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1.
T. Masuda T. Shibutani T. Ochiai S. Akagi H. Yamaguchi Y. Kugimiya N. Kimura T. Miyake 《Journal of Metamorphic Geology》2004,22(3):199-205
Evidence is presented of a lateral variation in differential stress during metamorphism along a regional metamorphic belt on the basis of the proportion of microboudinaged piemontite grains (p) in a quartz matrix in metacherts. It is proposed that p is a practical indicator of relative differential stress. Analysis of 123 metacherts from the 800 km long Sambagawa metamorphic belt, Japan, reveals that p‐values range from < 0.01 to 0.7 in this region. Most samples from Wakayama in the mid‐belt area have p‐values of 0.4–0.6, whereas those from western Shikoku have p‐values of < 0.1. This difference cannot be explained by variations in metamorphic temperature, and is instead attributed to a regional, lateral variation in differential stress during metamorphism. 相似文献
2.
Isao Sarashina Yoshiki Kunitomo Minoru Iijima Satoshi Chiba Kazuyoshi Endo 《Organic Geochemistry》2008,39(12):1742
Organic molecules such as proteins can be preserved in certain fossils. The bulk properties of fossil proteins of both vertebrates and invertebrates have been studied for over half a century. Named proteins have so far been identified, however, only in vertebrate fossils, such as collagen from mammoth bones. Using immunological assays, we examined 1500 year old fossils of the extinct land snail Mandarina luhuana from the Bonin islands for the presence of dermatopontin, a molluscan shell matrix protein. First, we examined the shell microstructure and mineralogy of the fossil shells using scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) in order to estimate the extent of diagenetic alteration. The results suggest that the original microstructure and mineralogy of the shells are preserved. Antiserum raised against the Type-1 dermatopontin fragment of the living land snail Euhadra brandtii showed significant immunological reactivity with the extracts from the fossil shells of M. luhuana. Immunological binding curves drawn for the shell extracts of extant M. aureola and the extinct M. luhuana confirmed the presence of dermatopontin in the fossil shells and provided an estimate that about 75–98% of the original dermatopontin was lost from the M. luhuana fossils. This is the first report of a named protein being identified in invertebrate fossils. 相似文献
3.
Masayuki Takahashi Sooji Shimura Yukuya Yamaguchi Yoshihiko Fujita 《Journal of Oceanography》1971,27(2):43-50
The photo-inhibition of phytoplankton photosynthesis at higher intensities was examined with a cultured marine diatom,Phaeodactylum tricornutum, and natural samples. The question was to determine whether photo-inhibition results from excretion of photosynthetic products from cell or from an actual decrease in photosynthetic rate.
P. tricornutum cultured at 15 klux showed very little photo-inhibition up to 70 klux, and, in the sample cultured at 1 klux, most marked photo-inhibition was observed in 3 hours experiment. Extracellular release was less than 30% of particulate fixation, and did not show any extreme increase to supplement photosynthesis depression at higher light intensities. When the photosynthesis was measured during 10 minutes, both samples showed no photo-inhibition. The photosynthesis by low light sample lost the linearity of time-course with prolonged exposure at high light intensity. Observed photo-inhibition, therefore, we explained with the actual decrease in photosynthetic rate. Similar photo-inhibition could be seen in marine phytoplankton samples concentrated by filtration. 相似文献
4.
Masayuki Takahashi Isao Koike Takashi Ishimaru Toshiro Saino Ken Furuya Yoshihiko Fujita Akihiko Hattori Shun-ei Ichimura 《Journal of Oceanography》1980,36(4):209-216
Water plumes, 20 km long or less, identified by low temperature, high salinity and high nutrient concentrations, were observed on the eastern side of Izu Islands where the Kuroshio Current or its branch flowed eastward. The T-S diagrams and the vertical profiles of oceanographic variables indicated that the water plumes resulted from the upwelling of subsurface water. A newly formed plume, characterized by a sharp temperature front and high nutrient concentrations, contained less chlorophyll than did old plumes. It is suggested that the upwelling plumes are maintained for a period long enough to allow luxuriant growth of phytoplankton. 相似文献
5.
Isao Hayashi 《Journal of Oceanography》1978,34(1):24-35
Macrobenthos were investigated at 77 stations on the level bottom of Maizuru Bay in the spring season in 1971. Among the animals collected in this survey, two animal groups,i.e. bivalves and polychaetes, predominated.Theora lubrica was the most predominant species, occupying 39 % of the total individuals collected. An apodan holothurian,Notomastus sp.,Prionospio ehlcrsi andLumbrineris longifolia also prevailed in number.According to the similarity of the composition of eight species common in the present area, the sampling stations were classified into four categories. As the stations belonging to each category are distributed in a peculiar portion of the bay, the bay can be divided into four areas, A–D, which are characterized as follows: Area A,Theora lubrica is highly predominant; Area B, an apodan holothurian and six common polychaetes (Notomastus sp.,Lumbrineris longifolia, Paraprionospio pinnata, Glycera chirori, Tharyx sp. andPolycirrus sp.) are relatively abundant; Area C, intermediate between Areas A and B; Area D, the above-mentioned eight species are scanty. These regional divisions of the bay correspond well with those based on the physico-chemical conditions on the bottom. Benthic feature of each area of the bay was discussed in connection with the bottom environment.Comparison of the present results with the previous data has revealed a considerable decrease of population density during the past 25 years in the area concerned. 相似文献
6.
Humitake Seki Hideshi Abe Yukuya Yamaguchi Shun-ei Ichimura 《Journal of Oceanography》1974,30(3):151-156
About 106 of total bacteria (direct microscopic count) or heterotrophic bacteria (colony count with Medium 2216E) and about 104 of petroleumlytic bacteria (oil-oxidizing bacteria) were enumerated per square centimeter of the surface of petroleum globules suspended in the topmost 10 meters of water from a station (22°00.2N, 125°51.9E) in the western North Pacific central water, where about 107 of total bacteria, about 103 of heterotrophic bacteria and about 10 of petroleumlytic bacteria were enumerated per liter of seawater. 相似文献
7.
Isao Naito 《Journal of Oceanography》1974,30(4):168-178
Secular variations of the mean pole and the z-term in the latitudinal vatiations are discussed geophysically in relation to oceanic motions on the large scale, particularly, to the variations of the Kuroshio system.It is shown that the large scale meanders of the Kuroshio occurred when the direction of displacement of the mean pole turned to the European continent from the North East Pacific and when the z-term changed from decrease to increase. The libration of the mean pole has connection with the zonal circulation of the oceanic mass and the secular variation of the z-term has connection with that of the meridional circulation. The large abrupt decrease in the z-term during 1955–1959 has close connection with the wellknown abnormal variation of sea surface temperature in the North Pacific during the same period.The structures of occurrence of the Kuroshio meanders in 1934 and 1969 may be different from those in 1953 and 1959, and the Kuroshio meander perhaps occurred after 1916 and existed during 2 or 3 years. Particularly the occurrence of the Kuroshio meander in 1959 may originate in the abrupt southward flow of oceanic mass in the Pacific.Except for some cases great earthquakes with magnitude of nearly 8 occurred near the Japan Trench and the Kurile-Kamchatka Trench about one year before the occurrences of the Kuroshio meander, and in the regions from the Alaska Peninsula to the Japan Islands great earthquakes occurred during the disappearance of the Kuroshio meander with a few exceptions.Existence of dynamical interactions between the ocean and the solid-earth may be suggested. 相似文献
8.
Santa Monica Bay is an open coastal embayment located directly seaward of Los Angeles, California. The Bay provides vital economic value through its water-dependent activities, such as swimming, diving, boating, and fishing. An increase from 100,000 residents in 1900 to 10 million in 2000 has imposed numerous environmental stressors on the Bay, including urbanization of the watershed. Pollutant discharges into the Bay increased throughout the early part of the century, but declined following passage of the Clean Water Act in 1972. Since that time, the predominant source of pollutant inputs has changed from point sources to non-point urban runoff. To assess how present-day and historical pollution interact to affect the environmental quality of Santa Monica Bay, three organizations collaborated on a multi-disciplinary study in 1997, towards which this volume is focused. This paper details the temporal patterns of anthropogenic influence on Santa Monica Bay to provide context for the papers that follow. 相似文献
9.
Abstract. Chemistry and sulfur isotopes are analyzed for a series of rocks in the chert‐dominant sequence around the stratiform manganese ore deposit of the Noda‐Tamagawa mine in the northern Kitakami Terrane, northeast Japan. The sequence is litholog‐ically classified into six units in ascending order: lower bedded chert, lower black shale, massive chert, manganese ore, upper black shale, and upper bedded chert. The rocks around the manganese ore deposit exhibit anomalous enrichment in Ni (max. 337 ppm), Zn (102) and U (30) in the upper part of lower bedded chert, Mo (122), Tl (79) and Pb (33) in the lower black shale, MnO, Cu (786) and Co (62) in the manganese ore, and As (247) and Sb (17) in the upper black shale. The aluminum‐normalized profiles reveal zonal enrichment of redox‐sensitive elements around the manganese bed: Zn‐Ni‐Fe‐Mo‐U(‐Co), Tl‐Pb(‐Mo), Mn‐Fe‐Cu‐V‐Cr‐Co(‐Zn) and As‐Sb in ascending order. The uppermost part of the lower bedded chert and black shale exhibit negative Ce/Ce* values, whereas the massive chert, manganese ore and lower part of the upper bedded chert display positive values. The isotopic δ34S values are 0±6 % in the lower part of the lower bedded chert, ‐19 to ‐42 % in the upper part of the lower bedded chert, ‐36 to ‐42 % in the lower black shale, ‐28 to ‐35 % in the massive chert, manganese ore and upper black shale, and ‐23±5 % in the upper bedded chert. Thus, there is a marked negative shift in δ34S values in the lower bedded chert, and an upward‐increasing trend in δ34S through the manganese ore horizon. The present data provide evidence for a change in the paleoceanographic environmental resulting from inflow of oxic deepwater into the stagnant anoxic ocean floor below the manganese ore horizon. This event is likely to have triggered the precipitation of manganese oxyhydroxides. The redistribution of redox‐sensitive elements through the formation of metalliferous black shale and manganese carbonate ore may have occurred in association with bacterial decomposition of organic matter during early diagenesis of initial manganese oxyhydroxides. 相似文献
10.
We have undertaken petrologic and SHRIMP U-Th-Pb isotopic studies on zircons from basaltic eucrites (Yamato [Y]-75011, Y-792510, Asuka [A]-881388, A-881467 and Padvarninkai) with different thermal and shock histories. Eucritic zircons are associated with ilmenite in most cases and have subhedral shapes in unmetamorphosed and metamorphosed eucrites. Some zircons in highly metamorphosed eucrites with granulitic texture occur alone in pyroxene, and typically have rounded to subrounded shapes due to recrystallization. Superchondritic Zr/Hf ratios of eucritic zircons indicate that they crystallized from incompatible element-rich melts after crystallization of ilmenite. Concentrations of uranium and thorium in zircons in the unmetamorphosed eucrite Y-75011 are higher than those in metamorphosed eucrites.The U-Pb systems of eucritic zircons are almost concordant but some zircon grains show reverse discordance. Radiogenic lead-loss up to 48% from zircons is observed in the shock-melted eucrite Padvarninkai. The 207Pb-206Pb ages of zircon in Y-75011 (4550 ± 9 Ma, n = 5) are nearly identical, within analytical uncertainty, to the ages of zircons from the metamorphosed eucrite Y-792510 (4545 ± 15 Ma, n = 13), the highly metamorphosed eucrites A-881388 (4555 ± 54 Ma, n = 5) and A-881467 (4558 ± 13 Ma, n = 8), and the shock-melted eucrite Padvarninkai (4555 ± 13 Ma, n = 18). The averaged 207Pb-206Pb age of zircon from five eucrites analyzed in this study is 4554 ± 7 Ma (95% confidence limits, n = 49), indistinguishable from the averaged U-Pb age (4552 ± 9 Ma) of the same samples. Because of the high closure temperature of lead in zircon (Tclosure = ∼1050°C with a cooling rate of 0.2°C/yr), the 207Pb-206Pb ages of eucritic zircon do not represent metamorphic ages but crystallization ages of extrusive lavas.This fact strongly suggests that volcanism of the eucrite parent body occurred at a very early stage of the Solar System history, 7-20 Ma after CAI formation (4567.2 ± 0.6 Ma), thus basaltic eucrites crystallized from parental magmas within a short interval following the differentiation of their parent body. The U-Pb ages of eucritic zircons are older than the U-Pb, Sm-Nd and Rb-Sr ages of some basaltic eucrites, which is consistent with differences in closure temperatures of each isotopic system, and suggests that thermal and shock metamorphism affected the isotopic systems of pyroxene, plagioclase and phosphates. 相似文献