EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reconstructing the pre–Variscan puzzle of Cambro–Ordovician basement rocks in the western Mediterranean region of Gondwana

Cecilio Quesada1, José Javier Álvaro2, and Josep Maria Casas3
Cecilio Quesada et al.
  • 1Instituto Geológico Minero de España, Madrid, Spain (
  • 2Instituto de Geociencias (CSIC-UCM), Madrid, Spain
  • 3Departament de Dinàmica de la Terra i de l’Oceà, Institut de Recerca GEOMODELS, Universitat de Barcelona, Barcelona, Spain

In today’s western Mediterranean region, Variscan and Alpine thrusts and shear zones combine to hamper a correct identification and palinspastic reconstruction of Cambro-Ordovician sequences. However, gap-related stratigraphic, climatically sensitive facies associations, sedimentary, volcanosedimentary, biogeographic, biodiversity and detrital zircon data mainly made available during the last two decades allow envisaging a new palaeogeographic scenario by linking proximal-to-distal transects across the western and eastern branches of the Ibero-Armorican Arc. Variscan parautochthonous and autochthonous domains are represented palaeogeographically by, from SW to NE: (i) the Central Iberian, West Asturian-Leonese and Cantabrian zones of the Iberian Massif and their laterally correlative Central Armorican Domain, fringed marginally by the Ossa-Morena and North Armorican thinned outer margin of Gondwana, reminiscent of the rift axis during the Cambrian; and (ii) the southeastern Pyrenees, Occitan and SW Sardinia domains, fringed marginally by the slope-to-basinal South Armorican, Thiviers-Payzac, Albigeois and northeastern Pyrenees domains. These proximal-to distal transects of West Gondwana record a diachronous SW-to-NE migration of evaporites, phosphorites and maximum peak of trilobite diversity, related to the counter-clockwise migration of the Gondwana supercontinent, supported by a gradual modification of detrital zircon provenance. Both branches of the Ibero-Armorican Arc also display a diachronous migration of Cambro-Ordovician rift-to-drift conditions associated with distinct igneous manifestations (volcanosedimentary and plutonic). This migration is related to the development of the Furongian (Toledanian) to Mid-Late Ordovician (Sardic) geodynamic events, in response to gap-related thermal doming, subaerial denudation and magmatic activity evolving from calc-alkaline to tholeiitic affinity.

How to cite: Quesada, C., Álvaro, J. J., and Casas, J. M.: Reconstructing the pre–Variscan puzzle of Cambro–Ordovician basement rocks in the western Mediterranean region of Gondwana, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9215,, 2020