Paleo- and Neo-Tethyan subducted slabs below the Eastern Mediterranean region

Douwe J.J. van Hinsbergen , Douwe van der Meer, Wim Spakman 

The late Paleozoic to recent Alpine-Himalayan orogen contains the geological remnants of subducted lithosphere of the Paleotethys and Neotethys oceans and of microcontinents within these. This orogenic belt is segmented by abrupt along-strike changes that according to plate reconstructions coincide with paleo-transform faults across which oceanic opening and subduction histories changed. Here, we test whether seismic tomography identifying these segments in the mantle below the Tethyan realm in the form of slab remnants that may be correlated to Paleo- and Neotethyan subduction zones. We focus on the Anatolian segment, and the neighboring Aegean and Iranian segments, using a recent, detailed plate tectonic reconstructions placed in a mantle reference frame, to predict where and when slabs would have subducted. We compare these predictions with seismic tomographic images of the mantle below the Eastern Mediterranean. We use previously interpreted slabs of the Aegean and Iranian region to identify anomalies of the Anatolian segment and identify a sub-horizontal slab between 2200 and 1500 km depth as the remnant of the Paleotethys oceanic lithosphere that subducted between ~240 and 180 Ma. Subsequent Neotethys subduction formed three major slabs, two of which (Pontides and Egypt slabs) broke off in the late Cretaceous and are present in the upper lower mantle. The final one (Cyprus slab) is present mostly in the upper mantle and overturned in the top of the lower mantle and is still subducting, or may be detaching, today. The present positions of these slabs likely reflect their past slab detachment locations, and their shapes reflect absolute motions (advancing, stationary, or retreating) of their associated paleo-trenches through time. We identify that slabs associated with Aegean, Anatolian, Iranian, and previously identified Tibetan segments make mantle provinces whose transitions still closely align the transform-related orogenic segmentation boundaries, implying minimal paleo-longitudinal mantle flow in the mantle reference frame since the Early Mesozoic. This suggests that upper and lower mantle structure is well explained by near-vertical sinking of slabs after their detachment since the Triassic without significant disturbance by bottom-up driven, or lateral, mantle convective flow.