New paleomagnetic data from Oligocene-upper Miocene sediments in the Rif chain (northern Morocco): Insights on the Neogene tectonic evolution of the Gibraltar arc

Abstract

In this paper, we present new paleomagnetic data from Tertiary sedimentary sequences of the Rif chain. Paleomagnetic results show that the Rif chain underwent different patterns of vertical axis rotations depending on the tectonic location of the sampled sites. Whereas no paleomagnetic rotations have been measured either in the upper Miocene postnappe basins located along the Mediterranean coast or in the upper Miocene Fes-Taza foreland basins, upper Miocene thrust top sequences from the external Rif show a significant amount (20° ± 13° in average) of counterclockwise rotations. The spatial distribution of paleomagnetic rotations shows that tectonic rotations, as observed in other arcs of the Mediterranean region, are confined to the orogenic wedge and do not extend to the foreland domain. Paleomagnetic results from this study contribute to better constrain the age of paleomagnetic rotations in the Rif chain, showing that counterclockwise rotations, previously measured only in Mesozoic units, extended into upper Miocene deposits. These results, together with recent published data from the Betics, suggest that the bending of the Gibraltar Arc was not completely achieved by the late Tortonian-Messinian, enhancing the role of vertical axis rotations in the late Miocene to Recent tectonic evolution of the Gibraltar Arc. Copyright 2008 by the American Geophysical Union.