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71.
IAN M. HOWAT EUGENE W. DOMACK 《Boreas: An International Journal of Quaternary Research》2003,32(1):56-75
This study analyses acoustic profiles of two mid-shelf troughs, the JOIDES Basin and Pennell Trough in the western Ross Sea, Antarctica. These troughs are subglacial erosion features formed by repeated advance of streaming ice onto the Ross Sea continental shelf. Sediment wedge formations, interpreted to have been deposited at the most seaward grounding zone during the Last Glacial Maximum (LGM), are observed within the mid-shelf region of these troughs. By correlating high-resolution acoustic profiles with core samples, we resolve the stratigraphy of these wedge formations to assess the relationships between bathymetry, subglacial sediment distribution and palaeo-ice-stream configuration. The grounding zone wedge geometries were controlled by the pre-existing topography. The JOIDES and Pennell Troughs were only partially infilled during the LGM. Axial diamict progradation from the landward margin of the troughs indicates enhanced flow (debris supply) along the axis of ice flow. Differences in grounding zone geometries indicate a decrease in basal debris deposition and/or supply during ice recession. The lack of a recessional ice-shelf facies indicates that either the ice shelf was absent during retreat, or that there was no melt-out of basal debris. 相似文献
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74.
GARY J. HUNTER IAN P. WILLIAMSON 《International journal of geographical information science》2013,27(2):169-179
With an ever-increasing number of land information systems being developed, there is a growing demand by users for systems which support the use of temporal data for time-based studies. System managers, however, may have difficulty responding to these calls because of the lack of available research to guide them in their task. This paper examines the simple method of storing and processing temporal graphical data by the addition of time-encoding attributes to data elements as required. To illustrate the technique, a historical digital cadastral database has been created which al lows users to display and report on the cadastral parcellation of a region at any time in the past. The method can also be widely applied to other data to assist a broad range of space/time-related studies. 相似文献
75.
Abstract This paper outlines the origins and objectives of the four multidisciplinary Regional Research Laboratories (RRLs) established in Great Britain by the Economic and Social Research Council at Cardiff, Edinburgh, London and Newcastle, and describes the work undertaken in the first 6 months of the trial phase. The RRLs will have four main functions, viz., data management, software development, spatial analysis and research training. An example is given of the work undertaken at each RRL, viz., a general purpose system for the display and query of large spatially-referenced data sets, an integrated spatial database for south-east England, a health care planning information system for the County of Avon and a target marketing system. The trial phase of this initiative is then evaluated in terms of its laboratory, research and regional dimensions 相似文献
76.
IAN A. KANE MASON L. DYKSTRA BENJAMIN C. KNELLER SACHA TREMBLAY WILLIAM D. McCAFFREY 《Sedimentology》2009,56(7):2207-2234
Seafloor images of coarse‐grained submarine channel–levée systems commonly reveal complex braid‐plain patterns of low‐amplitude bedforms and zones of apparent bypass; however, mechanisms of channel evolution and the resultant channel‐fill architecture are poorly understood. At Playa Esqueleto the lateral relationships between various elements of a deep‐marine slope channel system are well‐exposed. Specifically, the transition from gravel‐dominated axial thalwegs to laterally persistent marginal sandstones and isolated gravel‐filled scours is revealed. Marginal sandstones pass into a monotonous thin‐bedded succession which built to form relatively low‐relief levées bounding the channel belt; in turn, the levées onlap the canyon walls. Three orders of confinement were important during the evolution of the channel system: (i) first‐order confinement was provided by the erosional canyon which confined the entire system; (ii) confined levées built of turbidite sandstones and mudstones formed the second‐order confinement, and it is demonstrated that these built from overspill at thalweg margins; and (iii) third‐order confinement describes the erosional confinement of coarse‐grained thalwegs and scours. Finer‐grained sediment was transported in suspension and largely was unaffected by topography at the scale of individual thalwegs. Facies and clast analyses of conglomerate overlying channel‐marginal scours reveal that they were deposited by composite gravity flows, which were non‐cohesive, grain‐dominant debris flows with more fluidal cores. These flows were capable of basal erosion but were strongly depositional; frictional freezing at flow margins built gravel levées, while the core maintained a more fluidal transport regime. The resultant architecture consists of matrix‐rich, poorly sorted levées bounding better‐sorted, traction‐dominated cores. The planform geometry is interpreted to have consisted of a low‐sinuosity gravel braid‐plain built by accretion around mid‐channel and bank‐attached bars. This part of the system may be analogous to fluvial systems; however, the finer‐grained sediment load formed thick suspension clouds, probably several orders of magnitude thicker than the relief of braid‐plain topography and therefore controlled by the levées and canyon wall confinement. 相似文献
77.
Rift valleys have always enthralled geologists. They are the rents in the Earth's crust produced when continental plates pull apart. Besides telling us something about the evolution of our planet, they also act as topographic sumps in which parts of the sedimentary record of Earth history are often best preserved. Yet our understanding of how, where, and why rifts form has only recently come of age with new models of structure and sedimentation. 相似文献
78.
79.
The Teton Dam: rhyolite foundation + loess core = disaster 总被引:1,自引:0,他引:1
IAN SMALLEY 《Geology Today》1992,8(1):19-22
The Teton Dam was a large embankment dam built in Idaho, USA, in 1975. It failed catastrophically in 1976. Two major causes of failure were the fissured rhyolite terrain on which the dam was built and the brittle permeable loess used for the core. Thus two geological factors combined to produce an engineering disaster. The complex of factors involved in the failure is still being discussed by engineers and geologists. 相似文献
80.
REX HARLAND DIANE M. GREGORY MURRAY J. HUGHES IAN P. WILKINSON 《Boreas: An International Journal of Quaternary Research》1978,7(2):91-96
BOREAS Harland, R., Gregory, Diane M., Hughes, M. J. & Wilkinson, I. P. 1978 06 01: A late Quaternary bio- and climatostratigraphy for marine sediments in the north-central part of the North Sea. Boreas, Vol. 7, pp. 91–96. Oslo. ISSN 0300–9483.
Micropalaeontological studies of three boreholes in the north-central North Sea have led to the erection of a bio- and climatostratigraphy for the area. Palaeoenvironmental interpretations have depended largely upon oceanographic concepts and changes in the micropalaeontological assemblages have been related to postulated alterations in water mass regimes. The biostratigraphy can then be utilized as a climatostratigraphy since such water mass changes are most probably linked to alterations in the circulation of the North Atlantic, and in particular to the positions of the climatically important North Atlantic Current and Polar Front. The North Sea sequences are compared to similar sections in Europe and related to the commonly accepted standard chronostratigraphy. 相似文献
Micropalaeontological studies of three boreholes in the north-central North Sea have led to the erection of a bio- and climatostratigraphy for the area. Palaeoenvironmental interpretations have depended largely upon oceanographic concepts and changes in the micropalaeontological assemblages have been related to postulated alterations in water mass regimes. The biostratigraphy can then be utilized as a climatostratigraphy since such water mass changes are most probably linked to alterations in the circulation of the North Atlantic, and in particular to the positions of the climatically important North Atlantic Current and Polar Front. The North Sea sequences are compared to similar sections in Europe and related to the commonly accepted standard chronostratigraphy. 相似文献