Sedimentological evidence for a major subsurface fracture system linking the eastern Campsie and the eastern Ochil faults

Abstract

Synopsis Evidence for intra-Carboniferous and end-Carboniferous right-lateral strike slip within the Midland Valley is concentrated along lineaments which reflect major subsurface fracture systems. One such lineament runs ENE below the Kincardine Basin and joins the eastern Campsie Fault to the eastern Ochil Fault. This moved right-laterally during the deposition of the Passage Group, as proved by contemporaneous movements of its associated oblique folds. The hinge line between the Tulliallan Trough ‘low’ and the Bogside Saddle ‘high’ follows this lineament. The ‘low’ controlled the locus of the major Saline Channel Belt throughout most of the Namurian, whereas unusually thick peats commonly accumulated over the ‘high’. Reversals of apparent downthrow along this hinge reflected movements, probably right-lateral strike slip, along the underlying lineament. Low-angle detachments may explain the absence of any major ENE–WSW trending surface fracture above the lineament in the Kincardine Basin. The lineament, which probably extends WSW below the eastern part of the Milngavie–Kilsyth Fault to underlie the Paisley Ruck, may have been initiated as a Riedel Shear by right-lateral strike-slip along the Highland Boundary Fault, or it may reflect a reactivated Late–Caledonian left-lateral strike-slip fault system.