Abstract
The Cazedarnes duplex, located in the "Arc de Saint-Chinian" thrust system in the northern Pyrenean foreland, is a well exposed example of compressive hybrid duplex developed by fault-propagation folding. We present a description of this duplex and propose kinematic models of fault-propagation fold duplex formation. Contrary to standard rule of thrust system geometry, the mechanism of formation/evolution of the Cazedarnes fault-propagation fold duplex induced neither thickening of the duplex (i.e. elevation), nor roof-thrust folding: the roof of the duplex is not involved in the fault-propagation folds and is deformed independently of the duplex. This specific geometry is associated to material transfer from the anticline crests of the duplex horses towards the foreward synclines by syn-thrust normal faults branching down from the roof thrust.
