MIDCRUSTAL DETACHMENT IN THE BETIC SYSTEM OF SOUTHEAST SPAIN

The Tertiary orogenic belts of eastern Spain can be interpreted using the principles of thin-skinned thrusting with a fundamental detachment at mid-crustal level. In the eastern Betics the compression involves an oblique restacking of a stretched continental margin. Much of the shortening is transmitted on Permian and Triassic detachments which emerge as forward and back-thrust duplexes. An interpretation of the Guadarrama Range of central Spain is presented in which significant shortening is shown on a mid-crustal detachment propagating from the southeast. It is suggested that this represents the external limit of a compressive system linked to the Betics. The Pyrenees and eastern Cantabrians are a separate Tertiary compressive system again resulting from restacking of an extensional basin during the collision of Iberia and France. Previous authors have proposed mid-crustal detachment in the Pyrenees. Observation of the geological map of the Iberian Ranges suggests a broadly similar structural origin may apply, in which case the Iberian Ranges may represent the most external zone of a major Pyrenean system again linked by a mid-crustal detachment. Thus it is suggested that the whole of eastern Spain is made up of two major compressive systems linked at mid-crustal level.