Relationship Between Lineaments and Ground Water Occurrence in Western Botswana   总被引：8，自引：0，他引：8  

Magowe Magowe  James R. Carr 《Ground water》1999,37(2):282-286

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Resistance of salt marsh substrates to near-instantaneous hydrodynamic forcing     

Helen Brooks  Iris Möller  Simon Carr  Clementine Chirol  Elizabeth Christie  Ben Evans  Kate L. Spencer  Tom Spencer  Katherine Royse 《地球表面变化过程与地形》2021,46(1):67-88

Salt marshes deliver vital ecosystem services by providing habitats, storing pollutants and atmospheric carbon, and reducing flood and erosion risk in the coastal hinterland. Net losses in salt marsh areas, both modelled globally and measured regionally, are therefore of concern. Amongst other controls, the persistence of salt marshes in any one location depends on the ability of their substrates to resist hydrodynamic forcing at the marsh front, along creek margins and on the vegetated surface. Where relative sea level is rising, marsh elevation must keep pace with sea-level rise and landward expansion may be required to compensate for areal loss at exposed margins. This paper reviews current understanding of marsh substrate resistance to the near-instantaneous (seconds to hours) forcing induced by hydrodynamic processes. It outlines how variability in substrate properties may affect marsh substrate stability, explores current understanding of the interactions between substrate properties and erosion processes, and how the cumulative impact of these interactions may affect marsh stability over annual to decadal timescales. Whilst important advances have been made in understanding how specific soil properties affect near-instantaneous marsh substrate stability, less is known about how these properties interact and alter bulk substrate resistance to hydrodynamic forcing. Future research requires a more systematic approach to quantifying biological and sedimentological marsh substrate properties. These properties must then be linked to specific observable erosion processes, particularly at the marsh front and along creek banks. A better understanding of the intrinsic dynamics and processes acting on, and within, salt marsh substrates will facilitate improved prediction of marsh evolution under future hydrodynamic forcing scenarios. Notwithstanding the additional complications that arise from morphodynamic feedbacks, this would allow us to more accurately model the future potential protection from flooding and erosion afforded by marshes, while also increasing the effectiveness of salt marsh restoration and recreation schemes. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Contact metamorphism of pelitic,psammitic and calcareous sediments in the Southern Highlands of New South Wales     

Bryan E. Chenhall  Brian G. Jones  Paul F. Carr 《Australian Journal of Earth Sciences》2013,60(3):389-401

Contact metamorphism has been recognized along a 4 km wide belt adjacent to the shallow‐dipping eastern margin of the Arthursleigh Tonalite, an Early Devonian pluton of the Marulan Batholith, eastern New South Wales. In Ordovician psammitic and pelitic rocks three zones of progressive contact metamorphism range from muscovite + biotite + chlorite assemblages in the outer zone to K‐feldspar + cordierite assemblages adjacent to the pluton and in metasedimentary xenoliths. Retrograde phenomena include extensive replacement of metamorphic minerals by ‘sericite’ and chlorite. Calcareous metasediments adjacent to the tonalite typically contain assemblages of quartz + calcic plagioclase + ferrosalite + sphene, or wollastonite + calcite + diopside with minor grossularite and vesuvianite. Thermal effects in volcanic rocks along the western margin of the pluton are confined to recrystallization of the groundmass.

The regional geology indicates confining pressures of approximately 1 kbar at the time of emplacement of the tonalite. Contact metamorphic temperatures were estimated from two‐feldspar geothermometry to attain a maximum of approximately 590°C for rocks in the innermost zone of the aureole and 700°C for the xenoliths. Fluid compositions attending progressive contact metamorphism were water‐rich (Xco₂<0.2) and, during cooling, these fluids probably account for the extensive retrograde hydration observed in the aureole.  相似文献   

AXIOM: Advanced X‐ray imaging of the magnetosheath     

S. Sembay  G. Branduardi‐Raymont  J.P. Eastwood  D.G. Sibeck  A. Abbey  P. Brown  J.A. Carter  C.M. Carr  C. Forsyth  D. Kataria  S. Kemble  S. Milan  C.J. Owen  A.M. Read  L. Peacocke  C.S. Arridge  A.J. Coates  M.R. Collier  S.W.H. Cowley  A.N. Fazakerley  G. Fraser  G.H. Jones  R. Lallement  M. Lester  F.S. Porter  T. Yeoman 《Astronomische Nachrichten》2012,333(4):388-392

AXIOM (Advanced X‐ray Imaging Of the Magnetosphere) is a concept mission which aims to explain how the Earth's magnetosphere responds to the changing impact of the solar wind using a unique method never attempted before; performing wide‐field soft X‐ray imaging and spectroscopy of the magnetosheath, magnetopause and bow shock at high spatial and temporal resolution. Global imaging of these regions is possible because of the solar wind charge exchange (SWCX) process which produces elevated soft X‐ray emission from the interaction of high charge‐state solar wind ions with primarily neutral hydrogen in the Earth's exosphere and near‐interplanetary space (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Simultaneous measurements of Martian plasma boundaries by Rosetta and Mars Express     

N.J.T. Edberg  A.I. Eriksson  U. Auster  S. Barabash  A. Bößwetter  C.M. Carr  S.W.H. Cowley  E. Cupido  M. Fränz  K.-H. Glassmeier  R. Goldstein  M. Lester  R. Lundin  R. Modolo  H. Nilsson  I. Richter  M. Samara  J.G. Trotignon 《Planetary and Space Science》2009,57(8-9):1085-1096

We present the first two-spacecraft near-simultaneous observations of the Martian bow shock (BS), magnetic pileup boundary (MPB) and photo-electron boundary (PEB) obtained by the plasma instruments onboard Rosetta and Mars Express during the Rosetta Mars flyby on February 25, 2007. Our observations are compared with shape models for the BS and MPB derived from previous statistical studies. The MPB is found at its expected position but the BS for this event is found significantly closer to the planet than expected for the rather slow and moderately dense solar wind. Cross-calibration of the density measurements on the two spacecraft gives a density profile through the magnetosheath, indicating an increasing solar wind flux during the Rosetta passage which is consistent with the multiple BS crossings at the Rosetta exit.  相似文献   

Technologies for coastal erosion control: Edited by M. L. PalUnited Nations,New York, 1982, 132 pp.     

A.P. Carr 《Estuarine, Coastal and Shelf Science》1983,17(5):596-597

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Conservation of mass in tidal loading computations     

Duncan Carr Agnew 《Geophysical Journal International》1983,72(2):321-325

Summary. A re-examination of methods for including mass conservation in tidal loading shows that the spherical harmonic correction of Farrell is incorrect. The effect of unconserved mass for a nearly ocean-covered earth shows that the proper spherical harmonic expansion of the Newtonian Green function is the average of the internal and external expansions.  相似文献   

The influence of palaeoenvironment and lava flux on the emplacement of submarine, near-shore Late Permian basalt lavas, Sydney Basin (Australia)     

Paul F. Carr  Brian G. Jones 《Journal of Volcanology and Geothermal Research》2001,112(1-4)

Lava flux and a low palaeoslope were the critical factors in determining the development of different facies in the Late Permian Blow Hole flow, which comprises a series of shoshonitic basalt lavas and associated volcaniclastic detritus in the southern Sydney Basin of eastern Australia. The unit consists of a lower lobe and sheet facies, a middle tube and breccia facies, and an upper columnar-jointed facies. Close similarities in petrography and geochemistry between the basalt lavas from the three facies suggest similar viscosities at similar temperatures. Sedimentological and palaeontological evidence from the sedimentary units immediately below the Blow Hole flow suggests that the lower part of the volcanic unit was emplaced in a cold water, shallow submarine environment, but at least the top of the uppermost lava was subaerial with some palaeosol development. The lower lobe and sheet facies was emplaced on a low slope (<2°) in a lower to middle shoreface environment with water depths of 20–25 m. Lava may have transgressed from subaerial to subaqueous and was emplaced relatively passively with lava flux sufficiently high and uniform to form lobes and sheets rather than pillows. The middle unit probably originated from a subaerial vent and flowed into a shallow (10–15 m) submarine environment, and wave action probably interacted with the advancing lava front to form a lava delta. Lava flux was sufficiently high to produce well-developed, subcircular lava tubes, which lack evidence for thermal erosion. In some areas, lava ‘burrowed’ into the unconsolidated, water-saturated lava delta and sand pile to produce intrusive contacts. The upper columnar-jointed unit represents a ponded facies probably emplaced initially in water depths <5 m but whose top was subaerial.  相似文献   

Response to comment by Dr. Denis Marcotte     

James Russell Carr 《Mathematical Geology》1992,24(5):573-575

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Spatial and seasonal aspects of beach stability     

A. P. Carr  M. W. L. Blackley  H. L. King 《地球表面变化过程与地形》1982,7(3):267-282

Recent work at three contrasting sites in England and Wales has shown characteristics atypical of those frequently reported elsewhere. These differences are:

• (a) Taking each entire beach system there is no uniform trend of erosion or accretion, nor a progressive variation in beach elevation or volume alongshore, from one survey to the next. However, for Swansea Bay the ‘long-term’ (i. e. 18 months) range in profile height along that stretch of coast where the alignment of the beach is normal to the direction of wave approach, correlates well with computed wave energy derived from relevant offshore wave directions.
• (b) While beach variability is greatest during the ‘winter’ (i. e. storm) period there is no overall tendency for a drawdown of sediment from the intertidal zone at that time. Response times are relatively short. Thus high beach levels need not necessarily be associated with ‘summer’ conditions.
• (c) Although in Swansea Bay there is a tendency for the beach height to fluctuate least at mid-tide level this is not true of the other two sites. In no area does sediment eroded from the upper exposed part of the beach regularly appear to be deposited on the lower exposed part, or vice versa.

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