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Two Late Cenomanian -Early Turonian (C-T) intervals of the eastern part of the Kopet-Dagh basin, NE Iran have been investigated to evaluate the response of planktonic foraminifera to the geological event OAE2. The Gharesu and Taherabad sections with the thicknesses of 30 m and 22.5 m are composed of shale and marl interbedded with glauconitic sandstone. Three biozones Rotalipora cushmani, Whiteinella archaeocretacea and Helvetoglobotruncana helvetica were recognized based on study of planktonic foraminifera, in these sections. We observed the patterns of planktonic foraminiferal assemblage changes around the C-T boundary and divided this succession into several successive intervals. This study confirms that OAE2 was a long term event. A gradual perturbation in the study successions starts in the interval 1 with low abundance and diversity of planktonic foraminifera. An enhanced oxygen minimum zone (OMZ) occurs in the interval 3 which coincides with a temporary absence of planktonic foraminifera and sedimentation of framboidal pyrite. High diversity of planktonic foraminifera and appearance of new genera in the interval 5 indicate return of normal conditions to the basin. A significant short-term sea surface temperature cooling is also indicated by planktonic foraminiferal turnover and carbonate contents in the interval 2 which is comparable with other parts of the Tethys Ocean, Boreal sea and Atlantic region.

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The most comprehensive studies of LBF of the Eocene shallow-water sections of Iran were conducted by Rahaghi (1978, 1980, 1983) as well as Rahaghi and Schaub (1976). Aside from the study of Hottinger (2007) (Jahrum Formation, Shiraz area, Iran), only a few studies have been deeply carried out on LBF (such as alveolinids and nummulitids) with more precise stratigraphic records (Hadi et al., 2015, 2016b; Mosaddegh et al., 2017). Investigations of LBF major groups (alveolinids, nummulitids, and orthophragminids) suggest 20 shallow water benthic foraminiferal biozones (SBZ1-20) for Paleocene-Eocene Tethys (Serra-Kiel et al., 1998) and the aforementioned zonation has been extensively utilized in more than 400 articles published so far. Research performed on Eocene LBF in Iran (westerncentral Tethys) would provide significant data for a fundamental understanding of the relationship between the LBF and migration pathways. In addition, LBF was properly used as an indispensable tool for reconstructing Abstract: A high diversity of larger benthic foraminifera (LBF) fauna is recognized from the Ilerdian-Cuisian sedimentary succession for the first time of the Birjand region, Sistan Suture Zone of eastern Iran. These foraminifera are described in accordance with the standard shallow benthic zonation, placing considerable emphasis on biostratigraphic and microfacies analysis implications. Four shallow benthic zones (SBZ8 and SBZ10-12) have been designated in LBF horizons comprising index zonal markers such as Alveolina elliptica nuttalli (Davies), A. decipiens (Schwager), A. cf. oblonga, A. cf. minuta, A. cf. rugosa, A. cf. decastroi, A. aff. cremae, A. frumentiformis, A. aff. palermitana, N. cf. atacicus (Leymerie), N. tauricus (De la Harpe), N. pratti (d' Archia & Haime), N. polygyratus (Deshayes), N. cf. distans (Deshayes), Assilina sublaminosa (Gill), A. placentula (Deshayes), Asterocyclina cf. schweighauseri (Less), Discocyclina archiaci cf. staroseliensis (Less), and D. cf. archiaci bartholomei (Schlumberger). Five microfacies types including Alveolina-Opertorbitolites packstone (locally grainstone), nummulitids-Alveolina rudstone, Nummulites rudstone, Assilina-Nummulites rudstone, and orthophragminid-nummulitid pack-rudstone have been defined in the current study. Microfacies type 1 is finely characterized by high abundance of Alveolina with the predominance of A-form and globular to slightly elongate forms. Microfacies type 2 is dominated by small nummulitids in association with the abundance of the most diverse Alveolina species. Microfacies type 3 is composed of a diverse community of nummulitids, principally Nummulites A-forms along with Assilina. Microfacies type 4 is distinguished by a high diversity of not only A-and B-forms of Nummulites, but also Assilina specimens. Eventually, orthophragminids and nummulitids are common in microfacies type 5. Analysis of the Ilerdian-Cuisian deposits on the basis of the distribution of both biotic and abiotic components suggests depositions in a shallow ramp environment with ...

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High resolution sampling across the Cretaceous/Paleogene boundary (K/Pg) at the Galanderud section in northern Iran provides the most expanded and continuous section for us to consider biostratigraphy and the mass extinction pattern of Cretaceous planktic foraminifera. Based on planktic foraminifera, four biozones and five sub-biozones have been identified across the K/Pg boundary. These biozones include the Abathomphalus mayaroensis Biozone (Plummerita hantkeninoides subbiozone), the Guembelitria cretacea Biozone (including two sub-biozones: the Hedbergella holmdelensis and the Parvularugoglobigerina longiapertura), the Parvularugoglobigerina eugubina Biozone (including two subbiozones: the Parvularugoglobigerina Sabina and the Eoglobigerina simplicissima) and finely the Parasubbotina pseudobulloides Biozone. Planktic foraminiferal extinction occurred over a brief period, with 3% of the species disappearing in the late Maastrichtian, and 72% of the species becaming extinct at the K/Pg boundary. About 25% of the species survived into the early Danian. Extinction of 73% of the species at the K/Pg boundary is very compatible with the effect of a large asteroid impact.