Abstract

Coastal exposures of Lower Palaeozoic rocks in SE Ireland provide an excellent opportunity to study structures formed during the sinistrally oblique Early Devonian Acadian orogeny. A highly heterogeneous assemblage of broadly contemporaneous Acadian structures is preserved and includes complex curvilinear folds, a regional, slightly clockwise transecting pressure solution cleavage, and networks of regional and smaller-scale sinistral shear zones and faults. The geometric and kinematic characteristics of these structures suggest components of NW–SE shortening, top-to-the-SW sinistral shear and a small component of top-to-the-SE thrusting. The structures are arranged into geometrically and kinematically different assemblages that define three fault-bounded structural domains, of hundreds of metres to kilometre scale. These are interpreted to result from the kinematic partitioning of the bulk triclinic sinistral transpressional strain into end-member monoclinic contraction- and wrench-dominated deformations. In this case, the nature and distribution of strain may be controlled by the presence of a pre-existing basin-bounding structure, the Courtown–Tramore Fault. The present study once again illustrates well how structural facing patterns can be used to unravel the structural complexities of kinematically partitioned transpression zones.