摘要:

AbstractThis paper is about conditions and processes during the accumulation of the Upper Pleniglacial Middle and Upper Silt Loam complexes at Nagelbeek, Limbourg, a Weichselian stratigraphical type locality. The complexes correlate with Hesbayan and Brabantian loesses in Belgium, formed between 28,000 and 12,400 yrs BP. They are characterized by sediment features (cracks, mass deformations, and cut‐and‐fill features) that are ascribed to a cryogenic regimen. The main Middle Silt Loam subunit contains contraction cracks deformed and further modified by masswasting. Intra‐Upper‐Pleniglacial pedogenic intervals are inferred from three greyish bands, from a truncated weathered zone surmounting the Middle Silt Loam, and from an aeolian‐cumulic palaeosol at the base of the Upper Silt Loam. Latter two zones and an intervening erosional unconformity were cryogenically reworked, less than 22,000 yrs BP, to form a complex stratigraphical marker‐zone: the ‘Horizon à Langues de Nagelbeek’. Morphological variants of the marker‐zone are described. The geomorphic evolution of the Nagelbeek upland, from Saalian to Holocene times, is summarized in unconformity maps

ISSN:0197-9337    

DOI:10.1002/esp.3290090102

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractA review of the characteristics of segregated surfaces and consideration of the origins of the termsarmouredandpavedsuggests that the two terms are interchangeable, and that neither term is specifically associated with a particular segregation process. The dichotomy between segregated surfaces which are formed in channels in which the entire range of bed material is mobile under the prevailing hydrologic regime, and segregated surfaces which are intrinsically stable, forms the basis of an elementary distinction between different types of segregated surface. It is suggested that the termstable armour or stable pavementbe applied to those cases where the segregated surface is considered to be inactive under the prevailing hydrologic regime, and that the termunstable armourorunstable pavementbe applied to cases where the segregated surface experiences periodic mobilization.

ISSN:0197-9337    

DOI:10.1002/esp.3290090103

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractGypsum (plaster of paris) has been cast into spheres and placed in soils; weight loss has been used to identify relative water flow routes. Theoretical considerations and laboratory experimentation show that solutional weight loss of the material used increases with increasing water flow, but is independent of pH above pH 4. Results for gypsum sphere weight loss are presented for soils where moisture conditions have been measured independently using tensiometers. The data suggest that the weight loss method provides a viable time‐integrated demonstration of relative water flow route

ISSN:0197-9337    

DOI:10.1002/esp.3290090104

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractDissolved organic matter (DOM) and iron in a moorland stream were determined at 8‐hour intervals over a 6‐month period to examine relationships with streamflow. Regression of both solutes on discharge were positive and explained 50–70 per cent of the variance in the solute data, but better predictions were obtained in both cases when a covariate reflecting temporal variation in the relationships was introduced (explained variance 80–90 per cent). Variations in the regression of Fe on DOM were also identified, indicating differences in the complexing power of DOM for Fe and possible variations in the chemical composition of

ISSN:0197-9337    

DOI:10.1002/esp.3290090105

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractStream response to surface coal mining and reclamation was studied in 29 small (0·13 to 5·72 km2) watersheds located in the bituminous coal fields of Central Pennsylvania. These basins, up to 82 per cent mined, were selected from 176 first‐order tributaries of Beech Creek with similar vegetation, soil, lithology, and basin characteristics. Measurements were made at 262 cross‐sections (an average of nine cross‐sections per stream) of channel cross‐section area, bankfull width, mean bankfull depth, dimensions of the largest moving blocks, stream slope, valley‐side slope, basin area, and mined area. Observed differences in channel morphology were related to differences in extent of mining by means of scatter plots, correlation, cluster analysis, and bivariate regression.Stream response to increased peak discharge and channel shear stress produced by increased surface runoff from regraded mine spoil takes the form of enlarged channels and increases in the size of moving blocks. Large basin areas appear to dampen the effect of mining, resulting in limited channel enlargement with greater extent of mining. In contrast, where peak discharges and associated shear stresses exceed the combined erosional resistance of floodplain vegetation, colluvial blocks, and channel banks, streams adjust extensively to higher levels of mining, causing an abrupt increase in the size of transported blocks and eroded channels. In the first‐order basins studied, this stepped response occurs at approximately 0·45 km2mined area and 50 per cent of the total basin area mined.For streams that have exceeded both threshold levels, disequilibrium is demonstrated by a strong, positive correlation between local stream slope and basin area. Where both threshold levels of mining are exceeded, steep channel slopes reinforce the tendency of stream cross‐sections to increase with greater disturbance by mining, necessitating that these streams rapidly adjust their morphology in order to attain a new equilibrium which is compatible with the conditions imposed by mining

ISSN:0197-9337    

DOI:10.1002/esp.3290090106

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe Piedmont upland of Maryland has been variously interpreted as a peneplain, a series of peneplains, a surface of marine planation, and a landscape in dynamic equilibrium. These different perspectives of landform evolution are related to different scales of time and space. Both equilibrium and episodic erosion features can be recognized in the modern landscape. An equilibrium condition is suggested by adjustment of first and second order streams to rock structure and lithology, entrenchment of some streams against gneiss domes, altitudinal zonation of rock types around gneiss domes, correlation of lithology with overburden thickness on uplands, decreasing overburden thickness on uplands related to decreasing degree of metamorphism of crystalline rocks, and correlation of secondary mineral assemblages with subsurface drainage and slope. The long‐term episodic character of erosion is suggested by clastic wedges on the adjacent Coastal Plain, an upland of low relief that truncates non‐carbonate rocks of different lithologies, isovolumetric chemical weathering of alumino‐silicate rocks, clastic deposition in marble valleys, and weathering profile truncation by modern drainage.The Maryland Piedmont may have been an area of positive relief subject to subaerial erosion since Triassic and possibly Permian time. The upland surface preserved in the eastern Piedmont developed by the Late Cretaceous. In the interval from the Late Cretaceous to the Late Miocene, low input of terrigenous sediments to the Coastal Plain, dominance of marine sedimentation, and spotty evidence of saprolite formation on crystalline rocks, suggest that the Maryland Piedmont was an area of low relief undergoing intense weathering. Incised valleys were formed during a cycle of erosion probably initiated in the Late Miocene and extensive colluvial sediments were deposited on hillslopes by periglacial processes during the Pleist

ISSN:0197-9337    

DOI:10.1002/esp.3290090107

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe Soil Survey for Scotland, in their mapping of the soils in Orkney, identified a deep top phase of the Bilbster Series. This soil is distinguished by having a topsoil usually in excess of 75 cm and it occurs almost exclusively on the Mainland of Orkney, especially in the west round Marwick and Skaill Bays. An anthropogenic origin to this soil is proposed and the present study is designed to investigate the particular processes of formation which have led to the increase in soil depth. Results from transect and grid surveys indicate how the soil is thickest adjacent to old farms. The historical literature suggests a wide range of possible inputs from seaweed and calcareous sand to turves after they had been used as bedding for cattle. Analytical results support the last process as the dominant one and an accumulation rate of c.1 mm/yr is proposed.

ISSN:0197-9337    

DOI:10.1002/esp.3290090108

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290090109

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290090110

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractMicro‐erosion meter sites, installed on Aldabra Atoll, Indian Ocean in 1969 to measure erosion rates in coastal and subaerial sites, were remeasured in 1971 and again in 1982. The orders of magnitude of calculated erosion rates are comparable but the precise figures and patterns differ. For subaerial sites the short term (1969–71) range of 0·11–0·58 mm a−1compares with a long term (1971–82) range of 0·06–0·75 mm a−1; for coastal sites short term ranges of 0·002–7·5 mm a−1compare with long term rates of 0·09–2·7 mm a−1. Interpretation and extrapolation of short term data sho

ISSN:0197-9337    

DOI:10.1002/esp.3290090111

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY