Arkle: Lewisian-Cambrian unconformity

Arkle: Lewisian-Cambrian unconformity

The mountain of Arkle in west Sutherland consists of quartz arenites (quartz-cemented quartz sandstones) of Lower Cambrian age. The pale grey screes cover the planar unconformity with the underlying Lewisian gneisses, which have a shallow dip to the east-south-east (to the right in the photo).