Paleomagnetic data from Late Paleozoic dykes of Sardinia: Evidence for block rotations and implications for the intra-Pangea megashear system



Paleomagnetic studies of dyke swarms from the Variscan belt of Europe can be used to reconstruct internal postorogenic rotations within the fold belt. Here we present paleomagnetic data from 13 late Variscan dykes from Sardinia ranging in age from 298 ± 5 to 270 ± 10 Ma. The dykes can be grouped on the basis of their different directions in strike in a northern, a central-eastern and a south-eastern province. Paleomagnetic component directions have been obtained using thermal and alternating field demagnetization techniques, which give reproducible results. The paleomagnetic mean directions differ significantly between northern Sardinia and south-eastern and central-eastern Sardinia, the latter two regions yielding statistically similar paleomagnetic mean directions. These results indicate that Sardinia fragmented into two, arguably three, crustal blocks after emplacement of the dykes, which experienced differential relative rotations, as is also indicated by the differences in overall strike directions. The determination of timing, sense, and magnitude of these rotations has major implications for the reconstruction of the geodynamic evolution of the region in post-Carboniferous times. We argue that the observed block rotations occurred during the Permian as the result of post-Variscan intra-Pangea mobility possibly related to the transformation of an Early Permian Pangea B to a Late Permian Pangea A.