The intermontane Tarom Basin of NW Iran (Arabia-Eurasia collision zone) is located at the transition between the Iranian Plateau (IP) to the SW and the Alborz Mountains to the NE. This basin was filled by Late Cenozoic synorogenic red beds that retain first-order information on the erosional history of adjacent topography, the vertical growth of the plateau margin and its lateral (orogen perpendicular) expansion. Here, we perform a multidisciplinary study including magnetostratigraphy, sedimentology, geochronology and sandstone petrography on these red beds. Our data show that widespread Eocene arc volcanism in NW Iran terminated at ~ 38-36 Ma, while intrabasinal synorogenic sedimentation occurred between ~ 16.5 and < 7.6 Ma, implying that the red beds are stratigraphically equivalent to the Upper Red Formation. After 7.6 Ma, the basin experienced intrabasinal deformation, uplift and erosion in association with the establishment of external drainage. Fluvial connectivity with the Caspian Sea, however, was interrupted by at least four episodes of basin aggradation. During endorheic conditions the basin fill did not reach the elevation of the plateau interior and hence the Tarom Basin was never integrated into the plateau realm. Furthermore, our provenance data indicate that the northern margin of the basin experienced a greater magnitude of deformation and exhumation than the southern one (IP margin). This agrees with recent Moho depth estimates, suggesting that crustal shortening and thickening cannot be responsible for the vertical growth of the northern margin of the IP, and hence surface uplift must have been driven by deep-seated processes.

Shafaii Moghadam et al. (2020) contribute important new data on Late Cretaceous-Tertiary subduction- related magmatism in Iran, but their plate convergence model, wherein Neotethyan subduction begins in mid-Cretaceous time (c. 100 Ma), overlooks well established facts relating to the tectonic history of Neotethys, in regard to global plate reconstructions, paleolatitude data, the regional stratigraphy, geochronology and geochemistry, and metamorphic history. Based on their model, Neotethys subduction beneath Eurasia began at ~100 Ma, meaning that the Neotethys was spreading and bounded by opposing passive margins during Jurassic and Early Cretaceous time, for ~100 Ma prior to their proposed onset of Neotethyan convergence. Consequently, their subduction model contradicts (1) the Indian Ocean spreading history derived from magnetic anomalies; (2) continental paleolatitude data from paleomagnetism; (3) sedimentary and igneous evolution of the Mesozoic continental margins in Arabia and southern Asia, (4) the age and geochemistry of Jurassic igneous rocks in southernmost Eurasia; and (5) the preservation of Early to Middle Jurassic eclogite metamorphism and exhumation on the northern side of the Arabia-Eurasia suture. Reconciliation of each of these omissions and contradictions of their model would be welcome, and perhaps an advisory that readers may wish to evaluate their concept of Cretaceous subduction initiation with due circumspection.