Early Cretaceous benthic foraminiferal biozonation of the Fahliyan and Gadvan Formations in the Assaluyeh and Halegan stratigraphic sections, Zagros Basin, Southwest of Iran

摘要

Early cretaceous sediments (Fahliyan and Gadvan Formations) in the Coastal Fars (namely Assaluyeh and Halegan), Zagros fold-thrust belt, SW Iran, were measured and sampled for micropaleontological investigations. In this research, Fahliyan Formation lies unconformably on the Hith/Surmeh formations and the Gadvan Formation overlies the Fahliyan Formation with conformable contact. The Gadvan Formation overlies by Dariyan Formation; this contact is sharp and conformable. The Fahliyan Formation in these stratigraphic sections can be divided into two informal members: Lower Fahliyan member and Upper Fahliyan member; and the Gadvan Formation was divided into three informal members: Lower Shale member, Khalij member and Lower Shale member. The Fahliyan Formation and Gadvan Formation in the Zagros include a diversified assemblage of benthic foraminifera and dasycladalean algae. In Assaluyeh and Halegan sections based on foraminifers, three biozones and one subzone are recognized that in ascending order are: (1) Pseudochrysalidina (Dukhania) zone (Berriasian), (2) Pseudocyclammina lituus zone (Valanginian-Hauterivian), (3) Orbitolina-Choffatella-Salpingoporella dinarica assemblage zone (Barremian), and (4) Montseciella arabica subzone (Barremian).