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1.
We report the occurrence of ferrobasalts recovered from the Central Indian Ocean Basin crust generated at the Southeast Indian
Ridge during a phase of moderate to fast spreading accretion (∼110–190 mm/yr, full rate).The rocks are rich in plagioclase,
FeO* (13–19%), and TiO2 (2.27–2.76%), poor in olivine and MgO (3.44–6.20%), and associated with topographic highs and increased amplitude magnetic
anomalies corresponding to chrons A25 and A24. We suggest that secon dary eruptions from ancient N-MORB magma, which may have
been trapped at a shallow depth in a horizon of neutral buoyancy, could have produced the ferrobasalts.
Received: 27 January 1998 / Revision received: 25 May 1998 相似文献
2.
A. F. Sazhin F. V. Sapozhnikov T. N. Rat’kova N. D. Romanova V. P. Shevchenko A. S. Filippov 《Oceanology》2011,51(2):295-305
The data on the supra-ice snow, ice, under-ice water, and benthic algal flora obtained in 2007–2008 by sampling in the estuary
of the Severnaya Dvina River are analyzed. The river ice and under-ice water in the estuarine zone and in the channel part
of the Severnaya Dvina differed greatly in the algal flora’s composition. The fresh water species never exceeded 8.6%, while
the ice algae composed 90–96% of the total ice inhabitants’ biomass. In the under-ice water, this value did not exceed 58–64%.
The bacteria in the ice composed not more than 2.5–10% of the total biomass, while, in the under-ice water, 36–49%. The shares
of ciliates (0.04%) and nematodes (0.005–1.6%) in the total biomass were negligible. In the estuarine zone, the ice was inhabited
mainly by nematodes (78% of the total biomass), while, in the river, their share decreased to 9%. The contribution of bacteria
was 15% in Dvina Bay and increased to 61% in the river. The importance of algae in the snow was minor: 7% of the total biomass
in the marine zone and 30% in the river region. High species diversity of the algal flora in the sandy and sandy-silty littoral
grounds was revealed. The values of the total biomass of the bottom algal flora (0.38 g C/m2) were only two to three times lower than the values revealed in similar habitats in the summer. The epipelithic forms (0.15
g C/m2) dominated, being represented by 46 species of algae (49%). The shares of epipsammonic (0.12 g C/m2) and planktonic (0.11 g C/m2) species were almost equal to each other: 25 and 22 species, respectively (27 and 24%). 相似文献
3.
P. R. Vogt J. Gardner K. Crane E. Sundvor F. Bowles G. Cherkashev 《Geo-Marine Letters》1999,19(1-2):97-110
Numerous small (50- to 300-m-diameter) strong-backscatter objects were imaged on the 1200- to 1350-m deep crest of Vestnesa
Ridge (Fram Strait) and along the 900- to 1000-m deep northeast margin of the Storegga slide valley. Ground-truthing identified
most of these objects as 2- to 10-m-deep pockmarks, developed within soft, acoustically stratified silty clays (typical wet
bulk density: 1400–1600 kg m-3; sound speed: 1480– 1505 m s-1; porosity, 65–75%; shear strength: 5–10 kPa; water content: 80–120%; and thermal conductivity: 0.8–0.9 W m-1 deg C-1 in the top 3 m). Gas wipeouts, enhanced reflectors, and reflector discontinuities indicate recent or ongoing activity, but
the absence of local heat flow anomalies suggests that any upward fluid flows are modest and/or local. 相似文献
4.
The first empirical orthogonal functions (EOF1s) of surface-air temperature fluctuations for Russia and its neighboring states
within the period 1950–2005 are analyzed. The spatial distribution of the EOF1, the first principal components (PC1s) of the
observed air temperature (averaged over the summer, July, December–March, and individual winter months), and their time variations
(including trend parameters, some spectral characteristics, and the quantitative indices of relation to circulation indices
(on the basis of multiple step-by-step regression)) are considered. Significant seasonal differences have been revealed: the
winter air-temperature fluctuations are characterized by a higher (when compared to summer) spatial coherence, especially
in the latitudinal direction. The EOF1 of the winter air temperature (averaged over December–March) describes its fluctuations
for almost all of Russia; in this case, no less than 70% of the PC1 variability is due to variations in several circulation
indices; the main contribution (60%) is made by both the North Atlantic Oscillation (NAO) and Scandinavian (SCAND) indices.
On the whole, over the periods 1951–2005 and 1971–2005, the NAO contribution exceeds the SCAND contribution to the winter
temperature variability; the NAO is associated with a more rapid increase in air temperature in 1968–1997 and with the 1971–2005
trend. In 1951–1970 the main contribution to air temperature fluctuations was made by SCAND; the SCAND contribution exceeds
the NAO contribution in the periods 1951–2005 and 1971–2005. The 1971–2005 and 1968–1997 temperature trends are completely
described by variations in the NAO (70%) and SCAND (30%) indices for January and February. 相似文献
5.
I. A. Nemirovskaya 《Oceanology》2010,50(5):716-728
Data are presented on the content of aliphatic and polycyclic aromatic hydrocarbons (AHC and PAH, respectively) in the interstitial
waters and bottom sediments of the Kara Sea compared to the distribution of the particulate matter and organic carbon. It
was found that the AHC concentrations within the water mass (16 μg/l on average) are mainly formed by natural processes. The
AHC distribution represents the variability of the hydrological and sedimentation processes in different regions of the sea.
The widest ranges of the concentrations were registered in the Ob Bay-Kara Sea section: in the water (10–310 μg/l for the
AHC and 0.4–7.2 ng/l for the PAH) and in the surface layer of the bottom sediments (8–42 μg/l for the AHC and 9–94 ng/g for
the PAH). The differentiation of the hydrocarbons (HC) in the different media follows the marginal filter’s regularities;
therefore, no oil and pyrogenic compounds are supplied to the open parts of the sea. In the sediment mass, the HC content
is determined by the variations in the oxidative conditions in the sediment and its material’s composition. 相似文献
6.
P. Jean-Baptiste A. Dapoigny M. Stievenard J. L. Charlou Y. Fouquet J. P. Donval J. M. Auzende 《Geo-Marine Letters》1997,17(3):213-219
Hydrothermal vent fields south of the Garret Fracture zone were sampled for the isotope composition of helium and oxygen
([18O]H2O/[16OH2O). The helium isotopes end-member (3He / 4He=8.3×R
a
and [4He]≈1.2–2.4×10-5 cm3 STP g-1) is quite similar to other known hydrothermal sites pointing to the homogeneous helium composition of the upper mantle. The
δ18O end-member value (δ18O≈0.5–0.6‰) confirms previous suggestions from other sites and from isotope modeling, that hydrothermal fluids are slightly
enriched in 18O relative to the ocean as a result of water–rock interactions at high temperature.
Received: 11 December 1995/Revision received: 20 December 1996 相似文献
7.
The considered area of the Russian sector of the Arctic Basin was characterized in August–September of 2008 by the wide horizontal
and vertical variability of the concentrations of dissolved and particulate organic matter (OM), as well as of its elemental
and biochemical composition. The concentration ranges amounted to 51.6–434 and 2.2–18.6 μM, respectively, for the dissolved
and particulate Corg; up to 1.9–30.2 μM for Norg; and up to 0.08–1.53 μM for Porg. The maximum values were characteristic for the Russian Arctic shelf. The analysis of the authors’ and published data showed
that a pronounced accumulation of OM, mainly in the dissolved form, took place in the Arctic Basin within the past 12 years.
The concentrations of dissolved OM were higher in the western sector of the Russian Arctic than those in the eastern sector.
The main biochemical components in all the waters constituting the Arctic Ocean are carbohydrates and lipids for dissolved
OM and proteins and carbohydrates for particulate matter. 相似文献
8.
Thomas Leipe Franz Tauber Henry Vallius Joonas Virtasalo Szymon U?cinowicz Nicole Kowalski Sven Hille Susanna Lindgren Tero Myllyvirta 《Geo-Marine Letters》2011,31(3):175-188
In this study, particulate organic carbon (POC) contents and their distribution pattern in surficial sediments of the Baltic
Sea are presented for 1,471 sampling stations. POC contents range from approx. 0.1% in shallow sandy areas up to 16% in deep
muddy basins (e.g. Gotland Basin). Some novel relationships were identified between sediment mass physical properties (dry
bulk density (DBD), grain size) and POC levels. Notably, the highest POC concentrations (about 10–17 mg cm–3) occur in sandy mud to mud (60–100% mud content) with intermediate POC contents of about 3–7% and DBDs of 0.1–0.4 g cm–3. Areas with this range in values seem to represent the optimum conditions for POC accumulation in the Baltic Sea. The maximum
POC contents (8–16%) are found in fluid mud of the central Baltic Sea characterized by extremely low DBDs (<0.1 g cm–3) and moderate POC concentrations (4–7 mg cm–3). Furthermore, sediment mass accumulation rates (MAR), based on 210Pb and 137Cs measurements and available for 303 sites of the Baltic Sea, were used for assessing the spatial distribution of POC burial
rates. Overall, these vary between 14 and 35 g m–2 year–1 in the mud depositional areas and, in total, at least 3.5 (±2.9) Mt POC are buried annually. Distribution patterns of POC
contents and burial rates are not identical for the central Baltic Sea because of the low MAR in this area. The presented
data characterize Baltic Sea sediments as an important sink for organic carbon. Regional differences in organic carbon deposition
can be explained by the origin and transport pathways of POC, as well as the environmental conditions prevailing at the seafloor
(morphology, currents, redox conditions). These findings can serve to improve budget calculations and modelling of the carbon
cycle in this large brackish-water marginal sea. 相似文献
9.
Hydrocarbon gases in sediments and mud breccia from the central and eastern part of the Mediterranean Ridge 总被引:3,自引:3,他引:0
Microbiologically produced hydrocarbon gases (HCGs) in normal pelagic sediments have lithologically controlled distribution
– their content increases sharply in organic-rich sapropels. Generally, the HCG content is low (<10000 nl/l), The amount of
heavy HCGs is high (up to 60%, unsaturated HCGs dominate the saturated ones, and ethylene is prevalent. The same features
were found in sediment and mud breccia from inactive mud volcanoes. Thermogenic HCG was determined in active mud volcanoes
and in a high salinity fluid vent. They are characterized by: high methane concentration, δ13C(CH4) =−37.1 to −57.8%, essential ethane contents (2–7%), absence of unsaturated HCG, and the prevalence of iso-over n-butane. 相似文献
10.
闽南及闽中近海常见鲨鳐类肝油的脂肪酸组成 总被引:5,自引:0,他引:5
闽南及闽中近海鲨鳐类肝油的脂肪酸组成相似,主要的脂肪酸包括16:0(14.9%~23.7%),18:0(5.3%~10.4%),18:1ω9(8.6%~16.9%),16:1(3.4%~7.5%),20:4ω6(3.8%~14.7%)和22:6ω3(10.7%~36.9%).22:6ω3在分析的所有种类(基齿鲨Hypoprion sp除外)均是含量最高的脂肪酸成分.可见,闽南及闽中近海鲨鳐类肝油是22:6ω3良好的来源.底层生活习性种类肝油ω6PUFA的含量高于中上层种类,而中上层生活习性种类肝油22:6ω3的含量以及ω3PUFA与ω6PUFA的比值则相对地高于底层种类,这种现象可能与它们各自的摄食习性有关. 相似文献
11.
M. V. Makarova A. V. Poberovskii K. N. Visheratin A. V. Polyakov 《Izvestiya Atmospheric and Oceanic Physics》2009,45(6):723-730
The results of measuring the methane content in the entire atmospheric thickness over the St. Petersburg region are given
for 1991–2007. It is shown that, within this period, the mean annual cycle of the total methane content is characterized by
its maximum values in December–January and its minimum values in June–August when the annual-cycle amplitude amounts to ∼3.6%.
In this case, the annual variations in the total methane content may differ significantly from the mean annual cycle obtained
in some years. A statistically significant linear trend of the total CH4 content has not been revealed for 1991–2007. The obtained values of the linear-trend index have opposite signs in the winter
and summer months (positive for January 0.6 ± 0.2%/year and February 0.4 ± 0.2%/year and negative for July 0.3 ± 0.2%/year
and August 0.2 ± 0.1%/year). This fact suggests the tendency for an increase in the amplitude of the annual cycle of the total
CH4 content. The results of a spectral analysis of a series of data on the total CH4 content show that, for 1991–2007, the following harmonics are pronounced with a confidence of 95%: 12 months (annual harmonic),
32 months (quasi-biennial oscillations), and 55 months (4.5 years), which are also pronounced in the series of meteorological
parameters and total ozone content. 相似文献
12.
The seasonal climatic circulation of the sea reconstructed on the basis of assimilation of new arrays of many-year average
hydrological data in a model is analyzed. Five layers are discovered in the structure of climatic currents in the sea in depth:
the surface Ekman layer (∼ 10 m), a layer with small vertical gradients of the kinetic energy (∼ 10–60 m), a layer with relatively
high vertical gradients of the kinetic energy (∼ 60–150 m), a layer with gradual decrease in the kinetic energy and intensification
(from 250–350 m) of the east cyclonic gyre and Batumi anticyclonic eddy (∼ 150–1000 m), and an abyssal layer characterized
by an almost barotropic velocity (∼ 1000–2000 m). The specific features of the seasonal evolution of currents at these depths
are investigated. It is shown that the key role in the formation of deep-water circulation of the sea is played by the south
east flow, east cyclonic gyre, and Batumi anticyclonic eddy.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 28–45, November–December, 2005. 相似文献
13.
14.
The temporal variability of the chemical composition of surface aerosol with particle diameters of 0.7–2 μm is analyzed. This
analysis is based on the results of measurements of infrared transmission spectra of aerosol samples collected with the use
of a cascade impactor at the Zvenigorod Scientific Station of the Institute of Atmospheric Physics (IAP) in 1999–2005. Seasonal
features of the aerosol chemical composition and its dependence on the particle size are revealed. The interdiurnal variability
of the aerosol composition depends on the season, and it manifests itself more strongly in winter and spring. Air-mass changes
lead to changes in the relation of sulfates and nitrates in the micron fraction of aerosol. The enrichment of samples in nitrates
is especially characteristic of the winter and spring seasons. Compounds containing the NO2 group are often met in the samples of aerosol with particle sizes of 0.7–1.3 μm during the cold time of the year. The estimates
of the optical thickness of micron aerosol in the sulfate absorption band are obtained, and optical-thickness variations of
some scales are detected. The quantitative characteristics of statistical relations between different chemical components
of aerosol inside individual fractions and between chemical components of the micron and submicron fractions are obtained
and analyzed. 相似文献
15.
A. K. Ambrosimov D. A. Ambrosimov P. N. Makkaveev Yu. R. Nalbandov L. E. Skibinskii P. V. Hlebopashev 《Oceanology》2009,49(5):630-642
Characteristics of different types of river drainage were obtained during studies of a polygon in the near-mouth part of the
Volga River in 2000–2003: “fast” (flowing through deep channels) and “slow” (that which passes through the littoral parts
of the delta (1–2 m)). The low current velocities (lower than in the channel waters by a factor of ten), the abundance of
water vegetation, and the strong heating of the waters lead to the high intensity of the biochemical processes. Therefore,
the chemical composition of the waters is subjected to significant transformation with intensity so high that it allows comparing
these regions with some sort of “bioreactor.” These changes influence the dissolved oxygen and various forms of carbon content. 相似文献
16.
Centropages tenuiremis is a species with a wide distribution range in disturbed coastal waters.However,due to a lack of dietary information,it remains unclear as to how they maintain such dominance in fluctuating conditions.In this study,C.tenuiremis was collected from the Daya Bay Nuclear Power Plant both in inlet and outfall regions at 06:00,12:00 and 18:00 on April 27,2011 and their in situ diet was analyzed using a PCR protocol targeting 18S ribosomal genes.Thirty-four species of prey organisms were identified totally,including Dinophyta,Baciliariophyta,Viridiplantae,Rhizaria,Apicomplexa,Chordata,Mollusca,Arthropoda and Fungi,indicating an obvious omnivorous feeding habit of C.tenuiremis.Centropages tenuiremis obviously exhibited spatial and temporal variations in diet composition.More plant prey(land plants and phytoplankton)were consumed in the morning(~50%),while more animal prey(metazoans and protozoans)were ingested at midday and night(60%–70%).Furthermore,a more diverse diet was detected in the outfall region(10–11 taxa),where the temperatures were relatively higher and more fluctuating,than in the control region(5–10 taxa).This finding indicated that C.tenuiremis could potentially expand its food spectrum under stressful condition.Specifically,C.tenuiremis exhibited phytoplankton preference(58.62%–67.64%)in the outfall region with a lower omnivory index(0.27–0.35)than in the control region(0.51–0.95).However,phytoplankton density was lower than that in the control region,suggesting a possible herbivorous tendency of C.tenuiremis under elevated temperatures to balance the energy acquirement and feeding effort.The flexible food choices of C.tenuiremis observed here could effectively buffer environmental fluctuations and might be an important survival strategy in coastal ecosystems. 相似文献
17.
Electron microprobe analysis was conducted on plagioclase from the plagioclase ultraphyric basalts(PUBs)erupted on the Southwest Indian Ridge(SWIR)(51°E) to investigate the geochemical changes in order to better understand the magmatic processes occurring under ultraslow spreading ridges and to provide insights into the thermal and dynamic regimes of the magmatic reservoirs and conduit systems. The phenocryst cores are generally calcic(An_(74–82)) and are depleted in FeO and MgO. Whereas the phenocryst rims(An_(67–71)) and the plagioclase in the groundmass(An_(58–63)) are more sodic and have higher FeO and MgO contents than the phenocryst cores. The crystallization temperatures of the phenocryst cores and the calculation of the equilibrium between the phenocrysts and the matrix suggest that the plagioclase cores are unlikely to have crystallized from the host basaltic melt, but are likely to have crystallized from a more calcic melt. The enrichment in incompatible elements(FeO and MgO), as well as the higher FeO/MgO ratios of the outermost phenocryst rims and the groundmass, are the result of plagioclase-melt disequilibrium diffusion during the short residence time in which the plagioclase crystallized. Our results indicate that an evolved melt replenishing under the SWIR(51°E) drives the eruption over a short period of time. 相似文献
18.
The quantitative distribution and grain-size composition of the suspended particulate matter (SPM) in the marginal filter
of the Severnaya Dvina River during the summer low-water periods of 2001–2005 were first analyzed in seawater on board of
the vessel immediately after its sampling (without preliminary treatment) using a Coulter counter. This analysis revealed
the main regularities in the transformation of the grain-size spectra at successive salinity steps of the marginal filter
as well as the boundaries between these steps based on the data obtained by direct complex studies of the SPM dispersion.
It is established that the water salinity is the main factor that controls the changes in the grain-size distribution and
the composition of the particulate matter in the marginal filter. The concentrations of the pelitic fraction and the salinity
demonstrate negative correlations between each other. It is shown that the areas characterized by the mass development of
phytoplankton are located along the outer boundary of the marginal filter (at the biological step), where the salinity amounts
to 23–24 psu. The content of the suspended forms of some chemical (lithogenic) elements and the Corg indicating the SPM’s genetic composition and their relations with the grain-size composition of the latter and the environments
are studied. 相似文献
19.
The role of the small-size (SF; 0.1–0.5 mm) and large-size (LF; 0.5–20.0 mm) fractions in the biomass and abundance of mesozooplankton
(0.1–20.0 mm) was assessed using the database of samples obtained during the cruises of RV Akvanavt in the northeastern Black Sea in November 2000 and October 2006. The mesozooplankton was collected by means of Juday nets
(37/50, filtering gauze 160 μm) and Niskin bottles in two areas: (1) the shelf and continental slope (30–1480 m depth) and
(2) the deep sea (depths of more than 1500 m). The plankton net was considerably less effective in collecting the SF of the
mesozooplankton (by a factor of 30–36) than the Niskin bottles. When comparing the SF and LF, we estimated the abundance and
biomass of the SF in the samples obtained with the Niskin bottles. The abundance of the SF in the deep-sea area was 2.5 times
lower compared to the shelf and continental slope, and the LF abundance was 5.0 times lower in the same way. The abundance
of the SF constituted 88% of the total mesozooplankton on the shelf and continental slope, and 78% in the deep-sea area. The
biomass of the SF was higher as well on the shelf and continental slope. Meroplankton played a significant role in the SF
zooplankton abundance (0.5 × 103 + 0.16 ind. m−3) in this area. The SF grazing impact was 10% of the total mesozooplankton grazing on the shelf and continental slope, and
17% in the deepsea area. Appendicularia and nauplii of copepods had the greatest contribution to the mesozooplankton grazing
among the SF group. 相似文献
20.
Gas hydrates and active mud volcanism on the South Shetland continental margin, Antarctic Peninsula 总被引:1,自引:0,他引:1
During the Antarctic summer of 2003–2004, new geophysical data were acquired from aboard the R/V OGS Explora in the BSR-rich area discovered in 1996–1997 along the South Shetland continental margin off the Antarctic Peninsula. The
objective of the research program, supported by the Italian National Antarctic Program (PNRA), was to verify the existence
of a potential gas hydrate reservoir and to reconstruct the tectonic setting of the margin, which probably controls the extent
and character of the diffused and discontinuous bottom simulating reflections. The new dataset, i.e. multibeam bathymetry,
seismic profiles (airgun and chirp), and two gravity cores analysed by computer-aided tomography as well as for gas composition
and content, clearly shows active mud volcanism sustained by hydrocarbon venting in the region: several vents, located mainly
close to mud volcanoes, were imaged during the cruise and their occurrence identified in the sediment samples. Mud volcanoes,
vents and recent slides border the gas hydrate reservoir discovered in 1996–1997. The cores are composed of stiff silty mud.
In core GC01, collected in the proximity of a mud volcano ridge, the following gases were identified (maximum contents in
brackets): methane (46 μg/kg), pentane (45), ethane (35), propane (34), hexane (29) and butane (28). In core GC02, collected
on the flank of the Vualt mud volcano, the corresponding data are methane (0 μg/kg), pentane (45), ethane (22), propane (0),
hexane (27) and butane (25). 相似文献