JOURNAL OF SCIENCE (UNIVERSITY OF TEHRAN) (JSUT)
Year:2005 | Volume:31 | Issue:1|Papers Count:16

Numerous bird’s footprints have been found in the Upper Red Formation in western Mushampa village (100 km western Zanjan). Two specimens related to tetradactyl Antarctichnus, contain special track and tack off imprints. Birds walked with draging middle digit (digit III) on the sediments, which left as long furrow between footprints. Drag marks are in the tack off imprints, and some of them, however end to a circular hollow. These footprints are interpreted as running-leaping tack off model, on the other hand, birds have run at first, and have used foot pressure for leap in the point of tack off.

Geochemistry of Tertiary basic-intermediate volcanic rocks from S Danesfahan and S Karaj indicates two distinct rock series. S Danesfahan basic rocks are low in Ti (LT series), bearing the calc-alkaline signature of island arcs, while S Karaj basic rocks are high in Ti (HT series), representing midalkaline signature of oceanic islands. Geochemical characteristics of LT series volcanic rocks are as follows; low abundances of high field strength elements, HFSE, such as Ti, Nb and Ta and high abundances of large ion lithophile elements, LILE, such as K, Ba and Sr. This is consistent with attributing LT series volcanic rocks to the subduction of Neotethyan oceanic slab toward north in Eocene. LT series rocks are, therefore, magmatic products of a metasomatised lithospheric mantle wedge. Fluids released by the subducting oceanic slab, caused this metasomatism. On the other hand, contemporaneous, rather basic volcanics obtained from S Karaj , HT series, bear the characteristics of a deeper mantle source. S Karaj rocks, compared with the S Danesfahan’s, are enriched in trace elements particularly Ta and Nb. Trace element abundances and patterns of S Karaj volcanics are similar to the oceanic island basalts and imply the involvement of an asthenospheric (plume) mantle.

Rudbar area due to variety in lithological features and environmental conditions such as slope, precipitation rate, earthquake, and etc. is susceptible to land sliding. To evaluate landslide susceptibility in the area, landslide controlling factors were identified through analysis of existing maps, data and field survey. The landslide controlling factors were prepared as several thematic layers in a GIS environment. The thematic layers were analyzed and integrated using fuzzy logic system. The results were presented as landslide susceptibility maps in Auto CAD system. The results indicate that 68.30 percent of the landslides are located in moderate to high hazard class. Moreover, landslide density in high hazard class is significantly more than low hazard class. The main characteristic of the method is application of the expert's knowledge as rules for preparation of hazard map.

A volcanic rocks sequence which is composed of stratoid trachyandesite, basaltic trachyandesite lava flows and interbeds of paleosols is cropping out in the northeast of Zarjebostan area, as a part of Alborz paleogene volcanic belt. Petrographical evidences such as sieve textures, crystal zoning in the plagioclase phenocrysts and present of rounded phenocrysts all are indications of disequilibrium between the preexisting crystals and refreshed magma. Geochemical data from the studied volcanic sequence such as increase in the abundance of incompatible elements and concordant decrease in compatible ones are an indication of a magmatic evolution from bottom to top.

The Upper Palaeozoic strata widely crop out in the Marselan Valley, 28 km northeast of Loshan, north of Sangrud. The litho- and biostratigraphic study led to identification of 57 species (distributed among 37 genera) of foraminifera and 8 genera and species of algae. Three lithologic units (formations), seven lithozones and three assemblage zones are identified within the study interval. The rock units of the Permian system are in descending order as: a) Doroud Formation (Asselian- Sakmarian, thickness of 225 m), underlain disconformably by the middle Carboniferous (Bashkirian- Moskovian) Khashachal Formation, consists of red conglomerate, sandstone, shale, siltstone and buff oncoid limestone that can be divided in to three lithozones. b) Ruteh Formation (Murghabian, thickness of 364 m) mainly composed of cliff forming limestone that can be divided into two lithozones, unconformably overlying the Doroud Formation. c) Nessen Formation (early Djulfian, thickness of 140 m) consists of marly limestone intercalated with shale (contains of two lithozones), unconformably underlain by the Ruteh Formation and overlain disconformably by Elika Formation of Early-Middle Triassic age. Thin beds of laterite-bauxite indicate an unconformity at the Permian-Triassic boundary. Also these beds reveal that the study area, with a humid warm temperature, was lying near lat. 30°S.

In the eastern part of an ophiolitic complex in Sulabest area (in south east of Birjand) has exposed a metamorphic series including eclogite, blueschist, garnet bearing blueschist, amphibolite, epidote amphibolite, greenschist and micaschist. In addition to basaltic pillow lavas and cherts which have changed to eclogite and blueschist, were also metamorphosed most of gabbroic cumulate series to overlaying sheeted diabasic dykes. This metamorphism is within the limit of prehnite-actinolite(sub greenschist) to greenschist facieses. Presence of orbitoides microfossil within micritic limestones in ophiolitic complex, indicates Maastrichtian age of emplacement for ophiolitic complex. Thermobarometry results of eclogites showing that peak temperature of eclogites from Sulabest varies from 496 to 592°C and their peak pressures ranging from 22.0 to 26.4 Kbars. Epidote amphibolite retrograde metamorphism of these eclogites has been done in a temperature of 549 to 592°C and a pressure of 6.7 to 7.4 Kbars. Textural evidences and analyses results showing that, the second stage of metmorphism were taken place during ascending root of these rocks on to the surface. Coexisting of eclogites in studied area with blueschists, amphibolites and garnet amphibolites in the eastern part of an ophiolitic complex and combination of field observations and laboratory works, indicates that a subduction activity with a late Cretaceous age were responsible for the studied area and consequently for east of Iran, which were followed by an thrusting process during colliding of Afghan(Helmand) and Lut-Block plates.

The estimation of petrophysical parameters of reservoir which includes porosity, saturation and permeability, is the first and the most important step in an accurate evaluation and modeling of reservoirs. Porosity and saturation can be determined by row petrophysical logs and core analysis, meanwhile permeability only can be measured by the core analysis. For economic and technical reasons it’s impossible to take cores in all wells in a field or even completely in the depth of a well, so the estimation of permeability is necessary on the basis of petrophysical logs and core data. In this study fuzzy logic is used as a new and strong way in estimation of permeability by using petrophysical logs in one of the heterogeneous reservoirs in Iran.

Study of tide is one of the most important needs for scientists, engineers, port managers etc. Persian Gulf is one of the most important regions for transporting oil in the entire world. Harmonic analyses is one of the best methods used for analyzing of tide and the least square method is the best one for it. IOS is a tidal package that uses least square method. In this paper, we investigate the accuracy of IOS tidal package. For this reason, we perform numerical experiments with different lengths of records to determine sensitivity of tidal prediction results to these lengths. We also perform numerical examinations with gaps in data. Results of 25 tests performed in this regard show that if data recording is performed under the calm wave conditions, the accuracy of tidal predictions considerably increases with increase in length of data. However, predictions can be carried out with acceptable accuracy, using even 15 days of hourly data.

Two sections are measured and Sampled in Brojen and Semirom areas.The Brojen section is located 35 Km southwest of Brojen and consists of marls and olive-green shales belonging to Gurpi Formation and sandy limestone, marls and rudists limestone that overlain by red to green marl and shale and massive limestone belonging to Tarbur Formation. The Semirom section is located 57 km southwest of Semirom. It consists of grey marls and shales belonging to Gurpi Formation and marly limestone and massive limestone belonging to Tarbur Formation. Micropaleontological and palynological investigations reveal that the recovered assemblage of Brojen section contain 8 species belonging 8 genera of planktonic and benthic foraminiferas, 6 species belong to 5 genera of dinoflagellate and 15 genera with 12 species of spores and pollen. A large number of foraminiferal linings, wood materials and organic matters are also recovered. The recovered assemblage from upper part sediments of the Gurpi Formation and lower part of Tarbur Formation in Semirom section consists of 9 species belong to 11 genera of foraminiferas. On the basis of recovered assemblage one biozone of planktonic foraminiferas, two biozones of benthic forminiferas and one biozone of dinofellagellate were identified.

Dalan Formation is known as a largest gas reservoir in the Zagros and Persian Gulf areas. The Dalan carbonate succession was placed between early Permian Fraghan and early Triassic Kangan Formations at the base and top, respectively. Microfacies and sedimentological studies indicate the ooilithic facies would be a main reservoir facies, which is restricted to the Upper Dalan unit. Based on the study at least 5 distinct facies belt has been distinguished along the Dalan ramp carbonate platform. The above-mentioned facies belt consists of 9 facies groups in which were arranged from Sabkha, restricted lagoon, oolithic shoal to open marine settings. All facies groups are characterized by special sedimentological and diagenetic properties in the study areas (Kuh-Surmeh and Kuh-Dena). In terms of sedimentary environments, all facies group were controlled by eustatic sea-level changes, in the study areas. The sequence stratigraphical study has led to accurate recognition of 6 significant third-order cycles or depositional sequences consisting of several meter-scale parasequences. All depositional sequences were bounded by sequence boundaries (type1 and 2) or big sub aerial exposures. It is notable that each depositional sequence was deposited on the different sea-level flactuation with large scale shallowing-upward trend. Nevertheless, most depositional sequences are comprised of TST and HST intervals. As a result each depositional sequence represents a different sedimentary regime, sea-level changings and subsidence rate which were occurred during the Dalan carbonate deposition.

Studied potash-bearing evaporites are situated in the northern parts of the Great Kavir desert, south of Semnan city. These deposits, which could be classified as Mg-SO4 poor salts, belong to the lower parts of the Miocene Upper Red Formation. As well as halite, which is the main mineral, they contain primary sylvite and carnallite, and some secondary K-Mg bittern salts such as polyhalite, d'ansite and langbeinite. Surface and bottom nucleated chevron, cornet and cumulative textures in halite and sylvite indicates their early crystallization from parent brines in the shallow evaporitic ponds. Secondary K-bearing salts, which have been formed during shallow burial diagenesis, are polyhalite, d'ansite and langbeinite. High bromine contents, simple mineralogical paragenesis of these salts and their association with marine carbonates indicate their marine origin. Accordingly, a subsidizing relatively shallow marginal marine basin, under domination of arid climate, could be suggested for sedimentary environment of these evaporites.

Sistan is a flat and vast plain located on Hirmand river delta north of Sistan and Baluchestan province. Large amount of deposits carried to this plain, by the river, has decreased the depth of Hamoon Lake, so that, today some places of Zabol city has an elevation lower than Hamoon lake. So, to protect the city against flooding, some floodwalls (locally called Goore) have been constructed around the city. Erosion and destruction of these floodwalls is an important problem in the area. Because, this plain is mainly formed of sequences of clay and silt layers, soil dispersion, probably, has a main role in this erosion and destruction. Dispersion occurs in cohesive soils when the repulsive forces between clay particles exceed the attractive forces. They deflocculate in the presence of relatively pure water to form colloidal suspensions and therefore highly susceptible to erosion and piping. In this research 21 locations were selected in the study area and samplings were done. A series of field investigation, physical and chemical tests were carried out in an attempt to access dispersivity. In spite of High Na+ of these samples, dispersion of the soil samples rejected. However, mechanical erosion is the main cause of mentioned destruction.

With increasing of human needs to exploration of new hydrocarbon resources, petroleum geologist attention is attracted to qualitative and quantitative aspects of forming and migration of the hydrocarbon and also more precise evaluation of the hydrocarbon formation. Modeling investigation of source rocks can be considered as an important tool for exploration of oil and gas storage with lower risk. Existence of source rock is a necessary factor for any oil accumulation; hence having the acquaintance about source rock properties is very significant. It is imperative to know, where hydrocarbon is generated, from which kind of rock is migrated and transported. The most recent studies are carried out based on effective physico-chemical processes on hydrocarbon generation, value, quality and distribution of the organic matters in source rocks. Therefore, modeling method is an important tool to reconstruct depositional condition in time of sedimentation and after that. Based on studies by using modeling method with Winbury software (1D), the Gadvan Formation in located before threshold of oil window (Ro=0.35- 0.65). By considering burial history and thermal curves, insufficient maturity of the Gadvan Fm. is caused by shallow burial depth and low geothermal gradient in this region.

Kallat tunnel is located at the end of Mashhad-Kallat motorway and constructed in (1989) at the northeast of Kalat synclinal. During the tunnel excavation, some parts of tunnel was collapsed. Kallat tunnel was excavated in sandstone, limestone and marl. This paper presents the investigation of structural characteristics and stability assessments of the Kallat tunnel for widening it. Therefore, the rock mass rating (RMR), geological strength index (GSI) and rock mass quality (Q) systems was used for estimation of quality and quantity of rock masses properties around the tunnel. In order to estimate strength parameters of rock mass (compressive strength, tensile strength, deformation modulus and Hoek-Brown constants), Hoek-Brown failure criterion was used. Also finite element method (FEM) was used for stability analysis of Kallat tunnel. According to these data, the beginning section of the tunnel has the best stability and the end section of the tunnel has the worst stability conditions. The preliminary support design of this tunnel was analyzed by empirical method using the rock mass rating (RMR) and rock mass quality (Q) systems.

The F-X prediction filter is a technique to suppress random noise from seismic data in the frequency-space domain. For a given frequency, the coherent signal is predictable and random noise is unpredictable in the F-X domain. We then use the Complex Wiener Filter theory to obtain a least-square approximation of the desired signal. The method has been tested on a noisy stacked section. The result was acceptable without any noticeable artifact (lateral mixing). The method also applied on a synthetic shot record to eliminate air waves (coherent noise). This required application of an appropriate linear moveout on data before using F-X prediction filter. The necessary codes were written by authors in MATLAB environment.