Crustal structure of the SW-Moroccan margin from wide-angle and reflection seismic data (the DAKHLA experiment) Part A: Wide-angle seismic models

Klingelhoëfer, Frauke; Labails, Cinthia; Cosquer, Emmanuel; Rouzo, S.; Géli, Louis; Aslanian, Daniel; Olivet, Jean-Louis; Sahabi, Mohamed; Nouzé, Hervé; Unternehr, Patrick

doi:10.1016/j.tecto.2008.07.022

Cited by 59 publications

(65 citation statements)

References 24 publications

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“…While the Nova Scotia margin has been subject to numerous marine geophysical studies (e.g. Funck et al, 2004;Wu et al, 2006), the conjugate African segment remains fairly unknown, except for the northernmost segment (Holik et al, 1991;Contrucci et al, 2004;Jaffal et al, 2009;Klingelhoefer et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Deep crustal structure of the North-West African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)

et al. 2015

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International audienceThe structure of the Moroccan and Nova Scotia conjugate rifted margins is of key importance for understanding the Mesozoic break-up and evolution of the northern central Atlantic Ocean basin. Seven combined multichannel reflection (MCS) and wide-angle seismic (OBS) data profiles were acquired along the Atlantic Moroccan margin between the latitudes of 31.5° and 33° N during the MIRROR seismic survey in 2011, in order to image the transition from continental to oceanic crust, to study the variation in crustal structure, and to characterize the crust under the West African Coast Magnetic Anomaly (WACMA).The data were modeled using a forward modeling approach. The final models image crustal thinning from 36 km thickness below the continent to approximately 8 km in the oceanic domain. A 100 km wide zone characterized by rough basement topography and high seismic velocities up to 7.4 km/s in the lower crust is observed westward of the West African Coast Magnetic Anomaly. No basin underlain by continental crust has been imaged in this region, as has been identified north of our study area. Comparison to the conjugate Nova Scotian margin shows a similar continental crustal thickness and layer geometry, and the existence of exhumed and serpentinized upper mantle material on the Canadian side only. The oceanic crustal thickness is lower on the Canadian margin

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Section: Introductionmentioning

confidence: 99%

Deep crustal structure of the North-West African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)

et al. 2015

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“…5) [16,32,38]. Its con tinental nature is confirmed by basement gneisses penetrated by Site 544 DSDP and by a salt diapir drilled by Site 546, as well as by characteristic rotated faulted blocks.…”

Section: Atlantic Margin Of the United States And Southeastern Canadamentioning

confidence: 89%

“…According to the results of the DAKHLA wide angle seismic profiling experiment, the high velocity lower crust (Vp = 7.0-7.5 km/s), more than 10 km thick [38], probably related to underplating was estab lished (Fig. 5).…”

Section: Atlantic Margin Of the United States And Southeastern Canadamentioning

confidence: 98%

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Development of passive volcanic margins of the Central Atlantic and initial opening of ocean

Melankholina

Sushchevskaya

2015

Geotecton.

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Geological and geophysical data on the Central Atlantic are discussed in order to elucidate the tectonic setting of the initial magmatic activity, rifting, and breakup resulting in the origination of Mesozoic ocean. The structural, magmatic, and historical aspects of the problem are considered. It has been established that the initial dispersed rifting and low capacity magmatism at proximal margins was followed by the migra tion of the process toward the central part of region with the formation of distal zones and the development of vigorous magmmatism, further breakup of the lithosphere and ocean opening. Magmatism, its sources, and the features of newly formed magmatic crust at both the rifting and breakup stages of margin development are discussed and compared with subsequent spreading magmatism. Sr, Nd, and Pb isotopic compositions show that the magmatic evolution of the Central Atlantic proximal margins bears the features of two enriched components, one of which is related to the EM 1 source, developing only at the North American margin. Another enriched component typical of the province as a whole is related to the EM 2 source. To a lesser extent, this component is expressed in igneous rocks of Guyana, which also bear the signature of the MORB type depleted source typical of spreading tholeiites in the Atlantic Ocean. Similar conditions are assumed for subsequent magmatism at the distal margins and for the early spreading basalts in the adjacent Atlantic belt, which also contain a small admixture of enriched material. A comparison of the magmatism at the margins of Central and North Atlantic reveals their specificity distinctly expressed in isotopic compositions of igneous rocks. In contrast to the typical region of the North Atlantic, the immediate melting of the enriched lithos pheric source without the participation of plume related melts is reconstructed for the proximal margins of the Central Atlantic. At the same time, decompression and melting in the lithosphere could have been deter mined by the thermal effect of the Central Atlantic hot plume. This is testified by the intense melting in a short time interval over a vast area; the generation of rather homogeneous melts and creation of the thick magmatic crust; the radial arrangement of the dikes intruded in the course of plume ascent; as well as by the data of seis mic tomography indicating the occurrence of the hot upper mantle material, which has kept the "memory" of the action of a shallow seated Mesozoic plume. The formation of the Central Atlantic plume can be pre sumably regarded as a result of upwelling remobilisation adove the ancient African superplume and the rear rangement of the deep structure in Triassic and Jurassic times.

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“…8), we would draw attention to the results of the DAKHLA wide-angle seismic experiment (Klingelhoefer et al 2009) north of our AOI, offshore Western Sahara. The DAKHLA experiment provides crustal profiles extending on to the Central Atlantic Jurassic oceanic crust and shows a similar crustal structure in the OCT to that determined by OCTek gravity anomaly inversion in this area.…”

Section: South American Sectionmentioning

confidence: 99%

Crustal structure of the conjugate Equatorial Atlantic Margins, derived by gravity anomaly inversion

Kusznir

Roberts²,

Alvey³

2018

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The crustal structure of the Equatorial Atlantic conjugate margins (South America and West Africa) has been investigated using 3D gravity anomaly inversion, which allows for (1) the elevated geothermal gradient of the lithosphere following rifting and break-up and (2) magmatic addition to the crust during rifting and break-up. It is therefore particularly suitable for the analysis of rifted margins and their associated ocean basins. Maps of crustal thickness and conjugate-margin stretching, derived from gravity anomaly inversion, are used to illustrate how the Equatorial Atlantic opened as a set of stepped rift-transform segments, rather than as a simple orthogonal rifted margin. The influence of the transform faults and associated oceanic fracture zones is particularly clear when the results of the gravity anomaly inversion are combined with a shaded-relief display of the free-air gravity anomaly. A set of crustal cross-sections has been extracted from the results of the gravity inversion along both equatorial margins. These illustrate the crustal structure of both rifted-margin segments and transform-margin segments. The maps and cross-sections are used to delineate crustal type on the margins as (1) inboard, entirely continental, (2) outboard, entirely oceanic and (3) the ocean-continent transition in between where mixed continental and magmatic crust is likely to be present. For a given parameterization of melt generation the amount of magmatic addition within the ocean-continent transition is predicted by the gravity inversion. One of the strengths of the gravity-inversion technique is that these predictions can be made in the absence of any other directly acquired data. On both margins anomalously thick crust is resolved close to a number of oceanic fracture zones. On the South American margin we believe that this thick crust is probably the result of post-break-up magmatism within what was originally normal-thickness oceanic crust. On the West African margin, however, three possible origins are discussed: (1) continental crust extended oceanwards along the fracture zones; (2) oceanic crust magmatically thickened at the fracture zones; and (3) oceanic crust thickened by transpression along the fracture zones. Gravity inversion alone cannot discriminate between these possibilities. The cross-sections also show that, while 'normal thickness' oceanic crust (c. 7 km) predominates regionally, local areas of thinner (c. 5 km) and thicker (c. 10 km) oceanic crust are also present along both margins. Finally, using maps of crustal thickness and thinning factor as input to plate reconstructions, the regional palaeogeography of the Equatorial Atlantic during and after break-up is displayed at 10 Ma increments.Supplementary material: Detailed illustrations of the crustal-thickness mapping, the crustal cross-sections and the plate reconstructions are available at: https://doi

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Crustal structure of the SW-Moroccan margin from wide-angle and reflection seismic data (the DAKHLA experiment) Part A: Wide-angle seismic models

Cited by 59 publications

References 24 publications

Deep crustal structure of the North-West African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)

Deep crustal structure of the North-West African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)

Development of passive volcanic margins of the Central Atlantic and initial opening of ocean

Crustal structure of the conjugate Equatorial Atlantic Margins, derived by gravity anomaly inversion

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