Biostratigraphy and Sequence Stratigraphy of the Tarbur Formation (Maastrichtian) from Iranian Zagros Foreland Basin, Southwest of Iran

Shallow carbonate deposits (Tarbur Formation) were formed in the Zagros foreland basin with dynamic tectonics during the Maastrichtian age. From the viewpoint of reconstruction of depositional conditions in these deposits, studies of biostratigraphy, microfacies, microtaphofacies, and sequence stratigraphy were performed in a single area at Tang-e Shabi Khoon, northwest of Zagros. Based on the identification of two assemblage zones consisting of benthic foraminifera in these strata, the formation was deposited during the middle to late Maastrichtian. The number of cycles in test size and type of coiling in Loftusia decreased from the study area toward the northwest of the Neotethys basin. The input of clastic sediments affected the distribution of Loftusia and rudists in the study area. Nine microfacies, six microtaphofacies, and one terrigenous facies (shale) were identified based on the sedimentary features. These deposits of the middle-late Maastrichtian were deposited on a homoclinal carbonate ramp. The platform can be divided into restricted and semi-restricted lagoon, shoal, and open marine environments. In the study area, the deposits of the Tarbur Formation were deposited during four third-order depositional sequences. Local fault activities affected the formation of depositional sequences in the study area.