A geological framework for the continental margin to the west of Ireland

Abstract

On the basis of newly released magnetic data, a major fault feature is traced southwest across the Irish continental shelf; along the northwestern margin of the Slyne‐Erris Trough, the northern termination of the Porcupine Seabight, and across the Porcupine Ridge toward the vicinity of the eastern termination of the Gibbs Fracture Zone. This major fault passes into, and is identified with, the Great Glen Fault system. Apparent sinistral movement of the order of 50–70 km along the fault displaces a feature tentatively identified as the Highland Boundary Fault. A weak magnetic feature is also identified that might represent the course of the Moine Thrust. The Slyne‐Erris Trough has been referred to as part of a ‘failed’ rift associated with the Seabight opening, but might instead be related to the wrench faulting similar to that seen elsewhere along the Great Glen Fault line. An apparent transform movement along the portion of the fault at the head of the Porcupine Seabight may relate to rifting and the generation of oceanic crust in the central part of the Seabight. Two possible courses for the westward continuation of the Hercynian Front are recognized, and a major Tertiary intrusive centre is identified and related to a zone of dyke swarms.

From orogenic collapse to rifting: A case study of the northern Porcupine Basin, offshore Ireland

“…6A and B) and its role on controlling the deformation may be only due to rheological contrasts with the adjacent Grenvillian Basement. To the west, N-S structures are parallel to the Porcupine High that is mostly composed of Precambrian and Palaeozoic rocks (Riddihough and Max, 1976;Max, 1978;Naylor et al, 1999). To the east, they run along the Ruadan High, originally described as a Mesozoic shearing and inversion feature (Tate, 1993;Naylor et al, 2002) but herein interpreted as part of a buried Variscan nappe gently reactivated afterwards separating the North Mohling and Porcupine basins (Fig.…”