Wide-angle seismic control on the development of the Munster Basin, SW Ireland

Abstract

Abstract Three wide-angle seismic profiles were acquired from onshore southern Ireland during VARNET-96. These data provide the only subsurface seismic images of a series of predominantly Late Palaeozoic sedimentary basins. The Dingle Basin is a broadly symmetrical rift on the Dingle peninsula, but assumes a half-graben geometry to the east. The southern syn-rift basin margin is defined by the north-dipping Dingle Bay-Galtee Mountains Line. A south-dipping normal fault at Kerry Head marks the northern basin margin in the west, with displacement on this structure decreasing towards the east. The Dingle Basin is separated from the Munster Basin to the south by a basement horst. Seismic data strongly suggest that the Killarney-Mallow Fault Zone, located on the southern margin of this positive feature, is the Munster Basin northern syn-rift marginal fault. The preserved extensional displacement on this detachment decreases from c. 2.5 km in northern Iveragh, to c. 1 km at Mallow, suggesting that the fault tips out to the east of Mallow. A tilted fault block, possibly cored by shallow granite, is imaged in the northern Munster Basin. This fault terrace is bounded to the south by the Cork-Kenmare Line. The combined Munster Basin and South Munster Basin succession thickens across the Cork-Kenmare Line to a maximum thickness of 8 km on the Beara peninsula. A tectonic thickness of 6 km of sediment is modelled at the Old Head of Kinsale, increasing to 7 km in the southwest.