Upper Cretaceous–Palaeocene Foraminiferal Turnover of Interior Fars Zone: Gurpi and Tarbur Formations, Zagros Basin (Southwest of Iran)

Upper Cretaceous deposits (Gurpi and Tarbur formations) are well exposed in southeast of Shiraz city (SW Iran), in the Ghareh section. The Gurpi Formation mainly consists of cream marly pelagic limestone, green shale, and marls, 175 m thick, which covers Cenomanian shallow‐water sediments (Sarvak Formation) unconformably, while the Tarbur Formation is extended 10 m upward to include marly to sandy limestone. The Upper Cretaceous deposits are covered by marl of Sachun Formation (Upper Palaeocene). The Gurpi Formation deposits yielded planktonic foraminifera, while the Tarbur Formation consists of shallow‐water biofacies (benthic foraminifera and rudist debris). The stratigraphic distribution of Gurpi Formation planktonic foraminifera confirms the presence of five biozones in the Ghareh section, which are: Globotruncanita elevata Interval Zone, Globotruncana ventricosa Interval Zone, Radotruncana calcarata Total Range Zone, Globotruncana aegyptiaca Interval Zone, and Gansserina gansseri Total Range Zone. The youngest Omphalocyclus macroporus Taxon Range Zone is identified for the Tarbur Formation. According to described Late Cretaceous biozones, the age of the Gurpi Formation is assigned to the Campanian–Lower Maastrichtian, while the Tarbur Formation age is referred to the upper Maastrichtian. The lowermost part of the Sachun Formation consists of the Upper Palaeocene foraminiferal association, which includes Miscellanea minuta , Daviesina iranica , Globoflarina cf. sphaeroidea , and Rotalia trochidiformis . Therefore, the K/Pg boundary is marked by an obvious unconformable contact in the Ghareh section.