Late Proterozoic and Late Palaeozoic movement on the Coigach fault in NW Scotland

Synopsis Movement on the NNE-trending Coigach fault in NW Scotland can be dated by reference to the late Proterozoic Stoer and Torridon Groups which it cuts. It behaved as a normal fault in late Stoer Group time, with downthrow to the east. The fault was reactivated after the Cambrian as a listric fault with a downthrow to the west, displacing Torridon Group sediments about 5 km. Roll-over near the fault suggests that it soles out at around 8 km below present sea level. Most of the post-Cambrian movement was probably Devonian or Carboniferous. Mesozoic and later movement was negligible. Other NNE-trending faults on the mainland resemble the Coigach fault in showing large pre-Triassic displacements of the Torridon Group.