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.

伊朗北部法尔斯地区的前陆沉积岩记录了与阿拉伯板块与欧亚板块新生代碰撞相关的变形，这一碰撞导致了扎格罗斯造山带的形成。与该事件相关的变形时间尚不明确。为了解决这一问题，我们通过对查哈尔-马坎向斜中的中新世前陆沉积岩（19.7-14.8百万年）进行了研究，采用碎屑成分、粘土矿物学和低温裂变径迹定年方法。研究结果表明，大部分沉积岩源于洋壳岩石。中新世沉积岩的碎屑磷灰石裂变径迹（AFT）年龄特征记录了主扎格罗斯逆冲断层上盘的剥露过程，并证实从拉张的阿拉伯边缘的下滑转变为扎格罗斯地区的广泛地壳增厚和变形的过程不晚于19.7百万年。在19.7-16.6百万年和16.6-13.8百万年之间，从晚渐新世到中生代-古新世的AFT碎屑年龄特征的转变，被解释为可能是由于扎格罗斯-伊朗高原地区的褶皱和抬升扩张导致的古水系分布的可能重新排列。