The structure of the South-Central-Pyrenean fold and thrust belt as constrained by subsurface data

Authors

  • J.A. MUÑOZ Institut de Recerca Geomodels, departament de dinàmica de la Terra i de l’oceà, Facultat de Geologia, universitat de Barcelona C/ Marti i Franquès s/n, 08028 Barcelona.
  • J. MENCOS Departament de Ciències Ambientals, Universitat de Girona C/ Maria Aurèlia Campmany 69, 17003 Girona.
  • E. ROCA Institut de Recerca Geomodels, departament de dinàmica de la Terra i de l’oceà, Facultat de Geologia, universitat de Barcelona C/ Marti i Franquès s/n, 08028 Barcelona.
  • N. CARRERA Institut de Recerca Geomodels, departament de dinàmica de la Terra i de l’oceà, Facultat de Geologia, universitat de Barcelona C/ Marti i Franquès s/n, 08028 Barcelona.
  • O. GRATACÓS Institut de Recerca Geomodels, departament de dinàmica de la Terra i de l’oceà, Facultat de Geologia, universitat de Barcelona C/ Marti i Franquès s/n, 08028 Barcelona.
  • O. FERRER Institut de Recerca Geomodels, departament de dinàmica de la Terra i de l’oceà, Facultat de Geologia, universitat de Barcelona C/ Marti i Franquès s/n, 08028 Barcelona.
  • O. FERNÁNDEZ Repsol Exploración, Dirección de Geología, Schubertgasse 22/13, 1090 Wien, Austria.

Keywords:

Pyrenees, seismic data, cut-off and branch line

Abstract

The interpretation of the available seismic lines of the South-Central-Pyrenean fold and thrust belt, conveniently tied with the exploration wells, define the main structural features of this realm of the Pyrenees. In particular, they define the geometry and areal extension of the autochthonous foreland underneath the sole thrust. The mapping of
several selected structural lines brings constraints for the structural interpretation of the South-Central Pyrenees, including the cut-off lines between selected stratigraphic horizons of the autochthonous foreland and the branch line between basement-involved thrust sheets and the sole thrust. The thrust salient which characterizes at surface the geometry of the South-Pyrenean fold and thrust belt contrasts with the linear trend of these structural lines at subsurface. This salient has been the result of a secondary progressive curvature developed since Middle Eocene times by thrust displacement gradients during verthrusting of the South-Pyrenean thrust sheets above a Paleogene autochthonous sequence. Displacement gradients resulted from the uneven distribution of weak salt layers, mostly the Triassic and the Upper Eocene ones. The minimum amount of South-directed displacement from early Middle
Eocene times to Late Oligocene is 52km, which would be significantly higher if internal shortening by folding and cleavage/fracture development as well as hanging-wall erosion is added.

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Published

2018-12-20

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