INDUSTRIALIZATION OF U.S. AGRICULTURE. AN INTERPRETIVE ATLAS. By Howard F. Gregor     

RICHARD LE HERON 《New Zealand geographer》1984,40(2):117-118

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Microstructures of sediment flow deposits and subglacial sediments: a comparison     

MATTHEW S. LACHNIET  GRAHAME J. LARSON  DANIEL E. LAWSON  EDWARD B. EVENSON  RICHARD B. ALLEY 《Boreas: An International Journal of Quaternary Research》2001,30(3):254-264

Microstructural analysis of glacial deposits has recently been used as a research tool to determine sediment genesis. However, the occurrence of microstructures in deposits of known origin has not been sufficiently documented, hindering our ability to confidently interpret microstructures in sediments of unknown origin. Our objective is to present a calibration study of microstructures of recent sediment flow deposits and associated sediments from the Matanuska Glacier, Alaska, and to evaluate the degree of commonality with microstructures found in subglacially deformed sediments. Microstructures in sediment flow deposits can be formed as a result of sediment transport, deposition, and/or post-depositional processes, and are related to the viscosity regime of the source flow. Characteristic microstructures formed during brittle deformation include shears, faults, and brecciation; microstructures formed during ductile deformation include folds, pressure shadows, re-orientation of clasts around a 'core' stone, fine laminations, basal shear zones, imbrication, and flow fabrics. Other microstructures include fluid escape and injection structures, clast haloes, and fissility. The results of our comparison suggest that sediment flow deposits share many microstructures in common with subglacially deformed sediments.  相似文献   

Comments on a Paper by Jon. D. Woodhead Titled 'The Origin of Geochemical Variations in Mariana Lavas: a General Model for Petrogenesis in Intra-oceanic Island Arcs?'     

CONREY  RICHARD M. 《Journal of Petrology》1990,31(4):957-962

A general model for andesite genesis in intra-oceanic arcs involvingmagnetite fractionation has been proposed. Such a model is notconsistent with the low abundance of cumulate magnetite in gabbroicxenoliths in the Marianas and other arcs, and with the generallylow normative magnetite contents of Marianas lavas. Fractionationmodels involving magnetite consistently overestimate incompatibleelement abundances, and underestimate compatible Cr abundance.Magnetite fraction ation models offer no ready means of explainingeither the ubiquitous evidence for mineralogic disequilibriain arc rocks of all types, or the consistent correlation ofFeO*/MgO ratio and K₂O content in Marianas andesites.  相似文献   

A history of vegetation and fire, 6,600 B.P. to present, County Sligo, western Ireland     

JOHN R. DODSON  RICHARD H. W. BRADSHAW 《Boreas: An International Journal of Quaternary Research》1987,16(2):113-123

Dodson, John R. & Bradshaw, Richard H. W. 1987 06 01: A history of vegetation and fire, 6,600 B.P. to present, County Sligo, western Ireland. Boreas , Vol. 16, pp. 113–123. Oslo. ISSN 0300–9483.
Two lake sites on metamorphic rocks with small catchments and one mor humus deposit have been analysed to assess the relative influences of fire, man and climate upon the regional and local vegetation of the Lough Gill region of County Sligo. The vegetation of the area was dominated by mixed woodland from 6,600 B.P. to 600 B.P. The first evidence of human impact on the forests was around 5,400 B.P. in the form of clearance for pasture. The intensity of human impact varied between sites, and there were periods of forest recovery as well as decline. From 600 B.P. widespread forest destruction took place, and pasture with heathland became predominant. Pinus sylvestris had a major presence until about 5,400 B.P. It declined from this time and had a patchy distribution by 2,000 B.P. The decline of Pinus was linked with the expansion of treeless peatland in what are presumed to be wet periods, and Pinus recovery in drier periods. Fire may have encouraged the spread of heathland at the expense of Pinus . Arbutus unedo pollen was found at Slish Lake as early as 1,900 B.P., suggesting that it is native to this area. Isolated trees survive today at woodland edges. Charcoal particles occurred in all the profiles. Fire was particularly associated with heathland communities, and may have been used as a management tool to improve grazing conditions. Some of the phases of woodland decline correlate strongly with charcoal input suggesting forest destruction by fire.  相似文献   

Diagnosing cyclogenesis by partitioning energy and potential enstrophy in a linear quasi‐geostrophic model     

DANIEL HODYSS  RICHARD GROTJAHN 《地球，A辑:动力气象学与海洋学》2001,53(5):567-577

Baroclinic development is studied with 2 linear, quasi‐geostrophic models. One model is the Eady model, the other uses more realistic wind, density, Coriolis, and static stability. Initial‐value solutions are diagnosed using time series of potential enstrophy ( H ), total energy ( E ), the components of H and E , and the amplitude norm. Two vertical structures for the initial condition are used for both models. One initial condition is representative of a class of initial conditions studied previously having enhanced nonmodal growth (NG). The other initial condition approximates observed conditions prior to cyclogenesis. Results are shown for the most unstable normal mode wavelength of each model. The growth rates of the components of H and E evolve quite differently for different initial states and models tested. NG in H is shown to be sensitive to the contribution of the boundary potential vorticity (BPV) of the initial state; small adjustments in eddy structure at the boundary significantly alter BPV and H growth rates. The amount of NG is related to how far BPV present initially differs from the asymptotic normal mode. The effect upon NG of each approximation present in the Eady model (but not in the other model) are considered. Using realistic mean flow shear, static stability, or compressibility can significantly reduce NG but including linearly varying Coriolis parameter did not. Two conceptual models of NG are considered. Growth by increasingly favorable superposition remains relevant. Growth by "tilting into the vertical" is shown to be incorrect.  相似文献   

INDUSTRIAL AWAKENING. A GEOGRAPHY OF AUSTRALIAN MANUFACTURING 1788 to 1890     

RICHARD LE  HERON 《New Zealand geographer》1981,37(1):43-44

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Coordinating future adaptation policies across Canadian natural resources     

ADAM M. WELLSTEAD  RICHARD C. STEDMAN 《Climate Policy》2013,13(1):29-45

What are the roles of informal coordination networks, policy-oriented beliefs, and the concern about climate change? Informal networks are considered in addition to the highly publicized strategies and commitments made by government departments and agencies. Based on a survey of agriculture, forestry and water-based policy elites in the Canadian prairies, this article examines the structure and impact of informal networks and policy-oriented beliefs. To do so, a number of testable hypotheses were proposed. The results indicate that respondents looked to the federal government as a potential ally. However, the federal government did not reciprocate by supporting the other major organizational clusters (agriculture and forest industry, provincial government, environment groups and research organizations). A bleak picture of future action on climate change emerges when the gaps between closed and polarized networks are considered.  相似文献   

The feasibility of a land information system for Belize,Central America     

RICHARD F. HYDE 《International journal of geographical information science》2013,27(1):99-109

Abstract

Limitations of the current land records systems in Belize, Central America, led leaders of the Ministry of Natural Resources to initiate this feasibility study for a computer-aided land information system (LIS). Land records in Belize have been based on the British Torrens land tenure system, which maintains five sets of records along with informative maps. One paper file is maintained for each title application and records are continually circulated between seven locations throughout the country, resulting in up to 3 years to complete the process of title registration. A LIS will permit quick access to land records and eliminate most of the current problems, and will merge with a geographic information system being developed for Belize.  相似文献   

An inductive modelling procedure based on Bayes' theorem for analysis of pattern in spatial data     

RICHARD ASPINALL 《International journal of geographical information science》2013,27(2):105-121

Abstract

This paper describes an inductive modelling procedure integrated with a geographical information system for analysis of pattern within spatial data. The aim of the modelling procedure is to predict the distribution within one data set by combining a number of other data sets. Data set combination is carried out using Bayes’ theorem. Inputs to the theorem, in the form of conditional probabilities, are derived from an inductive learning process in which attributes of the data set to be modelled are compared with attributes of a variety of predictor data sets. This process is carried out on random subsets of the data to generate error bounds on inputs for analysis of error propagation associated with the use of Bayes’ theorem to combine data sets in the GIS. The statistical significance of model inputs is calculated as part of the inductive learning process. Use of the modelling procedure is illustrated through the analysis of the winter habitat relationships of red deer in Grampian Region, north-east Scotland. The distribution of red deer in Deer Management Group areas in Gordon and in Kincardine and Deeside Districts is used to develop a model which predicts the distribution throughout Grampian Region; this is tested against red deer distribution in Moray District. Habitat data sets used for constructing the model are accumulated frost and altitude, obtained from maps, and land cover, derived from satellite imagery. Errors resulting from the use of Bayes’ theorem to combine data sets within the GIS and introduced in generalizing output from 50 m pixel to 1 km grid squares resolution are analysed and presented in a series of maps. This analysis of error trains is an integral part of the implemented analytical procedure and provides support to the interpretation of the results of modelling. Potential applications of the modelling procedure are discussed.  相似文献   

Calcretes,fluviolacustrine sediments and subsidence patterns in Permo‐Triassic salt‐walled minibasins of the south Urals,Russia     

ANDREW J. NEWELL  MICHAEL J. BENTON  TIMOTHY KEARSEY  GRAEME TAYLOR  RICHARD J. TWITCHETT  VALENTIN P. TVERDOKHLEBOV 《Sedimentology》2012,59(5):1659-1676

The south Uralian foreland basin forms part of the giant, yet sparsely documented, PreCaspian salt tectonic province. The basin can potentially add much to the understanding of fluviolacustrine sedimentation within salt‐walled minibasins, where the literature has been highly reliant on only a few examples (such as the Paradox Basin of Utah). This paper describes the Late Permian terrestrial fill of the Kul’chumovo salt minibasin near Orenburg in the south Urals in which sediments were deposited in a range of channel, overbank and lacustrine environments. Palaeomagnetic stratigraphy shows that, during the Late Permian, the basin had a relatively slow and uniform subsidence pattern with widespread pedogenesis and calcrete development. Angular unconformities or halokinetic sequence boundaries cannot be recognized within the relatively fine‐grained fill, and stratigraphic and spatial variations in facies are therefore critical to understanding the subsidence history of the salt minibasin. Coarse‐grained channel belts show evidence for lateral relocation within the minibasin while the development of a thick stack of calcrete hardpans indicates that opposing parts of the minibasin became largely inactive for prolonged periods (possibly in the order of one million years). The regular vertical stacking of calcrete hardpans within floodplain mudstones provides further evidence that halokinetic minibasin growth is inherently episodic and cyclical.  相似文献