Aghajari Formation Research Articles

The results of Punch, Brazilian, and Uniaxial compressive strength experiments on sulfate rocks with complex mineral composition

Punch testing with different approaches has been used to know the compressive or tensile strength of rocks. In this research, by performing UCTs, BPTs, CPTs, BTs experiments and petrological studies, for the first time, the correlation between the results of these experiments and the mineral composition of sulfate rocks was investigated. The used rock blocks are mainly collected from the Gachsaran Formation outcrops at the four under construction reservoir dam sites (as well as from two points of the Aghajari Formation) in Iran. The regression analysis was used to study the correlations between UCS with block punch index (BPI) and cylindrical index (CPI) and Brazilian tensile strength (BTS) as well as BTS and CPI-BPI. By extracting 254 correlation equations, it was found that if the rock samples were taken from a specific geological point, the predominant correlation relationships were linear and with high determination coefficients, and therefore, the results of BPTs and CPTs can be used to predict compressive strength and tensile strength of rock with the same high reliability. In this study, for different mineral compositions of sulfate rocks, while presenting specific correlation relationships, the converting factors of BTS-CPI-BPI to UCS and CPI-BPI to BTS are presented.

Risk assessment of abnormal pressure zones with a focus on shallow gas pockets based on surface gas logging data and statistical relationships

The assessment of alterations in hydrocarbon components preserved in reservoirs is important for oil field management and drilling procedures. Drilling fluid analysis yields valuable insights into the reservoir fluid. This study focuses on identifying and quantifying shallow gas basins in the Azadegan oil field. Risk assessment of abnormal pressure zones with a focus on shallow gas pockets based on surface gas logging data and statistical relationships is also a key aspect of this research. Shifts in the C1 gas ratio to other gas components signify a notable peak in the Asmari Formation. Consistency among various wetness (Wh), balance (Bh), and character (Ch) indices suggests that the Aghajari and Gachsaran formations potentially harbor gas and contain some heavy or residual oil with limited production potential. However, the Asmari Formation shows the potential for natural gas production, while the Gurpi Formation has the potential for wet gas or condensate. Pixler parameters were computed and plotted to affirm the results of other parameters. The investigation of stratigraphic columns for component changes and lithology reveals that lithology plays a pivotal role in preserving valuable fluids. The upper section of the Aghajari Formation, primarily composed of shale-evaporite horizons, exhibits lower frequency compared to its lower part. The Gachsaran Formation displays an exceptional ability to preserve components in anhydrite sections. Although Asmari has a high accretion ratio, the Chilean calcareous sandstone horizons are more prominent in the upper part of the Gurpi Formation. The structural model includes humpback microstructures as controls for shallow gas pockets and component accumulation. Evaporite and shale layers significantly influence the movement of these components across different horizons. The 3D model illustrates migration from the Gurpi Formation to the Aghajari Formation, as both formations serve as sources due to the propagation paths leading to the Pabdeh and Gurpi Formations.

Age of folding in NW Lurestan arc across the Khanaqin fault by magnetostratigraphy on Aghajari growth strata, Zagros folded belt

The timing of deformation and the age of sediments in foreland basins are key information for reconstructing the tectonic history of orogenic belts. This study, utilized magnetostratigraphic techniques to determine the ages of ∼ 2.5 km-thick strata within the Zagros folded foreland basin in the flank of the NW-SE-trending Emam Hassan anticline, located above the N–S-trending Khanaqin blind basement fault. This fault separates the Lurestan arc in Iran from the Kirkuk embayment in Iraqi Kurdistan. These ages were combined with a detailed structural study to establish the timing of folding and integrate it into the regional framework of the Zagros folded belt. Magnetostratigraphic results indicate a Serravallian age at ∼ 13.4 Ma for the stratigraphic boundary between the Gachsaran Formation and the pre-growth Aghajari Formation, whereas the base of the Aghajari growth strata is Tortonian age (early Late Miocene) at ∼ 10 Ma. The mean sediment accumulation rate for the Aghajari Formation is ∼ 44 cm/kyr, with short peaks reaching up to 90 cm/kyr. Linear extrapolation of these rates proposes a younger age than ∼ 6.5 Ma (Messinian) for the base of the unconformable conglomerates of the Bakhtyari Formation. The Emam Hassan folding and related Gachsaran diapirism began ∼ 10 Ma and continued for at least 3.5 Myr until ∼ 6.5 Ma, coevally with the deposition of ∼ 1.3 km of the upper Aghajari Formation. Regional synthesis reveals that multi-detachment folding within the Lurestan arc propagates in-sequence towards the foreland. Although not the central focus of this study, our results, combined with the regional structural understanding, illustrate the potential 3-D structure at the depth of the seismogenic Khanaqin Fault, the source of the 2017 Mw 7.3 Sarpol-e Zahāb Earthquake.

Artiodactyl footprint Pazhanipeda kiyani ichnog. ichnosp. nov. From Miocene Agha Jari Formation, Gotvand area, Zagros Mountains, SW Iran

ABSTRACT Zagros Mountains in the southwest Iran was created by the closure of the Neo-Tethys and collision of Arabian and Eurasian plates. The Fars Group (Miocene to Pliocene) formed during this collision. The Agha Jari Formation (upper Miocene- lower Pliocene) is uppermost rock unit of the Fars Group, which has high potential for terrestrial vertebrate ichnology. This formation mostly deposited in the continental environment and a section of the formation studied in the east Gotvand, north Khuzestan province, southwest Iran. Agha Jari Formation, includes alternations of sandstone, siltstone, and marl in red to brown colour layers in the studied section. Numerous vertebrate footprints have been reported from the middle part of the formation in Gotvand section, among which artiodactyl footprints are abundant and diverse. Re-examination of artiodactyl footprints led to the discovery of a new ichnogenus and ichnospecies, Pazhanipeda kiyani, characterised by small-sized didactyl hooves, asymmetric and gracile imprints, and a wide interdigital angle. Based on the comparison of size, morphology and asymmetry of digit imprints with artiodactyl hooves, goats were considered as track makers of Pazhanipeda kiyani.

Evaluation of Iranipeda abeli (Avian track) from the Zagros Mountains, SW Iran: re-examination of the original material and overview of primary sources

ABSTRACT A slab with three tetradactyl avian footprints was excavated from the Agha Jari Formation (Mio-Pliocene) in the Zagros Mountains, southwest Iran, in the early last century and named as Urmiornis abeli. The name Urmiornis had been used for the didactyl bird fossil and ichnogenus name was later revised to Iranipeda. Validity of Iranipeda abeli has been discussed by authors in recent decades, and revision of the original material is necessary. Based on re-examination the holotype I. abeli reveals that this name is valid and it differs by long hallux, separate digit imprints and size of lateral digit II and IV traces with other large wading bird footprints. Iranipeda include three ichnospecies: I. abeli and I. millumi and I. intermedia by emended diagnosis of Iranipeda. Ciconiidae is the nearest track-maker candidate for Iranipeda. I. abeli type specimen has been collected from the lower part of the Agha Jari Formation and based on lithostratigraphic position and radiometric data, it is of Late Miocene age.

Magnetostratigraphic Age Control of the Timing of Tectonic Deformation and the Shifting Depositional Environments in the Dezful Embayment, Iran

AbstractThe timing of tectonic deformation in the Zagros foreland basin provides important information about the tectonic propagation process driven by the Arabia‐Eurasia convergence. The chronology of growth strata is one of the most important methods to delimit the history of folding and thrusting within the foreland basin. In this study, we report integrated analyses of sedimentology, magnetostratigraphy, and biostratigraphy of Miocene strata in the Dezful Embayment in the SW Zagros foreland basin. The new results indicate that deposition of the northern limb of the Gach‐e Moh Anticline was between 14.6 and 8.6 Ma; that includes the Upper Gachsaran Formation (14.6–13.8 Ma), the Mishan Formation (13.8–12.8 Ma), and the Agha Jari Formation (12.8–8.6 Ma). Based on magnetostratigraphic and sedimentary evidence, the transition from marine to non‐marine was at ∼12.8 Ma. Analysis of temporal lithofacies‐stacked patterns shows there were seventeen transgression‐regression cycles during the Middle Miocene Climatic Transition with a ∼100‐Kyr Earth eccentricity cycle, suggesting that the cyclic marine transgressions and regressions were mainly driven by eustatic sea level fluctuations; but tectonic‐induced basin subsidence also contributed marine transgressions in the Upper Mishan Formation. The final seawater retreat was at 12.8 Ma driven by both the global eustatic sea level drop and the enhanced south‐westward progradation of sediments eroded from the High Zagros. The base of the growth strata in the footwall of the Mountain Front Fault was at ∼11 Ma, suggesting that tectonic deformation caused by the Arabia‐Eurasia collision had propagated to the Dezful Embayment by that time.

Improvement of roller cone drill bit design by using finite element method and experimental study

An approach for increasing the rate of penetration (ROP) of roller cone bits is presented. The proposed approach is based on 3D finite element method (FEM) simulation as well as field test results that were carried out on the Aghajari formation located in the southwest of Iran. In order to reduce the operation time by improving roller cone bit design, the FEM simulation of the complex nature of the contact between the roller cone bit and the formation was performed and the obtained results were compared with the field test data. Results were employed to improve the geometry of the bit profile. Based on the improved design, a roller cone bit was manufactured and employed in the field experiment to assess the performance and to verify the numerical simulation. The results show a positive effect of the improvements on the ROP which leads to a considerable reduction in drilling costs. [Received: September 15, 2021; Accepted: February 26, 2022]

Vertebrate footprints from the Agha Jari Formation (late Miocene-Pliocene), Zagros Mountains, and a review of the Cenozoic vertebrate ichnites in the Persian Gulf region

Vertebrate footprints from the Agha Jari Formation (late Miocene-Pliocene), Zagros Mountains, and a review of the Cenozoic vertebrate ichnites in the Persian Gulf region

Pliocene growth of the Dowlatabad syncline in Frontal Fars arc: Folding propagation across the Zagros Fold Belt, Iran

Abstract The integration of biostratigraphy, strontium isotope stratigraphy, and magnetostratigraphy allowed for the precise dating of the >3.0-km-thick marine to non-marine foreland sedimentary succession within the Dowlatabad growth syncline along the Frontal Fars arc in the Zagros Fold Belt that extends from eastern Turkey to southern Iran. This area was the missing link to complete the dating of syntectonic deposits in the Fars arc and quantify the migration of sedimentary belts as well as the propagation of folding across the entire Mesopotamian foreland basin. Both are essential for defining the interplay of basin evolution and sequence of folding. Deposition of the foreland marine marls in the Mishan Formation started at ca. 11.5 Ma. The transition to a non-marine basin infill occurred at 4.9 Ma by the progradation of thick fluvial deposits of the Aghajari Formation with a fast accumulation rate of 63 cm/k.y. The beginning of growth strata deposition and thus the onset of folding in the Dowlatabad syncline is dated at 4.65 Ma. The first appearance of carbonate conglomerates sourced from the Guri limestone at 2.8 Ma marked the progressive dismantling of the nearby growing anticlines. The tectonic deformation in the front of the Fars arc was active for at least 2.85 m.y. and ceased at 1.8 Ma before the deposition of the discordant and slightly folded Bakhtyari conglomerates characterized by a clast composition derived from the Zagros hinterland. The compilation of magnetostratigraphic ages reveals that both the migration of the Aghajari-Bakhtyari sedimentary belts and the propagation of the folding front was in-sequence toward the foreland at a rate close to 20 mm/yr in the Fars arc and 15 mm/yr in the Lurestan arc, in the last 20 m.y. These high rates of folding propagation are about one order of magnitude larger than age equivalent shortening rates (∼4 mm/yr in Fars arc and ∼2 mm/yr in Lurestan arc) and thus imply an efficient detachment level at the base of the deformed Arabian sedimentary cover. Numerical experiments on both the cover and basement sequences are designed to test the influence of inherited basement structures on the deformation propagation within the cover sequence, providing clues on the partly coeval in-sequence deformation of the Zagros Simply Folded Belt and the local out-of-sequence Mountain Frontal Fault system as illustrated by regional and local geology.

Introducing tourist land attractions of Aghajari Formation in Genaveh, South Dezful Basin, Iran

Iran is one of the five countries in the world with the highest climatic diversity, in the word, in which the existing tourist and natural attractions have a high potential for the development of non-oil revenues. Accordingly, the southern regions of Iran with prominent features in formations belong to different geological periods. Differences in sedimentological features of these formations, especially differences in lithology, have led to the formation of extraordinary geomorphological features that are of great importance in attracting tourism. In these areas, especially the Zagros sedimentary basin, which has expanded with a northwest-southeast trend, various geomorphological structures that are important in the growth of the tourism industry are abundant and pristine and unknown. Genaveh port city of Bushehr province in Zagros basin located in Dezful basin with various Neogene formations and sediments (especially Aghajari Formation) and Quaternary, has special topographic and morphological structures such as mountain ranges, hot springs, sea, etc. There is a high potential of tourist attractions that have remained unknown until now. Most of the studied geomorphological features are located in Aghajari detrital deposits (molasses) that the placement of resistant (sandstone) and unstable sequences (marl and siltstone) leads to the formation of special geomorphological structures in this region. This study examines and introduces the pristine, unknown and natural geotourism landscapes of this region. These diverse geological features, along with rich cultural heritage, have provided the basis for tourism development and the creation of geoparks, which in turn are effective in the development of regional economy and rural areas.

Prediction of Uniaxial Compressive Strength and Modulus of Elasticity in Calcareous Mudstones Using Neural Networks, Fuzzy Systems, and Regression Analysis

The uniaxial compressive strength (UCS) and modulus of elasticity (E) are two important rock geomechanical parameters that are widely used in rock engineering projects such as tunnels, dams, and rock slope stability. Since the acquisition of high-quality core samples is not always possible, researchers often indirectly estimate these parameters. In the present study, prediction of UCS and E was investigated in calcareous mudstones of Aghajari Formation using multiple linear regression (MLR), multiple nonlinear regression (MNLR), artificial neural networks (ANN), and adaptive neuro-fuzzy ınference system (ANFIS). For this purpose, 80 samples from calcareous mudstones were subjected to the point loading, block punch, and cylinder punch tests. The performance of developed models was assessed based on determination coefficients (R2), mean absolute percentage error (MAPE), and variance accounted for (VAF) indices. The comparison of the obtained results revealed that, among the studied methods, ANFIS is the most suitable one for predicting UCS and E. Moreover, the results showed that ANN and MLNR respectively predict UCS and E better than MLR and a meaningful relationship between the observed and estimated UCS values in all regressions.

Folding, thrusting and diapirism: Competing mechanisms for shaping the structure of the north Dezful Embayment, Zagros, Iran

AbstractDifferentiating compressional growth strata from halokinetic sequences is not straightforward in foreland fold‐and‐thrust belts where compressional and diapiric processes were coeval. Although there are numerous studies on the role of salt layers in fold‐and‐thrust belts, very few focus on syntectonic evaporites where they are thick enough to develop diapirism. The tectonic structures of the northern Dezful Embayment, along the footwall of the Zagros Mountain Front Fault, show a complex evolution interpreted in this study by the concurrence of folding, thrusting and pre‐ and syn‐shortening diapirism of the lower Miocene Gachsaran evaporites. We explore this tectonic–diapiric–sedimentary interplay by combining field studies and remote‐sensing mapping, detailed stratigraphy and sedimentology, high‐quality seismic data, and step‐by‐step balanced tectono‐sedimentary restorations. Initial diapirism occurred soon after the deposition of at least 1.5 km thick Miocene Gachsaran evaporites during the sedimentation of up to 5 km thick Aghajari, Lahbari and Bakhtyari formations, which display syntectonic mixed growth strata and halokinetic sequences. These sedimentary sequences filled salt‐related minibasins, from which the Azanak Minibasin is the deepest, limited by growing salt walls and salt anticlines (Azanak thrust‐weld and the Saland–Lali anticline). Palaeocurrents and clasts compositions document fluvial diversions and exposure and erosion of Gachsaran evaporites along the active salt walls. Although, by further shortening, the precursor salt walls squeezed and reactivated as thrust‐welds structuring a duplex of overriding minibasins. During the deposition of the middle‐late Miocene Aghajari Formation, Kazhdumi and Pabdeh source rocks were buried to oil‐expulsion depths, and Sarvak and Asmari reservoirs were mildly folded in large and open anticlines. The Gachsaran system in the northern Dezful Embayment is collated with the structures of preshortening Hormuz salt and syn‐shortening Fars salt to highlight the important role of these ductile units in the tectonic evolution of the Zagros fold belt that is compared to syn‐compressional salt‐related Pyrenees, Carpathians, Sivas and Kuga fold belts.

The impact of active faulting on the geotechnical properties of the Upper Gotvand Dam, southwest Iran

Fault movement in dam foundations is an earthquake hazard feature that may lead to severe structural distortions. Such movements may manifest as rock failures, crushing and displacements of rock masses. Faults with surface breaking and potential block movements are also of considerable interest in the issue of dam safety. The Upper Gotvand Dam is the highest rock fill dam in Iran which was constructed over the Karun River in the Khuzestan Province, southwest Iran. Its location in the Zagros active belt, the most active seismotectonic zone of the country, makes it prone to abutment instability and potential seepage through the foundation and abutments. The dam foundation is on the sandstones of the Agha-Jari Formation while the abutments are composed of rock mass of the Bakhtyari Formation. The right abutment of the dam is highly fractured and displaced due to action of the Pir-Ahmad active fault.. Geotechnical sections along the dam axis and across the right abutment indicate four strike faults near the right bank as well as sharp changes in the dip of bedding along the dam axis. The Agha-Jari layers are tightly folded beneath the dam axis with a 30° inter-limb angle forming a chevron fold. The geomechanical classification of the outcropped rocks is in the range of weak to very weak. The whole region is affected by an N-S basement tectonic lineament introduced in this research as the Lali-Ahvaz trend. Variations in the geotechnical properties of the dam site are mostly due to the movement of the Pir-Ahmad Fault. The activity of the fault should be re-assessed for future operations and producing dam maintenance plans as fault activity could diminish future dam safety.

Evolution analysis of miocene channels and faults in offshore area of Strait of Hormuz (Eastern part of Persian Gulf) using seismic meta-attributes

Tectonic movement of Oman Orogeny and Zagros Orogeny and Hormuz Salt triggering are accompanied with presence of complex structures in Strait of Hormuz sedimentary basin. Geological model Obtained via multi-attribute analysis and the extracted geobodies are used to define type and relative age of channels and faults in offshore area of Strait of Hormuz (Eastern part of Persian Gulf). In this study, channels and faults were mapped using meta-attributes by a neural network. The probability volume helps more accurate extraction of channel bodies and fault planes. The channel bodies and fault planes can be revealed more continuous with dominant edges and subtle flexures as obtained results based on meta-attributes. Considering this approach, three distinct channel types (small (S), median (M) and large (L)) are illustrious in different substrates based on various flow powers that extended from West to East. Normal fault band with the NorthEast-SouthWest trend and few dip toward the East, whereas faulting may occur during late Mid Miocene- Early Upper Miocene. The main channels (M) and (L) are located on both sides of the fault in lower and upper deeps within Mid Miocene Mishan Formation sediments, while channels (S) located away from the fault within Upper Miocene-Pliocene Aghajari Formation sediments. Processes of sediment transport are very different in Miocene Aghajari and Mishan Formations as form of meandering channels and their slopes are dissimilar. Sediment supply has led to changing geometry of meandering channel due to effects of sea-level change. Based on seismic attribute study, slope and form of channel (M) has been affected by later faulting, whereas slope and form of channel (L) operated independently. Presence of meandering channel (M) with lower slope and higher sinuosity ratio in comparison with meandering channel (L) suggests that channels located in upper horizons of sedimentary basin could be consider as an appropriate place for hydrocarbon accumulation in intra Mid Miocene Mishan Formation. Furthermore, revealed channels within Mid Miocene Mishan Formation sediments are bigger than the channels within Upper Miocene-Pliocene Aghajari Formation. Reservoir properties study suggests that channel filled sediments are relatively porous than their backgrounds, producing relatively higher reservoir potential based on the integrated analysis of acoustic impedance and frequency content.

Petrophysical Evaluation and the Effect of Shale Layers on Net Pay Zone Thickness in the Marun Oil Field, Iran

The Marun oil field is situated on the eastern part of Zagros, Iran. Aghajari Formation is cropping out on the surface. The Asmari formation, the Bangestan and Khami Groups are the Main reservoirs in this field and Asmari formation is the most important reservoir. Dolomitic carbonates are dominant lithology in the study well. Increasing of shale Layers in different layers caused to decrease of brittle property and this condition had investigated by petrophysical evaluation. According to this research, near to 29 percent shale has mixed with sandstone rock units in the study well which is comparable with maximum porosity there. Because, sandstone layers have shown the best porosity (near to 26 percent) in the study well. Also, good rocks based on water saturation and porosity are situated in sandstone units and poor rocks have existed in the limestone-dolomites. Therefore, facies changes in the Asmari formation can explain the observed variations in reservoir quality in the study area.

Evaluating Sediment Production Caused by the Lithology of the Geological Formations in Sedimentary Basins (Case Study: Lali Area, Khuzestan, Iran)

As sediments are produced and accumulated in sedimentary basins especially in dams’ reservoirs and they highly affect the reservoirs life span, it is essential to scrutinize the effect of lithology and types of geological formations of an area on the life span of reservoirs specifically from the viewpoints of the erodability of these formations due to their lithology type. Lali area, Khuzestan, Iran and the water catchment of the intended area (based on geological situation and Taraz dam situation) are placed in the sedimentary-structural zone of the folded Zagros. The method of this research is based on analyzing the topography and geology maps and field work in order to identify the lithology of the geological formations. In fact, the amount of its erodability has been characterized by the type of the geological formations. The current research aims at putting the geological results, lithological data of the formations types and the outcrop of the soil-lithological units together in order to evaluate the sedimentary and erosive factors of these units and precisely identify the area’s geological formations to remove the ambiguities in this issue. Studies indicate that formations made of looser gypsum and marl like Pabde-Gurpi and Gachsaran are exposed to more sedimentation and erosion than the formations made of compacted lime stone and conglomerate with silica-lime cement such as Bakhtiary and Asmari formations and the sand stones of Aghajari formation reveal the moderate to high resistance. Thus, the lithological identification of the formations, the type of sediments and their looseness and hardness contribute to detect the amount and type of deposits entering into the dam reservoir. The type and amount of these transported and deposited sediments are assessed to predict more suitable optimized ways to exploit dams’ reservoirs.

Active surface cracking in Aghajari Formation of the Azar oil field, Zagros, western Iran

A very rare case of deformation is described in which surface cracks are being developed in a period of few months over an area of ca. 55 km2 in the Late Miocene–Early Pliocene Lahbari Member of Aghajari Formation outcropped in the Azar oil field of western Iran. The cracks are unique because of their activity and their relation to regional tectonic stress field, and not to shallow local processes. The cracks are almost parallel to the NE–SW shortening direction deduced from local folds, and are of almost pure tensile nature. Strike-slip faulting in the area is also in kinematic concordance with the cracks, which show a NW–SE extension direction. Erodibility of the surface geological materials and their downwashing by surface water is affecting the surface morphology very quickly. It is suggested that movement of incompetent underlying Middle Miocene Gachsaran Formation on a lateral ramp of the Zagros Foredeep Fault, and regional active shortening of the sedimentary sequence are responsible for development of the cracks. Construction of the Mohr diagram predicts that maximum depth of the tensile cracks is ca. 220 m. Weak mechanical nature of the Lahbari Member and transient pore pressure are major contributing factors for the crack development. Study of these active cracks may help to better understand the process of active and past fracturing in foreland fold thrust belts.

Shallow gas accumulations and seepage in the sediments of the Northeast Persian Gulf

Shallow gas accumulations and gas seepage may indicate deeper hydrocarbon reservoirs. Sonar and high resolution seismic recordings were carried out to obtain gas migration and accumulation below seabed in Northeast Persian Gulf. Results revealed some structures and reflectivity effects, for example few pockmarks, gas seepage, and other surface structures in sonar and seismic data. Most of the features observed on seismic data were located at depths between 5 and 10 m (sub-sea bed) that include acoustic blanking and turbidity, gas packets, gas chimneys, and enhanced reflection. Most of the gas is accumulated on young and thin parallel layers, but the presence of acoustic effect in Aghajari Formation indicates that the origin of the gas accumulation in shallow strata may be located in a deeper reservoir.

The Aghajari (Upper Fars) Formation in the Folded Zagros Zone, Iran: Insights to Identify Facies, Architectural Elements, Fluvial Systems, Petrography and Provenance

Abstract:The Aghajari Formation, called also the Upper Fars, develops throughout the Folded Zagros Zone and its thickness in the type section in southwest of Iran is 2966 meters. To analyze the sedimentary basin of this Formation, lithofacies, architectural elements and petrofacies of the related deposits in a section in southeast of Sarvestan in Fars Province of Iran with a thickness of 2221.45 meters were examined. Microscopically studying thin sections, the petrography and the occurrence of the deposits were determined. In this section, 16 lithofacies, 10 architectural elements and 2 sandstone petrofacies were identified. The lithofacies were divided into two major and minor groups, in which the major lithofacies consist of coarse‐grained (Gh, Gp, Gt and Gm), medium‐grained (Sh, Sp, St, Sl, Sm, Sr and Ss and fine‐grained ones (Fm, Fl and Fsm), and the minor lithofacies were evaporative and mixed silisiclastic‐carbonate. The identified architectural elements are CH, SB, GB, LA, DA, CR, CS, LV, LS, CH (FF) and FF. By combining evidences from facies analysis and architectural elements together, the Aghajari Formation was divided into three parts in which the related sedimentation environments, from top to bottom, are gravel, gravel‐sand and fine‐grained meandering river respectively. There have also been playas and shoreface in the lower part. Based on petrography, the sandstones of this formation were classified into two groups: litharenite and sublitharenite. The origin of these deposits (sandstones) was appointed to the recycled orogeny and the source of quartz is low and medium to high metamorphic rank. Using the field evidences, the paleocurrent direction was achieved indicating the direction of the paleocurrent from northwest to southeast at the time of deposition. It is hoped that these data can be used in the interpretation of the basin and reconstruction of the paleogeography in the local and regional scales.

Sedimentology and palaeogeography of conglomerates from the Aghajari Formation in Zagros Basin, SW Iran

Conglomerates, the lithified equivalent of gravels alternate with sandstones and mudstones in the upper parts of the Aghajari Formation in the Zagros Basin, southwestern Iran. The thickness of the Aghajari Formation in this studied area is 2221 meters. Polymictic conglomerates form excellent outcrops in the central parts of the study area. From the view of its (coarse) clast composition, the Aghajari Formation consists of two types of conglomerates: 1) limestone-chert clast-supported conglomerate (LCCSC) and 2) limestone clast-supported conglomerate (LCSC). The chronological and spatial relationships between these conglomerates are not easily determined caused by existence some thrust faults at their approximate boundaries. In the vertical succession, various lithofacies were recognized; their textural characteristics and sedimentary structures suggest a non-marine depositional system as they match with standard lithofacies of meandering rivers. Epirogenic movements in the region started in the Oligocene, showed by a polymictic conglomerate beds at the Jahrum-Asmari Formation boundary. These movements then changed to orogenic ones with the depositioning gravelly alluvium now known as Aghajari (upper parts) Formation.