Tectonics, Base‐Level Fluctuations, and Climate Impact on the Eocene to Present‐Day Erosional Pattern of the Arabia‐Eurasia Collision Zone (NNW Iranian Plateau and West Alborz Mountains)

AbstractThe NNW Iranian Plateau and west Alborz within the Arabia‐Eurasia collision zone are characterized by three main tectono‐stratigraphic zones, crosscut by the Qezel‐Owzan River (QOR) Basin. The interplay between present‐day deformation and climate, which control the landscape evolution of the region, is still poorly constrained. We addressed this gap by measuring millennial‐scale erosion rates from 10Be‐concentration in the QOR sands along with topographic/climatic metrics analyses. Results reveal low erosion rates in the Plateau and relatively high in the west Alborz. The regional consistency of topographic parameters with geomorphology suggests that they control sediment fluxes in the Plateau, while the surface uplift, active thrust‐faulting, and shallow crustal seismicity in the west Alborz are the main controlling factors. Climate has a secondary role on erosion rates. Furthermore, we calculated exhumation rates from published thermochronometric AFT/AHe ages to determine their relationship with 10Be short‐term data. Results imply that the exhumation rates increased slightly in the Plateau and west Alborz from ∼26 to ∼10 Ma, simultaneous with hard collision processes between the Arabia‐Eurasia. This trend accelerated from ∼10 to ∼2.8 Ma due to the isolation of the Caspian Sea and extreme base‐level fall. From ∼2.8 to ∼2 Ma, base‐level rise occurred under climate influence, and erosion rates decreased. Millennial‐scale data show the erosion rate decreased from ∼2 Ma to the Present‐day, which is attributed to the change in deformation style and fault kinematics from fold/thrusting to mainly strike‐slip faulting. The significantly lower erosion rates in the Plateau compared to west Alborz suggest a relatively stable plateau surface.