Geodynamics of East Anatolia-Caucasus Domain: Inferences From 3D Thermo-Mechanical Models, Residual Topography, and Admittance Function Analyses

Abstract

We investigate anomalous topography in the Anatolia-Caucasus domain of the Arabian-Eurasian plate convergence zone. To achieve this aim, we use three-dimensional (3D) geodynamic modeling in addition to analyses of the non-isostatic components of surface topography based on residual topography and free-air gravity admittance functions. The numerical experiments are based on two different temperature models obtained from P-wave tomography data that are sensitive respectively to large and small-scale variations of upper mantle structures. Our results suggest a long-wavelength convective support of topography, which is in general agreement with the uncompensated pattern of residual topography and free-air admittance values, as well as previous modeling studies. At shorter wavelengths, we provide new constraints on the regional dynamic processes related to 3D variations of the upper mantle flow vectors and associated surface deflections. Positive dynamic topography is found over the East Anatolian Plateau (∼400 m to ∼1.2 km) that is consistent with inferred lithospheric thinning processes pertinent to the tectonic evolution of the Tethyan orogenic system. We further show dynamic topography in the plateau (≥500 m) that may account for extensional tectonics in the Lake Van region interpreted from local kinematic and geophysical studies. In conjunction with the observations, negative anomaly patterns are estimated in the western part of the Black Sea (∼−2 km), the eastern Pontides arc (∼−200 m), and the northeast Arabian Plate (∼−1 to −2.3 km). Our model results also suggest a link between large-scale mantle flow and SW-NE-directed general pattern of the SKS-based anisotropy beneath the region. © 2021. American Geophysical Union.