Moine Thrust (structure)
|Name structure:||Moine Thrust|
|Exposed length:||125 km|
|Type locality||Knockan Crag|
|Key reference:||Elliott, D, Johnson, M R W., 1980. Structural evolution in the northern part of the Moine thrust belt, NW Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, 71: 69-96.|
|Schematic geological map of the Northern Highlands, showing extent of the Moine Thrust.|
Author(s): M Krabbendam (BGS).
The Moine Thrust is the main tectonic structure in the North West Highlands. It is a major thrust (a low angle reverse fault formed by shortening) formed during the Caledonian Orogeny during NW-directed teconic transport. It forms the NW boundary of the metamorphic rocks of the Caledonian Orogeny. It separates metamorphosed metasediments of the Neoproterozoic (c. 1000 ma) Moine Supergroup above the thrust from low-grade rocks of Cambro-Orodovician and older rocks below. The character of the thrust is highly variable from place to place: in some places (for instance between Ullapool and Knockan Crag) the Moine Thrust lies directly on rocks of the Foreland, in other places the Moine thrust forms the roof thrust of the Moine Thrust Zone, a complicated zone of thrust imbricates. Various geologists have placed the Moine Thrust in slightly different places, depending on their definition of the thrust. The Moine Thrust is taken here to be the western thrust boundary of Moine rocks, regardless of whether the thrust at that location is a ductile or brittle structure. Thus, rocks directly underneath the Moine Thrust have been deformed in a brittle fashion in some places, whereas in other areas they are mylonites formed by ductile deformation at high temperatures. The difference between these two end-members is illustrated by comparing the sections at the Stack of Glencoul and at Knockan Crag, two of the best exposed sections across the thrust the NW Highlands.
The Moine Thrust was important in the developing science of geology as it represent one of the first places where geologists in the 19th century recognized that large volumes of rocks could be translated over large distances along low angle faults. The development of these ideas led to a long-standing scientific debate between c. 1855 and 1886, known as the ‘Highlands Controversy’.
The Moine Thrust extends from the north coast of Sutherland, east of Durness, via Assynt, Ullapool, Kinlochewe, Lochcarron, Glenelg to Ard Thurnich on the Sleat peninsula of Skye.
|The Moine Thrust at Knockan Crag, north of Ullapool. Mylonitic Moine rocks above Durness Limestone. Transport direction was to the west (left). P531955.||Skolithos trace as seen on a bedding plane. P514906.|
- Moine Thrust