Climatic and tectonic controls on chemical weathering in the New Zealand Southern Alps   总被引：2，自引：0，他引：2  

Andrew D Jacobson  Joel D Blum  Dave Craw 《Geochimica et cosmochimica acta》2003,67(1):29-46

Climatic and tectonic controls on the relative abundance of solutes in streams draining the New Zealand Southern Alps were investigated by analyzing the elemental and Sr isotope geochemistry of stream waters, bedload sediment, and hydrothermal calcite veins. The average relative molar abundance of major cations and Si in all stream waters follows the order Ca²⁺ (50%) > Si (22%) > Na⁺ (17%) > Mg²⁺ (6%) > K⁺ (5%). For major anions, the relative molar abundance is HCO₃⁻ (89%) > SO₄²⁻ (7%) > Cl⁻ (4%). Weathering reactions involving plagioclase and volumetrically small amounts of hydrothermal calcite define the ionic chemistry of stream waters, but nearly all streams have a carbonate-dominated Ca²⁺ and HCO₃⁻ mass-balance. Stream water Ca/Sr and ⁸⁷Sr/⁸⁶Sr ratios vary from 0.173 to 0.439 μmol/nmol and from 0.7078 to 0.7114, respectively. Consistent with the ionic budget, these ratios lie solely within the range of values measured for bedload carbonate (Ca/Sr = 0.178 to 0.886 μmol/nmol; ⁸⁷Sr/⁸⁶Sr = 0.7081 to 0.7118) and hydrothermal calcite veins (Ca/Sr = 0.491 to 3.33 μmol/nmol; ⁸⁷Sr/⁸⁶Sr = 0.7076 to 0.7097).Streams draining regions in the Southern Alps with high rates of physical erosion induced by rapid tectonic uplift and an extremely wet climate contain ∼10% more Ca²⁺ and ∼30% more Sr²⁺ from carbonate weathering compared to streams draining regions in drier, more stable landscapes. Similarly, streams draining glaciated watersheds contain ∼25% more Sr²⁺ from carbonate weathering compared to streams draining non-glaciated watersheds. The highest abundance of carbonate-derived solutes in the most physically active regions of the Southern Alps is attributed to the tectonic exhumation and mechanical denudation of metamorphic bedrock, which contains trace amounts of calcite estimated to weather ∼350 times faster than plagioclase in this environment. In contrast, regions in the Southern Alps experiencing lower rates of uplift and erosion have a greater abundance of silicate- versus carbonate-derived cations. These findings highlight a strong coupling between physical controls on landscape development and sources of solutes to stream waters. Using the Southern Alps as a model for assessing the role of active tectonics in geochemical cycles, this study suggests that rapid mountain uplift results in an enhanced influence of carbonate weathering on the dissolved ion composition delivered to seawater.  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   

Book reviews     

John D. Halfman  Vivienne Jones  H. J. B. Birks  Hilary H. Birks 《Journal of Paleolimnology》1992,7(3):257-262

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Results of Two Pumping Tests in Wisconsin Age Weathered Till in Iowa   总被引：2，自引：0，他引：2  

LaDon Jones  Tracy Lemar  Chin-Ta Tsai 《Ground water》1992,30(4):529-538

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Radar backscatter from the ocean: Dependence on surface friction velocity     

W. Linwood Jones  L. C. Schroeder 《Boundary-Layer Meteorology》1978,13(1-4):133-149

From the mid 1960s to the present, the normalized radar cross-section (NRCS) of the ocean has been measured using airborne radars operating over a frequency range of 0.4 to 14 GHz. Analyses of these data have shown that the NRCS was proportional to the ocean surface wind speed raised to some power, but the values of the exponent remained in dispute. This paper extends previous work and uses these NRCS measurements to demonstrate that to the first order, the NRCS is a function of only the friction velocity at the ocean's surface. Further analyses characterize the dependence of the NRCS on radar variables such as frequency, incidence angle, polarization, etc. Finally, recommendations are made for using Ku-band radars at large incidence angles for remote sensing of the wind friction velocity vector.  相似文献   

Electromagnetic analogue model measurements and finite-difference numerical calculations of the response of a conducting slab to three different source fields     

R.D. Hibbs  F.W. Jones  V. Ramaswamy  H.W. Dosso 《Physics of the Earth and Planetary Interiors》1978,16(4):327-340

This work compares experimental analogue model measurements and finite-difference numerical calculations of the electric and magnetic fields for a highly conducting slab embedded in a poorly conducting host earth for three different source field configurations. Measurements and calculations were carried out for a uniform source, a sheet current source with a y exp(?ay) current intensity distribution, and a horizontal magnetic dipole source. The results indicate reasonable agreement with some exceptions between the analogue and numerical methods. The source field is found to have an important effect on the field anomalies at the interface of the highly conducting slab and the poorly conducting host medium.  相似文献   

High temperature elasticity of rutile-structure MgF2     

Leonie E. A. Jones 《Physics and Chemistry of Minerals》1977,1(2):179-197

The elastic moduli of single-crystal MgF₂ have been determined by the ultrasonic pulse superposition technique as a function of temperature from T=298?650° K. These new data are consistent with those obtained by other ultrasonic pulse techniques at and below room temperature and agree favourably with polycrystalline data above room temperature. The elastic moduli (c) are represented by quadratic functions in T over the experimental temperature range with the curvature in the same sense for all the moduli. For the rutile-structure fluorides and oxides, evaluation of the temperature derivatives of the elastic moduli at constant volume indicates that the dominant temperature effect is extrinsic for (?K _S /?T) _P and intrinsic for (?μ/?T) _P , where K _S and μ are the isotropic bulk and shear moduli, respectively. There appears to be no simple relationship between (?c/?T) _P and crystallographic parameters for the rutile structure, and |(?c/?T) _P | for the fluorides is in general very much lower than the corresponding |(?c/?T) _P | for the oxides. For the pair of compounds MgF₂-TiO₂, there is no evident analogue relationship for high-temperature elastic properties.  相似文献   

Hydrologic factors and90Sr transport: A case study     

D. D. Huff  N. D. Farrow  J. R. Jones 《Environmental Geology》1982,4(1):53-63

Lack of runoff control is probably the most important potential source of problems in the operation of solid, low-level radioactive waste disposal areas. Solid waste disposal area (SWDA) 4 at Oak Ridge National Laboratory is an example of the combined effects of hydrologic factors and burial ground operations on radionuclide transport. Results from a study of⁹⁰Sr transport at SWDA 4 show that both surface water and groundwater flows are important runoff control considerations and may vary in relative importance over an extended period of time. For the area studied, it is currently estimated that at least 80% of the⁹⁰Sr transport is directly related to surface runoff. Therefore, it is concluded that the key to remedial action at SWDA 4 is to control surface runoff. Research supported by the Office of Waste Operations and Technology, U.S. Department of Energy, under contract W-7405-eng-26 with Union Carbide Corporation. Publication No. 1905, Environmental Sciences Division, ORNL.  相似文献   

Crustal structure from two-ship multichannel seismic profiles on the continental shelf off Northwest Scotland     

R.S. White  E.J.W. Jones  V.J. Hughes  D.H. Matthews 《Tectonophysics》1982,90(1-2)

We report a series of two-ship multichannel seismic experiments carried out on the continental shelf off northwest Scotland in February 1981. Both expanding spread and constant offset profiles were shot using explosives and a 16.4-1 airgun. The expanding spread shot-receiver configurations yield detailed information on the variation of seismic velocity with depth, whilst constant offset profiles allow us to monitor lateral variations in the upper crustal velocity structure. We show an example of marked variations in the efficiency of compressional to shear wave conversion along a constant offset profile over shallow Lewisian basement west of the Outer Hebrides which we interpret as due to changes in the uppermost basement velocity structure. From profiles north of Cape Wrath we show that where the Precambrian Lewisian basement is buried beneath Mesozoic sediments of variable thickness we can use the constant offset profile of the basement refractor to strip off the effect of the sediments and so correct deeper crustal returns on the coincident expanding spread profiles.  相似文献   

Productivity of algal epiphytes in a Georgia salt marsh: effect of inundation frequency and implications for total marsh productivity     

R. Christian Jones 《Estuaries and Coasts》1980,3(4):315-317

Primary production by algal epiphytes of dead Spartina alterniflora shoots in a Georgia salt marsh was measured using the ¹⁴C technique. A 2³ factorial design was used to quantify the effects of light intensity and inundation frequency (stem height) on carbon fixation at two sites along a salt marsh creek. Algae inundated daily fixed carbon more rapidly than those which had dried for several days, but this may have been the results of greater biomass on more frequently immersed stems. This result corroborates studies showing desiccation is not always a severe stress for intertidal algae. Similarity of epiphyte algal productivity to that of salt marsh benthic diatoms suggests that, given adequate substrate, the epiphytes may be an important source of primary production during some seasons of the year.  相似文献