3D seismic analysis of slope-confined canyons from the Plio–Pleistocene of the Ebro Continental Margin (Western Mediterranean)     

Claudia Bertoni  Joe Cartwright 《Basin Research》2005,17(1):43-62

This paper documents the importance of three‐dimensional (3D) seismic data for integrated stratigraphic–morphological analysis of slope systems. Furthermore, it contributes to the general understanding of the evolutionary mechanisms of slope‐confined submarine canyons on continental margins and their significance in a sequence stratigraphic framework. Recently acquired 3D seismic data from the Ebro Continental Margin (Western Mediterranean) have been used to study a series of remarkably well‐imaged submarine canyons in the Plio‐Pleistocene succession. Detailed mapping shows that these canyons are restricted to the slope, and thus can be compared with slope‐confined canyons observed on the present day seabed of many continental margins. The slope‐confined canyons are typically 0.5–2 km wide, 10–15 km long, and incise more than 50 m into the slope units. Their most striking characteristic is an upslope branching geometry in the head region involving up to three orders of bifurcation, with downslope development of a single incisional axis. The submarine canyons are characterized by a nested stacking pattern, undergoing alternating phases of cutting and filling. Limited parts of the upper and middle slope remain outside the canyon system, confined in sharp depositional ridges. The canyons are observed on closely spaced surfaces and exhibit a geometry that allowed the construction and discussion of a local sequence stratigraphic model for their evolution. In general, active incision of the canyons is observed at times throughout almost the entire cycle of base‐level change. However, erosional activity is more significant during the later stages of the relative sea level rise and the entire falling stage, with the timing of maximum erosion observed at the end of the cycle. The minimum erosional activity of the canyons is linked instead to the earliest part of the relative sea level rise.  相似文献   

Times of peak astronomical tides     

Richard D. Ray  David E. Cartwright 《Geophysical Journal International》2007,168(3):999-1004

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Realizing the Literate Traveller     

William E Cartwright  Bob Williams  Chris Pettit 《Transactions in GIS》2007,11(1):9-27

A current research project is addressing the problem of finding appropriate geographical information by developing a (geo)information realization resource based upon the concepts of the Literate Traveller. It has as its main goal to provide tools for geographical knowledge building and exploration, by providing conventional spatial information plus geographical interpretation and appreciation artifacts. These artifacts are delivered in an interactive multimedia environment. This research examines the formulation of an initial prototype component to assist in providing geographical knowledge. The prototype is based on a study site in Townsville, Australia, and is being used as a vehicle to explore enhanced spatial information provision through the use of rich media. The research examines new ways to prospect for, discover and disseminate spatial knowledge within an intelligence‐briefing context. The paper reports on the concepts behind the design of the application developed for the test site, and presents initial findings from the early evaluation of the prototype.  相似文献   

Extraction of the M2 ocean tide from SEASAT altimeter data     

P. L. Woodworth  D. E. Cartwright 《Geophysical Journal International》1986,84(2):227-255

Summary. Three complementary methods for the extraction of the M2 ocean tide using SEASAT altimetry are presented and compared. The first method (that developed by Cartwright & Alcock), which provides 'point measurements'of the tide at the crossovers of the SEASAT repeat orbit ground track, has been applied to a study of the tide in tropical ocean areas. The other two methods involve spatial expansions of M2 in terms of either surface spherical harmonics (in the case of the method developed by Mazzega) or Platzman normal modes of the world ocean. The results obtained by each method from only one month of SEASAT data reproduce many features of the tide represented in recent tidal models, and promise well for satellite altimetry as a future source of tidal knowledge.  相似文献   

Some experiments with 'orthotides'   总被引：1，自引：0，他引：1  

G. A. Alcock  D. E. Cartwright 《Geophysical Journal International》1978,54(3):681-696

Summary. Properties of the Groves & Reynolds 'orthotide' functions are explored in application to two typical sea-level series. Long-term fluctuations of their mean products prevent the direct application of simple methods of analysis, including the direct extraction of radiational tidal constants. Independence and stability of the orthoweights in the presence of radiational tides are demonstrated numerically. Orders 0 to 9 seem sufficient to define typical tidal properties, with the largest weights occurring at orders 0 to 5. The very simple procedure of converting orthoweights to admittances or harmonic constants is applied, with satisfactorily stable results.  相似文献   

Field-Scale Investigation of Infiltration Into a Compacted Soil Liner     

Samuel V. Panno  Beverly L. Herzog  Keros Cartwright  Kenneth R. Rehfeldt  Ivan G. Krapac  Bruce R. Hensel 《Ground water》1991,29(6):914-921

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Aquifer Transmissivity from Surficial Electrical Methods   总被引：7，自引：0，他引：7  

Paul C. Heigold  Robert H. Gilkeson  Keros Cartwright  Philip C. Reed 《Ground water》1979,17(4):338-345

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The variances of tidal harmonics     

Dr. David E. Cartwright  Mr. Muhammad Amin 《Ocean Dynamics》1986,39(6):235-253

Summary The variances, or squared standard errors, of estimates of tidal harmonic constants from analyses of a month or a year of tide-gauge data are analysed in terms of spectral properties of their noise continuum, modelled as exponential cuspsE ₁ superimposed on a smoothly monotonic non-tidal spectrumE ₀. Taking 5 representative stations, each with 19 years of data,E ₀ is evaluated from the inter-species noise levels, andE ₁ from the ratio of the variances from monthly and yearly analyses. It is shown that the cusps surrounding the diurnal tides are dominated byE ₀, whereas the more important semi-diurnal and higher species cusps are fitted by an exponential form forE ₁ with bandwidth of a few cycles per year. The variance ratios (monthly: yearly analyses) for diurnal harmonics are somewhat greater than the value expected for white noise, partly because of residual tidal lines in the monthly analyses which cannot be related to the major constituents. The corresponding ratios for semi-diurnal and higher species harmonics are less than the white noise value, on account of the cusps. The standard errors of yearly estimates of the larger tidal constituents may be predicted as proportional to their mean amplitude, as a very rough guide, in the approximate ratio of 11 mm/m.Zusammenfassung Die Varianzen — oder Quadrate der Standardabweichungen — der Abschätzungen von harmonischen Gezeitenkonstanten aus Analysen monatlicher bzw. jährlicher Pegelbeobachtungsreihen werden nach den spektralen Eigenschaften ihres Rauschens analysiert. Dieses wird durch exponentielle SpitzenE ₁, die einem glatten monotonen NichtgezeitenspektrumE ₀ überlagert sind, dargestellt. Anhand 19 jähriger Beobachtungsreihen von 5 repräsentativen Stationen wirdE ₀ aus dem Hintergrundrauschen ermittelt undE ₁ aus dem Verhältnis der Varianzen aus monatlichen und jährlichen Analysen. Es wird gezeigt, daß die Spitzen im Bereich der eintägigen Tiden vonE ₀ beherrscht werden, die wichtigeren Spitzen der halbtägigen Tiden und der Tiden höherer Ordnung werden dagegen durch einen exponentiellen Ausdruck fürE ₁ mit einer Bandbreite von einigen Perioden pro Jahr angenähert. Die Verhältnisse der Varianzen (aus monatlichen zu jährlichen Analysen) für eintägige Harmonische sind etwas größer als der Wert, den man für weißes Rauschen erwarten würde, zum Teil deshalb, weil bei monatlichen Analysen nicht alle Tiden den Hauptkomponenten zugeordnet werden können. Die entsprechenden Verhältnisse für halbtägige und höhere Harmonische sind wegen der Spitzen kleiner als der Wert für weißes Rauschen. Die Standardabweichungen der jährlichen Abschätzungen größerer Gezeitenkomponenten können grob als proportional zu ihrer mittleren Amplitude geschätzt werden mit einem Verhältnis von etwa 11 mm/m.

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Varianzen harmonischer Gezeitenkonstanten

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Les variances des constantes harmoniques de marée

Résumé Les variances, ou carrés des écarts types, des estimations de constantes harmoniques de marée provenant d'analyses portant sur un mois ou une année de données marégraphiques sont analysées en terme de propriétés spectrales de leur continuum de bruit, modélisé comme des pics exponentielsE ₁ superposés à un spectre ne provenant pas de la marée sensiblement monotoneE ₀. Si l'on prend 5 stations représentatives, chacune comportant 19 années d'observations,E ₀ est évalué par les niveaux de bruit inter-espèces, etE ₁ par le rapport des variances provenant des analyses mensuelles et annuelles. On montre que les pics entourant les marées de type diurne sont dominés parE ₀, alors que les pics plus importants de type semidiurne et d'espèces supérieures sont bien approximés par une forme exponentielle pourE ₁ avec une largeur de bande de quelques cycles par an. Les rapports de variance (analyses mensuelles/annuelles) des harmoniques diurnes sont un peu plus grands que la valeur attendue pour le bruit blanc, partiellement à cause des composantes de marée résiduelles dans les analyses mensuelles qui ne peuvent pas être rattachées aux composantes majeures. En raison des pics, les rapports correspondants pour les harmoniques des espèces supérieures et semi-diurnes sont inférieures à la valeur du bruit blanc. Les écarts types des valeurs estimées annuelles des composantes principales de marée peuvent être définis grossièrement comme proportionnels à leur amplitude moyenne, en admettant un rapport de proportionnalité approximatif de 11 mm/m.

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Volumetric contraction during the compaction of mudrocks: a mechanism for the development of regional-scale polygonal fault systems   总被引：10，自引：1，他引：10  

J. A. Cartwright  & L. Lonergan 《Basin Research》1996,8(2):183-193

This paper describes the geometry and strain characteristics of a complex system of small extensional faults affecting Lower Tertiary mudrock-dominated successions throughout the central North Sea Basin. Structural mapping using three-dimensional seismic data shows that the fault trace geometry is polygonal. The shallow origin of the faults is confirmed by the recognition of growth sequences developed in their hangingwalls. Line balancing techniques were used to measure the extensional strain in two survey areas. This was found to be radially isotropic in the map plane. Extension in any line of section was found to vary from 6 to 19%. Since the deformation is clearly layer-bound and there is no evidence for displacement transfer to basement structures, it is argued that the only explanation for this apparent extension is by layer-parallel volumetric contraction. This is believed to occur in response to fluid expulsion from the mudrocks during early compaction. The conditions for failure may be achieved through increased pore fluid pressure or through tensile stresses generated as a result of pore fluid loss, or a combination of these two processes. Far-field tectonic stresses are not considered to be responsible for the formation of this fault system.  相似文献   

Permeability generation and resetting of tracers during metamorphic fluid flow: implications for advection-dispersion models     

Ian Cartwright 《Contributions to Mineralogy and Petrology》1997,129(2-3):198-208

Advection-dispersion fluid flow models implicitly assume that the infiltrating fluid flows through an already fluid-saturated medium. However, whether rocks contain a fluid depends on their reaction history, and whether any initial fluid escapes. The behaviour of different rocks may be illustrated using hypothetical marble compositions. Marbles with diverse chemistries (e.g. calcite + dolomite + quartz) are relatively reactive, and will generally produce a fluid during heating. By contrast, marbles with more restricted chemistries (e.g. calcite + quartz or calcite-only) may not. If the rock is not fluid bearing when fluid infiltration commences, mineralogical reactions may produce a reaction-enhanced permeability in calcite + dolomite + quartz or calcite + quartz, but not in calcite-only marbles. The permeability production controls the pattern of mineralogical, isotopic, and geochemical resetting during fluid flow. Tracers retarded behind the mineralogical fronts will probably be reset as predicted by the advection-dispersion models; however, tracers that are expected to be reset ahead of the mineralogical fronts cannot progress beyond the permeability generating reaction. In the case of very unreactive lithologies (e.g. pure calcite marbles, cherts, and quartzites), the first reaction to affect the rocks may be a metasomatic one ahead of which there is little pervasive resetting of any tracer. Centimetre-scale layering may lead to the formation of self-perpetuating fluid channels in rocks that are not fluid saturated due to the juxtaposition of reactants. Such layered rocks may show patterns of mineralogical resetting that are not predicted by advection-dispersion models. Patterns of mineralogical and isotopic resetting in marbles from a number of terrains, for example: Chillagoe, Marulan South, Reynolds Range (Australia); Adirondack Mountains, Old Woman Mountains, Notch Peak (USA); and Stephen Cross Quarry (Canada) vary as predicted by these models. Received: 3 February 1997 / Accepted: 26 June 1997  相似文献