Four barriers to the development of effective exploratory visualisation tools for the geosciences     

MARK GAHEGAN 《International journal of geographical information science》2013,27(4):289-309

This paper outlines four specific problems that appear to represent considerable obstacles to the development of visualisation strategies for use within the domain of geography and the Earth sciences. These are: (1) the speed of graphical rendering, (2) the management of perceptual anomalies due to visual combination effects, (3) the vast range of potential approaches and mappings (the complexity of the visual assignment process), and (4) the orientation of the user into an artificial or virtual reality. Each problem is discussed in terms of the visualisation of geographical data for the purpose of exploratory visual analysis. The specific underlying research issues and questions are described, with particular emphasis to how these relate to the geographical domain. Where possible, some potential solutions are suggested. Specific examples of geographical data visualisation are given to substantiate the arguments presented. The discussion highlights the need for further research in a number of key areas, and stresses the weaknesses of current visualisation theory and technology when applied to non-trivial geographical datasets.  相似文献   

Host rock dolomitization and secondary porosity development in the Upper Devonian Cairn Formation of the Fairholme carbonate complex (South‐west Alberta,Canadian Rockies): diagenesis and geochemical modelling     

VEERLE VANDEGINSTE  RUDY SWENNEN  MARK H. REED  ROB M. ELLAM  KIRK OSADETZ  FRANÇOIS ROURE 《Sedimentology》2009,56(7):2044-2060

The Upper Devonian carbonate reefs in West‐central Alberta are important petroleum reservoirs that are well‐known for their extensive secondary porosity. An outcrop analogue study indicates that an early matrix‐selective dolomitization event occurred which is characterized by a major Late Devonian sea water component with increased salinity because of evaporation. It is interpreted that the matrix (replacive) dolomite formed during the Famennian as the result of a combination of both seepage and latent reflux dolomitization, although an additional type or overprinting of later intermediate burial dolomitization cannot be excluded. Formation of the moulds is attributed mainly to the dissolution of undolomitized fossil cores, most typically stromatoporoids. Geochemical modelling indicates that carboxylic acid fluids have the highest potential for dissolving residual calcite in this case. Geochemical models consistent with this analysis and interpretations can reproduce the secondary porosity and suggest a viable dolomitization process for the localities studied.  相似文献   

USE OF BOMB-¹⁴C TO INVESTIGATE THE GROWTH AND CARBON TURNOVER RATES OF A CRUSTOSE LICHEN     

BY MARK H. GARNETT  TOM BRADWELL 《Geografiska Annaler: Series A, Physical Geography》2010,92(1):53-63

The reliability of lichenometric dating is dependent on a good understanding of lichen growth rates. The growth rate of lichens can be determined from direct measurement of growing lichens or indirect methods by measuring lichens growing on surfaces of known age, although there are limitations to both approaches. Radiocarbon (¹⁴C) analysis has previously been used in only a handful of studies to determine lichen growth rates of two species from a small area of North America. These studies have produced mixed results; a small amount of carbon turnover appears to occur in one of the species ( Caloplaca spp.) previously investigated introducing uncertainty in the growth rate, while much higher carbon cycling occurred in another ( Rhizocarpon geographicum ), making the ¹⁴C approach unsuitable for estimating growth rates in the species most commonly used in lichenometric dating. We investigated the use of bomb-¹⁴C analysis to determine the growth rate of a different crustose species ( Pertusaria pseudocorallina ) common to Northern Europe. ¹⁴C-based growth rates were considerably higher than growth rates of morphologically similar species based on direct measurement made at locations nearby and elsewhere in the UK. This observation strongly suggests that a degree of carbon turnover probably occurs in Pertusaria pseudocorallina , and that bomb-¹⁴C analysis alone cannot be used to determine lichen age or absolute growth rates in this lichen species.  相似文献   

Carbon cycle studies based on the distribution of O₂ in air   总被引：1，自引：1，他引：0  

MICHAEL L. BENDER  MARK O. BATTLE 《Tellus. Series B, Chemical and physical meteorology》1999,51(2):165-169

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The type section of the Vikinghôgda Formation: a new Lower Triassic unit in central and eastern Svalbard     

ATLE MØRK  GEIR ELVEBAKK  ARNE W. FORSBERG  MARK W. HOUNSLOW.  HANS ARNE NAKREM.  JORUNN OS VIGRAN  WOLFGANG WEITSCHAT 《Polar research》1999,18(1):51-82

The Vikinghøgda Formation (250 m) is defined with a stratotype in Deltadalen-Vikinghøgda in central Spitsbergen. The Vikinghøgda Formation replaces the Vardebukta and Sticky Keep Formations of Buchan et al. (1965) and the lower part of the Barentsøya Formation of Lock et al. (1978) as extended geographically by Mørk, Knarud et al. (1982) in central Spitsbergen, Barentsøya and Edgeøya. The formation consists of three member: the Deltadalen Member (composed of mudstones with sandstones and siltstones), the Lusitaniadalen Member (dominated by mudstones with thin siltstone beds and some limestone concretions) and the Vendomdalen Member (composed of dark shales with dolomite interbeds and nodules). The Lusitaniadalen and Vendomdalen members replace the former Sticky Keep Formation/ Member in the siirne areu. The Vikinghøda Formation can be followed through central and eastern Spitsbergen to Barentøya and Edgeøya and includes all sediments between the chert-rich Kapp Starostin Formation (Permian) and the organic-rich shales of the Botneheia Formation (Middle Triassic). The subdivision into three members is also reflected in the organic carbon content and palynofacies. Upwards. each succeeding member becomes more distal, organic-rich and oil-prone than the one below.
The Vikinghøda Formation is well-dated by six ammonoid zones. although the transitional beds between the Deltadalen and Lusitaniadalen members lack age diagnostic macrofossils. Corresponding palynozonation and magnetustratigraphy have also been determined. The overall stratigraphical development correlates well with other key Triassic areas in the Arctic, although intervals in the late Dienerian and early Smithian may be condensed or missing.  相似文献   

A Crustal Progenitor for the Intrusive Anorthosite--Charnockite Kindred of the Cupriferous Koperberg Suite, O'okiep District, Namaqualand, South Africa; New Isotope Data for the Country Rocks and the Intrusives     

CLIFFORD  TOM N.; BARTON  ERIKA S.; RETIEF  EDWARD A.; REX  DAVID C.; FANNING  C. MARK 《Journal of Petrology》1995,36(1):231-258

The Koperberg Suite comprises some 1700 small bodies of intrusiverocks largely composed of andesine anorthosite, biotite diorite,and leuconorite, norite and melanorite-hypersthenite; 30 mineshave been established in the O'okiep District in the cupriferousrocks of this anorthosite-charnockite kindred. The suite isintrusive into a sequence of granite gneiss and metavolcanicand metasedimentary rocks, and intrusive granite, that wereelevated to the granulite fades of regional metamorphism.TheSm-Nd model ages for the country rocks and the Koperberg Suiteare all 1700 Ma (T_CHUR) and 2000 Ma (T_DM) supporting a majorcrustforming event in this portion of Namaqualand at the endof Lower Proterozoic times. The granulite fades metamorphismin the O'okiep District is recorded by a Rb-Sr isochron ageof 1223 48 Ma on the Nababeep Granite Gneiss, and by (1197 15)-Ma-old inherited cores of zircons in the Koperberg Suite.The time of intrusion of the Concordia and Rietberg Granitesis believed to be reflected by their Rb-Sr whole-rock age of1105 24 Ma. The mean U-Pb age of 1029 10 Ma on individualzircon grains and zircon rims from the Koperberg Suite recordsthe time of its intrusion, and this is supported by the Sm-Ndwhole-rock age of 1022 42 Ma for the suite. Subsequent coolingand reheating events are recorded by the Ar-Ar ages of 800–850Ma for the Koperberg Suite, and of 500–550 Ma for thesuite and certain country rocks, respectively.An Nd value of-7,and its volume and composition, suggest a crustal-melt sourcefor the intrusive Concordia Granite. Moreover, the age-correctedhigh l_Sr (07061-07272) and low Nd (-9), and the high µ₂(101), that characterize the Koperberg Suite also imply a crustalsource, and a model is presented for the generation of the majorpart of the suite by partial melting of granulites of overallintermediate (diorite) composition in the lower crust. Corresponding author  相似文献   

Petrology of Upper Amphibolite Facies Marbles from the East Humboldt Range, Nevada, USA; Evidence for High-Temperature, Retrograde, Hydrous Volatile Fluxes at Mid-Crustal Levels     

PETERS  MARK T.; WICKHAM  STEPHEN M. 《Journal of Petrology》1994,35(1):205-238

Petrographic and petrologic investigations of upper amphibolitefacies metacarbonates from the East Humboldt Range core complex,Nevada, provide important constraints on P-T-X_CO2 conditionsand fluid flow during metamorphism. Three marble assemblagesare observed [(1)dol+cc+bt+cpx+q+ruscapkspamph; (2) cc+bt+cpx+plag+q+sphscapksp;(3) cc+cpx+plag+q+sphscapksp], all of which equilibrated withrelatively CO₂-rich fluid compositions, at P-T conditions of6 kbar and 600–750C. The most recent equilibration eventis recorded in some calcsilicate gneisses where retrograde amphiboleand epidotegarnet replace clinopyroxene and plagioclase, respectively.This is attributed to infiltration of H₂O-rich fluids at and/orafter peak metamorphic temperatures, which continued as therocks were cooled and rapidly uplifted after a Tertiary extension-relatedheating event. Likely sources for the retrograde fluids are the abundant pegmatiticleucogranites in the area. Volumetric fluid-rock ratios of 0.02–0.4are required to generate the retrograde assemblage, and observedleucogranite proportions are more than adequate to provide therequired volume of fluid. Estimates of retrograde fluid fluxesrange from 0.25 to 510² cm³/cm² for a transient temperaturegradient of 5C/m, to 310³ to 710⁴ cm³/cm² for a temperaturegradient of 35C/km. These gradients are characteristic of askarn-type contact metamorphic environment and a regional crustalgeotherm, respectively. They imply different time-scales andlength-scales for the retrograde fluid flow system, with theformer more akin to a contact metamorphic setting with local,meter-scale retrograde fluid flow, and the latter to a regionalmetamorphic setting with regionally high mid- and lower-crustaltemperatures and fluid flow throughout a significant thicknessof the middle crust. Higher gradients are considered more likelygiven the proximity of leucogranites to retrogressed calc-silicategneisses, and the resultant relatively small fluxes are consistentwith a magmatic source. The length-scale of reaction within the retrograde fluid flowsystem was of the order of meters to hundreds of meters andinvolved both pervasive and (later) fracture-controlled down-temperatureflow. Retrograde fluid flow in this terrance, as well as othersdominated by magmatic volatiles, is in the form of multiplediscrete bursts of fluid released in a discontinuous mannerpotentially over long periods of time (1–10 Ma) with locallyvariable thermal gradients along the flow path.  相似文献   

Ensemble prediction of blocking regime transitions   总被引：2，自引：0，他引：2  

JORGEN S. FREDERIKSEN  MARK A. COLLIER  ANDREW B. WATKINS 《地球，A辑:动力气象学与海洋学》2004,56(5):485-500

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Source,timing, frequency and flux of ice‐rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis     

ANNA I. HAAPANIEMI  JAMES D. SCOURSE  VICTORIA L. PECK  HILARY KENNEDY  PAUL KENNEDY  SIDNEY R. HEMMING  MARK F. A. FURZE  ANNA J. PIEŃKOWSKI  WILLIAM E. N. AUSTIN  JOHN WALDEN  EMILIE WADSWORTH  IAN R. HALL 《Boreas: An International Journal of Quaternary Research》2010,39(3):576-591

Haapaniemi, A.I., Scourse, J.D., Peck, V.L., Kennedy, H., Kennedy, P., Hemming, S.R., Furze, M.F.A., Pieńkowski, A.J., Austin, W.E.N., Walden, J., Wadsworth, E. & Hall, I.R. 2010: Source, timing, frequency and flux of ice‐rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis. Boreas, Vol. 39, pp. 576–591. 10.1111/j.1502‐3885.2010.00141.x. ISSN 0300‐9483. Increased fluxes of ice‐rafted detritus (IRD) from European ice sheets have been documented some 1000–1500 years before the arrival of Laurentide Ice Sheet (LIS)‐sourced IRD during Heinrich (H) events. These early fluxes have become known as ‘precursor events’, and it has been suggested that they have mechanistic significance in the propagation of H events. Here we present a re‐analysis of one of the main cores used to generate the precursor concept, OMEX‐2K from the Goban Spur covering the last 30 ka, in order to identify whether the British–Irish Ice Sheet (BIIS) IRD fluxes occur only as precursors before H layers. IRD characterization and planktonic foraminiferal δ¹⁸O measurements constrained by a new age model have enabled the generation of a continuous record of IRD sources, timing, frequency and flux, and of local contemporary hydrographic conditions. The evidence indicates that BIIS IRD precursors are not uniquely, or mechanistically, linked to H events, but are part of the pervasive millennial‐scale cyclicity. Our results support an LIS source for the IRD comprising H layers, but the ambient glacial sections are dominated by assemblages typical of the Irish Sea Ice Stream. Light isotope excursions associated with H events are interpreted as resulting from the melting of the BIIS, with ice‐sheet destabilization attributed to eustatic jumps generated by LIS discharge during H events. This positive‐feedback mechanism probably caused similar responses in all circum‐Atlantic ice‐sheet margins, and the resulting gross freshwater flux contributed to the perturbation of the Atlantic Meridional Overturning Circulation during H events.  相似文献   

Identifying key processes in the hydrochemistry of a basin through the combined use of factor and regression models   总被引：5，自引：0，他引：5  

SANDOW MARK YIDANA  BRUCE BANOENG-YAKUBO  PATRICK ASAMOAH SAKYI 《Journal of Earth System Science》2012,121(2):491-507

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