New biostratigraphy and microfacies analysis of Eocene Jahrom Formation (Shahrekord region, High Zagros, West Iran); A carbonate platform within the Neo-Tethys oceanic realm

Abstract

Abstract The Eocene Jahrom Formation in High Zagros was studied in Kuh-e-Soukhteh and North Gahrou sections (southwest of Shahrekord region, Chaharmahal Bakhtiari Province). This formation, composed of limestone, marl, and dolomitic limestone (dolostone), accumulated on a marine platform within the Neo-Tethys ocean realm. It yields a rich foraminiferal fauna, in which three larger benthic foraminiferal assemblage zones were identified. Two assemblage zones in the North Gahrou section were correlated to the Ypresian and Bartonian, and one assemblage zone is represented in the Kuh-e-Soukhteh section and assigned to the Bartonian. A discontinuity marked by a hiatus from Cuisian to Lutetian in the North Gahrou section was most probably due to a concealed fault. According to microscopic textures and distribution of benthic foraminifera and other components (peloids, intraclasts, etc.), a gentle depth gradient from the inner ramp to the proximal outer ramp representing small scattered reliefs (shoal) may be reconstructed.