Crustal and uppermost mantle structure of the Porcupine Basin west of Ireland from seismic and gravity methods

Tomar, Gaurav; O’Reilly, B. M.; Prada, Manel; Hardy, R.J.J.; Bean, Christopher J.; Singh, Satish C.; Bérdi, Laura

doi:10.1016/j.marpetgeo.2022.105652

Cited by 2 publications

(5 citation statements)

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“…The Base Cretaceous Unconformity (BCU) was mapped at the interface between underlying highly faulted layers, the syn‐rift sequence and the onlapping reflectors of the post‐rift Cretaceous sequence (Figures 1–4). The top of the crystalline basement, sampled by drilling in the north of the basin (Naylor et al, 2002) and identified more widely from seismic velocities (Chen et al, 2018) and gravity modelling (Tomar et al, 2022), was mapped from its structural location at the base of the reflectors of the syn‐rift and pre‐rift sequences (Figures 1, 2, and 4). The seismic signal of the Top Basement (TB) reflector varies across the studied area (e.g.…”

Section: Methodsmentioning

confidence: 99%

“…The P reflector is widely considered to represent the crustmantle boundary. This view is based on 2D seismic data (Reston et al, 2001(Reston et al, , 2004Whiting et al, 2021), 2D prestack depth migrated seismic data and gravity modelling (Tomar et al, 2022) and wide-angle seismic data and velocity models (Chen et al, 2018;O'Reilly et al, 2006;Prada et al, 2017;Watremez et al, 2016) that identified P as the top of the underlying serpentinized mantle within the study area. Our data support this view and there are no consistent reflections within the 3D volume below P (Figure 3) that might point to a deeper top mantle.…”

Section: Lithospheric Structurementioning

confidence: 99%

“…The potential for deriving kinematic constraints on detachment evolution arises, not only from the highquality data, but also from the nature of the Porcupine Basin which shows increasing extension towards the south (Tate et al, 1993;Tomar et al, 2022;Whiting et al, 2021), with an associated southward increase in magmatic input towards the magma-richer segments…”

Section: Introductionmentioning

confidence: 99%

“…In this study, we interpret a 3D seismic reflection survey from the hyper‐extended domain of the Porcupine Basin offshore southwest of Ireland that images the ‘Porcupine Arch’ (Naylor et al, 2002) which coincides with a distinct, large, free‐air gravity anomaly high (Readman et al, 2005). The origin of the arch is debated and has been interpreted as a possible detachment fault developed at the top of serpentinized mantle (Chen et al, 2018; O'Reilly et al, 2006; Prada et al, 2017; Reston et al, 2004; Tomar et al, 2022; Watremez et al, 2016), and as a large mafic igneous intrusion below the sedimentary cover of the basin (Gagnevin et al, 2017). Our 3D seismic interpretation suggests that the Porcupine Arch is an extensional detachment, referred to as the ‘P reflector’ (P, Reston et al, 2001, 2004), with the available seismic dataset providing the most complete 3D imaging of an extensional lithospheric‐scale detachment, including its sub‐horizontal and steep frontal areas and the connection between them (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…The potential for deriving kinematic constraints on detachment evolution arises, not only from the high‐quality data, but also from the nature of the Porcupine Basin which shows increasing extension towards the south (Tate et al, 1993; Tomar et al, 2022; Whiting et al, 2021), with an associated southward increase in magmatic input towards the magma‐richer segments of the basin, as represented by the volcanic Porcupine Median Ridge (PMR, Gagnevin et al, 2017). The northern limit of the PMR occurs at the southeast corner of the Porcupine detachment (Figure 1) becoming most prominent some 25 km south‐east of the studied area.…”

Section: Introductionmentioning

confidence: 99%

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Punctuated propagation of a corrugated extensional detachment offshore Ireland

2022

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Low‐angle detachments are fundamental crustal structures found in many extensional systems and plate tectonic boundaries, including onshore extensional basins, rifted margins and mid‐oceanic ridges. Direct observations of the complete geometry of extensional detachments are rare so that aspects of our understanding of their development and evolution rely mainly on proxy observations and numerical simulations. A high‐resolution 3D seismic reflection survey Offshore West of Ireland images a complete corrugated extensional detachment, from its steep oceanward breakaway faults to its back‐rotated domal crest. The detachment surface, the P reflector, developed during the Jurassic hyperextension of the Porcupine Basin and is preserved in its slip position. It covers 95 × 35 km area and has a N‐S elongate domal shape, at right angles to the prevailing extension direction, with a crest at ca. 6.3 s two‐way travel time. It is overlain by a syn‐rift sequence offset by steep frontal faults that pass eastward into shallower, predominantly west‐dipping highly listric faults that merge downwards with the detachment. The detachment has pronounced E‐W corrugations parallel to the basin opening direction, and N‐S lineaments that correspond with the footwall cutoff lines of overlying Jurassic faults. The most significant N‐S lineaments correspond with changes in dip of the detachment. We propose that the geometry of P can be explained by a conceptual model in which the detachment was assembled from initially steep faults that developed at the front of P and back‐rotated to form listric faults during extension, with punctuated oceanward propagation of the segments of the detachment. Comparisons with 2D profiles and 3D surfaces of published detachments suggest that our conceptual model may be applicable to other detachments that accommodate extreme extension at other rifted margins and at mid‐oceanic slow and ultra‐slow spreading ridges.

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Section: Methodsmentioning

confidence: 99%