نشریه رسوب شناسی کاربردی
پیاپی 3 (بهار و تابستان1393)

Zarivar Lake، located west of Marivan city، Kurdistan Province، is an important freshwater lake in Iran. This study determined the concentration، origin، and distribution of heavy metals (Ni، Co، Mn، Ti، and V) in Zarivar Lake bed sediments. The sediment samples were collected from 31 stations. Cluster and Pearson correlation analyses were used to evaluate the relation between metals and physicochemical parameters of the samples. Ni، V، Co، and Ti were strongly correlated with each other and were negatively correlated with Mn. A distribution map of the metals was drawn using the ARC GIS 9. 2 software. Results showed that metal concentrations were low and sediments were not contaminated by Ni، Co، Mn، Ti، and V. The presence of metals in bed sediments is controlled by local geological units. The mean variation in metal concentrations was Ti > Mn > V > Ni > Co. The results of the geoaccumulation index (Igeo) showed that the samples were practically not polluted by these five metals. The source of Mn appears to be different from the other studied metals. Enrichment factors for these five elements were lower than pollution limits، which indicated low enrichment. The pollution index showed moderately polluted sediments with regards to Ni، Ti، Co، and V، and unpolluted sediments with regards to Mn، which showed the human impact on the concentration of these metals.

Pore type distribution in reservoir rocks is the main factor controlling fluid flow in porous media. Therefore، determination of pore types in reservoir rocks leads to better prediction of the number of wells to be drilled in the field and to improved forecasts of recoverable hydrocarbon. Hydrocarbon reservoirs، especially carbonate rocks، have complex pore types and sizes. In this study، pore types of the Asmari formation are recognized with log data and are validated by core data. For determination of pore types from log data، a velocity deviation log method was used. Based on velocity deviation log and elastic properties، pore types were classified into three classes (positive، zero، and negative) and eight subclasses. They include intraparticle (intrafossil)، moldic or vuggy، microporosity، interparticle، intercrystalline، intergranular، shale microporosity، and fracture porosities. In this field both carbonate and clastic intervals had high potential for production. To determine reservoir quality، hydraulic flow units along with their pore type’s spectrum were investigated. For this purpose، flow units were determined with the flow zone index method. Results of this study led to the determination of three flow units in the carbonate section، with two flow units in the clastic interval. Accordingly، pore type distribution was investigated in each individual flow unit. Finally، results of this study showed that the production in this field is controlled with four pore types that were recognized by the velocity deviation log along the well bore.

The upper part of the Sarvak formation (Cenomanian–early Turonian) is the main reservoir rock in the Sarvestan oil field. The Sarvak formation showed a shallowing-upward sequence in this field. Detailed petrography on thin sections in two wells (SV#5 and SV#6) suggested that the Sarvak formation is composed of 12 microfacies that can be classified in four facies belts، including inner ramp، mid ramp، outer ramp، and basin. These facies indicated a homoclinal ramp-type carbonate platform at the time of deposition. According to petrographic evidence، the facies were influenced by marine، meteoric (eogenetic and telogenetic)، and burial diagenesis. Meteoric dissolution and fracturing were the most important factors enhancing reservoir quality، while cementation and compaction reduced porosity and permeability. The evaluation of the reservoir development showed that meteoric digenesis during Cenomanian–Turonian and mid-Turonian times has had a significant influence on shoals، patch reefs، and their taluses، which created vuggy and moldic porosity and improved their reservoir quality، especially during the mid-Turonian.

The Aghajari formation alternates sandstone، marl، and siltstones with gypsum veins. The formation is a wide outcrop in the southern and southwestern parts of Iran، and dates from the Miocene to Pliocene. However، very little information is available on the nature of the genesis of this formation. In this study، petrographical properties and major element geochemistry of sandstones from the formation in Khuzestan province were performed to identify the provenance and tectonic setting of these rocks. Petrographic examinations of 29 sandstone samples revealed that these sandstones are calclithites and volcarenites. Five of the studied rocks samples are grain-supported. One sample has gypsum cement، and the others have calcite cement. Moreover، discriminant plots showed that the provenance of the sandstones is sedimentary quartz that is derived from recycled orogeny. The major element geochemistry analysis demonstrated that the chemical compositions of the rocks are litharenite، ferrous sandstones، as well as greywacke. Moreover، projecting the major element geochemistry data on tectonic setting discrimination plots indicated that the sandstones had been deposited in an active continental margin.

Vast Permian carbonate deposits exist in the Maku area as compared with other parts of Iran، and comprise dark gray limestones with a thickness of about 926 m. Based on lithostratigraphic studies، there are three lithologic units (bellerophon limestones، cherty limestones، and crystallized and dolomitic massive limestones) in the Permian deposits. Biostratigraphic studies led to the identification of four biozones representing the Murgabian– Djulfian age for carbonate deposits in the studied section. According to microscopic studies، there are nine microfacies that belong to the carbonate ramp with inner-ramp، mid-ramp، and outer-ramp environments. Magnetic susceptibility values of these deposits were measured between 10 × 10−6 SI and 30 × 10−6 SI، and mostly show negative values. Integration of magnetic susceptibility، stratigraphy، and microfacies studies showed that the carbonate production rate on ages {1. 2 [EN] Meaning unclear} and in different depositional environments were the main factors leading to magnetic susceptibility changes in the studied section.

Nowadays، erosionand sedimentation processes are studied in the sciences such as geology، natural geography and watershed management. Soil conservation and prevention of rapid filling of reservoir dam are very important problems. Accordingly، rate of erosion، estimation of annual sediment production and sediment yield of catchment basin using experimental models are intriguing for researchers. In this research، Khor and Sefidarak watershed basin in Alborz provenance are selected as case studies. The purpose of this project is to estimate the annual delivery sediment in these basins، using EPM and MPSIAC models، and make comparisons between them. In this relation، after field surveying، lithology، soil، vegetation cover and other maps، for each subbasin were used and carried out the compilation of all information. Corresponding tables were prepared for quantitative calculation of each parameter for study of erosion using MPSIAC model and classification of erosion intensity was carried out using EPM model. Average specific sediment yield for the seven basins in two models MPSIAC and EPM is 3. 28 and 1. 99 cubic meters per hectare per year (respectively) and Average specific erosion in these two models MPSIAC and EPM is 11. 0 and 3. 93 cubic meters per hectare per year.

The Surmeh Formation comprises the Jurassic rocks of the Zagros Mountains and is considered as one of the most important petroleum reservoir units in the Persian Gulf basin. This formation is mainly composed of thick bedded and cliff forming carbonate rocks. The aims of this study are to investigate depositional history and sequence stratigraphy of the Surmeh Formation in the Fars province or eastern Zagros. Field and laboratory examination of the formation revealed the presence of 15 lithofacies related to different evolutionary stages of a carbonate platform. The results of different measured sections indicated that the lower part of the Surmeh Formation is composed of thick-bedded dolomitic facies containing Lithiotis fossils of Toarcian age related to a shallow marine epeiric platform. At the Aalenian tectonic movement along the preexisting basin faults resulted in the formation of adistally steepened ramp and Pars intrashelf basin. Consequently، alternating shale and limestone (calciturbidites) were deposited in the deep marine environment of an outer ramp during Bajocian. During Bathonian، overproduction of carbonates and progradation of platform facies over basinal deposits resulted in reestablishment of the homoclinal ramp that was in existence in the study area until the end of Jurassic. Vertical facies variations and comparison with global sea level curve revealed the existence of two second-order depositional sequences in the Surmeh Formation. The given sequences by themselves include 6 third-order sequences and correlate with lower Zuni I and lower Zuni II super sequences of Sloss (1963).