Pre-Miocene Paleomagnetic Data from the Calabrian Block Document a 160° Post-Late Jurassic CCW Rotation

The Calabrian block, along with Alboran, Kabylies and Peloritani, form isolated and enigmatic igneous/metamorphic terranes (AlKaPeCa) stacked over the Meso-Cenozoic sedimentary successions of the Apennines and Maghrebides. The long-lasting debate on the origin and evolution of such crustal terranes include different paleogeographic interpretations. Some authors considered them as: i) remnants of a micro-continent lying between Eurasia and Africa; ii) fragments of the Hercynian margin of Europe separated from Africa during Early Jurassic Alpine Tethys spreading, later detached from Corsica-Sardinia and/or Catalan-Provençal margin, and then stacked over Apennine-Maghrebian sediments during Neogene roll-back episodes; iii) portion of the Africa-Adria paleomargin deformed and involved into the orogenic pile.

Paleomagnetic data are crucial to properly reconstruct the drift of the AlKaPeCa blocks and their lasting geological history, however no paleomagnetic data could be obviously obtained from the Hercynian crystalline rocks of the AlKaPeCa. Besides the well-defined ∼20° clockwise (CW) rotation, constrained between 1 and 2 Ma and related to changes occurring in the roll-back system and spreading episodes in the Tyrrhenian Sea, the tectonic behavior of the Calabrian block during the Early Jurassic rifting episodes, the Early-mid Cretaceous transcurrent tectonics, the Late Cretaceous-early Cenozoic Africa-Europe collision, and Eocene-Miocene counterclockwise (CCW) 90° rotation of the Corsica -Sardinia block, to which Calabria was likely solidly attached, remains completely speculative.

We report on the paleomagnetism of upper Triassic-lower Miocene sedimentary rocks from the Longobucco succession that is transgressive over the crystalline Sila Massif (NE Calabria). Well-defined remanent magnetization directions carried by hematite were isolated in 10 sites (122 samples) in Jurassic rocks. Nine Toarcian and one Tithonian Ammonitico Rosso sites yielded a dual polarity “A” magnetization component whit a direction over 40° from the geocentric axial dipole (GAD) field direction, that supports a positive fold test. Five sites yielded a “B” normal polarity component NE (<40°) of the GAD direction characterized by a negative fold test. We interpret the B component as a Miocene magnetic overprint later clockwise rotated by ∼20° during the Pleistocene (1–2 Ma) rotation of Calabria. When corrected for such rotation, the A component defines a ∼160° CCW rotation of the Calabrian block with respect to Europe. Of these, ∼90° likely occurred along with Corsica-Sardinia block during its Eocene-Miocene rotation from the Provençal margin. Thus, the Calabrian block underwent an additional Cretaceous-Eocene 70° CCW rotation that we relate to Early-mid Cretaceous >500 km left-lateral transcurrent motion between Africa and Europe.