XXXV. The Highland Boundary Fault in Arran

Abstract

The Highland Boundary Fault strikes the north-east coast of Arran near the Fallen Rocks, where, instead of continuing its normal south-westerly course, which would take it right across the granite mountains which form the nucleus of the island, it turns to the south and south-east, and describes a semi-circle concentric with the granite, till it disappears under the Sound of Kilbrannan at Dougrie. Here the fault appears to resume its normal direction, reappearing near the Mull of Kintyre, and passing on into the north-east of Ireland. Tracing the fault across Arran from the north-east, we find that for the first two miles its direction is nearly due south, and the quartzite conglomerates of the Lower Old Red Sandstone lie uptilted against nearly vertical schists, some of which, from the presence of cherty bands associated with lavas, somewhat resembling the Arenig rocks of the Southern Uplands, are suggested by the Geological Survey to be of corresponding age. The schists are cut out on the north side of Glen Sannox, and for the next three miles the Lower Old Red lies directly against, and has been greatly indurated and altered by contact with the granite. The schists reappear half a mile to the north-west of the summit of Maol Don, and from this point right across to the western shore of the island form a narrow strip, bordering the granite on the one side and having the Old Red faulted down against them on the other. The intrusion of the granite has, This 250-word extract was created in the absence of an abstract