Crustal structure variations along the NW-African continental margin: a comparison of new and existing models from wide-angle and reflection seismic data

Type Article
Date 2016-04
Language English
Author(s) Klingelhoefer FraukeORCID1, Biari Youssef1, 2, 5, Sahabi Mohamed2, 3, Aslanian DanielORCID1, Schnabel Michael, Matias Luis4, Benabdellouahed Massinissa5, Funck Thomas6, Gutscher Marc-Andre5, Reichert Christian3, Austin James A.7
Affiliation(s) 1 : IFREMER, Dept Marine Geosci, ZI Pointe Diable, F-29280 Plouzane, France.
2 : Univ Chouaib Doukkali, Fac Sci, Lab Geosci Marines & Sci Sols, URAC 45, BP 20, El Jadida 24000, Morocco.
3 : Geozentrum Hannover, BGR, Stilleweg 2, D-30655 Hannover, Germany.
4 : Inst Dom Luiz, Ed C6,Piso 3, P-1749016 Lisbon, Portugal.
5 : Univ Europeene Bretagne, Brest Inst Univ Europeen Mer, UMR Domaines Ocean 6538, Pl Nicolas Copernice, F-29280 Plouzane, France.
6 : GEUS Geol Survey Denmark & Greenland, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark.
7 : Univ Texas Austin, John A & Katherine G Jackson Sch Geosci, Inst Geophys, JJ Pickle Res Campus,Bldg 196,Rm 3-254, Austin, TX 78712 USA.
Source Tectonophysics (0040-1951) (Elsevier Science Bv), 2016-04 , Vol. 674 , P. 227-252
DOI 10.1016/j.tecto.2016.02.024
WOS© Times Cited 15
Keyword(s) Moroccan continental margin, Wide-angle seismic, Passive margins, Deep structure, Plate reconstruction
Abstract Deep seismic data represent a key to understand the geometry and mechanism of continental rifting. The passive continental margin of NW-Africa is one of the oldest on earth, formed during the Upper Triassic–Lower Liassic rifting of the central Atlantic Ocean over 200 Ma. We present new and existing wide-angle and reflection seismic data from four study regions along the margin located in the south offshore DAKHLA, on the central continental margin offshore Safi, in the northern Moroccan salt basin, and in the Gulf of Cadiz.

The thickness of unthinned continental crust decreases from 36 km in the North to about 27 km in the South. Crustal thinning takes place over a region of 150 km in the north and only 70 km in the south. The North Moroccan Basin is underlain by highly thinned continental crust of only 6-8 km thickness. The ocean-continent transition zone shows a variable width between 40 and 70 km and is characterised by seismic velocities in between those of typical oceanic and thinned continental crust. The neighbouring oceanic crust is characterised by a thickness of 7-8 km along the complete margin. Relatively high velocities of up to 7.5 km/s have been imaged between magnetic anomalies S1 and M25, and are probably related to changes in the spreading velocities at the time of the Kimmeridgian/Tithonian plate reorganisation.

Volcanic activity seems to be mostly confined to the region next to the Canary Islands, and is thus not related to the initial opening of the ocean, which was associated to only weak volcanism. Comparison with the conjugate margin off Nova Scotia shows comparable continental crustal structures, but 2-3 km thinner oceanic crust on the American side than on the African margin.
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Klingelhoefer Frauke, Biari Youssef, Sahabi Mohamed, Aslanian Daniel, Schnabel Michael, Matias Luis, Benabdellouahed Massinissa, Funck Thomas, Gutscher Marc-Andre, Reichert Christian, Austin James A. (2016). Crustal structure variations along the NW-African continental margin: a comparison of new and existing models from wide-angle and reflection seismic data. Tectonophysics, 674, 227-252. Publisher's official version : https://doi.org/10.1016/j.tecto.2016.02.024 , Open Access version : https://archimer.ifremer.fr/doc/00316/42685/