Paleoclimate And Paleoceanography Study Of The Middle Okinawa Trough In The Last 37 Cal Ka BP

Based on the characteristics of grainsize, δ¹³C and δ¹⁸O of planktonic foraminifer, sea surface temperature (SST), the δ¹⁸O of sea water (δ¹⁸Ow), terrestrial long-chain alkanes and long-chain alkenone of a piston core DGKS9604, which was retrieved from the western continental slope of the middle Okinawa Trough, and by comparing with nearby piston core DGKS9603 located in the trough bottom, the millennial-scale paleoclimate changes, the variation of the main path and strength of the Kuroshio Current, characters of terrestrial organic carbon input and paleo-productivity of the sea surface are discussed in this paper.The sedimentation rate (SR) of the middle Okinawa Trough of the last glacial period is mainly controlled by the sea level change and the wetness of the source area. The SR decreases gradually from OIS3, OIS2 to OIS1 in both the contiental slope and the trough bottom. During 33～30 Cal ka BP the climate in Chinese mainland was warm and wet, which led the increased runoff to the Okinawa Trough and the maximum SR of the last 37 ka. During the last glacial period the amount of terrestrial material inputting into Okinawa Trough was high, which made the SR twice as that of the postglacial period. In the semi-abyssal area continental slope is the major accumulation site of terrestrial material; the SR in the trough bottom is greatly lower than that of the slope; however their difference decreased during glacial period.The SST difference between Holocene (25.1 ℃) and LGM (22.1℃) of the middle Okinawa Trough is 3.0℃, and the δ¹⁸O difference is 1.4‰, both are higher than that of the open seas. The δ¹⁸O and U₃₇^K -SST variations show that 9 obvious cooling events happened in the last glaical and postglacial period in the study area. The characteristics and possible causes of the H3～H1 during the last glacial period, the 5 rapid climate changes in the last deglacial period and the cooling events happened in the early, middle and late Holocene are deeply discussed in this paper. Spectral analysis shows that there is 1 000 a period of climate change of the Okinawa Trough...