فهرست مطالب rahim shabanian

 In this study the upper cretaceous rocks have been studied in shahin- Dezh , Detrital rocks with a thickness of 156 meters and  carbonate rocks with 114.5 meter lithological features and macroscopic characteristics of sandstone sequences,rocks were divided into 12 lithological units.Sandstone petrofacies often have mature texture characteristics and are placed in litarnite group of the sedarenite type based on the composition of the main grains which sedimentation conditions and environment the shallow and semi-deep sloping turbulent seas.thickness the basis of lithological features and macroscopic characteristics of carbonate sequences were divided into 11 separate stratigraphic rock units on the surface, and macroscopic characteristics of sections consisted of 3 groups of microfasics based on laboratory studies of microscopic samples and are comparable to SMF 3-Flugel, s Pelagic Mudstone-Wackestone and are deposited in the facies zone FZ_1 and FZ_3, evoking the sedimentation environment of relatively deep seas Shows that in general the conditions of shallow turbulent seas are related to the relatively deep seas off the coast of the Tethys Ocean and at the end of the second geological period Based on the composition of sandstone petrofacies grains, the aragonite range is determined by re-cycling for the origin of rocks. The study of vertical and horizontal changes in the microfacies environment indicates that high cretaceous sequences are composed of five sequences and show the retreat of short  transgression and regression in the form of a long - term progressive sequence The effect of this erosion is seen in the retreat and closure of the Tethys Ocean in this area

The Permian Ruteh Formation is known as one of the most significant successions in northwestern Iran. In the studied area it exposed a thick succession (201 m) of medium to thick-bedded carbonate sedimentary rocks in the west of Kuseh-Kahrizeh village in the north of Mahabad city. This formation unconformably overlain the Cambrian Mila Formation and it is unconformably underlain by the Oligo-Miocene Qom Formation The laboratory studies on the thin sections led to the identification of 15 microfacies that are arranged in three facies associations: inner ramp, mid-ramp and outer ramp. The petrographic results and facies analysis demonstrate that the depositional environment of Ruteh Formation in the studied area exhibits the characteristics of a homoclinal carbonate ramp platform of a gentle slope. This platform is mainly composed of supratidal, intertidal, lagoon, shoal, open marine, mid-ramp, and outer ramp environments. According to facies frequency analysis, the lagoon environment accounts for the highest abundance of facies (33%), whearas the outer ramp environment shows the least abundance (2%).Vertical distribution analysis of sedimentary facies led to the identification of transgressive and regressive depositional patterns. Accordingly, a total of 4 depositional sequences of third-order, 5 sequence boundaries and 4 maximum flooding surfaces were identified. The boundaries between all sequences are identified as SB1.

The Ruteh Formation is the second sedimentary cycle in Alborz basin. The petrography and laboratory studies of these deposits led to the identification of 15 microfacies which were deposited in seven sub-environments including supratidal, intertidal, lagoon, shoal, open marine, middle ramp, and outer ramp. Since there were no turbidity deposits, the lack of marginal reef belt and the gradual changes of facies, it turned out that these sediments were deposited in a homoclinal carbonate ramp. The study of relative sea level changes was done according to vertical distribution of facies and their stacking patterns. These studies lead to identification of four depositional sequences. The petrography data and geochemical analyzes were used in order to identify the diagenetic processes and geochemical changes. The recognized diagenesis processes include micritization, cementation, compaction, stylolitization, silicification, ferrugenation and neomorphysm. These diagenetic processes took place in three diagenetic environments: marine-phreatic, meteoric-phreatic and burial. Geochemical analyzes confirms that the carbonate sediments of Ruteh Formation were originally composed of aragonite, which was eventually recrystallized to calcite during diagenesis. Plotting Sr/Ca versus Mn diagram approved that sediments was subjected to a meteoric diagenesis in a semi-closed to open diagenetic system. The results of this research can be used to provide a sedimentary model for these deposits which completes the palaeogeographical data for the Tethys Ocean.
 

The geological observations indicating a coherent Iranian-Gondwanaland continental landmass during the Late Precambrian to Permian are consistent with palaeomagnetic data (Berberian and King 1980). Palaeomagnetic evidences from the Upper Precambrian rocks and iron ores of Bafq area in central Iran (Becker et al. 1973), the Lower Paleozoic rocks of kuh-e-Gahkom and Surmeh of the Zagros (Burek and Furst 1975), the Cambrian purple sandstone of the salt range of Pakistan (McElhiny 1970), the Upper Devonian–Lower Carboniferous of the Alborz Mountain in north Iran (Geiroud Formation; Wensink et al. 1978) and from the Upper Precambrian, Ordovician and Permian rocks of central Iran (Soffel et al. 1975; Soffel and Forster 1977) show similar geomagnetic poles with those of Afro-Arabia. These data and the widespread similarity of Paleozoic sedimentary succession indicate that during the Late Precambrian and Paleozoic, Central Iran, the Alborz in northern Iran and the Zagros in south Iran were parts of Gondwana (Berberian and King 1981). In the Late Carboniferous–Early Permian, continental rifting separated these lands from Gondwana due to the expansion of Neo-Tethys Ocean. Due to the glaciers growth and Hercynian orogeny movements in that time (Berberian and King 1981; Lasemi 2000), the Early Permian sedimentary facies in Iran are mainly siliciclastic (Dorud Formation in Alborz–Azarbaijan zone). In the Late Permian, after deposition of the Droud Formation, glaciers regression, tectonic tension activities and increasing volume of mid ocean ridges led to the sea progress and carbonate platforms restoring in the southern margin of Paleo-Tethys (Lasemi 2000). The carbonate rocks of the Upper Permian Ruteh (Asserto 1963) and Nesen (Glaus 1964) formationsin the Alborz–Azarbaijan zone and the Jamal Formation in central Iran, record the development of these carbonate platforms. The Ruteh Formation studied here is exposed about 15 km north of Mahabad city. Since no studies have been carried out on the Ruteh Formation in this area so far, this research aims to identify the sedimentary environment, sequence stratigraphy, diagenesis and geochemistry of this formation.

After literature review and preliminary visits of the study area, for the most complete and appropriate succession in the field was selected. Then, its rock units were delineated by means of horizontal and vertical scrolling. Based on the geometric features of sedimentary units, stratigraphic planes, sedimentary structures and biotic and abiotic components, the existing sedimentary units were divided and separated into diverse facies. In order to determine the microfacies and sedimentary environment of the Ruteh Formation 101 rock samples were collected systematically, and by taking into account the changes in the facies. To analyze the microfacies, textures, depositional environments, the facies components, the ratio between its components and various diagenesis processes, the samples were sent to the laboratories, and a thin microscopic section was made from the collected rock samples. Thin sections were studied under polarizing microscopes. In order to determine the frequency of allochems, the comparison charts (Bacelle and Bosellini 1965) were used. The microfacies naming was done by means of Folk’s (1962) and Danham’s (1962) methods, environmental energy detection based on Flügel's method (2010), texture studies based on Tucker's (2002) method, diagenesis evidences, energy detection and sedimentary environments were done by means of Wilson’s (1975) and Flügel’s (2010) methods. To detect depositinal sequences, the models presented by Hunt and Tucker (1992) were also used. To study the early mineralogy of the Permian carbonate rocks in northern region of Mahabad, after thoroughly studying thin sections petrography, eight limestones samples with the highest micritic matrix and least alternation and lowest fossil contents were selected. Then they were subjected to elemental analysis using ICP-MS (Inductively Coupled Plasma Mass Spectrometry) and alkali melting methods in laboratory of Zarazma Company (Tehran), then geochemical values plotted in geochemical diagrams for early mineralogy determination.

With regard to the identified microfacies, the process of the basin deepening from the carbonate platform towards the deep basin, the absence of oncoids, pisoid and aggregate grains, which are specific to carbonate shelf and rarely found in carbonate ramps (Flügel 2010), also, lack of re-deposited carbonate facies, sediments related to gravity flow processes in sediments of the Ruteh Formation indicates sedimentation of these sediments in a low-slope and approximately uniform gradient in the basin floor slope a homoclinal ramp profile can be predicted for the deposits of the Ruteh Formation in this study area (Wilson 1975; Read 1985; Lee et al. 2001; Flugel 2010). Due to the low expansion of the reefs in the carbonate ramp compared to the rimmed carbonate platforms, the lack of widespread barrier reef and the presence of patch reef in the Ruteh Formation is another reason for this fact that the sedimentary environment of this formation is a homoclinal carbonate ramp (Bastami 2016). On the other hand, by reviewing of distributed facies in sub-environments and their constituents it can be concluded that Ruteh Formation depositional environment is a bioclastic carbonate ramp similar to that introduced by Kolodka (2012) for Dalan Formation in Fars province. Based on the vertical distribution of facies, relative sea level changes these studies lead to identification of four depositional sequences. Early marine diagenetic processes like micritization and marginal micrite cements well represente transgression of sea level. During the sea level regression (sequence boundaries), sediments have been affected by meteoric diagenetic processes such as granular calcite cement, blocky calcite cement, syntaxial cement, ferrugination and neomorphism. Also the evidences of deep burial diagenetic process observed by physical compaction, druzy calcite cement, stylolization, poikilotopic calcite cement and silisification processes. Geochemical analyzes confirms that the carbonate sediments of Ruteh Formation were originally composed of aragonite, which was eventually recrystallized to calcite during diagenesis. Plotting Sr/Ca vs. Mn diagram approved that sediments was subjected to a meteoric diagenesis in a semi-closed to open diagenetic system.

The Cretaceous deposits in Morakan, located in the northeast of Khoy, a town in western Azerbaijan province, Iran, are primarily made up of carbonate rocks. These deposits, which are of 717 meters thick, lie on the clastic facies of Jurassic and are covered with beneath the pelagic beds of the Upper Cretaceous. To investigate the facies, sedimentary environment and sequential stratigraphy of these successions, a stratigraphic section was made in the south of Morakan village. Carbonate facies in this section have deposited in open marine, bar, lagoon, and tidal flat facies belts. The study of these facies and comparing them with old and modern sedimentary environments reveals that these succes-sions have deposited in a carbonated platform of rimmed shelf type. The study of the vertical succes-sion of microfacies shows four main sequences in the form of system tracts of TST and HST, which are made up of shallowing and deepening parasequences. The first lower boundary of the sequences is the type SB1 unconformity, and other identified sequences are the type SB2 unconformity.

Remains of fossil herbivorous mammal from families like Elephantidae، Rhinocerotidae، Giraffidae، Bovidae and Equidae have been studied systematically from a new fossiliferous horizon from the Ilkhchi area in the southeastern high foothills of Sahand. Genera such as Hipparion، Gazella، Samotherium، Chilotherium and Choerolophodon and some undetermined specimens are identified and reported. Based on the position of the layer containing fossils، which is placed at the top of a volcanic (dacitic tuff) key bed and based on the absolute ages available from this key layer، a Late Miocene age is proposed for this fauna.

Ruteh Formation is composed of dark bioclastic limestone and marl layers in the Baghdarreh section، Soltanieh Mountains (northwest Iran). It is about 43 meters in thick. Ruteh Formation is Murghabian in age based on foraminifers’ assemblages. Carbonate layers contain Zoophycos، Chondrites، Planolites and Rhizocorallium trace fossils، which Zoophycos is the main and abundant among other rare trace fossil. Microfacies analysis (10 identified microfacies) shows sediments of Ruteh Formation deposited in three facies belts including inner، middle and outer homoclinal carbonate ramp. Zoophycos only present in the outer ramp to open marine microfacies with anaerobic and low tolerances conditions، below storm weather base. Where the depth increased، size of Zoophycos and its burrow diameter increases which fellowed by development of bioturbation. Ruteh Formation’s Zoophycos have no lobate structure and it formed in organic bearing carbonate sediments.