Radium and lead-210 in marine barite     

D.V Borole  B.L.K Somayajulu 《Marine Chemistry》1977,5(3):291-296

Measurements of ²²⁶Ra and ²¹⁰Pb in barite samples separated from different depths of a piston core from the eastern equatorial Pacific are reported. ²²⁶Ra is enriched in the barite as would be expected from the chemistries of Ra and Ba; the ${}^{226}\text{Ra}\text{Ba}$ ratio centers around 1.5 · 10¹⁴ atoms/mole. The results suggest that barite is concentrating Ra at a rate comparable to its decay rate, viz. 5.78 · 10^?3 yr^?1. The gross ²¹⁰Pb depletion with respect to ²²⁶Ra is indicative of ²²²Rn loss due to the smallness of the barite crystals.  相似文献   

Marine geology in the environs of Bouvet Island and the South Atlantic triple juction     

G. Leonard Johnson  Richard N. Hey  Allen Lowrie 《Marine Geophysical Researches》1973,2(1):23-36

It is suggested that Bouvet Island is the surface manifestation of a mantle plume which has resulted in the creation of a chain of seamounts in the South Atlantic and a general shoaling of the region.The strike of two newly defined large fracture zones borth and south of the Bouvet Island pedestal have been utilized to determine a pole of rotation at 12.5°S, 12.5°W for the Africa-Antarctica motion. A pole at 75°S, 13°E has been calculated for the South America-Antarctica motion. At the triple junction the South America-Africa relative motion is 3.3 cm yr^-1 (whole rate) at 075°. The Africa-Antarctica motion is 1.7 cm yr^-1 at 065° and the South America-Antarctica motion is 1.6 cm yr^-1 at 085.  相似文献   

Water colour index of the Guinean sector of the Atlantic Ocean     

V. L. Vladimirov  B. Diallo  O. V. Martynov  M. K. H. Salle 《Physical Oceanography》1990,1(4):321-324

The distribution of the colour index is considered in the region bounded by 8–11°N and 13°30–18°30W based on the results of measurements made on board vessels of the Marine Hydrophysical Institute of the Ukrainian SSR Academy of Sciences (MHI) in 1977–1985. Mean values and statistical characteristics are calculated for the colour index variability over one-degree squares. A map of its multi-yearly average distribution is plotted.Translated by M. M. Trufanov.  相似文献   

A stochastic model of the atmospheric precipitation in the coastal zone of the Tropical Atlantic     

G. S. Dvoryaninov  A. V. Prusov  M. V. Shokurov 《Physical Oceanography》1991,2(1):29-43

A stochastic prognostic model of the atmospheric precipitation in the tropical area of the Atlantic Ocean is developed on the basis of a large data array. The data represent a series of monthly precipitation rates for 31 towns in the Republic of Guinea covering a period of 35–64 years as well as satellite data on the meridional displacement of the Intertropical Convergence Zone during 11 years. The model takes into account major regularities of the tropical precipitation: their impulsive periodic regime, trends, and the modulation of the stochastic component by the determined variability.Translated by Mikhai M. Trufanov.  相似文献   

Four-dimensional analysis of the variability of hydrophysical fields in the tropical atlantic and on the shelf of guinea     

I. E. Timchenko  V. O. Belozersky  E. M. Igumnova 《Physical Oceanography》1994,5(3):211-220

The problem of monitoring of the mesoscale variability of hydrophysical fields in the shelf zone is considered. The usefulness of the data available in regional information centres is discussed. The possibility of monitoring the dynamics of the oceanic fields in the tropical Atlantic encompassing separate observation sites is demonstrated using the oceanographic databank of the scientific research centre (CERESCOR) in Conakry-Rogbane as an example. The results of assimilation of the hydrophysical survey data derived on the shelf in a telescopic model of the region are given.Translated by Mikhail M. Trufanov.  相似文献   

Three Kings Ridge: a west-facing arc     

L. W. Kroenke  J. V. Eade 《Geo-Marine Letters》1982,2(1-2):5-10

The Three Kings Ridge has been described as a remnant arc or an east-facing arc on the western side of the South Fiji Basin under which symmetric South Fiji Basin magnetic anomaly lineations have been lost. We find evidence of neither arc-trench morphology on the eastern flank of the ridge nor collision tectonism within the adjacent South Fiji Basin that might have obliterated it. We believe there is room for the missing magnetic lineations within the South Fiji Basin and we recognize the distinctive island-arc morphology characteristic of a west-facing arc on the western flank of the Three Kings Ridge. Our interpretation requires that arc volcanism postdated formation of much of the South Fiji Basin and that oceanic lithosphere from the adjacent Norfolk Basin must have been subducted beneath the west-facing Three Kings Arc.  相似文献   

Upper Jurassic overlapping-fans slope-apron system: Brae oilfield,North Sea     

Dorrik A. V. Stow 《Geo-Marine Letters》1983,3(2-4):217-222

The Brae oilfield reservoir in the North Sea comprises Upper Jurassic resedimented conglomerates and sandstones interbedded with organic-rich silstone and mudstone thin-bedded turbidites. The system represents a series of small overlapping fans that form a thick (300 m) slope-apron accumulation of sediments deposited in a narrow (<10 km wide) belt along an active fault zone. The complex lateral and vertical distribution of facies was due mainly to variable tectonic activity, and partly also to sediment supply and sea-level changes.  相似文献   

Reynolds stress and TKE production in an estuary with a tidal bore   总被引：4，自引：0，他引：4  

J. H. Simpson  N. R. Fisher  P. Wiles 《Estuarine, Coastal and Shelf Science》2004,60(4):619-627

We report new measurements of the turbulent properties of the flow in a tidally energetic estuarine channel of almost uniform cross-section. A high-frequency (1.2 MHz), bottom-mounted Acoustic Doppler Current Profiler (ADCP) has been used to observe the velocity field at a sampling rate of 10 Hz in parallel with measurements of the surface elevation by tide gauges. Our data have been analysed using the Variance Method to determine turbulent kinetic energy (TKE), shear stress and TKE production over the tidal cycle with a time resolution of 60 s. During the highly energetic but brief flood period, when the surface axial velocity reaches 2 m s⁻¹, we observed large values of stress (>2 Pa) and shear production (5 W m⁻³). TKE is also input through the release of energy in the bore itself which results in a brief but intense injection of energy at the bore front with large transient TKE levels (100 J m⁻³). Subsequent input by shear production maintains TKE levels which are generally lower (20 J m⁻³) than the strong peak associated with the bore for the rest of the flood. On the ebb, the flow is relatively tranquil with maximum speeds 0.5 m s⁻¹ and peak TKE production rates of 0.1 W m⁻³.The flow and elevation data have also been used to estimate the energy fluxes into and out of the estuary. Short (1 h), intense energy inputs (8 MW at springs) on the flood flow are largely balanced by longer, less intense seaward energy flow on the ebb. The net energy input is found to be 0.1 MW at springs which is consistent with estimates of upstream dissipation. Peak dissipation in the bore itself may exceed the mean energy input but it is active only for a small fraction of the tidal cycle and its average contribution does not exceed 12% of total dissipation.  相似文献   

Mineralogical and geochemical features of authigenic carbonates on seepings and hydrothermal fields (By the examples of the Black Sea reefs and the mounds of the lost city field)     

A. Yu. Lein  O. Yu. Bogdanova  Yu. A. Bogdanov  L. I. Magazina 《Oceanology》2007,47(4):537-553

Two genetically different types of authigenic carbonate mounds are studied: those within an active hydrothermal field related to serpentinite protrusions in the zone of intersection of a transform fracture zone and the Mid-Atlantic Ridge, and those in an active field of methane seepings in the Dnieper canyon of the Black sea. The general geochemical conditions under which authigenic carbonate formation occurs in the two fields considered were found. They include the presence of reduced H₂S, H₂, and CH₄ gases at the absence of free oxygen; the high alkalinity of the waters participating in the carbonate formation; the similarity of the textural and structural features of authigenic aragonite, which represents the initial mineral of the carbonate matter of the mounds; the paragenesis of aragonite with sulfide minerals; and the close relation of carbonate mounds with communities of sulfate-reducing and methane-oxidizing microorganisms. A new mechanism of formation of hydrothermal authigenic carbonates is suggested; it implies their microbial sulfate reduction over the hydrogen of the fluid in the subsurface zone (biosphere) of mixing between the hydrothermal solution and the adjacent seawater.  相似文献   

Experimental method for quantifying resistance to the opening of netting panels   总被引：1，自引：0，他引：1  

Sala  A.; O'Neill  F. G.; Buglioni  G.; Lucchetti  A.; Palumbo  V.; Fryer  R. J. 《ICES Journal of Marine Science》2007,64(8):1573-1578

  相似文献