The pre-Torridonian metamorphic history of the Loch Torridon and Scourie areas in the North-West Highlands, and its bearing on the chronological classification of the Lewisian

Summary The paper describes the metamorphic history of two areas of Lewisian gneiss in the North-West Highlands of Scotland. Metamorphosed sedimentary rocks are described for the first time from the Loch Torridon area. It is shown that both in the Loch Torridon and the Scourie districts the gneisses have been produced in two separate periods of metamorphism, migmatization and deformation. These two metamorphic episodes, which are named the Scourian and Laxfordian episodes, are separated in time by a period of uplift and tension during which a series of uniform dolerite dykes was intruded. Since a very great interval of time appears to have elapsed between the two metamorphic episodes, it is suggested that the rocks produced during these episodes should be regarded as members, not of a single formation as heretofore, but of two distinct chronological units.