Geometry and architecture of faults in a syn-rift normal fault array: The Nukhul half-graben, Suez rift, Egypt     

Paul Wilson  Rob L. Gawthorpe  David Hodgetts  Franklin Rarity  Ian R. Sharp 《Journal of Structural Geology》2009,31(8):759-775

The geometry and architecture of a well exposed syn-rift normal fault array in the Suez rift is examined. At pre-rift level, the Nukhul fault consists of a single zone of intense deformation up to 10 m wide, with a significant monocline in the hanging wall and much more limited folding in the footwall. At syn-rift level, the fault zone is characterised by a single discrete fault zone less than 2 m wide, with damage zone faults up to approximately 200 m into the hanging wall, and with no significant monocline developed. The evolution of the fault from a buried structure with associated fault-propagation folding, to a surface-breaking structure with associated surface faulting, has led to enhanced bedding-parallel slip at lower levels that is absent at higher levels. Strain is enhanced at breached relay ramps and bends inherited from pre-existing structures that were reactivated during rifting. Damage zone faults observed within the pre-rift show ramp-flat geometries associated with contrast in competency of the layers cut and commonly contain zones of scaly shale or clay smear. Damage zone faults within the syn-rift are commonly very straight, and may be discrete fault planes with no visible fault rock at the scale of observation, or contain relatively thin and simple zones of scaly shale or gouge. The geometric and architectural evolution of the fault array is interpreted to be the result of (i) the evolution from distributed trishear deformation during upward propagation of buried fault tips to surface faulting after faults breach the surface; (ii) differences in deformation response between lithified pre-rift units that display high competence contrasts during deformation, and unlithified syn-rift units that display low competence contrasts during deformation, and; (iii) the history of segmentation, growth and linkage of the faults that make up the fault array. This has important implications for fluid flow in fault zones.  相似文献   

Watershed urbanization and changing flood behavior across the Los Angeles metropolitan region   总被引：3，自引：0，他引：3  

Jingfen Sheng  John P. Wilson 《Natural Hazards》2009,48(1):41-57

This article examines the effects of watershed urbanization on stream flood behavior in the Los Angeles metropolitan region. Stream gauge data, spatially distributed rainfall data, land use/land cover, and census population data were used to quantify change in flood behavior and urbanization in multiple watersheds. Increase in flood discharge started at the very early stage of the urbanization when the population density was relatively low but the rate of increase of flood discharge varied across watersheds depending on the distribution of the imperviousness surface and flood mitigation practices. This spatial variability in rainfall–runoff indices and the increasing flood risk across the metropolitan region has posed a challenge to the conventional flood emergency management, which usually responds to flood damages rather than being concerned with the broader issues of land use, land cover, and planning. This study pointed out that alternative land use planning and flood management practices could be mitigating the urban flood implemented hazard.  相似文献   

High-resolution carbon isotope changes in the Permian–Triassic boundary interval, Chongqing, South China; implications for control and growth of earliest Triassic microbialites     

Xinan Mu  Steve Kershaw  Yue Li  Li Guo  Yuping Qi  Alan Reynolds 《Journal of Asian Earth Sciences》2009,36(6):434

High-resolution δ¹³C_CARB analysis of the Permian–Triassic boundary (PTB) interval at the Laolongdong section, Beibei, near the city of Chongqing, south China, encompasses the latest Permian and earliest Triassic major facies changes in the South China Block (SCB). Microbialites form a distinctive unit in the lowermost 190 cm above the top of the Changhsing Formation (latest Permian) at Laolongdong, comparable to a range of earliest Triassic sites in low latitudes in the Tethyan area. The data show that declining values of δ¹³C_CARB, well-known globally, began at the base of the microbialite. High positive values (+3 to 4 ppt) of δ¹³C_CARB in the Late Permian are interpreted to indicate storage of ¹²C in the deep waters of a stratified ocean, that was released during ocean overturn in the earliest Triassic, contributing to the distinctive fall in isotope values; this interpretation has been stated by other authors and is followed here. The δ¹³C_CARB curve shows fluctuations within the microbialite unit, which are not reflected in the microbialite structure. Comparisons between microbialite branches and adjacent micritic sediment show little difference in δ¹³C_CARB, demonstrating that the microbialite grew in equilibrium with surrounding seawater. The Early Triassic microbialites are interpreted to be a response to upwelling of bicarbonate-rich poorly oxygenated water in low latitudes of Tethys Ocean, consistent with current ocean models for the PTB interval. However, the decline of δ¹³C_CARB may be due to a combination of processes, including productivity collapse resulting from mass extinction, return of deep water to ocean surface, oxidation of methane released from methane hydrate destabilisation, and atmospheric deterioration. Nevertheless, build-up of bicarbonate-rich anoxic deep waters may be expected as a result of the partial isolation of Tethys, due to continental geography; release of bicarbonate-rich deep water, by ocean upwelling, in the earliest Triassic may have been an inevitable consequence of this combination of circumstances.  相似文献   

ALMA capabilities for observations of continuum emission     

T. L. Wilson 《Astrophysics and Space Science》2008,313(1-3):13-14

The Atacama Large Millimeter/submillimeter Array, ALMA, combines a large collecting area, very sensitive receivers and a location on a high dry site. ALMA’s sensitivity for continuum measurements is increased with the added feature of an 8 GHz instantaneous bandwidth. Taken together, these four factors provide unparalleled sensitivity in the millimeter/submillimeter wavelength range. With its great sensitivity and angular resolution, ALMA will transform our view of mm/sub-mm astronomy.  相似文献   

非潮汐海洋运动对地球动力学扁率变化的贡献   总被引：1，自引：1，他引：0       下载免费PDF全文

胡小工  Jian-Li CHEN  黄珹  B.D.Tapley  C.R.Wilson 《地球物理学报》2004,47(3):428-432

通过考察全球海洋环流数值模型以及TOPEX/Poseidon海洋测高数据,得到结论：1997/1998年后的部分J2异常变化可能来自海洋环流变化导致的质量重新分布,具体地说是太平洋环流变化导致的从高纬地区向低纬地区的质量迁移. 本工作表明来自于海洋内部温盐效应的变化对J2异常变化有重要贡献,进一步证实了卫星激光测距资料所得结果的可靠性.  相似文献   

Correlation of the Kimmeridgian-Tithonian (Jurassic) boundary beds exposed in the Boulonnais,France with those at Kimmeridge,Dorset, UK     

Ramues Gallois  Alain Vadet  Steve Etches 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(2):187-195

Sediments of Kimmeridgian and Tithonian age are well exposed on the Boulonnais coast of northern France between Equihen and Cap Gris Nez and on the south coast of England at and adjacent to Kimmeridge Bay. Both successions were deposited on a marine shelf and lie within the Subboreal faunal province which enables detailed correlations to be made between them based on ammonite assemblages. They are, however, lithologically markedly different due to their environmental settings: close to a land area in the case of the Boulonnais and within a depositional basin in the case of Kimmeridge. The succession adjacent to the Kimmeridgian-Tithonian boundary exposed in the Boulonnais is highly condensed and laterally variable with more attenuated successions occurring close to the former Anglo-Brabant Massif land area. The boundary occurs at the end of a succession of up to six regressive-transgressive events that onlap the land area. This is in contrast to that at outcrop at Kimmeridge, where the Kimmeridgian-Tithonian boundary is marked by a correlative conformity in an unbroken basinal succession. The cliff and foreshore exposures in the Kimmeridge area provide the only unbroken succession in the Subboreal faunal province of the beds adjacent to the Kimmeridgian-Tithonian boundary.  相似文献   

INDIGENOUS ENVIRONMENTAL LEARNING IN A SMALL DEVELOPING COUNTRY: ADOLESCENTS IN BARBADOS, WEST INDIES   总被引：1，自引：0，他引：1  

Robert B. Potter  B.Sc.  Ph.D.  Mark Wilson  B.A.  M.Phil 《Singapore journal of tropical geography》1991,11(1):56-67

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Widespread 18O depletion in some precambrian granulites of Australia     

Allan F. Wilson  Ajoy K. Baksi 《Precambrian Research》1983,23(1):33-56

In the Strangways Range a broad tract of lower Proterozoic mafic and silicic granulites with δ ¹⁸O = 0.1 to 7.3% is depleted in ¹⁸O on average by 2–47% compared with high-grade gneisses and granitoids of Canada and other shields. The Fraser Range mafic granulites (δ¹⁸O ~ 7.2%) are enriched with respect to unaltered sea-floor basalts (~5.7%).In some rocks depletion in ¹⁸O could be related to dehydration during granulite-facies metamorphism and removal of the resultant products of partial melting. In other rocks pre-granulite reaction between heated seawater and hot basic intrusives seems to be a plausible mechanism of depletion in ¹⁸O. A direct correlation between depletion in ¹⁸O and the abundance of brown granulite hornblende suggests that ¹⁸O-depleted water was present in certain mafic rocks before the onset of granulite metamorphism, whereas in others brown hornblende was introduced during a phase of the granulite facies metamorphism itself.  相似文献   

The Palaeomagnetic History of a Doubly-baked Rock     

R. L. Wilson 《Geophysical Journal International》1962,6(3):397-399

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Light scattering by an optically thin inhomogeneous,spherically-symmetric planetary atmosphere: Brightness at the zenith near the terminator     

S. J. Wilson  K. K. Sen 《Astrophysics and Space Science》1980,71(2):405-410

The approximate method of representing the intensity by a three-stream angular division is used to compute the brightness at the zenith near the terminator of an optically thin, spherically-symmetric planetary atmosphere illuminated by parallel solar radiation. The results are compared with those of Sobolev obtained under classical Eddington approximation.Part of this work was done when the author was on sabbatical leave at Kanazawa Institute of Technology (Japan).  相似文献