Global maps of lake-level fluctuations since 30,000 yr B.P.     

F.Alayne Street  A.T. Grove 《Quaternary Research》1979,12(1):83-118

This paper presents selected world maps of lake-level fluctuations since 30,000 yr B.P. These are based on a literature survey of 141 lake basins with radiocarbon-dated chronologies. The resulting patterns are subcontinental in scale and show orderly variations in space and time. They reflect substantial changes in continental precipitation, evaporation, and runoff, which are due to glacial/interglacial fluctuations in the atmospheric and oceanic circulations. In the tropics, high lake levels are essentially an interglacial or interstadial phenomenon, although there are important exceptions. Since extensive lakes during the Holocene corresponded with relatively high sea-surface temperatures, and therefore presumably with high evaporation rates on land, they are interpreted as the result of higher precipitation. Tropical aridity culminated in most areas at, or just after, the glacial maximum, although the present day is also characterized by a below-average abundance of surface water. In extratropical regions the mapped patterns are more complex. They vary markedly with latitude and proximity to major ice sheets. In these areas, evidence is at present insufficient to evaluate the relative contributions of precipitation and temperature to the observed lake-level record.  相似文献   

Recharge and pollution of the english chalk: Some possible mechanisms     

M.J. Reeves 《Engineering Geology》1979,14(4):231-240

Pore water in the Chalk is likely to remain essentially static under the influence of environmental forces with the exception of evapotranspiration. A process of piston displacement of water through networks of microfissures provides a possible mechanism for downward percolation through the unsaturated Chalk.

Maintenance of continuous diffusion equilibrium between fissure and pore water throughout downward migration allows the explanation of the observed rates of movement for thermonuclear tritium in the unsaturated zone. Activation of increasingly large fissures with increasing infiltration rates explains observed rapid water-table response under conditions of sustained high inflow, and is consistent with the behaviour of water quality parameters in the saturated aquifer. Whereas in the unsaturated zone it is suggested that 80 to 90% of total flow passes through microfissures, in the saturated aquifer fluid transport is essentially through macrofissures. Diffusion equilibrium between pore water and fissure water in the saturated zone is not therefore expected.

Individual macrofissures occasionally are enlarged by solution, making it possible for a large proportion of saturated flow to take place through relatively few preferential flow channels. Although the macrofissures, and particularly enlarged macrofissures, are largely responsible for aquifer transmissivity, microfissure storage may often be highly significant in terms of specific yield.  相似文献   

Teleseismic delay times,Bouguer anomalies and inferred thickness of the African lithosphere     

J.D. Fairhead  C.V. Reeves 《Earth and Planetary Science Letters》1977,36(1):63-76

Teleseismic P-wave travel time residuals (delay times) have been determined for 38 African seismograph stations using a total of 104 presumed Russian underground nuclear explosions. The delay times (T) for seismograph stations situated on Precambrian crust within the interior of Africa, where surface erosion is minimal, appear to be linearly related to both the station elevation (E) and Bouguer anomaly (B) such that: T=(1.12±0.32)E?(1.81±0.44)(1) T=?(0.013±0.005)B?(1.81±0.60)(2) where T is in seconds,E in kilometres and B in milligals. Equation 2 has been used to predict delay times more generally using the smoothed Bouguer anomaly map of Africa. The delay time map is tentatively used to derive a map of lithosphere thickness which takes into account lateral variations of velocity within both the lithosphere and asthenosphere. The lithospheric thickness model indicates a major zone of thin lithosphere (or thick asthenosphere) is associated with the East African Rift system and its continuation into southern Africa. Concomitant seismicity and volcanism further suggest that incipient separation of the continental plate is taking place along the axis of this zone.  相似文献   

Botswana gravity reference net     

R. M. Carruthers  C. V. Reeves 《Journal of Geodesy》1974,48(4):409-418

Gravity reference stations for the National Gravity Survey of Botswana have been established at twenty-three sites throughout the country in a net linked to existing bases in South Africa, Kenya and Zambia with an internal accuracy of better than 0.5 gravity units (one gravity unit, gu, equals an acceleration of 10⁻⁶ m.s⁻²). The field procedure and reduction of data are explained and a list is given of the gravity values.  相似文献   

Subterranean Natural Brines Produce Sodium Sulphate in West Texas     

C. C. Reeves  Jr. 《Ground water》1963,1(3):35-36

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European species of Thlaspi L. (Cruciferae) as indicators of nickel and zinc     

R.D. Reeves  R.R. Brooks 《Journal of Geochemical Exploration》1983,18(3):275-283

The analysis of herbarium specimens has shown that unusual metal uptake by European species of Thlaspi (Cruciferae, mustard family) is not confined to the well-known accumulation of zinc from calaminiferous soils. At least twelve species show unusual accumulation of nickel, to levels of 1000–30,000 μg/g (dry-mass basis), from serpentine or other nickel-rich substrates. In addition, accumulation of zinc to levels above 1000 μg/g in the dry mass of the plant is widespread; about three-quarters of the European species, from a wide variety of soil types, have been found to exhibit this behaviour in the natural state. These observations are significant in many fields, including taxonomy, plant physiology and phytochemistry, but are particularly important in extending the potential of biogeochemical methods of mineral exploration.  相似文献   

Time and space nonlocalities underlying fractional-derivative models: Distinction and literature review of field applications     

Yong Zhang  David A. Benson  Donald M. Reeves 《Advances in water resources》2009

We investigate the spatiotemporal nonlocality underlying fractional-derivative models as a possible explanation for regional-scale anomalous dispersion with heavy tails. Properties of four fractional-order advection–dispersion equation (fADE) models were analyzed and compared systematically, including the space fADEs with either maximally positive or negative skewness, the time fADE with a temporal fractional-derivative 0<γ<1$0<\gamma <1$, and the extension of the time fADE with 1<γ<2$1<\gamma <2$. Space fADEs describe the dependence of local concentration change on a wide range of spatial zones (i.e., the space nonlocality), while time fADEs describe dynamic mass exchange between mobile and multiple immobile phases and therefore record the temporal history of concentration “loading” (i.e., the time-nonlocality). We then applied the fADEs as models of anomalous dispersion to four extensively-studied, regional-scale, natural systems, including a hillslope composed of fractured soils, a river with simultaneous active flow zones and various dead-zones, a relatively homogeneous glaciofluvial aquifer dominated by stratified sand and gravel, and a highly heterogeneous alluvial aquifer containing both preferential flowpaths and abundant aquitards. We find that the anomalous dispersion observed at each site might not be characterized reasonably or sufficiently by previous studies. In particular, the use of the space fADE with less than maximally positive skewness implies a spatial dependence on downstream concentrations that may not be physically realistic for solute transport in watershed catchments and rivers (where the influence of dead-zones on solute transport can be described by a temporal, not spatial, fractional model). Field-scale transport studies show that large ranges of solute displacement can be described by a space nonlocal, fractional-derivative model, and long waiting times can be described efficiently by a time-nonlocal, fractional model. The unknown quantitative relationship between the nonlocal parameters and the heterogeneity, and the similarity in concentration profiles that are solutions to the different nonlocal transport models, all demonstrate the importance of distinguishing the representative nonlocality (time and/or space) for any given regional-scale anomalous dispersion process.  相似文献   

Erratum: Discriminant analysis for estimation of groundwater age from hydrochemistry and well construction: application to New Zealand aquifers     

Christopher J. Daughney  Uwe Morgenstern  Rob van der Raaij  Robert R. Reeves 《Hydrogeology Journal》2010,18(2):541-541

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Dust injection into the Martian atmosphere     

Douglas W. Johnson  Paul Harteck  Robert R. Reeves 《Icarus》1975,26(4):441-443

A mechanism for initiating global dust storms on Mars is proposed in which the diurnal variation of surface temperature results in the desorption of adsorbed CO₂, which under certain conditions can inject large amounts of fine (1–10 μm) dust into the atmosphere.  相似文献   

Estimating Rainfall Recharge and Soil Water Residence Times in Pukekohe, New Zealand, by Combining Geophysical, Chemical, and Isotopic Methods   总被引：1，自引：0，他引：1  

Michael R. Rosen  John Bright  Peter Carran  Michael K. Stewart  Robert Reeves 《Ground water》1999,37(6):836-844

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