Constraints on palaeodrainage evolution induced by uplift and exhumation on the southern flank of the Zagros–Iranian Plateau

Foreland sedimentary rocks from the northern Fars region of Iran contain a record of deformation associated with the Cenozoic collision between Arabia and Eurasia that resulted in formation of the Zagros orogen. The timing of the deformation associated with this event is poorly known. To address this we conducted a study of Miocene foreland sedimentary rocks (19.7–14.8 Ma) of the Chahar–Makan syncline using clast composition, clay mineralogy and low-temperature fission-track dating. The results showed that most of the sedimentary rocks were sourced from ophiolitic rocks. Detrital apatite fission-track (AFT) age signatures of Miocene sedimentary rocks record exhumation in the hanging wall of the Main Zagros Thrust and confirm that the change from underthrusting of the stretched Arabian margin to widespread crustal thickening and deformation in the Zagros region is no younger than 19.7 Ma. A transition from Late Oligocene to Mesozoic–Eocene AFT detrital age signatures between 19.7–16.6 Ma and 16.6–13.8 Ma is interpreted to reflect a possible rearrangement of palaeodrainage distribution that resulted from folding and expansion–uplift of the Zagros–Iranian Plateau region.