A constitutive model for mechanical and chemo‐mechanical compaction in sedimentary basins and finite element analysis          下载免费PDF全文

A. Brüch  S. Maghous  F.L.B. Ribeiro  L. Dormieux 《国际地质力学数值与分析法杂志》2016,40(16):2238-2270

Compaction and associated fluid flow are fundamental processes in sedimentary basin deformation. Purely mechanical compaction originates mainly from pore fluid expulsion and rearrangement of solid particles during burial, while chemo‐mechanical compaction results from Intergranular Pressure‐Solution (IPS) and represents a major mechanism of deformation in sedimentary basins during diagenesis. The aim of the present contribution is to provide a comprehensive 3D framework for constitutive and numerical modeling of purely mechanical and chemo‐mechanical compaction in sedimentary basins. Extending the concepts that have been previously proposed for the modeling of purely mechanical compaction in finite poroplasticity, deformation by IPS is addressed herein by means of additional viscoplastic terms in the state equations of the porous material. The finite element model integrates the poroplastic and poroviscoplastic components of deformation at large strains. The corresponding implementation allows for numerical simulation of sediments accretion/erosion periods by progressive activation/deactivation of the gravity forces within a fictitious closed material system. Validation of the numerical approach is assessed by means of comparison with closed‐form solutions derived in the context of a simplified compaction model. The last part of the paper presents the results of numerical basin simulation performed in one dimensional setting, demonstrating the ability of the modeling to capture the main features in elastoplastic and viscoplastic compaction. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Temporal and bathymetric resolution of nautiloid death assemblages in stratigraphically condensed oozes (New Caledonia)          下载免费PDF全文

Adam Toma&#x;ových  Jn Schlgl  Darrell S. Kaufman  Natlia Hud kov 《地学学报》2016,28(4):271-278

Cephalopod shells can be affected by postmortem transport and biostratigraphic condensation, but direct estimates of the temporal and spatial resolutions of cephalopod assemblages are missing. Amino acid racemisation calibrated by ¹⁴C demonstrates a centennial‐scale time averaging (<500 years) of Nautilus macromphalus in sediment‐starved, epi‐ and mesobathyal pelagic environments. The few shells that are thousands of years old are highly degraded. The median occurrence of dead shells is at 445 m depth, close to the 300–400 m depth where living N. macromphalus are most abundant. Therefore, dead shells of this species accumulate at a centennial temporal resolution and with excellent bathymetric fidelity. Dead Nautilus shells exist for only a few hundred years on the seafloor, in contrast to the biostratigraphically condensed mixture of extant foraminifers and foraminifers that went extinct during the Pleistocene. Cephalopod shells that do not show any signs of early diagenetic cementation are unlikely to be biostratigraphically condensed.  相似文献   

Long-term variation of the semi-annual wave maxima in geomagnetic activity     

Emil M. Apostolov  Vojtěch Letfus  Reviewer J. Pýcha 《Studia Geophysica et Geodaetica》1989,33(4):379-390

Summary The time variations of the amplitudes and phases of the semi-annual variation in geomagnetic activity, characterized by the linear planetary index aa, have been analysed for the period 1868–1985. The results provide qualitative confirmation of Murayama's conclusions [13] about the systematic f phase in dependence on the changes in the level of solar activity and give support to Russel-McPherron's mechanism [16] concerning the effect of the predominant polarity of the interplanetary magnetic field. A distinctly expressed variation of the phase differences in the course of the sunspot cycle and of the 22-year cycle, and specific variations related to the sequence of four consecutive cycles have been established, as well as a well-defined 90-year period, all of them as a reflection of analogous variations in solar activity. The variations of the phase differences observed around the equinoxes can be explained by the combined effect of the mechanisms of the axial and equinoctial hypothesis. It is assumed that a displacement of the maxima of the semi-annual variation to dates after the equinoxes will be observed in the ascending parts and a reverse displacement towards the equinoxes and earlier dates in the desccending parts of the following sunspot cycles 22 nad 23.On leave from the Geophysical Institute of the Bulgarian Academy of Sciences, Akad. G. Bonchev Str. bl. 3, Sofia 1113, Bulgaria.  相似文献   

Dynamical stability of convection cells in the upper mantle     

Ludvík Urban  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1988,32(2):151-158

Summary A two-dimensional flow model of an incompressible fluid with constant viscosity has been used to study the changes in the large-scale flow pattern (aspect ratio 4). Implications for convection in the Earth's mantle are discussed.

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a ¶rt; mn uuu ua u¶rt;mu nm m unm ¶rt; uu uu mu ama¶rt;a. ¶rt;am mam ¶rt; uu amuu u.

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On the gravitation absorption hypothesis     

Zdeněk Šimon  Jan Kostelecký  Antonín Zeman  Reviewer L. Skalský 《Studia Geophysica et Geodaetica》1988,32(1):16-23

Summary It is recommended that the data from measurements with supraconducting gravity meters be also analysed with regard to verifying the gravitation absorption hypothesis. Based on theoretical data from a3-year period, the spectrum of the assumed effect of shielding the gravitational influence of the Sun by the Earth's body on the value of the acceleration of gravity has been calculated for the tidal station Brussels (Figs 2a–e).

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¶rt;aam aauuam ¶rt;a uu n¶rt;uaumau ma mu u nuunm n¶rt;auaumauu. a mmuu ¶rt;a a mmu nu¶rt; u nm n¶rt;naa ma auauaumau ¶rt;mu a m a uu u u mmu ¶rt; nuu mauu (u. 2a–).

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КРИТИКА     

Milan Burša  Jiří Vaněk  Oldřich Novotný  Ladislav Křivský  Petronela Ochabová  Jan Bednář 《Studia Geophysica et Geodaetica》1988,32(4):416-420

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Moravian and Silesian nationalities: A new phenomenon in the ethnic map of the Czech Lands?     

P. Daněk 《GeoJournal》1993,30(3):249-254

In the 1991 population census, 1.4 million inhabitants of the Czech Republic applied for Moravian or Silesian nationality, which did not exist before.They expressed their consciousness of territorial appurtenance to the historical provinces of Moravia and Silesia and by this declaration they set it above the appurtenance to the Czech nation. New social cleavage thus developed in ethnically almost homogeneous environment of the Czech Republic, which constitutes a potential threat of the further splitting of the State. Trying to find the causes of such a phenomenon, the author deals with the territorial differentiation of these inhabitants and factors which influenced it. The close interconnection with political demands is stressed. The insensive centralizing measures of the communist regime are considered as the direct impulses of the present development. The phenomenon is understood as a specific manifestation of the posttotalitarian social crisis in Central and Eastern Europe.  相似文献   

The atmospheric mean energetic level and external forcing     

Dagmar Novotná  Vojtěch Vítek 《Studia Geophysica et Geodaetica》1991,35(1):33-38

Summary The atmospheric mean energetic level and corresponding flow pattern are studied theoretically in terms of the prescribed divergence of the horizontal wind vector. The divergence field may reflect the diabatic effect due to particles of extraterrestrial origin.  相似文献   

Problems of the theoretical model applied to geosciences     

Radan Květ 《GeoJournal》1994,34(4):365-370

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Radioactive and trace element distribution in basaltic rocks of Lower Silesia     

Vladimír Kropáček  Věra Vaňková  Reviewer J. Fiala 《Studia Geophysica et Geodaetica》1985,29(3):290-299

Summary The distribution of radioactive(Th, U, K) and selected trace(Rb, Sr, Ba, Y, Zr, V, Cr, Ni) elements in volcanic rocks from the Opole and Jawor regions of the Lower Silesia has been studied. The behaviour of these elements in the studied rocks indicates that the Lower Silesian volcanic rocks are characterized by less differentiated type than other volcanic rocks of the Bohemian Massif, the Opole rock types probably having a less differentiated character than the Jawor rock types.

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¶rt;a an¶rt;u a¶rt;uamu(Th, U, K) u m ¶rt;u(Rb, Sr, Ba, Y, Zr, V, Cr, Ni) m auu n¶rt;a am n u u uuu. a n mam n¶rt;num, m aum u uuu n¶rt;mam ¶rt; aamuu n¶rt; u ¶rt;uuau, aum u ana¶rt; uu. au a n¶rt;num, m auu n¶rt; amu n ¶rt;uuau ma ua n¶rt; u amu .

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