A model for the paleoenvironmental distribution of larger foraminifera of Oligocene–Miocene carbonate rocks at Khaviz Anticline, Zagros Basin, SW Iran

Abstract

Platform carbonate sediments of Oligocene–Miocene age (Asmari Formation) in the Zagros Basin (SW Iran) have been investigated in order to determine their paleoecology and depositional environment. The Zagros Basin is the result of the opening and closure of the Neo-Tethys Ocean along the northeastern border of the Arabian Plate. The thick sedimentary sequences of the Zagros Basin contain rocks ranging in age from Cambrian to recent. The geological evidence suggests that the region was part of a passive continental margin, which subsequently underwent rifting in the Permo-Trias and collision in the Late Tertiary. The Asmari carbonate system was dominated by foraminifera and corallinacean assemblage. Based on the distribution of the larger foraminifera, four assemblage zones have been recognised. Facies analysis allowed the recognition of nine microfacies types that are grouped into three depositional environments that correspond to the inner, middle and outer shelf. The biota assemblage of the Asmari Formation suggests that carbonate sedimentation took place in tropical waters and oligotrophic to slightly mesotrophic conditions. Our detailed analysis of microfacies and paleoecology shows that the Asmari Formation deposited on a carbonate open shelf dominated by heterozoan and, subordinately, photozoan skeletal assemblage.

Keywords:

• Asmari Formation
• Oligo-Miocene
• paleoecology
• larger benthic foraminifera
• Zagros Basin
• sedimentary environment

Acknowledgements

The authors wish to thank the reviewers for their helpful and constructive comments. We would also like to thank the University of Isfahan for providing financial support and National Iranian South Oil Company for fieldwork logistics.