Site 1202 (24°48.2´N, 122°30.00´E) is located in 1274 m deep water on the southern slope of the southwestern part of the Okinawa Trough, which extends from Kyushu, Japan, to the northeast side of the island of Taiwan (Fig. F1). The Okinawa Trough is an active intracontinental backarc basin bordered to the south by the Ryukyu arc-trench system (Sibuet et al., 1998; Wang et al., 1999). Sedimentation rates are high because of terrigenous input from Taiwan and the East China Sea shelf (Boggs et al., 1979; Lin and Chen, 1983). The East China Sea continental shelf was above sea level during the LGM, and only the Okinawa Trough was submerged. Unlike most parts of the Pacific, the seafloor in the Okinawa Trough lies well above the carbonate compensation depth, so calcareous microfossils can be preserved. This makes Site 1202 an ideal site for obtaining a high-resolution record of the Quaternary history of the Kuroshio Current.
A 20-m-thick sequence from Hole 1202A (100–120 meters below sea floor [mbsf]) that contained a suspected magnetic excursion (Mono Lake; 105–108 mbsf) (Shipboard Scientific Party, 2002) and the entire sequence from Hole 1202B are the subject of this report. Both holes were cored at the end of Leg 195 with the advanced piston corer (APC). Hole 1202B was cored with the APC to refusal at a depth of 111.6 mbsf and was deepened with the extended core barrel (XCB) to 140.5 mbsf. The sedimentary succession consists of one lithostratigraphic unit characterized by homogeneous, slightly calcareous, bioturbated clayey silt with isolated sandy intervals and fine sand laminae. Thin sandy layers have been interpreted to be mostly detrital carbonate, indicating episodes of turbidity current activity (Shipboard Scientific Party, 2002). There are no visible ash layers, but one sample with volcanic glass particles was identified by smear slide analysis conducted on the Hole 1202D sequence (Shipboard Scientific Party, 2002).
Biostratigraphic analysis (Shipboard Scientific Party, 2002) of core catcher samples, especially the absence of pink Globigerinoides ruber, indicates that the sequence is younger than 127 ka, suggesting that the average sedimentation rate is at least 320 cm/k.y. Previous work (Jian et al., 2000) on Holocene sediments from southern Okinawa Trough showed an average sedimentation rate of ~20 cm/k.y. with exceptionally abrupt changes in the sedimentation rates, probably caused by sudden changes in the input of terrigenous material.