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691.
M.E. vinogradov E.A. Shushkina V.I. Vedernikov N.P. Nezlin V.I. Gagarin 《Deep Sea Research Part II: Topical Studies in Oceanography》1997,44(9-10)
Data collected from 20 years of observations by the P. P. Shirshov Institute of Oceanology (about 250 comprehensive ecosystem stations) are summarized to evaluate the primary production and biomass of the principal groups of plankton in the Pacific Ocean. The stations were classified into geographical regions according to satellite determined criteria. The areas of these regions were evaluated according to CZCS data from 1978 to 1986. The total value of primary production was evaluated as 26·9 Gt C year−1. Taking the “bottle effect” correction into account, this value may be as high as 45.6 Gt C year−1. Total biomass values of phytoplankton (134 Mt C), bacteria (86 Mt C), protozoa (26 Mt C) and mesoplankton (184 Mt C) were also calculated. Seasonal variabilities of all these values were remarkably insignificant. 相似文献
692.
Water velocity and density profiles were obtained in late-spring and late-winter to document reversing mean circulation patterns at the entrance to a semiarid coastal lagoon, the Bay of Guaymas, in the Gulf of California, Mexico. The lagoon is shallow but the bathymetry at its entrance is similar to that of temperate estuaries with an asymmetrically positioned channel flanked by shoals. In late-spring the mean circulation at the entrance to the lagoon was driven by horizontal density gradients that arose from excess evaporation over precipitation in the area as evidenced by water density profiles. The lagoon exported relatively warm (25·8 °C) and salty (36·2) water to the Gulf of California through the channel. This export was consistent with inverse estuarine circulation influenced by bathymetry. In late-winter, the circulation at the entrance of the lagoon was mostly driven by wind stress that blew from the northwest, roughly along the main axis of the lagoon. Relatively cool (16·0) °C) and less salty (35·1) water from the Gulf of California was driven into the lagoon within the channel. Density gradients inside the lagoon seem to have played a secondary role in driving the circulation. The late-winter circulation was then estuarine-like, with outflow in the direction of the wind over the shallow areas and a compensatory inflow appearing in the channel as expected from theory of wind-driven flow over bathymetry. This estuarine-like circulation developed despite the lack of measurable freshwater input to the lagoon and was the opposite to that observed in late-spring. These observations then document a reversal in water exchange patterns from season to season in a semiarid coastal lagoon. The observations also constitute one of the few reported examples of flow over shoals driven in the same direction as the wind stress with a compensatory flow in the channel. 相似文献
693.
Analysis of microbiological and chitinase activities relative to the white shrimpPenaeus setiferus, and its chitinoclastic endosymbionts, have demonstrated the relevance of total chitinolytic processes in penaeid biology. Microorganisms may serve as a direct source of nutrients for the animal as well as in the elaboration of extracellularin situ chitinase enzymes. The enzyme produced by the predominant gut bacteria,Beneckea neptuna, is a moderately actively inducible chitinase while the shrimp has an indigenous constitutive chitinase and chitobiase system. Factors of temperature, pH, ion inhibition and reducing sugar ratios have been compared for the bacterial and animal enzymes. This dual enzyme system suggests that metabolic chitin transformation may play a vital role in crustacean metabolism. 相似文献
694.
A high-resolution seismic survey covering more than 2,000 km2 has revealed the processes responsible for the slope morphology and channel sedimentation across the forearc slope-basin
of the Kurile Arc–NE Japan Arc collision zone, offshore from Tokachi (Hokkaido, Japan). The dominant slope contours parallel
the trench but, in the middle and lower reaches of the southern slope, contours are convex-shaped with an offshore trend.
This sector of the slope is traversed diagonally by the Hiroo submarine channel. The offshore-trending convex contours and
the channel course have developed through the interplay of tectonic and sedimentary processes, including the development of
anticlines, anticline-induced lobe sedimentation and channel avulsion. In its upper reaches, the channel is restricted by
a topographic low associated with NNW–SSE-trending anticlines which developed within the upper and middle slope sectors during
late Miocene uplift. The uplift timing and trend of these anticlines indicate that they resulted from collision, the channel
sedimentology and slope morphology of the middle and lower slopes having been influenced by Pliocene uplift of NE–SW-trending
anticlines. The trends of these anticlines parallel those of the Kurile Trench. The Pliocene and early Pleistocene strata
of the middle and lower slopes consist of ponded lobe sediments deposited along the palaeo-Hiroo submarine channel on the
landward side of the anticlines. As a lobe pile accumulated, the channel thalweg shifted to the north of the stack, allowing
the channel to bypass the topographic high formed by the growing stack. Thick levee deposits built up along the channel course
during the late Pleistocene and Holocene. These levees, along with the Pliocene and early Pleistocene lobes, are reflected
in the present-day sigmoid-shaped, convex offshore-trending contours. Thus, the interplay of subduction- and collision-related
anticlines, tectonic-related channel ponding, and avulsion has contributed to the slope morphology of the southern Kurile
Trench. 相似文献
695.
696.
Formation of pockmarks by pore-water escape 总被引:1,自引:1,他引:1
P. K. Harrington 《Geo-Marine Letters》1985,5(3):193-197
During the course of a North Sea rig site investigation, a number of seabed depressions were observed on side-scan sonar records, some of which may be identified as pockmarks. Others are described as pits. A pockmark evolutionary series is proposed on the basis of all these features with a suggested mechanism which would favor release of pore water, but does not exclude gas escape. Acoustic voids are considered to be a related phenomenon. 相似文献
697.
Observations from a surface mooring, in a weak-flow regime over the southeastern Bering Sea shelf, were used to derive surface heat fluxes for the period May–July 1996. Changes in heat content of the water column also were determined from subsurface temperature measurements. Agreement of net surface heat flux and change in heat content was within 2%. This result provides additional evidence that heat advection and diffusion are small in this region. 相似文献
698.
The basic relations of the classical dyamic method have been complemented with the condition allowing for the non-monotonicity
of the vertical kinematic structure. The elements of the multi-layered system of geostrophic currents have been found to correlate
over depth with seawater density and hydrostatic pressure distribution. An example of the analysis of the vertical structure
of currents, involving specific hydrological data, is given.
Translated by Vladimir A. Puchkin. 相似文献
699.
A. Mascle R. Vially E. Deville B. Biju-Duval J.P. Roy 《Marine and Petroleum Geology》1996,13(8):941-961
The Southeast Basin of France is the thickest onshore French sedimentary basin which contains locally as much as 10 km of Mesozoic-Cenozoic sediment. Basin development occurred in several stages between late Carboniferous and late Cretaceous times. Partial tectonic inversion took place during two compressive events, the so-called ‘Pyrenean’ and ‘Alpine’ phases of late Cretaceous-early Tertiary and late Tertiary ages respectively. They are separated by an intervening stretching event of Oligocene age, which further south resulted in the opening of the western Mediterranean oceanic basin. As a result of this complex tectonic history, structural traps were difficult to image on the seismic data shot during the first phase of exploration prior to 1980. Oil and gas natural seeps, and shows in several wells, indicate that some petroleum systems are, or have been active, at least in some places.The present erosional western margin of the basin is more or less superimposed on the initial Triassic-Jurassic margin. Margin subsidence and Tertiary inversion are discussed using regional sections on which the polyphase history of the entire basin is well shown. These sections are located on three major segments where the Mesozoic margin is either partly preserved (Ardèche), or has been partly inverted in late Tertiary times (Vercors-Chartreuse), or has been completely inverted in early Tertiary times (Corbières-eastern Pyrenees). 1-D ‘Genex’ basin modelling on the Ardèche segment, and 2-D ‘Thrustpack’ structural-maturity modelling in the Vercors-Chartreuse segment are used to further assess the remaining petroleum plays. 相似文献
700.