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

Abstract

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 ~2-m stratigraphic resolution, with ~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 ~19.5 Ma, the marine-continental transition is dated at 18.8 Ma, and the top of the succession has an age of ~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 ~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.