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原稿種別: 表紙
2009 年 86 巻 p.
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原稿種別: 付録等
2009 年 86 巻 p.
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原稿種別: 付録等
2009 年 86 巻 p.
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原稿種別: 付録等
2009 年 86 巻 p.
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原稿種別: 付録等
2009 年 86 巻 p.
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藤原 義弘
原稿種別: 本文
2009 年 86 巻 p.
1-2
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原稿種別: 目次
2009 年 86 巻 p.
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原稿種別: 付録等
2009 年 86 巻 p.
4-
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尾田 太良, 佐藤 時幸, 山崎 誠, 井龍 康文, 鈴木 紀毅
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2009 年 86 巻 p.
5-
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尾田 太良, 堂満 華子
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2009 年 86 巻 p.
6-11
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Neogoboquadrina group is dominant in modern planktic foraminiferal assemblages around Japan. As on of the most useful paleoceanographic proxies, the coiling direction of Neogloboquadrina pachyderma was widely used by many workers who have explained the behavior by temperature controlling the coiling direction in a single species. Morphologic characteristics and geographical distribution pattern, however, reflect the presence of two distinct species with opposite coiling direction preferences in the Northwest Pacific and Japan Sea. The Oyashio and cold waters in Japan Sea are inhabited by N. pachyderma, with dominantly sinistral shells associated with rarely dextral forms. On the other hand, the dominantly dextrally coiled Neogloboquadrina incompta, accompanied with rarely sinistral shells, thrives in (1) the Perturbed area located between the Oyashio and the Kuroshio fronts and (2) the transitional water formed by mixing of the Tsushima Warm Current with cold waters in Japan Sea. In addition, N. incompta is also common in the area off Ensyu-nada, where the cold water mass occurs associated with the meandering of the Kuroshio. Thus, N. pachyderma and N. incompta are the optimal markers of the cold waters and the transitional waters as well as the cold water mass in the Kuroshio domain, respectively. These two species contribute to reconstruct the paleoceanography in Northwest Pacific and Japan Sea.
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佐藤 時幸, 千代延 俊
原稿種別: 本文
2009 年 86 巻 p.
12-19
発行日: 2009/10/16
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We discuss in detail the Cenozoic paleoceanograpy related to the sea surface stratification, nutrient, and sea surface temperature based on the relationship between the coccolith maximum size and Discoaster abundance. The positive correlation was recognized between these parameters in the sequence from Eocene to Pliocene. As Discoaster is likely a lower photic species as like Florisphaera profunda, abundant occurrence of Discoaster indicates the sea surface stratification and the oligotrophic condition. On the basis of the relationship between coccolith maximum size and Discoaster abundance found in the Cenozoic sequence of ODP sites 807 and 731, the intervals of the late Eocene, NN3 to NN4 zones in the early Miocene, and NN6 to NN9 zones in the middle Miocene, are interpreted as the oligotrophic conditions.
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木元 克典
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2009 年 86 巻 p.
20-33
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Reconstruction of paleo-sea surface temperature (SST) and vertical water structure made great impacts on understanding the climatic systems in each oceans during the Neogene epoch. The Magnesium/Calcium ratio (Mg/Ca) in planktic foraminifers reflects the calcified temperature and was identified as a reliable tracer of SST. In this decade, this relatively new paleotemperature proxy has been refined by precise geochemical analytical techniques, and applied for the geological materials. Despite of such utilities in paleoceanography, it has been recognized that Mg/Ca incorporation in the shells of planktic foraminifers is altered by several factors: 1) carbonate dissolution, 2) diagenetic overprints after deposition, 3) heterogenetic distributions of Mg in the foraminiferal calcite, and 4) biologic factors in foraminiferal microenvironments. These factors are possibly impediment to apply the Mg/Ca ratio to high resolution paleoceanographic reconstruction studies. To explain these aspects of matter, I propose some approaches from geochemical and paleontological viewpoints to establish reliable calibration equation in the Northwestern Pacific, where there are no available calibration equations for paleothermometry at this time. The most fundamental thing is making consensuses for integration of geochemical procedures including chemical cleaning of foraminiferal shells and global standardization of analytical quality control. The second important thing is further studies of living planktic foraminiferal ecologies using plankton tows and sediment traps. Mutual efforts between these studies should give rise to establish reliable calibration equation in the Northwestern Pacific.
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千代延 俊
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2009 年 86 巻 p.
34-44
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Calcareous nannofossil assemblages and productivity at ODP Site 846 from the eastern equatorial Pacific and ODP Site 807 from the western equatorial Pacific were analyzed in order to reconstruct the climate evolution around the last 550,000 years. From Marine Isotope Stage (MIS) 14 to MIS 8, the nannofossil assemblage at Hole 846B exhibits a high relative abundance of small coccoliths. The assemblage in the coeval intervals at Holes 846B and 807A contains a high absolute abundance of coccoliths and a low relative abundance of warm water species. These characteristics of the tropical Pacific cores suggest an intensified trade wind and coastal upwelling system during MIS 14 through MIS 8. However, from boundary of MIS 8/7, a shift in calcareous nannofossil assemblage from a high to a low abundance of very small coccoliths is recorded at all holes, while the relative abundance of warm water species increased in the equatorial regions. From MIS 7 to MIS 1, very small coccoliths remained low in abundance, while warm water species continued to exhibit high values. These characteristics suggest that the strength of the trade winds was weakened during MIS 7 through to the present, as the upwelling system along the equator is controlled by the strength of the trade winds which linked Walker circulation during El Nino-like conditions. Thus, the modern hydrography in the equatorial Pacific Ocean formed after boundary of MIS 7/8, and the drastic shift in biological productivities and assemblages in the surface waters occurred suddenly during MIS 8, resulting from the change of Walker circulation and Hadley circulation strength.
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山本 正伸
原稿種別: 本文
2009 年 86 巻 p.
45-58
発行日: 2009/10/16
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We present a palaeoceanographic perspective of the North Pacific during the last two glacial cycles based on U^<K'>_<37>-derived palaeotemperature records from Japan and California margins. At the Japan margin, the sea surface temperature (SST) in the Kuroshio-Oyashio transition has varied in response to precessional cycle. At the California margin, SST has varied in response to ice volume changes, but the SST difference between inshore and offshore sites (ΔSST_<northeastern Pacific (NEP)>=SST_<ODP1014>-SST_<ODP1016>) has responded to precessional cycle. Comparison of ΔSST_<NEP> and the SST_<MD01-2421> of the central Japan margin revealed anti-phase variation; high ΔSST_<NEP> (indicating weakening of the California Current) corresponded to low SST at the Japan margin (indicating the southward displacement of the northwestern Pacific subarctic boundary and weakening of the Kuroshio Extension), and vice versa. This finding suggests that the intensity of the North Pacific subtropical gyre circulation has varied in response to precessional forcing.
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北 逸郎, 長谷川 英尚, 佐藤 時幸, 林 辰弥, 小島 淳
原稿種別: 本文
2009 年 86 巻 p.
59-66
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We investigated the relation between δ^<15>N_<org> values of organic matter and the number of nannofossil in marine sediments during a period from 300ka to 1300ka, using the core samples from ODP Hole 1006A, off Great Bahama Bank of the Caribbean Sea. The δ^<15>N_<org> values and the number of nannofossil (absolute abundance of coccoliths) fluctuate in the ranges of +0.1‰ to +5.8‰ and 1x10^8 to 30x10^8 specimens/g, respectively, with a clear positive correlation. As the number of nannofossil increases, δ^<15>N_<org> values become greater. These changes are closely linked to 100-ky and 41-ky variations in δ^<18>O_<planktonic> values of planktonic foraminifera (Globigerinoides ruber), reflecting mixing of surface water in the photic zone and bottom water brought about by the trade wind which became stronger during glacial period. δ^<15>N_<org> values (+0.1 to +5.8‰) of marine sediments from the Caribbean Sea fluctuate within a range lower than those (+4 to +10‰) from the Arabian Sea under the strong influence of upwelling during interglacial period. The difference in the fluctuation ranges of δ^<15>N_<org> values between these areas seems to reflect that in the amount of nitrate carried from bottom water to surface water under the influence of the trade wind and monsoon and its consumption rate by phytoplankton. These results corroborate the consideration that δ^<15>N_<org> values of marine sediments can be related directly to changes in productivity of phytoplankton.
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浅海 竜司
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2009 年 86 巻 p.
67-78
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To elucidate the "Quaternary" history of climate and ocean variability necessitates the use of paleoclimate proxy records from the tropical/subtropical regions that extend far beyond instrumental data currently obtainable. Fossil corals are one of the best archives for reconstructing thermal and hydrologic changes at the sea surface from the past. Massive Porites corals, forming annually-banded aragonite skeletons and growing rapidly, provide chronological control and allow high-resolution sampling. In particular, coupled determinations of coral Sr/Ca ratio and oxygen isotope can yield independent time-series of sea surface temperature and salinity, showing seasonal-to-decadal climatic variability such as El Nino/Southern Oscillation. This paper is a review of previous studies on paleoenvironmental analyses using fossil corals and suggests what needs to be addressed to develop coral paleoclimatology. Some previous studies indicated that estimates of sea surface temperature and salinity from coral Sr/Ca ratio and oxygen isotope records were biased to some degree due to seawater-temperature calibrations, changes in chemical composition of "Quaternary" seawater, diagenetic alteration, and/or vital effects. Further accurate evaluations of potential influences affecting coral geochemistry will enable more robust and high-fidelity reconstruction of tropical/subtropical sea surface conditions from the past.
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齋藤 めぐみ, 林 辰弥
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2009 年 86 巻 p.
79-86
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西田 民雄, 平野 弘道, 棚部 一成, 利光 誠一
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2009 年 86 巻 p.
87-88
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西 弘嗣, 酒井 治孝
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2009 年 86 巻 p.
89-90
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小笠原 憲四郎
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2009 年 86 巻 p.
91-92
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矢島 道子
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2009 年 86 巻 p.
93-
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西 弘嗣
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2009 年 86 巻 p.
93-94
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生形 貴男
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2009 年 86 巻 p.
94-
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西 弘嗣
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2009 年 86 巻 p.
95-
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矢島 道子
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2009 年 86 巻 p.
95-96
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原稿種別: 付録等
2009 年 86 巻 p.
97-100
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原稿種別: 付録等
2009 年 86 巻 p.
100-103
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原稿種別: 付録等
2009 年 86 巻 p.
103-
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原稿種別: 付録等
2009 年 86 巻 p.
103-
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原稿種別: 付録等
2009 年 86 巻 p.
104-
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2009 年 86 巻 p.
105-
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2009 年 86 巻 p.
105-
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2009 年 86 巻 p.
105-
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2009 年 86 巻 p.
106-
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2009 年 86 巻 p.
107-
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2009 年 86 巻 p.
App5-
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2009 年 86 巻 p.
App6-
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2009 年 86 巻 p.
App7-
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2009 年 86 巻 p.
App8-
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2009 年 86 巻 p.
App9-
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原稿種別: 表紙
2009 年 86 巻 p.
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原稿種別: 表紙
2009 年 86 巻 p.
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