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Alpine ductile deformation of the upper Iberian collided margin (Eaux-Chaudes massif, west-central Pyrenean hinterland, France)
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  • Norbert Caldera,
  • Antonio Teixell,
  • Albert Griera,
  • Pierre Labaume,
  • Marc Guardia
Norbert Caldera
Universitat Autònoma de Barcelona

Corresponding Author:norbert.caldera@uab.cat

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Antonio Teixell
Universitat Autonoma de Barcelona
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Albert Griera
Universitat Autònoma de Barcelona
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Pierre Labaume
Géosciences Montpellier, Université de Montpellier
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Marc Guardia
Universitat Autònoma de Barcelona
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The Eaux-Chaudes massif provides keys to unravel the deep-seated deformation of the Iberian rifted margin during the Alpine orogeny in the Pyrenees. The massif conforms to an inlier of upper Cretaceous carbonate rocks within the Paleozoic basement of the western Axial Zone, originally deposited in the upper margin shelf before the Cenozoic collision. New geological mapping and cross-section construction lead to the description of the lateral structural variation from a km-scale fold nappe in the west to a ductile, imbricate fold-thrust fan in the east. The transition from a Variscan pluton to Devonian metasediments underlying the autochthonous Cretaceous induced this structural change. Recumbent folding, which involved upper Paleozoic rocks, was facilitated by a lower detachment in Silurian slates and an upper detachment in an overlying Keuper shale and evaporite thrust sheet. Remains of this allochthonous sheet form shale and ophite bodies pinched within the upper Cretaceous carbonates, conforming unusual tertiary welds. Ductile shear in the overturned limb of the Eaux-Chaudes fold nappe imparted strong mylonitic foliation in carbonate rocks, often accompanied by N-S stretching lineation and top-to-the-south kinematic indicators. The burial of the massif by basement-involved thrust sheets and the Keuper sheet, along with their Mesozoic-Cenozoic cover, account for ductile deformation conditions and a structural style not reported hitherto for the Alpine Pyrenees. Two hypotheses for the tectonic restoration of this part of the Pyrenean hinterland are proposed in this work.
10 Mar 2023Submitted to ESS Open Archive
13 Mar 2023Published in ESS Open Archive