Abstract

The basal Cambrian clastic sediments in northwest Scotland record a transgressive sequence of barrier island to tidal shelf quartz-arenites (Eriboll Sandstone Lower Member and Pipe Rock) overlain by a storm-dominated interval of mixed clastic-carbonate sediments (Fucoid Beds). Two shallowing events interrupt this sequence: the lower near the middle of the Pipe Rock, and the upper at the top of the Fucoid Beds which led to the deposition of the quartz-arenites of the Salterella Grit. Variations in the proportion of storm deposited facies and in the thickness of tidally generated structures suggests that tidal currents progressively increased during deposition of the quartz-arenites and then decreased until deposition of the mixed clastic-carbonate deposits. These features suggest amplification of tides as the shelf approached a resonant width during transgression. Further transgression produced a wide, non-resonant shelf where tides were frictionally damped, and storm processes were dominant. Similar sequences of the same age in western Newfoundland, eastern Greenland and Spitsbergen may also have been produced by the shelf bordering the north American craton responding to tidal amplification followed by frictional damping.

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