The so-called “Upper Orbitolina Limestone” of Isfahan is a relatively thick lithological unit of the Taft Formation, cropping out in Central Iran, that is known for its orbitolinid inventory. An integrated biostratigraphy based on agglutinated benthic foraminifera (mainly orbitolinids) and calcareous nannofossils was carried out for the unit. This upper part of the Taft Formation is dated here as early to middle Aptian on the basis of orbitolinids such as Iraqia simplex Henson, Dictyoconus? pachymarginalis Schroeder, Paleodictyoconus cf. cuvillieri (Foury), Mesorbitolina lotzei (Schroeder), and Mesorbitolina parva (Douglass). Calcareous nannofossil index taxa appearing in the upper part of the “Upper Orbitolina Limestone” and also in the underlying shaly unit, including Percivalia fenestrata (Worsley), Percivalia sp., Hayesites irregularis Thierstein, Watznaueria barnesiae Perch-Nielsen, ?Phosterolithus prossii Aguado, ?Rhagodiscus achlyostaurion Hill, R. angustus Stander, Micrantholithus sp., and Eprolithus floralis Stander, support the assigned age by orbitolinids. Based on the discovery of lower Aptian deposits from the “Upper Orbitolina Limestone” (previously assigned to the upper Aptian), the Lower Cretaceous stratigraphy of the Isfahan area is revised.

伊斯法罕所谓的“上轨道石灰岩”是塔夫脱组的一个相对较厚的岩性单元，位于伊朗中部，以其轨道石库存而闻名。对该单元进行了基于凝集的底栖有孔虫（主要是眼眶科动物）和钙质纳米化石的综合生物地层学。塔夫脱组的这个上部在这里的年代可以追溯到早期到中期的阿普蒂安，基于如伊拉克单纯形Henson、Dictyoconus ? pachymarginalis Schroeder, Paleodictyoconus cf. cuvillieri（Foury），Mesorbitolina lotzei（施罗德），和Mesorbitolina麦穗鱼（道格拉斯）。钙质纳米化石指数分类群出现在“上轨道石灰岩”的上部以及下伏的页岩单元中，包括Percivalia fenestrata (Worsley)、Percivalia sp.、Hayesites impreis Thierstein、Watznaueria barnesiae Perch-Nielsen 、? Phosterolithus prossii Aguado, ? Rhagodiscus achlyostaurion Hill, R . angustus旁观者，Micrantholithus属和Eprolithus floralis旁观者，通过orbitolinids支持所赋予的时代。基于在“上轨道层”中发现了下阿普蒂安矿床 Limestone”（以前分配给上阿普蒂安），对伊斯法罕地区的下白垩统地层进行了修订。