The Knockrath series of alternating black slates and quartzitic siltstones and the conformably overlying Bray series of mudstones and graywackes are both considered Precambrian and to have been extensively deformed before deposition of lower Paleozoic strata. Subsequent folding and faulting have occurred and they are now part of a Caledonian anticlinorium that has been subject to thrusting and steep normal faulting.