魏國彥2006-07-252018-06-282006-07-252018-06-282005http://ntur.lib.ntu.edu.tw//handle/246246/11877We measured the oxygen and carbon isotopic ratios of several foraminiferal species to reconstruct the hydrological structures of surface-waters during (1) the Marine Isotope Stages (MIS) 10-12 of the South China Sea and made a comparison with the record of MIS 1-6, and (2) the Holocene of Southern Okinawa Trough. In addition, organic carbon content and major elements in bulk sediment of the MIS 10-12 of two cores from the South China Sea were analyzed to examine the surface-water productivity and bottom water conditions. The fluctuation amplitudes of oxygen and carbon isotopic ratios of two studied species and the isotopic offsets between them are both smaller during the MIS 12-10 compared to that in MIS 1-6. It appears that the lower amplitude of solar insolation during MIS 10-12 is responsible for the smaller isotopic fluctuation. The offsets in δ 18 O and δ 13 C between the surface dwelling species (Globigerinoides ruber) and the thermohaline species (Neogloboquadrina dutertrei) during the MIS 10-12 become smaller compared to that in the MIS 1-6, signifying a less stratified surface-water column. The bottom waters are more oxygenated and probably also better ventilated during the interglacials as evidenced by lower content of total organic carbon and the elevated MnO/Al2O3 and P2O5/ Al2O3 ratios. The δ 18 O values of four foraminiferal species (Globigerinoides ruber, Neogloboquadrina dutertrei, Globorotalia menardii and Pulleniatina obliquiloculata) all display a decreasing trend during the past 8 kyrs while the offsets among them remain to be relatively constant. No sensible excursion can be identified to explain the drastic reduction of Pulleniatina obliquiloculata, a Kuroshio characteristic species, during 4.5 – 3.0 Ka. This result leaves the occurrence of the Pulleniatina obliquiloculata Minimum Event (PME) to be an unsolved paleoecologic enigma. A major shift to heavier δ 13 C values occurred at ~8 ka as manifested by all four species in the Southern Okinawa Trough. The offset in δ 13 C between G. ruber and P. obliquiloculata increased after 8 ka compared to the earliest Holocene. Integrating the various lines of evidence, we interpret that a stable hydrological condition in the Okinawa Trough established at about 8 ka and lasted until 2 ka.application/pdf839683 bytesapplication/pdfzh-TW國立臺灣大學地質科學系暨研究所paleomonsoonKuroshio Currentplanktic foraminifersOkinawa TroughSouth China SeaMIS 11thermocline[SDGs]SDG14reporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/11877/1/932611M002010.pdf