摘要:

ABSTRACTThe relative abundance of thirty‐two surface features identified on the surfaces of quartz sand grains from eight coded samples was noted independently by five scanning electron microscopists. These data (reduced to binary form) were the subject of canonical variate analyses which discriminated clearly between all samples. Thirteen variables were important in distinguishing between the eight samples. This indicates that there are no single key surface features which, on their own, would allow rapid environmental discrimination. The contention that a multiplicity of surface features should be recorded for the purpose of environmental discrimination is, therefore, upheld.Operator variance, although considerable in the recognition of individual surface features, is negligible in discrimination of samples based on binary data. The SEM technique of analysis of quartz grain surface textures is a reliable and statistically valid means of discriminating between samples from different environment

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1983.tb00655.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTParticles projecting from the bed of an alluvial channel distort the fluid stream to produce a distinctive pressure field. This has considerable significance for both the entrapment and entrainment of other particles and is a primary cause of the widespread occurrence of pebble clusters and boulder shadows. Lift and drag forces are determined on clustered hemispherical particles of varying size. In the wake of an obstructing particle both forces are shown to vary directly with particle separation in a linear fashion. On the stoss side of the cluster, drag is uniform regardless of the separation of the component particles, but lift is shown to increase when particle separation is small, so affecting stability. This mutual interference of neighbouring clustered bed particles is a vital consideration of incipient motion and is shown by field evidence to cause a wide range in transport stage for particles of similar size and shape. On average, 46% of clustered particles are entrained by flood flow compared to 87% of particles in open plane‐beds. The influence of clusters is a major determinant of sedimentary sortin

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1983.tb00656.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1983.tb00657.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1983.tb00658.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1983.tb00659.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1983.tb00660.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1983.tb00661.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0037-0746    

DOI:10.1111/j.1365-3091.1983.tb00662.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY