The Ibero-Armorican Arc: A collision effect against an irregular continent?

Abstract

The Ibero-Armorican Arc is the main Variscan macrostructure in western Europe. Although it was recognized in the 1920s, its genesis is still debatable and the proposed models for its generation questionable. However, even if some doubts persist, it seems that most agree on the general geodynamic evolution of this virgation in both branches. In the Middle to Late Devonian, Iberia was deformed by a sinistral transpressive regime, while in the northern branch thrusting events were predominant. In the Carboniferous, a dextral transpression begins to predominate in the Armorican branch, while the southern branch was deformed by southward thrusting. In an attempt to correlate these events, we propose that during the Late Devonian a Cantabrian indentor moved northward, producing the oblique closure of the southern part of the Rheic Ocean and an almost orthogonal closure in central Europe. In the Carboniferous, the collision with the irregular margin of Laurasia induced a rotation of the indentor; the intracontinental deformation was then achieved by dextral transpression in the northern branch and thrusting in the southern one.