On the origin of a reddened interflow bed within the Palaeocene lava field of north Skye

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Abstract
Synopsis: A reddish brown to reddish orange interflow bed from the Palaeocene lava field of north Skye at Lochan nan Dunan is considered to be of epiclastic origin, with features which distinguish it from in situ palaeosols and solely volcaniclastic deposits. It has sharp upper and lower contacts, is clay matrix-supported, and is dominated by clasts of lateritic rock, together with clasts of somewhat altered basaltic rock and siltstone. Also present are: crystals of fresh clinopyroxene (Wo 46.26–47.35 En 45.29–45.91 Fs 6.85–8.18 ), plagioclase (An 70–75 ) and alkali feldspar (Or 30–50 Ab 50–70 An ); shards of hawaiitic glass; and secondary hydrothermal minerals in a variety of associations. The clasts of lateritic rock and the fine-grained matrix of the bed were both derived from a previously developed palaeosol and the clasts of volcanic and sedimentary material were also derived from considerably weathered material. The crystals and glass shards are considered to have been derived either from primary ash eruptions or from contemporaneous, unaltered ash deposits. Palynological investigations reveal that the bed is devoid of pollen and spores, and contains only fragments of inertinite, indicating that it was exposed at the Earth’s surface for a relatively short time interval, and confirms that the reddening ‘event’ occurred prior to deposition of the bed. The bed contains valuable information about pyroclastic material and phenocryst-bearing magmas not preserved elsewhere in the lava field, and the fresh nature of this material indicates that the time intervals between eruption of the ash, deposition of the bed, and the eruption of the overlying lava flow(s) were relatively short.