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

摘要

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 theopening and closure of the Neo-Tethys Ocean along the northeastern border of the Arabian Plate. The thick sedimentarysequences of the Zagros Basin contain rocks ranging in age from Cambrian to recent. The geological evidence suggests thatthe region was part of a passive continental margin, which subsequently underwent rifting in the Permo-Trias and collisionin the Late Tertiary. The Asmari carbonate system was dominated by foraminifera and corallinacean assemblage. Based onthe distribution of the larger foraminifera, four assemblage zones have been recognised. Facies analysis allowed therecognition 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 intropical waters and oligotrophic to slightly mesotrophic conditions. Our detailed analysis of microfacies and paleoecologyshows that the Asmari Formation deposited on a carbonate open shelf dominated by heterozoan and, subordinately,photozoan skeletal assemblage.