University of Isfahan Journal of Stratigraphy and Sedimentology Researches 2008-7888 37 1 2021 03 21 Volume 37, Issue 1 - Serial Number 82, Spring 2021 Volume 37, Issue 1 - Serial Number 82, Spring 2021 26246 FA Journal Article 2022 01 11 https://jssr.ui.ac.ir/article_26246_47845ef84452a333fb59748ed38e5cb6.pdf

University of Isfahan Journal of Stratigraphy and Sedimentology Researches 2008-7888 37 1 2021 03 21 Middle–Late Devonian conodont fauna of the Bahram Formation in the Shahzadeh Mohammad section, North of Kerman Middle–Late Devonian conodont fauna of the Bahram Formation in the Shahzadeh Mohammad section, North of Kerman 1 22 25156 10.22108/jssr.2020.124039.1172 FA Fattaneh Zamani Ph.D. Student, Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran Mehdi Yazdi Professor, Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran Ali Bahrami Associate Professor, Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran. Hameh Ameri Assistant Professor, Department of Ecology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran. Cathrin Girard Professor, Department of Paleontology (ISEM), University of Montpellier, CNRS, EPHE, IRD, Montpellier, France Claudia Spalletta Professor, Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Alma Mater Studiorum-Università di Bologna, Bologna, Italy. Journal Article 2020 07 20 Abstract Devonian deposits of the Bahram Formation with a thickness of 300 m were studied based on conodont fauna in Shahzadeh Mohammad section (33 km east of Zarand, 95 km north of Kerman city) in central Iran structural Zone. According to 31 identified species and subspecies and their stratigraphic development, nine conodont biozones belonging to the middle Givetian to the lower Famennian age were identified. The presence of Polygnathus ansatus determines the ansatus Zone and Icriodus arkonensis arkonensis, determines the age of middle Givetian for the base of the Bahram Formation, which is the oldest age determined for the base of the Bahram Formation. Based on conodont distributions and conodont biofacies, polygnathid-icrodid biofacies are the most abundant biofacies in the section, indicating the middle shelf environment for the studied deposits. Keywords: Devonian, Conodont, Bahram Formation, Givetian–Famennian, Biofacies. Introduction The Devonian, one of the most important periods in the Paleozoic, was a time of major sea-level changes and catastrophic events (Sandberg et al. 2002). Besides, it was a time of exceptionally high sea-level stand. It inferred widespread equable climates, which resulted in the most significant carbonate production and diversity of marine fauna in the Paleozoic (Gradstein et al. 2005). The Late Devonian was a time of many sea-level changes, catastrophic events, and two mass extinctions, knowledge of which is gained mainly through a high-resolution conodont biochronology (Sandberg and Ziegler 1996). The Devonian is the time for the radiation of fish and the appearance of the first ammonoids, insects, and amphibians. Vascular plants and forests became established; plants took over the land and became so plentiful that the first coal deposits were formed in tropical swamps. Besides, before the end of the period, land tetrapods appeared. Due to the greenhouse climate condition and sea-level highstand, global reef growth reached an acme in the Middle Devonian (Gradstein et al. 2005). Due to the relative rise of sea level, Middle and Late Devonian sediments were deposited in the northern, eastern, and central parts of Iran. In Central Iran, Middle and Late Devonian succession are exposed in the Kerman, Tabas, Yazd, and Isfahan regions. In Kerman, these deposits are limited to the northern parts of the region and are introduced and studied as Sibzar and Bahram formations. The Sibzar Formation, has few occurrences and only in two disjunct areas can be traced (Wendt et al. 2002). This formation is placed between the Padeha and the Bahram formations. The Bahram Formation consists of siliciclastic and carbonate strata. There is a complete profile from Lower to Upper Devonian deposits in the Shahzadeh Mohammad section, east of Zarand. The studied section is part of the Kerman-Tabas Block, which constitutes one of the individual structural units of the Central-East-Iranian Microcontinent. In this study, the biostratigraphy, biofacies, and sea-level changes of the Bahram Formation in the Shahzadeh Mohammad section have been investigated based on conodont fauna. Material & Methods In total, 300 m of the Middle–Upper Devonian successions (Bahram Formation) at the Shahzadeh Mohammad section has been measured. Forty samples, about 4–5 kg, were systematically collected and treated with conventional preparation methods. The samples were processed with diluted acetic/formic acid (20%). The residue was washed by sieving ((using sieve Mesh numbers 10, 30, 60, and 100). The conodonts were extracted from residues by hand picking. Discussion of Results & Conclusions Ancyrodella, Icriodus, Pelekysgnathus, Polygnathus are the present genera in this section. Conodont biofacies and relative sea-level changes of the Middle–Upper Devonian Shahzadeh Mohammad section have been investigated and compared with the global sea-level curve. The biofacies interpretation is based on the distribution of the above four genera in the conodont biofacies presented by Sandberg and Dreesen (1984). Since the dominant genera of this section are Icriodus and Polygnathus, frequency changes of these genera determine conodont biofacies and relative sea-level changes. Polygnathus indicates an increase and Icriodus indicates a decrease in the relative sea-level. The following biofacies were identified: icriodid, icriodid-polygnathid, polygnathid-icriodid, and polygnathid biofacies. Polygnathid-icriodid biofacies is the most abundant biofacies. Due to the presence of shallow-water species, the abundance of Icriodus and Polygnathus, the absence of the genus Palmatolepis, the middle shelf environment is determined for the Bahram Formation in the Shahzadeh Mohammad section. In general, all of the Devonian succession from the Kerman area have been deposited in a shallow-water environment, and generally indicates the shallow parts of the Paleotethys. Our examination has yielded new conodont data from the Bahram Formation in the Shahzadeh Mohammad section. The ansatus Zone to Palmatolepis glabra pectinata Zone (middle Givetian to lower Famennian) were assigned to the Bahram Formation within nine conodont zones (Zamani et al. 2020). Conodonts from the sample Sh7 (Polygnathus ansatus and Icriodus arkonensis arkonensis) indicate Givetian age for the basal part of the Bahram Formation; but Middle Frasnian age is reported in previous studies in this area. The first appearance of Ancyrodella rotundiloba pristina represents Givetian/Frasnian boundary at sample Sh12. Abstract Devonian deposits of the Bahram Formation with a thickness of 300 m were studied based on conodont fauna in Shahzadeh Mohammad section (33 km east of Zarand, 95 km north of Kerman city) in central Iran structural Zone. According to 31 identified species and subspecies and their stratigraphic development, nine conodont biozones belonging to the middle Givetian to the lower Famennian age were identified. The presence of Polygnathus ansatus determines the ansatus Zone and Icriodus arkonensis arkonensis, determines the age of middle Givetian for the base of the Bahram Formation, which is the oldest age determined for the base of the Bahram Formation. Based on conodont distributions and conodont biofacies, polygnathid-icrodid biofacies are the most abundant biofacies in the section, indicating the middle shelf environment for the studied deposits. Keywords: Devonian, Conodont, Bahram Formation, Givetian–Famennian, Biofacies. Introduction The Devonian, one of the most important periods in the Paleozoic, was a time of major sea-level changes and catastrophic events (Sandberg et al. 2002). Besides, it was a time of exceptionally high sea-level stand. It inferred widespread equable climates, which resulted in the most significant carbonate production and diversity of marine fauna in the Paleozoic (Gradstein et al. 2005). The Late Devonian was a time of many sea-level changes, catastrophic events, and two mass extinctions, knowledge of which is gained mainly through a high-resolution conodont biochronology (Sandberg and Ziegler 1996). The Devonian is the time for the radiation of fish and the appearance of the first ammonoids, insects, and amphibians. Vascular plants and forests became established; plants took over the land and became so plentiful that the first coal deposits were formed in tropical swamps. Besides, before the end of the period, land tetrapods appeared. Due to the greenhouse climate condition and sea-level highstand, global reef growth reached an acme in the Middle Devonian (Gradstein et al. 2005). Due to the relative rise of sea level, Middle and Late Devonian sediments were deposited in the northern, eastern, and central parts of Iran. In Central Iran, Middle and Late Devonian succession are exposed in the Kerman, Tabas, Yazd, and Isfahan regions. In Kerman, these deposits are limited to the northern parts of the region and are introduced and studied as Sibzar and Bahram formations. The Sibzar Formation, has few occurrences and only in two disjunct areas can be traced (Wendt et al. 2002). This formation is placed between the Padeha and the Bahram formations. The Bahram Formation consists of siliciclastic and carbonate strata. There is a complete profile from Lower to Upper Devonian deposits in the Shahzadeh Mohammad section, east of Zarand. The studied section is part of the Kerman-Tabas Block, which constitutes one of the individual structural units of the Central-East-Iranian Microcontinent. In this study, the biostratigraphy, biofacies, and sea-level changes of the Bahram Formation in the Shahzadeh Mohammad section have been investigated based on conodont fauna. Material & Methods In total, 300 m of the Middle–Upper Devonian successions (Bahram Formation) at the Shahzadeh Mohammad section has been measured. Forty samples, about 4–5 kg, were systematically collected and treated with conventional preparation methods. The samples were processed with diluted acetic/formic acid (20%). The residue was washed by sieving ((using sieve Mesh numbers 10, 30, 60, and 100). The conodonts were extracted from residues by hand picking. Discussion of Results & Conclusions Ancyrodella, Icriodus, Pelekysgnathus, Polygnathus are the present genera in this section. Conodont biofacies and relative sea-level changes of the Middle–Upper Devonian Shahzadeh Mohammad section have been investigated and compared with the global sea-level curve. The biofacies interpretation is based on the distribution of the above four genera in the conodont biofacies presented by Sandberg and Dreesen (1984). Since the dominant genera of this section are Icriodus and Polygnathus, frequency changes of these genera determine conodont biofacies and relative sea-level changes. Polygnathus indicates an increase and Icriodus indicates a decrease in the relative sea-level. The following biofacies were identified: icriodid, icriodid-polygnathid, polygnathid-icriodid, and polygnathid biofacies. Polygnathid-icriodid biofacies is the most abundant biofacies. Due to the presence of shallow-water species, the abundance of Icriodus and Polygnathus, the absence of the genus Palmatolepis, the middle shelf environment is determined for the Bahram Formation in the Shahzadeh Mohammad section. In general, all of the Devonian succession from the Kerman area have been deposited in a shallow-water environment, and generally indicates the shallow parts of the Paleotethys. Our examination has yielded new conodont data from the Bahram Formation in the Shahzadeh Mohammad section. The ansatus Zone to Palmatolepis glabra pectinata Zone (middle Givetian to lower Famennian) were assigned to the Bahram Formation within nine conodont zones (Zamani et al. 2020). Conodonts from the sample Sh7 (Polygnathus ansatus and Icriodus arkonensis arkonensis) indicate Givetian age for the basal part of the Bahram Formation; but Middle Frasnian age is reported in previous studies in this area. The first appearance of Ancyrodella rotundiloba pristina represents Givetian/Frasnian boundary at sample Sh12.

https://jssr.ui.ac.ir/article_25156_411c10a3dadf0452fc53fd32a988b06d.pdf

University of Isfahan Journal of Stratigraphy and Sedimentology Researches 2008-7888 37 1 2021 03 21 New findings in biostratigraphy of the Sarvak and Ilam formations of Abteymour Oil Field (Dezful Embayment) New findings in biostratigraphy of the Sarvak and Ilam formations of Abteymour Oil Field (Dezful Embayment) 23 44 25058 10.22108/jssr.2020.124889.1185 FA Reza Omidi PhD. Student in Stratigraphy and Paleontology, Department of Geology, Faculty of Earth Sciences, Isfahan University, Isfahan, Iran Abbas Sadeghi Department of Geology, University of Shahid Beheshti, Tehran, Iran 0000-0002-5515-0781 Mahboobeh Hosseini-Barzi Department of Geology, University of Shahid Beheshti, Tehran, Iran Narges Akbar Bas Kelayeh Fundamental Geological Survey, National Iranian South Oil Company, Ahvaz, Iran Journal Article 2020 09 14 Abstract Biostratigraphic studies of the Sarvak and Ilam formations in wells No. 1 and 14 of the Abteymour Oil Field led to the recognition of six species of foraminifers from the two mentioned formations for the first time. In this research, the species of Fischerina carinata and Spiroloculina cenomana in the Sarvak Formation and the species of Palaeosigmoilopsis apenninica and Sigmomassilina ottadunensis in the Sarvak and Ilam formations belonging to the suborder of MILIOLINA Delage and Herouard (1896) and the species Rotorbinella sp. nov. in the Sarvak and Ilam formation and Pararotalia boixae in the Sarvak and Ilam formations belonging to the suborder of ROTALIINA Delage and Herouard (1896) were identified and described. These species are not yet reported from the Sarvak and Ilam formations. Based on the identified fauna, the Sarvak Formation with a thickness of 812.98 and 238 meters in wells No. 1 and 14 respectively is Cenomanian–Turonian in age, and the Ilam Formation with a thickness of 151.7 and 136 meters in wells No. 1 and 14 respectively is Santonian–Campanian? in age. Keywords: Abeteymour Oil Field, Ilam Formation, Foraminifera, Rotaliidae, Sarvak Formation Introduction The Sarvak and Ilam formations, as one of the most important carbonate hydrocarbon reservoirs after the Asmari reservoir in the Zagros Basin, have special importance in petroleum studies. So far, several studies have been conducted on the two mentioned formations from different aspects especially biostratigraphic studies (James and Wynd 1965; Wynd 1965; Wood and Lacassagne 1956; Wells 1966, 1967, 1968; Stoneley et al. 1975; Speers 1967; Rahimpour-Bonab et al. 2012; Omidvar et al. 2014; Amiri Bakhtiar 1991; Khosroo Tehrani and Fonooni 1994; Allahbakhsh Ghiyasvand 2003; Teimourian 2004; Akbari Bas Kelayeh and Taheri 2005, 2006; Kamyabi Shadan 2005; Agh 2005; Sadeghi et al. 2006; Ghalavand 2009; Soleimani 2010; Ghobeyshavi et al. 2010; Sajjadi and Omidvar 2011; Omidvar 2011). However, these biostratigraphic studies of the Sarvak and Ilam formations in different areas of the Zagros Basin, introducing several biozones, some coexistence of foraminifera in these zones have been introduced . In the Dezful Embayment, due to the tectonic phases that occurred after Cenomanian and after Turonian (sub Hercynian tectonic phases), there is some absence of stratum or hiatus. The shallowing trend of the Late Albian to Cenomanian basin produced large amounts of shallow carbonate sediments of the Sarvak Formation in the Zagros Basin. However, during the Late Turonian, a regional uplift has taken place causing partial or complete erosion of the Turonian sediments, which create an erosional unconformitiy after Turonian, characterized by the development of iron-bearing sediments and sedimentary discontinuities in the Dezful Embayment and Fars areas. Omidi et al. 2018, in order to identify the fossil content with an emphasis on recognizing foraminifera of the Sarvak and Ilam formations in the south of Dezful embayment, studied two subsurface sections of wells 1 and 14 of the Abteymour oil field. They introduced four biozones based on the identification of 71 species belonging to 57 genera of foraminifera: one biozone in the Ilam Formation, called Biozone No. 1: Rotorbinella-Pararotalia Assemblage Zone, and three biozones in the Sarvak Formation called biozone No. 2: Nezzazatinella picardi-Dicyclina Schlumbergeri Assemblage Zone; biozone No. 3: Rotorbinella mesogeensis Total Range Zone and biozone No. 4: Nezzazata-alveolinid Assemblage Zone. Based on these identified biozones, the ages of the Sarvak and the Ilam formations are Cenomanian–Turonian and Santonian–Campanian, respectively. The identified benthic foraminifera in the Abteymour Oil Field is somehow similar to the other parts of the Zagros, but in addition to the benthic foraminifera reported in previous studies of these two formations; six other foraminifera species are identified and introduced from this oil field for the first time in this research. Since the Ilam and Sarvak formations face several high-pressure zones during drilling in the Abteymour oil field, identification of high-pressure oil and gas zones in strata is one of the issues that are of great importance. As a result, fossil studies, especially foraminifera can be helpful in finding the relative and sometimes exact location of high-pressure zones. The Ilam Formation in drilled wells in parts of the south of Dezful Embayment (Abteymour Oil Field) has low interest in terms of diversity of fossil genera and species (foraminifera); however, some foraminiferal members have been less studied, for example, the genus and species of the Rotaliidae family. In addition to the introduction of the Rotalia sp. 22-algae assemblage zone (due to the high diversity of Rotaliidae family members, sometimes up to 60 species, sp. 60) in the James and Wynd (1965) studies, and the high focus of systematic studies by Hottinger et al. (2014) on this family confirms the complexity and importance of the study in identifying and distinguishing the genus and species of this family; therefore, geologists on oil wells in Iran know the Ilam Formation as the "Rotalia Formation". Thus, the importance of the systematic study of the Rotaliidae family for separation of genera and species is more important. In this study, the foraminifera of the Ilam Formation have been systematically studied (to separate and distinguish several genera and species of Rotaliidae from each other), and this can be used to complete the chain of biostratigraphic studies in identifying high-pressure oil zones. In the Sarvak Formation, the study and knowledge of benthic foraminifera fossil assemblages could have great importance in the enrichment of fauna associations and recognizing biostratigraphic zones, determining the exact age of strata, knowing more local biozones, and identifying oil zones. Also, the rate of change in the diversity and abundance of foraminifera and their morphological characteristics increases in anoxic periods, for example, OAE1a (Leckie et al. 2002; Erba 2004). However, one of the biological characteristics of this incident is the presence of planktonic foraminifera with elongated chambers (Coccioni et al. 2006). However, here it is enough to describe the species that have been reported for the first time from the Sarvak and Ilam formations to identify more foraminifera and the fauna associations in the enrichment of the biozonations related to these two formation.. Material & Method In order to do biostratigraphy and identifying foraminifera in the Sarvak and Ilam formations in Abteymour Oil Field, the two wells of No.1 and 14, with the most suitable sample, were selected.A total of 1347 thin sections of the two wells (716 thin sections from well No. 1, mainly prepared from drilling cuttings and 631 thin sections from well No. 14, mostly prepared from drilling cores) were studied. These thin sections were studied microscopically to identify the microfossil contents, and after identification, they were photographed. Identification and description of the foraminifera were performed based on Loeblich and Tappan (1988), Boix (2007), Chiocchini et al. (2012), and Hottinger (2014). Discussion of Results & Conclusions The Sarvak and Ilam formations (Bangestan oil reservoir) are considered the second largest oil reservoir in Iran after the Asmari reservoir. Therefore, a careful study of the fossil content of these two oil formations is of particular importance in biostratigraphic studies. For this reason, in this study, a detailed study of the fossil content (especially foraminifera) of these two formations has been considered. The Ilam Formation in wells No. 1 and 14 has a thickness of 152 and 136 meters, respectively, and its lithology is mainly limestones and limestone with shale interbeds. The Sarvak Formation in well No. 1 is 813 meters thick, and in well No. 14, 238 meters of the Sarvak Formation has been drilled. The lithology of the Sarvak Formation is mainly limestones and dolomitic limestones. The biostratigraphy of the Sarvak and Ilam formations in wells No. 1 and 14 of Abteymour Oil Field, in addition to benthic foraminifera, which has been reported in previous studies of the Sarvak and Ilam formations, the following six benthic foraminifera are identified and introduced for the first time from these two formations:1- Fischerina carinata Peybernès, 1984 (Cenomanian, Sarvak Formation); 2- Spiroloculina cenomana Chiocchini, 2008 (Cenomanian, Sarvak Formation); 3- Sigmomassilina ottaduenesis Chiocchini, 2008 (Turonian, Sarvak Formation and Santonian–Campanian?, Ilam formations); 4- Paleosigmoilopsis apenninica Chiocchini, 2008 (Cenomanian–Turonian, Sarvak Formation); 5- Pararotalia boixae Piuz and Meister, 2013 (Cenomanian, Sarvak Formation and Santonian, Ilam Formation); 6- Rotorbinella sp. nov. (Turonian for Sarvak Formation and Santonian-Campanian? for Ilam Formation). These species have never been reported before from the Sarvak and Ilam formations. Abstract Biostratigraphic studies of the Sarvak and Ilam formations in wells No. 1 and 14 of the Abteymour Oil Field led to the recognition of six species of foraminifers from the two mentioned formations for the first time. In this research, the species of Fischerina carinata and Spiroloculina cenomana in the Sarvak Formation and the species of Palaeosigmoilopsis apenninica and Sigmomassilina ottadunensis in the Sarvak and Ilam formations belonging to the suborder of MILIOLINA Delage and Herouard (1896) and the species Rotorbinella sp. nov. in the Sarvak and Ilam formation and Pararotalia boixae in the Sarvak and Ilam formations belonging to the suborder of ROTALIINA Delage and Herouard (1896) were identified and described. These species are not yet reported from the Sarvak and Ilam formations. Based on the identified fauna, the Sarvak Formation with a thickness of 812.98 and 238 meters in wells No. 1 and 14 respectively is Cenomanian–Turonian in age, and the Ilam Formation with a thickness of 151.7 and 136 meters in wells No. 1 and 14 respectively is Santonian–Campanian? in age. Keywords: Abeteymour Oil Field, Ilam Formation, Foraminifera, Rotaliidae, Sarvak Formation Introduction The Sarvak and Ilam formations, as one of the most important carbonate hydrocarbon reservoirs after the Asmari reservoir in the Zagros Basin, have special importance in petroleum studies. So far, several studies have been conducted on the two mentioned formations from different aspects especially biostratigraphic studies (James and Wynd 1965; Wynd 1965; Wood and Lacassagne 1956; Wells 1966, 1967, 1968; Stoneley et al. 1975; Speers 1967; Rahimpour-Bonab et al. 2012; Omidvar et al. 2014; Amiri Bakhtiar 1991; Khosroo Tehrani and Fonooni 1994; Allahbakhsh Ghiyasvand 2003; Teimourian 2004; Akbari Bas Kelayeh and Taheri 2005, 2006; Kamyabi Shadan 2005; Agh 2005; Sadeghi et al. 2006; Ghalavand 2009; Soleimani 2010; Ghobeyshavi et al. 2010; Sajjadi and Omidvar 2011; Omidvar 2011). However, these biostratigraphic studies of the Sarvak and Ilam formations in different areas of the Zagros Basin, introducing several biozones, some coexistence of foraminifera in these zones have been introduced . In the Dezful Embayment, due to the tectonic phases that occurred after Cenomanian and after Turonian (sub Hercynian tectonic phases), there is some absence of stratum or hiatus. The shallowing trend of the Late Albian to Cenomanian basin produced large amounts of shallow carbonate sediments of the Sarvak Formation in the Zagros Basin. However, during the Late Turonian, a regional uplift has taken place causing partial or complete erosion of the Turonian sediments, which create an erosional unconformitiy after Turonian, characterized by the development of iron-bearing sediments and sedimentary discontinuities in the Dezful Embayment and Fars areas. Omidi et al. 2018, in order to identify the fossil content with an emphasis on recognizing foraminifera of the Sarvak and Ilam formations in the south of Dezful embayment, studied two subsurface sections of wells 1 and 14 of the Abteymour oil field. They introduced four biozones based on the identification of 71 species belonging to 57 genera of foraminifera: one biozone in the Ilam Formation, called Biozone No. 1: Rotorbinella-Pararotalia Assemblage Zone, and three biozones in the Sarvak Formation called biozone No. 2: Nezzazatinella picardi-Dicyclina Schlumbergeri Assemblage Zone; biozone No. 3: Rotorbinella mesogeensis Total Range Zone and biozone No. 4: Nezzazata-alveolinid Assemblage Zone. Based on these identified biozones, the ages of the Sarvak and the Ilam formations are Cenomanian–Turonian and Santonian–Campanian, respectively. The identified benthic foraminifera in the Abteymour Oil Field is somehow similar to the other parts of the Zagros, but in addition to the benthic foraminifera reported in previous studies of these two formations; six other foraminifera species are identified and introduced from this oil field for the first time in this research. Since the Ilam and Sarvak formations face several high-pressure zones during drilling in the Abteymour oil field, identification of high-pressure oil and gas zones in strata is one of the issues that are of great importance. As a result, fossil studies, especially foraminifera can be helpful in finding the relative and sometimes exact location of high-pressure zones. The Ilam Formation in drilled wells in parts of the south of Dezful Embayment (Abteymour Oil Field) has low interest in terms of diversity of fossil genera and species (foraminifera); however, some foraminiferal members have been less studied, for example, the genus and species of the Rotaliidae family. In addition to the introduction of the Rotalia sp. 22-algae assemblage zone (due to the high diversity of Rotaliidae family members, sometimes up to 60 species, sp. 60) in the James and Wynd (1965) studies, and the high focus of systematic studies by Hottinger et al. (2014) on this family confirms the complexity and importance of the study in identifying and distinguishing the genus and species of this family; therefore, geologists on oil wells in Iran know the Ilam Formation as the "Rotalia Formation". Thus, the importance of the systematic study of the Rotaliidae family for separation of genera and species is more important. In this study, the foraminifera of the Ilam Formation have been systematically studied (to separate and distinguish several genera and species of Rotaliidae from each other), and this can be used to complete the chain of biostratigraphic studies in identifying high-pressure oil zones. In the Sarvak Formation, the study and knowledge of benthic foraminifera fossil assemblages could have great importance in the enrichment of fauna associations and recognizing biostratigraphic zones, determining the exact age of strata, knowing more local biozones, and identifying oil zones. Also, the rate of change in the diversity and abundance of foraminifera and their morphological characteristics increases in anoxic periods, for example, OAE1a (Leckie et al. 2002; Erba 2004). However, one of the biological characteristics of this incident is the presence of planktonic foraminifera with elongated chambers (Coccioni et al. 2006). However, here it is enough to describe the species that have been reported for the first time from the Sarvak and Ilam formations to identify more foraminifera and the fauna associations in the enrichment of the biozonations related to these two formation.. Material & Method In order to do biostratigraphy and identifying foraminifera in the Sarvak and Ilam formations in Abteymour Oil Field, the two wells of No.1 and 14, with the most suitable sample, were selected.A total of 1347 thin sections of the two wells (716 thin sections from well No. 1, mainly prepared from drilling cuttings and 631 thin sections from well No. 14, mostly prepared from drilling cores) were studied. These thin sections were studied microscopically to identify the microfossil contents, and after identification, they were photographed. Identification and description of the foraminifera were performed based on Loeblich and Tappan (1988), Boix (2007), Chiocchini et al. (2012), and Hottinger (2014). Discussion of Results & Conclusions The Sarvak and Ilam formations (Bangestan oil reservoir) are considered the second largest oil reservoir in Iran after the Asmari reservoir. Therefore, a careful study of the fossil content of these two oil formations is of particular importance in biostratigraphic studies. For this reason, in this study, a detailed study of the fossil content (especially foraminifera) of these two formations has been considered. The Ilam Formation in wells No. 1 and 14 has a thickness of 152 and 136 meters, respectively, and its lithology is mainly limestones and limestone with shale interbeds. The Sarvak Formation in well No. 1 is 813 meters thick, and in well No. 14, 238 meters of the Sarvak Formation has been drilled. The lithology of the Sarvak Formation is mainly limestones and dolomitic limestones. The biostratigraphy of the Sarvak and Ilam formations in wells No. 1 and 14 of Abteymour Oil Field, in addition to benthic foraminifera, which has been reported in previous studies of the Sarvak and Ilam formations, the following six benthic foraminifera are identified and introduced for the first time from these two formations:1- Fischerina carinata Peybernès, 1984 (Cenomanian, Sarvak Formation); 2- Spiroloculina cenomana Chiocchini, 2008 (Cenomanian, Sarvak Formation); 3- Sigmomassilina ottaduenesis Chiocchini, 2008 (Turonian, Sarvak Formation and Santonian–Campanian?, Ilam formations); 4- Paleosigmoilopsis apenninica Chiocchini, 2008 (Cenomanian–Turonian, Sarvak Formation); 5- Pararotalia boixae Piuz and Meister, 2013 (Cenomanian, Sarvak Formation and Santonian, Ilam Formation); 6- Rotorbinella sp. nov. (Turonian for Sarvak Formation and Santonian-Campanian? for Ilam Formation). These species have never been reported before from the Sarvak and Ilam formations.

https://jssr.ui.ac.ir/article_25058_db0930766af44d30a92ee5b35d3e24bd.pdf

University of Isfahan Journal of Stratigraphy and Sedimentology Researches 2008-7888 37 1 2021 03 21 Biological evolution of the carbonate platform of the Taleh Zang Formation in Kermanshah region Biological evolution of the carbonate platform of the Taleh Zang Formation in Kermanshah region 45 66 25131 10.22108/jssr.2020.124937.1186 FA Mohammad Shalalvand M.Sc, Department of Sedimentary Basins and Petroleum, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran. Mohammadhossein Adabi Professor, Department of Sedimentary Basins and Petroleum, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran. Afshin Zohdi Assistant Professor, Department of Geology, Faculty of Sciences, University of Zanjan, Zanjan, Iran. Journal Article 2020 09 19 Abstract In this paper, the biological evolution of the carbonate platform of the Taleh Zang Formation with Paleocene age in the Kermanshah region has been investigated in two stages (time interval) concentrating on fossil debris (such as algae, corals, and benthic foraminifera). For this purpose, two suitable stratigraphic of this formation in the south (Kaboutar Bala section) and southwest (Barikeh section) of Kermanshah were selected, sampled, and studied. For a broader view, the results of this study have been compared with other parts of Tethys basin around the world. The depositional environment of the studied deposits of the Taleh Zang Formation is a carbonate ramp and is probably a form a low gradient ramp due to underdeveloped coral constructions. The gradient of this platform increases from the northwest (Barikeh section) to the southwest (Kaboutar Bala section). Four biofacies were recognized in the studied successions, which include green algae, coral, green algae and benthic foraminifera as well as benthic foraminifera and green algal biofacies. In the lower parts of the Taleh Zang Formation, the presence of algal and coral biofacies (patch reefs) indicates the first stage of carbonate biological evolution of this formation, in that such biofacies has been identified in the Paleocene sequences of other Tethys sectors. Throughout the time and in the upper parts of the Taleh Zang Formation, corals have disappeared and the abundance of green algae is greatly reduced. By the presence of benthic foraminifera with low amounts of green algae, the second stage of the biological evolution of the carbonate platform of the Taleh Zang Formation in the Kermanshah region is formed. In the Early Eocene in Kermanshah region and in the studied successions, due to the seawater regression, the production of carbonates in the Taleh Zang Formation stopped and the detrital red sediments of the Kashkan Formation replaced the carbonates of the Taleh Zang Formation. However, the carbonate production of this formation continued in other areas of the Zagros sedimentary basin (Lorestan province) until the Middle Eocene. Keywords: Biofacies, Carbonate platform biological evolution, Taleh Zang Formation, Paleocene, Kermanshah. Introduction During the Early Paleogene (Paleocene to Eocene), the major carbonate producers were algae, corals, and benthic foraminifera. At the end of the Early Paleogene due to the warming events such as the Paleocene–Eocene Thermal Maximum (PETM), the increase in temperatures in the oceans and CO2 in the atmosphere led to the decline of corals and the expansion of benthic foraminifera (Bernaola et al. 2007; Zamagni et al. 2012; Zhang et al. 2018, 2020). At this time, larger benthic foraminifera, which could tolerate higher temperatures, progressively became one of the main carbonate producers (Pujalte et al. 2003; Scheibner and Speijer 2008). During the Paleocene–Eocene, three biological evolutionary stages could be identified and separated in the carbonate platforms around the world (Scheibner and Speijer 2008; Zamagni et al. 2012; Martin et al. 2020). In stage one, Late Paleocene coralgal dominated platforms; in stage two, a transitional latest Paleocene platform stage with coralgal reefs dominating at middle palaeolatitudes and larger benthic foraminifera dominated platforms at low palaeolatitudes; and in stage three, Early Eocene larger foraminifera dominated platforms in all latitudes. One of the areas where Paleogene carbonates can be abundantly identified and studied is SW Iran, where during the Paleogene, the Taleh Zang Formation has unique outcrops in Kermanshah and Lorestan provinces. Algae, corals, and benthic foraminifera, which are the main producers of the carbonates, have a significant abundance in the Taleh Zang Formation in the Kermanshah region (Shalalvand 2019; Shalalvand et al. 2019 a). Previous studies on this formation have focused mainly on biostratigraphy in the Lorestan Province (Maghfouri Moghaddam et al. 2008; Rajabi et al. 2013; Shojaei Nejad et al. 2018) and in some cases determining the sedimentary environment (Zohdi and Adabi 2008), none of which mention the existence of algal and coral biofacies. In this study, besides identifying the algae and corals, the possible relationship between the biofacies changes of the Taleh Zang Formation is compared with the biological evolution of the Paleocene–Eocene carbonate platform exposed in other parts of the Tethys Basin. This study makes an attempt to cover an important gap in knowledge at middle latitudes (20° to 30°) located between the northern and southern Tethys platform. Materials and Methods After studying the 1/250000 map of Kermanshah (Braud 1978) and 1/250000 map of Ilam-Kuhdasht (Llewellyn 1974), the areas were survived and the outcrops (Barikeh and Kaboutar Bala outcrop sections) were selected as parts of the Zagros Paleocene deposits. Considering the aim of study, accurate sampling on these two stratigraphic sections was performed systematically at two-meter intervals. Finally, 130 hand specimens from Barikeh and 33 samples from Kaboutar Bala sections were collected for petrographic studies. Articles published by various researchers were used to recognize and study the calcareous algae (Elliott 1968; Deloffre and Radoicic 1978; Barattolo 1998; Genot and Granier 2011; Granier et al. 2013; Sobhi and Ahmed 2015; Bucur et al. 2016; Barani et al. 2017; Granier et al. 2017; Bucur et al. 2018; Barattolo et al. 2019). The identification of corals in this paper was also based on studies of different researchers (Turnsek and Kosir 2004; Bernecker and Weidlich 2005; Zamagni et al. 2012; Baron-Szabo 2018). Besides, the biofacies present in this study were identified based on field observations and compared with standard microfacies introduced by Flugel (2010). Discussion of Results and Conclusion In this paper, four biofacies of green algae, coral, green algae and benthic foraminifera as well as benthic foraminifera and green algae biofacies were identified. The abundant presence of benthic foraminifera and fragments of green algae led to the biofacies being considered as separate biofacies from the latter. According to the identified facies, the Taleh Zang Formation in the Kermanshah region was deposited in a shallow carbonate ramp during Paleocene. At this time, which is the first stage of evolution of the Paleogene carbonate platform, algae and corals are very widespread in the Taleh Zang Formation. In this stage, two separate biofacies have been identified, which include the green algae biofacies and the coral biofacies. These biofacies have also been identified in many Paleocene carbonate deposits of the Tethys Basin (Scheibner and Speijer 2008; Martin et al. 2020). During the Late Paleocene and in the Upper Thanetian, with the extinction of corals and most of the algae, the benthic foraminifera was very widespread. This is another stage (stage two) in the evolution of the carbonate platform of the Taleh Zang Formation. At this stage, two biofacies were identified and separated. These biofacies include the green algae and benthic foraminifera as well as benthic foraminifera and green algae biofacies. During the Early Eocene in Kermanshah region, in contrast to the other areas of the Zagros sedimentary Basin, the carbonate production of the Taleh Zang Formation disappears completely. At this time, Kashkan siliciclastic deposits including conglomerates and sandstones formed in a fluvial sedimentary environment (Rostami et al. 2019). In this paper, the obtained results are compared with other similar Tethyan sectors to build a broader view (Scheibner and Speijer 2008; Zamagni et al. 2012; Martin et al. 2020). The carbonate platforms in the West Carpathians (W-Slovakia), the Pyrenean platform (France and Spain), and the Ionian Isp lands (Greece) are located in mid-latitudes (30°–45° N). In these platforms, the major organisms in the first and second evolutionary stages are composed of coralgal reefs (Accordi et al. 1998; Baceta et al. 2005). In these areas, in the third stage of biological evolution, benthic foraminifera plays an important role, except in the Carpathian Mountains. In the Carpathian region at the end of the Paleocene, the whole reef complex was destroyed and no younger strata were recorded (Kazmer et al. 2003; Bucek and Kohler 2017). Carbonate platforms located in Tunisia, Western Morocco, Sirte Basin (Libya), and Zagros Basin in Kermanshah region with the presence of Taleh Zang Formation, are located at intermediate latitudes (20°–30° N). During the Paleocene, in some carbonate platforms (such as Morocco) of these areas, coral reefs and benthic foraminifera are absent. The absence of corals and benthic foraminifera makes this area different from other areas (Jorry et al. 2006; Scheibner and Speijer 2008; Martin et al. 2020). Carbonate platforms in Oman, Northwest India, and Northwest Somalia are also characterized by low latitudes (0°–20° N). Coral reefs indicate the first stage of evolution of these platforms. In the second evolutionary stage, coral reefs and benthic foraminifera are generally present. In the Early Eocene, the abundant presence of benthic foraminifera in all regions describes the third stage (Carbone et al. 1993; Sarkar 2015; Tomas et al. 2016). Overall, it can be concluded that only two biological evolutionary stages are present in the carbonate platform of the Taleh Zang Formation in the Kermanshah region. The first stage is quite similar to the platforms of the Carpathian, Pyrenean, Ionian Islands, Libya, Northwestern India, and Northwestern Somalia. The second stage of the biological evolution of the Taleh Zang Formation is also comparable to the platforms located in Libya and Oman Abstract In this paper, the biological evolution of the carbonate platform of the Taleh Zang Formation with Paleocene age in the Kermanshah region has been investigated in two stages (time interval) concentrating on fossil debris (such as algae, corals, and benthic foraminifera). For this purpose, two suitable stratigraphic of this formation in the south (Kaboutar Bala section) and southwest (Barikeh section) of Kermanshah were selected, sampled, and studied. For a broader view, the results of this study have been compared with other parts of Tethys basin around the world. The depositional environment of the studied deposits of the Taleh Zang Formation is a carbonate ramp and is probably a form a low gradient ramp due to underdeveloped coral constructions. The gradient of this platform increases from the northwest (Barikeh section) to the southwest (Kaboutar Bala section). Four biofacies were recognized in the studied successions, which include green algae, coral, green algae and benthic foraminifera as well as benthic foraminifera and green algal biofacies. In the lower parts of the Taleh Zang Formation, the presence of algal and coral biofacies (patch reefs) indicates the first stage of carbonate biological evolution of this formation, in that such biofacies has been identified in the Paleocene sequences of other Tethys sectors. Throughout the time and in the upper parts of the Taleh Zang Formation, corals have disappeared and the abundance of green algae is greatly reduced. By the presence of benthic foraminifera with low amounts of green algae, the second stage of the biological evolution of the carbonate platform of the Taleh Zang Formation in the Kermanshah region is formed. In the Early Eocene in Kermanshah region and in the studied successions, due to the seawater regression, the production of carbonates in the Taleh Zang Formation stopped and the detrital red sediments of the Kashkan Formation replaced the carbonates of the Taleh Zang Formation. However, the carbonate production of this formation continued in other areas of the Zagros sedimentary basin (Lorestan province) until the Middle Eocene. Keywords: Biofacies, Carbonate platform biological evolution, Taleh Zang Formation, Paleocene, Kermanshah. Introduction During the Early Paleogene (Paleocene to Eocene), the major carbonate producers were algae, corals, and benthic foraminifera. At the end of the Early Paleogene due to the warming events such as the Paleocene–Eocene Thermal Maximum (PETM), the increase in temperatures in the oceans and CO2 in the atmosphere led to the decline of corals and the expansion of benthic foraminifera (Bernaola et al. 2007; Zamagni et al. 2012; Zhang et al. 2018, 2020). At this time, larger benthic foraminifera, which could tolerate higher temperatures, progressively became one of the main carbonate producers (Pujalte et al. 2003; Scheibner and Speijer 2008). During the Paleocene–Eocene, three biological evolutionary stages could be identified and separated in the carbonate platforms around the world (Scheibner and Speijer 2008; Zamagni et al. 2012; Martin et al. 2020). In stage one, Late Paleocene coralgal dominated platforms; in stage two, a transitional latest Paleocene platform stage with coralgal reefs dominating at middle palaeolatitudes and larger benthic foraminifera dominated platforms at low palaeolatitudes; and in stage three, Early Eocene larger foraminifera dominated platforms in all latitudes. One of the areas where Paleogene carbonates can be abundantly identified and studied is SW Iran, where during the Paleogene, the Taleh Zang Formation has unique outcrops in Kermanshah and Lorestan provinces. Algae, corals, and benthic foraminifera, which are the main producers of the carbonates, have a significant abundance in the Taleh Zang Formation in the Kermanshah region (Shalalvand 2019; Shalalvand et al. 2019 a). Previous studies on this formation have focused mainly on biostratigraphy in the Lorestan Province (Maghfouri Moghaddam et al. 2008; Rajabi et al. 2013; Shojaei Nejad et al. 2018) and in some cases determining the sedimentary environment (Zohdi and Adabi 2008), none of which mention the existence of algal and coral biofacies. In this study, besides identifying the algae and corals, the possible relationship between the biofacies changes of the Taleh Zang Formation is compared with the biological evolution of the Paleocene–Eocene carbonate platform exposed in other parts of the Tethys Basin. This study makes an attempt to cover an important gap in knowledge at middle latitudes (20° to 30°) located between the northern and southern Tethys platform. Materials and Methods After studying the 1/250000 map of Kermanshah (Braud 1978) and 1/250000 map of Ilam-Kuhdasht (Llewellyn 1974), the areas were survived and the outcrops (Barikeh and Kaboutar Bala outcrop sections) were selected as parts of the Zagros Paleocene deposits. Considering the aim of study, accurate sampling on these two stratigraphic sections was performed systematically at two-meter intervals. Finally, 130 hand specimens from Barikeh and 33 samples from Kaboutar Bala sections were collected for petrographic studies. Articles published by various researchers were used to recognize and study the calcareous algae (Elliott 1968; Deloffre and Radoicic 1978; Barattolo 1998; Genot and Granier 2011; Granier et al. 2013; Sobhi and Ahmed 2015; Bucur et al. 2016; Barani et al. 2017; Granier et al. 2017; Bucur et al. 2018; Barattolo et al. 2019). The identification of corals in this paper was also based on studies of different researchers (Turnsek and Kosir 2004; Bernecker and Weidlich 2005; Zamagni et al. 2012; Baron-Szabo 2018). Besides, the biofacies present in this study were identified based on field observations and compared with standard microfacies introduced by Flugel (2010). Discussion of Results and Conclusion In this paper, four biofacies of green algae, coral, green algae and benthic foraminifera as well as benthic foraminifera and green algae biofacies were identified. The abundant presence of benthic foraminifera and fragments of green algae led to the biofacies being considered as separate biofacies from the latter. According to the identified facies, the Taleh Zang Formation in the Kermanshah region was deposited in a shallow carbonate ramp during Paleocene. At this time, which is the first stage of evolution of the Paleogene carbonate platform, algae and corals are very widespread in the Taleh Zang Formation. In this stage, two separate biofacies have been identified, which include the green algae biofacies and the coral biofacies. These biofacies have also been identified in many Paleocene carbonate deposits of the Tethys Basin (Scheibner and Speijer 2008; Martin et al. 2020). During the Late Paleocene and in the Upper Thanetian, with the extinction of corals and most of the algae, the benthic foraminifera was very widespread. This is another stage (stage two) in the evolution of the carbonate platform of the Taleh Zang Formation. At this stage, two biofacies were identified and separated. These biofacies include the green algae and benthic foraminifera as well as benthic foraminifera and green algae biofacies. During the Early Eocene in Kermanshah region, in contrast to the other areas of the Zagros sedimentary Basin, the carbonate production of the Taleh Zang Formation disappears completely. At this time, Kashkan siliciclastic deposits including conglomerates and sandstones formed in a fluvial sedimentary environment (Rostami et al. 2019). In this paper, the obtained results are compared with other similar Tethyan sectors to build a broader view (Scheibner and Speijer 2008; Zamagni et al. 2012; Martin et al. 2020). The carbonate platforms in the West Carpathians (W-Slovakia), the Pyrenean platform (France and Spain), and the Ionian Isp lands (Greece) are located in mid-latitudes (30°–45° N). In these platforms, the major organisms in the first and second evolutionary stages are composed of coralgal reefs (Accordi et al. 1998; Baceta et al. 2005). In these areas, in the third stage of biological evolution, benthic foraminifera plays an important role, except in the Carpathian Mountains. In the Carpathian region at the end of the Paleocene, the whole reef complex was destroyed and no younger strata were recorded (Kazmer et al. 2003; Bucek and Kohler 2017). Carbonate platforms located in Tunisia, Western Morocco, Sirte Basin (Libya), and Zagros Basin in Kermanshah region with the presence of Taleh Zang Formation, are located at intermediate latitudes (20°–30° N). During the Paleocene, in some carbonate platforms (such as Morocco) of these areas, coral reefs and benthic foraminifera are absent. The absence of corals and benthic foraminifera makes this area different from other areas (Jorry et al. 2006; Scheibner and Speijer 2008; Martin et al. 2020). Carbonate platforms in Oman, Northwest India, and Northwest Somalia are also characterized by low latitudes (0°–20° N). Coral reefs indicate the first stage of evolution of these platforms. In the second evolutionary stage, coral reefs and benthic foraminifera are generally present. In the Early Eocene, the abundant presence of benthic foraminifera in all regions describes the third stage (Carbone et al. 1993; Sarkar 2015; Tomas et al. 2016). Overall, it can be concluded that only two biological evolutionary stages are present in the carbonate platform of the Taleh Zang Formation in the Kermanshah region. The first stage is quite similar to the platforms of the Carpathian, Pyrenean, Ionian Islands, Libya, Northwestern India, and Northwestern Somalia. The second stage of the biological evolution of the Taleh Zang Formation is also comparable to the platforms located in Libya and Oman

https://jssr.ui.ac.ir/article_25131_3aa9a825cc4a77bcdcf0ce176a02831d.pdf

University of Isfahan Journal of Stratigraphy and Sedimentology Researches 2008-7888 37 1 2021 03 21 Sequence stratigraphy of the Qom Formation in the Sirjan–Abadeh region Sequence stratigraphy of the Qom Formation in the Sirjan–Abadeh region 67 94 25113 10.22108/jssr.2020.120992.1142 FA Ebrahim Mohammadi Assistant Professor, Department of Ecology, Institute of Science, High Technology and Environmental Science, Graduate University of Advanced Technology, Kerman, Iran Journal Article 2020 01 13 Abstract Sequence stratigraphy of the Qom Formation deposits (in two stratigraphic sections) in the Sirjan–Abadeh region has been studied. This formation in the Sirjan area (Bujan section; with Rupelian–Chattian age and 156 m thickness), consists mainly of medium- to thick-bedded and massive limestones and marls. They are unconformably underlain by the polygenetic conglomerate with indeterminate age, and unconformably overlain by the quaternary alluvium. The Qom Formation outcrops in northern Abadeh (with Rupelian–Chattian age and 85 m thickness) consist mainly of massive and bedded limestones, shales, and conglomerates. They are conformably underlain by the Lower Red Formation and unconformably overlain by the quaternary alluvium. Eleven different microfacies, belonging to open marine (middle ramp), lagoon (inner ramp), beach, and braided streams were recognized. Based on the field investigations, deepening and shallowing patterns in microfacies, stacking patterns, and the distribution of foraminifers, four third-order depositional sequences in the Bujan section and five third-order depositional sequences in the Abadeh section have been identified. These depositional sequences are bounded by both type 1 and 2 sequence boundaries. Sequence boundaries are mainly characterized by the abrupt change in lithology and biotic components. Keywords: Qom Formation, Rupelian–Chattian, Sequence stratigraphy, Ramp. Introduction The Qom Formation, Rupelian–Burdigalian in age (Mohammadi et al. 2013, 2015, 2019), was deposited at the northeastern coast of the Tethyan Seaway (Reuter et al. 2009). It consists of thick successions of marine marls, limestones, gypsum, and siliciclastics that were deposited on extensive mixed carbonate-siliciclastic ramps (Reuter et al. 2009), in the Sanandaj–Sirjan fore-arc basin, Urumieh-Dokhtar Magmatic Arc (Intra-arc basin), and Central Iran back-arc basin (Mohammadi et al. 2013, 2015, 2019, Mohammadi and Ameri 2015). The Qom Formation is the main reservoir and source rock for hydrocarbons in middle Iran (Abaie et al. 1964; Rezaei et al. 2000; Mohammadi et al. 2019). This formation is isochronous with the Asmari Formation in the Zagros Basin in southern and southwestern Iran, which is a well-known fractured reservoir that contains 12% of the world's oil (Xu et al. 2007). Although geological investigations on the Qom Formation started more than 160 years ago (Loftus 1855), surprisingly little information is available concerning the sequence stratigraphy of the Qom Formation. Besides, most of the previous works are limited to one stratigraphic section. The aim of this study is, therefore to bridge this gap by studying two stratigraphic sections in the Sirjan–Abadeh region. The stratigraphic sections are located in the Sanandaj–Sirjan fore-arc basin. Material & Methods Bujan and northern Abadeh sections of the Qom Formation in the Sirjan–Abadeh region were studied bed by bed to analyze their sequence stratigraphic framework. A total of 99 and 55 samples were collected (based on field evidence and lithofacies changes) from the Bujan and northern Abadeh sections, respectively. Softer samples were disaggregated and the foraminifera and ostracoda picked and analyzed, while thin sections were prepared from harder samples. All samples were studied in detail and particular attention was paid to main allochems such as foraminifera, corals, corallinacean algae, bryozoans, and ostracoda. The biostratigraphy of the Bujan and northern Abadeh stratigraphic sections are discussed in detail in Mohammadi et al. (2014) and Mohammadi and Ameri (2015), respectively. Likewise, the facies of the Bujan and northern Abadeh stratigraphic sections are analyzed in detail in Mohammadi et al. (2014) and Mohammadi and Ameri (2018), respectively. The facies were investigated by Mohammadi (2020b) to interpret the palaeoenviornment and depositional model. The sequence stratigraphy analysis is based on the model presented by Hunt and Tucker (1992, 1995), Emery and Myers (1996), Hardenbol et al. (1998), Catuneanu (2000, 2006), Simmons et al.(2007), and Catuneanu et al. (2009, 2010, 2011). Discussion of Results & Conclusions Eleven different microfacies/lithofacies, belonging to open marine (middle ramp), lagoon (inner ramp), beach, and braided streams were recognized in the Qom Formation of the two stratigraphic sections from the Sirjan–Abadeh region. The recognized microfacies/lithofacies are as follows: Perforate foraminiferal wack-/packstone, coralline perforate foraminiferal packstone, bioclastic bryozoan corallinacea coral pack-/grainstone, coral boundstone, sandy bioclast wack-/pack-/grainstone, perforate and imperforate foraminiferal bioclast wack-/pack-/grainstone, bioclastic imperforate foraminiferal wack-/packstone, Marl with porcelaneous foraminifera, red shale, muddy sandstone, matrix-supported conglomerate. The latter was deposited within continental braided streams. Four third-order depositional sequences in the Bujan section and five third-order depositional sequences in the Abadeh section have been identified. These depositional sequences are bounded by both type 1 and 2 sequence boundaries. In the Bujan section, only the transgressive systems tracts and the highstand systems tracts were recognized, while in the Abadeh section, the lowstand systems tracts were also identified (in two third-order depositional sequences). Maximum flooding surfaces were coincident with deepening and shallowing in each depositional sequence. Comparison of the relative sea-level curves in the study sections with global sea-level curve of Haq et al. (1988) shows a reasonable correlation around Rupelian–Chattian boundary. However, remaining relative sea-level curve changes probably were related to local factors such as the tectonic and sediment supply in the study area. Abstract Sequence stratigraphy of the Qom Formation deposits (in two stratigraphic sections) in the Sirjan–Abadeh region has been studied. This formation in the Sirjan area (Bujan section; with Rupelian–Chattian age and 156 m thickness), consists mainly of medium- to thick-bedded and massive limestones and marls. They are unconformably underlain by the polygenetic conglomerate with indeterminate age, and unconformably overlain by the quaternary alluvium. The Qom Formation outcrops in northern Abadeh (with Rupelian–Chattian age and 85 m thickness) consist mainly of massive and bedded limestones, shales, and conglomerates. They are conformably underlain by the Lower Red Formation and unconformably overlain by the quaternary alluvium. Eleven different microfacies, belonging to open marine (middle ramp), lagoon (inner ramp), beach, and braided streams were recognized. Based on the field investigations, deepening and shallowing patterns in microfacies, stacking patterns, and the distribution of foraminifers, four third-order depositional sequences in the Bujan section and five third-order depositional sequences in the Abadeh section have been identified. These depositional sequences are bounded by both type 1 and 2 sequence boundaries. Sequence boundaries are mainly characterized by the abrupt change in lithology and biotic components. Keywords: Qom Formation, Rupelian–Chattian, Sequence stratigraphy, Ramp. Introduction The Qom Formation, Rupelian–Burdigalian in age (Mohammadi et al. 2013, 2015, 2019), was deposited at the northeastern coast of the Tethyan Seaway (Reuter et al. 2009). It consists of thick successions of marine marls, limestones, gypsum, and siliciclastics that were deposited on extensive mixed carbonate-siliciclastic ramps (Reuter et al. 2009), in the Sanandaj–Sirjan fore-arc basin, Urumieh-Dokhtar Magmatic Arc (Intra-arc basin), and Central Iran back-arc basin (Mohammadi et al. 2013, 2015, 2019, Mohammadi and Ameri 2015). The Qom Formation is the main reservoir and source rock for hydrocarbons in middle Iran (Abaie et al. 1964; Rezaei et al. 2000; Mohammadi et al. 2019). This formation is isochronous with the Asmari Formation in the Zagros Basin in southern and southwestern Iran, which is a well-known fractured reservoir that contains 12% of the world's oil (Xu et al. 2007). Although geological investigations on the Qom Formation started more than 160 years ago (Loftus 1855), surprisingly little information is available concerning the sequence stratigraphy of the Qom Formation. Besides, most of the previous works are limited to one stratigraphic section. The aim of this study is, therefore to bridge this gap by studying two stratigraphic sections in the Sirjan–Abadeh region. The stratigraphic sections are located in the Sanandaj–Sirjan fore-arc basin. Material & Methods Bujan and northern Abadeh sections of the Qom Formation in the Sirjan–Abadeh region were studied bed by bed to analyze their sequence stratigraphic framework. A total of 99 and 55 samples were collected (based on field evidence and lithofacies changes) from the Bujan and northern Abadeh sections, respectively. Softer samples were disaggregated and the foraminifera and ostracoda picked and analyzed, while thin sections were prepared from harder samples. All samples were studied in detail and particular attention was paid to main allochems such as foraminifera, corals, corallinacean algae, bryozoans, and ostracoda. The biostratigraphy of the Bujan and northern Abadeh stratigraphic sections are discussed in detail in Mohammadi et al. (2014) and Mohammadi and Ameri (2015), respectively. Likewise, the facies of the Bujan and northern Abadeh stratigraphic sections are analyzed in detail in Mohammadi et al. (2014) and Mohammadi and Ameri (2018), respectively. The facies were investigated by Mohammadi (2020b) to interpret the palaeoenviornment and depositional model. The sequence stratigraphy analysis is based on the model presented by Hunt and Tucker (1992, 1995), Emery and Myers (1996), Hardenbol et al. (1998), Catuneanu (2000, 2006), Simmons et al.(2007), and Catuneanu et al. (2009, 2010, 2011). Discussion of Results & Conclusions Eleven different microfacies/lithofacies, belonging to open marine (middle ramp), lagoon (inner ramp), beach, and braided streams were recognized in the Qom Formation of the two stratigraphic sections from the Sirjan–Abadeh region. The recognized microfacies/lithofacies are as follows: Perforate foraminiferal wack-/packstone, coralline perforate foraminiferal packstone, bioclastic bryozoan corallinacea coral pack-/grainstone, coral boundstone, sandy bioclast wack-/pack-/grainstone, perforate and imperforate foraminiferal bioclast wack-/pack-/grainstone, bioclastic imperforate foraminiferal wack-/packstone, Marl with porcelaneous foraminifera, red shale, muddy sandstone, matrix-supported conglomerate. The latter was deposited within continental braided streams. Four third-order depositional sequences in the Bujan section and five third-order depositional sequences in the Abadeh section have been identified. These depositional sequences are bounded by both type 1 and 2 sequence boundaries. In the Bujan section, only the transgressive systems tracts and the highstand systems tracts were recognized, while in the Abadeh section, the lowstand systems tracts were also identified (in two third-order depositional sequences). Maximum flooding surfaces were coincident with deepening and shallowing in each depositional sequence. Comparison of the relative sea-level curves in the study sections with global sea-level curve of Haq et al. (1988) shows a reasonable correlation around Rupelian–Chattian boundary. However, remaining relative sea-level curve changes probably were related to local factors such as the tectonic and sediment supply in the study area.

https://jssr.ui.ac.ir/article_25113_5fbf6084df5d93fa02b72e32529a220c.pdf

University of Isfahan Journal of Stratigraphy and Sedimentology Researches 2008-7888 37 1 2021 03 21 Biostratigraphy, microfacies analysis and depositional environment of the Bartonian–Priabonian limestones in Shan-Abad anticline (west of Rafsanjan) Biostratigraphy, microfacies analysis and depositional environment of the Bartonian–Priabonian limestones in Shan-Abad anticline (west of Rafsanjan) 95 126 25130 10.22108/jssr.2020.124521.1177 FA Tayebeh Ahmadi Assistant Professor, Department of Geology, Payame Noor University (PNU), Tehran, Iran Journal Article 2020 08 31 Abstract The Middle–Late Eocene carbonate deposits have developed in the Shan-Abad anticline as a thin belt among volcanic rocks. The nummulite banks are one of the most interesting deposits in this belt and composed of nummulite accumulations in the form of small, low-relief build-ups. Investigating three outcrops of these deposits were carried out at the eastern flank of Shan-Abad anticline in the present study. A high diversity of larger benthic foraminifera (LBF) and a small number of planktonic foraminifera are recognized, and the sedimentary environment is reconstructed.Based on LBF, three Tethyan foraminiferal biozones (SBZ 17–SBZ 19) spanning the Middle to Late Eocene interval are identified. The textural analysis and faunal assemblages reveal eleven microfacies types. These microfacies types (MFT) are deposited on a carbonate ramp model from tidal to open marine settings. Analysis of the Bartonian–Priabonian deposits based on facies distribution and paleoecology of the biotic components suggest deposition in the inner, middle and proximal outer ramp settings. The inner ramp includes proximal and distal parts. The proximal part of inner ramp is characterized by tidal flat, lagoon, and shoal belts. The distal part of inner ramp includes the nummulite banks. The open marine microfacies were deposited in mid to proximal outer ramp settings. Keywords:Bartonian, Priabonian, Microfacies, Foraminifera, Nummulite accumulations, Rafsanjan. Introduction During the Paleogene, LBFs formed the most common foraminifera groups in shallow marine sediments of different parts of the Tethyan region. Among them, the genus Nummulites hasa unique potential for the rock-forming. The Eocene nummulite banks are widespread along the Tethyan margins and make significant hydrocarbon reservoirs in many places, such as Tunisia (Racey et al. 2001) and Libya (Anketell and Mriheel 2000). In the last few decades, valuable LBF biostratigraphic schemes were conducted by Schaub (1981), Papazzoni and Sirotti (1995), and Serra-Kiel et al. (1998), especially in western Tethys. In Iran, the first comprehensive studies of Eocene LBF were done by Bozorgnia and Kalantari (1965), Rahaghi (1978, 1980, 1983) and Rahaghi and Schaub (1976) and continued by other researchers (e.g., Mosaddegh et al. 2017, Hadi and Vahidinia 2019 and Hadi et al. 2019 a, b). In western Rafsanjan city (Kerman Province, southeastern Iran), the Eocene successions were dominated by volcanic rocks, while sedimentary outcrops and nummulite accumulations of the Eocene deposits are scarce. Despite poor distribution, they are rich in LBFs, which led to the preparation of an excellent tool for paleontological and paleoenvironmental investigations. This study presents the biozonation, microfacies, and depositional environment of the Eocene successions in the Shan-Abad anticline (western Rafsanjan). Material & Methods For this study, three stratigraphic sections on the Eastern flank of Shan-Abad anticline were measured in the field, and their lithologies and sedimentary patterns were described. Shan-Abad 1 and 2 are located 20 km west of the city of Rafsanjan (close to Shan-Abad village) with a thickness of 19.2 m and 18 m, respectively. The Deh-Zahir section is 27.8 m thick is located near Deh-Zahir village (about 8 km south of the Shan-Abad sections). Over 70 samples were collected for the microfacies and micropaleontological analysis. LBF assemblages were investigated in thin sections in order to determine the age of the deposits, applying the Shallow Benthic Zones (SBZs) of Sera-Kiel et al. (1998). A total of 11 MFTs have been defined based on LBF assemblages and sedimentary textures. The textural classification follows the classifications of Embry and Klovan (1971) and Dunham (1962). For the microfacies analysis, the methods of Wilson (1975) and Flügel (2010) were followed. Discussion of Results & Conclusions The Middle–Late Eocene shallow marine successions of the Shan-Abad anticline in Rafsanjan contain stratigraphically important LBFs, which have been used for biostratigraphy and microfacies analysis. Three shallow-water Tethyan foraminiferal biozones (SBZ17–SBZ19) of Middle–Late Eocene are recognized. These biozones are recognized based on one or more fundamental biostratigraphic markers and their first and last occurrences. The co-occurrence of Nummulites incrassatus, N. ptukhiani, N. striatus, N. perforatus, N. cf. N. lyelli, N. malatyensis, Alveolina nuttalli, and A. fusiformis are considered to indicate an Early Bartonian (SBZ17) age. In the Deh-Zahir section, these species are accompanied by Morozovelloides coronatus and M. crassatus, showing this interval is comparable with the E12 biozone of Wade Biozonation (Wade et al.2011). The SBZ18 (Late Bartonian) is marked by the first appearance of Pellatispira madraszi, N. chavannesi, Heterostegina cf. reticulata tronensis, and Nummulites aff. biedai. These species are reported from the Late Middle Eocene from various parts of Tethyan regions such as Italy, Turkey, Armenia and India (Eames 1952; Cole 1970; Jones 1961; Banerji 1981; Serra-Kiel et al. 1998; Bassi 1998; Less et al. 2008; Özcan et al. 2010; Matsumaru and Sarma 2010; Less and Özcan 2012; Cotton et al. 2016). The SBZ 19 is defined by the first appearance of Nummulites aff. fabianii, which appears within SBZ 19 and ranges to SBZ 20. It has been documented from the Late Eocene (Priabonian) of many Tethyan and Indo–pacific regions such as Italy, Turkey, Libya, Pakistan, India and Tanzania (AbdulSamad 2000; Matsumaru and Sarma 2010; Cotton and Pearson 2011; Less et al. 2011; Less and Özcan 2012, Bukhari et al. 2016, Babar et al. 2018). Based on the lithological characteristics, sedimentary texture, and biological content of the studied successions, 11 MFTs were recognized from tidal to open marine belts. From the shoreline towards the sea, they are as follow: 1. Tidal flat microfacies belt: The MFTs of this microfacies belt are bioclastic microconglomerate (MFT1), lithoclastic dolomudstone (MFT2), lithoclast foraminifera bioclast wackestone (MFT3). 2. Lagoon microfacies belt: The bioclast perforate and imperforate foraminifera wackestone/packstone was deposited in lagoon environments. 3. Shoal microfacies belt: The imperforate foraminifera peloidal grainstone (MFT5), bivalve rudstone/floatstone (MFT6) and foraminifera bioclast lithoclast intraclast grainstone (MFT7) were deposited in high-energy shoal environments. 4. Nummulite bank microfacies belt: The MFTs of this microfacies belt include nummulithoclastic packstone and Nummulites rudstone/floatstone/packstone that contain high accumulations of Nummulites. 5. Open marine microfacies belt: Perforate foraminifera bioclast packstone/wackestone and nummulitid orthophragminid packstone/wackestone indicate deeper, low-energy and low light environments of this belt. These MFTs are developed on different parts of a carbonate ramp. The tidal flat, lagoon, and shoal MFTs have formed in the proximal inner ramp environments. Distal inner ramp settings are characterized by the nummulite bank microfacies. Open marine MTFs were deposited in the mid, to proximal outer ramp settings. Abstract The Middle–Late Eocene carbonate deposits have developed in the Shan-Abad anticline as a thin belt among volcanic rocks. The nummulite banks are one of the most interesting deposits in this belt and composed of nummulite accumulations in the form of small, low-relief build-ups. Investigating three outcrops of these deposits were carried out at the eastern flank of Shan-Abad anticline in the present study. A high diversity of larger benthic foraminifera (LBF) and a small number of planktonic foraminifera are recognized, and the sedimentary environment is reconstructed.Based on LBF, three Tethyan foraminiferal biozones (SBZ 17–SBZ 19) spanning the Middle to Late Eocene interval are identified. The textural analysis and faunal assemblages reveal eleven microfacies types. These microfacies types (MFT) are deposited on a carbonate ramp model from tidal to open marine settings. Analysis of the Bartonian–Priabonian deposits based on facies distribution and paleoecology of the biotic components suggest deposition in the inner, middle and proximal outer ramp settings. The inner ramp includes proximal and distal parts. The proximal part of inner ramp is characterized by tidal flat, lagoon, and shoal belts. The distal part of inner ramp includes the nummulite banks. The open marine microfacies were deposited in mid to proximal outer ramp settings. Keywords:Bartonian, Priabonian, Microfacies, Foraminifera, Nummulite accumulations, Rafsanjan. Introduction During the Paleogene, LBFs formed the most common foraminifera groups in shallow marine sediments of different parts of the Tethyan region. Among them, the genus Nummulites hasa unique potential for the rock-forming. The Eocene nummulite banks are widespread along the Tethyan margins and make significant hydrocarbon reservoirs in many places, such as Tunisia (Racey et al. 2001) and Libya (Anketell and Mriheel 2000). In the last few decades, valuable LBF biostratigraphic schemes were conducted by Schaub (1981), Papazzoni and Sirotti (1995), and Serra-Kiel et al. (1998), especially in western Tethys. In Iran, the first comprehensive studies of Eocene LBF were done by Bozorgnia and Kalantari (1965), Rahaghi (1978, 1980, 1983) and Rahaghi and Schaub (1976) and continued by other researchers (e.g., Mosaddegh et al. 2017, Hadi and Vahidinia 2019 and Hadi et al. 2019 a, b). In western Rafsanjan city (Kerman Province, southeastern Iran), the Eocene successions were dominated by volcanic rocks, while sedimentary outcrops and nummulite accumulations of the Eocene deposits are scarce. Despite poor distribution, they are rich in LBFs, which led to the preparation of an excellent tool for paleontological and paleoenvironmental investigations. This study presents the biozonation, microfacies, and depositional environment of the Eocene successions in the Shan-Abad anticline (western Rafsanjan). Material & Methods For this study, three stratigraphic sections on the Eastern flank of Shan-Abad anticline were measured in the field, and their lithologies and sedimentary patterns were described. Shan-Abad 1 and 2 are located 20 km west of the city of Rafsanjan (close to Shan-Abad village) with a thickness of 19.2 m and 18 m, respectively. The Deh-Zahir section is 27.8 m thick is located near Deh-Zahir village (about 8 km south of the Shan-Abad sections). Over 70 samples were collected for the microfacies and micropaleontological analysis. LBF assemblages were investigated in thin sections in order to determine the age of the deposits, applying the Shallow Benthic Zones (SBZs) of Sera-Kiel et al. (1998). A total of 11 MFTs have been defined based on LBF assemblages and sedimentary textures. The textural classification follows the classifications of Embry and Klovan (1971) and Dunham (1962). For the microfacies analysis, the methods of Wilson (1975) and Flügel (2010) were followed. Discussion of Results & Conclusions The Middle–Late Eocene shallow marine successions of the Shan-Abad anticline in Rafsanjan contain stratigraphically important LBFs, which have been used for biostratigraphy and microfacies analysis. Three shallow-water Tethyan foraminiferal biozones (SBZ17–SBZ19) of Middle–Late Eocene are recognized. These biozones are recognized based on one or more fundamental biostratigraphic markers and their first and last occurrences. The co-occurrence of Nummulites incrassatus, N. ptukhiani, N. striatus, N. perforatus, N. cf. N. lyelli, N. malatyensis, Alveolina nuttalli, and A. fusiformis are considered to indicate an Early Bartonian (SBZ17) age. In the Deh-Zahir section, these species are accompanied by Morozovelloides coronatus and M. crassatus, showing this interval is comparable with the E12 biozone of Wade Biozonation (Wade et al.2011). The SBZ18 (Late Bartonian) is marked by the first appearance of Pellatispira madraszi, N. chavannesi, Heterostegina cf. reticulata tronensis, and Nummulites aff. biedai. These species are reported from the Late Middle Eocene from various parts of Tethyan regions such as Italy, Turkey, Armenia and India (Eames 1952; Cole 1970; Jones 1961; Banerji 1981; Serra-Kiel et al. 1998; Bassi 1998; Less et al. 2008; Özcan et al. 2010; Matsumaru and Sarma 2010; Less and Özcan 2012; Cotton et al. 2016). The SBZ 19 is defined by the first appearance of Nummulites aff. fabianii, which appears within SBZ 19 and ranges to SBZ 20. It has been documented from the Late Eocene (Priabonian) of many Tethyan and Indo–pacific regions such as Italy, Turkey, Libya, Pakistan, India and Tanzania (AbdulSamad 2000; Matsumaru and Sarma 2010; Cotton and Pearson 2011; Less et al. 2011; Less and Özcan 2012, Bukhari et al. 2016, Babar et al. 2018). Based on the lithological characteristics, sedimentary texture, and biological content of the studied successions, 11 MFTs were recognized from tidal to open marine belts. From the shoreline towards the sea, they are as follow: 1. Tidal flat microfacies belt: The MFTs of this microfacies belt are bioclastic microconglomerate (MFT1), lithoclastic dolomudstone (MFT2), lithoclast foraminifera bioclast wackestone (MFT3). 2. Lagoon microfacies belt: The bioclast perforate and imperforate foraminifera wackestone/packstone was deposited in lagoon environments. 3. Shoal microfacies belt: The imperforate foraminifera peloidal grainstone (MFT5), bivalve rudstone/floatstone (MFT6) and foraminifera bioclast lithoclast intraclast grainstone (MFT7) were deposited in high-energy shoal environments. 4. Nummulite bank microfacies belt: The MFTs of this microfacies belt include nummulithoclastic packstone and Nummulites rudstone/floatstone/packstone that contain high accumulations of Nummulites. 5. Open marine microfacies belt: Perforate foraminifera bioclast packstone/wackestone and nummulitid orthophragminid packstone/wackestone indicate deeper, low-energy and low light environments of this belt. These MFTs are developed on different parts of a carbonate ramp. The tidal flat, lagoon, and shoal MFTs have formed in the proximal inner ramp environments. Distal inner ramp settings are characterized by the nummulite bank microfacies. Open marine MTFs were deposited in the mid, to proximal outer ramp settings.

https://jssr.ui.ac.ir/article_25130_1cd07f1b8f923783c7be51911531732f.pdf

University of Isfahan Journal of Stratigraphy and Sedimentology Researches 2008-7888 37 1 2021 03 21 Biostratigraphy of the Cretaceous deposits based on ammonites in the southwest of Qayen area (Qumenjan section) Biostratigraphy of the Cretaceous deposits based on ammonites in the southwest of Qayen area (Qumenjan section) 127 146 25121 10.22108/jssr.2020.122202.1155 FA Seyed Naser Raisossadat Academic staff- Professor, Geology Dept., Faculty of Sciences, University of Birjand, Birjand, Iran, Abdolmajid Mosavinia Associate Professor, Geology Department, Payame Noor University, Box 19395-3697, Iran Ahmadreza Khazaei Associate Professor, Geology Department, Faculty of Sciences, University of Birjand, Birjand, Iran Shahram Asadi MSc in Stratigraphy and Paleontology, Geology Department, Payame Noor University of Birjand, Iran Journal Article 2020 04 06 Abstract Ammonite biostratigraphy could be used in age determination and correlation of rock units in different sedimentary basins. Qumenjan section with 125 meters thickness is mainly formed by grey sandy limestone with grey and thick-bedded limestone intercalations. The study area is located in the eastern margin of the Lut Block. For a stratigraphical study of Lower–Upper Cretaceous deposits in southwestern of Qayen area, a stratigraphic section was selected and measured. Eight ammonites, including Anisoceras, Calycoceras, Hypoturrilites, Hysteroceras, Mantelliceras, Puzosia, and Scaphites genera and thirteen representative species were identified. Based on the identified assemblage fossils and comparison with international biozones, Hysteroceras orbignyi subzone for Late Albian age, Mantelliceras mantelli biozone for the lower part of Early Cenomanian age, Mantelliceras dixoni biozone for the upper part of Early Cenomanian age, and Turrilites costatus biozone for Middle Cenomanian age is suggested. According to identified genera and species a Late Albian–Middle Cenomanian age is assigned for ammonite bearing of the section. The first occurrence of Mantelliceras mantelli is taken as the base of Cenomanian. Compression of the identified ammonites with other basins shows that the east Iran basin was a part of Tethys Realm during late Albian–middle Cenomanian. Keywords:Biostratigraphy, Ammonite, Albian, Cenomanian, Qayen, East Iran. Introduction Ammonites are one of the best macrofossils for Cretaceous biostratigraphy. The Albian and Cenomanian ammonites of Kopet Dagh and Central Iran have been studied by numerous researchers such as Seyed-Emami and Aryai (1981), Seyed-Emami (1977), Seyed-Emami, (1982), Seyed-Emami et al. (1984), Immel and Seyed-Emami (1985), Seyed-Emami and Immel (1995, 1996), Immel et al. (1997), Mosavinia et al. (2007), Mosavinia and Wilmsen (2011), Mosavinia et al. (2014), and Wilmsen et al. (2015). The Cretaceous deposits have spread in the east of Iran and in Birjand and Qayen area. These deposits have different facies. The Cretaceous rocks include conglomerate and sandstone units in the base and then changed to limestones in Late Barremain to Aptian. During Albian–Cenomanian, the depth of the sedimentary basin increased and thin-bedded limestones, marly limestones, and marls were deposited. The Lower Cretaceous succession is composed of different rock units that are outcropped in the eastern margin of Lut Block. These deposits usually start with a basal conglomerate. “Orbitolinind Limestone” is an informal name that is used for a succession containing Orbitolina limestone and marl intercalations. Aptian–Cenomanian succession mostly is composed of detrital, marl, and carbonate beds most of which are biogenic sediments deposited in carbonate platforms. Upper Cretaceous deposits are mostly widespread in Maastrichtian (Stocklin et al. 1972; Fauvelet and Eftekharnezhad 1990). Flyschiod facies are also spread with Ophiolites in Upper Cretaceous (Aghanabati2004). One of the oldest studies conducted in the east of Iran is published by Clap (1940). Several geological and paleontological studies have been done by several researchers such as Stocklin et al. (1972), Tirrul et al. (1983), Fauvelet and Eftekharnezhad (1990), Berthiaux et al. (1991), Raisossadat and Skelton (2005), Babazadeh et al. (2010), Khazaei et al. (2011), Raisossadat et al. (2016), Sharifi et al. (2016), Motamedalshariati et al. (2016), Raisossadat and Noori (2016), Latifi et al. (2018), Raisossadat et al. (2017) and Zarei et al. (2019). Despite the above-mentioned studies , there still seems the need to do more studies in paleontological fields. Ammonites are known as useful fossil groups in age determination and are used as biostratigraphical and biozonation tool for the Cretaceous deposits. The aim of this study is to provide an ammonite biozonation and a short palaeobiogeographic discussion on the Cretaceous deposits of the study area. Material & Methods Based on the geological map and field observation, a stratigraphical section was selected and measured in the southwest of Qayen and in south of the Qumenjan Village. The geographical coordinates of the base of the section are 58° 52' 11" E 33° 32' 19" N. Sixteen rock and ammonite samples were collected. Ammonites were cleaned, covered with magnesium vapor and photographed. Collected specimens were identified. The collected samples were stored in the Department of Geology, University of Birjand. Discussion of Results & Conclusion The Qumenjan section with 125 meters thickness starts with a conglomerated bed at the base, and then continues with sandy limestones. The major part including a succession of grey limestone and argillaceous limestone intercalations. In this study, the following ammonites are identified: Anisoceras plicatile, Calycoceras gentoni, Calycoceras (Newboldiceras) asiaticum, Calycoceras sp., Hypoturrilites sp ., Hysteroceras orbignyi, Mantelliceras dixoni, Mantelliceras saxbii, Mantelliceras mantelli, Mantelliceras cf. lymense, Puzosia (P.) sp., Scaphites sp. Based on reported microfauna (Ahrari 2009; Moloudi 2014) and identified ammonites a Late Aptian to Middle Cenomanian age is suggested for the section. Based on the identified ammonites, the following biozones is suggested for the studied section: Hysteroceras orbignyi subzone: this subzone is introduced as an index subzone for the Late Albian. Range of this zone is from the first occurrence of Hysteroceras orbignyi to the first occurrence of Mantelliceras mantelli. The associate ammonite is Puzosia sp. The thickness of this subzone is 25 meters. Mantelliceras mantelli Interval Zone: This zone is reported from south of the UK, France, Spain, and Portugal and south of Africa. Mantelliceras mantelli is discussed as index zone of Early Cenomanian. The range of this zone is from the first occurrence of Mantelliceras mantelli to the first occurrence of Mantelliceras dixoni. The associate ammonites are Hyphoplites cf. costosus, Hypoturrilites cf. gravesianus, Scaphites sp. The thickness of this subzone is 19 meters. Mantelliceras dixoni Interval Zone: This zone is an index zone for lower part of Middle Cenomanian. However, this zone could confirm Middle Cenomanian. The range of this zone is from the first occurrence of Mantelliceras dixoni to the first occurrence of Turrilites costatus. The associate ammonite is Mantelliceras cf. lymense. The thickness of this subzone is 14 meters. Turrilites costatus Interval Zone: This zone is introduced by Hancock (1991). Alabushev (1995) introduced it as a subzone. Wilmsen et al. (2007) mentioned Anisoceras plicatile and Turrilites costatus as index fossils for Acanthoceras rhotomagense Zone. Kennedy and Gale (2015) reported Calycoceras gentoni from Middle Cenomanian. Acanthoceras rhotomagense is reported as the index zone of Middle Cenomanian. In the studied section A. rhotomagense has not been reported. Therefore, based on the occurrence of Turrilites aff. costatus Zone, Middle Cenomanian age is suggested for the upper part of the section. The associate assemblages include Calycoceras (Newboldiceras) asiaticum, Calycoceras gentoni, Anisoceras plicatile and Calycoceras sp. Latitudinal and provincial control of ammonite faunas was common throughout the Mesozoic. Both the ranks (realm, province, etc.) and names have varied from author to author. Tectonic movements and sea-level changes (regressions and transgressions) caused seaways connecting basins to open marine or close and led to several distinct new basins or limitation of seaways and between marine basins. Thus, numerous sub-realms and provinces have been named. Three biogeographic realms existed during the Mesozoic; Boreal Realm embraced the Arctic basins and the seas extending southward from there over parts of North America, Northern Europe, and Siberia. The Boreal seas were largely landlocked but linked by narrow seaways to the Tethyan Realm. The Tethyan Realm includes low latitude areas such as Africa, the Pacific, the Middle East, and America, and centered on the Paleo-Tethys Ocean. An Austral Realm has also been proposed for high southerly latitudes (Stevens 1973). To study the palaeobiogeographic conditions of Upper Albian–Lower Cenomanian in eastern Iran, the ammonite fauna of the studied section was compared with other reported ammonites from different areas. The reported ammonites from east of Iran show affinity with those reported from Kopet Dagh, Central Iran, Europe, and USA. The absence of Scholenbachia that is an index genus of the Boreal Realm and the presence of some genera such as Anisoceras, Scaphites, Hypoturrilites, and Puzosia could suggest that the study area is a part of Tethys Realm. However, the presence of Mantelliceras could show the effects of the influence of Boreal. The analysis of the ammonite stratigraphic distribution in the selected section in east of Iran allowed us to establish the faunal succession for the Upper Albian–Middle Cenomanian in the region. Based on identified assemblage, the following biozones are suggested. Hysetroceras orbignyi subzone is suggested as index zone of Late Albian, Mantelliceras mantelli Zone could confirm lower part of Early Cenomanian, Mantelliceras dixoni Zone is known as the upper part of Early Cenomanian and Turrilites costatus Zone is suggested as Middle Cenomanian. Compression of the identified ammonites with other basins shows that the east Iran basin was a part of Tethys Realm during Late Albian–Middle Cenomanian. Abstract Ammonite biostratigraphy could be used in age determination and correlation of rock units in different sedimentary basins. Qumenjan section with 125 meters thickness is mainly formed by grey sandy limestone with grey and thick-bedded limestone intercalations. The study area is located in the eastern margin of the Lut Block. For a stratigraphical study of Lower–Upper Cretaceous deposits in southwestern of Qayen area, a stratigraphic section was selected and measured. Eight ammonites, including Anisoceras, Calycoceras, Hypoturrilites, Hysteroceras, Mantelliceras, Puzosia, and Scaphites genera and thirteen representative species were identified. Based on the identified assemblage fossils and comparison with international biozones, Hysteroceras orbignyi subzone for Late Albian age, Mantelliceras mantelli biozone for the lower part of Early Cenomanian age, Mantelliceras dixoni biozone for the upper part of Early Cenomanian age, and Turrilites costatus biozone for Middle Cenomanian age is suggested. According to identified genera and species a Late Albian–Middle Cenomanian age is assigned for ammonite bearing of the section. The first occurrence of Mantelliceras mantelli is taken as the base of Cenomanian. Compression of the identified ammonites with other basins shows that the east Iran basin was a part of Tethys Realm during late Albian–middle Cenomanian. Keywords:Biostratigraphy, Ammonite, Albian, Cenomanian, Qayen, East Iran. Introduction Ammonites are one of the best macrofossils for Cretaceous biostratigraphy. The Albian and Cenomanian ammonites of Kopet Dagh and Central Iran have been studied by numerous researchers such as Seyed-Emami and Aryai (1981), Seyed-Emami (1977), Seyed-Emami, (1982), Seyed-Emami et al. (1984), Immel and Seyed-Emami (1985), Seyed-Emami and Immel (1995, 1996), Immel et al. (1997), Mosavinia et al. (2007), Mosavinia and Wilmsen (2011), Mosavinia et al. (2014), and Wilmsen et al. (2015). The Cretaceous deposits have spread in the east of Iran and in Birjand and Qayen area. These deposits have different facies. The Cretaceous rocks include conglomerate and sandstone units in the base and then changed to limestones in Late Barremain to Aptian. During Albian–Cenomanian, the depth of the sedimentary basin increased and thin-bedded limestones, marly limestones, and marls were deposited. The Lower Cretaceous succession is composed of different rock units that are outcropped in the eastern margin of Lut Block. These deposits usually start with a basal conglomerate. “Orbitolinind Limestone” is an informal name that is used for a succession containing Orbitolina limestone and marl intercalations. Aptian–Cenomanian succession mostly is composed of detrital, marl, and carbonate beds most of which are biogenic sediments deposited in carbonate platforms. Upper Cretaceous deposits are mostly widespread in Maastrichtian (Stocklin et al. 1972; Fauvelet and Eftekharnezhad 1990). Flyschiod facies are also spread with Ophiolites in Upper Cretaceous (Aghanabati2004). One of the oldest studies conducted in the east of Iran is published by Clap (1940). Several geological and paleontological studies have been done by several researchers such as Stocklin et al. (1972), Tirrul et al. (1983), Fauvelet and Eftekharnezhad (1990), Berthiaux et al. (1991), Raisossadat and Skelton (2005), Babazadeh et al. (2010), Khazaei et al. (2011), Raisossadat et al. (2016), Sharifi et al. (2016), Motamedalshariati et al. (2016), Raisossadat and Noori (2016), Latifi et al. (2018), Raisossadat et al. (2017) and Zarei et al. (2019). Despite the above-mentioned studies , there still seems the need to do more studies in paleontological fields. Ammonites are known as useful fossil groups in age determination and are used as biostratigraphical and biozonation tool for the Cretaceous deposits. The aim of this study is to provide an ammonite biozonation and a short palaeobiogeographic discussion on the Cretaceous deposits of the study area. Material & Methods Based on the geological map and field observation, a stratigraphical section was selected and measured in the southwest of Qayen and in south of the Qumenjan Village. The geographical coordinates of the base of the section are 58° 52' 11" E 33° 32' 19" N. Sixteen rock and ammonite samples were collected. Ammonites were cleaned, covered with magnesium vapor and photographed. Collected specimens were identified. The collected samples were stored in the Department of Geology, University of Birjand. Discussion of Results & Conclusion The Qumenjan section with 125 meters thickness starts with a conglomerated bed at the base, and then continues with sandy limestones. The major part including a succession of grey limestone and argillaceous limestone intercalations. In this study, the following ammonites are identified: Anisoceras plicatile, Calycoceras gentoni, Calycoceras (Newboldiceras) asiaticum, Calycoceras sp., Hypoturrilites sp ., Hysteroceras orbignyi, Mantelliceras dixoni, Mantelliceras saxbii, Mantelliceras mantelli, Mantelliceras cf. lymense, Puzosia (P.) sp., Scaphites sp. Based on reported microfauna (Ahrari 2009; Moloudi 2014) and identified ammonites a Late Aptian to Middle Cenomanian age is suggested for the section. Based on the identified ammonites, the following biozones is suggested for the studied section: Hysteroceras orbignyi subzone: this subzone is introduced as an index subzone for the Late Albian. Range of this zone is from the first occurrence of Hysteroceras orbignyi to the first occurrence of Mantelliceras mantelli. The associate ammonite is Puzosia sp. The thickness of this subzone is 25 meters. Mantelliceras mantelli Interval Zone: This zone is reported from south of the UK, France, Spain, and Portugal and south of Africa. Mantelliceras mantelli is discussed as index zone of Early Cenomanian. The range of this zone is from the first occurrence of Mantelliceras mantelli to the first occurrence of Mantelliceras dixoni. The associate ammonites are Hyphoplites cf. costosus, Hypoturrilites cf. gravesianus, Scaphites sp. The thickness of this subzone is 19 meters. Mantelliceras dixoni Interval Zone: This zone is an index zone for lower part of Middle Cenomanian. However, this zone could confirm Middle Cenomanian. The range of this zone is from the first occurrence of Mantelliceras dixoni to the first occurrence of Turrilites costatus. The associate ammonite is Mantelliceras cf. lymense. The thickness of this subzone is 14 meters. Turrilites costatus Interval Zone: This zone is introduced by Hancock (1991). Alabushev (1995) introduced it as a subzone. Wilmsen et al. (2007) mentioned Anisoceras plicatile and Turrilites costatus as index fossils for Acanthoceras rhotomagense Zone. Kennedy and Gale (2015) reported Calycoceras gentoni from Middle Cenomanian. Acanthoceras rhotomagense is reported as the index zone of Middle Cenomanian. In the studied section A. rhotomagense has not been reported. Therefore, based on the occurrence of Turrilites aff. costatus Zone, Middle Cenomanian age is suggested for the upper part of the section. The associate assemblages include Calycoceras (Newboldiceras) asiaticum, Calycoceras gentoni, Anisoceras plicatile and Calycoceras sp. Latitudinal and provincial control of ammonite faunas was common throughout the Mesozoic. Both the ranks (realm, province, etc.) and names have varied from author to author. Tectonic movements and sea-level changes (regressions and transgressions) caused seaways connecting basins to open marine or close and led to several distinct new basins or limitation of seaways and between marine basins. Thus, numerous sub-realms and provinces have been named. Three biogeographic realms existed during the Mesozoic; Boreal Realm embraced the Arctic basins and the seas extending southward from there over parts of North America, Northern Europe, and Siberia. The Boreal seas were largely landlocked but linked by narrow seaways to the Tethyan Realm. The Tethyan Realm includes low latitude areas such as Africa, the Pacific, the Middle East, and America, and centered on the Paleo-Tethys Ocean. An Austral Realm has also been proposed for high southerly latitudes (Stevens 1973). To study the palaeobiogeographic conditions of Upper Albian–Lower Cenomanian in eastern Iran, the ammonite fauna of the studied section was compared with other reported ammonites from different areas. The reported ammonites from east of Iran show affinity with those reported from Kopet Dagh, Central Iran, Europe, and USA. The absence of Scholenbachia that is an index genus of the Boreal Realm and the presence of some genera such as Anisoceras, Scaphites, Hypoturrilites, and Puzosia could suggest that the study area is a part of Tethys Realm. However, the presence of Mantelliceras could show the effects of the influence of Boreal. The analysis of the ammonite stratigraphic distribution in the selected section in east of Iran allowed us to establish the faunal succession for the Upper Albian–Middle Cenomanian in the region. Based on identified assemblage, the following biozones are suggested. Hysetroceras orbignyi subzone is suggested as index zone of Late Albian, Mantelliceras mantelli Zone could confirm lower part of Early Cenomanian, Mantelliceras dixoni Zone is known as the upper part of Early Cenomanian and Turrilites costatus Zone is suggested as Middle Cenomanian. Compression of the identified ammonites with other basins shows that the east Iran basin was a part of Tethys Realm during Late Albian–Middle Cenomanian.

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