Paleomagnetic constraints on the early Miocene closure of the southern Neo-Tethys (Van region; East Anatolia): Inferences for the timing of Eurasia-Arabia collision

Oligocene-Miocene convergence of the Eurasian and Arabian plates resulted in (i) the gradual closure of the Neo-Tethys Ocean that formed an open marine connection between the Indian Ocean and the proto-Mediterranean until the early Miocene and (ii) Eurasia-Arabia continental collision. Remnants of the Neo-Tethys basin are found scattered over eastern Anatolia. The Van region of SE Anatolia contains a unique stratigraphic succession (Van Formation) of this ancient marine corridor, showing a gradual transition from deep-marine marls to continental clastics and shallow marine deposits. This formation is considered a key unit for the late stage evolution of the Neo-Tethys Ocean as it contains one of the youngest marine deposits of the southern Neo-Tethys branch in SE Anatolia. Here, we present new magnetostratigraphic and Anisotropy of Magnetic Susceptibility (AMS) data to better constrain the timing of the marine-continental transition and the style of deformation in the Van region. The Van Formation was sampled in similar to 2-m stratigraphic resolution, with similar to 350 paleomagnetic cores drilled in stratigraphic order. These cores were analyzed with thermal and alternating field demagnetization, resulting in a magnetic polarity pattern that could straightforwardly be correlated to the standard Geomagnetic Polarity Time Scale (GPTS). The base of the section has an age of similar to 19.5 Ma, the marine-continental transition is dated at 18.8 Ma, and the top of the succession has an age of similar to 16.8 Ma. The AMS data show a conspicuous change from extensional to contractional patterns, coinciding with the end of open marine environments, at an age of similar to 19 Ma. We hypothesize that the closure of the marine basin and the concomitant change in stress regime in the Van region are related to the onset of Eurasia-Arabia collision and the terminal subduction of the Neo-Tethys oceanic lithosphere.