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Samples of sediment collected from the Severn floodplain between Worcester and Gloucester following the severe flooding in January and February 1990, were analysed for their grain size distribution. The results show that most sand was deposited within 20 m of the channel bank, but that fine sand may contribute to flood sediment across the width of the floodplain. James' (1985) numerical model of overbank sedimentation attempts to predict the transfer of sediment to the floodplain during flooding. Geometrical and hydraulic data relating to the Severn flood are used as input for a computer program of James' (1985) model. The pattern of sediment concentrations predicted by the model was compared with that obtained from statistical analysis of the flood sediment. The patterns were found to be similar, so James' (1985) model was considered to predict in a relative sense the distribution of flood sediment.

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Abundant arthropod trackways, assigned to Diplichnites gouldi, are described from the Lower Old Red Sandstone (Early Devonian; Lochkovian) of Pant-y-Maes quarry, Brecon Beacons, South Wales. The trackways are preserved on bedding planes of finely laminated planar and rippled siltstones. The sedimentology of the succession indicates that these units represent bar top and marginal deposits in a braided fluvial setting. Two trackway types are recognized (Type A and B); comparisons with contemporaneous myriapodous producers favour kampecarid and eoarthropleurid myriapods, respectively. Functional analysis of the trackways indicates that the producers were not using the most efficient, stable, walking techniques, but instead utilized in-phase ‘swimming stroke’-like gaits. Together with their occurrence on rippled surfaces, and lateral displacement of some trackways (attributed to currents), this indicates that they were produced sub-aqueously.

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Palaeosols (fossil soils) are a major component of alluvial deposits in the geological record. Not only do these typically show considerable variations in their degrees of development within single formations, but they also exhibit highly complex stratigraphic relationships with one another. A simple quantitative approach to these variations is presented which provides a graphical means of assessing differences in soil (palaeosol) development within a sequence with calcic or petrocalcic horizons. To illustrate the approach, a range of palaeosols from the Siluro-Devonian (Old Red Sandstone) of Britain are characterized in terms of the likely frequency and magnitude of depositional events which occurred during their formation. In particular, two alluvial suites from the Manorbier area of South Wales are analysed using this approach. The technique should be widely applicable to other alluvial successions and provides a means of graphicallv presenting relationships between multiple palaeosols, although the wide range of rates of formation of calcic and petrocalcic horizons precludes their use to provide narrow estimates of deposition rates.

Studies of the lowermost Old Red Sandstone of South Wales (Pridolian-Lochkovian) have revealed that the mudstones that constitute up to 80% of some of the formations have been deposited in a variety of environments. In addition there is a variety of lithofacies associations present in some mud-dominated units that suggests diverse mechanisms of deposition. This paper considers the Moor Cliffs Formation and examines four distinct mudrock facies.The overall depositional environment is considered to have been a multi-stage, multi-channel system, similar to a modern dryland river system, with mud-dominated, moderately sinuous ephemeral rivers that reworked muddy floodplain sediment over a proximal braidplain during seasonal flooding. The alluvial deposits were pedified to varying degrees as calcic Vertisols, which, due to seasonal wetting and drying, provided soil aggregates for reworking by wind and water as sand-or silt-sized pellets. Very infrequent flooding events (superfloods) resulted in extensive stripping of the floodplain surface and the introduction of allochthonous sand sheet deposits over wide areas in this normally sediment-starved system.Depressions (pans or waterholes) on the floodplain formed ephemeral lakes following floods, and acted as sediment traps for dust from the frequent dust storms occurring in the system.