Shelf-margin clinoforms and prediction of deepwater sands   总被引：1，自引：1，他引：1  

Erik P. Johannessen  Ron J. Steel† 《Basin Research》2005,17(4):521-550

Early Eocene successions from Spitsbergen and offshore Ireland, showing well‐developed shelf‐margin clinoforms and a variety of deepwater sands, are used to develop models to predict the presence or absence of turbidite sands in clinoform strata without significant slope disturbance/ponding by salt or mud diapers. The studied clinoforms formed in front of narrow to moderate width (10–60 km) shelves and have slopes, 2–4°, that are typical of accreting shelf margins. The clinoforms are evaluated in terms of both shelf‐transiting sediment‐delivery systems and the resultant partitioning of the sand and mud budget along their different segments. Although this sediment‐budget partitioning is controlled by sediment type and flux, shelf width and gradient, process regime on the shelf and relative sea‐level behaviour, the most tell‐tale or predictive signs in the stratigraphic record appear to be (1) sediment‐delivery system type, (2) degree of shelf‐edge channelling and (3) character of shelf‐edge trajectory through time. The clinoform data sets from the Porcupine Basin (wells and 3‐D seismic) and from the Central Basin on Spitsbergen (outcrops) suggest that river‐dominated deltas are the most efficient delivery systems for dispersing sand into deep water beyond the shelf‐slope break. In addition, low‐angle or flat, channelled shelf‐edge trajectories associate with co‐eval deepwater slope and basin‐floor sands, whereas rising trajectories tend to associate with muddy slopes and basin floors. Characteristic features of the shelf‐edge, slope and basin‐floor segments of clinoforms for these trajectory types are documented. Seismic lines along the slope to basin‐floor transects tend to show apparent up‐dip sandstone pinchouts, but most of these are likely to be simply sidelap features. Dip lines aligned along the axes of sandy fairways show that stratigraphic traps are unlikely, unless slope channels become mud‐filled or are structurally partitioned. Another feature that is prominent in the data sets examined is the lack of slope onlap. During the relative rise of sea level back up to the shelf, the clinoform slopes are generally mud‐prone and they are characteristically aggradational.  相似文献   

Contemporary fiddling in human geography while Rome burns: has quantitative analysis been largely abandoned--and should it be?   总被引：2，自引：0，他引：2  

Ron Johnston  Les Hepple  Tony Hoare  Kelvyn Jones  Paul Plummer 《Geoforum》2003,34(2):157-161

Chris Hamnett [Geoforum 34 (2003) 1] has certainly been provocative in his claim that the nature of much contemporary human geography means that the discipline ‘will cease to be taken seriously in the world beyond the narrow confines of academe’ (p. 1). Much of his critique focuses on what he terms ‘post-modernism, new cultural geography and the interpretative turn’ (p. 2) practiced by those he identifies as ‘the new intellectual dilettanti’ (p. 3). In responding, however, our concern is not with that aspect of his critique, but rather with Hamnett’s misrepresentation of one section of contemporary human geography.  相似文献   

Seismotectonics of the Sinai subplate – the eastern Mediterranean region     

Amos Salamon  Avraham Hofstetter  Zvi Garfunkel  Hagai Ron 《Geophysical Journal International》2003,155(1):149-173

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Book Review: D.Keeble and F.Wilkinson (eds), High-Technology Clusters, Networking and Collective Learning in Europe     

Ron Boschma 《GeoJournal》2002,56(2):167-169

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Separation of multi-component NRM: A general method     

Kenneth A. Hoffman  Ron Day 《Earth and Planetary Science Letters》1978,40(3):433-438

A method is presented which can successfully isolate components of remanent magnetization having intermediate relative stability in a single rock sample which contains any number of remanence components with overlapping coercivity or blocking temperature spectra. The approach consists of analysis of the path swept out by the vector destroyed during a detailed alternating field or thermal demagnetization run. The point of intersection determined for any two neighboring great circle segments identified in such a difference vector path defines the direction of such a component. Samples cored from a fragment of a Jurassic pillow basalt, shown to contain several components of magnetization, serve to illustrate the utility of the method for the case when the Zijderveld approach is unsuccessful.  相似文献   

Devonian basins of western norway - sedimentary response to tectonism and to varying tectonic context     

Ron J. Steel 《Tectonophysics》1976,36(1-3)

The Devonian basins of western Norway are notable for their small size (<2000 km) and for the great stratigraphie thickness (up to 25 km) and the cyclic nature of their coarse-grained, alluvial infilling. These general features alone strongly suggest that tectonism was the dominant control on sedimentation but it is argued in particular that a coarsening-upwards motif, which permeates the three main basins usually on a scale of less than 200 m, was the direct sedimentary response to basin-floor subsidence. The coarsening-upwards is interpreted in terms of progradation of alluvial plain and alluvial fan facies in response to rapid lowering of the basin floor, while the overall cyclicity of the basin fills reflects repetition of such tectonic events. Detailed study within Hornelen Basin shows that the repeated coarsening-upwards theme overprints different sedimentary facies, and, in particular, the clastic wedges on opposite sides of the basin have contrasting thicknesses, radii, grain-size gradients and conglomerate types. These features suggest differing rates or degree of continuity of fault movement on opposite margins of the basin. Hornelen and Solund Basins, the two largest, are strongly contrasted in their differing mode of filling and sediment grade. It is suggested that this may reflect their development under strike-slip and dip-slip dominated regimes, respectively.  相似文献   

Transport,fate, and infectivity of <Emphasis Type="Italic">Cryptosporidium parvum</Emphasis> oocysts released from manure and leached through macroporous soil     

Douglas G. Boyer  Ewa Kuczynska  Ron Fayer 《Environmental Geology》2009,58(5):1011-1019

A major mode of transmission of Cryptosporidium parvum, a widespread waterborne pathogen, is via contaminated drinking and recreational waters. Oocyst transport to surface water can occur by deposition of manure directly in the water or by wash off in surface runoff. Oocyst transport to groundwater is less straightforward and requires that the oocysts move through soil and bedrock to reach the water table. The purpose of this study was to determine the relative concentration and infectivity of C. parvum oocysts released from manure and leached through columns of undisturbed, macroporous karst soil. Modeling the fate of oocysts in this system over time can provide baseline data for evaluating real world events. Substantially more oocysts leached from undisturbed soil columns than disturbed soil columns. Oocyst survival studies using BALB/c neonatal suckling mice showed that about 85% of oocysts were infective at the beginning of leaching experiments. The oocyst infectivity decreased to about 20% after 12 weeks of leaching from soil columns maintained at 10°C. Cool (10°C) temperatures appear to increase survivability and maintain infectivity of many oocysts for 3 months or longer. Cool temperatures also appear to increase rates of release of oocysts from manure and leaching through soil. This study demonstrated that leaching is an important mechanism of oocyst transport in karst soils where infiltration capacities are high and long, continuous macropores exist. Karst groundwater systems might be especially vulnerable to contamination by leached oocysts, because of the prevalence of shallow soils and rapid groundwater movement. Oocysts leaching from soils into the epikarst could accumulate and remain viable for months until hydrological conditions are right for flushing the oocysts into the conduit flow system.  相似文献   

ASIANS,PACIFIC ISLANDERS,AND ETHNOBURBS IN AUCKLAND,NEW ZEALAND     

Ron Johnston  Michael Poulsen  James Forrest 《Geographical review》2008,98(2):214-241

ABSTRACT. Recent work on Asian ethnic minority immigrants to cities in the Anglophone Pacific Rim argues that their settlement patterns do not conform to those of earlier migrant streams. Instead of concentrating in high‐density, low‐quality, inner‐city housing, these new residents are moving directly to suburban areas where they form much less intensive concentrations—ethnoburbs—than has been typical of other culturally distinct migrant groups. We evaluate this thesis for Asian migrants in the Auckland metropolitan area, whose numbers more than quadrupled between 1991 and 2006. Their residential pattern is compared with that of Pacific Islanders also resident there, providing supporting evidence for the ethnoburb hypothesis.  相似文献   

On Geographic and geography     

Ron Johnston 《New Zealand geographer》2009,65(3):167-170

New Zealand Geographic is one of a number of geographical magazines published in the English‐speaking world that make little or no reference to work by academic geographers. It recently launched a New Zealand Geographic Trust to promote research into ‘New Zealand's life, culture and sciences’ and collaborated with four other publishers of geographical magazines to raise awareness of climate change: the work of academic geographers is again ignored. This exclusion of academic and school geography from such enterprises raises important issues regarding the discipline's public profile in New Zealand and suggests the need for greater public engagement activity by the country's geographers.  相似文献   

Shelf edge and shoreline trajectories, a dynamic approach to stratigraphic analysis   总被引：1，自引：1，他引：0  

Sverre Henriksen  Gary J. Hampson†  William Helland-Hansen‡  Erik P. Johannessen§  Ron J. Steel¶ 《Basin Research》2009,21(5):445-453

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