| Summary: | Permian and Triassic sedimentation in the Iberian Ranges, took place in a cratonic area inside the Iberian Plate. This Plate was undergoing an extensional regime because of its location between two broad rifting areas, the Tethys and the Protoatlantic. The evolution of these two major geotectonic realms resulted in the development of a complex multidirectional system of grabens and troughs, which transected the Variscan fold belt and its European foreland (Ziegler, 1988). In the framework of the southward-propagating Arctic-Atlantic rift system and the westward propagation of the Tethys rifts, a progressive regional extension took place with sorne Late-Hercynian fault systems being reactivated. In the Molina de Aragón area, the sedimentation took place as flood-dominated alluvial fans with paleocurrents towards the NE related to the main NW-SE fracture system. More to the southeast, in the Albarracin area, more organízed alluvial fan systems were developed with a transition between proximal and distal facies (jig. 11). A major prograding event resulted in a coarsening-upwards sequence from mudstones to sandstones and conglomerates. The relative stability of alluvial channels was higher here than in the northern area.A general reactivation of the NW-SE fracture system (jig. 12) resulted in a larger area of sedimentation and the lower Buntsandstein sediments onlapping the Saxonian facies. The three 21. lowest Buntsandstein units (<<Conglomerados de la Hoz del Gallo>>, < > and <<Nivel de Prados») configurare a fining-upwards megasequence with a distintive evolution in the fluvial style.
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