Morphology and surface sedimentary features of point bars in Welsh gravel-bed rivers

Abstract

SummaryTwo examples of point bars in single-channel gravel-bed rivers in Wales illustrate some of the morphological and surface sedimentary features observed during a wider examination of 40 sites of recent (less than 100 years) channel sedimentation. The point bars consist of predominantly sandy gravel bar platforms overlain by discontinuous sand bodies. Cut bank exposures show generally massive sandy gravels abruptly underlying a silt/sand unit. Morphologically the bars are platformlike, with primary inner-attached, or secondary medial, chutes. This relief, together with the effects of seasonal vegetation, determines the locations of finer-grained (non-gravel) material. The frequency with which deposits produced by this type of channel sedimentation may be encountered in Quaternary and pre-Quaternary successions is briefly discussed.