Reply to discussion on ‘Middle Jurassic shear zones at Cap de Creus (eastern Pyrenees, Spain): a record of pre-drift extension of the Piemonte–Ligurian Ocean?’ Journal of the Geological Society, London , 174, 289–300

Abstract

We welcome the discussion by Elena Druguet, Jordi Carreras and Jochen Mezger (Druguet et al. 2017) of our paper (Vissers et al . 2017 b ) in which we report Jurassic 40Ar/39Ar ages from shear zones at Cap de Creus, NW Spain. The authors argue that our interpretation of these results and the inferred development of the Cap de Creus shear zones during Jurassic stretching and opening of the Piemonte Ligurian ocean contradicts structural and tectonic evidence, and that it is not sufficiently supported by geochronological data. Below we first consider their structural and tectonic arguments from the tectonic–palaeogeographical scale down to the smaller field scale, and then proceed to discuss our Ar/Ar results. Druguet et al. (2017) note that prior to the Oligo-Miocene rifting event the Corso-Sardinian block was fixed east of NE Iberia, hence that the rocks at Cap de Creus were not located at the Jurassic pre-drift continental margin and that the northern Cap de Creus shear zones could not have formed as normal faults related to continental rifting. This palaeogeographical argument builds on a previous hypothesis by Stampfli & Borel (2002), Stampfli et al. (2002) and Stampfli & Hochard (2009) in which Iberia, the Corso-Sardinian block and the Brianconnais domain formed one single microcontinent. This hypothesis, however, must be discarded on the basis of recent palaeomagnetic work on Sardinia by Advokaat et al. (2014) showing that between Late Jurassic and Eocene time Sardinia underwent no vertical-axis rotations relative to Eurasia and was fixed to Europe in a rotated position that results from post-Eocene deformation, whereas all available evidence indicates that Iberia was located much further west and underwent some 35° counterclockwise rotation during the Cretaceous (van Hinsbergen et al. 2017; Vissers et al . 2017 a ). Sardinia, …