Cathodoluminescence petrography of syntectonic quartz fibres     

Dorothee Dietrich  Paul R. Grant 《Journal of Structural Geology》1985,7(5):541-553

The cathodoluminescence of low grade metamorphic quartz is reported in the literature to be uniformly brown. This study describes an investigation of syntectonic quartz fibres from veins and pressure shadows contained in different carbonate units of the Helvetic Alps, Switzerland, and of Anglesey, U.K., with the Scanning Electron Microscope in the cathodoluminescence mode. The cathodoluminescence spectra measured show systematic variations between older and younger parts of the same fibre, and between fibres from different tectonic units. These variations can be related first to variations in the temperature of formation of the quartz fibres, and second to deformation-induced differences in the microstructure of the earlier formed parts of fibres during later imposed strains.  相似文献   

Effect of treatment with reserpine on the change in filtration rate of Mytilus edulis subjected to dissolved copper     

Richard Howell  Alasdair M. Grant  Norman E.J. Maccoy 《Marine pollution bulletin》1984,15(12):436-439

Exposure of specimens of Mytilus edulis to dissolved copper leads to a fall in the filtration rate measured in whole animals. The copper concentration leading to a 50% reduction in the filtration rate was found to be 0.094 mg I⁻¹. This effect was abolished on depletion of the monoamine content of the animal using reserpine. It is suggested that there may be a chemosensory mechanism present in the animals which responds to increased levels of metals in the seawater leading to a reduction in the rate of ciliary beating and mediated via the branchial nerve.  相似文献   

Carbohydrates in recent marine sediments—II. Occurrence and fate of carbohydrates in a recent stromatolitic deposit: Solar Lake,Sinai     

J. Klok  H.C. Cox  M. Baas  J.W. de Leeuw  P.A. Schenck 《Organic Geochemistry》1984,7(2):101-109

In a study on the diagenesis of carbohydrates in a recent stromatolitic deposit (Solar Lake, Sinai) monosaccharides are quantitated after mild acid hydrolysis and gas chromatographic analysis as alditol acetates. From the depth profiles of the individual monosaccharides relative to the total organic carbon three categories of carbohydrates can be distinguished. The behaviour of the various categories upon burial is discussed in terms of their potential to become a part of the organic matter that survives geological periods. The distribution patterns of especially the mono-O-methyl monosaccharides at various depths are characteristics for the bacterial communities present in the corresponding parts of the sediment column.  相似文献   

RbSr and KAr ages of paleozoic glauconites from Ohio—Indiana and Missouri,U.S.A.     

Norman K. Grant  Thomas E. Laskowski  K.A. Foland 《Chemical Geology》1984,46(3):217-239

Glauconite pellets from the Lower Silurian Brassfield Formation on both limbs of the Cincinnati Arch in Ohio and Indiana give a RbSr age of 370 ± 11 Ma, which is substantially younger than the stratigraphic age of the formation. The age is concordantcwith conventional KAr ages of 355 ± 6 and 368 ± 5 Ma for two of the same glauconites. Concordant ages were also obtained from the Viburnum Trend in Missouri, where glauconite pellets from the Davis Formation in an ore-zone collapse structure into the underlying Bonneterre Formation give a RbSr age of 387 ± 21 Ma and conventional KAr ages of 368 ± 5 and 369 ± 5 and 369 ± 5 Ma. A third suite of glauconite from the Bonneterre Formation in the Old Lead Belt ～ 10 km from the nearest ore body has given a RbSr age of 423 ± 7 Ma and slightly older conventional KAr ages of 434 ± 6, 445 ± 6 and 441 ± 11 Ma.Because these glauconite-bearing rocks have been buried to depths of less than 1 km, thermal resetting of the RbSr and KAr systematics appears unlikely. The initial ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios of the RbSr isochrons are similar to the ratios for vein- and vug-filling dolomite and calcite. This is consistent with resetting of the RbSr and KAr systems during diagenetic changes which included the isotopic equilibration (perhaps by cation exchange) of the Sr in the glauconite with that in the diagenetic and Mississippi Valley-type ore fluids. This interpretation implies that the age of the Mississippi Valley-type mineralization in the Viburnum Trend is Devonian rather than Carboniferous—Permian as has been inferred from paleomagnetic measurements.Cation-exchange experiments with a dilute Sr-bearing solution and an artificial oilfield brine indicate that glauconite adsorbs large amounts of Sr, some of which is sufficiently strongly attached to the glauconite lattice as to resist leaching with ammonium acetate. The introduction of this strongly attached Sr may be the first step in the resetting of the RbSr systematics of glauconite by cation exchange.  相似文献   

Mt. Pelée, martinique: may 8 and 20, 1902, pyroclastic flows and surges     

Richard V. Fisher  Grant Heiken   《Journal of Volcanology and Geothermal Research》1982,13(3-4)

The distribution, stratigraphic relationships and fragmental components of the May 8 and 20, 1902, pyroclastic flows from Mt. Pelée, Martinique, together with eyewitness accounts, suggest the following explanation for those eruptions. The eruptions were vertically directed magmatic (perhaps initiated phreatically), and contained abundant juvenile lithics from congealed magma of the dome and neck. This resulted in a two-part eruption column having (1) a dense, lithic-charged part which collapsed into the crater and flowed out of a pre-existing notch in its side, giving rise to pyrochlastic flows, and (2) a magmatically derived column containing gases, juvenile vitric material and crystals which largely by-passed the neck and dome and escaped into the atmosphere. All of the energy of the flows was apparently focused through the notch. They emerged fully turbulent and flowed down Rivière Blanche. Gravity segregation of large and abundant fragments soon resulted in a dense, high-concentration, poorly fluidized block-and-ash flow confined to the valley, leaving above a fully turbulent, high-energy ash-cloud surge. As the ash-cloud surge moved down the mountain, it continued to expand outward. The process of gravity segregation continued as the ash-cloud surge expanded, resulting in secondary block-and-ash underflows. Toward St. Pierre, the secondary block-and-ash flows developed on a gently sloping upland surface 100 m or more above the valley of Rivière Blanche. The turbulent, fragment-depleted surges above the secondary block-and-ash flows maintained sufficient energy to devastate the landscape outward to about 3000 m, including St. Pierre. The surges refracted around obstacles and in one place, moved up a small valley in a direction opposite to the main flows.  相似文献   

The nature of geomorphology. Alistair F. Pitty,Methuen, London, 1982. No. of pages: x+161. ISBN 0 416 32110 0 (0 416 32120 8 paperback)     

N. J. Cox 《地球表面变化过程与地形》1983,8(6):608-609

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The scaling of flow in vegetative structures     

Grant  Richard H. 《Boundary-Layer Meteorology》1983,25(2):171-191

Sensible heat flux data obtained from the U.S. Environmental Protection Agency's Regional Air Pollution Study in St. Louis, Missouri are presented and discussed. Large spatial variations exist in heat flux on both a land-use scale and the urban scale. Arguments based upon empirical data and sampling theory show that estimates of heat flux representative of an upwind fetch l _x require a minimum observation height proportional to z ^3/4. The influence of advection on the magnitude of the heat flux is also explored for both the urban and sub-urban or land-use scales. The data clearly indicate that advection can strongly modulate and even dominate the vertical heat flux above surfaces in areas which maintain large horizontal temperature gradients. The advection contribution is positive for cold air advection and negative for warm air advection, and may result from either the urban heat island or land-use mesoscale features. The depth of advective influence is directly proportional to the horizontal scale of the phenomenon and inversely proportional to horizontal temperature gradient.  相似文献   

Modelling sediment transport as a moving wave — The transfer and deposition of mining waste     

G. Pickup  R. J. Higgins  I. Grant 《Journal of Hydrology》1983,60(1-4):281-301

The movement of slugs of bedload from a discrete input point down a river has proved difficult to model using conventional finite-difference formulations of equations of motion. A model is proposed which makes explicit allowance for the mean sediment velocity and, through a dispersion coefficient, the distribution of sediment velocity about the mean. A second comparative model uses the normal mass conservation or sediment transport continuity approach. The models have been tested over a 43-month period using data from seven monitored cross-sections of the Kawerong River on Bougainville Island, Papua New Guinea, a system which receives waste from a large copper mine. The dispersion model performs considerably better than the mass-conservation model.  相似文献   

Reply     

T. Grant Caldwell  Hugh M. Bibby  Colin Brown 《Geophysical Journal International》2007,171(2):567-567

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Hydrogeology of the Winnipeg Formation in Manitoba, Canada     

Grant A. G. Ferguson  Robert N. Betcher  Stephen E. Grasby 《Hydrogeology Journal》2007,15(3):573-587

The Winnipeg Formation is the basal sedimentary unit throughout much of southern and central Manitoba, Canada, where it forms a regional aquifer over most of its extent. This aquifer is an important source of water in southeastern Manitoba and in Manitoba’s Interlake area, but in most other areas, groundwater within the aquifer is saline. Chemical and isotopic evidence indicate the presence of groundwaters of three different origins: (1) basin brines; (2) modern meteoric recharge; and (3) subglacial recharge that occurred during the late Pleistocene. Hydraulic head and sedimentary facies distributions indicate that the flow system in parts of the area is not in a state of equilibrium and saline waters will encroach on areas currently occupied by freshwater in some areas, while in other areas, freshwater will replace saline water. These features must be considered in groundwater resource management, as groundwater withdrawals will likely hasten these processes.

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Resumen La Formación Winnipeg es la unidad sedimentaria basal en la mayor parte de Manitoba central, Canadá, donde forma un acuífero regional en la mayor parte de su extensión. Este acuífero es una fuente importante de agua en el Sureste de Manitoba y el área de entrelagos de Manitoba, pero en la mayoría de las otras zonas del acuífero, el agua es salina. Las evidencias químicas e isotópicas indican que existen aguas subterráneas de tres orígenes diferentes: (1) salmueras de cuenca; (2) recarga meteórica actual; y (3) recarga subglacial ocurrida durante el Pleistoceno Superior. Los niveles piezométricos y la distribución de las facies sedimentarias indican que el sistema de flujo no se encuentra en estado de equilibrio en parte del área y las aguas salinas irán invadiendo áreas actualmente ocupadas con aguas dulces, mientras que en otras zonas el agua dulce está reemplazando al agua salina. Estos hechos deben ser considerados en la gestión de las aguas subterráneas como recurso, ya que las extracciones de agua acelerarán probablemente estos procesos.

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Résumé La Formation de Winnipeg est l’unité sédimentaire de base sur la plus grande partie du Sud et du centre du Manitoba au Canada, où elle forme un aquifère régional sur pratiquement toute son extension. Cet aquifère représente une ressource en eau importante dans le Sud-Est du Manitoba et dans les zones d’entre les lacs, mais salée dans la plus part des autres zones. Les indications isotopiques et chimiques permettent de distinguer trois différentes origines des eaux souterraines: (1) les saumures de bassin; (2) la recharge météoritique moderne; (3) la recharge sub-glaciaire qui est apparue durant le Pléistocène récent. Les charges hydrauliques et la distribution des faciès sédimentaires indiquent que le système d’écoulement dans certaines zones n’est pas dans un état d’équilibre et que les eaux salées empièteront sur des zones d’eau douce, tandis que dans d’autres zones l’eau douce remplacera les eaux salées. Ces aspects doivent être considérés dans la gestion des ressources en eau souterraine, car le prélèvement des eaux souterraines pourrait accentuer ces processus.

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