Carboniferous, Northern Highlands of Scotland

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Johnstone, G S and Mykura, W. 1989. British regional geology: Northern Highlands of Scotland. Fourth edition. Keyworth, Nottingham: British Geological Survey.

Strata of Carboniferous age occur in the Northern Highlands only in the peninsula of Morvern; they crop out beneath Permo-Triassic sediments on the northeast shore of the Sound of Mull at Inninmore Bay, and probably also at the head of Loch Aline. This is one of only a small group of Carboniferous outcrops in the Highlands of Scotland, the other representatives of which are found to the south in the Pass of Brander near Loch Awe, at Glas Eilean near Jura, and at Machrihanish in Kintyre. These are described in British Regional Geology: The Grampian Highlands. It seems that these small outliers represent small basins of accumulation developed as the main basin of the Midland Valley Trough to the south intermittently extended into the bordering Highland massif (Francis, 1983).

The Inninmore sediments of the Northern Highlands are at least 100 m (and possibly as much as 160 m) thick, and dip gently to the north beneath the basal breccia of the Trias. The lower part of the sequence consists mainly of white, yellow and grey sandstones, grey and black sandy shales, and impure fireclay. Thin seams of coal occur but are of no economic value. The higher strata consist mainly of massive yellowish pebbly sandstone with some thin beds of lilac- coloured shale.

Various horizons in the sequence yield fossil plants but neither marine nor freshwater shells have been found. Though containing no diagnostic species, the flora[1] form an assemblage which suggests an early Coal Measures age; it includes the following species: Asterophyllites charaeformis, A. equisetiformis, Calamites cisti, C. schutzeiformis, Mariopteris muricata, Neuropteris gigantea, and Samaropsis sp.

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Footnote[edit]

  1. Revised names provided by P. J. Brand.