Evidence for an Early Permian Oceanic Rift in the Northern North Atlantic

Russell, Michael J.; Smythe, David

doi:10.1007/978-94-009-9803-2_15

Cited by 38 publications

(11 citation statements)

References 20 publications

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“…Roberts, 1975), Mid-Late Cretaceous (Kristofferson, 1978;Chappell and Kusznir, 2005), Early Permian (Russell and Smythe, 1978) or Late Carboniferous (Haszeldine and Russell, 1987) times; quasi-oceanic crust formed during Late Carboniferous-Early Permian (Smythe, 1989) times; stretched continental crust with zones of oceanic crust (e.g. Megson, 1987); highly stretched continental crust Hauser et al, 1995;O'Reilly et al, 1996;Morewood et al, 2005); highly stretched continental crust with concomitant igneous intrusion (Joppen and White, 1990); and crustal blocks interspersed with serpentinised mantle (Pérez-Gussinyé et al, 2001).…”

Section: Rockall Basin and Associated Marginal Basinsmentioning

confidence: 99%

Three-dimensional gravity and magnetic modelling of the Irish sector of the NE Atlantic margin

2010

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A new 3D lithospheric model has been constructed using high-resolution gravity data from the Irish National Seabed Survey. The sedimentary component of the model incorporated density variations due to laterally varying overcompaction associated with Cenozoic denudation. After optimisation based on gravity inversion, regional crustal thickness variations were defined which are in reasonable agreement with the results of wide-angle seismic experiments. High crustal extension factors (β>5) characterise the deeper parts of the Rockall and Porcupine basins and in places the model indicates extreme stretching (β>10) beneath these basins. This could be because of instability in the gravity inversion, although other recent investigations have independently suggested similarly high extension factors. In contrast, the Hatton Basin is characterised by an apparent extension factor of about 2. The modelling resolves a pattern of NE-to NNE-trending local Mesozoic basins on the margins of the Rockall Trough, helping to delineate structures that were previously only sparsely sampled by seismic surveys. It appears possible that rifts with similar trends underlie the volcanic rocks which obscure the deeper parts of the Hatton Basin. The linear trends of the basins to the south and east of Ireland are interpreted to have been inherited from a basement fabric that was initially established during the late Precambrian assembly of this basement and subsequently subjected to Caledonian and Variscan reactivation. Magnetic modelling indicates that the variations in the thickness of the crystalline crust predicted by the gravity models can explain the regional magnetic anomaly patterns over the Rockall and Porcupine basins, but that significant additional magnetic material (probably igneous rocks of both Palaeogene and Cretaceous ages) is required to explain the anomalies in the Hatton Basin region. The magnetic signature of the Rockall Basin is distinctly different to that over the basement (of similar apparent thickness) formed during mid Cretaceous (C34N) opening of the ocean basin to the south. This is an impediment to hypotheses that invoke mid Cretaceous sea-floor spreading rather than intracontinental rifting to explain the development of the basin. The exception is in the extreme south of the basin where the volcanism associated with the Barra Volcanic Ridges combined with indications of relatively strong lithosphere could be evidence of incipient ocean opening.

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Section: Rockall Basin and Associated Marginal Basinsmentioning

confidence: 99%

Three-dimensional gravity and magnetic modelling of the Irish sector of the NE Atlantic margin

2010

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“…Extensive partial melting and hence depletion of the lower crust/upper mantle component of the Rockall lithosphere may have occurred during intrusion of the Scourie dyke swarm, which extends from NW Scotland to Greenland. Further melting and depletion of the subcontinental lithosphere may have occurred during rifting-related basic volcanism in Torridonian times (Lawson 1972;Stewart 1975), subsequently during postulated Permo-Carboniferous rifting of the Rockall Trough (Russell & Smythe 1978), and yet again during the mid-to late-Cretaceous to provide basic magma associated with the development of the Rockall Trough (Roberts et al 1973b;Harrison et al 1975).…”

Section: Discussionmentioning

confidence: 99%

Petrochemistry and isotope geochemistry of early Palaeogene basalts forming the dipping reflector sequence SW of Rockall Plateau, NE Atlantic

Merriman

Taylor

Morton

1988

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S U M MARY: A transect across the passive margin SW of Rockall Plateau was drilled during DSDP Leg 81. Site 555 was located on continental crust of the Rockall Plateau. Sites 552 and 553 were located over the wedge of dipping reflectors, and Site 554 drilled the outer high at the transition from the thick wedge of dipping reflectors to normal oceanic crust. New trace-element and Pb-isotope data are presented which characterize three basalt types: (I) Dipping reflector basatts resemble depleted N-type MORBs, strongly depleted in light rare earth elements (LREEs) and other incompatible elements; they have been contaminated by U-depleted continental crust, or alternatively derived from depleted subcontinental lithosphere.(2)Outer high basalts are less strongly depleted N-type MORB and show no evidence of crustal contamination. (3) Site 552 basalts postdate the onset of subsidence of SW Rockall margin; they are relatively evolved N-type MORB derived from a source similar to that of the outer high basalts but show evidence of crustal contamination. Genesis of the dipping reflector basalts is best explained by a stretching/rifting model, not the 'subaerial seafloor spreading' model.

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“…Rosemary Bank is not compatible with the Permian age interpreted and used inferentially by Russell and Smythe (1978) …”

Section: The Inferred Late Cretaceous-early Tertiary Age Formentioning

confidence: 96%

“…The Rockall Trough is thought to be underlain by oceanic crust of Cretaceous age (Roberts, 1975; in press) but a Permian age has also been suggested by Russell (1976) and Russell and Smythe (1978). As evidence in support of a Permian age, the latter authors cite and interpret the results of an early palaeomagnetic study of Rosemary Bank by Scrutton (1971).…”

Section: Introductionmentioning

confidence: 97%