GEOSCIENCES
Year:2015 | Volume:24 | Issue:95 (STRATIGRAPHY & SEDIMENTOLOGY)|Papers Count:30

Paleozoology of Yafteh and Kani Mikaiel caves in center and northwest of Zagros Mountains led to the identification of small mammals’assemblage. Taxonomic determination revealed inclusion of four orders of small mammals including: order Rodentia with families of Muridea, Cricetidae, Calomyscidae, Dipodidae; order Lagomorpha with two families of Ochotonidae and Leporidae; order Soricomorpha with family Talpidae, and order Carnivores with family Mustelidae. These remains were recovered after systematic excavation in these caves. Radiocarbon analysis of these remains showed the oldest sample belonged to Yafteh cave with 35, 000 BP. and Pleistocene period, whereas, Kani Mikaiel cave covered the periods from lat Pleistocene (19, 000 BP.) to Holocene (17, 00 BP.). Geochronology analysis of Kani Mikaiel sediments showed that the lower layers of this cave belonged to the last glacial age in Pleistocene which gradually has been replaced by the warm weather in Holocene period. With continuing of this weathering varying, faunal spectrum of Pleistocene and Holocene periods has been migrated in cold and warm phases or more spread. The aim of this research, are the study of small mammal remains of Yafteh and Kani Mikaiel caves in center and northwest of Zagros mountains and the research about the study of paleobiodiversity, paleoenvironment conditions and the evolution of microvertebrate on the Iranian plateau.

The Gurpi Formation at Farhadabad section in west of Darehshahr, was studied in detail for environmental changes and water–level fluctuations via using organic matter contents of the rock samples. Depositional environment interpretation was done based on integration of evidences derived from organic geochemistry analysis (TOC, TIC and Aliphatic n-alkane (short, mid and long chain n-alkane to sum of n-alkane, TAR (terrigenous-aquatic ratio), CPI (Carbon Preference Index), ratio of C17 to C27 and Isoperinoids (pr/ph, pr+ph/nC17+nC18, pr/nC17and ph/ nC18) and palynofacies data (Amorphous organic matter, marine palynomorphs and palynomaceral). Statistical studies on palynomorphs confirm the results gained from the organic geochemical analysis. High ratio of palynomaceral and high TAR and CPI and dominance of long chain n- alkane and low ratio of C17/C27 (C17 relative to C27) and high ratio of Pr/Ph (>1) indicate regression condition at the base of the Gurpi Formation, Lopha Member, top of Emam-Hassan Member and Cretaceous – Tertiary boundary. On the other hand high abundance of marine palynomorphs and transparent amorphous organic matter and unimodal n-alkane with a marked even over odd predominance (CPI< 1) and TAR<1 and high C17/C27 (C17 relative to C27) and low ratio of pr/nC17<0.5 indicate transgressive condition in upper part of Globotruncanita stuartiformisbiozones, black shales between Lopha and Emam- Hassan, upper part of Contusotruncana contusa biozones and at the base of purple shale of the Pabdeh Formation. Maximum flooding surface probably equates the 70 Ma MFS K175, 68 Ma MFS K180 and 58 Ma MFS Pg10 of Sharland et al., 2001 that is recorded in many parts of the Arabian Plate. The relative sea level curve resulted in form this study is well in accord with the existing eustasy curves especially for the Campanian- Maastrichtian boundary indicating effect of eustasy on relative sea- level changes during this period. Combining all these data, an open marine environment with terrestrial organic input under suboxic to anoxic conditions can be concluded for the depositional course of the Gurpi Formation.

A relatively thick sequence of Mid-Cretaceous (Aptian) strata exposed in Baghin area, west of Kerman, Iran. The strata comprise a diverse macro-fauna such as bivalves, echinoids, gastropods, corals and brachiopods. Among the bivalves, presence of a pectinid species, Neithea notabilisis relatively conspicuous. The studies show a marked morphological variation in the species. Also, biometric analysis reveals a mark interspecific variation in the studied specimens. Low diversity in the genusNeithea could be due the high isolation of the Baghin area and therefore its limited connection to other water masses during the Mid-Cretaceous or because of its contribution to the diversification trend seen in the Mediterranean region.

The Asmari Formation is well-exposed at Kuh-e-Mish, locating at Gorg-Darreh area (The Zagros fold-thrust belt). In this area, the true thickness of Asmari Formation is 480m. This formation was studied for its microfacies analysis in Gorg-Darreh area (kuh-e-Mish). In this study, seven microfacies was recognized within this formation. These microfacies belong to the tidal flat, restricted lagoon, protected lagoon, patch reef, foreslope, basin sub-environments.A carbonate ramp is suggested for depositional environments of the Asmari Formation. Likewise, distributions of foraminifers of this formation were studied in order to determine the age relationships of the Asmari Formation. In this study, 45 species belonging to 41 genera were identified. In general, three assemblage biozones were recognized in this formation, consisting of Lepidocyclina – Operculina - DitrupaAssemblage Zone, Peneroplis evolutus - Austrotrillina howchini Assemblage Zone and Borelis melo curdica – Meandropsina iranicaAssemblage Zone. Therefore, based on these assemblage biozones, the Asmari Formation is assigned to late Oligocene (Chattian) – early Miocene (Aquitanian- Burdigalian).

Carbonate successions of the Ziarat Formation with introduce the Baghdareh and Gheynarjeh sections in the Soltanieh Mountains (southern Zanjan) are rare locality in the western Alborz zone, which are contains of great abundance of large benthic foraminifera (LBF), particularly species ofAlveolina. In fact, from this succession described some of Alveolina species and their comparative stratigraphic distribution with theAlveolina species in the Tethyan basin which is represent close affinities with coeval Alveolina assemblages described in diVerent studies from this province. Also, this correlation shows Ilerdian-Cusianstages of study area that characterized by A. ellipsoidalis, A. laxa, A. tumida, A.cemali, A.aragonensis, A. pisiformis, A.rotundata, A.subpyrenaica, A. cf. canavari, A. canavari, A.ex gr. cremae species.

The Permian deposits in the Sibestan section located 65 km northwest of Tehran, consists of 3 formal formations. The formations from lower to upper include: 1- Dorud Fm. consisting of 205 meters of siliciclastic deposits of early Permian age and according to the lithostratigraphy facies is divided into 10 rock units.2- Ruteh Fm. consisting of 178 m. of limestone of late early Permian (Murghabian) age and lithostratigraphically divided into 5 units.3- Nessen Fm. consisting of 54 m. of limestone, shale and sandstone of lower Julfian age. This formation is also divided into 8 lithologic units. The Permian strata terminates by bauxite-laterite horizon of Julfian equivalent age. This sequence is covered disconformably by 28.10 m. of yellowish gray platy limestone of strata, the lower Triassic Elika Fm. According to the paleontological studies, three foraminiferal biozones in Ruteh and Nessen formations have beenidentified. Ruteh Fm.: 1- Schubertella giraudi-Codonofusiella distincta assemblage zone of Bolorian? -Kubergandian age, 2-Cribrigenerina sumatruna- Langella ocarina assemblage zone of Murghabian age; Nessen Fm.: 3-Paraglobivalvulina mira-Ichtyolaria assemblage zone of Median? - Julfian age. In addition, 14 species and genera and one subspecies of conodonts have been identified and also 2 conodonts biozones have been recognized in this section which correspond to the international conodont zones. Ruteh Fm.: 1-Sweetognathus whitei biozone of Early Permian; Elika Fm: 2- Hindeodus parvus-Isarcicella isarcica biozone of Early Triassic, 3-Pachycladina symmetrica-P. oblique assemblage zone of Early Triassic.

Succession of Permian strata in Pir-Eshagh stratigraphic section has been measured totally about 1400 m, which is consists mainly of Dorud formation with a thickness of about 100 m which in turn has been overlain by Ruteh and Nesen formations with thickness of 1100 and 200 m respectively. This succession overlay unconformably Devonian volcanic rocks and is in turn overlain by the yellow lamellar limestone of Elika Formation that deposited during early and middle Triassic. For identification of various calcareous genera and species of algae in these sediments, we systematically selected 220 thin sections from the lower up to the upper bounds based on the lithological changes perpendicular to the strike of layers. In this study, we identified seven genera and nine species of dasycladacean green algaeMizzia sp., Mizzia velebitana, Mizzia cornuta, Macroporella cf. nuda, Macroporella sp., Epimastopora sp., Epimastoporasymetrica, Paraepimastopora longutuba, Epimastopora likana, Epimastoporella japonica, Tabasoporella tulipaformis, Gyroporella sp., Gyroporella nipponica, and two genera and 5 species of gymnocodiacean algae, Permocalculus sp., Permocalculus cf. dikenliderensis, Permocalculus fragilis, Permocalculus plumosus, Permocalculus tenellus, Gymnocodium sp., Gymnocodium bellerophontis at Ruteh and Nesen formations. Also, Tabasoporella tulipaformisalgae belonging to the dasycladaceae family which has been introduced from the Jamal formation, was identified and reported from the carbonated units in the northwest of Iran.

Calcareous nannofossils were used for biostratigraphy and biozonation of Surgah Formation at Kabirkuh section close to the Ilam dam. This formation is mainly composed of 153.7 meters dark gray shales from which 109 samples were for nannofossil studies. Their study lead to identification of 16 family, 44 genera and 80 species. Based of the first and last occurrence of the index species and accompanying forms standard zones of CC13-CC15 or Uc8- Uc 12 were identified resulting in an age of Turonian - Early Santonian for the Surgah Formation.

In this study, 60 samples have been studied from Carboniferous deposits of Khames stratigraphical section, 10 Km southeast of Khalkhal. The marine sequence of Khames stratigraphical section is about 163.5 m. thick and consists of gray to black Limestone and dolomitic limestone.The lower boundary of the under study section marked with yellowish limestones of Cretaceous and dark Sills with Faulted contact. The upper boundary of the Carboniferous strata is covered with Pliocene Polygenetic conglomerate disconformably. The Carboniferous unit studied here has not been named so far, so in this research, we have attempted to identify the stratigraphical position of the mentioned sequence. In this research 30 genera and 25 species of benthic foraminifera were identified similar to those reported from carboniferous strata of Qezelqaleh, Bagher Abad, Mobarak and Sardar formations suggesting a Late Visean to Early Bashkirian age for the Khames Carboniferous marine sequence.

The Gurpi Formation stretches through the Zagros basin, SW Iran. This formation at the Banroushan section, SW Ilam, consists of 225 m shale with interbeds of marl forming two formal members of Seymareh (Lopha) and Emam Hassan. These Members are made up of limestone. The lower and upper boundaries of this formation are continuous with the Ilam and Pabdeh formations. In the present investigation, 46 planktonic species of 13 genera have been identified and based on which the Gurpi Formation is divided into 10 biozones. which are cosmopolitan. These are: Biozone 1-Globotruncanita elevata Partial Range Zone; Biozone 2- Globotruncana ventricosa Interval Zone; Biozone 3- Globotruncanita calcarataInterval Zone; Biozone 4- Globotruncanella havanensis Partial Range Zone; Biozone 5- Globotruncana aegyptiaca Interval Zone; Biozone 6-Gansserina gansseri Interval Zone; Biozone 7- Contusotruncana contusa Interval Zone; Biozone 8- Abathomphalus mayaroensis Interval Zone; Biozone 9-Parasubbotina pseudobulloides Interval Zone; Biozone 10- Globanomalina pseudomenardii Interval Zone. Based on these biozones the Gurpi Formation in the study area is dated as Early Campanian to Paleocene.

Rich assemblages of Carboniferous corals exist in the Zaladu stratigraphic section. After identification of corals, more than 200 thin sections of coral fossils and microfacies were selected and studied for environmental parameters. This association belonging to Bashkirian age (the oldest stage of Late Carboniferous) and were found in two horizons. Based on the colonies geometry, the distance between them, the abundance and distribution of corals and microfacies study, the habitats of lower horizon is “ Coral meadows (subtype B1) “. The upper horizon made a“polyspecific Coral biostrome (subtype C2) “. These corals existed in a lagoon toward barrier and open marine toward barrier belonging to a shallow carbonate ramp environment. This association favored a shallow, warm, and clear marine environment with normal salinity and high oxygen, within the photic zone. The fasciculate rugoseFomichevella and Heintzella, have the most abundance, and these colonies form the main builders of the coral association. Colonial rugose coralsFomichevella and Minatoa have maximum diversity. Michelinia tabulate corals, has the least abundance and diversity.

Pabdeh Formation has been investigated in three sections viz. the Type Section, Tang-e Hatti and the northern limb of Gurpi Anticline within the Zagros Sedimentary Basin with emphasis on calcareous nannofossils. Study of microscope slides prepared from the 1508 collected samples resulted in determination of 256 species belonging to 59 genera from 22 families of nannofossils and biostratigraphic classification was carried out based on their stratigraphic distribution. According to Martini (1971) zonal scheme, presence of NP4-NP23 nannofossil zones at the Type Section, and NP5-NP23 nannofossil zones at both Tang-e Hatti and northern limb sections have been ascertained thus indicating Early Paleocene to Early Oligocene age for the Pabdeh Formation at these three localities. Calcareous nannofossil assemblages reveal sedimentation of Pabdeh Formation occurred in an oligotrophic, warm water environment during Paleocene-Eocene which was later on replaced by a relatively cooler water condition in Oligocene times.

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

Aitamir Formation is a well-known rock unit inKopeh-Dagh range in the north east of Iran. This formation has been made up of a sandstone part in the lower and a shale sector in the upper. Both parts are Glauconitic and often seen in Olive-green color. This research is on a section of the Aitamir Formation based on Palynomorphs which has been conducted on the route from Mashhad to Kalat-e-Naderi, in the edge of Zavin village with a thickness of 506 meters and the coordinates of 36o 43’ 45.42” north, and 59° 57’ 5.56” east. Some 40 samples of this section have been gathered and 120 Palynological slides have been prepared. The study of these slides has resulted in identification of 28 genera and 47 species of dinoflagellates. Regarding the identified dinoflagellates, the age of the formation was confirmed as Albian-Cenomanian. The study of the factors involved in preservation of organic materials shows low to moderate levels of oxygen, with low depositional rate and an inner to outer neritic environment for the formation in the mentioned section. Three Palynofacies differentiated also confirm these results.

Albian–Cenomanian siliciclastic-carbonate sediments of northwest Rayen in south Kerman, southeast Iran (526 m) are classifiable to three informal units. Unit one includes conglomerates, sandstones and siltstones with limestone and marl intercalations. Unit two is composed of Orbitolina bearing limestones with rudists, belemnoid and ammonite bioclasts. Alternations of pelagic limestones and sandstones formed the third unit. Assemblage of continental to marine trace fossils have been found in the first and third units of the studied section, that include Koilosomaisp., Ophiomorpha isp., Palaeophycus isp., Planolites isp., Skolithos isp., Taenidium isp., and Thalassinoides suevicus. These trace fossils belongs to Scoyenia, Skolithos and Cruziana ichnofacies. AbundantThalassinoides-Phycodes compound trace fossil, however have been found in the third unit. Box-workedThalassinoides burrow system ends to multi- branched Phycodes borrows. This compound trace fossil is interpreted as feeding-domicile biogenic structure, so thatThalassinoides domichnium ends to Phycodes excavated feeding burrows.CompoundThalassinoides-Phycodes trace fossil extended in the deeper parts of offshore shelf sediments in the studied section. Based on ichnological data, it seems that Albian-Cenomanian sediments of northwest Rayen deposited in a deepening upward sequence.

Geomagnetism is one of the most applied techniques of geophysics in geology. Today, this method is applied in different disciplines such as Magnetic fabric of rocks, palaeomagnetism and environmental magnetism. Each of these magnetic methods is suitable for a particular lithology.Therefore, the potential of sandstones of Shemshak Group, in central Alborz Mountain range were examined to record their response to the application of some conventional magnetic methods. This rock unit is formed during two major tectonic events of early and middle Cimmerian and has great coverage not only in the study area but also in a vast majority of Iran. The total number of 135 oriented core samples was taken from 18 stations. In this study combination of magnetic and petrographic data are examined. The result of magnetic mineralogy analysis of all samples (except samples from stations 10 and 15) show irreversibility i.e. minerals such as hematite and magnetite, have formed during the heating stage. The results of thermal demagnetization analysis showed that ferromagnetic minerals present in the samples (except samples from stations 10, 14 and 15) have demagnetized below 400oC and by proceeding heating, samples show zigzag pattern or show abnormal increase in susceptibility. This indicates that, the magnetic minerals are formed during heating in one stage and due to unstability lose its susceptibility in other stage. The magnetic susceptibility (Km) vary from 200-400×10-6 SI for more stations of study area, indicating abundance of paramagnetic mineral in this rock unit. From petrography point of view all the sandstone samples are classified as arenites and ratio of quartz to lithic fragment and feldspar is relatively low, which may indicate low mineral maturity. Comparison of magnetic mineralogy and thermal demagnetization data for two stations S10 and S15 show that there is an inverse potential relationship between amount of stable ferromagnetic mineral in a sample and amount of its alteration during heating stage. The results of this study reveal the poor nature of Shemshak Group sandstones for palaeomagnetic studies due to their low mineral maturity and water percolation which increase the possibility of acquisition of chemical remanent magnetization (CRM). The high sedimentation rate of sandstones cause magnetic inclination and declination error, and low ferromagnetic mineral fraction in samples, make them unsuitable to record magnetic directionsduring formation of rocks. However, abundance of paramagnetic minerals such as biotite in these rocks, proves their applicability for magnetic fabric studies.

The Lower Carboniferous deposits (Shishtu II Formation) is exposed in the Banarizeh section, Southeastern Isfahan, Central Iran. The Shishtu II Formation is characterized by continental to shallow marine deposits, where it unconformably overlies the Alluvial deposits and is unconformably overlain by the Sardar Formation. The thickness of Shishtu II Formation reach to 195m and contain moderate diversity, high richness Holothurian sclerites assemblages and other skeletal particles of scatter Crinoids, Brachiopods and Corals. The systematic studies and taxonomic investigation carried out on the collected samples from studies area led to recognition of 8 species belonging mainly to 4 families (Calclamnidae, Achistridae, Palaeocaudinidae, Theelidae). The Holothurian sclerites in Shishtu II Formation are dominantly as: Eocaudina subhexagona, Eocaudina ovalis, Microantyx permiana, Mercedescaudina langeri, Protocaudina hexagonaria, Achistrum monochordata, Thalattocanthus Consonus.Based on sratigraphical distribution of the Holothurian sclerites, Tournaisian- Visean age is suggested for Shishtu II Formation.

The Dalan upper member is a gas reservoir in the Persian Gulf, which is important because of gas and condensates production. This unit has been affected by dolomitization. Dolomicrites is a type of dolomites identified in the studied interval. This investigation concentrates on dolomicrites from the point of view of its spatial distribution and reservoir zonation. This type of dolomite has been studied using thin section, RCAL, and isotopic analysis data. This type of dolomite is identified relying upon petrographical evidences such as very fine to fine unimodal, anhedral to subhedral crystals of dolomite. The texture is equivalent to xenotopic-A and nonplanar-A. Some features like fenestral fabrics, microbial filaments evaporitic cast, anhydrite nodules and mud cracks are also identified. The findings led us to the conclusion that dolomicrites pertains to fenestral dolomitic mudstone, which deposited in supratidal to arid upper intertidal. The result of isotopic analysis of oxygen revealed that this dolomite formed at temperature between 20.36oC to 46.6oC. This confirms deposition in sabkha environment so sabkha dolomitization model offered for dolomicrites. The diagenetic processes affected dolomudstones are dissolution, cementation, compaction, anhydrite replacement and fracturing. Studies of the porosity and permeability data indicated that reservoir characterization is under the influence of texture. In mud-dominated facies like dolomitic mudstone, reservoir quality is poor to fair unless this part influenced by subsequent diagenetic processes like dissolution and fracturing.

The Middle- Late Triassic Dashtak Formation acts as one of the best seal for giant gas reservoirs entrapped within the Dehram group inthe Southwest of Iran and the northern Persian Gulf because ofthick anhydrite deposits. The facies analysis of Dashtak Formation led to recognition of 14 microfacies, which are related to coastal plain, sabkha) supratidal (, tidal flat, lagoon, and shoal environments. Examination of the vertical and lateral facies changes and thire comparison with their modern and ancient counterparts, all indicate that the Dashtak Formation was deposited in a shallow carbonate ramp platform. The sequence stratigraphic studies showed that the Dashtak Formation consists of four thirdorder depositional sequences, each consisting of the transgressive and highstand systems tracts. The thickness of this formation increases from the Kuh-e Surmeh toward the boreholes d, c, b and a. A strontium isotope dating of the Dashtak Formation indicated a Triassic age from Ansian to Norian stages.

Rock typing by different techniques is useful to interpret the zoning of reservoir. As the hydraulic flow unit has an effective connectionbetween the geological and petrophysical conditions, recognition of distribution quality of flow units in a reservoir can be useful for separation of reservoir into different units with different reservoir conditions. In this study, by using of flow zone indicator (FZI), six flow units has been determined based on the porosity and permeability data in both wells A and B of the Bangestan reservoir in the MansouriOil Field. The main statistical parameters of Porosity and permeability data for each of flow units (HFU) shows HFU3andHFU1 have the highest and HFU5 and HFU6 have the lowest reservoir quality in the oil field. In order to cluster validity, silhouette approach was used to hierarchical and K-means clustering methods and finally hierarchical clustering was selected as the best method and the porosity and permeability data for both wells were included in the six clusters (RT). Comparison between Hierarchical clustering method with the flow units and microfacies indicated acceptable results for both methods.

In Kermanshah Radiolarites, Jurassic to late Cretaceous in age, three sedimentary facies including tempestite, pelagic mudstone, and radiolarian wackestone-packstone were identified. Each of these sedimentary facies accompanies by ichnofacies, which reveal the depth and energy of the environment. In the tempestites (including calclithite bed, flat pebble conglomerate and hummocky cross stratification) the trace fossils with Domichnia such asThalassinoides can be observed, which indicate the energetic conditions at the time of sedimentation. Trace fossils found in pelagic limestone units have Pascichnia and Fodinichnia. These Trace fossils includePlanolites, Chondrites and Helminthopsis, which indicate distalCruziana ichnofacies and show low energy condition. As a result of increasing of depth in siliceous deposits, the trace fossils with Pascichnia and Chemichnia includingScolicia, Helminthopsis, Gyrochorte and Chondrites, and Thalassinoides become dominant, which are indicative of the transitional zone between the distal Cruziana ichnofacies and the Zoophycos ichnofacies. The sedimentary facies and the present ichnofacies are indicative of the sedimentation of these deposits in the transitional zone between the middle and the outer ramp.

What referred as the Miyankalleh Peninsula and the Gorgan Gulf in the southeast of Caspian Sea is in fact a typical barrier island complex consisting of following major environments: 1) open sea, 2) Miyankalleh Barrier Island, and 3) Gorgan Lagoon. The major sub environments of this barrier complex are beach sand ridges, back barrier salt marsh; fresh water marsh; active, semi active, and stabilized sand dunes; and puffy grounds. The relics of sea- level changing and the major sedimentary structures of this complex are: different kinds of marine and nonmarine ripple marks, some kinds of rill marks, swash & backwash, long shore currents & rip currents, mud cracks, parallel and perpendicular beach bars, many traces of faunas on the stoss slope of sand dunes, and small bays. The form and development of the Miyankalleh Barrier Island Complex depend on the presence and combination of several factors such as high sands, high- energy storms, and long shore currents in a micro tidal, high amplitude wave dominated regime in a gentle slope of this beach. The Khozini channel, which was the way of connecting the Gorgan Lagoon to the Caspian Sea was the result of unsuccessful man made channel filled & abandoned quickly by long shore currents of the Caspian Sea. Chemical analysis and core studies of the Zaghmarz region indicate this area was part of the shallow marine Caspian Sea in the past, which subsequently occupied by non-marine sediments. The human interferences caused the intensive geomorphologic changes and converted the depositional bank to the erosional coast in the western part of studied area. This event resulted in retreating of more than 40 meters landwards of this coast and revealed an old wooden ship beneath the six meters beach sand ridges.

In evaluating the quality of the reservoir sandstone facies, clay usually has significant effect in reducing reservoir effective porosity, permeability as well as calculation accuracy of formation fluids saturation. There are several methods for identifying and measuring the amount of clay.In sandstone reservoirs, diversity of type and amount of clay minerals may change the capacity of cation exchange (CEC) measured in the reservoir rocks. The last parameter (i.e. CEC) can be an important criterion for zoning of reservoir based on the type of clay minerals. Cation Exchange Capacity (CEC) measurement is used as one of the subsidiary clay typing methods. This parameter is the ability of clay to absorb and release of cations in the surrounding solution, which has a specified range for each clay mineral. In cases of clay mixtures, CEC values tend toward the range of the dominant clay type of sample. In this study, cation exchange capacity of the clay minerals has been calculated in two wells of the Gonbadli Gas Field in the Shurijeh sandstone reservoir. First, CEC of 20 samples has been measured using Bower method and employing intelligent estimator based on neural network as well. Based on the petrophysical logs and laboratory results, an appropriate model was fitted to estimate this parameter in well interval. According to the CEC values of clay minerals, existing data classified into five categories including clean zone and zones of clay containing kaolinite, chlorite-illite, halloysite with two water molecules and montmorillonite. For this purpose Bayesian, Parzn and K- nearest neighbor (KNN) classifiers were used. Finally, the obtained results in comparison with the results of X-ray diffraction experiments (XRD) showed good agreement.

The Lake Urmia is the greatest hyper saline Lake in the world. This lake, located in Azerbaijan area, Northwest of Iran is an intra-continental sedimentary basin. Its area is about 6000 km2 with an average water depth of 6 meters. Hydrochemistry of the water resources of the basin showed mainly chloridic and sulfidic composition due to the geology of the surrounding areas and its variable lithology and Inlet water are supplied from the permanent and seasonal rivers. The hydrochemical investigations were carried out over a time period from 2007 to 2012 using previously published data together with newly collected water samples.120 samples were collected during 6 years. The analaysis results showed Na-Mg-Cl type of the brinefrom 2007 to 2010, which is comparable with the Great Salt Lake in the USA. The chemical composition of lake in 2007 showed the percentage of sodium is higher than Magnesium. In 2011 and 2012 water composition is HCO3<<Ca+Mg. That is, the path of brine composition on the Eugster and Hardie flow diagram has changed from row III2b (Na-Mg-Cl) to (Mg-Na-Cl) in 2011 and 2012 after halite crystallization and may finally result in Mg-Cl-SO4 brine type in the future. The Sodium to Magnesium ratio is 5.12 in 2007. However, this amount in 2011 is 0.68 and 0.56 in 2012. In future, with Increasing ofevaporation, the Magnesium to sodium ratio increases and chemical compositions of the brine in the north and south of the Shahid Kalantari Highway experience more difference.

The Santonian – CampanianIlam Formation is one of the major reservoirs of Bangestan Group in the Zagros petroliferous basin. In the Siri Alvand Oilfield located in the Persian Gulf this formation with a total thickness of 130 m, consists of limestone. In this study, microfacies, depositional environments, diagenetic processes and sequence stratigraphy of the Ilam Formaton in Siri Alvand oilfield was studied. Based on thin sections studies, 8 microfacies and 4 facies associations were identified that deposited in a homoclinal carbonate ramp environment. On the basis of petrographic studies, the main diagenetic processes affected these rocks include bioturbation, cementation, dissolution, dolomitization, stylolitization, pyritization and fracturing. The most important cement types in this formation are bladed calcite, fine equant calcite, drusy mosaic calcite, coarse blocky calcite and syntaxial calcite overgrowth. Sequence stratigraphic studies led to recognition of four third order depositional sequences in the Ilam Formation that all of them terminated to the type 1 sequence boundary. Finally, facies and diagenetic processes intensity were studied in each sequence.

This study is focused on the microfacies and facies associations in the 540 meter-thick interval of the Late Permian Upper Dalan reservoirs in the South Pars Gas Field using the petrographic studies, image analysis techniques and quantitative analysis of the constituting components.The petrographic studies led to the recognition of 15 microfacies that formed in four facies associations: peritidal, lagoon, shoal and off shoal.Due to the high frequency of the shoal facies in the Upper Dalan, those have been investigated in details. The relative sea-level changes during deposition of the Upper Dalan member were examined using the vertical microfacies and facies association’s variations. The main focus of this study is to investigate the microfacies variations and depositional environment evolutions in the Upper Dalan member in response to the relative sea-level changes. The frequency analysis of the facies revealed that during the Late Permian, a major fall has been occurred in relative sea-level recorded in the lower (K4 unit) and upper (K3 unit) parts of the Upper Dalan member. In these intervals, the facies change from ooid-bioclastic shoals to the alternative layers of shoal-lagoon-peritidal facies. As well, anhydrite precipitation and dolomitization are prominent diagenetic features, which are indications of climate change. The facies variations were used to reconstruct the relative sea-level changes during deposition of the Upper Dalan member in the South Pars Gas Field. As a result, two and a half third-order and 12 fourth-order cycles have been distinguished.

The Qom Formation is well exposed in Ashtian area (Central Iran). Pelecypoda of the formation in a stratigraphic section of west of Ashtian were examined in terms of paleontological and paleoecological criteria. In this section, the Qom Formation overlies the Lower Red Formation with a gradual contact and is disconformably overlain by Upper Red Formation. For the first time, the systematic studies of the fauna yielded four genera and two species of small pelecypoda. Common stratigraphic ranges of determinatedpelecypoda with the presence of coexistence foraminifera, give the age of Early Miocene (Aqitanian) for these layers. The distribution of the foraminifera in the studied area indicates that carbonate containing small pelecypoda of the Qom Formation were deposited in an aphotic zone of tropical to subtropical region.

The Nayband Formation in North of Isfahan includesfive Members: 1- Gelkan Member (marl and sandstone), 2- Bidestan Member (sandstone and reefal limestone), 3- Howz- e- Sheikh Member (marl and sandstone), 4- Howz- e- Khan Member (marl and reefal Limestone) and 5- Qadir Member (marl and sandstone). The biostromal limestones of Bidestan and Howz-e- Khan Members represent a typical known key bed in North of Isfahan. In Bidestan and Howz-e- Khan Members (NaybandFormation), coral reefs grow up and their distribution are significant in the biostromal limestone of Bidestan and Howz-e- Khan Members of Nayband Formation.Twelve genera and 31 species of Scleractiniancorals were recognized in thesereefal members. They included: Reimaniphylliidae, Margarophylliidae, Coryphylliidae, Cyclophyllidae, Astraeomorphidae, Pamiroseriidae, Stylophyllidae and Actinastraeidae families. According to the field observations and evidences, laboratory studies and analysis, measurements of the coral size and the destroyedepitechaof thecorals, it could beguessed that Scleractinian corals survive below the storm wave base (about 20 meters depth) but they tolerated many storms. Morphology of Scleractinian corals of Late Triassic sea (North of Isfahan) indicatesinadequate living conditions and high energy environment. Corals have major roleinreconstruction of Paleoenviromentofthe LateTriassic unitsofthe North of Isfahan (Nayband Formation) in Dizlusection.