Sand ridges on the inner Atlantic shelf of North America: Morphometric comparisons with Huthnance stability model   总被引：1，自引：0，他引：1  

A. G. Figueiredo Jr.  D. J. P. Swift  Stubblefield  T. L. Clarke 《Geo-Marine Letters》1981,1(3-4):187-191

Sand ridge fields on the inner shelf of the Middle Atlantic Bight are generally thought to have formed in response to northeasterly storm flows as the shoreface underwent erosional retreat with postglacial sea-level rise. However, the hydrodynamic mechanism is poorly unerstood. Coastal boundary models see the ridges as responses of the seafloor to distortions in the flow induced by the coastal boundary. Stability models propose that an irregular initial topography will evolve toward an ordered array of bedforms in response to repeated flow events. The two classes of models are not mutually exclusive, nor are members within each class mutually exclusive. Results of measurements of ridge spacing on the inner Atlantic shelf of North America agree with the predictions of stability models.  相似文献   

Calculation of the added mass of circular cylinders in shallow water     

David Clarke   《Ocean Engineering》2001,28(9):354

The added mass of hull section shapes must be known, in order to carry out any studies of ship motions, which may be associated with either seakeeping or manoeuvring. Determination of the added mass in deep water can involve conformal mapping or surface singularity distributions. However, in shallow water the problem of determining the added mass is made more difficult by the proximity of the seabed. In this paper, three approaches to the problem of finding the added mass of semi-circular sections are explored. Although there is no known exact solution to this problem, the relationships given by the three methods are compared and the approximate nature of the solutions is examined. The first method is a series solution, which is taken here to include more terms than are normally given in the existing literature. The other two solutions are considered to be new, and so are given in some mathematical detail.  相似文献   

IGU special issue on population redistribution in Asia and the Pacific region     

Clarke JI  Kawabe H 《Population geography : a journal of the Association of Population Geographers of India》1981,3(1-2):1-120

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Monazite behaviour and age significance in poly-metamorphic high-grade terrains: A case study from the western Musgrave Block, central Australia     

Nigel M. Kelly  Geoffrey L. Clarke  Simon L. Harley 《Lithos》2006,88(1-4):100-134

Integrated, in situ textural, chemical and electron microprobe age analysis of monazite grains in a migmatitic metapelitic gneiss from the western Musgrave Block, central Australia has identified evidence for multiple events of growth and recrystallisation during poly-metamorphism in the Mesoproterozoic. Garnet + sillimanite-bearing metapelite underwent partial melting and segregation to palaeosome and leucosome during metamorphism between 1330 and 1296 Ma, with monazite grains in leucosome recording crystallisation at 1300 Ma. Monazite breakdown during melting is inferred to have occurred in the palaeosome. During a subsequent granulite facies event at 1200 Ma, deformation and metamorphism of leucosome and palaeosome resulted in partial disturbance of ages and potential minor growth on 1300 Ma monazite in leucosome. Growth of new, high-Y (+HREE) monazite in palaeosome domains occurred during garnet breakdown in the presence of sillimanite to cordierite and spinel, as a result of post-peak isothermal decompression. Diffusive enrichment of resorbed garnet rims in Y + HREE suggests garnet breakdown occurred slower than volume diffusion of REE. Monazite in both palaeosome and leucosome were subsequently partially to penetratively recrystallised during a retrogression event that is suggested to have occurred at 1150–1130 Ma. The intensity of recrystallisation and disturbance of ages appears linked to proximity to retrogressed garnet porphyroblasts and their occurrence in the relatively reactive or ‘fertile’ local environments provided by the palaeosome/mesosome volumes, which caused localised changes in retrogressive fluids towards compositions more aggressive to monazite. Like reaction textures, it is apparent that domainal equilibrium and reaction may control or at least strongly influence monazite REE and U–Th–Pb chemistry and hence ages.  相似文献   

The Port Mouton Shear Zone: intersection of a regional fault with a crystallizing granitoid pluton   总被引：2，自引：0，他引：2  

D. Barrie Clarke  Krista L. McCuish  Ron H. Vernon  Victor Maksaev  Brent V. Miller   《Lithos》2002,61(3-4):141-159

The peraluminous tonalite–monzogranite Port Mouton Pluton is a petrological, geochemical, structural, and geochronological anomaly among the many Late Devonian granitoid intrusions of the Meguma Lithotectonic Zone of southern Nova Scotia. The most remarkable structural feature of this pluton is a 4-km-wide zone of strongly foliated (040/subvertical) monzogranites culminating in a narrow (10–30 m), straight, zone of compositionally banded rocks that extends for at least 3 km along strike. The banded monzogranites consist of alternating melanocratic and leucocratic compositions that are complementary to the overall composition of that part of the pluton, suggesting an origin by mineral–melt and mineral–mineral sorting. Biotite and feldspar are strongly foliated in the plane of the compositional bands. These compositional variations and foliations originated by a process of segregation flow during shearing of the main magma with a crystallinity of 55–75%. Subsequent minor brittle fracturing of feldspars, twinning of microcline, development of blocky sub-grains in quartz, and kinking of micas demonstrate overprinting by a high-temperature deformation straddling the monzogranite solidus. Small folds and late sigmoidal dykes indicate dextral movement on the shear zone. This Port Mouton Shear Zone (PMSZ) is approximately co-linear with the only outcrops of Late Devonian mafic intrusions in the area, two of which are syn-plutonic with well-developed mingling textures in the marginal tonalite of the Port Mouton Pluton. Also closely co-linear with the mafic intrusions are a granitoid dyke that extends well beyond the outer contact of the Port Mouton Pluton, a swarm of large aligned angular xenolithic slabs, a zone of thin wispy schlieren banding, a large Be-bearing pegmatite, and a breccia pipe with abundant garnetiferous metapelitic xenoliths. In various ways, the shear zone may control all of these features. The Port Mouton Shear Zone is parallel to many other NE-trending faults and shear zones in the northern Appalachians, probably related to the docking of the Meguma Zone along the Cobequid–Chedabucto Fault system.  相似文献   

The interpretation of reaction textures in Fe‐rich metapelitic granulites of the Musgrave Block,central Australia: constraints from mineral equilibria calculations in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3     

R. W. White  Roger Powell  G. L. Clarke 《Journal of Metamorphic Geology》2002,20(1):41-55

Fe‐rich metapelitic granulites of the Musgrave Block, central Australia, contain several symplectic and coronal reaction textures that post‐date a peak S2 metamorphic assemblage involving garnet, sillimanite, spinel, ilmenite, K‐feldspar and quartz. The earliest reaction textures involve spinel‐ and quartz‐bearing symplectites that enclose garnet and to a lesser extent sillimanite. The symplectic spinel and quartz are in places separated by later garnet and/or sillimanite coronas. The metamorphic effects of a later, D3, event are restricted to zones of moderate to high strain where a metamorphic assemblage of garnet, sillimanite, K‐feldspar, magnetite, ilmenite, quartz and biotite is preserved. Quantitative mineral equilibria calculations in the system K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–Fe₂O₃ (KFMASHTO) using Thermocalc 3.0 and the accompanying internally consistent dataset provide important constraints on the influence of TiO₂ and Fe₂O₃ on biotite‐bearing and spinel‐bearing equilibria, respectively. Biotite‐bearing equilibria are shifted to higher temperatures and spinel‐bearing equilibria to higher pressures and lower temperatures in comparison to the equivalent equilibria in K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O (KFMASH). The sequence of reaction textures involving spinel is consistent with a D2 P–T path that involved a small amount of decompression followed predominantly by cooling within a single mineral assemblage stability field. Thus, the reaction textures reflect changes in modal proportions within an equilibrium assemblage rather than the crossing of a univariant reaction. The D3 metamorphic assemblage is consistent with lower temperatures than those inferred for D2.  相似文献   

The Organization of Production in High Technology Industries: An Empirical Assessment*     

Audrey E. Clarke  Brian P. Holly 《The Professional geographer》1996,48(2):127-139

Recent attention given to the concept of vertical integration and disintegration of production processes has identified the existence of a continuum, with small, flexibly specialized producers at one end and large, mass production units at the other end. Firms along the continuum constantly strive for the optimum combination of economies of scale and scope. This paper attempts to identify the organizational characteristics of high technology firms in one industrial complex of the U.S. Manufacturing Belt. A principal components analysis is performed on a number of theoretically relevant variables for a sample of high technology establishments in Northeast Ohio. The results indicate that the region contains a variety of organizational forms ranging from isolated workshops to large, vertically integrated assembly plants. These findings conform to expectations derived from recent conceptualizations in the literature. Additional empirical research will further enhance understanding of the processes that shape the organization of production in territorial complexes.  相似文献   

A geomatics data integration technique for coastal change monitoring     

J. P. Mills  S. J. Buckley  H. L. Mitchell  P. J. Clarke  S. J. Edwards 《地球表面变化过程与地形》2005,30(6):651-664

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A three-dimensional approach to fault seal analysis: fault-block juxtaposition & argillaceous smear modelling     

Stuart M. Clarke  Stuart D. Burley †  Graham D. Williams 《Basin Research》2005,17(2):269-288

Three‐dimensional (3D) numerical modelling of fault displacement enables the building of geological models to represent the complex 3D geometry and geological properties of faulted sedimentary basins. Using these models, cross‐fault juxtaposition relationships are predicted in 3D space and through time, based on the geometries of strata that are cut by faults. Forward modelling of fault development allows a 3D prediction of fault‐zone argillaceous smear using a 3D application of the Shale Gouge Ratio. Numerical models of the Artemis Field, Southern North Sea, UK and the Moab Fault, Utah, USA are used to demonstrate the developed techniques and compare them to traditional one‐ and two‐dimensional solutions. These examples demonstrate that a 3D analysis leads to significant improvements in the prediction of fault seal, the analysis of the interaction of the sealing properties of multiple faults, and the interpretation of fault seal within the context of sedimentary basin geometry.  相似文献   

A multiscale masking method for point geographic data     

Keith C. Clarke 《International journal of geographical information science》2016,30(2):300-315

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