AN ASSOCIATION OF MINOR FINING-UPWARD CYCLES AND ALIGNED GUTTER MARKS IN THE MIDDLE LIAS (LOWER JURASSIC) OF THE YORKSHIRE COAST

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Abstract
Summary: Two thin sandstone and siltstone horizons in the Middle Lias (Lower Jurassic) of the Yorkshire coast, informally called the lower and upper striped beds, are characterised by small-scale fining-upward layers associated with filled scour channels (gutter marks). The gutters are up to 5 m long, 50–500 mm wide and up to 200 mm deep, and have variable cross-sections. Some have a simple, fining-upward laminated structure, others a complex, multiple-stacked structure. They show a remarkably uniform, approximately east-west, orientation at localities 20 km apart. The trend of rare ripple marks is approximately at right angles to the gutter marks. The striped beds are interpreted as deposits of submarine sheet flows, with contemporary scour and fill, in a prodelta - open shelf slope setting.