The tectonics of the Beinn Dronaig area, Attadale

Abstract

On Beinn Dronaig are combined not only three stratigraphic zones of the Moine and several ‶inliers″ of ‶Lewisian″, but, apparently, two systems of folding at right angles to one another. Comparison is made between the structures of Beinn Dronaig and the Monte Rosa (Pennine Alps), and the danger of using doubtful stratigraphy to determine structure is pointed out. It is emphasised that recumbent structures will, in general, have a strike nearly at right angles to the axial-trend. On Beinn Dronaig, even where the strike is NE-SW, the axial-plunge is towards the SSE. Thus, in fact, only one system of folding is present, and its trend is nearly at right angles to the strike of the Moine Thrust-plane. The ‶Lewisian inliers″ do not root in situ; they are discontinuous bodies in the core of a recumbent fold. ‶Mullion-structure″ and pegmatite eyes are common throughout the area, but are especially characteristic of the fold-hinge.