984 resultados para Fluvial
Quantification of a distributive fluvial system; the Salt Wash DFS of the Morrison Formation, SW USA
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Peer reviewed
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Inclui notas explicativas e bibliográficas.
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On cover: Estudio de derecho internacional.
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.
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Prepared in cooperation with U.S. Army, Corps of Engineers, Huntington District, Huntington, West Virginia.
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Mode of access: Internet.
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Documents relating to exploratory journeys by boat through the Peruvian Amazon basin.
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Two different slug test field methods are conducted in wells completed in a Puget Lowland aquifer and are examined for systematic error resulting from water column displacement techniques. Slug tests using the standard slug rod and the pneumatic method were repeated on the same wells and hydraulic conductivity estimates were calculated according to Bouwer & Rice and Hvorslev before using a non-parametric statistical test for analysis. Practical considerations of performing the tests in real life settings are also considered in the method comparison. Statistical analysis indicates that the slug rod method results in up to 90% larger hydraulic conductivity values than the pneumatic method, with at least a 95% certainty that the error is method related. This confirms the existence of a slug-rod bias in a real world scenario which has previously been demonstrated by others in synthetic aquifers. In addition to more accurate values, the pneumatic method requires less field labor, less decontamination, and provides the ability to control the magnitudes of the initial displacement, making it the superior slug test procedure.
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It has been established that large numbers of certain trees can survive in the beds of rivers of northeastern Australia where a strongly seasonal distribution of precipitation causes extreme variations in flow on both a yearly and longer-term basis. In these rivers, minimal flow occurs throughout much of any year and for periods of up to several years, allowing the trees to become established and to adapt their form in order to facilitate their survival in environments that experience periodic inundation by fast-flowing, debris-laden water. Such trees (notably paperbark trees of the angiosperm genus Melaleuca) adopt a reclined to prostrate, downstream-trailing habit, have a multiple-stemmed form, modified crown with weeping foliage, development of thick, spongy bark, anchoring of roots into firm to lithified substrates beneath the channel floor, root regeneration, and develop in flow-parallel, linear groves. Individuals from within flow-parallel, linear groves are preserved in situ within the alluvial deposit of the river following burial and death. Four examples of in situ tree fossils within alluvial channel deposits in the Permian of eastern Australia demonstrate that specialised riverbed plant communities also existed at times in the geological past. These examples, from the Lower Permian Carmila Beds, Upper Permian Moranbah Coal Measures and Baralaba Coal Measures of central Queensland and the Upper Permian Newcastle Coal Measures of central New South Wales, show several of the characteristics of trees described from modern rivers in northeastern Australia, including preservation in closely-spaced groups. These properties, together with independent sedimentological evidence, suggest that the Permian trees were adapted to an environment affected by highly variable runoff, albeit in a more temperate climatic situation than the modem Australian examples. It is proposed that occurrences of fossil trees preserved in situ within alluvial channel deposits may be diagnostic of environments controlled by seasonal and longer-term variability in fluvial runoff, and hence may have value in interpreting aspects of palaeoclimate from ancient alluvial successions. (C) 2001 Elsevier Science B.V. All rights reserved.
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We appreciate very helpful reviews by Dr. Martin Stokes and three anonymous reviewers and editor Dr. Richard Marston. We also appreciate the encouragement for writing this paper from Dr. Timothy Horscroft. We acknowledge support of the sponsors of the Fluvial Systems Research Group consortium, BP, BG, Chevron, ConocoPhillips and Total.
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We appreciate very helpful reviews by Dr. Martin Stokes and three anonymous reviewers and editor Dr. Richard Marston. We also appreciate the encouragement for writing this paper from Dr. Timothy Horscroft. We acknowledge support of the sponsors of the Fluvial Systems Research Group consortium, BP, BG, Chevron, ConocoPhillips and Total.
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Peer reviewed