The Islay Anticline (Inner Hebrides)

Abstract

I. Introduction As compared with the publications of the Geological Survey, the present paper includes the following new features:— (1) Direct structural evidence is offered of the superposition of the Lower Torridonian sediments of the Rhinns of Islay upon the Lewisian Gneiss of the southern part of that peninsula. Dr. Peach and Mr. Wilkinson were not apparently on the outlook for big inversions, apart from such as are introduced by thrusts, and so their interpretation of the structure required confirmation. (2) The Loch Gruinart Fault is recognized, and its possible correlation with the Great Glen Fault discussed. No dislocation is suspected in this position by the Survey authors, but Mr. George Barrow, in conversation, has suggested that an important thrust separates the Rhinns from the rest of Islay. (3) Collateral evidence is afforded of the existence of the Loch Skerrols Thrust. (4) The Maol an Fhithich Quartzite is separated from the Islay Quartzite. (5) The comparatively simple anticlinal structure of North Islay, as illustrated in Sections A & B (Pl. XII), is traced in detail. In the Survey description Dr. Peach and Mr. Wilkinson recognize the anticlinal structure of that part of the district which is included within the horseshoe outcrop of the Dolomitic Group; but they correlate the quartzite beyond this outcrop with the quartzite inside, and assume that the Dolomitic Group is everywhere preserved in synclines. The structural relations, although very clear in the