Oykel Gorge
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Condition (NatureScot)
| Unit | Feature | Condition | Area (ha) | Assessed |
|---|---|---|---|---|
| F1 | Moine | Favourable | — | 2010-05-17 |
Geology & landscape
Geological Feature: Gorge / Ravine, Rock Outcrop · Rock Type: Schist
Landscape processes: Fluvial
Description
Oykel Gorge The Oykel Gorge Site of Special Scientific Interest (SSSI) is located at Oykel Bridge (on the A837 road) in east Sutherland. This site has been notified for the geological interest of its ‘Moine Supergroup’ rocks which are approximately 1000 million years old. These were originally deposited as shallow marine sediments. They have since been deeply buried within the Earth, and heated and compressed to form a quartz-rich rock known as ‘psammitic schist‘ containing thin mica-rich layers. The site is important as one of the finest examples in great Britain of prominent parallel grooves and ridges on the rock surface, known as ‘mullions’. The mullions are the result of the compression and the folding of rock which is made up of layers of different compositions which have different strengths. In this case, the quartz-rich rocks are stronger and the mica-rich layers are weaker. The excellence and accessibility of the rock exposure makes this a key site for the study of the formation of mullions. The mullions at Oykel Gorge have been widely featured in geological texts, making the site one of international as well as national importance.