07 Oct 2020

07 Oct 2020

Review status: a revised version of this preprint was accepted for the journal SE and is expected to appear here in due course.

Evolution of the Iberian Massif as deduced from its crustal thickness and geometry of a mid-crustal (Conrad) discontinuity

Puy Ayarza1, José Ramón Martínez Catalán1, Ana Martínez García2, Juan Alcalde2, Juvenal Andrés1,2, José Fernando Simancas3, Immaculada Palomeras1, David Martí2,4, Irene DeFelipe2, Chris Juhlin5, and Ramón Carbonell2 Puy Ayarza et al.
  • 1Geology Department, Salamanca University. Pza de la Merced, s/n. Salamanca 37008, Spain
  • 2Geosciences Barcelona, CSIC. Lluis Solé i Sabaris, s/n. Barcelona 08028, Spain
  • 3Geodynamics Department, Granada University. Av/ de la Fuente Nueva, s/n. Granada 18071, Spain
  • 4Lithica SCCL. Avinguda Farners 16, Santa Coloma de Farners, Girona 17430, Spain
  • 5Department of Earth Sciences, Uppsala University. Villavägen 16, Uppsala, 75236, Sweden

Abstract. Normal incidence seismic data provide the best images of the crust and lithosphere. When properly designed and continuous, these sections greatly contribute to understanding the geometry of orogens and, together with surface geology, to unravel their evolution. In this paper we present an almost complete transect of the Iberian Massif, the westernmost exposure of the European Variscides. Despite the heterogeneity of the dataset, acquired during the last 30 years, the images resulting from reprocessing with a homogeneous workflow allow us to clearly define the crustal thickness and its internal architecture. The Iberian Massif crust, formed by the amalgamation of continental pieces belonging to Gondwana and Laurussia (Avalonian margin) is well structured in upper and lower crust. A conspicuous mid-crustal discontinuity is clearly defined by the top of the reflective lower crust and by the asymptotic geometry of reflections that merge into it, suggesting that it has often acted as a detachment. The geometry and position of this discontinuity can give us insights on the evolution of the orogen, i.e. of the effects and extent of the late Variscan gravitational collapse. Also, its position and the limited thickness of the lower crust in central and NW Iberia constraints the response of the Iberian microplate to Alpine shortening. This discontinuity is here observed as an orogeny-scale feature with characteristics compatible with those of the worldwide, Conrad discontinuity.

Puy Ayarza et al.

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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Puy Ayarza et al.

Data sets

Reassessing the lithosphere: SeisDARE, an open access seismic data repository Irene DeFelipe, Juan Alcalde, Minika Ivandic, David Martí, Mario Ruíz, Ignacio Marzán, Jordi Díaz, P. Ayarza, Imma Palomeras, Jose Luis Fernandez Turiel, Cecilia Molina, Isabel Bernal, Larry Brown, Roland Roberts, and Ramón Carbonell

Puy Ayarza et al.


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Short summary
Vertical incidence seismic profiling on the Iberian Massif images a mid-crustal scale discontinuity at the top of the reflective lower crust. This feature shows that upper and lower crustal reflections merge into it, thus suggesting that it has often behaved as a detachment. The orogen scale extension of this discontinuity, present in Gondwanan and Avalonian affinity terranes into the Iberian Massif demonstrates its relevance, leading us to interprete it as the Conrad Discontinuity.