WIND EROSION AND PM10 EMISSIONS FROM AGRICULTURAL FIELDS ON THE COLUMBIA PLATEAU     

LARRY D. STETLER  KEITH E. SAXTON 《地球表面变化过程与地形》1996,21(7):673-685

Research to investigate relations between simultaneous processes of soil erosion by wind and PM₁₀ emissions from dry land fields on the Columbia Plateau, Washington, has been initiated by the U.S. Department of Agriculture — Agricultural Research Service (ARS) and Washington State University. Dry land agriculture is the primary cropping system world-wide but is constantly threatened by erosive winds which reduce the soil resource and/or remove fines which are the most active soil portion for plant production. Soils on the Columbia Plateau are very fine-grained containing more than 4 per cent of freely occurring aggregates or particles less than 10 μm aerodynamic diameter. Analysis from eight wind events show that significant relations exist between total mass of soil in both horizontal (saltation) and vertical (suspension) transport. The data suggest that by limiting horizontal soil erosion, emitted dust can be simultaneously reduced. Aggressive conservation tillage can be an effective weapon in reducing soil erosion by maintaining surface residue and roughness.  相似文献   

NEW UNCERTAINTY CONCEPTS IN HYDROLOGY AND WATER RESOURCES edited by Z. W. Kundzewicz,Cambridge University Press/UNESCO/IASH International Hydrology Series, 1995. No. of pages: xiii + 322. Price: £75.00 (hb). ISBN 0-521-46118-9.     

KEITH BEVEN 《地球表面变化过程与地形》1996,21(10):982-983

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Tidal influence in Cretaceous fluvial strata from Utah, USA: a key to sequence stratigraphic interpretation   总被引：6，自引：0，他引：6  

KEITH W. SHANLEY  PETER J. McCABE†  ROBERT D. HETTINGER† 《Sedimentology》1992,39(5):905-930

Detailed models already exist that outline physical and temporal relationships in marine and marginal marine strata. Such models are still in their infancy in alluvial deposits. Recognition of tidal and estuarine influence in fluvial strata is critical to the development of high resolution sequence stratigraphic correlations between marine and non-marine strata. Strata that have previously been interpreted as low energy meandering river deposits contain sedimentary and biogenic structures that suggest a tidal influence. These structures include sigmoidal bedding, paired mud/silt drapes, wavy and lenticular bedding, shrinkage cracks, multiple reactivation surfaces, inclined heterolithic strata, complex compound cross-beds, bidirectional cross-beds, and trace fossils including Teredolites, Arenicolites and Skolithos. Although none of these structures is unique to tidal processes, the preponderance of data suggests that fluvial systems have been affected by tidal processes well inland of coeval shoreline deposits. These deposits rarely form a significant proportion of a depositional sequence; however, their occurrence allows time significant surfaces to be extended for tens or even hundreds of kilometres inland from coeval shoreline deposits. In Turonian through Campanian strata exposed in the Kaiparowits Plateau of southern Utah, tidally influenced facies are recognized within at least two distinct stratigraphic levels that were deposited during periods of relatively rapid base level rise. These strata form part of an alluvial transgressive systems tract. Landward of each of the marine transgressive maxima, tidal facies are present in fluvial channels that are completely encased in non-marine strata at distances up to 65 km inland from a coeval palaeoshoreline. Our work suggests that such deposits may have gone unrecognized in the past, but they form a significant component of alluvial strata in many depositional sequences. Although these tidally influenced fluvial deposits may be difficult to recognize, they are temporally equivalent to marine maximum flooding surfaces and provide a chronostratigraphic correlation between alluvial and nearshore marine deposits.  相似文献   

Triassic carbonate submarine fans along the Arabian platform margin, Sumeini Group, Oman     

KEITH F. WATTS 《Sedimentology》1988,35(1):43-71

ABSTRACT The Sumeini Group formed along the passive continental margin slope that bounded the northeastern edge of the Arabian carbonate platform. With the initial development of this passive continental margin in Oman during Early to Middle Triassic time (possibly Permian), small carbonate submarine fans of the C Member of the Maqam Formation developed along a distally steepened slope. The fan deposits occur as several discrete lenticular sequences of genetically related beds of coarsegrained redeposited carbonate (calciclastic) sediment within a thick interval of basinal lime mudstone and shale. Repeated pulses of calciclastic sediment were derived from ooid shoals on an adjacent carbonate platform and contain coarser intraclasts eroded from the surrounding slope deposits. Sediment gravity flows, primarily turbidites with lesser debris flows and grain flows, transported the coarse sediments to the relatively deep submarine fans. Channel erosion was a major source of intraformational calcirudite. Two small submarine fan systems were each recurrently supplied with calciclastic sediment derived from point sources, submarine canyons. The northern fan system retrogrades and dies out upsection. The southern fan system was apparently longer-lived; calciclastic sediments in it are more prevalent and occur throughout the section. The proximal portions of this fan system are dominated by channelized beds of calcirudite which represent inner- to mid-fan channel complexes. The distal portions include mostly lenticular, unchannelized beds of calcarenite, apparently mid- to outer-fan lobes. Carbonate submarine fans appear to be rare in the geological record in comparison with more laterally continuous slope aprons of coarse redeposited sediment. The carbonate submarine fans of the C Member apparently formed by the funnelling of coarse calciclastic sediment into small submarine canyons which may have developed due to rift and/or transform tectonics. The alternation of discrete sequences of calciclastic sediment with thick intervals of ‘background’ sediment resulted from either sea-level fluctuations or pulses of tectonic activity.  相似文献   

AN INTEGRATED APPROACH TO MODELLING HYDROLOGY AND WATER QUALITY IN GLACIERIZED CATCHMENTS     

KEITH RICHARDS  MARTIN SHARP  NEIL ARNOLD  ANGELA GURNELL  MICHAEL CLARK  MARTIN TRANTER  PETER NIENOW  GILES BROWN  IAN WILLIS  WENDY LAWSON 《水文研究》1996,10(4):479-508

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Laos and the making of a 'relational' resource frontier   总被引：1，自引：0，他引：1  

KEITH BARNEY 《The Geographical journal》2009,175(2):146-159

This paper seeks to reconsider the contemporary relevance of the resource frontier, drawing on examples of nature's commodification and enclosure under way in the peripheral Southeast Asian country of Laos. Frontiers are conceived as relational zones of economy, nature and society; spaces of capitalist transition, where new forms of social property relations and systems of legality are rapidly established in response to market imperatives. Customary property rights on the resource frontier can be seized by powerful actors in crucial political moments, preparing the territorial stage for more intensive phases of resource commodity production and accumulation. Relational frontier space is understood through the work of geographers such as Doreen Massey, who views the production of space as 'constituted though the practices of engagement and the power-geometries of relations'. In Laos, a twenty-first century resource frontier is being driven by new corporate investments in natural resources, and a supporting array of land reform programmes. The paper focuses on both the material and representational aspects of the production of the resource frontier, through policy and discourse analysis, and village level research in Laos' Khammouane province. By rethinking a dualist and hierarchical-scaled imaginary of frontier places, both rural people and local ecologies are shown to be key actors, in a complex, relational reproduction of frontier zones. An emerging Lao spatial and political assemblage – a form of 'frontier-neoliberalism'– is shown as producing dramatic changes in socio-natural landscapes, as well as new patterns of marginalisation and livelihood insecurity for a vulnerable rural population.  相似文献   

Terrace scarp deflation as a renewable source for eolian sediments in an arctic periglacial setting     

KEENE SWETT  KEITH MANN 《Polar research》1987,5(1):45-52

Glacial, glaciofluvial, and glaciolacustrine sediments deposited by the retreating Vibekes Glacier are being actively reworked into sand dunes and loess sheets on the tops of glaciofluvial terraces down-valley from Vibekes Glacier and Vibekes So. Active permafrost precludes trenching below 0.5 to 1.0 meters. However, sedimentary structures, deflationary and abrasion features in shallow and surface deposits are visible. Although an armored pavement inhibits sediment deflation on the horizontal terrace surfaces, a combination of fluvial erosion, mass-wasting, and eolian processes on terrace scarps provides a continuing source of sand- and silt-size materials for redeposition.  相似文献