Rifting, crustal attenuation and subsidence in the Bay of Biscay

Charpal, O. De; Guennoc, Pol; Montadert, L.; Roberts, D.G.

doi:10.1038/275706a0

Cited by 209 publications

(103 citation statements)

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“…(3) The geophysical signatures of the main lithospheric faults and shear zones responsible for mantle unroofing are strong seismic reflectors, the most famous of them being the S reflector of the Armorican and Galicia margins (De Charpal et al 1978;Le Pichon & Barbier 1987;Hoffmann & Reston 1992;Sibuet 1992;Krawczyk & Reston 1995;Reston et al 1996), named H in the Iberia Abyssal Plain Krawczyk et al 1996;Manatschal et al 2001). The geological signature of the tectonic shearing and exhumation of subcrustal mantle is the foliation and brecciation of the peridotite and intruded gabbro, caused by deformation at falling temperature and decreasing pressure (Girardeau et al , 1998(Girardeau et al , 1999Kornprobst & Tabit 1988;Beslier et al 1990Beslier et al , 1996Cornen et al 1996a,b).…”

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Non-volcanic rifted margins, continental break-up and the onset of sea-floor spreading: some outstanding questions

Boillot

Froitzheim

2001

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During the last 20 years, regional studies on the West Iberia margin and on the former margins of the Tethys have considerably advanced the understanding of processes related to continental break-up and the onset of sea-floor spreading. However, some questions remain outstanding. To tentatively answer these, a coherent interpretation of available data is proposed, based on the detachment fault concept applied to the continental as well as the oceanic lithosphere, and on the hypothesis of a multi-staged rifting process. The interpretation addresses the nature of the lower crust beneath non-volcanic passive margins, the origin of ophicalcites, the probable time gap between syn-or post-rift crystallization of gabbros and extrusion of basalts on the sea floor, and the significance of dipping reflectors within oceanic lithosphere adjacent to non-volcanic passive margins. The interpretation also considers the symmetry v. asymmetry of continental rifting and break-up, the location of the ocean-continent boundary, and the possible association of magnetic quiet zones with ultramafic sea floor (serpentinized peridotite) bordering non-volcanic passive margins.

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Non-volcanic rifted margins, continental break-up and the onset of sea-floor spreading: some outstanding questions

Boillot

Froitzheim

2001

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“…Refraction data on the shelf (Holder & Bott, 1971) suggested that the Moho shoaled from 25 km beneath the shelf break to 12 km near the continent-ocean transition where, from the available refraction data, the observed ductile crust was estimated to be only 3 km -2-in thickness. These early results showed that the observed thinning of the crust could not be fully explained by the extension of lO-15% in the upper crust and resulted in the suggestion that the lower ductile had thinned by a greater amount (De Charpal et al, 1978;r Montadert et al, 1979). The drill, dredge and reflection data / suggested that at the end of rifting a system of half-graben about 2.5 km below sea level existed adjacent to the continent-ocean transition (Montadert, Roberts et al, 1977.…”

Section: Introductionmentioning

confidence: 99%

A seismic refraction and reflection study of the continent-ocean transition beneath the north Biscay margin

1982

Deep Sea Research Part B. Oceanographic Literature Review

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(Ziegler, 1978 and this volume) and the adjacent margins of the North Atlantic Ocean.It has become clear that extension may also occur in strike slip and convergent settings (Bally & Snelson, 1979), and examples include the Western Mediterranean (Biju-Duval et al., 1977) , the Pannonian Basin (Royden & Sclater, 1981) and the Great Basin (Profett, 1977).The occurrence of crustal extension, expressed by rifting, in these different geological settings emphasises that very little is known of the mechanisms producing the rifting process, including its initiation, which cause the profound changes in crustal structure revealed by attenuation and ultimately by the formation of a spreading ocean basin. . "Several innovative theoretical models (McKenzie, 1978;Royden et al., 1980;Royden and Keen, 1980; Sclater & Christie, 1981;Turcotte, 1981) have proposed mechanisms for lithospheric extension and have attempted to evaluate quantitatively the mechanical and thermal consequences of each model in terms of histories of margin and basin subsidence. These models may have a potential practical value in predicting the thermal history and thus the degree of.hydrocarbon maturity in sedimentary basins formed in response to a lithospheric extension (Royden & Keen, 1980;Royden et al., 1980;Sclater & Christie, 1980). However, a rigorous description of the deep crustal structure beneath a cratonic sedimentary basin or a passive continental margin that would provide sufficient data to quantify the extension in order to constrain these models has been lacking as has a comprehensive study of the geological and thermal history of basins that have evolved in response to lithospheric extension.In this paper, we present some of the results of a detail seismic refraction and reflection study of the northern or Armorican margin of the Bay of Biscay. The study examined the deep crustal structure (Montadert, Roberts et al., 1977;Montadert et al. , 1979). -The overall tectonic style consists of tilted and rotated fault blocks whose downthrow is consistently down toward the ocean. The pattern of faults is probably en-echelon or anastomosing. Many of the fault blocks are bounded by listric normal faults ( Fig. 2a) with throws of up to 3000 m. The listric faults flatten out with depth close to the top of a sub-horizontal group of reflectors called 'S' (Fig. 2b). Comparison with early refraction data suggested that this reflector corresponded to the boundary between a 4.9 and 6.3 km.sec ^ layer (Avedik & Howard, 1979). De Charpal et al. (1979 and Montadert et al. (1979) interpreted the 6.3 km. sec ^ refractor as the boundary between the upper brittle and the lower ductile continental crust. Refraction data on the shelf (Holder & Bott, 1971) suggested that the Moho shoaled from 25 km beneath the shelf break to 12 km near the continent-ocean transition where, from the available refraction data, the observed ductile crust was estimated to be only 3 km -2-in thickness. These early results showed that the observed thinning of the crust could not be ful...

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“…It has been tentatively interpreted as the seismic signature of a syn-rift detachment fault (Wernicke and Burchfiel, 1982;Boillot et al, 1987;Hoffman and Reston, in press) and as décollement at the brittle-ductile transition within the thinned continental crust (de Charpal et al, 1978;Montadert et al, 1979;Sibuet, 1992). The S reflector may also represent the tectonic contact between continental crustal material and underlying serpentinized peridotite, marking a detachment fault that was rooted in the mantle (Boillot et al, 1989(Boillot et al, ,1992.…”

Section: The S Reflectormentioning

confidence: 99%