A Late Tournaisian synmetamorphic folding and thrusting event in the eastern Variscan foreland: 40Ar/39Ar evidence from the phyllites of the Wolsztyn–Leszno High,western Poland     

Żelaźniewicz  Andrzej  Marheine  Dirk  Oberc-Dziedzic  Teresa 《International Journal of Earth Sciences》2003,92(2):185-194

A Variscan foreland in western Poland comprises two NW-trending basement highs, which are concealed under Carboniferous through Triassic strata of the Fore-Sudetic Monocline (FSM). Both highs consist of multiply deformed quartz-sericite - albite - chlorite phyllites of unknown protolith age. ⁴⁰Ar/³⁹Ar laser probe dating of white micas in up to 0.5-mm-thick mica layers, which form the S₂ axial-plane foliation in phyllites of the Wolsztyn-Leszno High, yielded an age of 340.1DŽ.6 Ma for the lower greenschists facies metamorphism and probably also for the F₂ folding. This deformation was associated and followed by thrusting, which brought about the basement highs. The latter delivered clasts to overlying late Viséan-early Namurian flysch basin that was mainly sourced from the Saxothuringian Sudetes in which most of the deformation occurred between 345-335 Ma. The FSM basement may represent an independent terrane, referred to as the Wielkopolska terrane, belonging to the Armorican Terrane Assemblage.  相似文献   

Characteristics of tephra in Holocene lake sediments on King George Island, West Antarctica: implications for deglaciation and paleoenvironment     

Yong Il Lee  Hyoun Soo Lim  Ho Il Yoon  Andrzej Tatur 《Quaternary Science Reviews》2007,26(25-28):3167-3178

Several reworked tephra layers in gravity-flow deposits are present in lacustrine core sediments collected from Hotel and Rudy Lakes on King George Island, South Shetland Islands, maritime sub-Antarctica. This study tests the values of tephra for establishing regional tephrochronologies for lakes in ice-covered landscapes in the vicinity of volcanoes. The tephra record is more abundant in a long Hotel Lake core (515 cm long). This study uses volcanic glass samples from five tephra layers of Hotel Lake and from one tephra layer of Rudy Lake. Morphologically, tephras are mixtures of basaltic and pumice shards, both having various degrees of vesicularity. Major element analyses of glass shards reveal that the majority of the glass fragments belong to basic glass (<60 wt% SiO₂), compositionally ranging from basalt to low-silica andesite and subalkaline series medium-K tholeiites, probably sourced from Deception Island located 130 km southwest of King George Island. Less than 20% of tephra belongs to silicic glass and occurs in three tephra horizons E of Hotel Lake. However, source volcano(es) for about 10% of basic tephra and silicic tephra are not readily identified from nearby volcanic centers. Except for the studied tephra in Rudy Lake, all tephra samples in Hotel Lake are not ashfall deposits but reworked and redeposited pyroclasts derived from retreating ice sheet, resulting in the occurrence of geochemically equivalent tephra samples in different tephra horizons. The dating of the studied tephra horizons represents the timing of deglaciation rather than that of volcanic eruptions. The result of this study implies that combined with sedimentological information more chemical criterion is necessary to study tephrochronology and regional correlation and to understand paleoenvironmental changes using tephra.  相似文献   

Methods of Searching for Planets Around Pulsars     

Konacki  Maciej  Maciejewski  Andrzej J. 《Earth, Moon, and Planets》1998,81(1):101-102

Earth, Moon, and Planets -  相似文献   

On hyperelasticity for clays   总被引：1，自引：0，他引：1  

Andrzej Niemunis  Marcin Cudny 《Computers and Geotechnics》1998,23(4):221-236

Under purely elastic conditions a constitutive model for clays should be conservative. This can be achieved by using a hyperelastic stress–strain relation derived from an elastic potential. To circumvent problems connected with formulation of a suitable potential a simple concept of back-stress elasticity is proposed. Several elastic models are critically reviewed, two of which had been originally incorrectly classified as hyperelastic. A novel elastic potential which can be used to generate various hyperelastic models is proposed. Its salient feature is that the resulting stiffness is a homogeneous function of order 1 with respect to stress. An example of Mathematica calculation with tensorial differentiation is enclosed (Wolfram S. Mathematica. A system for doing mathematics by computer. Addison-Wesley Publishing, 1988). ©  相似文献   

An algorithm for the optimum distribution of a regional seismic network — II. An analysis of the accuracy of location of local earthquakes depending on the number of seismic stations     

Andrzej Kijko 《Pure and Applied Geophysics》1977,115(4):1011-1021

Summary Seven optimal networks consisting of 4 to 10 stations are compared for a given region, where velocity-depth profiles and the distribution of seismic intensity are known. Assuming that the standard error of arrival time is _t =0.05 s and the standard errors of the parameters of velocity-depth profiles are equal to 5% of their values, the average standard errors of the origin time and focus coordinates are estimated. The application of optimum methods to the planning of seismic networks in the Lublin Coal Basin is presented, and maps of standard errors of origin time , depth and epicenter ( _xy ) for the case of an optimum network of 6 seismic stations are given.  相似文献   

Diagrams of electrochemical equilibria of the system copper-potassium ethylxanthate-water at 25°C     

Tadeusz Hepel  Andrzej Pomianowski 《International Journal of Mineral Processing》1977,4(4):345-361

On the basis of thermodynamic calculations, diagrams of metastable electrochemical equilibria of the system copper-potassium ethylxanthate-water, at 25°C were constructed. The equilibria equations and diagrams for the total activity of [EtX^?] + [HEtX] + 2 [(EtX)₂] (equalling 10^?1, 10^?4 and 10^?7 mol/dm³), are presented. The practical conclusions resulting from these diagrams for the flotation of native copper are discussed.  相似文献   

GEOGRAPHY IN MEXICO     

Jerry P. Schofer  Silvana Levi  Efrain Pena Villada  Andrzej M. Zeronski 《The Professional geographer》1990,42(3):380-382

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Non-integrability of the three-body problem     

Andrzej J. Maciejewski  Maria Przybylska 《Celestial Mechanics and Dynamical Astronomy》2011,110(1):17-30

We consider the planar problem of three bodies which attract mutually with the force proportional to a certain negative integer power of the distance between the bodies. We show that such generalisation of the gravitational three-body problem is not integrable in the Liouville sense.  相似文献   

Seasonal transport pattern of chromium(III and VI) in a stream receiving wastewater from tanneries     

Ewa Szalinska  Janusz Dominik  Davide A.L. Vignati  Andrzej Bobrowski  Boguslaw Bas 《Applied Geochemistry》2010

Water, suspended matter and sediment samples from a system heavily impacted by wastewater from numerous small tanneries (the upper Dunajec River, southern Poland) were collected to establish the annual cycle of Cr. To study possible oxidation processes the speciation of Cr and Mn concentrations were also investigated. This study showed that Cr(III and VI) temporal and spatial distributions are regulated by coupled anthropogenic (source location and emissions) and hydrologic factors (water flow and particle transport). Chromium(III) concentrations in all compartments varied seasonally as a function of the hydrological regime, production cycle in tanneries and distance from the discharge location. Cr(III) was largely associated with the particulate phase and rapidly deposited in river bed sediments. Contaminated river sediments were however flushed during flood periods to the reservoir located downstream from tanneries. During the tanning season (November to March), Chromium(III) concentrations in the water column and total Cr concentration in sediments exceeded relevant ecotoxicological guidelines only upstream from the reservoir, which trapped about 70% of the annual Cr(III) load transported by the Dunajec river. A correlation between Cr(VI)/Cr(III) ratios and Mn concentration in sediments downstream from the reservoir suggests the possibility of Cr(III) oxidation in natural conditions.  相似文献   

Numerical modeling and neural networks to identify model parameters from piezocone tests: I. FEM analysis of penetration in two‐phase continuum     

Rafał F. Obrzud  Andrzej Truty  Laurent Vulliet 《国际地质力学数值与分析法杂志》2011,35(16):1703-1730

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