ORIGIN OF THE WESTERN SUBBETIC ARC (SOUTH SPAIN) - PALEOMAGNETIC AND STRUCTURAL EVIDENCE

An integrated structural and palaeomagnetic study in Late Cretaceous-E ocene rocks of the western Subbetic are in the Betic Cordillera of sou thern Spain shows that the change in fold trend around the are is sign ificantly greater than the variation in primary magnetic declination. This suggests that the arcuate geometry is not primarily a consequence of differential rotation. The area has experienced a regional clockwi se rotation of at least 40 degrees, which was most probably imposed du ring oblique WNW-directed convergence along the southern Iberian margi n in early Miocene time, before the arcuate structure was formed. Kine matic indicators associated with the arcuate folds and thrust traces a re for the most part consistently WNW-directed, suggesting that the ar e is not primarily a result of variations in the direction of tectonic transport. The arcuate structure was probably initiated without signi ficant rotation by the WNW-directed indentation of the curved western end of the Alboran domain into the Iberian margin, and was then tighte ned, involving up to about 35 degrees of further rotation in different segments of the are. Finally, one sector in the are was rotated antic lockwise by about 40 degrees with respect to the rest of the region, r eorientating the magnetic declinations, the fold trends, and the kinem atic indicators. This rotation was associated with local sinistral she ar.