| Summary: | The Upper Jurassic succession in the West Shetland area is composed of a Kimmeridge Clay Formation equivalent. Within this formation, two sandstone members are identified: the Rona Member, which forms the lowermost sandstone unit, and the Solan Sandstone Member. Within the Rona Member, nine different facies are identified. The facies reflect deposition by a variety of different depositional processes (fluvial, sheetflood, debris flow, high and low density turbidity flow, suspensions), in environments ranging from deep marine to upper and lower shoreface and subaerial and submarine fan deltas. The Rona Member varies in thickness between 4 and 84 m, with vertical facies transition reflecting deposition under progressively more marine conditions. The thickest and coarsest grained successions are confined to the present-day structural highs and overlie Lewisian aged metamorphics. The immature sandstone composition indicates short transport distances and derivation from the underlying Lewisian basement. Thin and finer grained successions have a wider distribution and also overlie Triassic and Lower Jurassic strata. Deposition of the Rona Member is interpreted to have been controlled by the gradual transgression of a residual relief on the Lewisian basement, with the thickest occurrences confined to low relief areas. The Solan Sandstone Member is interbedded with Kimmeridigan shales and is composed of two facies. Facies A comprises massive, homogeneous sandstones, dominated by water-escape structures, and deposited by sustained turbidity currents. Facies B sandstones occur as sandstone injection structures (sills and dykes), which have been sourced by facies A sandstone bodies. Solan sandstones are compositionally mature and have a limited distribution.
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