Terrane assemblage of the Leinster Massif, SE Ireland, during the Lower Palaeozoic

Abstract

Compilation of Irish Geological Survey mapping is used to construct a synthesis of the tectonic evolution of the Leinster Massif during the Lower Palaeozoic. The massif is interpreted as a series of NE-SW trending tectonostratigraphic terranes of diverse origin and provenance brought together along major sinistral transcurrent faults. With minor discrepancies the age of these terranes decreases from SE to NW. The Precambrian basement Rosslare terrane is succeeded by the Early Cambrian continental margin Cullenstown-Cahore terrane. In the Waterford-Wicklow terrane Late Cambrian-Early Ordovician accreted ocean floor materials are overlain by a Late Ordovician volcanic arc. The Early to Mid-Ordovician accreted ocean floor Dublin terrane to the NW is overthrust by the Early Cambrian continental margin Bray terrane and is followed to the NW by the mainly Silurian Midlands terrane. These terranes were juxtaposed after substantial sinistral movement along transcurrent faults during the Silurian. Consolidation of the massif also took place from SE to NW. Stages in the consolidation are marked by the intrusion of the Saltees (437 Ma), Carrigmore (415 Ma) and Leinster (404 Ma) stitching plutons. Fault movement ceased before the deposition of Late Devonian and Carboniferous sediments on a linking unconformity across the massif.