Great Glen Fault and Timing of Granite Intrusion on the Proto-Atlantic Continental Margins

Age distribution patterns for the British Caledonian granites—the products of destructive plate margin processes—are most consistent with a reconstruction based on dextral transcurrent faulting in the Great Glen. Post-intrusive cooling rates (3 to 10° C per m.y.) suggest an Ordovician metamorphic climax which predates closure of the Proto–Atlantic ocean. Consequently there arose many geological contrasts between the opposing continental margins.