Hyperextended basins are increasingly recognized along the outboard parts of continental margins as aborted basins created during continental break-up. Many of the concepts for understanding and modelling basin evolution and fill were developed for regions that have undergone modest crustal stretching (β < 2) and may not be valid in basins where the crust and upper mantle are heavily modified by extreme stretching. The present study uses extensive 2D and 3D seismic and well data to analyse the Late Jurassic-Cretaceous tectono-stratigraphic evolution of the Porcupine Basin, bracketing the timing of hyperextension. It is an instructive basin, offshore west of Ireland, preserving low-magnitude strain in the north, with increasing degrees of hyperextension in the south. Detailed mapping of strain domains (proximal, necking and hyperextended) across the Porcupine Basin reveals five main rift segments, each with a distinctive geometry and strain history. During early low-strain rifting, inherited crustal structures strongly influenced the rift architecture by controlling the location and geometry of fault-controlled marine depocentres. The transition from hyperextension to post-rift subsidence was marked by locally developed, unconformity-bounded, marine sequences that draped the underlying rift topography. Whilst these 'transition sequences' are dated as Tithonian above the necking domain, similar but younger Early Cretaceous transition packages developed in the hyperextended domain, suggesting extension migrated towards the rift axis during hyperextension. Early post-rift sequences were broadly distributed across the rift centre and basin flanks before strong, thermally-controlled subsidence of the hyperextended crust, along with hinging of the necking domain, locally to the point of slope failure, gave rise to axially-focused marine deposition. Hyperextension may have left the basin susceptible to intra-plate stress changes accounting for several unconformities within the post-rift fill. This study provides an improved basin-wide understanding of the tectono-stratigraphic evolution of hyperextended basins.

Sedimentary basins west of Ireland contain a number of deep seismic structures that have been variously interpreted as fault blocks, serpentinite extrusions or igneous complexes. The Porcupine Arch (PA) is a deep-level (>11 km) domal 50 km wide seismic feature associated with a prominent free-air gravity anomaly high and high P-wave velocities. Detailed seismic mapping of igneous sill complexes in the Porcupine Basin suggests a possible connection with the PA. The sills form a thick (>5 km) interconnected network extending from the PA into the flanking post-rift Cretaceous stratigraphy, suggesting that the PA may be the top of a large (ultra)mafic intrusion that fed the sills. An intrusive origin for the PA is in agreement with geophysical modelling (gravity and V p ), the seismic character of the Porcupine Arch structure and the primitive bulk composition of the Porcupine sills, and is consistent with documented regional Cenozoic uplift in the basin with the development of shallow water and the occurrence of Paleocene–Eocene deltaic depositional systems. Similar mafic–ultramafic intrusive complexes have been documented elsewhere on the northeastern Atlantic margin, including the Rockall Trough. These findings emphasize that higher heat flow in the early Cenozoic may have prevailed over the northern part of the Porcupine Basin.

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&lt;p&gt;Diffraction imaging is the technique of separating diffraction energy from the source wavefield and processing it independently. As diffractions are formed from objects and discontinuities, or diffractors, which are small in comparison to the wavelength, if the diffraction energy is imaged, so too are the diffractors. These diffractors take many forms such as faults, fractures, and pinch-out points, and are therefore geologically significant. Diffraction imaging has been applied here to the Porcupine Basin; a hyperextended basin located 200km to the southwest of Ireland with a rich geological history. The basin has seen interest both academically and industrially as a study on hyperextension and a potential source of hydrocarbons. The data is characterised by two distinct, basin-wide, fractured carbonates nestled between faulted sandstones and mudstones. Additionally, there are both mass-transport deposits and fans present throughout the data, which pose a further challenge for diffraction imaging. Here, we propose the usage of diffraction imaging to better image structures both within the carbonate, such as fractures, and below.&lt;/p&gt;&lt;p&gt;To perform diffraction imaging, we have utilised a trained Generative Adversarial Network (GAN) which automatically locates and separates the diffraction energy on pre-migrated seismic data. The data has then been migrated to create a diffraction image. This image is used in conjunction with the conventional image as an attribute, akin to coherency or semblance, to identify diffractors which may be geologically significant. Using this technique, we highlight the fracture network of a large Cretaceous chalk body present in the Porcupine, the internal structure of mass-transport deposits, potential fan edges, and additional faults within the data which may affect fluid flow pathways.&lt;/p&gt;