Geology pages

The topography of the mapping area is observed to be partially controlled by lithology, with differing units producing areas of low and high relief. The Tollie gneiss is an exception to this as the lithology is seen to have little control on the relief, but to the west of Meall Airigh Mhic Criadh (NGR 83177766) where the gneissose banding becomes much thinner a topographic low is observed (the valley of the Allt Eas Ghairbh Ghraird NGR 82107757), with poor exposure in the central part of the valley. Overall, the Tollie gneiss is very well exposed in the higher parts with the topography being extremely rugged.

The Garbh amphibolite forms a ridge of high relief with good exposure on the higher parts of the ridge but poorer exposure in the forested part of the unit immediately south of the road

The Luibean semipelitic schists form a valley with very poor exposure. This unit is bounded on the west by the Achlais amphibolite, which forms a ridge (highest point being Meall na h-lolaire 775 feet NGR 81227703). The exposure in this unit is adequate but peters out in to peat bog around Loch Clair. The Torr schists form part of this ridge with exposure being good in the higher areas, but poor exposure in the lower area around Auchercairn farm.

The Sabhail amphibolite is a small well-exposed unit, which does not significantly affect the topography.

The Gairloch schist is a small poorly exposed unit, which also has no significant effect on topography.

The Camas breccia is reasonably well exposed along the coast but does not affect topography significantly.