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Original Article |
Reactivation Research Group, Department of Earth Sciences, University of Durham, Durham DH1 3LE, UK (e-mail: p.clegg@durham.ac.uk)
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.
Key Words: Ireland • Leinster Terrane • strain • transpression • kinematics
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