Remagnetization during Rotation: The Variscan Orocline(s?) in Iberia

Abstract

The Variscan orogeny in Iberia consists of at least one orocline in a c-shape but recent work suggests that a second orocline is formed simultaneously, creating an s-shape. In order to investigate the geometry and kinematics of the southern orocline we perform a paleomagnetic study on remagnetized Cambrian limestones located in the middle of the s-shape with the Cantabrian Orocline in the north and the Central Iberian Orocline to the south. The paleomagnetic study shows 65 degree spreading with east and southeast magnetic directions. The rocks show magnetic isotropy and fold tests are negative. Thermomagnetic analysis shows pyrrhotite as main carrier with inclusions of magnetite, which is more closely investigated by using hysteresis loops, IRM acquisition, and subsequent unmixing in three end-members. The total interpretation is a 65 degree counterclockwise rotation with rapid local remagnetizations during the Later Carboniferous to Early Permian. This interpretation does only fit with the Cantabrian Orocline in the north, which disproves simultaneous formation of both oroclines. The Central Iberian Orocline, if present, must be formed before the initiation of the Cantabrian Orocline.