The structural and stratigraphic framework of the Irish Rockall Trough

Abstract

The Irish sector of the Rockall Trough is the largest of the sedimentary basins offshore Ireland and is virtually unexplored. This study establishes the first regional structural and stratigraphic framework of the Mesozoic and Tertiary fill of the Irish sector of the Trough with the aim of assessing its hydrocarbon potential. Major structural features of the Irish Rockall Trough and the adjacent part of the Irish Continental Shelf have been mapped using a combination of 9000 km of confidential and released regional seismic lines, satellite gravity data and a compilation of marine and aeromagnetic data. A sequence stratigraphic framework for the Mesozoic and Tertiary has been established using the seismic data tied to ten wells in adjacent basins (Erris and Slyne troughs and Porcupine Basin) and to one well in the southern part of the UK Rockall Trough. A major advance was the recognition of new Mesozoic perched basins and tilted fault blocks on both margins of the Trough in areas previously interpreted as shallow basement. A further 12000 km of seismic data acquired in the summer of 1996 indicate that a considerable thickness of sediment is present in these basins containing a fill analogous to the Slyne and Erris troughs. The configuration of the perched basins suggests that a major linked rift system, coincident with the site of the present-day Rockall Trough, existed during the early Mesozoic. Within the Trough, a number of sub-basins have been identified, characterized by syn-rift wedges of interpreted Jurassic to Early Cretaceous age.