Biozonation, microfacies analysis and depositional environment of the Cenomanian sediments (Sarvak Formation) in South Zagros Basin (SW Iran)

In this study, the Sarvak Formation in the Kuh-e Zana stratigraphic section has been investigated in terms of Cenomanian biostratigraphy, microfacies analysis, and depositional environment interpretation. The section is located in the Interior Fars zone in the Zagros Basin. The selected section of the Sarvak Formation consists of 211 m of limestone and overlies the Kazhdumi Formation conformably whereas the upper limit of the Sarvak Formation is not obvious. Based on paleontological data three biozones in the study area were established: (1) Nezzazata simplex interval zone (Early Cenomanian), (2) Chrysalidina gradata interval zone (Middle Cenomanian), (3) Cisalveolina fraasi (fallax) & Cisalveolina lehneri—Praetaberina bingistani assemblage zone (Late Cenomanian). Based on petrographic studies, eleven microfacies were identified as follows: MF1: Oligosteginid bioclast wackestone to packstone, MF2: Bioclastic wackestone–packstone, MF3: Bioclastic peloidal wackestone–packstone, MF4: Rudist floatstone, MF5: Rudist rudstone, MF6: Foraminifera intraclastic grainstone, MF7: Benthic foraminifera rudist debris packstone–grainstone, MF8: Bioclastic grainstone–packstone, MF9: Bioclastic benthic foraminiferal wackestone to packstone, MF10: Bioclastic peloidal packstone, MF11: Algal-foraminiferal wackestone–packstone. Microfacies analysis shows that the Sarvak Formation comprises three paleoenvironments as the outer ramp, middle ramp, and inner ramp (shoal and lagoon).