PALEOMAGNETIC EVIDENCE FOR ROTATION OF THE IBERIAN PENINSULA AND THE EXTERNAL BETIC CORDILLERA, SOUTHERN SPAIN

Paleomagnetic investigations of Jurassic, Cretaceous and Tertiary sites in the external Betic Cordillera indicate that, while the observed remanence vectors have inclinations which are conformable with the expected inclinations for stable Iberia, declinations deviate significantly. These results indicate that: (1) the Mesozoic limestones of the Penibetic have been rotated clockwise with respect to stable Iberia and, (2) there is a differential rotation between the Cretaceous sites (Dec. = 61-degrees +/- 11-degrees) and the Jurassic sites (Dec. = 38-degrees +/- 8-degrees). The differential rotation of 23-degrees between the late Jurassic and late Cretaceous is consistent with the Cretaceous anticlockwise rotation of the Iberian Peninsula with respect to Eurasia. It follows that during this time period this part of the Betic mobile belt was part of the continental margin of the Iberian Peninsula. A study which was confined to a single unbroken stratigraphic section west of Ronda indicates that most of the anticlockwise rotation (20-degrees) probably occurred between the Cenomanian and the Campanian. The anticlockwise rotation of these rocks must have been followed by a clockwise rotation of at least 60-degrees to account for the observed clockwise declination anomalies.