A structural profile of Caledonian deformation in Down

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Abstract
Summary: Coastal exposure in County Down provides an almost complete cross section of the continuation of the Southern Uplands fold belt in Ireland. Intensely folded Ordovician and Silurian turbidite successions are segmented by at least ten major strike parallel faults. In each segment the fold envelope descends northward but the strike faults throw up progressively younger sediments to the south. A system of upright folds, with slaty cleavage axial plane, but locally transecting, becomes progressively complicated southward by the clear development of two further phases of folding and cleavage with constant geometry and opposing vergence. The chronology of cleavage, folding, later kink-band and brittle deformation is punctuated by successive late Caledonian lamprophyre dyke swarms. The total structure is consistent with a model of diachronous deformation and northward translation and rotation at a destructive plate margin.