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Middle–Late Devonian boundary conodonts from Anarak and Sar-Ashk sections, central Iran

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The Middle/Late Devonian boundary is investigated based on twenty-four conodont species and subspecies from the Anarak and Sar-Ashk sections in the northwest and southeast of Central East Iran Microplate. The earliest Frasnian strata are defined by the first appearance of Ancyrodella rotundiloba pristina and can be correlated with the global stratotype in the Montagne Noir, South of France. The Late Givetian – Early Frasnian carbonates of the Bahram Formation in the Sar-Ashk section transgressively overlie the sandstones of the Padeha Formation, whereas the coeval interval in the Anarak section composes the middle part of the Bahram Formation. | Turkish Journal of Earth Sciences Turkish J Earth Sci 2022 31 71-84 http journals.tubitak.gov.tr earth TÜBİTAK Research Article doi 10.3906 yer-2011-5 Middle Late Devonian boundary conodonts from Anarak and Sar-Ashk sections central Iran 1 2 1 Hossein GHOLAMALIAN Vachik HAIRAPETIAN Mohammad POOSTI 1 Department of Geology Faculty of Sciences University of Hormozgan Bandar Abbas Iran 2 Department of Geology Esfahan Khorasgan Branch Islamic Azad University Esfahan Iran Received 06.11.2020 Accepted Published Online 22.11.2021 Final Version 28.01.2022 Abstract The Middle Late Devonian boundary is investigated based on twenty-four conodont species and subspecies from the Anarak and Sar-Ashk sections in the northwest and southeast of Central East Iran Microplate. The earliest Frasnian strata are defined by the first appearance of Ancyrodella rotundiloba pristina and can be correlated with the global stratotype in the Montagne Noir South of France. The Late Givetian Early Frasnian carbonates of the Bahram Formation in the Sar-Ashk section transgressively overlie the sandstones of the Padeha Formation whereas the coeval interval in the Anarak section composes the middle part of the Bahram Formation. Conodont biostratigraphy of Late Givetian Early Frasnian strata in both sections revealed the presence of the Lower hermanni to Lower hassi zones. A new polygnathid species Polygnathus anarakensis is also proposed. Key words Givetian Frasnian boundary conodont biostratigraphy Iran 1. Introduction Ancyrodella rotundiloba early form Feist and Klapper Eifelian marine strata are rarely exposed in central 1985 Klapper 1985 Klapper et al. 1987 . Ancyrodella Iran e.g. Zefreh area NE of Esfahan which is studied rotundiloba pristina has recently been accepted as the by Brice et al. 2006 . On the other hand Givetian to synonym of An. rotundiloba early form Klapper and Famennian sequences are extensively cropped out in the Kirchgasser 2016 so we follow this opinion and apply Central-East