Visualization for exploration of spatial data     

MENNO-JAN KRAAK  ALAN MACEACHREN 《International journal of geographical information science》2013,27(4):285-287

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JAMGIS,the first Jamaican Government comprehensive multi-data geographical information system Achievements and problems     

L. ALAN EYRE 《International journal of geographical information science》2013,27(4):363-371

Abstract

JAMGIS, the first comprehensive multi-data geographical information system (GIS) in Jamaica, has been developed by the Ministry of Agriculture in cooperation with USAID and two universities in the U.S.A. The system and its database are described and a number of problems encountered in its development and practical application are discussed. The most valuable products to date have been the delineation of areas of crop suitability, two series of twelve land use/cover maps at 1:50000 scale and statistical analyses of soil and land resources.  相似文献   

Geological and mineral deposit maps of the Arab World     

ALAN S. COLLINSON  MICHAEL J. DA VIES  PETER IBBOTSON 《Geology Today》1987,3(5):133-135

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An intercomparison of three-dimensional tidal hydrodynamic models of the Irish Sea     

ALAN M. DAVIES  HERMAN GERRITSEN 《地球，A辑:动力气象学与海洋学》1994,46(2):200-221

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Interglacial marine deposits of the Somerset Levels, South West England     

CLARENCE KIDSON  DAVID D. GILBERTSON  JOHN R. HAYNES  ALAN HEYWORTH  CLEDWYN E. HUGHES  ROBIN C. WHATLEY 《Boreas: An International Journal of Quaternary Research》1978,7(4):215-228

Sands and gravels underlain by silts and clays, known as the Burtle Beds, from the Somerset Levels of South West England have been examined in a specially excavated pit. The Mollusca, Foraminifera and the Ostracoda, and the sparse macroscopic plant remains included in the deposit, all indicate a prgressive marine transgression in which water temperatures obtained approximating to those of the present sea in the adjacent Bristol Channel. The deposits are shown to be estuarine/marine near shore and intertidal sediments of interglacial age. Radiometric assays and studies of palaeomagnetism have failed to indicate clearly which interglacial marine transgressive phase is involved. Geomorphological considerations supported to some extent by the Ostracoda suggest that a last interglacial (Ipswichian) age is more likely than an earlier (Hoxnian?) date. Estimates of the height of sea levels involved are, of necessity, based on evidence which cannot be regarded as wholly reliable. Having regard to the environmental conditions indicated by the included fauna, and making allowance for post depositional erosion, it is suggested that mean sea level at the height of the ‘Burtle’ transgression was between 9 and 12 m above that of the present (O. D.). Assuming a similar tidal range to that of today, a MHWST (Mean High Water of Spring Tides) level of between 15 and 18 m above O. D. is indicated  相似文献   

Isotope Geochemistry of Tertiary Igneous Rocks from the Isle of Skye, N.W. Scotland   总被引：1，自引：4，他引：1  

DICKIN  ALAN P. 《Journal of Petrology》1981,22(2):155-189

New Pb isotope analyses are reported for forty-seven basic,intermediate and acid Tertiary igneous rocks from the Isle ofSkye and adjacent regions of northwest Scotland. New Sr isotopeanalyses and two Rb/Sr isochron dates are also reported forthe acid igneous rocks. These results are combined with publishedSr and Nd isotope data for Tertiary igneous rocks from Skyeand adjacent regions in order to examine the genesis and evolutionof Tertiary magmas in the Isle of Skye. Pb isotope analyses form a linear array on a Pb/Pb isochrondiagram, with a slope yielding an apparent age of 2920 ±70m.y. (2), interpreted as a mixing line between ca. 2900 m.y.-oldcrustal Pb and 60 m.y.-old mantle-derived Pb. Combined isotopicdata support a model of selective crustal Pb, Sr and Nd contaminationof basic and intermediate mantle-derived magmas, without significantmodification of major-element composition. This contaminationprocess is probably due to the breakdown of LIL-element-enrichedaccessory mineral phases, and does not necessarily produce linearmixing lines on isotope ratio plots of different elements. SkyeRedhills epigranites contain a predominant fraction of acidmagma which differentiated from mantle-derived basic precursors,and a subsidiary fraction of upper crustal melt. The proportionof this melt is estimated to rise from less than 10 per centin the older granites to around 30 per cent in the younger. Isotopic and geochemical data are used to draw conclusions aboutthe differentiation histories of the four principal magma typesof Skye: the Fe-rich and Fe-poor members of the Skye Main LavaSeries, Preshal Mhor Basalts and Redhills epigranites.  相似文献   

HYDRAULIC STUDIES ON THE ORIGIN OF BEDDING     

ALAN V. JOPLING 《Sedimentology》1963,2(2):115-121

A series of quasi-quantitative experiments on delta building were carried out in a laboratory flume for the purpose of studying the mechanics of deposition of topsets, foresets, and bottomsets. The genesis of these sets can be rationally explained through the discipline of sediment transport mechanics by taking cognizance of (a) the hydraulic phenomena of gradually varied and rapidly varied flow, (6) the concept of aggradation to a profile of equilibrium. The geometry of a delta front is controlled by the dynamics of the environment of deposition, and the frontal profile can be inter- preted as a function of the micro-mechanics of particle movement in the transition zone where the stream enters the basin of deposition.  相似文献   

Phonolitic Diatremes within the Dunedin Volcano, South Island, New Zealand   总被引：2，自引：2，他引：2  

PRICE  RICHARD C.; COOPER  ALAN F.; WOODHEAD  JON D.; CARTWRIGHT  IAN 《Journal of Petrology》2003,44(11):2053-2080

The Port Chalmers Breccia is a vent-filling, clastic volcanicunit exposed within the Miocene Dunedin Volcano of South Island,New Zealand. Clasts (up to in excess of 1 m but generally <20cm) are supported in ash and fine lapilli of phonolitic (ne-benmoreiteor tephro-phonolite) composition and the dominant clast type(55 to almost 100%) is also phonolitic. Less abundant lithologiesinclude ne-normative basalt (basanite), hawaiite, mugeariteand trachyandesite, syenites and microsyenites, coarse-grainedmafic (gabbros) and ultramafic rocks (pyroxenites, hornblendites),schists and sediments. The breccias were emplaced as diatremesassociated with localized, but highly explosive, eruptive eventsin which mantle-derived CO₂ was an important component. Thesyenitic and ultramafic clasts could represent intrusive suitesproduced by crystal fractionation acting on parental ne-benmoreitemagmas that may themselves have been derived by crystal fractionationfrom basanitic precursors. An alternative variation on thismodel is that the parental ne-benmoreites were generated throughpartial melting of an alkalic igneous underplate. Sr, Nd andPb isotopic compositions are strikingly similar to those ofintraplate igneous rocks, ranging in age from 100 to less than10 Ma, from elsewhere in the South Island, and New Zealand'ssub-Antarctic islands, the south Tasman Sea and the Ross Searegion. This regional, HIMU-influenced, isotopic signature isbelieved to be derived from within the lithospheric mantle. KEY WORDS: phonolite; diatreme; nepheline syenite; Dunedin Volcano; alkalic rocks; fractional crystallization  相似文献   

Spatial distribution of carbon sources and sinks in Canada's forests   总被引：7，自引：0，他引：7  

JING M. CHEN  WEIMIN JU  JOSEF CIHLAR  DAVID PRICE  JANE LIU  WENJUN CHEN  JIANJUN PAN  Y BLACK  ALAN BARR 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):622-641

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What status for the Quaternary?   总被引：3，自引：0，他引：3  

PHILIP L. GIBBARD  ALAN G. SMITH  JAN A. ZALASIEWICZ  TIFFANY L. BARRY  DAVID CANTRILL  ANGELA L. COE  JOHN C. W. COPE  REW S. GALE  F. JOHN GREGORY  JOHN H. POWELL  PETER F. RAWSON  PHILIP STONE  COLIN N. WATERS 《Boreas: An International Journal of Quaternary Research》2005,34(1):1-6

The status of the Quaternary, long regarded as a geological period effectively coincident with the main climatic deterioration of the current Ice Age, has recently been questioned as a formal stratigraphic unit. We argue here that it should be retained as a formal period of geological time. Furthermore, we consider that its beginning should be placed at the Gauss-Matuyama magnetic chron boundary at about 2.6 Ma, rather than at its current position at about 1.8 Ma. The Quaternary would be formally subdivided into the Pleistocene and Holocene epochs. The global chronostratigraphical correlation table proposed is enclosed at the back of this issue.  相似文献