THE THREE FOLD-SYSTEMS IN THE METAMORPHIC ROCKS OF UPPER GLEN ORRIN, ROSS-SHIRE AND INVERNESS-SHIRE

Abstract

The major structures in the area immediately north-east of the Monar area (Ramsay 1958) are a synform and a neutral fold with axes plunging south-west and south respectively. They appear to have formed on the western limb of a larger and earlier major N.–S. antiform. They are, however, separated from the axial region of this fold by a slide, which cuts out a maximum of 7700 feet of the structural succession, and was apparently formed contemporaneously with the synform and neutral fold. All these structures were affected by refolding and distortion during a third phase of folding; this gave rise to structures plunging south-west, which on occasion obscure the earlier structures. It is suggested that the divergent attitudes of the major synform and neutral fold were one effect of this distortion. This three-fold structural history is supported by evidence of the relations of minor structures to the major folds and by observations of earlier small-scale structures refolded or overprinted by later ones. Petrofabric diagrams demonstrate that recrystallization and reorientation accompanied all three phases of folding.