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).

The 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. Plain Language Summary: The Earth's surface is shaped by interactions between tectonics, climate, and erosion. Tectonic activity with ground motion weakens and fractures bedrock, creating debris and physical erosion, particularly in regions experiencing crustal shortening. There is no doubt that tectonics influence climate primarily by growing high mountain ranges and plateaus. Such high topography may create a barrier to atmospheric circulation and alter precipitation that has significant impact on climatic conditions and erosion. A number of regions around the world have shown the link between tectonic and climatic processes, however, we still lack a comprehensive understanding of ongoing deformation/tectonics and climate on the NNW Iranian Plateau and its margin. We used new 10Be concentration data from river sands and integrate these with topographic‐climatic metrics combined with long‐term data to show how this region has evolved over the past 50 Ma. Our findings suggest that millennial‐scale erosion rates have decreased relative to the long term, mainly due to tectonic impact. A key outcome of this study is that the results indicate that the landscape is in a quasi‐equilibrium in the Iranian Plateau and in a transient state in the west Alborz. Key Points: Acceleration of post‐collisional AFT/AHe derived exhumation rates (∼10 to ∼2.8 Ma) under impact of tectonics and base‐level fluctuationsDeceleration of 10Be millennial‐scale erosion rates compared to the long‐termNearly stable Plateau since Pliocene due to tectonic quiescence, evolving margin due to tectonic/climate coupling in Pliocene‐Quaternary [ABSTRACT FROM AUTHOR]