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Sedimentological Advances |
1 Postgraduate Research Institute for Sedimentology, University of Reading, Whiteknights, P.O. Box 227, Reading, Berkshire RG6 6AB, UK R.Goldring{at}reading.ac.uk
2 Southampton Oceanography Centre, University of Southampton, Empress Dock, Southampton SO14 3ZH, UK
3 Department of Geology, University of Leicester, Leicester LE1 7RU, UK
An attempt to establish the depositional environment of the Bencliff Grit and its stratigraphic relationships is made using sedimentology, micropalaeontology, palynology and ichnology. Integration of these techniques demonstrates that the main sand units that characterize the Bencliff Grit represent periodic incursions by unidirectional west- and WNW-directed high-density flows, into water depths of at least 5 m from which biological recovery was relatively slow. An essentially autogenic process with dune migration over a colonized interdune area can probably be rejected. The ‘event’ sand units were not associated with colonized sediment-water interfaces. There are at least eight thin units of heterolithic muds and sands closely associated with two suites of marine trace fossils representing sand (Diplocraterion habichi) and mud (D. parallelum) associations. All mud samples are characterized by a signature of marine palynomorphs and microfossils. The palynofacies show significant differences which correlate with sedimentary facies. These include a palynofacies indicative of rapid sedimentation (in muds immediately following sands). In muds associated with the marine trace fossils a diagenetically modified assemblage is present. A bay or lagoonal setting with back-barrier washover sands is tentatively favoured rather than the intertidal, shoreface or estuary model previously used. The base of the Bencliff Grit does not a priori represent a sequence boundary and there are no parasequences within the formation. A sequence boundary may be present within the top 1 m of the formation, associated with a complex transgressive surface.
