Theoretical grain-size thresholds and their application to accurate methods for paleointensity determination     

S.K. Banerjee  R.F. Butler 《Physics of the Earth and Planetary Interiors》1977,13(4):268-271

New values of critical grain-size thresholds, d_s and d₀, for magnetite and Fe have been obtained using a rigorous theoretical approach. The temperature dependence of these thresholds is interesting in that they point up the existence of certain grains which, when cooled from above their blocking temperature, pass sequentially through the following magnetization states: superparamagnetic→single-domain→non-uniform magnetization. Such grains will yield correct paleointensities by the Wilson or Shaw method but not by the well-known method due to Thellier and Thellier.  相似文献   

Paleomagnetic evidence for Jurassic deformation of the McCoy Mountains Formation,southeastern California and southwestern Arizona     

Lucy E. Harding  Robert F. Butler  Peter J. Coney 《Earth and Planetary Science Letters》1983,62(1):104-114

The Mesozoic McCoy Mountains Formation is a 7.3-km-thick deformed clastic sequence exposed in six mountain ranges in southeastern California and southwestern Arizona. Interbedded with Jurassic volcanic rocks at its base, the McCoy Mountains Formation had been assigned a Cretaceous age based upon fossil angiosperm wood found in the upper third of the section. Characteristic natural remanent magnetism (NRM) from 145 oriented samples from 18 sites within the sedimentary terrane yield an in situ mean direction:I = 20.6°, D = 335.1°, α₉₅ = 7.7° (uncorrected for structural tilting). Opaque mineralogy and a failed fold test indicate that the NRM is a chemical remanence acquired post-folding. The paleomagnetic pole position calculated from the in situ mean direction falls adjacent to poles from the Summerville Formation and Canelo Hills Volcanics. We interpret these data to indicate that deformation, mild metamorphism, and resultant magnetization of the McCoy Mountains Formation occurred during Jurassic time. It is suggested that the McCoy Mountains Formation and underlying Jurassic volcanics were deposited adjacent to, and then deformed between, the North American craton and an outlying allochthonous terrane during Jurassic time.  相似文献   

The effects of closure on the moments of a distribution   总被引：1，自引：0，他引：1  

John C. Butler 《Mathematical Geology》1979,11(1):75-84

When percentages are formed from uncorrelated, normally distributed parent variables the moments of the percentage distribution may differ considerably from those of the parents. Equations can be derived which enable the approximation of the moments of a percentage variable in terms of the moments of the parent distribution, the row sum statistics, and the correlation between a part of a sum and the sum (the part-whole correlation). If the part-whole correlation is negative the mean and variance of the percentage are increased (relative to the means and variances of those variables with a positive part-whole correlation) and the percentage variable will exhibit a positive skewness. If the part-whole correlation is positive the percentage variable will be negatively skewed if, and only if, the part-whole correlation is greater than the ratio of the coefficient of variation of the row sum (T) to the coefficient of variation of the parent variable. The kurtosis of the percentage variable must be greater than that of the parent variable regardless of the sign of the part-whole correlation. It is obvious that the interpretation or explanation of the distribution of a percentage variable must include an assessment of the effects of percentage formation. However, at the present time the isolation of the percentage effect appears to be impossible unless the parent data set is available.  相似文献   

Input sensitivity study of a stratospheric photochemistry model     

Dixon M. Butler 《Pure and Applied Geophysics》1978,117(3):430-435

A general technique for calculating the sensitivities, uncertainties and overall imprecision of a model to a set of input parameters is described and applied to the calculation of CFM induced stratospheric ozone depletion. The input data set used is reaction rates and the technique highlights those that most need further study in the laboratory. The convolution of individual uncertainties to obtain an overall imprecision gives good agreement with the results of Monte-Carlo calculations using the same model.A paper presented at the IAGA/IAMAP Joint Assembly at Seattle, Washington, USA. 22 August–3 September 1977.  相似文献   

Association announcement     

John C. Butler 《Mathematical Geosciences》1996,28(3):379-381

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Book review     

D. F. Watson  John C. Butler 《Mathematical Geology》1988,20(3):277-281

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Concentration and size variation of condensation nuclei at Mawson,Antarctica     

J. L. Gras  A. Adriaansen  R. Butler  B. Jarvis  P. Magill  B. Lingen 《Journal of Atmospheric Chemistry》1985,3(1):93-106

Condensation nucleus (CN) concentrations have been measured at Mawson (67.6°S, 62.9°E) since mid 1981. Weekly median concentrations have an annual cycle with a maximum of around 300 to 400 cm^-3 in summer and a minimum of a few tens of particles per cm^-3 in winter. In this respect Mawson behaves very much like an Antarctic continental location. Preliminary measurements of the size distribution of CN particles taken over a nine month period suggest a seasonal change in typical particle radius from around 0.01 m in winter to around 0.04 m in summer. Diurnal variation in the CN concentration is generally very weak and does not show any systematic relation to the pronounced diurnal variation in wind-speed at Mawson.Department of Science, Antarctic Division  相似文献   

The restoration of thrust systems and displacement continuity around the Mont Blanc massif,NW external Alpine thrust belt   总被引：1，自引：0，他引：1  

Robert W.H. Butler 《Journal of Structural Geology》1985,7(5):569-582

Foreland-propagating external thrust belts may be considered as essentially plane strain phenomena so that displacements can be correlated throughout their linked, three-dimensional fault geometry. This approach has been applied to part of the northwest external French-Swiss Alps, around the Mont Blanc basement massif. Imbricates of basement and cover sequences on the SW margin of this massif restore to a width in excess of 77 km with an implicit shortening of at least 67 km. These displacements can be correlated with those in the neighbouring Helvetic nappes by transferring movements, via lateral branch lines, onto the Mont Blanc thrust. By reappraising thrust geometries, the Helvetic/Ultrahelvetic nappe complex has been restored to a width of 114 km to the ESE of the Aiguilles Rouges basement massif. Displacements on the internal (SE) margin of the Mont Blanc massif, estimated by balanced sections and a restoration of the Ultrahelvetic klippen in the sub-alps, exceed 59 km. Thrust continuity, incorporating the restorations of nappes and imbricate geometries around the Mont Blanc massif, is illustrated on a crude, restored branch-line map which also serves as a preliminary palaeogeographic reconstruction. External thrust systems, to the east of the external Belledonne/Aiguilles Rouges massif, restore to a width of at least 140 km in the footwall to the Frontal Pennine thrust.  相似文献   

Optimal Siting of Artificial Recharge: An Analysis of Objective Functions     

Cijun Li  Jean M. Bahr  Eric G. Reichard  James J. Butler  Jr.  Irwin Remson 《Ground water》1987,25(2):141-150

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Direct-Push Electrical Conductivity Logging for High-Resolution Hydrostratigraphic Characterization   总被引：3，自引：0，他引：3  

M.K. Schulmeister  J.J. Butler Jr.    J.M. Healey  L. Zheng  D.A. Wysocki  G.W. McCall 《Ground Water Monitoring & Remediation》2003,23(3):52-62

Fine-scale hydrostratigraphic features often play a critical role in controlling ground water flow and contaminant transport. Unfortunately, many conventional drilling- and geophysics-based approaches are rarely capable of describing these features at the level of detail needed for contaminant predictions and remediation designs. Previous work has shown that direct-push electrical conductivity (EC) logging can provide information about site hydrostratigraphy at a scale of relevance for contaminant transport investigations in many unconsolidated settings. In this study, we evaluate the resolution and quality of that information at a well-studied research site that is underlain by highly stratified alluvial sediments. Geologic and hydrologic data, conventional geophysical logs, and particle-size analyses are used to demonstrate the capability of direct-push EC logging for the delineation of fine-scale hydrostratigraphic features in saturated unconsolidated formations. When variations in pore-fluid chemistry are small, the electrical conductivity of saturated media is primarily a function of clay content, and hydrostratigraphic features can be described at a level of detail (<2.5 cm in thickness) that has not previously been possible in the absence of continuous cores. Series of direct-push EC logs can be used to map the lateral continuity of layers with non-negligible clay content and to develop important new insights into flow and transport at a site. However, in sand and gravel intervals with negligible clay, EC logging provides little information about hydrostratigraphic features. As with all electrical logging methods, some site-specific information about the relative importance of fluid and sediment contributions to electrical conductivity is needed. Ongoing research is directed at developing direct-push methods that allow EC logging, water sampling, and hydraulic testing to be done concurrently.  相似文献