Researches in Earth Sciences
Year:2011 | Volume:1 | Issue:4|Papers Count:8

The caprock of the Asmari reservoir in the Zagros region is consist of Gachsaran Formation. Zeloi Oil Field located at 30km NW Masjed-Soleiman with a length of 40 km and width of 6 km. The palaeo-environment was evaluated by the uses of geochemical variation in the sedimentary basin of Gchsaran Formation in this oil field. Based on these data, the cap rock was on a sabkha-lagoonal environment. Wet to dry hot weather condition was increased evaporation, caused to generate a cycle retrogradation and extended sabkha environment. Finally, The thickness of deposited layers of salt in Gachsaran Formation was due to sea water retrogradation and disconnection with sedimentary basin. This changes could be indicator of alternatively of wet to dry hot weather during deposition of Gachsaran Formation.

Ilam Formation in Kuh-e-Shah Nakhjir section, south of Ilam, with a total thickness of 172 m, consist of limestone with interbedded marly and shaley limestone. The lower contact with the underlying Surgah Formation and upper contact with the Gurpi Formation is conformable. On the bases of petrographic studies, important diagenetic processes in the Ham Formation include cementation, physical and chemical compaction and replacement processes such as hematitization, pyritization, phosphatization, glauconitization and silicification. Porosities observed in this section include intraparticle, vuggy and fracture types. Petrographic studies and, determination of fossils and textural characteristics led to identification of five carbonate microfacies, which are belong to open marine facies belt. Planktonic foraminifera are dominate in these microfacies and they were mud supported and are deposited in deeper part of the basin.

The study section, with a thickness of 652 m, includes the Champeh and Mol Members of the Gachsaran Formation located at the southeast Firoozabad. The Champe Member comprises of thin to medium limestone layers inter-bedded with marl and marly limestone. The Mol Member consists of inter-bedded of thin marly limestone, green and red marl and gypsum and anhydrite. Based on occurrence of the Archaias asmaricus- Archaias hensoni assemblage subzone, the lower part of the section (from base up to 116m) is Chattian in age. The rest of the section is considered to be Aquitanian in age. Facies and microfacies of the Champeh Member reflect deposition in tidal flat and lagoon environments. Tidal flat deposits comprise fenestral mudstone and stromatolite bindstone and lagoon environment identified based on the occurrence of green-gray marl, imperforate and occasionally with perforate foraminifera and peloid in wackestone to grainstone textures. Restricted to semi-restricted lagoonal facies of the Mol Member are gypsum and anhydrite, gypsiferous red marl, hybrid sandstone, mudstone, green-gray marl, imperforate with occasionally perforate foraminifera and peloid with wackestone to grainstone texture.Two third order depositional sequences comprise of TST and HST stacking patterns and a half depositional sequence (HST) identified for the studied section. Semi-restricted lagoon facies with increase in foraminifera are characteristic of the TST stacking patterns. Decrease in foraminifera, records the restricted lagoon facies of HST stacking patterns. Identified sequence boundaries are correlateable with depositional boundaries of the other parts of the Zagros.

Various volcanic rocks of different ages especially of Cenozoic are exposed in Central Alborz. Some of volcanic unit’s with the low crystal and high glass content are used in cement industry. After sampling, the volcanic rocks, based on their petrography and geochemical studies, 13 samples were prepared to use in pozzolanic cement. Petrographic studies revealed that non zeolithic alternation is a dominant event that reduce the pozzolanic activity. In this study, three different methods are used to determine pozzolanic characteristis and results were compared. Obtained results from central Alborz volcanic rocks show that resistance index method, according to ASTMC618, is not compatible whit thrmogravimetry and equilibrium concentration determination methods. However, the result of Thermogravimetry method (STA-tg) is well compatible whit the equilibrium concentration determination method according to the EN196-5.The observed results obtained from resistance index method (ASTMC618) cannot be use to determine pozzolanic activity as a sole evaluation indicators. Petrography of rocks as a complementary feature of chemical characteristics is very useful and decisive.

Generally, the origin of coastal sands is river basins and influence of dynamic waves and currents along the coastline are distributed. The case study in this research is middle part of the shore line of Caspian Sea between Haraz River and Babolrood with approximate length of 60 kilometers. The purpose of this research is to determine the direction and amount of sand currents that distributed along the coastline. To achieve this goal, wind data, discharge and sediment of rivers and topographic and geological maps, are used as the main tools and data. In addition, during the field work more than 20 samples of sand taken from the shore line and using survey by granolometery techniques. Then analyses by assessment of sands size and the wave characteristics by analytical methods with Gradistat 4.0 software between them, communicate between directions of sand current during the coastline. To control the results, the wave tank model to compare current levels of sand in the swash zone was used. Also to assess the direction of sands movement by the waves along the shoreline sand samples was colored in the selected sites, the amount of their distribution was controlled. The results show that the dominant directions of wave was, West, North West and North, respectively and current distribution caused by sand and towards the East than the average distance from the river mouth sand particle diameter is smaller. Factors such as discharge of rivers and discharge of sediment and resistance of formation in basins determine as directly the volume of transfers of sand along the coastline sensitive.

Because of arid and semiarid conditions in Iran and the shortage of freshwater resources, it is essential sensitivity to water quality of rivers and factors affecting to these factors. In this regard improper use of lands is one of the most important factors in reducing the amount and quality of water resources in Catchments. The goal of this study was to determine the relationship between land use changes with changes in water quality parameters in Kahurestan catchment. So, at first changes in the area of land uses was measured in this catchment at three different times. Then, the changes in water quality of river, was studied at different times. The results showed that land use caused decrease in pasture lands and increase in agricultural lands and bare lands that eventually has been resulted to decrease in water quality in the river of this catchment.

Long-term annual or seasonal averages of climatic variables like temperature, has generally been used as indicator for the assessment of climate change. Accordingly, this paper is aimed to examine extreme temperature as indicative climatic variable in synoptic stations of Semnan located in Semnan province during a 42 year period (1965-2006) to determine recent climatic changes over the mentioned area. To achieve the aim, 7 indices of extreme temperature recommended by the internationally agreed WMO-CCLICLIV AR list of over 50 climate change indices climate extremes were selected and calculated. The seven indices are consist of cold nights, cold days, warm nights, hot days, summer days, frost days and diurnal temperature range. These indices describe cold extremes as well as warm extremes. Extreme temperature indices for this study are based on time series method and the 1st and 99th percentiles.Results of this research indicated that thermal conditions over the area are changing as shown by a warming trend identified during the study period. Results of this study also showed that the marked negative trends for indices such as cold days, cold nights, frost days and diurnal temperature range over the region. While significant increases are detected in the annual number of hot days, warm nights and summer days.