Forward modelling of porosity and pore pressure evolution in sedimentary basins   总被引：4，自引：0，他引：4  

D. M. Audet  J. D. C. McConnell 《Basin Research》1992,4(2):147-162

The gravitational compaction of sediments is an important process in forward basin modelling. This paper presents a mathematical model for the one-dimensional compaction of an accreting layer of argillaceous sediments. Realistic constitutive laws for the clay compressibility and the clay permeability, based on soil mechanics tests, were incorporated into the model. The governing equations were put in dimensionless form and the extent of abnormal pore fluid pressure development was found to depend on the sedimentation parameter, a dimensionless group representing the ratio of the sediment hydraulic conductivity to the sediment accumulation rate. The effects of clay compressibility were studied and highly colloidal clays such as montmorillonite developed higher overpressures than less compressible materials. The results also showed that overpressuring developed in shales for cases in which the clay permeability did not go to zero in the limit of zero porosity. Linear models based on simplifying assumptions inappropriate for sedimentary basins were found to give significantly different estimates for the conditions leading to overpressuring. Using reasonable parameters, the model adequately reproduced porosity and pore pressure profiles measured in the sand-shale sequences of the South Caspian Sea.  相似文献   

FOREIGN OWNERSHIP AND TRADE OF UNITED STATES HIGH-TECHNOLOGY MANUFACTURING     

James E. McConnell 《The Professional geographer》1981,33(1):63-71

Analysis of recent trends in the foreign ownership and trade of United States high-technology manufactures reveals that foreign-based corporations are intensifying their direct investments in United States technology-intensive industries, that the locations of foreign-owned subsidiaries are becoming increasingly dispered thoughout the country, and that the industry-level concentration of foreign direct investments is highly correlated with the specialization of United States high-technology imports from the principal investing countries.  相似文献   

Biostratigraphy and depositional environment of algal stromatolites from the Mescal Limestone (Proterozoic) of central Arizona     

Robert L. McConnell 《Precambrian Research》1975,2(3):317-328

The Apache Group of central Arizona is subdivided into, from base upward, the Pioneer Formation, the Dripping Spring Quartzite and the Mescal Limestone. Radiometric age determinations by Silver, and Livingston and Damon indicate an age of 1.2–1.4 billion years. Within the Mescal Limestone, algal stromatolites form a conspicuous biostrome, commonly 20–25 m thick. The basal 1–5 m of the biostrome consists of up to three zones of digitate stromatolites, which often form discrete bush-like bioherms. These forms are interpreted as Baicalia baicalica, Parmites sp. and Tungussia sp.; the latter form previously reported by Cloud and Semikhatov (1969). The form Parmites is interpreted as a modification of digitate stromatolites probably by decrease in current velocity within the shallow marine environment, which allowed discrete heads to coalesce. Basal digitate forms are replaced upward in the biostrome by domal and undulatory laminated (stratiform) stromatolites, interpreted to represent gradual upward shoaling, with lower intertidal and subtidal forms (digitate morphology) being replaced by upper intertidal and possibly supratidal forms (stratiform types).The digitate form B. baicalica is suggested by Soviet workers to be indicative of Middle Riphean time (1350-950 m.y.). While many empirical data suggest the possibility of gross subdivision of Late Proterozoic time on the basis of algal stromatolite “zones”, the intercontinental applicability and the ultimate validity of this concept in unresolved.  相似文献   

OROGENIC ANDESITES AND CRUSTAL GROWTH,edited by A. Gómez‐Tuena,S.M. Straub and G.F. Zellmer. Geological Society,London, Special Publications, 385, 2014. No. of pages: ix+414. Price: £125‐00. ISBN 978‐1‐86239‐369‐1 (hardback).     

Brian McConnell 《Geological Journal》2016,51(1):161-161

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Canadian middle atmosphere model: Preliminary results from the chemical transport module     

J. de Grandpré  J.W. Sandilands  J.C. McConnell  S.R. Beagley  P.C. Croteau  M.Y. Danilin 《大气与海洋》2013,51(4):385-431

Abstract

An important objective of middle atmosphere global climate modelling is the development of the capability of predicting the response of the middle atmosphere to natural or anthropogenic perturbations. To achieve this, a comprehensive chemistry package interactively coupled with radiative and dynamical modules is required. This paper presents preliminary results obtained with a photochemistry module which has been incorporated in the Canadian Middle Atmosphere Model (CMAM). The module contains 42 species including necessary oxygen, hydrogen, nitrogen, chlorine, bromine and methane oxidation cycle species. Photochemical balance equations are solved on‐line throughout the middle atmosphere at every dynamical time step. A full diurnal cycle is simulated with photolysis rates provided by a look‐up table. The chemistry solver is a mass conserving, fully implicit, backward difference scheme which currently uses less than 10% of the GCM run time. We present the results obtained from short integrations and compare them with UARS measurements. The model ozone distribution appears in quantitative agreement with observations showing peak values near 10 ppmv and confined to the 35‐km region. The abundance of nitrogen, chlorine, bromine oxides and their respective contributions to the overall ozone budget is realistic. The study illustrates the capability of the model to simulate middle atmosphere photochemistry for the disparate conditions occurring throughout the region.  相似文献   

A New look at the ionosphere of Jupiter in light of the UVS occultation results     

J.C. McConnell  J.B. Holberg  G.R. Smith  B.R. Sandel  D.E. Shemansky  A.L. Broadfoot 《Planetary and Space Science》1982,30(2):151-167

Simple photochemical models cannot reconcile Jupiter's ionospheric electron density profiles with the observed neutral atmosphere. The location of the peak electron density predicted when the neutral atmosphere determined by theVoyager Ultraviolet Spectrometer is combined with simple models falls about 1000km lower than the peak determined by radio occultation. The locations and magnitudes of the peaks in electron density can be accounted for by including the effects of vertical transport of ions in the ionospheric models. This vertical transport may be induced by meridional winds in the neutral atmosphere or external electric fields. It is probable that precipitating particles and an altitude-variable H₂ vibrational temperature play important roles in determining the character of the iono?phere. In view of the complex relationship between the ionosphere and neutral atmosphere, an attempt to infer one from the other cannot succeed. However, combining independent information on the two leads to new insights into the coupling of the neutral atmosphere, the ionosphere and the magnetosphere.  相似文献   

Airglow on Mars: Some model expectations for the OH Meinel bands and the O₂ IR atmospheric band     

A. García Muñoz  J.C. McConnell  S.M.L. Melo 《Icarus》2005,176(1):75-95

This work presents model calculations of the diurnal airglow emissions from the OH Meinel bands and the O₂ IR atmospheric band in the neutral atmosphere of Mars. A time-dependent photochemical model of the lower atmosphere below 80 km has been developed for this purpose. Special emphasis is placed on the nightglow emissions because of their potential to characterize the atomic oxygen profile in the 50-80 km region. Unlike on Earth, the OH Meinel emission rates are very sensitive to the details of the vibrational relaxation pathway. In the sudden death and collisional cascade limits, the maximum OH Meinel column intensities for emissions originating from a fixed upper vibrational level are calculated to be about 300 R, for transitions v^′=9→v^′?8, and 15,000 R, for transitions v^′=1→v^′=0, respectively. During the daytime the 1.27 μm emission from O₂(), primarily formed from ozone photodissociation, is of the order of MegaRayleighs (MR). Due to the long radiative lifetime of O₂(), a luminescent remnant of the dayglow extends to the dark side for about two hours. At night, excited molecular oxygen is expected to be produced through the three body reaction O + O + CO₂. The column emission of this nighttime component of the airglow is estimated to amount to 25 kR. Both nightglow emissions, from the OH Meinel bands and the O₂ IR atmospheric band, overlap in the 50-80 km region. Photodissociation of CO₂ in the upper atmosphere and the subsequent transport of the atomic oxygen produced to the emitting layer are revealed as key factors in the nightglow emissions from these systems. The Mars 5 upper constraint for the product [H][O₃] is revised on the basis of more recent values for the emission probabilities and collisional deactivation coefficients.  相似文献   

Broad-band bottom forward loss and backscattering off San Diego     

McConnell  S.O. DeProspo  D.F. 《Oceanic Engineering, IEEE Journal of》1994,19(3):360-367

Broad-band forward loss and backscattering measurements were made at low to moderate grazing angles in shallow water off San Diego using pulses extending from 1 to 6 kHz in bandwidth. For forward bounce measurements, these large bandwidths achieved time resolutions as small as 0.25 ms, and revealed fine-scale subbottom layering with separations down to approximately 50 cm. The forward loss values show large fluctuations (>10 dB) over translation distances of 20-50 m in some cases or between two measurement runs separated by a few hundred meters in other cases. This observation, along with associated variations in the extent and number of subbottom arrivals, indicates a distinct patchiness in surficial sediment type. Previous measurements made in nearby locales also evidenced strong variations in bottom loss, but lacked the spatial resolution to discern interface reflections from subbottom contributions. Broad-band backscattering strength measured at 20-40° grazing was quite homogeneous over the entire region, probably because the critical angle is below 20°, as inferred from forward loss measurements. Theory suggests that scattering at angles above critical is from subbottom inhomogeneities rather than boundary roughness. The grazing angle and frequency dependence of these backscattering data are relatively weak  相似文献   

The Bad Step Tuff: a lava-like rheomorphic ignimbrite in a calc-alkaline piecemeal caldera,English Lake District   总被引：2，自引：2，他引：0  

Michael J Branney  B Peter Kokelaar  Brian J McConnell 《Bulletin of Volcanology》1992,54(3):187-199

Lava-like tuffs are lithologically indistinguishable from lavas, and form part of a temperature-and composition-controlled continuum from low-grade tuffs (which are non-welded or slightly welded), through high-grade (densely welded) tuffs, extremely high-grade tuffs (which may be agglutinated right to their upper and lower contacts), to spatter-fed lava flows. In some high-grade tuffs, a component of nonparticulate flow may postdate emplacement and deposition, but in extremely high-grade tuffs non-particulate deformation normally occurs during emplacement and deposition. In such cases, syn-depositional non-particulate deformation (previously called primary welding) and non-particulate slumping (previously called secondary flowage) processes overlap and are continuous, one into the other, so that distinction between them and their resultant structures is unrealistic and inapplicable. Therefore the term rheomorphism should be used to embrace all types of non-particulate flow. The Bad Step Tuff is the most lava-like of a sequence of rheomorphic calc-alkaline rhyolitic ignimbrites emplaced during a climactic caldera-forming eruption episode in the English Lake District. It is a ponded sheet, 40 to 400 m thick, which comprises a basal crudely stratified heterolithic breccia, a thick flow-laminated and locally vesicular central part, which beomes increasingly flow-folded upwards, and an upper autobreccia. Despite an absence of vitroclastic textures within the main laminated part, field relations show it to be a tuff. Diagnostic criteria are (1) a gradation, within a lithophysal zone, from unambiguous vitroclastic matrix of the basal lithic breccia upwards into the central flow-laminated tuff; (2) only rate autobreccia at the base of the sheet but ubiquitous autobreccia at the top of the sheet; and (3) close textural similarity with localized, intensely rheomorphic parts of associated ignimbrites that widely display unequivocal vitroclastic textures where their rheomorphism is less marked. The extremely high-grade character of the Bad Step Tuff may reflect its proximal setting in a piecemeal-type caldera. High emplacement temperatures resulted from high-rate but low-velocity vent emission from fissures along numerous cross-cutting calderafloor faults, producing very low boil over eruption columns and proximal ponding.  相似文献   

Evolution of taphrogenic lineaments in continental platforms     

Dr. R. B. McConnell 《International Journal of Earth Sciences》1974,63(2):389-430

The Rift System of eastern Africa is taken as a basis for an enquiry into the nature and age of taphrogenic lineaments in continental platforms. Special emphasis is placed on those segments in which the early Precambrian infrastructure has been exposed by continued uplift and deep erosion, and the evidence points to a genetic association of the Neogene graben faults with dislocation zones originating in the Precambrian and affecting the deep lithosphere. These proto-rift dislocations were repeatedly rejuvenated during successive tectonothermal cycles, showing blasto-mylonites, flaser gneisses and migmatites according to tectonic depth, and culminating in brittle surface faulting. A fundamental difference between taphrogenic and orogenic processes is emphasized by the oblique crossing of younger fold belts by the lineaments. Geophysical and other evidence from Africa confirms data from the Rhinegraben and Lake Baikal showing that continental rift systems are underlain by zones of high heat flow and intrusions of anomalous low density mantle rock (penetrative convection), producing structures comparable with those beneath mid-ocean ridges. Geological mapping, however, proves that dilation is minimal and that rift volcanism is of continental type and, with small exceptions, is limited to a sector extending south from the Afar triangle in Ethiopia through Kenya. It is suggested that sea-floor spreading in the African rifts was prevented by their geotectonic position, and that the continent was under pressure from the active mid-ocean ridges surrounding it on three sides. Evidence is described from East Africa, and from the West African and Guiana Shields, indicating that continental lineaments extended into the ancestral rifts of sea-floor spreading. It is concluded that in the lithosphere, above the mantle lowvelocity zone, deep criss-crossing lineaments of ancient origin exist, of which some served in Precambrian times as dislocation zones and channels for penetrative convection and were thus pre-conditioned for periodic tectonothermal rejuvenation. Certain segments of these channels have been selected by the powerful rising mantle dorsals associated with sea-floor spreading, and thus play a part in plate tectonics.  相似文献