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Structure profonde de la Marge Nord Gascogne et du Bassin Armoricain

Abstract : The formation and the evolution of the North Biscay Margin are highly linked to the opening of the Bay of Biscay, the North Atlantic Ocean and the formation of the Pyrenean. The new compilation of old and new seismic data (reflection and refraction), in correlation with results of deep drillings and continental studies (for instance on Parentis Basin and Western Approaches Basin), enabled us to define the evolution (in time and space) of the sedimentary cover; construction of regional time and depth structure and isopach maps. Four tectonic phases are identified : two during the rifting (upper Jurassic and Aptian) and two during the pyrenean compression (upper Cretaceous/Palaeocene and Eocene). "Catastrophic" tectonic and sedimentary events have affected the margin during the end of the rifting. The 80 km wide Armorican Basin is a wide Continent/Ocean Transition zone with a substratum (layer with the velocities of 7.4-7.6 km/s), interpreted as serpentinized mantle, and covered by post-rift flat-lying sediments. This Cretaceous sedimentary basin collapses at the end of the rifting or during the initiation of the oceanic accretion. The distance between the true oceanic domain and the continental domain (not thinned) is constant along the whole margin. The crustal thinning happens exclusively under the narrow continental slope; tilted blocks, situated at the foot of the continental slope, seem to have a minor role in the processes of the crustal thinning. This geometry, similar to the geometry of the Parentis Basin, is not atypical. The current geodynamic models do not explain the geometry of the North Biscay Margin; the thinning cannot be explained by pure extension alone.
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https://tel.archives-ouvertes.fr/tel-00605279
Contributor : Isabelle Thinon <>
Submitted on : Friday, July 1, 2011 - 9:46:45 AM
Last modification on : Tuesday, March 31, 2020 - 5:14:24 PM
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Isabelle Thinon. Structure profonde de la Marge Nord Gascogne et du Bassin Armoricain. Sciences de la Terre. Université de Bretagne occidentale - Brest, 1999. Français. ⟨tel-00605279⟩

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