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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.

In case of a decrease in reservoir pressure, injection projects are inevitable that the desired production rate is maintained. Moreover, one of the key issues in injection operations is optimum injection pressure determination to prevent fault reactivation . The aim of this study is to evaluate fault reactivation tenacity in one of SW Iranian oil fields at different injection stages. Two main steps in this study are geomechanical modeling and fault extraction. In addition, fullset data, image log, dipole sonic log, and MDT pressure points were used to construct the geomechanical model. Also, 3-D seismic data were used for fault extraction and characterization. Ultimately, according to the geomechanical model, the stress state is strike-slip normal, and the maximum horizontal stress direction is toward NE-SW. Furthermore, 18 faults have been extracted using seismic data, which their strikes are often NW-SE. In addition, the faults are inactive in the present-day stress state, but the first fault will be reactivated with a 33 MPa increase in pore pressure.

Sarvak Formation as the oil reservoir with the most hydrocarbon potential in Yaran oil field is of special importance. The present research was conducted to study the reservoir parameters of this Formation. For this purpose, petro-physical crude data was first prepared and using the Geolog6.7 software, a petro physical plot was drawn. Afterward, petro-physical properties of reservoir were done by modeling and using cross plots and logs, including porosity, permeability, lithology type, shale volume, water saturation and fractures analysis were investigated. Finally, with the adaptation of petro-physical parameters and other geological assessments from drilling cores, reservoir zoning and reservoir quality was analyzed. The obtained results showed that in the studied well there is a depth of 2600 to 2693 m of hydrocarbon potential friends. Effective porosity of the Sarvak Formation varies from 10 to 15%. Moreover, all of the investigated methods present of the prevailing lithology Carbonate, which can be on some outcrops of the shale layers, which has led to a decrease in reservoir quality in other zones.

Middle Albian to Cenomanian strata of the Sarvak Formation indicate pelagic facies in Tang-e-Chenarbashi stratigraphic section. These strata deposited in five sequences of the third order and nine sequences of the fourth order. These sequences were determinated in a succession including six microfacies mudstone, sponge spicule packstone, peloidal packstone, radiolarian packstone, Oligosteginid, planktonic foraminifera wackestone - packstone, benthic foraminifera echinoidal wackestone - packstone. Study of the third order sequences show that in some of them exist paraconformity which related to sequence boundary of the fourth order sequences. Investigating these sequence boundaries and recognition the sequences were done based on planktonic foraminifera biozones. In this study, separating the fourth order sequences is generally based on fossil fauna. In the fourth order sequences, maximum flooding surfaces (mfs) were recognized based on maximum diversity and abundance of planktonic taxa and decreasing of benthic foraminifera. Introduction The Sarvak Formation, one of the four formations of the Bangestan Group in Zagros basin, generally includes two facies, deep facies in the Lurestan province and shallow facies in the Khuzestan and Fars provinces. The Sarvak Formation deposited during Middle Albian to Early Turonian which the two main orogenic phases, Austrian (Albian / Cenomanian) and Sub-Hercynian (Cenomanian / Turonian) occurred. The warmest climate and the highest sea level took place along the Earth history in Albian to Cenomanian, and this could be a good and unique objective to investigation the effects of many interesting phenomena due to the amazing and unrepeated events. In addition, depositions of this time span could be included interesting depositional sequences. The aim of this research is recognition of depositional sequences of the Sarvak sediments by using of fossils. Material and Methods One stratigraphic section with 712 meters thickness was selected for studying of deep facies of the Sarvak Formation in Lurestan province. Totally, 148 thin sections were studied for recognizing microfacies characteristics and paleoenvironment based on Flugel (2010) and Wilson (1975). Study of sequence stratigraphy of the Sarvak Formation in the examined section was carried out based on Hunt and Tucker (1992, 1995) by using microfacies with fossil content. Discussion and conclusion A critical and detail biostratigraphic study with relay on planktonic foraminifera and microfacies is used here is based on Daneshian et al.(2011, 2013). On the basis of the mentioned references, age determination clears to us a Middle Albian to Cenomanian age for the Sarvak Formation in the selected section. Also, 6 microfacies including mudstone, sponge spicule packstone, peloidal packstone, radiolarian packstone, Oligosteginid, planktonic foraminiferal wackestone - packstone, benthic foraminiferal echinoidal wackestone – packstone, were determinated. Study of depositional sequences in the pelagic and hemipelagic sediments is complicated and confusing. In fact, lack of exposures and also similarity and monotonous between the facies constructing the depositional sequences, make it difficult to differentiate systems tracts. Geological field studies do not play a critical role in sequence stratigraphic studies of the Sarvak deposits in Tang-e-chenarbashi section. thus, we focused on microfacies data to find the system tracts. The microfacies show that the strata deposited in five third-order sequences. The problem displayed when we faced to some paraconformity existed in the third order sequences. The paraconformities were recognized by biostratigraphic studies. Since these paraconformities are belong to the fourth order sequences, we persuade to elicit the fourth order sequences for the studied section, but when we know this fact the cause of fourth and lower order sequences is Milankovitch cycles, we should draw our attention to fossils than microfacies. The purpose of this paper is not Cyclostratigraphy but is to clear role of fossils in separating depositional sequences. In this research two functions of fossil data are considered: 1) dating the depositional sequences using global biozones, and 2) investigation of system tracts where microfacies are ineffective tools. In this study the abundance of four main fossil groups including planktonic foraminifera, benthic foraminifera, oligosteginids and echinoid fragments illustrated against lithostratigraphic column, sea level changes and investigated sequences. Many features such as amount of planktonic foraminifera, broken fossil fragments, dramatically the increase or decrease in r-selected or k-selected taxa and many other similar to these, coincide with ts surface or mfs which help us to demonstrate the forth-order depositional sequences. This study tries to establish relation between classic usage of fossils just for age determining and use it as main allochem that is able to reflect many small scale events which tracking them in the deposit is impossible. Generally, five third-order sequences in a succession including six microfacies were recognized. Biostratigraphic data helped us to know the age of depositional sequences to attribute them to correct order with more confidence. Also, on the basis of extracted biozones, some paraconformities have been identified.

Introduction: The Sarvak Formation is mainly composed of limestone and is one of the most important rock reservoirs in the Zagros sedimentary basin. This formation has been studied extensively in many parts of the Zagros; however the information about various aspects of this formation in northern Lorestan is limited. Due to the discovery of a pycnodont fish tooth plate from Aleshtar area, and because of scarce data on Cretaceous deposits in this region, we conducted this research. Material &Methods: In order to study the age, sedimentary environment and sequence stratigraphy of the Sarvak Formation, field and microscopic studies of 100 thin sections from an outcrop near Aleshtar (north of Lorestan) has been carried out. Discussion of Results &Conclusions: The Sarvak Formation in the studied section is Cenomanian in age and is 835 meters thick. It is bounded by Garu and Surgah formations at the base and top respectively. It is mainly composed of thick, medium, and thin bedded limestone rich in chert nodules, bioturbation and rudists. The studied outcrops can be subdivided into four units litho-stratigraphically. The first unit is 200 meters of thick, grey limestone with benthic foraminifera and echinoids. Second unit is 320 meters of mainly grey, medium bedded limestone with reddish intercalation of shale, containing benthic foraminifera, rudist debris and bioturbation. 180 meters of thick bedded, grey limestone with rudist and other bivalve debris forms the third unit. The last litho-stratigraphic unit consists of 135 meters of medium to thin bedded, grey limestone with interlayers of dolomitic limestone and rudist/bivalve debris and bioturbation. Benthic foraminifera are less abundant here. Our study led to the identification of 12 microfacies and 3 facies-belts, which belong to tidal flat, lagoon, and open marine environments. These microfacies are differentiated based on abundance and diversity of skeletal and non skeletal remains and rock texture. These facies, ordered from shallower to deeper environments, include: bioclastic stromatolite wackestone to bindstone, and pisoid rudstone in tidal-flat facies belt; bioclast peloid intraclast grainstone, bioclast green algae wackestone to packstone, peloid ooid grainstone to packstone, bioclast echinoderm benthic foraminifera wackestone, rudist benthic foraminifera wackestone, orbitolina miliolid wackestone to packstone, bioclast miliolid wackestone, and benthic foraminifera rudist floatstone to rudstone in lagoon facies belt; and rudist floatstone to rudstone, and bioclast oligosteginid wackestone within open marine facies belt. According to type and gradual changes of microfacies in lower parts of the Sarvak Formation, and compared to abrupt changes of microfacies and presence of extensive rudists in the upper parts of this formation, lower and upper parts of the Sarvak Formation are deposited in two different sedimentary environments. Presence of micrite in most of microfacies, formation of sedimentary textures such as wackestone to packstone and absence of traceable reefs on the ground, shows that the carbonate sediments of the Sarvak Formation in the lower parts in the studied section were deposited in a ramp carbonate platform. Widespread distribution of rudists in the field, abundance of oligosteginids, and abrupt changes of microfacies along the section; like alteration of pisoid and stromatolite facies to oligosteginids in a short interval, indicates that the upper parts of the studied section were deposited in a carbonate shelf. Three third-order depositional sequences were determined based on the deepening and shallowing trend of facies. The transgressive systems tract consists mainly of microfacies belonging to the lagoon and open marine sedimentary environments, which contain the benthic foraminifera, echinoids and oligosteginids. The highstand systems tract consists mainly of microfacies belonging to the lagoon with green algae and the benthic foraminifera, and also to the microfacies belonging to the tidal flat, which contain stromatolite and pisoid. The maximum progression level in sediment sequences 1 and 2 was determined by microfacies rich in echinoid and rudist debris. In sedimentary sequence 3 it is identified with oligosteginid rich microfacies.

Dezful embayment in the south west of Iran is part of Zagros fold zone which despite the small area includes almost all of Iran oil production. Sarvak Formation with middle cretaceous (Albin-Turunin) is the second biggest reservoir of Zagros basin, after the Asmari formation. In this study, with well logging data of two wells, by Geolog software, the petrophysical parameters of Sarvak Formation in the Dezful embayment was studied using the contingent Probabilistic method. Petrophysical parameters such as determination of porosity, water saturation, shale volume and lithology were calculated using this data and common cross plots. Based on this evaluation and utilizing cross plots result, the lithology of Sarvak formation in this zone was determined to be Limestone with traces of dolomite and shale. According to the calculated petrophysical properties of the reservoir, and for more accurate assessment, Sarvak Formation was divided to 6 sections. Findings of this research show that Sarvak Formation includes good reservoir parameters only in half its sections (sections 4, 2 and 6).

International audience; Comprehensive study of seismic, well-logs and core data is essential in sequence stratigraphic analysis. In the absenceof seismic and core data, gamma-ray logging is an important stratigraphic tool due to its sensitivity to shale content ofstrata. In this paper, gamma-ray log data are divided into two clusters. One cluster with higher average of gamma valueis interpreted as being due to deeper sedimentary environments. A second cluster with lower average is due to shallowersedimentary environments or shelf deposits. This kind of interpretation is based on two assumptions: (1) a deeperdepositional environment produces higher gamma emission, and (2) the gamma-ray log is not much affected fromdiagenetic processes. At each sampling depth, a positive label is assigned to the cluster with higher, and a negative labelto the cluster with lower average. A cumulative diagram of the cluster labels was compared to previously studied environmentalfacies. It was illustrated that the diagram recreates the relative water depth change, so it identifies sequencesurfaces (sequence boundary and maximum flooding surface). The identified sequence surfaces were compared tocore-based sequence stratigraphy of the carbonate Sarvak Formation, southwest Iran, in two oil wells. Sequence stratigraphyinterpretations are judgmental, i.e., based on expert opinion, and being judgmental is a source of uncertaintyfor further decision making. This work reveals that stacking patterns and system tracts of the third-order sequences inthe carbonate reservoirs could be identified in a systematic way using gamma-clustering algorithm. Nevertheless, thewell-log resolution is a limiting factor for identifying the fourth-order sequences.

International audience; The “facies” is a frequently used term for describing sedimentary units. In the literature, this term has been used for different purposes, as depositional environment, rock type, lithofacies, etc. In subsurface geology, the core samples are essential for facies studies. While lacking cored intervals, the well logs provide precious subsurface information, but the complexity of well log responses leads most of the time to the complexity of interpretations. In this paper, a method is proposed to study the facies types through well logs. The case study is a carbonate platform system, deposited in the upper Cretaceous, named Sarvak Formation, in one of Iranian onshore oilfields, located in the Abadan Plain. For this purpose, parametric and non-parametric (k-nearest neighbor) classifiers were applied to the dataset. Detailed petrography, assisted by core descriptions, led to 37 microfacies, grouped into three main lithofacies, four carbonate rock types and six environmental facies. Classifiers could not identify the microfacies due to a limited number of observations and high variations. However, the environmental facies were truly classified. In addition, lithofacies classification and Dunham carbonate rock typing were carried out correctly. It is discussed that k-nearest neighbor is clearly the outperformed classifier, and the classical parametric models were inadequate due to the nature of the input well logs (dependency of well logs and may be their distribution), and the overlapping of the input feature space.

Paleontological studies lead to recognition of 21 genera and 16 species of benthic foraminifera, 5 genera and 6 species of planktonic foraminifera and 3 genera and 3 species of oligosteginids. The vertical distribution of fauna lead to identification of 5 biozones including: Favusella washitensis Range Zone, Oligostegina Assemblage Zone, Rudist debris Zone, Nezzazata-Alveolinids Assemblage Zone, Nezzazatinella-Dicyclina Assemblage Zone. Based on the indicated biozones, the age of the Sarvak Formation is Late Albian to Early Turonian in the study area. Eleven carbonate facies belonging to four environments including tidal flat, restricted and semi-restricted lagoon, shoal and open marine are recognized. The identified facies are deposited on the homoclinal ramp setting. Based on the vertical changes of facies and recognized depositional environments, four third-order depositional sequences are represented. The transgressive systems tracts mainly comprises of open marine facies including sponge spicule, oligosteginid, echinoid and benthic foraminifera, while the highstand systems tracts mainly consists of shoal facies rich in bioclast, and restricted and semi-restricted lagoon facies rich in porcellaneous and hyaline benthic foraminifera and peloid. The maximum flooding surface represented by open marine facies including echinoid and planktonic foraminifera

Sarvak formation, with the middle cretaceous (Cenomanian) age, is one of the stratigraphic units of the Bangestan group in the southern Iran. The carbonate rocks of this formation form the reservoir rock in the study field. Generally, Sarvak formation is subdivided into three members including Mishrif, Khatiyah, and Maddud in the Persian Gulf, and the average thickness of the reservoir unit (i.e. Mishrif) in the field varies from 55 to 73 meters. The purpose of this study is to investigate the petrophysical properties of Sarvak formation in terms of rock type and hydraulic flow unit analysis. In this context, at the first step, the geological characteristics (i.e. sedimentary texture and diagenetic features) of the reservoir rocks were studied in this field. Then, the core porosity and permeability data obtained from different facies plots of the petrophysical diagram of Lucia in which different facies distribute on the three petrophysical classes of diagram based on sedimentary and diagenetic characteristics resulted in the differentiation of eight rock types. Also, using the concept of reservoir quality index (RQI) and flow zone index (FZI), eight hydraulic flow units were recognized and named as A, B, C, D, E, F, G, and H in an ascending reservoir quality order. The results show a good relation between different identified rock types and HFUs in the reservoir, which can be interpreted based on geological attributes.

Sarvak Formation (Late Albian-Middle Turonian) is one of the important reservoir units after Asmari (Oligo-Miocene) in southwest Iran that host an important hydrocarbon reserves in this region. Due to facies and environmental variations as well as complex diagenetic history, its reservoir properties show intense complexity and heterogeneity. To understand these imposed heterogeneities a comprehensive reservoir study including facies analysis, diagenetic study and sequence stratigraphy are carried out. According to facies analysis study, carbonates of the Sarvakformation deposited in a homoclinal ramp-type platform. Low diversity of determined microfacies as well as mud-dominated facies in this field, indicating of a leeward ramp. Main diagenetic processes affected carbonates of this unit are extensive dissolution (in two step: eogenetic and telogenetic), dolomitization (in two ways: mixing zone and stylolite related), cementation (include meteoric, shallow and deep burial cements), micritization, mechanical and chemical compaction (stylolitization), dedolomitization, silicification, pyritization, recrystallization and fracturing. Paragenetic sequence of diagenetic events of this formation above and below Cenomanian-Turonian boundary showed two different histories for these two parts. Three 3rd ordered are recognized in sequence stratigraphic within the Sarvak Formation belong to Middle Cenomanian to Middle Turonian time span. Examining facies distribution patterns and diagenetic events in a sequence stratigraphic framework indicate close relationships and predictability of diagenetic alterations.

The Sarvak Formation in Tang – e – Chenarbashi with 712 meters thickness encompasses Albian - Cenomanian planktonic foraminifera. In the studied section, surveying the Albian – Cenomanian boundary is indicated that Rotalipora appeninica Zone not be recognized. Paracostellagerina libyca can be to consider as a marker for Albian – Cenomanian boundary, absence of the Albian marker foraminifera permit us to consider the first occurrence of this species as the begining of Cenomanian. Also Favosella voloshinae, Paracostellagerina libyca are report for first time from Iran.

The Sarvak formation from the Bangestan group is an important petroleum reservoir in Iran that we studied geochemically in 5 outcrop sections in the Izeh zone. Our results show that characteristics of the Sarvak Formation changed in the Izeh zone. High Sr/Mn ratios and Sr content with heaviest oxygen isotopes of the Sarvak Formation carbonates indicate lower dissolution processes, extensive rock-water interaction (WRI), and a closed diagenetic system. O and C isotope variations suggest marine phreatic diagenesis in the north flank of the Mish, Bangestan, and Mangasht anticlines, and meteoric diagenesis in the south flank of the Mish and Payun anticlines. Observed geochemical variations in the Izeh zone can be related to reactivation of deep-seated structures and faults that caused variation in thickness, facies, and diagenesis.