Received: 11 Sep 2020 – Accepted for review: 30 Sep 2020 – Discussion started: 07 Oct 2020
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.
Reassessing the lithosphere: SeisDARE, an open access seismic data repositoryIrene 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 https://digital.csic.es/handle/10261/101879
Puy Ayarza et al.
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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.
Vertical incidence seismic profiling on the Iberian Massif images a mid-crustal scale...