The Tectonics of the Morar Anticline and the Problem of the North-West Caledonian Front

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Abstract
Summary: Within the Morar region of western Inverness-shire, the schists of the Moine Series, adjacent to the North-West Caledonian Front, are disposed in a great N.-S.-trending anticlinal fold—the Morar anticline—which consists of a simple discordant envelope of normal Moine Schists in continuous stratigraphical succession, and a complex core of highly folded and deformed Moine-like rocks with associated, tectonically incorporated gneisses of basement (Lewisian) type. A reinvestigation of the area leads to the conclusion that the lower part of the Moine succession has been reduplicated within the core of the Morar anticline and that the structure provides an example of a window opened by erosion on a pitch culmination. The simple envelope is identifled as an upper Moine or Morar nappe which has been driven westwards across a much broken, autochthonous basement, with partial reduplication of the Moine succession. This structural interpretation applies also to the homologous Loch Hourn—Glenelg anticline to the north and is shown to be comparable in style with the type of relationship which exists between the autochthonous Hercynian massifs and the Helvetic ang Subalpine zones of the Alps. The structures in the Morar area are correlated with those of the North-West Caledonian Front to the west of the Moine thrust, and two orogenic phases of Caledonian movement are distinguished, (a) an earlier (mid-Ordovician) phase of folding and thrusting, followed by regional injection and regional metamorphism of the Moine Series, and (b) a later (late-Silurian=Erian) phase of clean-cut thrusting—the Moine thrust phase. The region is regarded, therefore, as a