Heterogeneous deformation in fold and thrust belts induced by anisotropies in the ocean topography; the South Portuguese Variscan zone example (SW Portugal).

Abstract

The Variscan fold and thrust belt related with the South Portuguese Zone presents a SW forward propagation and the coeval development of synthetic folds and thrusts pervasive at all scales. Although several models have been proposed for their formation, the estimated strain pattern is more compatible with a push from the rear induced by the north-eastern subduction zone. Although there is a strong consistence concerning the kinematics of these Variscan structures, there is an important contrast of their geometries between the inner and the external sectors, where the very low dips prevails. Although, there are some previous models suggesting that the behaviour of the more external domains could be related with the interference between the undeformed sedimentary sequence of the upper plate with the active margin of the fold and thrust belt, independent evidence of this process is lacking. The realization of scaled analogue experiments concerning the Carboniferous evolution of SW Iberia Variscides, not only show that they could induced the flat lying major thrust of the external domains, but also emphasize their important role in the structural evolution of much of the fold and thrust belt.