Santonian-Campanian planktonic foraminifera biostratigraphy of the northern Moghan area (NW Iran): implications for the
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ORIGINAL PAPER
Santonian-Campanian planktonic foraminifera biostratigraphy of the northern Moghan area (NW Iran): implications for the timing of Cretaceous marine transgression Mohsen Yazdi-Moghadam 1 & Yadolah Ezampanah 2 Received: 28 May 2020 / Accepted: 2 September 2020 # Saudi Society for Geosciences 2020
Abstract An Upper Cretaceous deep marine unit containing planktonic foraminifera was studied based on the material recovered from a subsurface section at the northern part of the Moghan area. The unit contains a relatively diverse assemblage of planktonic foraminifera, which allowed identifying a number of three biozones spanning the late Santonian to early late Campanian. These are Dicarinella asymetrica Zone, Globotruncanita elevata Zone, and Globotruncana ventricosa Zone. Based on the stratigraphic values of the identified planktonic foraminifera, a late Santonian to middle-late Campanian age is ascribed to the examined strata. The biostratigraphic results also point to the earlier marine transgression in the northern Moghan area starting in the late Santonian. Our biostratigraphic results indicate a prominent stratigraphic hiatus at the contact of Upper Cretaceous unit with the overlying Sarmatian strata, comprising the late Campanian to middle Serravallian. Keywords Biostratigraphy . Planktonic foraminifera . Upper Cretaceous . Moghan area . Paratethys
Introduction During the Upper Cretaceous, different structural units of Iran (including Zagros, Kopet-Dagh, Central Iran, Moghan area, etc.) are characterized by deposition of shallow and deep marine carbonates and marlstones (e.g., James and Wynd 1965; Stöcklin and Setudehnia 1971; Setudehnia 1972; Motiei 1993). Although these deposits are formally named in the Zagros belt (Sarvak, Surgah, Ilam, Gurpi, Tarbur formations) and also in the Kopet-Dagh region (Abderaz, Abtalkh, Neyzar, Kalat formations), they are generally mapped as “Cretaceous strata” in Central Iran and the Moghan area (e.g., FOL 2000; Omidvar et al. 2016, 2018; YazdiMoghadam et al. 2017). Planktonic foraminifera are usually abundant in Cretaceous-Neogene deep marine deposits. The
Responsible Editor: Beatriz Badenas * Yadolah Ezampanah [email protected] 1
National Iranian Oil Company Exploration Directorate, Sheikh Bahayi Square, Tehran, Iran
2
Geology Department, Earth Sciences Faculty, Bu-Ali Sina University, Hamadan, Iran
group has been largely used for biostratigraphic studies of their hosting rocks throughout the Tethys. In Iran, most of the planktonic foraminiferal biostratigraphic studies have been devoted to the Zagros fold and thrust belt, Kopet-Dagh, and Central Iran due to their known importance as petroleum bearing areas (e.g., Ghasemi-Nejad et al. 2006; Piryaei et al. 2010; Beiranvand et al. 2014; Sarfi et al. 2015; Ezampanah et al. 2018a, b; Yazdi-Moghadam et al. 2018). The Moghan area is known as one of the prolific structural units of Iran (Willm et al. 1961; FOL 2000); however, the published detailed stratigraphic studies (including surface and subsurface section
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