Crustal structure across the Grand Banks-Newfoundland Basin Continental Margin - II. Results from a seismic reflection profile

Lau, K. W. Helen; Louden, K. E.; Deemer, S.; Hall, Jérémy; Hopper, John R.; Tucholke, Brian E.; Holbrook, W. S.; Larsen, Hans Christian

doi:10.1111/j.1365-246x.2006.02989.x

Cited by 49 publications

(84 citation statements)

References 32 publications

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“…This asymmetry indicates that the continental crust separated southeast of the rift axis. The zone of exhumed continental mantle is widest along IAM‐9 [ Dean et al , 2000], but continental mantle was also exhumed in the southern Newfoundland Basin before oceanic spreading started in late Hauterivian time (∼129 Ma) [ Whitmarsh and Miles , 1995; Lau et al , 2006a]. …”

Section: Discussionmentioning

confidence: 99%

Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada

et al. 2006

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We present a compressional seismic velocity profile of the crust of the eastern margin of the Grand Banks of Newfoundland, Canada. This velocity model was obtained by a tomographic inversion of wide‐angle data recorded on a linear array of 24 ocean bottom seismometers (OBSs). At the landward side, we imaged a crustal thickness of 27 km in Flemish Pass and beneath Beothuk Knoll, which is thinner than the 35‐km‐thick crust of the central Grand Banks. We therefore assume that the eastern rim of the Grand Banks stretched uniformly by 25%. Farther seaward, the continental crust tapers rapidly beneath the continental slope to ∼6 km thickness. In the distal margin we find a 60‐km‐wide zone with seismic velocities between 5.0 and 6.5 km s−1 that thins to the southeast from 6 to 2 km, which we interpret as highly extended continental crust. Contrary to other seismic studies of the margins of the Grand Banks, we find seismic velocities of 8 km s−1 and higher beneath this thin crustal layer in the continent‐ocean transition. We conclude that mantle was locally emplaced at shallow levels without significant hydration from seawater or serpentinized mantle was removed along a décollement in the final stages of continental rifting. The outer edge of highly extended continental crust borders a 25‐km‐wide zone where seismic velocities increase gradually from 6.3 km s−1 just below the top of acoustic basement to 7.7 km s−1 at 5 km below basement. We interpret this area as a relatively narrow zone of exhumed and serpentinized continental mantle. Seaward, we imaged a thin and laterally heterogeneous layer with a seismic velocity that increases sharply from 5.0 km s−1 in basement ridges to 7.0 km s−1 at its base, overlying mantle velocities between 7.8 and 8.2 km s−1. We interpret this area as unroofed mantle and very thin oceanic crust that formed at an incipient, magma‐starved, ultraslow spreading ridge. A comparison of the conjugate rifted margins of the eastern Grand Banks and the Iberia Abyssal Plain show that they exhibit a similar seaward progression from continental crust to mantle to oceanic crust. This indicates that before continental breakup, rifting exhumed progressively deeper sections of the continental lithosphere on both conjugate margins. A comparison between the continent‐ocean transition of the Grand Banks and Flemish Cap shows that the final phase of continental rifting and the formation of the first oceanic crust required more time at the Grand Banks margin than at the southeastern margin of Flemish Cap.

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Section: Discussionmentioning

confidence: 99%

Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada

et al. 2006

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“…This change in crustal thickness is associated with a strong continentward dip of the Moho underneath the necking zone that can be up to 35°(e.g. Lau et al 2006;Osmundsen and Ebbing 2008;van Avendonk et al 2009). The distal margin is formed by less than 10 km thick that wedges out oceanwards and is replaced by exhumed subcontinental mantle that grades into oceanic crust (for a more detailed description, see Péron-Pinvidic and Manatschal 2008).…”

Section: The Alpine Tethys Rifted Marginsmentioning

confidence: 95%

Unravelling the interaction between tectonic and sedimentary processes during lithospheric thinning in the Alpine Tethys margins

Mohn

Manatschal

Müntener

et al. 2010

Int J Earth Sci (Geol Rundsch)

161

163

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The discovery of exhumed continental mantle and hyper-extended crust in present-day magma-poor rifted margins is at the origin of a paradigm shift within the research field of deep-water rifted margins. It opened new questions about the strain history of rifted margins and the nature and composition of sedimentary, crustal and mantle rocks in rifted margins. Thanks to the benefit of more than one century of work in the Alps and access to world-class outcrops preserving the primary relationships between sediments and crustal and mantle rocks from the fossil Alpine Tethys margins, it is possible to link the subsidence history and syn-rift sedimentary evolution with the strain distribution observed in the crust and mantle rocks exposed in the distal rifted margins. In this paper, we will focus on the transition from early to late rifting that is associated with considerable crustal thinning and a reorganization of the rift system. Crustal thinning is at the origin of a major change in the style of deformation from high-angle to lowangle normal faulting which controls basin-architecture, sedimentary sources and processes and the nature of basement rocks exhumed along the detachment faults in the distal margin. Stratigraphic and isotopic ages indicate that this major change occurred in late Sinemurian time, involving a shift of the syn-rift sedimentation toward the distal domain associated with a major reorganization of the crustal structure with exhumation of lower and middle crust. These changes may be triggered by mantle processes, as indicated by the infiltration of MOR-type magmas in the lithospheric mantle, and the uplift of the Briançonnais domain. Thinning and exhumation of the crust and lithosphere also resulted in the creation of new paleogeographic domains, the Proto Valais and Liguria-Piemonte domains. These basins show a complex, 3D temporal and spatial evolution that might have evolved, at least in the case of the Liguria-Piemonte basin, in the formation of an embryonic oceanic crust. The re-interpretation of the rift evolution and the architecture of the distal rifted margins in the Alps have important implications for the understanding of rifted margins worldwide, but also for the paleogeographic reconstruction of the Alpine domain and its subsequent Alpine compressional overprint.

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“…2) have revealed a 120 km wide transitional zone outboard of volcanic basement, drilled within 30 km of thinned continental crust during the Deep Sea Drilling Project . This zone of transitional crust was subdivided into a landward 70 km zone of topographically subdued, exhumed serpentinized mantle peridotites (Bullock & Minshull 2005) similar to transitional crust interpreted further south on the Iberian and Newfoundland margins (Boillot et al 1987;Pickup et al 1996;Whitmarsh et al 1996;Chian et al 1999;Dean et al 2000;Lau et al 2006b;Sibuet et al 2007a;Tucholke & Sibuet 2007;Deemer et al 2009;Welford et al 2010b), and a less well-constrained 50 km zone of exhumed serpentinized basement ridges identified to the south on both margins (Boillot et al 1980;Beslier et al 1993;Shipboard Scientific Party 1998;Dean et al 2000;Henning et al 2004;van Avendonk et al 2006;Welford et al 2010b). …”

Section: The Irish Atlantic Marginmentioning

confidence: 99%

Comparison of lithosphere structure across the Orphan Basin–Flemish Cap and Irish Atlantic conjugate continental margins from constrained 3D gravity inversions

Welford

Shannon

O’Reilly

et al. 2012

JGS

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127

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Regionally constrained 3D gravity inversion results on the Orphan Basin-Flemish Cap and the Irish Atlantic conjugate continental margins are compared to investigate crustal structure, early rifting history and geological evolution of this part of the North Atlantic. The full-crustal density anomaly distributions provide some of the first depth images of how rifted structures compare along and across these conjugate margins. Broad similarities in crustal structure are identified with some noticeable differences, linked to rifting and crustal stretching processes. Extreme crustal thinning (stretching factors >3.5) is indicated beneath much of the southern Porcupine Basin, the western half of West Orphan Basin, the eastern half of Jeanne d'Arc Basin, the southeastern half of East Orphan Basin and in pockets beneath Rockall Basin. This appears to have resulted in the serpentinization (and possible exhumation) of mantle lithosphere on the Irish Atlantic and Flemish Cap margins but not beneath Orphan Basin. A simple evolution model is proposed for the early stages of rifting between the margins. It is suggested that ancient orogenic sutures played an important role in controlling the northward migration of rifting and the rotation and displacement of Flemish Cap out of Orphan Basin.Supplementary material: Enlarged maps from this paper are available at www.geolsoc.org.uk/SUP18527.

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Crustal structure across the Grand Banks-Newfoundland Basin Continental Margin - II. Results from a seismic reflection profile

Cited by 49 publications

References 32 publications

Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada

Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada

Unravelling the interaction between tectonic and sedimentary processes during lithospheric thinning in the Alpine Tethys margins

Comparison of lithosphere structure across the Orphan Basin–Flemish Cap and Irish Atlantic conjugate continental margins from constrained 3D gravity inversions

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