Inversion of a transfer system into lateral ramps: An example from the South-Central Pyrenees (Spain)

Abstract

Field work in the South-Central Pyrenees suggests that omission contacts (i.e. younger over older rocks) occur at the base of the Cadi unit (Cadi thrust), and pass laterally into thrusts. This change occurs across tear faults which are present in the hangingwall of the Cadi thrust sheet and which controlled the deposition of Upper Cretaceous sediments (Adraen formation). Detailed mapping in the contact area between the Nogueres and Cadi units has shown that the actual thrust geometry in the study area is controlled by preexisting normal and transfer faults which developed in an already compressional context. Lateral ramps or tear faults develop depending on the angle between the pre-existing extensional transfer fault and the thrust transport direction.