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Paleomagnetic evidence for Neogene tectonic rotations in the northern Apennines, Italy

Muttoni, Giovanni; Argnani, Andrea; Kent, Dennis V.; Abrahamsen, Niels; Cibin, Ubaldo

Paleomagnetic analysis was carried out in the northern Apennines on Eocene to Pliocene Epiligurian units. Five Early Miocene and two Middle Miocene sites yielded dual polarity site-mean directions which show signs of clustering after correction for bedding tilt. These likely primary magnetizations, in conjunction with data from the literature, give an overall mean Late Oligocene-Middle Miocene paleomagnetic pole which shows a large and significant counterclockwise rotation of 52° (±â‰ˆ8°) with respect to the Africa reference paleopoles (or a similar amount of rotation with respect to the coeval Europe reference paleopole). However, this paleopole falls close to the roughly coeval paleopole for Corsica-Sardinia, which is here calculated by averaging data from the literature. Three additional Early Miocene sites from an area west of Parma affected by Pliocene tectonics yielded site-mean directions which pass the fold test and are rotated counterclockwise by a lesser amount than the rest of the Miocene sites. Most of the remaining sites bear paleomagnetic directions acquired after tilting during a recent phase of remagnetization. We suggest that the large-scale rotation observed in the northern Apennines was associated with the motion of the Corsica-Sardinia block within the general context of the Africa-Europe relative motions. A compilation of published data from the central Apennines also shows a differential rotation of the northern relative to the southern Umbria belt which occurred after the motion of Corsica-Sardinia and may have been due to pivoting of the northern Umbria belt against a deep-seated lineament during the non-rotational opening of the Tyrrhenian Sea.

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Earth and Planetary Science Letters

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Lamont-Doherty Earth Observatory
Biology and Paleo Environment
Published Here
December 6, 2011