Biostratigraphy of Dariyan Formation in Lar Anticline (north east Gachsaran) and Lower Cretaceous sediments in Kolah-Ghazi area (south-east Isfahan)

In order to identify foraminifera and determine the precise age of lower Cretaceous in Zagros and Central Iran basins, Dariyan Formation in Lar Anticline (north east Gachsaran) and Kolah-Ghazi section (south-east Isfahan province) were measured and investigated. Dariyan Formation in the studied section includes 111 ms of thick, medium to thin layers of limestone, marl and marly limestone. The Lower Cretaceous deposits in Kolah-Ghazi section also is 260 ms thick which includes thick to medium layer limestone and shale. Based on the fossil characteristics and biostratigraphical studies of Lar Anticline section, 28 benthonic foraminifera and 4 planktonic foraminifera have been identified that classified in 4 biozones: Hedbergellids - Orbitolinids assemblage zone, Mesorbitolina texana zone, Mesorbitolina gr. subconcava zone, Favusella washitensis rang zone. In Kolah-Ghazi section (south-east Isfahan), 21 benthonic and 1 planktonic foraminifera have been identified and consequently 2 biozones are recognized as follow: Mesorbitolina texana zone, Mesorbitolina gr. subconcava zonethe studied areas were correlated with some sections of the Dariyan in Kuh-e-Fahliyan, Kuh-e- Mangasht and Meymand. Accordingly, the sedimentation of two studied sections in Lar Anticline and Kolah-Ghazi section were started from Late Aptian which were later than the other sections, and the end of sedimentation in the Kolah-Ghazi section was earlier than the other sections in the Late Aptian age, while the end of sedimentation of Dariyan Formation in other sections was in Early Albian age.