Ice Conditions in Zalew Szczecinski (Stettiner Haff) and in Zatoka Pomorska (Pomeranian Bight) during the winter of 1995/96     

Natalija Schmelzer  Marzenna Sztobryn  Ida Stanisławczyk 《Ocean Dynamics》1996,48(1):89-95

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Book reviews     

Yu. N. Korenkov  Carl W. Cable  Vernon F. Cormier  Vassily Levin  Jacek A. Majorowicz  Yehuda Bock  Waclaw M. Zuberek  Teng-fong Wong  William L. Power  Gary A. Robbins  Piotr Raczka  Krzysztof E. Haman  Katarzyna Chałasinska-Macukow  Ryszard Balcer  Henryk Piwkowski 《Pure and Applied Geophysics》1991,137(3):309-336

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On the energy gap for Fe-poor oxide and silicate minerals     

Sławomir Maj 《Physics and Chemistry of Minerals》1991,17(8):711-715

A relationship between the energy gap (E _G) and the density (ρ) over mean atomic weight (〈A〉) ratio for Fe-poor oxide and silicate minerals is derived from simple properties of their free atom-components. Theoretical considerations are based on the Lorentz electron theory of solids. The eigenfrequency ν ₀ of elementary electron oscillators, in energy units h ν ₀, is identified with the energy gap of a solid. The numerical relation is of the form $$(\langle U_0 \rangle ^2 - E_G^2 )\frac{{\langle A\rangle }}{\rho } = \frac{4}{3}\pi \hbar ^2 \frac{{e^2 }}{m}N = 276.79 eV^2 cm^3 /mol$$ where 〈U ₀〉 is the average first ionization potential (per free atom), ? is crossed Planck's constant, e is the electron charge, m is the electron rest mass, and N is Avogadro's number. For several geophysically interesting oxide and silicate minerals which are in general composed of four different elements (O, Si, Mg and Al), we obtain from laboratory data that the mean value of $$\left\langle {[\langle U_0 \rangle ^2 - (E_G^{lab} )^2 ]\frac{{\langle A\rangle }}{\rho }} \right\rangle \approx 248.2 \pm 20.9eV^2 cm^3 /mol.$$ .  相似文献   

Normal form,Lie-Poisson structure and reduction for the Henon-Heiles system     

Stanisław Kasperczuk 《Celestial Mechanics and Dynamical Astronomy》1995,63(3-4):245-253

The reduced Henon-Heiles system is investigated as a Hamiltonian dynamical system obtained by applying the normalization of the HamiltonianH=1/2(p ₁ ² +p ₂ ² +q ₁ ² +q ₂ ² )+1/3q ₁ ³ –q ₁ q ₂ ² to fourth-degree terms. The related equations of motion are bi-Hamiltonian and possess the Lie-Poisson structure. Each Lie-Poisson structure possesses an associated Casimir function. When reduced to level sets of these functions, the equations of motion take various symplectic forms. The various reductions give different coordinate representations of the solutions. These coordinate representations are used to seek the simplest representation of the solutions.  相似文献   

ROV study of a giant pockmark on the Gabon continental margin   总被引：1，自引：4，他引：1  

H. Ondréas  K. Olu  Y. Fouquet  J. L. Charlou  A. Gay  B. Dennielou  J. P. Donval  A. Fifis  T. Nadalig  P. Cochonat  E. Cauquil  J. F. Bourillet  M. Le Moigne  M. Sibuet 《Geo-Marine Letters》2005,25(5):281-292

A giant, 800-m wide pockmark, called Regab, was discovered along the Equatorial African margin at 3160-m water depth and was explored by remote operated vehicle (ROV) as part of the Zaiango (1998–2000) and Biozaire (2001–2003) projects carried out conjointly by TOTAL and a number of French research institutes. A microbathymetric map obtained using the ROV sensors shows that the pockmark actually consists of a cluster of smaller pockmarks aligned N70 along a 15-m deep depression. Methane was recorded all over the pockmark, the highest values along the axis of the depression where massive carbonate crusts and dense seep communities were also found. Several faunal species belong to the Vesicomyidae and Mytilidae bivalve families, as well as to Siboglinidae (Vestimentifera) tubeworms. Preliminary analyses confirm their association with symbiotic bacteria, thus documenting their dependence on fluid seeps. The pockmark appears to be related to an infilled channel, visible on the seismic data 300 m below the seafloor, which may act as a reservoir for biogenic fluids supplied to the trap from the surrounding sediments.  相似文献   

Neogene tectonic evolution of the Alboran Sea from MCS data   总被引：1，自引：3，他引：1  

M. C. Comas  V. García-Dueñas  M. J. Jurado 《Geo-Marine Letters》1992,12(2-3):157-164

The structural framework of the northern Alboran Sea is one of a series of grabens or half-grabens developed during various Miocene rifting stages. MCS profiles and well data reveal early to late Miocene seismo-stratigraphic units affected by rifting. Three rifting episodes—latest Aquitanian-Burdigalian, Langhian-Serravalian, and Tortonian-are postulated to have caused significant extension and crustal thinning beneath the Alboran Sea. The middle Miocene episode led to major depocenters and triggered mud diapirism. Post-Tortonian tectonics modified the architecture of the Miocene Alboran Basin and formed the present structure, seafloor morphology, and boundaries of the Alboran Sea.  相似文献   

Remineralization and accumulation of organic carbon and nitrogen in marine sediments of eutrophic bays: the case of the Bay of Concepcion, Chile     

Laura Farías   《Estuarine, Coastal and Shelf Science》2003,57(5-6):829-841

The Bay of Concepcion (36°40′S; 73°02′W) is a semi-enclosed and shallow embayment in which biogeochemical processes are seasonally coupled to coastal upwelling during the austral spring and summer. The nutrient cycle in the bay is complex due to the combined effects of a pronounced O₂ minimum layer and high nutrient concentrations both originating from subsurface equatorial water during coastal upwelling and a rapid rate of sediment nutrient recycling. The sediments are characterized by a high content of organic matter mainly due to the extremely high rates of phytoplankton production and deposition. During the upwelling period, a black flocculent layer frequently covers the sediment–water interface in the inner part of the bay where an extensive mat of Beggiatoa spp. develops. Three approaches are used to analyse the extent to which the benthic system recycles or retains nutrients at two stations, located at the centre (station C, St. C) and mouth (station B, St. B) of the bay for a 1-year period (March 1996–1997): (1) estimation of C and N remineralization rates based on SO₄²⁻ reduction measurements, (2) calculation of C and N turnover rates using a diagenetic model applied to total organic carbon and total nitrogen vertical distributions and, (3) construction of C and N budgets from direct measurements of sedimentation (from a sediment trap) and estimates of the C and N burial rates. Depth-integrated SO₄²⁻ reduction rates varied between 3.4 (winter) and 25.5 (summer) mmol m⁻² d⁻¹. Estimated C and N oxidation rates ranged between 7.9 and 87.8 mol C m⁻² yr⁻¹ and between 0.9 and 6.9 mol N m⁻² yr⁻¹, respectively. Each approach yielded minor differences in the C and N remineralization rates (and also minor differences between both studied stations), except when the kinetic model was applied to C and N distribution without including the presence of the flocculent layer. The rates of carbon oxidation and sulphate reduction were considerably higher than in other coastal sediments with similar depositional regime. The C and N burial rates were 2.23 and 0.21 (St. C) and 1.30 and 0.09 (St. B) mol m⁻² yr⁻¹, respectively. The C/N ratio of the buried fraction was ca. 10.6 at St. C and 14.4 at St. B. Because the observed differences in burial rates could not be ascribed to distinctive depositional (both stations have similar sediment accumulation rates) and oceanographic (similar O₂ concentration and hydrography) conditions, differences may be due to in part spatial heterogeneity in the supply of organic matter. The degree of preservation of organic matter as plankton detritus and nitrogen accumulating bacterial biomass associated with Beggiatoa spp. at St. C may also be involved.  相似文献   

Effects of rainy season on mobilization of contaminants from tsunami deposits left in a coastal zone of Thailand by the 26 December 2004 tsunami     

Witold Szczuciński  Przemysław Niedzielski  Lidia Kozak  Marcin Frankowski  Anetta Zioła  Stanisław Lorenc 《Environmental Geology》2007,53(2):253-264

Study on contamination of tsunami sediments deposited on 26 December 2004 conducted shortly after the tsunami in coastal zone of Thailand revealed elevated contents of salts in water-soluble and some heavy metals and arsenic in bioavailable fractions (Szczuciński et al. in Env Geol 49:321–331, 2005). Few months later rainy season started and effected in total rainfall of over 3,300 mm. This paper presents results of survey repeated 1 year after the tsunami. To assess the effects of rainy season on mobilization of previously determined potential contaminants, the same locations were sampled again and analysed with the same methods. The tsunami deposit layer was well preserved but in many locations the sediments were coarser than just after tsunami due to washing out of finer fractions. The water-soluble salts contents were strongly reduced after the rainy season. However, the concentrations of acid leachable heavy metals and metalloids were still elevated in comparison to reference sample from an area not impacted by tsunami. It is possible that the metals and metalloids are successively moved to more bioavailable fraction from forms which were more resistant to mobilization.  相似文献   

Archaeological objects in loesses recognized by GPR research at the site Karmanowice,Poland     

Artur Poręba  Wacław M. Zuberek  Jolanta Nogaj-Chachaj  Andrzej Kotyrba  Sławomir Siwek 《Acta Geophysica》2007,55(4):640-651

The aim of the research was to examine subsurface soil layers with the use of the Ground Penetrating Radar (GPR) method. Neolithic archaeological post in Karmanowice was examined. On the basis of earlier geophysical researches and archaeological premises, eight measurement profiles had been chosen. Ground Penetrating Radar system with antenna of 500 MHz frequency was applied. The measurements were made with 30 and 60 ns time windows. The results were shown as the GPR sections. The analysis of the obtained results allowed us to outline anomalies connected with the appearance of archaeological objects in subsurface soil layers. The border between the anthropogenically changed upper layer and undisturbed loess was established, and the sections of slope wash layers were designated. Anomalies were confirmed by digging and test drillings. Additionally, 2D resistivity imaging method was used for verification of specific anthropogenic anomalies.  相似文献   

Wavefield downward extrapolation for migration velocity analysis on Marmousi data-set     

Andrzej Kostecki  Anna Półchłopek 《Acta Geophysica》2007,55(2):209-221

The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures. Determination of velocity is the recursive process which means that the wavefield on depth level z _n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z _n . The velocity ν [x, z _n − z _n−1] can be thus treated as interval velocity in Δz _n = z _n − z _n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media.  相似文献