Andrusz, G.; Harloe, M.; Szelenyi, I. (eds.) Cities after socialism. Urban and regional change and conflict in post- socialist societies.     

Herman van der Wusten 《GeoJournal》1997,42(4):465-467

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Editorial note     

Herman van der Wusten  Olga Gritsai 《GeoJournal》1996,38(1):v-v

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Early Namaqua low-pressure metamorphism: deformation and porphyroblast growth in the Zoovoorby staurolite schist, South Africa     

H. C. HUMPHREYS  J. M. VAN BEVER DONKER 《Journal of Metamorphic Geology》1990,8(2):159-170

This paper describes the deformation and metamorphism recorded in the Zoovoorby staurolite schist, a sliver of pelitic supracrustal material in the 1.3–1.0 Ga eastern Namaqua Province, South Africa. The supracrustal Biesjepoort Group, of which the schist is a part, has undergone at least four phases of deformation (D₁–D₄). D₁ and D₂ are preserved in the pelitic schists; staurolite and garnet grew during D₁, with staurolite growth persisting to the very earliest D₂ crenulation. Andalusite, found in more Mg-rich schists, grew during D₂, overprinting both S₁ schistosity and S₀ banding. S₂ has been rotated both with respect to S₁ (preserved as parallel orientated inclusion trails in garnet and staurolite) and with respect to its original orientation (preserved as open D₂ crenulations in staurolite). Staurolite is dissolved against S₂ in zones of progressive shear. The pseudomorphing of staurolite and andalusite by cordierite, and the preservation of relic grains of both minerals in a wide range of garnet–cordierite pelites throughout the eastern Namaqua Province infers that what is preserved fortuitously in the Zoovoorby locality is representative of the early metamorphic history of a much larger terrane. The high thermal gradients needed to attain estimated conditions of 540–550° C and 1.6–2.4 kbar require substantial heat input. Large amounts of foliated (syn-D₂) granite amongst the supracrustal succession are inferred to be the result of delamination of a thickened crust at a destructive plate margin, generating an elevated thermal gradient during D₁–D₂ times.  相似文献   

Introduction to LADEDA — a Geographic Information System     

P.R. VAN BERK EL  R.D. WILLIAMS 《New Zealand geographer》1985,41(2):84-90

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Microbial-foraminiferal episodes in the Early Aptian of the southern Tethyan margin: ecological significance and possible relation to oceanic anoxic event 1a   总被引：4，自引：0，他引：4  

A. IMMENHAUSER  H. HILLGÄRTNER†  E. VAN BENTUM 《Sedimentology》2005,52(1):77-99

Two regionally significant microbial-foraminiferal episodes (∼150 kyr each) occur within the Early Aptian shallow marine platform in Oman and throughout eastern Arabia. The stratigraphically lower of these two intervals is characterized by isolated or coalescent domes that share similarities with modern, open-marine stromatolites from the Exuma Cays, Bahamas. The upper interval is predominantly built by a problematic Lithocodium/Bacinella consortium in buildup and massive boundstone facies. Based on high-resolution chemostratigraphy, these shoalwater intervals are coeval with oceanic anoxic event 1a (OAE1a; Livello Selli). Field evidence demonstrates that the buildup episodes alternate with stratigraphic intervals dominated by rudist bivalves. This biotic pattern is also recognized in other coeval Tethyan sections and is perhaps a characteristic shoalwater expression of the OAE1a. The short-lived regional expansions of this microbial-foraminiferal out-of-balance facies cannot be explained by local environmental factors (salinity and oxygen level) alone and the buildup consortia do not occupy stressed refugia in the absence of grazing metazoans. Judging from recent analogues, the main fossil groups, i.e. microbial assemblages, macroalgae, larger sessile foraminifera, and rudist bivalves, all favoured elevated trophic levels but with different tolerance limits. The implication of this is that the influence of palaeofertility events, possibly related to OAE1a, on carbonate platform community structures must be investigated. The observations made in these coastal sections are a significant first step for the improved understanding of the Early Aptian period of biotic, oceanic and climatic change.  相似文献   

Microfabric analysis by manual and automated stereological procedures: a methodological approach to Antarctic tillite     

ARJEN P. STROEVEN  PIET STROEVEN†  JAAP J. M. VAN DER MEER‡ 《Sedimentology》2005,52(2):219-233

Fabric analysis is commonly used to infer former movement directions of diamictons; however, analysis techniques are typically time consuming and partly subjective. Stereological analysis provides an alternative for objective determination of the preferred orientation of particles. The ability of manual and automated stereological procedures to determine the preferred orientation of particles (120–4000 µm) in tillite is assessed, using core samples from Mount Feather, McMurdo Dry Valleys, Antarctica. Orthogonal sets of vertical thin sections were subjected to directed secant analysis involving the determination of the number of intersections between particle outlines and a rotating series of parallel lines. The manual analysis reveals a weakly developed three-dimensional tilt angle (plunge) of 68°. This reflects the depth-averaged subglacial deformational structure of the deposit. Because the preferred orientation signal is weak, in the automated set-up this signal is obscured by the effect of digitization, hampering the reliable assessment of the orientation direction. The study shows microfabric variability within the studied cored section that is interpreted as a shear fabric. Reliable macrostructural information that might constrain ice flow directions requires a larger number of randomly or systematically drawn core samples from which averaged microstructural fabrics can be derived.  相似文献   

Oxygen isotope variability in snow from western Dronning Maud Land, Antarctica and its relation to temperature   总被引：1，自引：0，他引：1  

M. M. HELSEN  R. S. W. VAN DE WAL  M. R. VAN DEN BROEKE  D. VAN AS  H. A. J. MEIJER  C. H. REIJMER 《Tellus. Series B, Chemical and physical meteorology》2005,57(5):423-435

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A unified formulation for the three-dimensional shallow water equations using orthogonal co-ordinates: theory and application     

Herman W. J. Kernkamp  Henri A. H. Petit  Herman Gerritsen  Erik D. de Goede 《Ocean Dynamics》2005,55(3-4):351-369

In this paper, the formulations of the primitive equations for shallow water flow in various horizontal co-ordinate systems and the associated finite difference grid options used in shallow water flow modelling are reviewed. It is observed that horizontal co-ordinate transformations do not affect the chosen co-ordinate system and representation in the vertical, and are the same for the three- and two-dimensional cases. A systematic derivation of the equations in tensor notation is presented, resulting in a unified formulation for the shallow water equations that covers all orthogonal horizontal grid types of practical interest. This includes spherical curvilinear orthogonal co-ordinate systems on the globe. Computational efficiency can be achieved in a single computer code. Furthermore, a single numerical algorithmic code implementation satisfies. All co-ordinate system specific metrics are determined as part of a computer-aided model grid design, which supports all four orthogonal grid types. Existing intuitive grid design and visual interpretation is conserved by appropriate conformal mappings, which conserve spherical orthogonality in planar representation. A spherical curvilinear co-ordinate solution of wind driven steady channel flow applying a strongly distorted grid is shown to give good agreement with a regular spherical co-ordinate model approach and the solution based on a β-plane approximation. Especially designed spherical curvilinear boundary fitted model grids are shown for typhoon surge propagation in the South China Sea and for ocean-driven flows through Malacca Straits. By using spherical curvilinear grids the number of grid points in these single model grid applications is reduced by a factor of 50–100 in comparison with regular spherical grids that have the same horizontal resolution in the area of interest. The spherical curvilinear approach combines the advantages of the various grid approaches, while the overall computational effort remains acceptable for very large model domains.  相似文献   

PERMEABILITY AND CONSOLIDATION OF SEDIMENT MIXTURES AS FUNCTION OF SAND CONTENT AND CLAY MINERALOGY   总被引：1，自引：0，他引：1  

W. JACOBS W. G. M. VAN KESTEREN J. C. WINTERWERP 《国际泥沙研究》2007,22(3):180-187

The current study is the first step in a systematic experimental research on the erosion behaviour of sand-mud mixtures. It concerns the effect of a varying sand content and clay mineralogy on the porosity, structure, strength and permeability of artificially generated sediment mixtures. The permeability of a sediment mixture is an especially significant parameter concerning the type of erosion that occurs. It determines if the erosion of the bed is either a drained or an undrained process, respectively indicating surface erosion or mass erosion. Measurements on various mixtures concerning the consolidation coefficient and the permeability have been executed. Results show a distinct transition of behaviour between a sand-silt dominated network structure and a clay-water matrix. The occurrence of these two types of structures appears to depend on the porosity of the volume fraction of sand related to silt, which is, therefore, an important parameter concerning the type of erosion. Finally, the study provides a valuable data set that can be used as a reference for following stages of this research on the erosion behaviour of natural cohesive sediments.  相似文献   

Reconstructing the Growth of High Topography Across Eastern Tibet in Space and Time     

Kevin FURLONG  Eric KIRBY  WANG Erchie  Matthijs VAN SOEST  XU Ganqing  SHI Xuhu  Peter KAMP  Martin DANISIK  Kip HODGES 《《地质学报》英文版》2013,87(Z1):37-37

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