نشریه رخساره های رسوبی
سال دهم شماره 2 (پیاپی 19، پاییز و زمستان 1396)

Introduction The Asmari Formation at Deris section has been studied in order to biostratigraphy and paleoecology observations. This section with the thickness of 460 m is located at northwest of Deris village, in interior Fars zone of the Zagros Basin with coordinates of E: 51° 32' 26'', N: 29° 41' 59''. The Asmari Formation deposits in this section consists of interbedded gray and cream to gray thin, medium, thick and massive limestone, with slightly dolomitic nodular and marl. Based on field studies and according to the thickness of the layers, color and lithology, 5 lithostratigraphic units have been nominated for the mentioned section. Method and Materials Using regional geological maps, the study section was identified and measured. Field observation focused on detailed description of bed-by-bed thickness, color, lithology and biotic components systematically. 450 samples from the Asmari Formation were collected. Field works were completed with the study of more than 270 thin-sections for identification of skeletal debris, fabric characteristics and microfacies interpretation. Biostratigraphy results have been determined and concluded based on Ehrenberg et al., (2007) and recent biozones introduced by Laursen et al., (2009) and van Buchem et al., (2010). Result and Discussion Biostratigraphy study based on the distribution of benthic foraminifera, led to identification of 19 genera and 19 species, accordingly two assemblage zones have been recognized and Oligocene (Rupelian-Chattian) age was introduced for the Asmari Formation in the Deris section. The suggested assemblage zones are: 1- Nummulites vascus - Nummulites fichteli Assemblage Zone (Rupelian) This collection has been deployed from the base of the section to the thickness of 66 m and consists of Nummulites vascus, Nummulites fichteli, Nummulites sp., Operculina sp., Amphistegina sp., Heterostegina sp., Elphidium sp.1, Elphidium sp.14, Dendritina rangi, Planorbulina sp., Neorotalia viennoti, Haplophragmium slingeri, Nephrolepidina tournoueri, Nephrolepidina sp., Sphaerogypsina sp., Eulepidina sp., Subterranophyllum thomasi, corralinacean algae, miliolids and textularids. Based on strontium isotope study by Ehrenberg et al. (2007), because of the presence of Nummulites spp. this assemblage indicates the Rupelian stage. On the other part, it is equivalent to the assemblage zone number two of Laursen et al., (2009) (Nummulites vascus - Nummulites fichteli Assemblage Zone) and van Buchem et al., (2010). The age is Rupelian stage. 2- Archaias asmaricus - Archaias hensoni - Miogypsinoides complanatus Assemblage Zone (Chattian) This association is introduced for the thickness of 66-460 m and consists of Operculina sp., Amphistegina sp., Heterostegina sp., Elphidium sp.1, Elphidium sp.14, Dendritina rangi, Planorbulina sp., Neorotalia viennoti, Haplophragmium slingeri, Sphaerogypsina sp., Eulepidina sp., Nephrolepidina tournoueri, Nephrolepidina sp., Reussella sp., Valvulinid sp., Borelis cf. pygmaea, Triloculina trigonula, Triloculina cf. tricarinata, Pyrgo sp., Archaias asmaricus, Archaias operculiniformis, Archaias sp., Peneroplis thomasi, Peneroplis evolutus, Peneroplis sp., Austrotrillina howchini, Austrotrillina sp., Meandropsina iranica, Discorbis sp., Ditrupa sp., Spirolina sp., Spiroloculina sp., Bigenerina sp., Miogypsinoides cf. complanatus, Subterranophyllum thomasi, corralinacean algae, miliolids and textularids. It is equivalent to the assemblage number four of Laursen et al., (2009) (Archaias asmaricus - Archaias hensoni - Miogypsinoides complanatus Assemblage Zone) and van Buchem et al., (2010). So, it is considered as Chattian in age. In this study, the Asmari Formation biozones of Deris section also have been correlated with two other sections in the Internal Fars zone and Dezful Embayment zone of Zagros Basin. This comparison confirms that the foreland basin of Zagros becomes deeper in SE to NW protraction. Some ecological factors such as sedimentary basin substrate, depth and hydrostatic pressure, water energy, temperature, turbidity and light influence the distribution and frequency of organisms specially benthic foraminifera (Hottinger, 1983; Romero et al., 2002; Bassi et al., 2007; Flugel, 2010). By study of skeletal elements and accumulation of carbonate grains, it was found that the Oligocene Asmari Formation carbonates have been deposited in the waters of the tropics. Moreover, detailed analysis of microfacies and paleoecology shows that the association of skeletal debris is heterozoan (foralgal, rodalgal and foramol) in this section.

In this research, Calcareous Nannofossils of the Chamanbid Formation in Ghoroneh section have been studied. The Ghoroneh stratigraphic section with 750 meters thickness is located at the Binalud Mountains, about 43 kilometers far in northwestward direction from Neyshabour city. In this study, 64 samples from Chamanbid Formation have been studied. Samples were prepared following a standard smear slide method (Bown, 1999). Calcareous nannofossils nomenclature follows the taxonomic schemes of Perch-Nielson (1985). In general, 27 genera and 49 species of the calcareous nannofossils have been recognized in this section. Calcareous nannofossils recorded in the Mesozoic strata are believed to be an appropriate means for biostratigraphic studies. Abbreviations used in this study are the FO (first occurrence) and the LO (last occurrences). Based on the zone maker of index taxa and their accociated assemblages, biozones NJ9-NJ18 from biozonation scheme of Bown et al. (1988) with the age of Early Bajocian to Jurassic-Cretaceous boundary and CC1 zone from Sissingh (1977) belongs to Early Berriasian, have been suggested for the studied sequence and the biozones are as follows:
Watznaueria britannica Zone: The first nannofossil unit recorded in this study is the NJ9 zone.This bio zone is recorded from the FO Watznaueria britannica to the FO of Stephanolithion speciosum. The age of this zone is Lower Bajocian.

Stephanolithion speciosum Zone: The second nannofossil unit recorded in this study is the NJ10 zone. This biozone is recorded from the FO Stephanolithion speciosum to the FO of Pseudoconus enigma. The age of this zone is Lower Bajocian to Upper Bajocian.

Pseudoconus enigma Zone (NJ11(: This zone spans the interval from the FO of Pseudoconus enigma to the FO of Ansulasphaera helvetica. The age of this zone is Upper Bajocian to Upper Bathonian

Ansulasphaera helvetica Zone )NJ12(: This zone spans the interval from the FO of Ansulasphaera helvetica to the FO of Stephanolithion bigotii bigotii. The age of this zone is Upper Bathonian to Callovian.

Stephanolithion bigotii bigotii Zone )NJ13(: This zone spans the interval from the FO of Stephanolithion bigotii bigotii to the FO of Stephanolithion bigotii maximum. The age of this zone is Callovian.

Stephanolithion bigotii maximum Zone: The NJ14 zone spans the interval from the FO of Stephanolithion bigotii maximum to the LO of Stephanolithion bigotii maximum. The age of this zone is Callovian to Lower Oxfordian.

Cyclagelosphaera margerelii Zone )NJ15(: This zone spans the interval from the LO of Stephanolithion bigotii maximum to the FO of Stephanolithion brevispinus. The age of this zone is Lower Oxfordian  to Upper Kimmeridgian.

Stephanolithion brevispinus Zone (Nj16): This zone spans the interval from the FO of Stephanolithion brevispinus to the FO of Stephanolithion atmetos. The age of this zone is Upper Kimmeridgian to Lower Volgian.

Stephanolithion atmetos Zone (NJ17): This zone spans the interval from the FO of Stephanolithion atmetos to the LO of Stephanolithion atmetos. The age of this zone is Lower Volgian to Middle Volgian.

Watznaueria fossacincta Zone: The NJ18 zone spans the interval from the LO of Stephanolithion atmetos  to ?. The age of this zone is Middle Volgian to Jurassic/Cretaceous boundary. The detail study of Chamanbid Formation at the Binalud Mountains, based on calcareous nannofossils, enables the subdivision of the studied deposits into biozones NJ9-NJ18 from biozonation scheme of Bown et al. (1988) with the age of Early Bajocian to Jurassic-Cretaceous boundary and CC1 zone from Sissingh (1977) belongs to early Berriasian, have been suggested for the studied sequence.

The Moghan area (N38º 30’ to 39º 42’ and E46º 39’ to 48º 10’), as a part of the Kura sedimentary-structural Basin, is located in the NW Iran. The geological and structural history of this area is related directly to its location in northern part of the Talysh-Lesser Caucasus folded and thrusted belt. It is positioned at the collisional zone between the Eurasia and Africa-Arabian continental plates. The convergence is active today, at an estimated rate of 20-30 mm per year.

The area is included in the world’s largest continental collision zone, the Alpine-Himalayan belt, and is marked by intense compression and faulting. The Moghan sedimentary Basin is part of the Para-Tethys Basin that formed in a back-arc and volcanic belt developed from southern France, in the Mediterranean to western China. Tectonic deformations during the Neogene favored the subdivision of Para-Tethys in three major subdomains namely the western, central and eastern Para-Tethys.

This study focuses on the Upper Cretaceous carbonate sequences of the Moghan area, considered as one of the most important intervals in view of their potential as reservoir rocks. Here, facies analysis and paleo-environmental reconstruction of these sequences are presented for the first time in eight surface sections across the study area. This study is based on the stratigraphic and petrographic analysis of Upper Cretaceous sedimentary sequences in Nasir Kandi surface section in the Moghan area, NW Iran. A total of 498 meters of sedimentary thickness were studied and logged. Macroscopic field-features descriptions combined with the results of microscopic studies have been used for facies analysis, paleoenvironmental reconstruction and biozonation. In total, 161 hand specimens were collected for subsequent studies. Sampling intervals were generally between 1 to 3 meters. Upper Cretaceous paleogeographic maps from the eastern part of the Para-Tethys Basin indicate that the Moghan area was located at 30-35º paleolatitude in northern hemisphere. During this time, sea-level was at one of its higher levels in geological history and carbonate platforms developed on continental margins all around the Tethyan realm (Miller et al., 2004). Shallow- to deep marine carbonates were deposited in such platforms in a tectonically active back-arc basin simultaneously to volcanic activity and siliciclastic influx. Based on it paleolatitude location, a temperate to cool subtropical paleoclimatic condition could be considered for this area. This interpretation is also supported by our observations, especially regarding the grain association (skeletal and non-skeletal) of the studied sequences.

Faunal and floral association of this formation (including rudists, other bivalves, echinoderms, benthic and planktonic foraminifera, red algae and bryozoan) represents a foraminiferal-mollusk (foramol) or bryozoan-mollusk (bryomol) association (Coffey and Read, 2007; Einsele, 2013). These communities live in temperate and cold waters and also at deeper settings in comparison to the tropical chlorozoan association (Lees, 1975; Flügel, 2013).

In Nasir Kandi section in westernmost part of the Moghan area, deep-marine pelagic facies are the dominant. Therefore, it seems that the shallow inner parts of the Upper Cretaceous platform were located in the central parts of Moghan area. This shallow platform turns into deep marine settings with a steep slope and without any remarkable marginal barrier, to the southeast and southwest.  Accordingly, biostratigraphic analysis of these facies, based on planktonic foraminifera resulted in recognition of four biozones: Globotruncana ventricosa Zone (middle to late Campanian), Globotruncanella havanensis Zone (late Campanian), Globotruncana aegyptiaca Zone (latest Campanian) and Gansserina gansseri Zone (latest Campanian to early Maastrichtian). We are grateful to the National Iranian Oil Company- Exploration Directorate for financial support and data preparation. The University of Isfahan and the Pars Petro Zagros (PPZ) Company are thanked for the provision of facilities for this research. Journal editor and anonymous reviewers are acknowledged for their kind helps.

The Iranian Plate is regarded as a marginal fragment of Gondwana, which has been separated from Gondwanan-Arabian plate during the Late Paleozoic or Early Mesozoic (Early Triassic) and has been connected with the Eurasian Turan plate at the end of Middle Triassic time (Berberian and King, 1981; Soffel and Förster, 1984; Weddige, 1984a; Scotese, 2001). Tectonically, Iran is subdivided into several structural zones that have been affected with numerous folds, faults and recurrences, so that respectively each zone has different geological characteristics with exclusive sedimentological features and fossil contents (Stocklin, 1968; Wendt et al., 2005). The studied section is located at the vicinity of Tar village (Tarq area), about 45 km southwest of Natanz city, 110 km northeast of Isfahan. The area structurally belongs to the Sanandaj-Sirjan Metamorphic belt at the contact area between Uromiyeh-Dokhtar volcanic belt and Central Iran Microplate. The project conducted the biostratigraphy of the Middle - Upper Devonian deposits based on conodont fauna to establish the precise age of the Bahram Formation in the studied profile. Bahram Formation in the studied section is composed of 3 separate units with different lithological characters and different fossil contents. The first clastic unit is an alternation of dolomites, sandstones and minor shale interbeds with rare fossils, disconformable overlaid Padeha Formation. The second and Third units are mainly carbonate with several fossiliferous horizons. Zahedi (1973), Adhamian (2003), Ghobadipour et al. (2013) and Bahrami et al. (2015) studied the Devonian deposits in the central Iran area, and they all reported pre-Permian erosional disconformity (Hercynian phase). Wendt et al. (2002; 2005) and Berberian and King (1981) also reported the same phase from the other localities where Paleozoic rocks are exposed in Iran. Sharland et al. (2001) and Ruban et al. (2007) believed Per-Permian erosional corresponds to the deformation and uplifts of contemporaneous to the Neothetian rifting in the Middle Permian time. Forthy –six samples collected for systematically conodont studies and processed with conventional acetic/formic acid. Besides, a few samples, that were prolific, let us to stablish the conodont zonation for the studied interval. Based on revealed data out of conodont studies, 26 conodont species belong to 4 genera were identified: Icriodus. obliquimarginatus, I. subterminus, I. brevis, I. expansus, I.excavatus, I. eslaensis, I. alternatus alternatus, I. sp. nov, I. aff. difficilis, Polygnathus. varcus, P. cf. parawebbi, P. ensensis, P. linguiformis linguiformis, P. linguiformis linguiformis γ1a, P. linguiformis linguiformis γ1b, P. linguiformis linguiformis γ2, P. linguiformis linguiformis γ4, P. pseodufoliatus, P. alatus, P. angustidiscus, P. webbi, P. politus, Polygnathus xylus, P. aequalis, Ancyrodella sp., and Bipennatus bipennatus. Three conodont zones were discriminated as follow: expansus Zone, subterminus Zone, Upper falsiovalis (Frasnian)?. The conodont biostratigraphy proves the Late Givetian to Early Frasnian? age for the deposits of the Bahram Formation in North Tar section. Icriodids and Polygnathids dominated between the studied conodont fauna yielded Icrodid-Polygnathid biofacies to the studied interval, although in the upper expansus zone and Lower Frasnian? interval of the section indicates more or less the Polygnathid-Icriodid biofacies, the privilege of the deeper condition than the subterminus part of the section. The CAI (color alteration index) of the conodonts were close to 4/5-5 shows high temperature after burial process that indicator of no gas and oil potential in the area.  This article is extracted from a research project No. 910712 entitled "Biostratigraphy of Devonian rocks (Bahram Formation) in the North-tar section (Southwest Natanz) based on conodonts". The Project financially and logistically supported by the Vice chancellor for Research and Technology office at University of Isfahan which deeply appreciated. The author also thanks to Dr. Vachik Hairapetian (Islamic Azad University Khorasgan Branch) for his valuable guidance in determination of the vertebrate micro-remains.

Important known bauxite deposits in Iran, which occur in the so called Irano-Himalayan belt, are spatially distributed in four regions, namely (1) the northwest of Iran (e.g. Bukan, Shahindezh), (2) the Zagros heights, (3) the Alborz Mountain Range and (4) the central plateau of Iran. They are restricted to Permian, Permo-Triassic, Triassic, Triassic-Jurassic, and Middle Cretaceous (Cenomanian–Turonian) in ages (Abedini & Calagari, 2014).

The Gazanjeh area is located about 25 km southeast of Bukan city, south of West-Azarbaidjan Province, NW Iran. The stratigraphical gap emerged during the Late Permian is manifested by the development of a bauxite horizon in this area. The propose of the present study is to indentify the texture, mineralogical types, controlling factors of distribution and mobilization of major, minor, and trace elements in residual facies, paleo-geographical conditions, sedimentary environment of formation and development of the bauxite deposit in the Gazanjeh area.


In this study, a profle perpendicular to the strike of bauxitic layers was selected and 16 systematic and

representative samples with varying intervals (80-150 cm) were collected. Laboratory works began with preparation of thin and /or polished sections from all 16 samples and their examination under microscope. For the identification of mineralogical phases in the bauxites, 8 samples from a selective section were chosen for X-ray diffraction (XRD) analyses.  XRD analyses were carried out using diffractometer model D-5000 SIEMENS in Geological Survey of Iran (Tehran). The chemical compositions of the bauxites (#16) were determined at the Kansaran Binaloud Company, Tehran, Iran. The values of major and minor elements were determined by X-ray fluorescence (XRF). Rare Trace element contents were determined by inductively coupled plasma mass spectrometry (ICP-MS). Loss on ignition (LOI) was determined by weight loss of 1 g sample after heating at 1000 °C for 60 min.

Since the rocks are fine-grained, identifcation of minerals in the bauxite ores under a microscope was not possible.Terefore, petrographic examinations were principally focused on textural features of the ores. Considering the mode of distribution of texture-forming components and matrix, various kinds of textures such as pelitomorphic, microgranular, ooidic, pisoidic, macro-pisodic, spastoidic, colloform, nodular, pseudo-breccia, breccia, and clastic identified within the ores. These textures show allogenic origin for deposit (Bardossy, 1982). The pelitomorphic and colloformic textures imply an indirect bauxitization and weak draining processes during the evolution of this deposit. The development of hematitic nodules in the ores can be attributed to factors such as variation in water activity in pedogenic environments and/or climatic fluctuations (Mongelli, 2002). The XRD analyses show that the minerals including diaspore, hematite, pyrophyllite, chlorite, chamosite, rutile, anatase, and muscovite-illite are the main mineral phase of the phreatic.Trivariate plot of SiO2-(Al2O3+TiO2)-Fe2O3 (Balsubramaniam et al., 1984) denotes that three distinct mineralogical types can be differentiated within the horizon, namely (1) laterite, (2) ferruginous laterite, and (3) siliceous bauxite. Also, plotting the Kanigorgeh data on trivariate diagram SiO2-Al2O3-Fe2O3 (Schellmann, 1982) attests to the formation of the above ores under moderate to intense lateritization conditions. Trivariate plot of SiO2-Al2O3-Fe2O3 (Meshram & Randive, 2011) reveal that deferritization-ferritization mechanisms and destruction of kaolinite were the most important processes involving during development of ores in this deposit. Comparison of the range of stability fields of major constituent minerals of the bauxite ores with the pH and Eh variations of natural environments (Temur & Kansun, 2006) show that this deposit formed two facies, (1) oxidant-basic and (2) reduction-acidic. Geochemical investigations indicate that the degree of concentration of elements such as V, Zr, Co, Cu, Ga, Hf, Mo, Sc, U, and Zn in oxidant-basic facies and concentration of elements such as Ba, Cr, Ni, Pb, Rb, Sr, and Th in reduction-acidic facies is great. Difference in concentration of elements in these two facies can be associated with occurrence of processes such as adsoption by clays, scavening by hematite and manganese oxides, lateritization intensity, function of carbonates bedrock as geochemical barrier, and chemistry of meteoritic waters (Braun et al., 1990; Mordberg, 1996; Schwertmann & Pfab, 1996; Marques et al., 2004; Fernandez-Caliani & Cantano, 2010; Ndjigui et al., 2013; Abedini & Calagari, 2014).

Dariyan formation which is one of the oil reservoirs in the south pars field, has been studied in wells SPO-1, SPO-2, SPO-3 from this field. Six hydraulic flow units (HFU) were identified by flow zone indicator (FZI) for reservoir facies, including HFU-A, HFU-B, HFU-C, HFU-D, HFU-E and HFU-F. Comparison between these hydraulic flow units indicate HFU-A and HFU-B with very Low reservoir quality, HFU-C with low reservoir quality, HFU-D with medium reservoir quality and HFU-E and HFU-F with high reservoir quality which reveal good correspond with facies texture and diagenetic specifications. Also, based on studies, four rock types were identified. Rock type 1 includes flow unites mostly with very low reservoir quality (B, C), and flow unites with medium (D) and flow unites with high reservoir quality (E, F) are lesser. Rock type 2 is nearly semblable to rock type 1 albeit, flow unites with medium (D) and high (E) reservoir quality are more and flow unites with very low and low reservoir quality are less than rock type 1. Rock type 3 is more liaise to flow unites with high reservoir quality (E, F) and less with medium reservoir quality (D). Rock type 4 is only related with flow unite with high reservoir quality (F).

Generally, the groundwater chemistry depends on many factors, including the quality of the recharged water, the hydrogeological‏ conditions, water-rock interactions‏, human activities etc‏ (Kumar et al., 2012). According to these processes, the chemical composition of groundwater varies with respect to space and time and the concentrations of chemical species increase in groundwater flow path (Sharif et al., 2007; Suma et al., 2014;  Rattan et al., 2005)‏. The water-rock interaction and the types of chemical reactions (dissolution, precipitation, ion exchange processes, redox etc.), which effected on groundwater quality, usually is determined in the discharge point. Based on chemical composition, the quality of groundwater‏ is classified to drinking, industrial, and agricultural categories (Elgano and Kannan, 2007, Subramani et al., 2005). Assessing the quality of groundwater and surface water resources, especially in areas related to groundwater for drinking, is very important. Rocky and alluvial facies have different effects on the quality of water resources (Clark, 2015). Sedimentary rocks and minerals, especially minerals in evaporite formations‏ damage the water quality (Jagadeshan et al., 201; Ozman et al., 2011; Redwan et al., 2016; Choi et al., 2013). The most important aim of this paper is to investigate the subsurface alluvial deposits and geological formations (rocky and alluvial facies) and their effect on the chemical characteristics of water and the water quality for various uses (drinking, agriculture, and industry) in Samalqan plain. The collected drilling‏ data of 15 exploitation wells from North Khorasan Regional Water Company, has been used for the purposes of this study. Sampling from deep wells in different parts of the plains has been done to assess the water quality in both wet and dry seasons in Year 1392-93. Arc GIS (10.1), PHREEQC 2.6, Aq.QA, Excel, and RockWorks14 software's were used to generate required maps and diagrams. Using the available‏ drilling logs information in both AA' and BB' directions, the geological layers of sediments were investigated in the Samalqan plain. Based on dfistribution of coarse sediments in the North East of the plain (in AA' cross section), the water table depth increases from the northeast to the southwest. As drilling logs show, the geological facies changes in this direction and it shift from gravel in the southwest to muddy and sandy in central part of the plain and finally to gravelly in the northeastern parts of the plain. In BB' trend, along the east - west and north of the plain, the Tirgan Formation facies and the Neogene sediments have an important role in the quality of water resources. The drilling logs in this direction indicate that the gravelly sandy and muddy facies is visible and it changes from muddy to sandy and gravely from East to West. Due to the proximity to facies changing to the limestone of Tirgan Formation, the electrical conductivity (EC) of water shows minimum values in the southern part of the plain. The abundance of cations and anions facies are like Na+ >Mg2+ > Ca2+>K+‏ ‏ and Cl- > HCO3- >SO42-, respectively. According to the Pie chart in both dry and wet seasons, the concentration of bicarbonate is reduced however, the concentrations of sodium, chloride, and sulfate are increase from south to the north of the plain, which is due to the existence of Neogene sediments in the eastern part of the plain and to the lack of aquifer recharge from northern part of the plain. The groundwater equipotential map show that the direction of groundwater flow is toward northern (the output of the catchment) and the type of‏ groundwater changes from bicarbonate to chlorine in this direction. Saturation indexes of minerals indicate more dissolution of halite and gypsum with respect to‏ calcite and dolomite in Samalqan plain. Samalqan water resources have good to unpleasant quality for drinking, and its water is appropriate to un- appropriate in terms of agricultural usages and it is corrosive sedimentational in industry point of view. We need to appreciate the efforts of Dr. Mohammad Vahidinia, Dr. Asadullah Mahbuobi and Dr. Mohammad Khanehbad, from Ferdowsi University of Mashhad, Mr. Davarpanah, head of Ashkhane water affairs, Mr Karimi, head of Ashkhaneh water affairs archives, Mrs. Bakhshabadi, secretary of water resources studies of North Khorasan Regional Water, Mr. Bahrami and Mr. Moniri, East Abkav company, Mr. Abyari, digger of Yazd Abgune company. As well as we thanks the efforts of Mr. Moheghi, Mr. Sohrabi, Mr. Asemani,Mr. Eskandari, Mr. Shadmehr, Mrs Zandvakili and Mrs Valizadeh.

Considering that detail paleontological and sedimentological studies have not been carried out on the northern Nourabad area, this study is based on measured stratigraphic section of the Haft- Cheshme to evaluate and analyize the parameters such as biostratigraphy and sedimentary environments of Miocene deposits, inorder to gain the new information about the geology of the area. In this study, large benthic foraminifers used to identify the biozones and determine the age of these deposits. On the other hand, in order to obtain new information on the formation of these deposits, the study of sedimentary environment was also discussed. For detail study of these deposits, sampling were done at 1 meter interval. A total of 100 samples were collected from a thickness of 127 meters. The sedimentary facies are named based on Flugel (2010) classification. Also, in the designation of carbonate facies, Dunham (1962) and Ambry and Klovan (1971) have been used for the classification of carbonate facies. The lower boundary of Miocene deposits in this section is sharp with Mc unit of ophiolitic complex and the upper boundary is erosional. Based on the studies of the larger benthic foraminifera assemblages, 18 genera and 20 species were identified which represent the Borelis melocurdica- B. melo melo assemblage zone and suggest a Burdigalian age. Also based on the field observations, petrographic studies and textural characteristics as well as the abundance and distribution of foraminiferal fauna and other components, 14 carbonate microfacies have been identified. These carbonate microfacies were deposited in 5 facies belts including lower slope facies, upper slope facies, margin facies, platform-margin sand shoals and lagoon. The existence of coral barrier reefs, intraclasts, aggregate grains and the sudden facies changes and also the absence of vast areas of intertidal flat represent that this sequence deposited on a rimmed carbonate platform.  Also based on the petrographic studies of Bouma Ta and Tb divisions and the existence of the sedimentary structures such as Bouma Ta division (re-deposited carbonates, calciturbidites), the studied section has been deposited on a rimmed carbonate shelf.