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排序方式: 共有469条查询结果,搜索用时 15 毫秒
1.
Takuya Matsumoto Masahiko Honda Ian McDougall Igor Yatsevich Suzanne Y. O'Reilly 《地学学报》2004,16(1):23-26
Using a Rayleigh distillation fractionation model, we calculate that the maximum isotope fractionation potentially achievable is less than 5% during the early stages of gas release from a sample. Our calculation corrects the erroneous conclusions of Gautheron and Moreira (2003), who re‐interpreted the plume‐like neon isotopic compositions found in metasomatic apatite from a south‐eastern Australian xenolith (Matsumoto et al., 1997) to be the result of Rayleigh‐type isotope fractionation of originally MORB‐type neon during stepheating gas extraction. We stress that the modelling of neon isotopic fractionation by Gautheron and Moreira (2003) is incorrect, and that the finding of a plume‐like neon isotopic composition in the apatite by Matsumoto et al. (1997) remains a quite valid and robust conclusion. 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.
Sedimentation process of fine-grained terrigenous red soils was observed on the seafloor by coral reefs near an estuary using a paired mooring of turbidity meter and sediment trap or a mooring of sediment trap and current meter. Silty clays contained in the bottom calcareous sands were mainly resuspended and trapped in both surface and bottom layer traps, at noncatastrophic normal sedimentation periods. In addition, silty clays were supplied to this mooring site by inflowing river. Turbidity and the flux rate determined by sediment traps show certain relationship accompanied with the coefficient, which is changed by precipitation, current, and other conditions. Resuspension process caused by a typhoon was recorded as both core sequence of sediment trap and time-series data of bottom current. Maximum velocity of 49.5 cm/s was recorded from bottom currents resulting from the passing of attyphoon at the mooring site. A graded sand layer is interbedded in dark-gray, silty clay and considered to be a resuspended sediment resulting from the passing of the typhoon. Flux of the resuspended sediments by the typhoon was estimated from this core sequence and compared to the flux observed at the normal sedimentation. 相似文献
4.
Decadal variability of subsurface temperature in the North Pacific has been investigated. Two dominant regions were found;
the central subarctic region (CSa) and the north-eastern subtropical region (NESt). In CSa, cooling (warming) of wintertime
subsurface temperature corresponds to the large (small) temperature gradient and southward (northward) shift of subsurface
temperature front, associated with the increase (decrease) of positive wind stress curl and the southward (northward) shift
of curl τ zero line with 2 years delay. It is suggested that the relocation of subtropical-subarctic boundary plays an important
role. In NESt, importance of heat flux through the sea surface and heat divergence in the Ekman layer is also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
The effects of the reed,Phragmites australis (Trin.), on substratum grain-size distribution in a salt marsh 总被引:1,自引:0,他引:1
The effects of the reed,Phragmites australis (Trin.), growing in a brackish water lagoon, were studied in relation to the grain-size distribution of the substratum. At the salt marshes near the lagoon, the upper soils from the surface to a depth of 20 cm contained much silt-clay. These fine particles were found to be transferred from the river and fish ponds near the lagoon, and to be deposited when the tidal rhythm changed, that is, when the water current stopped. In addition, the fine particles, which were deposited on the bottom of the lagoon adjacent to the marshes, became resuspended as a result of wind-caused wave action, and then were transported and redeposited in the salt marshes at the flood tide. Since the reeds further reduced the water current caused by the waves and tide, the reeds were thought to promote redeposition of the resuspended matter. In other words, the reeds were considered to protect deposited and redeposited particles such as silt and clay from resuspension as a result of wave action by reducing the effects of waves and wind. These processes suggested that silt-clay will become abundant in the substratum of the salt marsh adjacent to the lagoon. 相似文献
6.
Satoshi Yamamoto 《Journal of Oceanography》1984,40(1):80-89
The pattern of distribution of detrital mineral grains in the water column was investigated at three stations in the western Pacific during July through August of 1979. The sedimentation of detrital mineral grains was also studied using piston cores from two sites adjacent to the three stations. The concentration of suspended detrital mineral grains in the subsurface waters becomes lower with increasing distance from the land, and shows a prominent peak in the intermediate zone of the water column. The sharp increase in water density and viscosity in the pycnocline in the intermediate zone decreases the settling velocity of grains, and may result in the accumulation of falling grains in the intermediate layer. Proportion of detrital mineral grains to organic remains in the sediment was more than two orders of magnitude larger than in the overlying water column, and reasons for this are briefly discussed. 相似文献
7.
Tetsuo Yanagi Koji Ishikawa Koh-ichi Inoue Satoshi Susami 《Journal of Oceanography》1995,51(2):225-238
The detailed flow structure around a tical front in Hiuchi-Nada, Japan was observed with the use of ADCP (Acoustic Doppler Current Profiler). The surface convergence region is observed at the transition zone between vertically well mixed area and the stratified area. The surface divergence regions exist next to the surface convergence region. The strong downward current is estimated in the middle layer just below the surface convergence region. The maximum surface convergence and the maximum downward velocity in the middle layer are 1.0×10–4 s–1 and 0.12 cm s–1, respectively. 相似文献
8.
Matsumoto Takeshi Goslin Jean Lagabrielle Yves Ruellan Etienne Tanahashi Manabu 《Marine Geophysical Researches》1997,19(1):37-53
A surface ship gravity survey was carried out in the northern part of the North Fiji Basin during the NOFI cruise by the R/V l'Atalante in August-September, 1994. The two ridges inside the study area, the South Pandora Ridge and the Tripartite Ridge, present different structures and states of isostatic equilibrium in terms of gravity anomaly and its tectonic implications. The former is supported by a restoring force of an imaginary elastic plate in the crust and the latter by the Airy type isostasy. These characteristics can be derived from the difference in magmatic activity, as influenced by the difference in lithospheric structure. The latter is characterised by greater active magmatism and hydrothermalism underneath the ridge than the former. Such a difference in the magmatic activity and the horizontal scale of the shallow subsurface structure is derived from the difference in the stiffness or viscosity of the lithosphere beneath the two ridges. 相似文献
9.
Seasonal Variability of Near-Surface Heat Budget of Selected Oceanic Areas in the North Tropical Indian Ocean 总被引:1,自引:0,他引:1
The results obtained from an Ocean General Circulation Model (OGCM), the Modular Ocean Model 2.2, forced with the National
Center for Environmental Prediction/National Center for Atmospheric Research reanalysis data, and observational data have
been utilized to document the climatological seasonal cycle of the upper ocean response in the Tropical Indian Ocean. We address
the various roles played by the net surface heat flux and the local and remote ocean dynamics for the seasonal variation of
near-surface heat budget in the Tropical Indian Ocean. The investigation is based in seven selected boxes in the Arabian Sea,
Bay of Bengal and the Equatorial Indian Ocean. The changes of basin-wide heat budget of ocean process in the Arabian Sea and
the Western Equatorial Indian Ocean show an annual cycle, whereas those in the Bay of Bengal and the Eastern Equatorial Indian
Ocean show a semi-annual cycle. The time tendency of heat budget in the Arabian Sea depends on both the net surface heat flux
and ocean dynamics while on the other hand, that in the Bay of Bengal depends mainly on the net surface flux. However, it
has been found that the changes of heat budget are very different between western and eastern regional sea areas in the Arabian
Sea and the Bay of Bengal, respectively. This difference depends on seasonal variations of the different local wind forcing
and the different ocean dynamics associated with ocean eddies and Kelvin and Rossby waves in each regional sea areas. We also
discuss the comparison and the connection for the seasonal variation of near-surface heat budget among their regional sea
areas.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Jean-Marie Auzende Eiichi Honza Xavier Boespflug Satendra Deo Jean-Philippe Eissen Jun Hashimoto Philippe Huchon Junichiro Ishibashi Yo Iwabuchi Philip Jarvis Masato Joshima Kiyoyuki Kisimoto Yasuto Kuwahara Yves Lafoy Tsuyoshi Matsumoto Jean-Pierre Maze Kiyohiko Mitsuzawa Hiroyasu Monma Takeshi Naganuma Yukihiro Nojiri Suguru Ohta Kiyoshi Otsuka Yoshihisa Okuda Hélène Ondreas Akira Otsuki Etienne Ruellan Myriam Sibuet Manabu Tanahashi Takeo Tanaka Tetsuro Urabe 《Marine Geophysical Researches》1990,12(4):269-283
The aim of the Japanese-French Kaiyo 87 cruise was the study of the spreading axis in the North Fiji Basin (SW Pacific). A
Seabeam and geophysical survey allowed us to define the detailed structure of the active NS spreading axis between 16° and
22° S and its relationships with the left lateral motion of the North Fiji Fracture Zone. Between 21° S and 18°10′ S, the
spreading axis trends NS. From 18°10 S to 16°40 S the orientation of the spreading axis changes from NS to 015°. North of
16°40′ S the spreading axis trends 160°. These two 015° and 160° branches converge with the left lateral North Fiji fracture
zone around 16°40′ S to define an RRFZ triple junction. Water sampling, dredging and photo TV deep towing give new information
concerning the hydrothermal activity along the spreading axis. The discovery of hydrothermal deposits associated with living
communities confirms this activity. 相似文献