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Norbert CALDERA

Thesis: Inversion tectonics in the proximal Iberian continental Margin: the case of the Eaux-Chaudes massif, west-central Pyrenees

Supervisors:
Antonio TEIXELL and Albert GRIERA
Universitat Autònoma de Barcelona

Major Results

The Eaux-Chaudes massif is re-interpreted as a large-scale recumbent fold, defined by the Upper Cretaceous rocks. High ductile strain observed, especially in the reverse limb, attests a deformation style rarely reported for the alpine Pyrenees.

Abstract

Tectonic inversion of rifted margins generate structural complexity often poorly understood due to the limited outcrops of post-basement rocks. The Eaux-Chaudes massif conforms an outcrop of the Pyrenean hinterland and a key-marker to constrain the structural style and paleotemperature conditions during the Alpine orogeny.
This massif has been interpreted as a complex duplex structure. Nevertheless, our observations and analyses lead us to propose a large-scale recumbent fold for the Upper Cretaceous rocks, cored by folded Paleozoic metasediments.

The reinterpretation of this massif is supported by macro and microstructural data evidencing ductile deformation, especially well-developed in the reverse limb of the large structure. Autochthonous and normal limb show low-grade deformation.
Unexpected high temperatures for the Upper Cretaceous rocks (in the lower greenschist facies) have been identified by Raman Spectroscopy of Carbonaceous Material analyses performed along the recumbent fold, supporting field and laboratory data which evidence ductile deformation.
The ductility and metamorphic temperature bear similarities with the lower Helvetic nappes of the Alps.

Large-scale recumbent fold (Les Eaux-Chaudes), defined by the Upper Cretaceous rocks.
Raman Hight Temperatures in Upper Cretaceous Rocks (300-355°C)

Recumbent folding in the Upper Cretaceous Eaux‐Chaudes massif: A Helvetic‐type nappe in the Pyrenees?

Caldera, N, Teixell, A, Griera, A, Labaume, P, Lahfid, A. Recumbent folding in the Upper Cretaceous Eaux‐Chaudes massif: A Helvetic‐type nappe in the Pyrenees?. Terra Nova. 2021; 00: 1– 0

keywords: Pyrenean orogeny, Recumbent fold nappe, RSCM paleothermometry, Hinterland tectonics, Ductile deformation

DOI: https://doi.org/10.1111/ter.12517