Evidence for Tertiary Crustal Distortion in Mid-Argyll

REGIONAL deformation associated with the emplacement of Tertiary igneous rocks is well known in the British Isles. There appears to be some evidence in mid-Argyll, recorded on the one-inch maps of the Geological Survey of Scotland1, which suggests that crustal distortion (broadly similar to that described from east Greenland by Wager and Deer2) may have occurred in this area during the Tertiary. This distortion is now reflected by a change in the trend of the Old Red Sandstone minor dyke swarm, the north-north-east–south-south-west tear-faults and, also, by variations in the strike of the Dalradian country-rocks; the district over which this change takes place coincides with the path of the Tertiary dyke swarm centred on Mull.