Faulting and associated cataclasis in Eastern Ardgour

Abstract

Synopsis Three main sets of faults have been identified in Eastern Ardgour, the NE–SW faults, the NW–SE to W–E faults and the N–S faults. Each set has formed in response to a specific tectonic regime. Cataclastic rocks associated with the faults fall into two main series, the protomicrobreccia–microbreccia–cataclasite–ultracataclasite series, and the fault breccia–fault gouge series. These rock types are abundant in the hills and along the north-west shore of Loch Linnhe, but their distribution is far from uniform. The most intense cataclasis occurs along or adjacent to the main faults of the area which themselves lie within broader zones of variably shattered rock. A history of fault activity has been established for the area; of particular interest are the NE–SW faults because they form part of the Great Glen fault zone. Study of these faults and their associated cataclastic rocks indicates that the Great Glen has been active, intermittently, as a brittle seismic fault zone since late Caledonian times.