The sedimentary sequence, extending from the Maastrichtian to the lower Eocene and exposed in two sections in the easternmost part of the Izeh Zone (Kuh-e-Sefid and Mish anticlines) in the Zagros Basin, has been subjected to a comprehensive analysis of its Planktic foraminiferal assemblage. This time interval encompasses the upper part of the Gurpi Formation and the lower to middle part of the Pabdeh Formation, spanning from the base to the top. The lithology of the Maastrichtian-early Eocene successions comprises calcareous shales, argillaceous limestones, glauconitic and phosphatic limestones, marlstones, purple shales, and cherty argillaceous limestones. A total of 35 genera and 118 species of Planktic foraminifera have been conclusively identified. The identified biozones include the Contusotruncana contusa Interval Zone and the Abathomphalus mayaroensis Interval Zone, indicating an early to late Maastrichtian age for the upper part of the Gurpi Formation. The lower to middle part of the Pabdeh Formation exhibits distinctive biozones, such as Praemurica uncinata (P2), Igorina albeari (subzone P3b), Igorina-Globanomalina pseudomenardii Interval Zone, Globanomalina pseudomenardii (P4), Morozovella velascoensis (P5), Acarinina sibaiyaensis (E1), Globanomalina pseudomenardii- Pseudohastigerina wilcoxensis Interval Zone, Pseudohastigerina wilcoxensis/Morozovella velascoensis (E2), Morozovella marginodentata (E3), Morozovella velascoensis-Morozovella formosa formosa and/or Morozovella lensiformis Interval Zone (subzone P6a), Morozovella formosa (E4), Morozovella aragonensis/Morozovella subbotinae (E5), Acarinina pentacamerata (E6), Acarinina cuneicamerata (subzone E7a), and Turborotalia frontosa (subzone E7b). The boundary between the Pabdeh and Gurpi Formations in the examined sections is demarcated by an unconformity, characterized by a sedimentary hiatus from the early Danian to the early Selandian within biozones P0 to P3a.

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