Between 28 April and 1 May 2001, four holes were drilled at Site 1202 (24°48´N, 122°30´E) off northeast Taiwan during Ocean Drilling Program (ODP) Leg 195 (Fig. F1). This marked the first international scientific drilling of the Okinawa Trough under the auspices of the Deep Sea Drilling Project (DSDP) or ODP. The site is located on a gentle topographic high on the southern slope of the southern Okinawa Trough at 1274 m water depth (Fig. F2). Site 1202 was designed to obtain a high-resolution record of paleoceanographic changes of the Kuroshio Current during the latest Quaternary (Salisbury, Shinohara, Richter, et al., 2002).
The Kuroshio Current is the largest western boundary surface current in the North Pacific Ocean (e.g., Hsueh, 2000; Liu et al., 2003; Lee and Chao, 2003; Liang et al., 2003). It plays an important role in the meridional transport of heat, mass, momentum, and moisture from the Western Pacific Warm Pool to high latitudes in the North Pacific. Its role in the Pacific is as important as that of the Gulf Stream in the North Atlantic, but very little is known of its evolution except during the latest Quaternary. Because most seafloor in the western Pacific is deeper than the carbonate compensation depth (CCD) (~3500 m), it is difficult to obtain a suitable sequence to study the origin and history of the Kuroshio Current. Site 1202 was chosen for drilling because it lies under the path of the Kuroshio Current and its shallow water depth in the southern Okinawa Trough.
Deep scientific drilling had never before been conducted in the Okinawa Trough. Drilling at Site 1202 would open a deep time window into the sedimentary record, allowing long-term paleoceanographic changes and the effects of tectonics and sea-level fluctuations on sedimentation in the trough to be examined for the first time. However, because the sedimentation rate at Site 1202 (3.4 m/k.y.) was much higher than those previously documented (~0.5–1.1 m/k.y.), the sedimentary record spanned less than ~120 k.y. despite the deep penetration to 408 meters below seafloor (mbsf) (Shipboard Scientific Party, 2002). Almost concurrent with the Leg 195 expedition, the Marion Dufrense cored a series of piston cores in the southern Okinawa Trough for the International Marine Past Global Change Study (IMAGES) program. The results from Site 1202, compared with dating results from IMAGES cores and other recent studies of sediment traps and short box-cores in the area, explain well the high sedimentation rates observed in the deep hole.
Although some Site 1202 postcruise studies are still under way, this article synthesizes the available results. Most of the postcruise research results were assembled for publication in a special issue of Terrestrial, Atmospheric, and Oceanic Sciences in 2005 (TAO, 16[1]). Other sources include several personal communications from researchers. To facilitate interpretation of the results from Site 1202, the results of recent tectonic, oceanographic, and sedimentologic studies of the region are also summarized.