Subduction termination through progressive slab deformation across Eastern Mediterranean subduction zones from updated P-wave tomography beneath Anatolia


Portner, Daniel Evan
Delph, Jonathan R.
Biryol, C. Berk
Beck, Susan L.
Zandt, George; Özacar, A. Arda; Sandvol, Eric; Türkelli, Niyazi

Using finite-frequency teleseismic P-wave tomography, we developed a new three-dimensional (3-D) velocity model of the mantle beneath Anatolia down to 900 km depth that reveals the structure and behavior of the subducting African lithosphere beneath three convergent domains of Anatolia: the Aegean, Cyprean, and Bitlis-Zagros domains. The Aegean slab has a relatively simple structure and extends into the lower mantle; the Cyprean slab has a more complex structure, with a western section that extends to the lower mantle with a consistent dip and an eastern section that is broken up into several pieces; and the Bitlis slab appears severely deformed, with only fragments visible in the mantle transition zone and uppermost lower mantle. In addition to the subducting slabs, high-amplitude slow velocity anomalies are imaged in the shallow mantle beneath recently active volcanic centers, and a prominent fast velocity anomaly dominates the shallow mantle beneath northern Anatolia and the southern Black Sea. As a whole, our model confirms the presence of well-established slow and fast velocity anomalies in the upper mantle beneath Anatolia and motivates two major findings about Eastern Mediterranean subduction: (1) Each of the slabs penetrates into the lower mantle, making the Eastern Mediterranean unique within the Mediterranean system, and (2) the distinct character of each slab segment represents different stages of subduction termination through progressive slab deformation. Our findings on the destructive processes of subduction termination and slab detachment have significant implications for understanding of the postdetachment behavior of subducted lithosphere.

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Figure 8.
Diagrammatic representation of the interpreted slab geometry for each convergent domain. To create the isosurface, a synthetic velocity structure imitating our interpretation of the slab structure was created, and a synthetic recovery test was performed. The isosurface itself is an isovelocity contour of the output model of the synthetic test. As such, the surface is not derived from data and is not a quantitative representation of the tomography model, but is instead our interpretation. Red triangles indicate volcanoes active in the Holocene. OL—oceanic lithosphere; CL—continental lithosphere; STEP—subduction-transform edge propagator system.

Publication Listing

Geosphere (2018) 14 (3): 907-925.