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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.

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In the present study, over 3000 m of Upper Cretaceous sediments (Tarbur Formation) in seven stratigraphic, columnar sections were studied. The area is located in the Zagros mountain ranges of southwestern Iran, attributed to the converging continental Arabian Shield, and is interpreted as the result of subduction and collision. Based on foraminiferal studies of the Tarbur Formation in the sections, we have established many new biozones in the stratigraphic sections. However, investigations of the biozones indicate that there is no lithostratigraphic variation between the Upper Cretaceous and Lower Paleocene sediments in some of the studied sections. The concept of widespread formations and lithologic correlations is not applicable in this area, probably as a result of the tectonic unrest at that time. The biostratigraphic boundary between the Cretaceous and the Lower Paleocene is nevertheless well defined by the intraformational boundary in the sections.

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The Kazhdumi Formation is one of the most significant rock units in the Bangestan Group in Zagros Basin. In this study, one section of the Kazhdumi Formation (Kuh-e-Rahmat) was selected for research. The section is extended approximately 89 m thick. The lower lithostratigraphic limit of the Kazhdumi Formation is marked by an oxidized zone, while the upper boundary is described as gradational type. The stratigraphic distribution of foraminifer taxa confirms two biozones in the studied section: Hemicyclammina sigali and Mesorbitolina subconcava in the Assemblage Zone and Mesorbitolina aperta in the range zone. Based on the investigated calcareous algae, Trinocladus tripolitanus, Range Zone is described. The identified calcareous algae are well distributed along Kazhdumi Formation. According to the received data of the established biozones, the age of the Kazhdumi Formation is Albian.

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