Highland Boundary Fault

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The Highland Boundary Fault is a geologic fault that traverses Scotland from Arran and Helensburgh on the west coast to Stonehaven in the east. It separates two distinctly different physiographic regions: the Highlands from the Lowlands, but in most places it is only recognisable as a change in topography.[1]

Geological map of central Scotland. The fault divides the Old Red Sandstone and Devonian deposits (brownish, no. 23, at center) from the Metamorphic and Archaean deposits (pinkish, no. 27, above the brownish).
Geological map of central Scotland. The fault divides the Old Red Sandstone and Devonian deposits (brownish, no. 23, at center) from the Metamorphic and Archaean deposits (pinkish, no. 27, above the brownish).
Topological map of central Scotland. Lower elevations (greenish) are separated from higher elevations (brownish) by the fault line.
Topological map of central Scotland. Lower elevations (greenish) are separated from higher elevations (brownish) by the fault line.

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 to Aberfoyle, then Callander, Comrie and Crieff. It then forms the northern boundary of the Vale of Strathmore and reaches the North Sea immediately north of Stonehaven near the ruined Chapel of St. Mary and St. Nathalan.[2] 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.[2]

The Highland Boundary Fault was active during the Caledonian Orogeny,[1] 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.[2]

[edit] References

  1. ^ a b Loch Lomond - Highland Boundary Fault. Scottish Geology. Hunterian Museum and others (2006-07-20). Retrieved on 2006-12-13.
  2. ^ a b c Highland Boundary Fault. Gazetteer for Scotland. University of Edinburgh and Royal Scottish Geographical Society. Retrieved on 2006-12-13.

[edit] See also

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