The alveolinids were once highly widespread in the Cenomanian of the Tethys Basin. Even though evolutionary studies have, thus far, been conducted using material from many countries e.g. Spain, Oman, and the UAE, the Zagros region in SW Iran has not been studied yet. Two sections of the Sarvak Formation in the Pyun and Kuh‐e‐Zana areas were investigated. Five type levels can be identified in the Pyun section. The evolutionary trend begins with praealveolinids followed by ovalveolinids in the Early Cenomanian. Cisalveolinids firstly appear in the Late Cenomanian strata and then Multispirina is derived. Then Simplalveolina simplex appears, which is derived from Multispirina iranensis. At the Kuh‐e Zana section, the evolutionary trend was observed in three levels. There is no ideal evolutionary trend because Multispirina and Simplalveolina are absent in this section. The identified trends are similar to those of the Iberian Ranges in Spain.

The Sarvak Formation is a carbonate sequence of Late Albian-Early Turonian age in Zagros Basin in Iran. In this investigation, the Sarvak Formation at the Pyun Anticline section (Izeh Zone) has been studied. It consists of 797 m thick limestone which overlies the Kazhdumi Formation conformably and underlies the Gurpi Formation unconformably at the Pyun Anticline. A very rich fossil association (85 genera and 132 species) characterizes the Pyun section. Based on the stratigraphic distribution of diagnosed foraminifera, five biozones are established: 1, Muricohedbergella-Globigerinelloides sp. assemblage zone (Late Albian); 2, Praealveolina iberica-Chrysalidina gradata interval zone (Early Cenomanian); 3, Chrysalidina gradata-Cisalveolina fraasi (fallax) and C. lehneri interval zone (Middle Cenomanian); 4, C. fraasi (fallax) and C. lehneri-Praetaberina bingistani assemblage zone (Late Cenomanian); 5, Nezzazatinella picardi-Mangashtia-Dicyclina assemblage zone (Early Turonian). Based on the petrographic and sedimentological analyses, some 13 carbonate microfacies were identified. The investigated microfacies confirm a ramp-type paleoenvironment. These microfacies, from distal to proximal environments, consist of: MF1:

Fahliyan Formation is importance in terms of Zagros stratigraphy since it is one of the oil reservoir rocks at the Jurassic-Cretaceous boundary. This rock unit consists of two types of deep and shallow facies in Zagros area. Recognition of bio-zones as well as discontinuity or continuity between the studied formation and the encompassed strata is taken into consideration. In order to study biostratigraphy on Fahliyan Formation, the stratigraphic section of Kuh-e-siah in the northeast of Fars Province was selected. In this section, Fahliyan Formation is measured 345 m consisting of thin to medium-bedded of limestone with the interbeds of sandy and dolomitic limestones. Fahliyan Formation conformably overlies Surmeh formation and underlies the marls of Gadvan formation. Vertical distribution of the identified foraminifers and calcareous algae confirms presence of 3 biozones in the sediments of Fahliyan Formation, as follows: 1) Calpionella alpina zone; 2) Pseudochrysalidina conica zone; 3) Pseudocyclammina lituus-Trocholina sp. assemblage zone. Based on Established biozones, the age of Fahliyan Formation in Kuh-e-Siah section was determined from Berriasian to Late Hauterivian.

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