Séminaire de Nicolas Saspiturry, Géoressources & Environnement, Bordeaux

How permian / cretaceous rifts inheritances control the preservation of a hyper-thinned rift in an orogen and its thermal history from its creation to its reactivation ?

Séminaire de Nicolas Saspiturry, 2019

Abstract

First, the presentation aims to document the Permian structural inheritance in Western Pyrenees. The Bidarray Basin, that is now in contact with late-Variscan granulites, forms a Permian N0-20° extensional basin developing on the southern ank of an immature MCC. The preservation of the Permo-Triassic paleogeography, indicates that there is no Mesozoic lateral motion between Iberia and Europe in this part of Pyrenees.
Next, the talk will focus on the Mauléon Cretaceous rift system based on a geological cross-section incorporating newly acquired eld data and seismic interpretations. The Barremian Aptian symmetric sag basin initiates in response to lower crustal thinning. During Albian to Cenomanian time, the continental crust thinning was accommodated by a sequence of antithetic detachments responsible for the Mauléon hyperthinned rift apparent nal symmetry (Fig. A). The third part of the presentation deals with the processes responsible for rift preservation in the Pyrenean orogen. Respectively at rst and second order, the Early Cretaceous and Permian inherited structures favored the inversion of the hyperthinned basin into a hybrid pop-up, in which the opposite edges present dierent tectonic reactivation styles (Fig. B).
Finally, we will discuss the 3D repartition of the Cretaceous thermal anomaly using RSCM methodology. The paleo thermal gradients increases basinward from 30°C/km to 60°C/km, inducing a complex competition between brittle vs. ductile deformation. We also emphasized the major role of hyper-extension inheritance on the post-collisional thermicity, controlling the abnormal current gradient, i.e. ~25°C/km (Fig. B).