The Arén Croup was deposited synchronously to the growth of the Boixols thrust. Sedimentation took place in siliciclastic marine and alluvial environments. The growth of a footwall syncline affected the geometry of the basin fill by adding drowning and uplifting movements. Such a mechanism might be common to those settings where fault propagation folds develop. In the Arén Croup, this differential subsidence mechanism was not able to overprint the identified sedimentary cycle
