Biostratigraphic Revision of Middle-Cretaceous Biostratigraphy Succession in South Zagros Basin

Abstract

Cenomanian succession (Sarvak Formation) is well distributed along Zagros area particularly in the south portion of the Zagros (Fars area). This study attempts to determine the precise biostratigraphic biozones of four stratigraphic sections selected from the Cenomanian strata south Zagros basin, including the sections of Nour Abad, Samghan, Doroodzan, and Arsanjan. The vertical distribution of the index foraminifers confirms a faunal assemblage of benthic and planktic foraminifers in the mentioned stratigraphic sections. The received Biostratigraphic data of this work reveals well developed benthic foraminifers and well distributed Cenomanian planktons in the uppermost lithostratigraphic part of the studied Sarvak exposures. However, the established biozones of the Sarvak Formation represent the Cenomanian age, which is similar to many recognized Cenomanian biozones in the Tethyan realm, whereas the foraminiferal biostratigraphy of the Arsenjan stratigraphic column is assigned to the Late Albian to Early Cenomanian age. Since benthic foraminifers are well expanded in studied section of Sarvak Formation, the presence of pelagic biofacies is a proof of transgression in some studied sections. However, the established biozones support that geologic setting is the most factor which controls vertical distribution of foraminifers and other microfossils during the deposition of Sarvak Formation. The received biostratigraphic data of the Sarvak Formation determines subdivision of Cenomanian age in the South Zagros basin clearly.