Distribution of Alveolina assemblages in the Ypresian (Ilerdian-Cuisian) successions from Iran and Turkey (central and western Tethys): biostratigraphic implications for regional correlation

Benthic foraminiferal assemblages dominated by Alveolina species from the Ypresian (Ilerdian-Cuisian) are studied herein from numerous localities of Iran and Turkey. From these successions, highly diversified assemblage of 58 alveolinid species are identified along with their detailed biostratigraphical application, which resulted in the recognition of eight shallow benthic zones (SBZ5-SBZ12). Our findings are based upon the distribution ranges of Alveolina from the Ilerdian-Cuisian sediments in Iran (Central Tethys) that are considered to have a strong affinity with their coeval fauna in Turkey (Western Tethys). In this study, the wide expansion ranges of Alveolina permit us to achieve a high-resolution biostratigraphy and apply the shallow benthic zones of the peri-Mediterranean region (Western Tethys) to the Ilerdian-Cuisian successions in Iran (Central Tethys). Nevertheless, the distribution of some Alveolina species, even the zonalmarkers consisting of Glomalveolina lepidula, Alveolina ellipsoidalis, A. pisiformis, A. laxa, A. subpyrenaica, A. varians, A. fornasinii and A. canavarii are found occurring at younger stratigraphic levels in Iran and/or Turkey than in the western European shallow marine deposits.