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

Summary

The Alpine-Himalayan orogen preserves geological remnants of subducted lithosphere from the Paleotethys and Neotethys oceans and intervening microcontinents. This orogenic belt displays distinct segments separated by discontinuities aligned with paleo-transform faults, reflecting laterally varying ocean opening and closure histories. We investigate how upper and lower mantle slab remnants imaged by seismic tomography may correlate with Paleo- and Neotethyan subduction zones, focusing on the Anatolian, Aegean, and Iranian segments. Using plate tectonic reconstructions in a mantle reference frame, we predict slab subduction timing, amount, and location and make a semi-quantitative dimensional comparison with seismic tomographic images beneath the Eastern Mediterranean and Middle East. We identify three major Neotethyan slabs: the Pontides and Egypt slabs detached in the Late Cretaceous and now occupy the upper lower mantle. The Cyprus slab remains mainly in the upper mantle in which it overturns. To account for subducted lithosphere that reconstructions predict, we interpret that the Cyprus slab lies overturned in the lower mantle down to ∼1000 km. We interpret a large lower mantle anomaly volume between 2200-1500 km (the Herodotus anomaly) as representing Paleotethyan lithosphere that subducted between ∼240-180 Ma. Our reconstruction-tomography comparison suggests that current slab positions likely reflect past detachment locations, while geometries indicate paleo-trench absolute motions, including a Late Cretaceous same-dip, double subduction configuration. Slabs associated with Aegean, Anatolian, Iranian, and Tibetan segments define stable mantle provinces with boundaries aligned with transform-related orogenic segmentation, implying minimal paleo-longitudinal mantle flow since the Early Mesozoic. Our findings indicate upper and lower mantle structure primarily results from near-vertical slab sinking after detachment since the Triassic, without evidence for deflection by lateral components of mantle convection.