First record of Gyroconulina columellifera Schroeder & Darmoian, 1977 (larger benthic foraminifera) from the Maastrichtian Tarbur Formation of SW Iran (Zagros Fold-Thrust-Belt)

Abstract

The larger benthic foraminifera Gyroconulina columellifera Schroeder & Darmoian, 1977 (type-locality: Maastrichtian Aqra Formation of Iraq) is described for the first time from two sections of the Maastrichtian Tarbur Formation of the Zagros Fold-Thrust-Belt, SW Iran. New details on its wall microstructure are provided. The microfacies is represented by bioclastic wacke-/pack-/grainstones with benthic foraminifera (e.g., Loftusia ssp., Neobalkhania bignoti, Omphalocyclus macroporus) and dasycladalean algae. The Iranian discoveries give further evidence for the biostratigraphic importance of the taxon. The biostratigraphy of the Tarbur Formation based on larger benthic foraminifera is reviewed and critically discussed. Both Gyroconulina columellifera Schroeder & Darmoian, and the dasycladale Pseudocymopolia anadyomenea (Elliott), which have been first described from the Maastrichtian of Iraq, are now also reported from the Tarbur Formation of Iran. Their restricted occurrences along the southeastern northern margin of the Arabian plate and the Taurides of Turkey (Anatolian plate) are indicative for a Late Cretaceous provincialism, partly coinciding with the larger Loftusia bioprovince.