The Devonian of the upper part of the Valle de Aran, Central Pyrenees

The Devonian stratigraphy in the Valle de Arán of the Central Pyrenees, is different from that of its surroundings. In this area a zone of graded greywackes occurs together with a rock type of supposedly littoral facies, in an oblong basin, which has been filled longitudinally by sediments slipping down in turbidity currents from the delta slope in the West, thus building up the graded sediments of the deepest part of this basin. The Hercynian orogeny has folded this area very strongly, developing an intense cleavage. This cleavage together with repeated alternation of sediments of different competency caused the enormous variety of secondary folds with their special tectonical problems.