Preprints
https://doi.org/10.5194/se-2020-126
https://doi.org/10.5194/se-2020-126
21 Aug 2020
 | 21 Aug 2020
Status: this preprint was under review for the journal SE but the revision was not accepted.

A first estimation of the contraction related to vertical axis rotation: the case of the Ibero-Armorican Arc formation

Josep Maria Casas, Joan Guimerà, Joaquina Alvarez-Marron, and Ícaro Días da Silva

Abstract. Different models have been proposed to explain the formation of the Ibero-Armorican Arc, which require significant vertical axis rotations, at the end of the Variscan orogeny. Estimates of the amount of contraction (horizontal shortening) needed for these rotations range from 54 % to 91 % perpendicularly to the arc. These estimates are compared with coeval deformational structures developed in two areas of the orogen, one in the autochthonous hinterland underlying the Galicia-Trás-os-Montes Zone in the southern branch of the arc, and the other in the Cantabrian Zone foreland in the core of the arc. From this analysis it follows that the late Variscan deformation together with the subsequent Alpine contraction is not sufficient to explain the formation of the Ibero-Armorican Arc as a secondary structure by means of vertical axis rotations. Our analysis suggests this arc is mainly a primary, or non-rotational curve, slightly modified by ca. 10 % of superposed contraction during late Carboniferous and/or Alpine times. Moreover, we propose that the assumptions underlying the interpreted geometry of the arc be re-evaluated, and we discuss the role of late-Variscan regional strike-slip faults in the Iberian and in the Armorican massifs that probably acted consecutively before and during the contraction of the arc.

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Josep Maria Casas, Joan Guimerà, Joaquina Alvarez-Marron, and Ícaro Días da Silva
 
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Status: closed
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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
Josep Maria Casas, Joan Guimerà, Joaquina Alvarez-Marron, and Ícaro Días da Silva
Josep Maria Casas, Joan Guimerà, Joaquina Alvarez-Marron, and Ícaro Días da Silva

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Short summary
Many orogenic belts exhibit arcuate form in map view. We deal with the different models proposed to explain the formation of the Ibero-Armorican Arc in the western European Variscan Belt. We suggest this arc is primary slightly modified by superposed contraction during late Carboniferous and/or Alpine times. We discuss the role of late-Variscan regional strike-slip faults in the Iberian and in the Armorican massifs that probably acted consecutively before and during the contraction of the arc.