Microgastropod records in paleoceanographical environment of southern shelf of South China Sea since 14 ka

Very diversified and abundant benthic microgastropods and planktonic microgastropods (pteropods) from core NS93-12-25 could provide a glance of change of the sea level in the south continental shelf of the South China Sea since last 14 ka. Research shows that general sea level changes of this sea area were rising and later rising after a short period of falling in this period. In the range from the bottom of the core to the core depth of 200 cm, individuals in big size are common in microgastropods and Turritella filiola is very rich, signifying the environment of the inner continental shelf in the last deglaciation stage. In the core depth range of 200—150 cm the continuously getting light of the ??18O, the regularly decreasing of the percentage content of T. filiola and the high diversification of microgastropods indicate the rising of the sea level. Especially at the core depth range of 175—150 cm the pteropods became dominant, making sure the fact that the high sea level possibly occurred in the early Holocene. Channels of surrounding straits connecting the adjacent sea thus were opened. But at the core depth of about 100 cm T. filiola became very rich again. This possibly implies that there was a short term of the sea level falling, resulting in the temporal closure of the channels. In the core depth range of 55—50 cm the Scaliola' s representatives relatively develop and this may be inferred to the cooling of climate.

Biogenic Sediments and Their Paleoceanographic Implication in West Pacific Warm Pool during the Pleistocene

Primary productivity has played an important role in the global carbon cycle during the Quaternary. The average Corg/N ratio was 7.0 from the core MD97-2140 in the West Pacific Warm Pool （WPWP） over the last 1 755 ka, which indicates a main contribution of marine organic carbon to the organic matter in the sediments. Large fluctuations in mass accumulation rates （MARs） of biogenics and lithogenics from this core since the marine isotope stage （MIS） 6 reflected the moderate variability in oceanographic condition, while tittle fluctuations in MAR-biogenics and -lithogenics from the MIS 59 to MIS 7 implied the relatively stable and uniform oceanographic condition, although the sea surface temperatures （SSTs） probably fluctuated by ca. 5 ℃. MAR-organic since the MIS 6 increased evidently during the glacial periods, which ascribed to terrestrial inputs, including lithogenic matter and dissolved nutrient, which also contribute to stimulating primary productivity. The results compared among the four cores in the WPWP since the MIS 9 indicate that in the western sector with the shallow thermocline, high primary productivity during the glacial periods was controlled by wind-induced surface water mixing, upwelling, and terrestrial inputs, while in the central and eastern sectors, the little different medium to low productivity might have been made by more intense upweil- ing driven by strong winds because the thicker warm surface water pool and the deeper thermocline prevented nutrient-bearing water from upwelling to upper water column even during the glacial times.

Reconstruction of Paleoceanography Significance in the Western Pacific and Atlantic Oceans during the Neogene Based on Calcareous Nannofossil Productivity and Size Variations, Related to the Global Tectonic Events

We investigated the calcareous nannofossils in the western Pacific and Bahama Bank of Caribbean Sea to reconstruct the paleoceanography and correlate with the global events. The absolute abundant of coccolith (number/g) are gradually increased from NN6 throughout NN19 Zone, while the relative abundance of Discoaster is decreased at Sites 782 in the western Pacific Ocean. The changes of the modal and maximum size of Reticulofenestra which are strongly reflected the collapse of sea surface stability, show four times in 8.8 Ma, 6.4 Ma, 5.4 Ma and 3.75 Ma at Site 782. On the basis of relationship between the changes of maximum sizes of Reticulofenestra and nutrient condition, these eutrophication events are clearly traceable to the western Pacific, Bahama Bank, northwestern Pacific Ocean and to the Indian Ocean. Two paleoceanographic events found in 8.8 Ma and 3.75 Ma are interpreted as change to high nutrient condition resulted in the intensification of Asian Monsoon and closure of Panama Isthmus.

Millennial-scale paleoceanography in Okinawa Trough during Late Quaternary period

Based on the analyses of foraminifer and accelerator mass spectrometer radiocarbon dating in DGKS9603 core from mid-Okinawa Trough close to bottom, oscillation curve, which expressed the relation between the surface water temperature and the depth, has been obtained by using foraminifer analysis and calculation of FP-12E transfer function. The whole core indicated seven cold phases and eight warm phases. Obvious expression of low