La estructura del domo de la Rabassa y del sector oriental del sinclinal de Llavorsí (Pirineo Central)

Abstract

The Rabassa dome and the Llavorsí syncline are two structural units of the Hercynian basement of the Central Pyrenees. Their internal structure results from the superposition of hercynian thrusts and folds. Detailed structural analysis reveals that the pre-main cleavage structures are very significant. They are a southward directed thrust, which overthrusts the Silurian rocks over the highest positioned Devonian materials, and close hectometric to kilometric-sized folds. These pre-cleavage folds give rise to the antiform and the synfom structures of the Rabassa dome and the Llavorsí syncline respectively. Their axial planes are inclined to the south and strike from NE-SW to NW-SE. This early folding and the present topographic surface make the Silurian black shales overlying the Devonian formations to appear in some synform structures, which correspond to the bands of Silurian rocks extended along the centre of the Llavorsí syncline. Shortening related to the main cleavage development produces decametric and smaller scale folds of bedding and make the previous folds to be tighter. The early structural configuration is only modified by a set of E-W trending northward dipping inverse faults which cut the southern limb of the Llavorsí syncline.