Dynamics of Plateau Growth: Geodynamic Modeling of the East AnatolianPlateau Uplift Through Double Subduction Processes

The Turkish–Iranian Plateau was formed by the collision between the Arabian and
Eurasian plates, commencing along the Bitlis-Zagros suture in the Late Eocene (~30-
35 Ma). This region, commonly partitioned into the East Anatolian Plateau and the
Iranian Plateau, is associated with significant differences in terms of lithospheric
structure despite an overall average of ~2 km. The geodynamic evolution of East
Anatolia is represented by a double subduction system, where the two branches of
Neo-Tethys were subducting beneath Eurasia, constantly accumulating accretionary
material that forms the bulk of the plateau today (i.e., East Anatolian Accretionary
Complex). Seismic evidence demonstrates that the region has unusually thin MOHO
(~35 km around Lake Van region) while the whole area is formed mostly by oceanic
(accretionary) material and is underlain by no or very thin mantle lithosphere. The
uplift of East Anatolia is attributed to slab break-off and slab peelback (delamination),
combined with crustal shortening. However, the intricate plate dynamics arising from
such a double subduction system, controlling plateau formation remains unclear.
Here, we conducted 2D numerical experiments and comparative model sets indicate
that, in a double subduction system like Eastern Anatolia, the mechanisms of slab
break-off and peelback heavily depend on the rheology of the subducting plates and
the coupling between the overlying and subducting plate along the trenches. In cases
of strong coupling between subducting and overlying plates, we observed an
amalgamation of the two subducting plates as they converge, potentially resulting in
a break-off as a single blob, depending on plate rheology. Conversely, in models with
weaker coupling along the trenches, peelback along the northern slab creates a thin
lithosphere along the accretionary prism, such as in the evolution of the Eastern
Anatolian Plateau. Our results highlight the important interaction between the
subduction systems where rheological constraints of the lithosphere, among other
model parameters, exert a first-order control for plateau formation.