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University of Aberdeen/Canada-Newfoundland Offshore Petroleum Board 5th floor TD Place, 140 Water Street, St John’s, Newfoundland, Canada, A1C 6H6
Analysis of well and seismic data indicates that both the Jeanne d’Arc Basin on the Grand Banks of Newfoundland and the Porcupine Basin on the continental shelf off western Ireland were undergoing extension characterized by subsidence and rotation of fault blocks during mid-Aptian to late Albian times. Stratigraphic sequences in these conjugate basins developed in response to synchronous rift tectonism.
The base of each syn-rift sequence is defined by an angular unconformity which formed in response to regional uplift. This mid-Aptian rift-onset unconformity is buried beneath a depositional sequence characterized by retrogradational coastal sediments overlain by progradational coastal sediments in each basin. However, the lower retrogradational deposits dominate the syn-rift sequence in the Jeanne d’Arc Basin, while the upper progradational deposits dominate the syn-rift sequence in the northern Porcupine Basin. The relative dominance of sediments deposited along either transgressive or regressive coastlines was mainly determined by the local interplay of variable rates of rift-induced subsidence and sediment input.
The initiation of seafloor spreading between the Flemish Cap/Orphan Knoll and Goban Spur/Porcupine Bank continental margins near the end of Albian time resulted in the establishment of regional thermal subsidence, rapid coastal transgression and fully marine deposition above a locally-developed sequence-bounding unconformity.
