Long Wavelength Progressive Plateau Uplift in Eastern Anatolia Since 20 Ma: Implications for the Role of Slab Peel‐Back and Break‐Off

Abstract

Stratigraphic evidence is used to interpret that the East Anatolian Plateau with 2 km average elevation today was below sea level ~20 Ma and uplift began in the northern part. The presence of voluminous volcanic rocks/melt production across the plateau—younging to the south—corroborates geophysical interpretations (e.g., high heat flow and lower seismic velocities) that suggest progressive removal of the slab subducting under the Pontides. Here, we conduct numerical experiments that investigate the change in the surface uplift as a response to slab peel‐back and potential break‐off processes under subduction‐accretionary complexes as well as continental lithosphere. Model results show similar types of tectonic behavior and magnitudes of uplift‐subsidence in both oceanic and continental removal processes, and they satisfactorily explain 1.5 km of plateau rise and a ~280 km wide asthenospheric upwelling zone beneath Eastern Anatolia over 18 Myr timescale. Parametric investigation for varying plate strength and convergence velocities show that such model parameters control the amount of surface uplift (1 to 3 km), the width of the asthenospheric upwelling zone, and the potential timing/depth of break‐off of the steepening/peeling slab. Experiments show that slab break‐off develops during the terminal phase, which may correspond to only a few million years ago. Therefore, the long wavelength plateau uplift and magmatism over the Eastern Anatolian‐Lesser Caucasus region since 20 Ma is controlled by progressive slab peel‐back and resulting mantle dynamics. The slab break‐off process (if it happened) has yet an indiscernible role.

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

“…Subduction here occurred between the Jurassic and Late Cretaceous (e.g., Hässig et al., 2017; Parlak et al., 2013), with most evidence pointing to a Late Cretaceous‐Early Paleocene (72–62 Ma) collision (e.g., Kaymakçı et al., 2009; Rolland et al., 2009; Schleiffarth et al., 2018). Some geodynamic studies propose that Bitlis slab break‐off occurred first and the Pontides slab subsequently steepened and peeled back beneath eastern Anatolia following a later collision (e.g., Göğüş & Pysklywec, 2008; Keskin, 2003; Memiş et al., 2020; Şengör et al., 2008). Others suggest Pontides slab break‐off occurred prior to Bitlis slab break‐off, with no peeling of lithosphere beneath Anatolia involved (e.g., Parlak et al., 2013; Schleiffarth et al., 2018; Topuz et al., 2017).…”

“…Debate surrounds the causes of magmatism and uplift in central and eastern Anatolia, and if they have a common geodynamic evolution relating to consequences of terminal‐stage subduction. Some petrological and geodynamic modeling studies favor slab steepening/peel‐back of initially flat subduction and eventual break‐off as the cause, suggesting it is required to explain N‐S discrepancies in volcanic alkalinity (Bartol & Govers, 2014; Keskin, 2003; Şengör et al., 2008) and satisfy the 1–2 km plateau uplift (Göğüş & Pysklywec, 2008; Göğüş & Ueda, 2018; Memiş et al., 2020). Other geochronologic and geodynamic studies favor lithospheric removal/thinning in the form of gravitational instabilities developed during collision (Göğüş, Pysklywec, & Faccenna, 2017; Schleiffarth et al., 2018), advocating it is required to explain the rapid surface uplift and volcanism along plateau edges.…”

“…Several aspects of Neo‐Tethyan slab evolution are debated, one of the most contentious of which concerns the style and relative timing of collision and break‐off of the northern and southern Neo‐Tethyan Oceans. Below the Bitlis‐Zagros suture (Figure 1), the Bitlis slab, which represents the southern branch of the Neo‐Tethys Ocean, is thought to have undergone complete break‐off (e.g., Lei & Zhao, 2007; Memiş et al., 2020; Zor, 2008), though proposed ages span several geological periods, from 40–5 Ma (e.g., Keskin, 2003; Rabayrol et al., 2019; Schleiffarth et al., 2018). The Izmir‐Ankara‐Erzincan suture, between the Anatolide‐Taurides and the Pontides (Figure 1), marks the former location of the northern branch of the Neo‐Tethys Ocean (e.g., Hässig et al., 2017; Okay & Tüysüz, 1999), often termed the Pontides slab.…”

“…The 2 km‐high EAP, resembling the Tibetan Plateau (e.g., Şengör et al., 2003), is covered in 1 km‐thick, dominantly 10 Ma to recent volcanic units (Göğüş, Pysklywec, & Faccenna, 2017; McNab et al., 2018; Reid et al., 2017). However, recent isotopic data show volcanism may have been active since 20 Ma (Memiş et al., 2020; Rabayrol et al., 2019; Schleiffarth et al., 2018). The CAP is thought to have risen by 1 km in the last 10 Ma (e.g., Schildgen et al., 2014), with the southern margin risen by ∼2 km (e.g., Schildgenet al., 2012).…”

“…Petrological studies have suggested a roughly north to south migration and increase in alkalinity of EAVP magmatism (e.g., Keskin, 2003; Keskin et al., 1998), an argument used to support flat subduction/peel‐back, gradual steepening, and eventual break‐off of the Pontides slab during the Miocene. This mechanism has also been modeled to satisfy the long‐wavelength plateau uplift over eastern Anatolia since 20 Ma (Memiş et al., 2020). However, more recent geochronological studies deemed the north to south volcanic migration sporadic (Figure 1a; e.g., Schleiffarth et al., 2018), and consistent with a melt‐generation mechanism of localized lithospheric dripping in response to small‐scale convection (e.g., Rabayrol et al., 2019; Schleiffarth et al., 2018).…”