Imaging igneous rocks on the North Atlantic rifted continental margin

Roberts, A. W.; White, R. S.; Christie, P. A. F.

doi:10.1111/j.1365-246x.2009.04306.x

Cited by 26 publications

(34 citation statements)

References 51 publications

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“…These values are compatible with what is observed on the Fugloy Ridge (iSIMM Faroes line in Fig. 5d) (Roberts et al 2009), a little to the north of the main axis of the GIFR.…”

Section: Greenland -Iceland -Faroe Ridgesupporting

confidence: 91%

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A review of the NE Atlantic conjugate margins based on seismic refraction data

Funck

Gaina

Geissler

et al. 2016

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The NE Atlantic region evolved through several rift episodes, leading to break-up in the Eocene that was associated with voluminous magmatism along the conjugate margins of East Greenland and NW Europe. Existing seismic refraction data provide good constraints on the overall tectonic development of the margins, despite data gaps at the NE Greenland shear margin and the southern Jan Mayen microcontinent. The maximum thickness of the initial oceanic crust is 40 km at the Greenland-Iceland-Faroe Ridge, but decreases with increasing distance to the Iceland plume. High-velocity lower crust interpreted as magmatic underplating or sill intrusions is observed along most margins but disappears north of the East Greenland Ridge and the Lofoten margin, with the exception of the Vestbakken Volcanic Province at the SW Barents Sea margin. South of the narrow Lofoten margin, the European side is characterized by wide margins. The opposite trend is seen in Greenland, with a wide margin in the NE and narrow margins elsewhere. The thin crust beneath the basins is generally underlain by rocks with velocities of .7 km s 21 interpreted as serpentinized mantle in the Porcupine and southern Rockall basins; while off Norway, alternative interpretations such as eclogite bodies and underplating are also discussed.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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“…These values are compatible with what is observed on the Fugloy Ridge (iSIMM Faroes line in Fig. 5d) (Roberts et al 2009), a little to the north of the main axis of the GIFR.…”

Section: Greenland -Iceland -Faroe Ridgesupporting

confidence: 91%

“…This model would also be consistent with nearby lines that show a highvelocity lower crust (e.g. the iSIMM Faroes line: Roberts et al 2009). Crustal velocities gradually decrease towards the Faroes, starting some 100 km away from the islands.…”

Section: Greenland -Iceland -Faroe Ridgesupporting

confidence: 85%

A review of the NE Atlantic conjugate margins based on seismic refraction data

Funck

Gaina

Geissler

et al. 2016

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“…The traveltimes of P-wave refractions and wide-angle reflections within this data set have been previously analysed by Parkin & White (2008), White & Smith (2009) and Roberts et al (2009). Parkin & White (2008) focussed on the oceanic ends of both the Faroes and Hatton Bank Dip line profiles and joint reflection and refraction tomography resolved unusually thick oceanic crust (>8 km).…”

Section: Introductionmentioning

confidence: 99%

Identification and inversion of converted shear waves: case studies from the European North Atlantic continental margins

Eccles

White²,

Christie

2009

Geophysical Journal International

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S U M M A R YWide-angle shear wave arrivals, converted from compressional to shear waves at crustal interfaces, enable crustal Vp/Vs ratios to be determined which provide valuable constraint on geological interpretations. Analysis of the converted shear wave phases represents the next logical step in characterizing the crustal structure and composition following multichannel seismic structural imaging and tomographic inversion of the wide-angle compressional wave phases. In this offshore study across two passive margins extending from stretched continental to fully oceanic crust, the high-data density (2-10 km ocean bottom seismometer, OBS, spacing) and a consistent, efficient conversion interface produced shear wave data sets suitable for traveltime inversion. The shear waves were recorded by three orthogonal geophones in each OBS. Arrival phases, visible to 180 km offset, were identified using their arrival times, moveout velocities and particle motions. Across the North Atlantic volcanic rifted continental margins studied, breakup was accompanied by the eruption of large volumes of basalts of the North Atlantic Igneous Province. The interface between post-volcanic sediments and the top of the basalts provides the dominant conversion boundary across the oceanic crust and the continent-ocean transition. However, the shear wave data quality was significantly diminished at the continental ends of the profiles where the thick basalt flows and hence this conversion interface feathers out and crustal attenuation increases. Initial modelling of the converted shear wave phases was carried out using a layer-based approach with arrivals converted on the way up used to constrain the Vp/Vs ratio of the post-volcanic sedimentary sequence beneath each OBS. To produce a model with continuous crustal S-wave velocities, the compressional wave velocities beneath the sediment-top basalt interface were transformed into starting shear wave velocities using a constant value of Vp/Vs and the inversion carried out by specifying the appropriate ray path. Once the data set had been fully interpreted, correction of the traveltimes to effective symmetric ray paths enabled us to apply a regularized grid inversion. Such inversions are less subjective than the layer-based approach and yield more robust minimum structure results with quantifiable errors, except in the vicinity of a known subbasalt low-velocity zone encountered on the Faroes margin. Monte Carlo analyses were performed for this approach; the average model from multiple inversions using randomized starting models and traveltimes shows the structure required by the traveltimes and the model standard deviation gives an estimate of uncertainty. Model and inversion parametrizations were fully tested and optimum parameters chosen for compressional and shear wave inversions. This allows, after appropriate model smoothing, an estimate to be made of the spatial variation of the Vp/Vs ratio within the crust. There are marked gradients in Vp, Vs and Vp/Vs ratio across the continent-ocean ...

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“…A pre-volcanic low-velocity layer up to 1 km thick has also been modelled from a refraction seismic line located approximately 30 km in a easterly direction from the junction of transect sections 4 and 5 (Raum et al 2005;Roberts et al 2009) (Fig. 1b).…”

Section: Iceland -Faroe Ridge Stratigraphymentioning

confidence: 99%

The stratigraphy and structure of the Faroese continental margin

Ólavsdóttir

Eidesgaard

Stoker

2016

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This paper presents a summary of the stratigraphy and structure of the Faroese region. As the Faroese area is mostly covered by volcanic material, the nature of the pre-volcanic geology remains largely unproven. Seismic refraction data provide some indications of the distribution of crystalline basement, which probably comprises Archaean rocks, with the overlying cover composed predominantly of Upper Mesozoic (Cretaceous?) and Cenozoic strata. The Cenozoic succession is dominated by the syn-break-up Faroe Islands Basalt Group, which crops out on the Faroe Islands (where it is up to 6.6 km thick) and shelf areas; post-break-up sediments are preserved in the adjacent deep-water basins, including the Faroe-Shetland Basin. Seismic interpretation of the post-volcanic strata shows that almost every sub-basin in the Faroe-Shetland Basin has been affected by structural inversion, particularly during the Miocene. These effects are also observed on the Faroe Platform, the Munkagrunnur Ridge and the Fugloy Ridge, where interpretation of lowgravity anomalies suggests a large-scale fold pattern. The structure of the Iceland-Faroe Ridge, which borders the NW part of the Faroe area, remains ambiguous. The generally thick crust, together with the absence of well-defined seawards-dipping reflectors, may indicate that much of it is underlain by continental material.

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Imaging igneous rocks on the North Atlantic rifted continental margin

Cited by 26 publications

References 51 publications

A review of the NE Atlantic conjugate margins based on seismic refraction data

A review of the NE Atlantic conjugate margins based on seismic refraction data

Identification and inversion of converted shear waves: case studies from the European North Atlantic continental margins

The stratigraphy and structure of the Faroese continental margin

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