A reappraisal of the facing confrontation in north Cornwall: fold- or thrust-dominated tectonics?

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Abstract
The problem of conflicting fold or thrust solutions to the interpretation of the structure of north Cornwall is discussed via new detailed mapping of the coastal sections. In addition to facing evidence, shear criteria have been extensively applied in order to sustain new interpretations. The facing confrontation at Polzeath is confirmed but the high strain zone centred upon Tintagel is ascribed to later superimposed northwards directed ductile shearing. Peak metamorphism was synchronous with this event. Subsequent northwards displacement became confined to discrete thrust planes dismembering the south-facing structures which developed during an intermediate phase of backthrusting. The major structures are thrust-dominated, though large recumbent folds were generated during the early ductile phases. The facing confrontation is probably allochthonous having been carried northwards on a blind thrust. It is suggested that the important Rusey Fault Zone is the roof thrust to a triangle zone in which the lower grade rocks of the Culm Basin are uplifted over an underlying antiformal stack.