GEOPERSIA
Year:2014 | Volume:4 | Issue:2|Papers Count:9

For the first time, an assemblage of cryptospores, which includes 10 species belonging to nine genera, from the Upper Ordovician strata, is being reported, in Iran. These cryptospore assemblages were recovered from the upper part of Ghelli Formation., from the eastern Alborz Mountain range. These peri-Gondwanan cryptospores have been classified based on their morphology (monad, true dyad, pseudodyad, true attached, and loose tetrads). The results of the present study support previous findings that there are no significant differences between similar-aged cryptospore assemblages of the peri-Gondwanan, Baltic provinces and other parts of the world. Based on the presence of the chitinozoan index of the northern Gondwana (Spinachitina oulebsiri), the index acritarchs, and the present cryptospores, a late Hirnantian (Late Ordovician) age is proposed to the top of the Ghelli Formation. The cryptospores seem to be transported from an adjacent land area and the lack of land-derived elements in the up-section may indicate an increased distance offshore.

Bagh Vang Section is located at about 45 km to the Northwest of Tabas and South of Shirgesht areas. In Bagh Vang Section, the Permian deposits of the Jamal Formation with a thickness of 270 m are underlain by the Sardar Formation disconformably. The formation is also transitionally and conformably overlain by Lower Triassic deposits of Sorkh Shale Formation. A total of 124 rock samples have been systematically obtained from various layers of Bagh Vang Section for biostratigraphic study. Forty one genera and 48 species of foraminifera; 10 genera and 12 species of algae have also been determined through this study. According to the biostratigraphic study, some index fossils of Fusulinidae have been recorded and the following assemblage zones have been selected that are equivalent to international biozones (Leven, 1975; Ishii, 1975): Paradunbarula – Geinitzina Assemblage Zone (Murghabian), Dagmarita – Paraglobivalvulina Assemblage Zone (Djulfian), Colaniella – Reichelina Assemblage Zone (Changhsingien). Further, geochronology of Member 1 and Member 2 of the Jamal Formation (Bagh Vang Member) is attributed to Early Murghabian, according to the index fossils.

Echinoids fauna are common and distributed in the Lower Miocene deposits of the Bagher Abad area, northeast Isfahan, Central Iran. There are six Echinoid taxa belonging to the Echinoidea Class that can be described as: Clypeaster intermedius, Prinocidaris sp. and spines related to: Eucidaris zaemays, Stylocidaris Polyacantha, Spatangoid sp. and Prinocidaris sp. Bivalves, Foraminifers, Bryozoans, Brachiopods, scatter fragment of Crabs and Corals can obviously be seen in this section. The presence of Echinoids and Bivalves fauna indicated that, the shallow and warm water environment was dominated by them in Central Iran at the Lower Miocene (Burdigalian). From a palaeobiogeographic point of view, the fauna from the Qom Formation were similar to the West and Central parts of the Paratethys and confirmed that, the Bagher Abad area was located in the marginal seaways, which connected the West, Central Paratethys and Indo-pacific Ocean at that time (Lower Miocene).

Assessment of the reservoir structure and determination of theinsitu stress direction are necessary in oil production optimization and field development. Today, the application of reservoir software and Image logsplay a central role in resolving this problem. Electric and ultrasonic imaging tools record vast amounts of high-resolution data within the borehole wall. This enables the geoscientists to describe in detail the structural fracture networks very essential for stratigraphic and structural analysis and improved reservoir characterization. A Six Arm Electrical Borehole Imaging (EMI) tool has recently been developed. This tool represents further advancement in the evolution of electric borehole imaging. The electrode arrays mounted on six independent arms provide excellent pad contact and produce very high resolution images for stratigraphic and structural analysis. Furthermore, the results of this study indicate that EMI is a powerful technique for identifying the dominant porosity and defining the relationship between fractures and permeability. In this study, data from two wells (well No.3 with FMI and well No.6 EMI image log) were utilized. The results of the Velocity Deviation Log and images indicate that the production in the Asmari reservoir of this field is a combination of fractures and rock matrix. Besides, the fractures and porous zones have effectively impacted the reservoir rock properties so that two general patterns of tectonic fractures associated with longitudinal and diagonal wrinkling can be identified. Longitudinal patterns are the dominant ones and often form the open fractures. They are mainly oriented in the N45-90W direction and are chiefly observed in the upper Asmari zones. Induced fractures and breakouts have been observed in the two wells, indicating a maximum horizontal stress orientation of 65oN in well No.6 and 295oN in well No.3. The stress direction in the western section of this oil field is therefore different from the eastern one and does not follow the general Zagros trend.

Ground settlement due to the shallow tunneling in urban areas can have considerable implications for aboveground civil infrastructures. Engineering geological characteristics of the tunnel host ground including geotechnical parameters of surrounding soil, groundwater situation, and in situ stress condition are amongst the most important factors affecting settlement. In this research, ground settlement as a consequence of the excavation of the East-West lot of Tehran Metro line 7 (EWL7TM) has been investigated. This tunnel has been drilled into Tehran's recent alluvia composed of fine-grained and coarse-grained soils. Findings indicate that the finegrained and coarse-grained soils do not have similar behavior during shallow tunnel excavation. In general, maximum settlements (Smax) occurred in the cohesion-less soil is greater than cohesive soil. In some sections of tunnel, measured settlements are lower than evaluated items, stemming from the lower volume loss (VL). Performance of TBM and localized cementation of Tehran alluvia in the considered area have been regarded as significant reasons of occurred discrepancy. In other sections of tunnel, measured settlements are greater than evaluated figures. According to relative thickness constancy of the overburden, this antithesis can be attributed to the existence of old and obsolete underground spaces.

Estimation of the metal value in the metallic deposits is one of the important factors to evaluate the deposits in exploration studies and mineral processing. Therefore, one accurate estimator is essential to obtain a fine insight into the accumulation of the ore body. There are geostatistical methods for the estimation of the concentration of iron which performance of these models is complexity of analysis.The support vector machine (SVM) is by far one of the most robust artificial intelligence techniques used successfully for predictions and estimations of deposits because of its ability to generalize. Keeping this is view, the aim of this article is to use the SVM and back propagation neural networks (BPNN) to estimate the concentration of the iron element in the Choghartdeposit, in Iran. Comparing the obtained results with those of the validation process demonstrates that the SVM method is faster than the BPNN method and is more precise for the estimation of the iron concentration in the Choghartmine. The results of this study show that artificial intelligence- based models can evaluate the iron concentration with an acceptable accuracy.

One of the major issues in dam construction is water seepage, post impounding. Assessment and prediction of the amount of water leakage can be useful in preventing such events. The Seymareh dam has been constructed on the Seymareh River in Ilam province, Southwest of Iran. The dam controls the floods and generates hydroelectric power. It is already under impoundment and the seepage problem is being considered. Grout curtains have been employed in two directions at the right abutment of the dam to control the seepage. The normal reservoir level is 720 m and it has been impounded at the 660 m level up to the point. The purpose of this study is to predict the amount of water seepage through the right abutment of the dam by using numerical modeling. For this purpose, a new GW finite element code was used for a two-dimensional simulation of the water seepage. The Levels of the observations wells and the discharges of the downstream springs on the right river bank are used as the main data for this modeling and its verification. Assessments show that if the dam impoundment rises to the normal level, significant seepage may occur through the right abutment.

The analysis of geochemical data in frequency domain, as indicated in this research study, can provide new exploratory information that may not be exposed in spatial domain. To identify deep geochemical anomalies, sulfide zone and geochemical noises in Dalli Cu– Au porphyry deposit, a new approach based on coupling Fourier transform (FT) and principal component analysis (PCA) has been used. The relationship between frequency attributes of surface geochemical data and mineralizing depth has been discussed. To determine the exploratory features in different frequencies, high- and low-pass filters have been performed on frequency domain; PCA method has been employed on these frequency bands separately. The results of this study have identified the mineralizing elements and showed the relationship between high- and low-frequencies and depths of anomalies. The geochemical halos of mineral deposits at different depths affected frequency distribution of elements in the surface. The information obtained from geophysical studies and exploration drillings, such as, trenches and boreholes, confirm the results of FT–PCA method. This new approach is very effective tool to identify the promising anomalies and deep mineralization without drilling.

Thirteen species of rugose corals, belonging to nine genera are described from the Givetian and Lower Frasnian rocks of the Khoshyeilagh Formation in the Eastern Alborz Mountains (northeastern Iran). Glossophyllum ceratites (Goldfuss), Glossophyllum sp., Keriophyllum cf. maillieuxi (Tsien), Pseudozaphrentis sp., Temnophyllum imperfectum Coen-Aubert, Temnophyllum occidentale Hill and Jell, Temnophyllum sp., Aristophyllum luetti Coen-Aubert and Spinophyllum blacourti (Rohart) come from the Givetian rocks and Neotemnophyllum sp., Sinodisphyllum cf. posterum (Ivania), Sinodisphyllum kielcense (Rozkowska) and Charactophyllum? nanum (Hall & Whitfield) belong to the Lower Frasnian strata. In spite of more or less remarkable endemism, the Givetian coral faunas of northeastern Iran show similarities with rugose corals of Germany, Belgium and Poland while the Lower Frasnian faunas reveal affinities with Eastern Asia as well as Europe corals.