This excursion guide deals with the Upper Dalradian rocks which are exposed northwest of the Highland Boundary Fault in the South-west Highlands of Scotland. The exposures to be described are formed by the shores of Loch Long, and by the coast of the Firth of Clyde. The excursion based on Rosneath is largely independent of the state of the tide since the exposures are mostly above the high-water mark on raised beaches. However, the excursion based on Dunoon should be undertaken when the tide is low at localities 16 and 17.
The Dalradian rocks exposed to the north-west of the Highland Boundary Fault form four stratigraphic groups in the South-west Highlands. The first group is exposed in the north-west of the area under consideration as a thick series of schistose grits, quartzose mica-schists and pelitic schists. These rocks are known as the Beinn Bheula Schists. They are succeeded to the south-east by a varied series of rocks forming the Dunoon Phyllites. This group include schistose pebbly grits, schistose grits and greywackes, schistose semi-pelites and pelites, together with purple or black phyllites and dark fine-grained limestones. The last two rock-types are characteristic of the Dunoon Phyllites. These rocks are followed to the south-east by the Bullrock Greywacke which consists mainly of massive schistose grit. Finally, the Innellan Group of schistose pebbly grits and phyllites is found to the south-east of the Bullrock Greywacke in south-east Cowal. The rock-types in this group are similar to those forming the Dunoon . . .
- © 1977 Scottish Journal of Geology