Conjugate margins of Canada and Europe: Results from deep reflection profiling

Keen, C. E.; Peddy, Carolyn P.; Voogd, B. de; Matthews, D. H.

doi:10.1130/0091-7613(1989)017<0173:cmocae>2.3.co;2

Cited by 70 publications

(31 citation statements)

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“…3) on line 85-3 has previously been suggested to represent a sharp continent-ocean boundary ( Fig. 3; Keen et al, 1989). In light of the inferred presence of wide zones of exhumed serpentinized mantle with low relief on the west Iberia margin, Louden and Chian (1999) suggested that this layer consisted of exhumed serpentinized mantle.…”

Section: Discussionmentioning

confidence: 80%

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Flemish Cap-Goban Spur conjugate margins: New evidence of asymmetry

Gerlings¹,

Louden²,

Minshull³

et al. 2012

Geology

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We present the combined results of deep multichannel refl ection and refraction seismic surveys across the Flemish Cap-Goban Spur conjugate margin pair (North Atlantic), which we use to infer rifting style and breakup. Profi les on both margins cross magnetic anomaly 34 and extend into oceanic crust, making it possible to observe the complete history from continental rifting through to the formation of initial oceanic crust. The deep multichannel seismic (MCS) refl ection data have previously been used to support a model of symmetric pure shear extension followed by asymmetric breakup and a sharp continent-ocean boundary. Using both types of seismic data, our results indicate instead that asymmetric structures are formed during all stages of rifting, breakup, and complex transition to oceanic spreading. The differing nature of the two oceancontinent transition zones is particularly striking. For Flemish Cap, our reprocessed image of the MCS profi le clearly shows tilted fault blocks beneath back-tilted sediment packages, consistent with a wide region of highly thinned continental crust inferred from wideangle seismic data. In contrast, normal incidence and wide-angle seismic data for the Goban Spur transition zone indicate the presence of exhumed serpentinized mantle.

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Section: Discussionmentioning

confidence: 80%

“…Deep seismic refl ection data were used for the fi rst time in the 1980s to derive the rifting style of a passive conjugate margin pair (Keen et al, 1989). Seismic refl ection profi les from the Flemish Cap-Goban Spur margins ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Flemish Cap-Goban Spur conjugate margins: New evidence of asymmetry

Gerlings¹,

Louden²,

Minshull³

et al. 2012

Geology

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“…(a) Continental rift stage: crustal-scale cross-section of the Rhine Graben modified after Brun et al (1992) and four-layer-type analogue model modified after Beslier (1991). (b) Passive margin stage: restored conjugate margins of Canada and Europe modified after Keen et al (1989) and four-layer-type analogue model modified after Brun & Beslier (1996). and ECORS consortia, in the north and in the south of the Graben (Brun et al .…”

Section: Necking Of a Four-layer Lithosphere (A) Continental Rift Stagementioning

confidence: 99%

Narrow rifts versus wide rifts: inferences for the mechanics of rifting from laboratory experiments

Brun

1999

Philosophical Transactions of the Royal Society of London. Seri

276

256

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Laboratory experiments on analogue models of the lithosphere are useful tools to study tectonic processes and, in particular, to test physical hypotheses. They complement numerical modelling because the inherent limitations of each method are different. The basic principles of the method are recalled with particular application to models simulating the brittle-ductile layering of continental crust and lithosphere using sand and silicone putties to simulate the frictional and viscous behaviour of rocks. A selection of experiments is used to examine the role of rheology on the development of crustal-scale extensional structures: continental rifts, passive margins, wide extended domains, and core complexes. The difference between narrow rifts and wide rifts is attributed to the type of mechanical instability that can develop for a given type of lithospheric strength profile: namely necking versus spreading. Necking occurs preferentially in a stable lithosphere that has a four-layer-type of strength profile with the greatest strength located in the sub-Moho mantle. It gives birth to narrow rifts, from continental rifts to passive margins. Spreading occurs preferentially in a thickened lithosphere whose strength profile, after thermal relaxation, exhibits maximum strength at the base of upper brittle crust. It gives birth to wide rifts, such as the Basin and Range of the western United States or the Aegean. Core complexes are not considered to represent a particular mode of extension but are anomalies in wide rifts.

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“…However, many regions are not amenable to such studies, either because their present geographical location has resulted in an uneven distribution of data or because plate kinematic reconstructions do not provide an unambiguous reconstruction of the positions of the rifting continents. Nevertheless, a few conjugate-rifted margin comparisons have been recently carried out: the Australia-Antarctica margin system (Etheridge et al 1989); the western Europeaneastern Canadian margins (Keen et al 1989;Sibuet 1992;Srivastava and Verhoef 1992); the margins of the Greenland 'Geological Survey of Canada Contribution 31693…”

Section: Introductionmentioning

confidence: 99%

Deep seismic reflection data across the conjugate margins of the Labrador Sea

Keen¹,

Potter²,

Srivastava³

1994

Can. J. Earth Sci.

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A deep seismic reflection transect of the conjugate margins of the Labrador Sea is described, which represents one of the few data sets of this kind. A characteristic reflectivity is ascribed to a 120 km wide ribbon of very thin crust that may be either thinned continental crust, which has perhaps been intruded, or oceanic crust, perhaps modified by the proximity of the continent. Most of the major changes in crustal thickness and in the subsidence and sedimentation patterns on the margins occur landward of these transitional zones, which are found on both margins. An interpretation of these regions as continental in origin is compatible with other seismic observations on the west Greenland margin, but does not match the magnetic anomaly interpretation, which requires the transitional crust to be oceanic in origin. Models that satisfy the gravity anomalies and the subsidence history have been used to assist in interpreting the seismic data. The subsidence models include the effects of decompression melting during lithospheric extension and rifting, and we predict the thickness of igneous crust produced. However, the gravity models suggest that a lower crustal layer may extend farther inland below the Labrador shelf than is predicted by magmatic underplating. The present seismic results, combined with the other geophysical data, are consistent with a pure shear model of lithospheric stretching, with faulting confined to the upper crust. Many of the problems raised by this data set are similar to those identified in comparing the nonvolcanic margin of Iberia with the conjugate Grand Banks margin in the North Atlantic. If the transition zone results from stretching the continental lithosphere, then a large component of the very thin crust there must consist of igneous material formed by melting. Under these conditions a sharp, vertical ocean-continent boundary would be unlikely.Un profil transversal de sismique rCflexion profonde des marges conjugtes de la mer du Labrador est dtcrit, il reprCsente un parmi les rares ensembles de donntes de ce genre. Une rtflectivitt caractkristique est assignee h un ruban, d'une largeur de 120 krn, de crofite trbs mince qui pourrait &tre soit une crobte continentale amincie rCsultant d'une intrusion possible, ou soit une crofite octanique qui aurait pu etre modifite en raison de sa proximitt du continent. GCnCralement, les changements majeurs qui affectent 1'6paisseur de la crobte, la subsidence et les structures ~Cdimentaires sur les marges sont concentrCs du c6tC des terres dans ces zones de transition qui se trouvent sur les deux marges. L'interprCtation de ces rtgions fondte sur une origine continentale est compatible avec d'autres observations sismiques faites sur la marge du Groenland, mais elle est en dtsaccord avec l'interprktation des anomalies magnCtiques qui indiquent que la croiite transitionnelle est d'origine octanique. Les modbles compatibles avec les anomalies gravimttriques et conformes a l'histoire de la subsidence ont Ctt utilists pour aider interprCter les donnke...

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Conjugate margins of Canada and Europe: Results from deep reflection profiling

Cited by 70 publications

References 0 publications

Flemish Cap-Goban Spur conjugate margins: New evidence of asymmetry

Flemish Cap-Goban Spur conjugate margins: New evidence of asymmetry

Narrow rifts versus wide rifts: inferences for the mechanics of rifting from laboratory experiments

Deep seismic reflection data across the conjugate margins of the Labrador Sea

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