Revised lithostratigraphy and biostratigraphy of the Tarbur type section, Kuh-e-Gadvan, northeast of Shiraz, Fars area, Iran

The type section of the Upper Cretaceous (Maastrichtian) Tarbur Formation (692 m thick) was defined by James and Wynd (1965, AAPG Bulletin, v., 49, p. 2218) in the paper: Stratigraphic nomenclature of Iranian oil consortium agreement area. We have revised the definition based on field observation and thin section studies. Above the Tarbur Formation, we did not recognize the previously defined Sachun Formation, consisting of red and green marls. Instead we found the upper boundary of the Tarbur Formation to be bounded by a fault, which renders it indistinguishable from the Sachun Formation. Accordingly we propose a new type section for the Tarbur Formation in Kuh-e-Chel Cheshmeh, Kherameh, southeast of Shiraz city. Our study also recognized that marls with pelagic facies that yielded abundant planktonic foraminifera (Gansserina gansseri- Contusotruncana contusa subzone) are Mid-Maastrichtian in age. These marls may occur as a tongue followed by alternating marls and limestones, and finally by a thick-to-massive rudist reefal limestone (34 m thick).