Aligned southwest to northeast, from Lochranza on Arran it bisects the Isle of Bute, and crosses the south eastern parts of the Cowal and Rosneath Peninsulas as it passes up the Firth of Clyde. It comes ashore near Helensburgh then continues through Loch Lomond. The loch islands of Inchmurrin, Creinch, Torrinch, and Inchcailloch all form part of the Highland boundary fault.
From Loch Lomond it continues to Aberfoyle, then Callander, Comrie and Crieff. It then forms the northern boundary of Strathmore and reaches the North Sea immediately north of Stonehaven near the ruined Chapel of St. Mary and St. Nathalan. To the north and west lie hard Precambrian and Cambrian metamorphic rocks: marine deposits metamorphosed to schists, phyllites and slates. To the south and east are Old Red Sandstone conglomerates and sandstones: softer, sedimentary rocks of the Devonian and Carboniferous periods.
The Highland Boundary Fault was active during the Caledonian Orogeny, a plate tectonic collision which took place from Mid Ordovician to Mid Devonian periods (520 to 400 million years ago), during the closure of the Iapetus Ocean. The fault allowed the Midland Valley to descend as a major rift by as much as 4000 metres and there was subsequently vertical movement. This earlier vertical movement was later replaced by a horizontal shear. A complementary fault, the Southern Upland Fault, forms the southern boundary for the Central Lowlands.
Garnet Provenance Studies, Juxtaposition of Laurentian Marginal Terranes and Timing of the Grampian Orogeny in Scotland
May 01, 1998; A. R. HUTCHISON* & G. J. H. OLIVER Abstract: A study of the composition and zoning patterns of detrital garnets from Ordovician...