GLOBAL MAPPING OF STABLE ISOTOPES AND TRACE ELEMENTS IN THE PLANKTONIC FORAMINIFERA AND ITS APPLICATION TO PALEOCEANOGRAPHY

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Stable carbon and oxygen isotopes of foraminiferal and coral skeletons and molluscs have provided detailed information about the linkage between biological calcification processes and surrounding environments. Globigerinoides ruber has recently received much attention for paleoceanography in the subtropical and tropical ocean. G. ruber has two morphotypes (G. ruber s.s. and G. ruber s.l.) : G. ruber s.s. and s.l. are dwelling at the surface layer and at the deeper depth in the surface water, respectively. In order to establish a proxy for the quantitative reconstruction of sea surface temperature, oxygen and carbon isotopes were analyzed in G. ruber collected at 30 degree north, 175 degree east in the Pacific. The mean difference of delta 18 oxygen values between both morphotypes was 0.25‰ in August-October, corresponding to 1 degree C difference in water temperature. Together with foraminiferal assemblage, delta 18 oxygen values of two morphotypes of G. ruberー can be a good proxy for … More quantitative reconstruction of vertical seawater temperature in the surface ocean. For the further development, stable isotopes and contents of trace elements in the biogenic calcite and aragonite were analyzed in order to develop the proxy for the environments and conduct higher level of environmental reconstruction. Also we analyzed the oxygen isotopic values of molluscs, which suggest that the pearls were produced around 23-24 degree C, mainly in June to early July, which is consistent with their occurrence in the field. Therefore the pearls were produced under or close to isotopic equilibrium conditions. Furthermore, we collected sediment core MD01-2409 (41degree north, 141 degree east) at 975 m water depth on the continental margin off the northern Japan. Oxygen isotopic values of N. pachyderma (left) decrease only 1.5 ‰ from LGM to Holocene. If oxygen isotopic values of seawater decreased 1.0 ‰ because of ice sheet, the seawater temperature at the site increased only 2.5 degree. It suggests that the water temperature changes of the Oyashio water, at the depth 100-200 m, was lower than that of the water mass influenced by the Oyashio and the Tsugaru Warm Current at the depth shallower than 10 m. Less