Paleomagnetic contribution to resolving the tectonic evolution of the Drina-Ivanjica Unit, Internal Dinarides.

The Adria-derived Drina-Ivanjica Unit of the Internal Dinarides represents a composite basement-cover thrust sheet passively carrying obducted Jurassic ophiolites and post-obduction Upper Cretaceous sedimentary rocks, penetrated by post-orogenic Miocene igneous rocks. This study presents the first paleomagnetic results from the Drina-Ivanjica Unit obtained at a total of 34 geographically distributed localities, representing Triassic-Jurassic carbonates, Upper Cretaceous carbonate and flysch successions, as well as Miocene igneous rocks. Paleomagnetic directions for the igneous rocks and the Upper Cretaceous flysch, which had clearly remagnetized during Miocene magmatism, point to a 30° clockwise (CW) rotation, which must have taken place after 20 Ma. This angle perfectly agrees with the earlier-published value for both the Western and Eastern Vardar zones (including the Jadar-Kopaonik thrust sheet, the Sava Zone, and the Cretaceous overstepping sequence of the Eastern Vardar ophiolitic unit), suggesting a coordinated rotation between them and the Drina-Ivanjica Unit. Results of the present study set a younger age constraint (20 Ma) for the commencement of the coordinated CW rotation instead of the previously suggested 23 Ma. The rotation may have connected to the extension induced by the slab rollback of the Carpathians, which was also responsible for the opening of the Pannonian Basin. The paleomagnetic directions for the Cenomanian-Turonian carbonates, which are situated far from the magmatic bodies, are interpreted in terms of a minor counter-clockwise (CCW) rotation taking place before the Miocene CW rotation. The Triassic-Jurassic carbonates of the Drina-Ivanjica Unit have post-tilting magnetizations, which were likely induced by the thermal effect of the obducted ophiolites. The overall mean paleomagnetic direction suggests a rotation of about 50° CCW between 150-20 Ma, which is in line with the well-documented post-150 Ma CCW rotation of the Adriatic microplate. [ABSTRACT FROM AUTHOR]