monsoon evolution, and global cooling; (3) to improve our understanding of the stability of the Western Pacific Warm Pool and the role of seasonality changes in low-latitude marginal seas; and (4) to establish a detailed history of sea-level changes for the SCS.