Nannofossils are good for biosratigraphy, since they are abundant, planktonic, rapidly evolving and largely cosmopolitan especially in the Late Cretaceous. With respect to this reality and due to the lack of any precise paleontological study, the nannofossils of Gourpi Formation were investigated in the north of Gachsaran. This formation consists of marl and clay limestone. In this study, for the first time, 23 genera and 43 spesies of nannofossils were identified. Based on the obtained nannofossils, the study section in Late Santonian to Late Maastrichtian in age corresponding to CC16-CC26.

The effect of the paleoclimatic and paleoenvironmental changes on the structure of the biotic communities are stronger and better recorded in the shelf area than in the open sea. The present study is devoted to impact of climatic events on some species of calcareous nannofossils. For this reason, 17 samples of surface sediments of the Persian Gulf were studied. Preservation of calcareous nannofossils in surface sediment samples was good and the dominant species were Gephyrocapsa oceanica, Emiliania huxleyi, Helicosphaera carteriand Calcidiscus leptoporus. The presence of these taxa indicated the Holocene sediments in the study area were deposited in the warm water and the Persian Gulf was a shallow and hyposaline basin in which productivity of calcareous nannofossils was high.

A calcareous nannofossils biostratigraphic study has been carried out on the chalky limestones located in South Gorgan, north of Iran. The study is aimed at determining the age and nannofossil biozonations of the well. The samples were prepared using smear slide technique. Thirty seven calcareous nannofossils species were identified and used to make biostratigraphic zonations and dating of the strata. The distribution of the calcareous nannofossils enabled the establishment of five zones: Quadrum trifidum (CC22), Tranolithus phacelosus (CC23), Reinhardtites levis (CC24), Arkhangelskiella cymbiformis (CC25) and Nephrolithus frequens (CC26) belonging to late Late Campanian – late Late Maastrichtian following standard zonation schemes of previous workers. The zones were based on the first and last occurrences of marker species.

Nannofossils are suitable for biostratigraphical studied since they are aboundant, planktonic, rapidly evolving and largly cosmopolitan, especially in Late Cretaceous.According to this, due to the lack of any precise Paleontological study, the nannofossil of Neyzar Formation has been investigated in type locality. This formation consists of thick- bedded glauconitic sandstone, shale and a sandy limestone bed in the upper part. The Neyzar Formation conformably overlies the Abtalkh Formation and is itself conformably overlained by the Kalat formation.  As a result of this study, for the first time, 22 genera and 42 species of nannofossils have been identified. Based on these obtained nannofossils, the section is Late Maasrichtian in age, corresponding to CC25- CC26 (Sissingh, 1977) (equivalent to CC25c-CC26a-b, Perch- Nielsen, 1985).

In this research, paleoecology of Baghmashah Formation in Rizu section based on calcareous nannoplanktons has been investigated. Baghmashah Formation is part of the Mago sedimentary mega sequence in the Tabas block that was located in the northern margin of the Neotethys Ocean in Jurassic-Cretaceous. The Baghmshah Formation in this section with 270m thickness mainly includes the alternation of green marl-shale with thin interlayers of calcareous sandstone. The study of calcareous nannofossils and index species of nannofossil indicates Berriasian-early Huterivian age for the Baghmashah Formation in this section. Investigation of the abundance of calcareous nannofossils in the studied section shows that the sedimentary basin of Baghmashah Formation in Rizu section located in low latitude with warm surface waters, and formation deposited in oligotrophic conditions with shallow environment.

The Gurpi Formation was measured and sampled in a stratigraphic section located on the northern limb of the Chenareh anticline to the north of Andimeshk. The thickness of the Gurpi Formation in this section is 288. 5 meters and its lower boundary with the Ilam Formation is abrupt while its upper boundary with purple shales of the Pabdeh Formation is gradual and continuous. Paleontological studies led to the identification of 67 species belonging to 45 genera from 20 families of calcareous nannofossils, which made it possible to recognize CC18 to CC26 biozones from Sissingh standard classification scheme and NP1 to NP5 biozones from Martini standard classification scheme equivalent to biozones CNP1 to CNP7 from Agnini et al. . Based on the identified biozones, the duration of deposition of the Gurpi Formation was determined to be early Campanian–Selandian. In this section, the Emam Hassan Limestone Member was recognized with a thickness of 112. 8 meters having been deposited during the early Maastrichtian. Both the lower and the upper boundaries of the Emam Hassan Limestone Member within the Gurpi Formation are continuous and gradual. The position of the Campanian–Maastrichtian, Maastrichtian–Danian (Cretaceous–Paleogene) and Danian–Selandian transitions in the Gurpi Formation were also determined in the studied section.

IntroductionThe Lut Block is alsom called the "Median Mass of East Iran". This basin is a region characterized by Jurassic-Cretaceous-Tertiary sequence (Stocklin and Nabavi, 1973). In this research, to determine the age of these sequence in the Sarayan region (Rumeshtik section), a detailed study of calcareous nannofossils under optical microscope was performed. This section, based on the structural classification of Iran, is located in…

Using calcareous nannofossils is a powerful way for biozonation in sub-stage level, especially in the Late Cretaceous and Cenozoic, because they are planktonic, cosmopolitan, abundant and have very short age. Considering lack of any precise paleontological studies about the Gurpi Formation in the NW of shiraz (Bavan), nannofossils chose to investigate. This Formation consists of shale, marl and limestone. In this study, 23 genera and 46 species of nannofossils were identified. According to the identified marker species, 14 biozones were diagnosed that classified as CC14-CC26 and NP1(Base of the Pabdeh Formation). According to these biozones, it has been suggested that this section is aged of the Gurpi Formation from Early Santonian to Danian. The existence of CC26-NP1 zonal marker species of the K/T boundary has been considered which indicates continuous sedimentation from the Late Cretaceous to Early Paleocene.

The Gurpi Formation at Anaran Anticline in SE of Lurestan Province consists of 269. 5 meters of marl with limey marl intercalations; additionally, two formal members’ viz. Seymareh limestone and Emam-Hasan argillaceous limestone are also exposed. Studies reveal the presence of 70 species of calcareous nannofossils belonging to 38 genera, based on which 8 standard global biozones were differentiated. Consequently, the Gurpi Formation was attributed to middle Campanian through Paleocene. There is a distinct hiatus at Cretaceous-Paleogene boundary based on paleontological evidence, as deduced from the absence of nannofossilbiozones NP1-NP4. It seems that the reactivation of Anaranlinement as paleohigh resulted in change of facies and a hiatus in the succession of Gurpi Formation at SE of Lurestan Province.

Calcareous Nannofossils of the Gurpi Formation have been investigated at Kalchenar section (Northwest of Izeh). In this section, the Gurpi Formation is mainly consists of marls, shaly marls and marly limestones. For introducing index species, calcareous nannofossil assemblages and biozones, 150 slides have been studied which led to the recognition of twelve biozones. As a result, 61 species, 35 genera of calcareous nannofossils were detected. According to the identified biozones, the age of the Gurpi Formation is Late Campanian to Late Paleocene (Late Selandian) and K/Pg boundary is continuous at the studied interval, that is corresponding to CC21-CC26 of zonation scheme of Sissingh (1977) and NP1- NP6 of zonation of Martini (1971).