نشریه رسوب شناسی کاربردی
پیاپی 17 (بهار و تابستان 1400)

The Garau Formation (Apthian – Cenomanian) is one of the hydrocarbon-generating formations in the Zagros Basin. Investing hydrocarbon potential of the Garau Fm., 14 samples were taken through the Nosoud water-transfer tunnel, NW Kermanshah. The samples were analyzed by selected from Rock- Eval 3 pyrolysis method. The results show that kerogen type III is the most abundant in the Garau Fm. According to the Tmax, the organic matter of Garau Fm. is thermally matured in the study area. The HI vs TOC values indicate a CD organic facies representing an oxidizing environment of plant organic origin in this formation at the study area. In terms of genetic potential, the Garau Fm. is a poor to relatively good source rock, but its hydrocarbon potential ranks poor. The vitrinite reflectance is more than 1.3 in the most samples, which indicates gas production stage that is also confirmed by Tmax more than 440 C°. Furthermore, thermal history model of the Garau Fm. in the study area suggests this formation entered to catagenetic stage in Paleogene and reached to high thermal maturity in late Neogene. The existing methane and carbon dioxide in the tunnel with a concentration of more than 870 ppm can be attributed to the generation of gaseous hydrocarbons according to the results of thermal modeling.

In order to determination of biozones, facies types and sedimentary model, the Posht Darband stratigraphic section of the Qom Formation with a thickness of 330 meters located in the northwest of Hamedan, structural zone of the Sanandaj- Sirjan, has been considered. On the basis of field observations, Qom Formation is composed of medium to thick-bedded limestone (Member a) and alternation of sandy limestone, sandstone and green marl (Member b). According to paleontological study, seventeen genera and nine species of benthic foraminifera and other skeletal components are introduced from the Posht Darband section and consequently, Lepidocyclina - Operculina - Ditrupa Assemblage zone has been recognized in the Qom Formation. Facies analysis (Variety in fauna features, fabrics, and sedimentary textures) has produced eight microfacies related to the four facies belts of tidal flat, reef, slope and open marine. Base on abundance in reef facies deposits including coral boundstone, algae and bryozoan, an open shelf is proposed for the Qom Formation. The vertical distribution column of the facies types (without considering the possible erosion phenomenon) suggests that the facies changes in member "a" are gradual, but in member "b" they were rapidly, with facies retrogradation and progradation.

The Fahliyan Formation in Arvand oil field has a low lithological diversity and including of limestone in the lower parts and dolostone in the upper parts of the reservoir. The goal of this study is determination of facies, depositional environment, diagenetic processes and their effect on the reservoir quality of this formation. Microscopic studies of 478 thin sections of cores led to the identification of 21 microfacies belong to 4 facies belts including tidal flat, lagoon, shoal and open marine. This study also revealed diagenetic processes including micritization, bioturbation, neomorphism, compaction, dissolution, cementation and replacement. In order to investigation of reservoir characterization, the effects of diagenetic processes and sedimentology used on the distribution of porosity and permeability. After studies of facies and diagenetic processes that affected these facies, eight petrophysical Rock Type, based on petrophysical classes of Lucia, were identified. Grainstone facies have the higher reservoir quality because of dissolution processes, packstone facies has good reservoir quality and the wackestone facies have lower reservoir quality.

The Kazhdumi Formation (Aptian-Albian) comprises the lowermost lithostratigraphic unit of the Middle Cretaceous in the eastern and central regions of the Zagros Mountain chain and one of the richest known source rocks in the world. To investigate facies and sedimentary environment as well as sequence stratigraphy analysis of the formation in the central Zagros, this study focuses on the Payon anticline surface section in Izeh zone and a subsurface section of the Ahwaz oilfield in the Dezful embayment. Field, laboratory and well logging data showed that the Kazhdumi Formation composed mainly of dark bituminous shales and thin-bedded carbonates rich in pelagic fauna with subordinate horizons of radiolarite, glaugonite and phosphate. This sedimentary succession deposited in a low energy and organic-rich intra-shelf basin which was limited to the southeast by the Fars Platform (Dariyan Formation) and extended into the Burgan delta (Azadegan Sandstone Member) in the south of Khuzestan. To the north, the Kazhdumi depression bounded by the Balarud Fault and separated from the Lurestan Basin (Garau Formation). The creation of the Kazhdumi deep marine basin and sedimentation of the organic-rich deposits are the result of a rapid increase in accommodation due to sea-floor subsidence along the preexisting Kazerun and Hendijan regional fault systems and eustatic sea-level fluctuations as well as the influx of siliciclastics. Deposition of organic-rich sediments of the Kazhdumi Formation coincides with the globally recognized Aptian and Albian Oceanic Anoxic Events (OAE1a and 1b).

Soil Erosion and Sediment Yield is one of the main environmental problems in watersheds of Iran. The purpose of this study is using MPSIAC model and application of GIS to minimize the probable errors in soil erosion evaluation and sediment yield in Eshghabad-Sule watershed. This area is located in the southwest of Quchan, and it has 81.365 km2 area and elongate form. This basin is located in Binaloud structural zone, and it has relatively thick sequence of volcanic and sedimentary rocks. Data layers of MPSIAC model are comprised of nine effective factors in erosion and sediment yield in the watershed that were obtained by digitalizing and classifying the basic information data in GIS program. The final erosion map was obtained from all information layers. The results of MPSIAC model indicated that 46.79% (3807.1751hec) was classified at IV class with high sedimentation and 53.2% (4329.3249 hec) was classified at class III of erosion category with medium sedimentation. Mean sediment yield was calculated as 5.04 and 2.844 ton/hec by MPSIAC model, respectively. The comparison of mean sediment in this watershed with mean data from the nearest hydrometery station is get acceptable results.

The Gurpi Formation (Late Cretaceous-Paleogene) has been considered as a cap rock and source rock because of its stratigraphic position between two important Bangestan and Asmari reservoirs. The purpose of this study is geochemical evaluation of the Gurpi Formation as a possible source rock at Poshteh section in Kabir-kuh structure, consist of hydrocarbon enrichment (quantity), kerogen type (quality) and thermal maturity of organic matter. The TOC content of 31 studied samples from the Upper Cretaceous deposits of Gurpi Formation ranges from 0.04 to 1.67 (average 0.32 wt.%) and 0.13 to 0.33 (average 0.22 wt.%) in13 studied samples from the Paleogene succession. Also, the S2 parameter varies between 0.02 to 6.66 (average 0.87 mgHC/grRock) and 0.03 to 0.26 (average 0.07 mgHC/grRock) for the Upper Cretaceous and Paleogene succession respectively, which means poor to fair hydrocarbon potential for Upper Cretaceous and poor for Paleogene deposits in studied section. The HI/OI and the S2/TOC diagrams indicate that the Upper Cretaceous deposits are mainly composed of type II to II / III kerogen, related to the suboxic marine environment, and the ability of oil and gas generation. However, the Paleogene succession is mainly composed of type IV and III kerogen, deposited in oxic environment and has no hydrocarbon generation potential. The determined organic facies for the Upper Cretaceous succession range C to D and for the Paleogene succession range B to C and C. Maturity indicator parameters of PI and, Tmax reveals oil generation window for the Gurpi samples in the studied area.

 In this research Sarvak Formation from paleological point of view in Darian section, north east of Shiraz (folded Zagros) have been investigated. The Sarvak Formation with 200 meters thickness is mainly composed of dark gray massive limestone in the lower part and light gray in the upper part of the studied section. The identified foraminifera based on morphology and environmental conditions have been classified in eight morphogroups which consists of 6 benthonic and 2 planktonic foraminifera morphogroups. These morphogroups have been used for interpretation of relative depth of basin. Moreover, the change and differences in abundance and distribution of foraminifera in the studied section indicate some fluctuations of depth in sedimentary basin. Thus, in the lower part of section due to high abundance of planktonic foraminifera the depth of basin fairly is high, then with high abundance of benthonic and decrease or absence of planktonic foraminifera depth have decreased. After that in the middle of section the depth a little increased and finally in the most of middle and upper parts of succession because of increasing the abundance of benthonic and lack of planktonic foraminifera depth of basin have been decreased. So, the depth of basin in middle and upper parts to compare with the lower parts of studied section, could be suggested a shallow water environment.

Tirgan Carbonate Formation in Kopt-Dagh structural zone is an important karstic formation which contains significant water resources. Numerous water wells have been drilled in this formation. They have very different discharges. Ninety (90) thin sections, geophysical logs, well discharge changes, karst morphology have been studied. The karst development potential of each rock unit of this formation has been studied in this area, which depends on the sedimentary environment, diagenesis and siliciclastic sediment. In this region, Tirgan Formation can be divided into three limestone rock units and two limestone-marl rock units. This formation has been deposited in a homoclinal ramp and four sedimentary belts of tidal, lagoon, shoal to the open sea and twelve micro-facies have been identified. Twelve microfacies were identified. Compaction, stylolitization as an effective diagenetic factor is reducing from the base to the top of the formation and dissolution is increased. Siliciclastic deposits, quartz and shale decreased and rate of carbonate deposition and the diversity of allochems have increased from the base to the top. These events, in principle, significantly increased the potential for karst development. There are varieties of large and Small-scale karst features such as sinkholes, dry valleys, caves, karren and grikes in Upper parts of formation. Higher discharge of water wells (60 l/sec) and their continuous discharge, higher transmissivity (1037 m2/day) in the upper rock unit of Tirgan Formation shows that, this rock unit has the greatest potential for karst development and developed later.

Soils are discontinuous cover at the surface that may be composed of rocks and sediments in situ or by material transport. Heavy metals are one of the most important soil pollutants that can have a major impact on the health of living things and, above all, humans. Heavy metals, which enter the human body, can accumulate in the tissues and affect the nervous system and circulation. These metals also impair the normal functioning of the internal organs or may be auxiliary to other diseases. Elements such as mercury, lead, cadmium, chromium, nickel, zinc, selenium and the like are elements that are highly resident in the soil and have low mobility, so they may remain in the soil for many years. Such contaminants in the soil are caused by the addition of sludge, phosphate fertilizers, atmospheric sinks, color wastes and smoke from natural fuels, coal and other sources. Numerous studies have been carried out on the distribution of heavy metals in various soils such as urban, industrial, etc. Considering the importance of heavy metal contamination in soil and its effect on the health of living organisms, especially humans, this study was conducted to evaluate the concentration and contamination of heavy metals in soils north of Fereydoon Shahr (Isfahan province) using environmental indices; Geoaccumulation index, pollution load index, enrichment factor and pollution index were performed. The spatial distribution of heavy metal concentrations in the study area is also investigated.

The outcrops of the Sarvak Formation of the Khartu and Rashtalu anticline in southeastern Zagros have been studied of biostratigraphy, paleoenvironment and sequence stratigraphy. Six biozones were identified in Sarvask Formation in studied area (Middle Albian to Upper Cenomanian). Based on field observations, three stratigraphic units can be distinguished in both sections. Five facies were identified in ten microfacies in four facies belts. Carbonate sequence of the Sarvak Formation in the sections in a ramp (inner, middle and outer ramp) that includes lagoon, barrier, front barrier and open marine belts. Tectonic processes and the location of the sedimentary basin and the rate of entry from outside the basin on the ramp have been affected. Three third-order sequences have been identified, which have decreased to the upper basin depth. So that the diversity of habitats in the environment of Sarvak Formation was higher in Rashtalu section, while the fossil diversity in Khartu section was less.

The Sarvak Formation at the age of Late Albian-Middle Turonian is the most important carbonate reservoir rock in Abadan plain area in the southwest of Iran. The carbonate rocks of this formation have different and complex reservoir properties due to their tolerance to different diagenetic conditions and environments. This formation in the Darquain oil field mainly consists of white to cream limestone with thin interbedded of cream-colored argillaceous limestone and shale. The purpose of this study is to identify facies, interpret the sedimentary environment, identification of diagenetic processes, and their effect on the quality of the Sarvak reservoir in the Darquain oil field. For this reason, about 600 thin microscopic sections belonging to cores of wells No. 32 and 33 of this field were studied. Widespread laboratory studies show that the Sarvak Formation consists of 9 facies associated with a homoclinal carbonate ramp platform. The most important diagenetic processes in the Sarvak Formation are cementation, dolomitization, dissolution, mechanical and chemical compaction, micritization, and fracturing, which all occurred in marine, meteoric, and burial diagenetic environments. The porosity of the Sarvak Formation in the Darquain oil field is about 10% to 15% and the permeability is variable between 0.1 to 100 milliDarcy. Based on the available evidence, the reservoir quality of this formation is generally good.

Dashkasan village is in the southeastern part of Kurdestan Province. The purpose of this study is to determine the contamination of As, Pb, Ni, Zn and Cr by mining activities in the soil of the village of Dashkasan. The results of physicochemical analysis of soil samples showed that the soil pH is in the range of the neutral soils. In terms of cation exchange capacity, it is approximately in average of 15.16 mEq, and the weight percentages of organic matter in the samples are in average of 4.73. Granulometry showed that in general the soils of the region are medium to fine grained and in the range of sand, silt and clay and are often in the range of mud sand. They are poorly sorted and have low content of calcium carbonate. Environmental indicators were used to assess the amounts of soil contamination. The results of the contamination factor in the area of Dashkasan village showed that there is pollution in the most samples. The highest contamination factor is related to the element lead (9.80). The highest enrichment coefficient is related to the element lead (3.47). The results of geo-accumulation index of lead showed that some samples are in the high-contaminated to very high-contaminated group. Biohazard factor and biohazard potential showed that arsenic and lead the range of environmental risk is very high in the samples. In all soil samples collected in the area of Dashkasan village, the pollution load is higher than 1, which indicates that the study area has been affected by abnormal concentrations. On the basis of anthropogenic factor, the highest contamination is related to Pb.

The Asmari Formation is a thick carbonate sequence in the Zagros Foreland Basin that was deposited during the Oligo–Miocene. In order to conduct biostratigraphic studies, microfacies and to interpret the depositional environment, the Makhmal Kuh section in the Lurestan province located in west of Zagros was investigated. The section is 85 m thick, consisting of alternating layers of thick limestone interbedded with thin-layer limestone. Based on biostratigraphic studies, 12 genera belonging to 7 families of foraminifera were identified in the studied section. In this section, two fossil assemblages and 12 microfacies were identified based on the Rupelian-Aquitanian foraminifera distribution patterns. The fauna assemblages conform to the world standard zones. The study of microfacies indicates two different sedimentary sub-environments including lagoon and open sea in the studied section. These depositional sub-environments of the Asmari Formation are compatible with the inner, middle and outer ramp parts, formed under a Mesophotic, Oligophotic and Aphotic conditions in a homoclinal ramp.