Seismic Tomographic Imaging of the Eastern Mediterranean Mantle: Implications for Terminal‐Stage Subduction, the Uplift of Anatolia, and the Development of the North Anatolian Fault

Abstract:

By studying the mantle below the the Eastern Mediterranean, one can study a unique east-west transition from active subduction of Earth's oldest oceanic lithosphere to continental collision. Hypotheses concerning asthenospheric- and subduction-related processes have been invoked to explain the region's ∼2km uplift and Miocene volcanism, but their relative significance is debated. To address these issues, in Kounoudis et al., (2020) we present new P- and S-wave mantle seismic tomographic models that reveal fast anomalies associated with an intact Aegean slab in the west, progressing to a fragmented, partially continental, Cyprean slab below central Anatolia. Our models illuminate a gap between the Aegean and Cyprean slabs, and a horizontal tear in the Cyprean slab below the Central Anatolian Volcanic Province. Below eastern Anatolia, the detached 'Bitlis' slab is a fast wave-speed anomaly at ∼500km depth. Assuming slab sinking rates resemble Arabia-Anatolia convergence rates, the Bitlis slab's location suggests an Oligocene (∼26Ma) break-off. Results further reveal a strong velocity contrast across the North Anatolian Fault, likely resulting from a 40−60km decrease in plate thickness from the Precambrian lithosphere north of the fault to a thinned Anatolian lithosphere in the south. Slow shallow-mantle velocities below active volcanoes in eastern Anatolia, and ratios of P- to S-wave relative travel-times, indicate a thin lithosphere and melt contributions. Positive central and eastern Anatolian residual topography requires additional support from hot/buoyant uppermost mantle to maintain the observed 1−2km elevation, in addition to an almost absent lithospheric mantle. Small-scale fast velocity structures in the shallow mantle above the Bitlis slab may therefore be 'drips' of Anatolian lithospheric mantle.

Kounoudis, R., Bastow, I. D., Ogden, C. S., Goes, S., Jenkins, J., Grant, B., & Braham, C. (2020). Seismic tomographic imaging of the Eastern Mediterranean mantle: Implications for terminal‐stage subduction, the uplift of Anatolia, and the development of the North Anatolian Fault. Geochemistry, Geophysics, Geosystems, 21, e2020GC009009. https://doi.org/10.1029/2020GC009009.