Paleomagnetic results from Mallorca (Balearic Islands, Spain)

Abstract

We studied the paleomagnetism of Jurassic limestones on the island of Mallorca (Balearic Archipelago, western Mediterranean) to determine if two thrust sheets exhibiting different structural patterns were rotated relative to one another. After correction for tilt the circle of confidence for the mean paleomagnetic direction from sites in areas associated with frontal ramps overlaps with the confidence circle of the mean for those sites associated with oblique‐lateral ramps. This indicates that there has been no differential rotation in spite of the fact that the fold axes in these areas trend almost perpendicular to one another. Although the age of magnetization is prefolding (i.e., before Oligo‐Miocene), it is not certain that the paleomagnetic directions reflect Jurassic magnetization since they may have been acquired during a period of emersion in the Upper Cretaceous or Paleocene. The resulting mean direction for nine sites from both thrust sheets (declination = 41°, inclination = 48°, α95 = 7°) implies significant clockwise rotation of the whole island, or at least of the Mesozoic cover, since acquisition of magnetization. If part of this rotation occurred, as we believe, in the Neogene, then structural data from pre‐Miocene rocks must be corrected before being used for regional tectonic interpretation. The mechanism to produce 40° of clockwise rotation since the Oligo‐Miocene could be combined regional extension, Alpine compression, and block rotation.