Evidence for pre-orogenic, Early Devonian rifting in the Variscan belt: stratigraphy and structure of the Palaeozoic cover of the Mauges Unit (Upper Allochthon, Armorican massif, France) - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles International Journal of Earth Sciences Year : 2011

Evidence for pre-orogenic, Early Devonian rifting in the Variscan belt: stratigraphy and structure of the Palaeozoic cover of the Mauges Unit (Upper Allochthon, Armorican massif, France)

Michel Ballevre
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Cécile Robin
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Abstract

The Palaeozoic sediments from the Mauges Unit (Armorican Massif, France) are the best-preserved pre-orogenic sequences belonging to the Upper Allochthon. Two coherent sequences are identified. The southern unit (Chaˆteaupanne Unit) represents the cover of the Proterozoic basement and consists of Ordovician sediments unconformably overlain by Emsian carbonates followed by Emsian to earliest Eifelian immature sandstones. The northern unit (Tombeau Leclerc Unit) consists of an Hirnantian to Emsian condensed sequence, in reverse position, that has been thrust over the southern unit. The Devonian unconformity is interpreted as evidence for an Early Devonian extension, recorded by normal faults affecting both the Early Devonian limestones and the underlying Ordovician series. This crustal extension, recorded here for the first time, is possibly related to the opening of a backarc basin (Saint-Georges-sur-Loire) associated with the subduction of an ocean located further south (Galicia- Brittany-Massif Central Ocean).

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Stratigraphy

Dates and versions

insu-00636741 , version 1 (28-10-2011)

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Céline Ducassou, Michel Ballevre, Hubert Lardeux, Cécile Robin. Evidence for pre-orogenic, Early Devonian rifting in the Variscan belt: stratigraphy and structure of the Palaeozoic cover of the Mauges Unit (Upper Allochthon, Armorican massif, France). International Journal of Earth Sciences, 2011, 100 (7), pp.1451-1475. ⟨10.1007/s00531-010-0605-3⟩. ⟨insu-00636741⟩
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