Among the subfamily Orbitolininae, PALORBITOLINA LENTICULARIS Blumenbach, 1805 is a common facies marker prevailed in shallow marine deposits of the Tethys during Late Barremian-Early Aptian time span. This speciesis a eurytopic taxon having the high ability of adaptation to wide range of environmental conditions. This study is based on measurements on embryonic chamber and test diameter ofPALORBITOLINA LENTICULARIS. The specimens were collected from three surface sections which are arranged in east-west direction.Our data show that, depth of environment controls the diameter of embryonic chamber and size of the test. Furthermore, size of embryonic chamber increases through time during the Late Barremian to Early Aptian.

South west of Qayen area is one of the platform basins in the Thethys, which contains microfossils such as orbitolinids. Six species belonging to the genera Praeorbitolina, PALORBITOLINA, Palorbitolinoides, Mesorbitolina, and Conicorbitolina were identified in Qomenjan area. Based on orbitolinids species, two biozones including Mesorbitolina texana and PALORBITOLINA LENTICULARIS are suggested. The age of sediments is attributed to Late Baremian -Early Cenomanian and Early Aptian–Early Cenomanian. Based on occurrence and stratigraphic distributions of orbitolinids in the Qomenjan section and comparison with Cherchi and Schroeder's evolutionary model, Praeorbitolina cormyi–Conicorbitolina cuvilleri and PALORBITOLINA LENTICULARIS- Conicorbitolina cuvilleri phylogenetic lineage is suggested for the Qomenjan area herein. The most important changes in the phylogenetic lineage, represented in our research, are as follows: the change in the position of embryonic apparatus, the shape of the protoconch and subembryonic zone, increase in the size of embryonic apparatus and protoconch, increase in the number of subembryonic and deuteroconch partition.

For the microbiostratigraphical studies, a stratigraphical section (named Dareh-Goshayesh) has been selected in southeast of Maragheh, Northwestern Iran. The thickness of successions in the selected stratigraphic section is measured about 223. 6 m. The mentioned studied stratigraphic section is composed of two clastic and carbonate units. This succession unconformably overlies the Lar Formation and is overlain by the Upper Cretaceous strata paraconformably. Based on the micropaleontological studies, a diversified assemblage of foraminifera and calcareous algae has been determined and the age of the studied stratigraphic section is inferred as Late Barremian-Late Aptian. Also, during these studies, four biozones are determined as follows: PALORBITOLINA LENTICULARIS Range Zone, Balkhania balkhanica range zone, Orbitolina (Mesorbitolina) texana Zone and Orbitolina (Mesorbitolina) parva Zone. This paper presents the first micropalaeontological and lithostratigraphical studies.

The Lower Cretaceous Carbonate deposits of the Dariyan Formation of the High Zagros Belt are mainly composed of thick to medium bedded limestone. These deposits contain abundant and diversified benthic foraminifera which have been recovered from carbonate rocks. A rich assemblage of microfossils with characteristic: PALORBITOLINA LENTICULARIS (Blumenbach), Mesorbitolina subconcava (Leymerie), Mesorbitolina texana (Roemer), Mesorbitolina parva (Douglass) Pseudocyclammina hedbergi (Maync), Archalveolina reicheli (de Castro), Praechrysalidina infracretacea Luperto Sinni, Chofatella decipiens (Schlumberger), Debarina hahonerensis (Fourcade, Raoul et Vila), Rumanoculina ponticuli (Neagu), Rumanoloculina pseudominima (Bartenstein et Kovatcheva), Istriloculina cf. elliptica (Iovcheva) indicate paleoenviromental conditions of shallow water carbonate sedimentation and Urgonian type facies. Based on microfossils distribution and biozones identification in study sections, the age of the Dariyan Formation is assigned late Barremian-early Albian. The microfossils assemblages are regarded to be comparable with the Urgonian-type fauna known from the peri-Mediterranean Tethys in the Barremian-Albian time interval.

In order to study biostratigraphy of the Tirgan Formation in western Kopet Dagh, two surface sections including Navia – Robat Eshgh and Ghezelghan, were selected and 230 samples were collected. The Tirgan Formation was measured with a total thickness of 237 and 192 meters in Navia and Ghezelghan sections respectively and was represented by thick and sometimes medium bedded, grey and weathered cream colored limestones in two localities. In Navia section, the Tirgan Formation conformably overlies the Zard – Shurijeh Formation with sharp lithological changes. However, as a result of being located in the core of an anticline, this boundary is not determined in Ghezelghan section. The Tirgan Formation disconformably underlies the Abderaz Formation in Navia section while conformably underlies the Sarcheshme Formation at Ghezelghan section. As a result of biostratigraphical investigations, 58 species belonging to 68 genera of foraminifera were identified in the Tirgan Formation. Based on benthic foraminifera two biozones were determined as follows: 1. PALORBITOLINA LENTICULARIS Taxon Range Zone 2. Novalesia producta – Orbitolina spp. assemblage zone According to the determined biozones and fossils associations, the age of the Tirgan Formation is Barremian – Early Aptian in both sections. The comparison of the Tirgan Formation, in two-mentioned sections, shows some differences. In terms of biostratigraphy, there is not any significant distinctions, except for thickness difference in biozones.

The early-mid Cretaceous carbonate sequences in the northeast of Rafsanjan city contain abundant and diverse foraminifera assemblages. A stratigraphic section of these sequences has been sampled for biostratigraphical and paleoenvironmental studies. The studied section was subdivided into two informal lower and upper units based on lithological characteristics. The former is composed of coloured marls intercalated with a few limestone intercalations. Planktonic foraminifera, oligosteginids and radiolarian are most components of it. The upper unit consists of fossiliferous limestones with intercalation of marls, rich in benthic foraminifera and calcareous algae that form cliff walls. The lower unit is characterised by r-selected hedbergellids, reflecting nutrient-rich/eutrophic marine environments. Whiles an abundance of cone-shaped orbitolinids, calcareous algae, and invertebrate organisms (echinoids, corals, and Mollusca) reflect deposition in the photic zone of shallow water marine platforms with stable temperature and salinity conditions. The biostratigraphic data allow us to date the Lower Cretaceous successions between Barremian and probably the early Cenomanian. One planktonic and five benthonic foraminiferal biozones are identified which include:Hedbergella spp. Assemblage ZonePALORBITOLINA LENTICULARIS ZonePraeorbitolina spp. Assemblage ZoneMesorbitolina parva ZoneMesorbitolina texana ZoneMesorbitolina subconcava Zone

IntroductionThe Kopet-Dagh sedimentary basin was formed in northeast Iran, southwestern Turkmenistan and north Afghanistan after closure of the Paleotethys Ocean following the Middle Triassic orogeny (Ruttner, 1993). Tirgan Formation, in Kopeh-Dagh basin consists of thick-bedded orbitolinid limestones, limy shale– marl with thin intercalation of limestone….

Harmful algal blooms caused by dinoflagellates have significant adverse effects on environmental and public health. This study aimed to investigate the effect of water physicochemical parameters on the annual cycle of epiphytic dinoflagellates in the northern Chabahar Bay coastal waters of the Oman Sea (Iran). The macroalgal samples with associated epiphytes were collected seasonally from 6 coastal sites in spring, summer, atumn 2019 and winter 2020. The water physicochemical parameters were measured, and the data were analyzed using a one-way ANOVA and the principal component analysis (PCA). Twelve potentially toxic dinoflagellate species from five genera were identified during the four sampling seasons. Amphidinium carterae with an average of 11. 22% and A. operculatum with an average of 10. 77% of the total abundance of epiphytic dinoflagellates were the dominant species, and Gambierdiscus australes showed an average of 6. 48%. Based on the PCA, the abundance of certain species was found to be influenced by different environmental factors. The PCA revealed that NO2, NO3 and SiO4 values had the greatest impact at sites with high abundances of A. operculatum, Prorocentrum concavum, P. emarginatum, P. rhathymum and G. balechii. Furthermore, PO4 concentration had the greatest impact at the sites with high abundances of A. carterae, P. lima, Ostreopsis LENTICULARIS, O. heptagona, G. balechii, G. toxicus, G. australes and Coolia monotis. The results obtained highlighted a significant impact of dissolved oxygen, pH, salinity, temperature and nutrients on the epiphytic dinoflagellate species abundances in the study area.