Structure of the crust and African slab beneath the central Anatolian plateau from receiver functions: New insights on isostatic compensation and slab dynamics

Abstract

The central Anatolian plateau in Turkey is a region with a long history of subduction, continental collision, accretion of continental fragments, and slab tearing and/or breakoff and tectonic escape. Central Anatolia is currently characterized as a nascent plateau with widespread Neogene volcanism and predominantly transtensional deformation. To elucidate the present-day crustal and upper mantle structure of this region, teleseismic receiver functions were calculated from 500 seismic events recorded on 92 temporary and permanent broadband seismic stations. Overall, we see a good correlation between crustal thickness and elevation throughout central Anatolia, indicating that the crust may be well compensated throughout the region. We observe the thickest crust beneath the Taurus Mountains (>40 km); it thins rapidly to the south in the Adana Basin and Arabian plate and to the northwest across the Inner Tauride suture beneath the Tuz Gölü Basin and Kırşehir block. Within the Central Anatolian Volcanic Province, we observe several low seismic velocity layers ranging from 15 to 25 km depth that spatially correlate with the Neogene volcanism in the region, and may represent crustal magma reservoirs. Beneath the central Taurus Mountains, we observe a positive amplitude, subhorizontal receiver function arrival below the Anatolian continental Moho at ~50-80 km that we interpret as the gently dipping Moho of the subducting African lithosphere abruptly ending near the northernmost extent of the central Taurus Mountains. We suggest that the uplift of the central Taurus Mountains (~2 km since 8 Ma), which are capped by flat-lying carbonates of late Miocene marine units, can be explained by an isostatic uplift during the late Miocene-Pliocene followed by slab breakoff and subsequent rebound coeval with the onset of faster uplift rates during the late Pliocene-early Pleistocene. The Moho signature of the subducting African lithosphere terminates near the southernmost extent of the Central Anatolian Volcanic Province, where geochemical signatures in the Quaternary volcanics indicate that asthenospheric material is rising to shallow mantle depths.

Sedimentation and viscosity controls on forearc highs

“…The latter mechanism is consistent with the thick Anatolian crust and lithosphere and the presence of the Cyprus slab under the modern Central Taurus Mountains (e.g., Bakırcı et al, 2012;Abgarmi et al, 2017;Delph et al, 2017) and the coupled, short-wavelength vertical motions reported for South Turkey and its offshore during plateau margin growth (Walsh-Kennedy et al, 2014;Fernández-Blanco et al, 2019).…”

“…South Turkey surface uplift and growth of the modern Central Taurus Mountains at ~8 Ma and later times (e.g., Cosentino et al, 2012;Meijers et al, 2018) Thermo-viscous forearc high evolution in relation to mechanical accretion is consistent with geologic observations along the margin. For example, the presence of Cyprus slab, as imaged by topography (e.g., Bakırcı et al, 2012;Abgarmi et al, 2017), is compatible with the location of the area of maximum crustal thicknesses and uplift (Fig. 3), hence solving the discrepancy inherent to slab break-off models (e.g., Schildgen et al, 2014).…”

“…We integrated tectono-sedimentary and interpreted geophysical data from on-and offshore studies in a crustal transect running from the Cyprus trench to Central Turkey ( (Robertson, 1998;Stephenson et al, 2004;Calon et al, 2005aCalon et al, , 2005bÇıner et al, 2008;McCay, 2010;Fernández-Blanco et al, 2013) with the interpretation of several geophysical studies (Ates et al, 1999;Mart & Ryan, 2002;Ergün et al, 2005;Koulakov & Sobolev, 2006;Özeren & Holt, 2010;Mutlu & Karabulut, 2011;Abgarmi et al, 2017;Delph et al, 2017), as detailed in Fernández-Blanco (2014). CVP = Central Volcanic Province.…”

Geodynamics of Anatolia: Lithosphere Thermal Structure and Thickness

“…We favor a model where lithosphere thinning is possibly related to a proposed SE dipping paleosubduction beneath the southern Kirsehir Massif and the Taurides (Figure ). The presence of the associated cold slab in the upper mantle seems to be imaged by regional tomography models (Bijwaard & Spakman, ; Piromallo & Morelli, ) (Figures a and b), and its possible presence is neither supported nor rejected by a recent RF study (Abgarmi et al, ). The proposed paleosubduction may (at the SW part) interact with the, still speculative, Cyprus subduction, therefore complicating the geodynamic evolution of southern Turkey and possibly channeling mantle melting associated with the Cyprus subduction toward the Antalya block and along the East Anatolian fault (Figure d).…”

“…Anatolia has been covered by a large number of regional seismic tomography models (Biryol et al, ; Govers & Fichtner, ; Lei & Zhao, ; Maggi & Priestley, ; Portner et al, ; Salaun et al, ; Zor, ) and by some seismic RF studies (Abgarmi et al, ). Based on S ‐RF, the lithosphere thickness increases eastward from ~80 km in western Turkey to ~100 km beneath the East Anatolian Plateau (Kind et al, ), in overall agreement with our results that also show a general trend in lithosphere thickening eastward.…”