Stratigraphy and Palaeontology
Ali Jalali; Hamed Yarahmadzahi; Mehran Arian; Abdollah Saidi; Seyed Mohsen Aleali
Abstract
The Shishtou section is located in the north of Tabas Ghezelin and Asselian sequences of Zaladou formation with 60 m thickness are divided into five units, includes sandstone, limestone, shale, sandy limestone and limestone. The lower boundary of the Gzhelian deposits with disconformity on top of the ...
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The Shishtou section is located in the north of Tabas Ghezelin and Asselian sequences of Zaladou formation with 60 m thickness are divided into five units, includes sandstone, limestone, shale, sandy limestone and limestone. The lower boundary of the Gzhelian deposits with disconformity on top of the Moscovian deposits of the Abshani formation. The upper boundary of these deposits with the Tighe-Madanou formation is continuous. The assemblages of fusulinids in the Shishtou section such as Ruzhenzevites-Rauserites-Triticites are identified in the upper part of Gzhalian previously reported from equal deposits in Darvaz, Fergana, Southern Urals, Donetsk and Carnic of Alps, as well as, Central Iran, Central Alborz and Sanandaj-Sirjan zones. Also, different species of Sphaeroschwagerina, Pseudoschwagerina and Likharevites, which illustrate the Asselian age, represent the Carboniferous-Permian boundary in the studied section and allow for comparability with other structural-sedimentary zones of Iran, including Central Iran , Central Alborz (Doroud Group) and Sanandaj-Sirjan zone. This equivalence expresses the transgressive of sea level in different parts of Iran in the late Carboniferous and early Permian periods. In Shishto section 15 genera ,35 species and 2 subspecies of Fusulins have been identified, some of which are reported for the first time from Iran.
Tectonics
Mohammad R. Ghassemi; Ali Aghanabti; Abdollah Saeidi
Abstract
Correlation of the orogenic and epeirogenic events in Iran with the events that have been identified in different parts of the world and in different tectonic environments, has caused some confusion in the Iranian geological literature. After a brief review of the nature of known orogenic processes in ...
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Correlation of the orogenic and epeirogenic events in Iran with the events that have been identified in different parts of the world and in different tectonic environments, has caused some confusion in the Iranian geological literature. After a brief review of the nature of known orogenic processes in the world, examining issues related to the abovementioned correlations, and considering the tectonic history of various parts of Iran, we have tried to systematically describe and name the important orogenic and epeirogenic events of the country. Most Precambrian orogenic events in Iran are dubious due to unknown age and poorly constrained tectonic setting of the rock units attributed to Precambrian. Paleozoic in Iran has been mostly associated with epeirogenic events, and the only sign of a real orogenic event goes back to the Late Carboniferous in northern Iran. The important Mesozoic and Cenozoic orogenic events have shaped the modern tectonic configuration of Iran. The Paleotethys suture in northern and central Iran formed during the Gorgani orogeny, development of the Central Iranian active margin (Sanandaj-Sirjan) occurred in the Ekbatani orogeny, ophiolite obduction in Central Iran and Zagros developed during the Late Cretaceous events, and collision of the Iranian plate with the Helmand block resulted in the Sistani orogeny. The creation of the Zagros and Alborz Mountain ranges started from Oligocene and Miocene times, respectively, and the deformation due to their shortening continues to this day.
Tectonics
Rojan Hemati; Manouchehr Ghorashi; Ali Solgi; Abdollah Saidi
Abstract
The Zagros suture zone is one of Key regions. Continent - Continent collision between Arabian plate and Iranian Block. This region is coincided by High Zagros and Zagros Simply Fold Zones in Western side and in other side is the Sanandaj- Sirjan Zone. The region of this research in situated in Northern ...
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The Zagros suture zone is one of Key regions. Continent - Continent collision between Arabian plate and Iranian Block. This region is coincided by High Zagros and Zagros Simply Fold Zones in Western side and in other side is the Sanandaj- Sirjan Zone. The region of this research in situated in Northern part of suture zone. The Zagros suture is oriented parallel to the other collision Structures as passive and active margins of Neo- Tethys Basin and also to Magmatic Arc (Urmiyeh - Dokhtar Arc).The main Faults in this region which we can mention by name are Zagros Main Thrust Fault and Zagros Main Recent Fault, Which they are also parallel to others structures. This region of suture zone in highly deformed and structures as folds, faults and nappes are the evident of a long compression Tectonics. The aim of this research firstly is analysing of folds and secondly is calculation of shortening rate of crust in this part of collision Zone. Three structural section (Eslam Abad- e- Gharb - Mahidasht, Kamyaran and Gazorkhani) have been balanced and the rate of shortening which is obtained respectively is 6252m , 6530m and 2040m.
Tectonics
Zeynab Taslimi; Abdollah Saidi; Mehran Arian; A. Solgi; Manouchehr Ghoreshi
Abstract
The Alborz Mountains has been separated the subsiding Caspian Basin from the foreland basin of Central Iran. This mountain range from east to northwest, has changed greatly in structural trend formed spirally. Two orogenic phases, Cimmerian and Alpine events caused more changing in sedimentary basin ...
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The Alborz Mountains has been separated the subsiding Caspian Basin from the foreland basin of Central Iran. This mountain range from east to northwest, has changed greatly in structural trend formed spirally. Two orogenic phases, Cimmerian and Alpine events caused more changing in sedimentary basin of Palo Tethys and Neotethys and it caused the complexity of abundant structural in other way too. The aim of this research is to investigate and analysis of existence structures in east central Alborz from northwest of Damghan (South of Toyeh) to South of Sari (North Alborz fault). The Structural features Analysis indicate that the Alborz Mountains are a fold and thrust belt. During the intense shortening of Alborz crust in the studied area the initial model of folds have been modified or destroyed. Some of these folds could take place in flexural flow folds or Drug folds classes since one limb of folds on the surface of low-angel thrust faults was thrusted recumbently. The thrust faults with south and north dipping is the main controller for variety structures in this part of Alborz. Based on geological and structural properties, construction of folding structures initiated during the Alpine orogeny since the late Eocene (37 million years) and the most shortening and faulting had occurred during at the Late Miocene. Data presented here demonstrate that shortening percent in the study area of Alborz Mountains is about 36.27% and the Rate of Shortening is estimated about 0.93 mm/y.
Tectonics
Zahra Mohammadyasl; Abdollah Saidi; Mehran Arian; Ali Solgi; taher Farhadinejud
Abstract
The Studied area is located in the small part of the structural zone of Urumieh- Dokhtar Magmatic Arc, at 60km far from south of Qom and 12km far from south east of Kahak. In the beginning, 1:25000 map of the area was prepared, because, region is located in two 1:100000 scale map sheet of Kahak and Aran, ...
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The Studied area is located in the small part of the structural zone of Urumieh- Dokhtar Magmatic Arc, at 60km far from south of Qom and 12km far from south east of Kahak. In the beginning, 1:25000 map of the area was prepared, because, region is located in two 1:100000 scale map sheet of Kahak and Aran, and more rock units were separated. In the next step, in a several step of the field observations, 17 samples of regional volcanic rocks were taken for XRF and ICP chemical analysis, and they main Oxides, heavy metals and rare elements were identife. Most of the samples have been located in the Calk- alkaline series, and some in the Tulleit series. In the lithology diagrams, these samples respectively are arranged in the range of Andesite, Dacite, Trachy Andesite and Rhyolite Rocks. Due to the anomalies and the amount of Nb in the samples of the region, they formation can be related to the subduction zone. On the other hand, the depletion of Nb and Ti is special in magmatism in the subduction zone. Because in the subduction regions released fluids from floating lithospheric rich in LILE, increases in the mantle wedge. Since in the study area rocks exhibit calc- alkaline with moderate to high potassium, it can be concluded that the stones are related to active continental margin associated with subduction.
Tectonics
Sepideh Rezabeyk; Abdollah Saidi; Mehran Arian; Ali Sorbi
Abstract
In the Northern part of Suture Zone (Kermanshah) the deep sea sediments, oceanic crust remnants, platform carbonates, igneous and metamorphosed rock of active margin and carbonate sequence of passive margin are assembled in this studied area. This convergent area has provided a very complicated structural ...
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In the Northern part of Suture Zone (Kermanshah) the deep sea sediments, oceanic crust remnants, platform carbonates, igneous and metamorphosed rock of active margin and carbonate sequence of passive margin are assembled in this studied area. This convergent area has provided a very complicated structural zone. The main purpose of this study is stress characteristic analysis. A great data has gathered from the faults which are appeared within the rocks specially the radiolaritic rocks. The data includes characteristics of fault surface geometry, fault slip and lineation slip related. By using the method Right Dihedral, the position of main stress was obtained. The great number of reverse faults have a NW- SW trend, while the strike- slip faults, show a NE- SW direction. The Normal faults with a different displacements appeared younger than the other faults. The result of this study that we obtained the situation of main stress σ1, σ2 and σ3 respectively is 059, 305 and 195.
H. Yarahmadzahi; M. N. Gorgij; S. A. Aghanabati; A. Saeidi
Abstract
The studied section is located west of Tabas (Rahdar Mountion) in the Kalmard Block. The newly named Chili formation, as the first rock unit of the Khan group consist mainly of arenacous limestone, limestone and dolomite and has disconformity contact with underlying lower carboniferous deposits (Padeh ...
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The studied section is located west of Tabas (Rahdar Mountion) in the Kalmard Block. The newly named Chili formation, as the first rock unit of the Khan group consist mainly of arenacous limestone, limestone and dolomite and has disconformity contact with underlying lower carboniferous deposits (Padeh formation) and overlying late Yakhtashian-Early Murgabian (Sartakht formation) bauxite and laterite horizon,in this study 6 genus and 19 species of Fusulinids were recognized which could be grouped in two Biozones. The first biozone correspond to Perigondwania pamirensis Zone belonging to Late Sakmarian. The second one is comparable with Chalaroschwagerina vulgaris Zone of Early Yakhtashian age. The mentioned biozone is fairly comparable with Kalaktash assemblage already reported from Central Pamir,Karakorom, Afghanestan and south Tibet regions.
G. Maleki; A. Saeedi; M.H. Emami; M. Kheirkhah
Abstract
In Sanandaj- Sirjan zone a vast outcrops of volcanic rocks, which founded as high terraces, are covered the Pre-Quaternany rocks. The volcanic rocks are appeared in different shapes and morphological features. Based on the Zagros geodynamical evolution, mentioned rocks assumed ...
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In Sanandaj- Sirjan zone a vast outcrops of volcanic rocks, which founded as high terraces, are covered the Pre-Quaternany rocks. The volcanic rocks are appeared in different shapes and morphological features. Based on the Zagros geodynamical evolution, mentioned rocks assumed to be Post – Collissional, that are formed in an extentional system with a NW-SE trend. Three studied complexes in this paper are Ahmad abad, Tahmures and Nadri. The structural investigation of three the sites are complementary data to the geochemical analysis. In this regards, structural investigation done in those 3 mentioned sites. Studied faults shows different trends and age. Mechanism of faults are normal, and their age are either Post- basalt or syn-basalt, that is, Contemporaneous with the last deposition of late-Miocene marls. The age of the oldest faults is late- Miocene, before basalt intrusion.
Kh. Hashemi; B. Oveisi; A. Saeedi
Abstract
Young deformations and folds are one of the impressive characteristics of Zagros simple folded belt. The studied structure is Hormud fault-related fold which is situated in the coastal Fars and the southward of Lar town. In order to illustrate the geometry of the studied structure and its kinematic relationship ...
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Young deformations and folds are one of the impressive characteristics of Zagros simple folded belt. The studied structure is Hormud fault-related fold which is situated in the coastal Fars and the southward of Lar town. In order to illustrate the geometry of the studied structure and its kinematic relationship with north and south structures, a structural cross section with ~27 km length from NE to SW was prepared. This study showed that Hormud anticline has been formed in the footwall of Lar fault, synchronous with kinematic reorganization in the core of Lar anticline and increasing horizontal stresses. Interpretation of crustal young deformations in the vicinity of the footwall of Lar fault indicates that Hormud anticline is growing in the form of a constant limb length detachment fold. Estimation of relative shortening rate (0.9± 0.2) for south limb of Hormud anticline is showing its fast growth in the form of a rocket fold which was associated by fast propagation of Hormud fault toward the surface. As a consequence of this process, kinematic model of Hormud anticline changes from a constant limb length detachment fold to a shear fault bend fold. Estimations predict 0.7 ± 0.1 mm/yr relative uplift rate for young Hormud anticline in its crest.
S. Rajabi; M. Eliassi; A. Saidi; A. Shahidi
Abstract
In this research, heterogeneous fault slip data are used as the main data for doing paleostress analysis in North-Tehran tectonic wedge, which is restricted between Mosha and North-Tehran faults. Using these data and paleostress methods, the studied area is divided into 15 smaller stable stress regions ...
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In this research, heterogeneous fault slip data are used as the main data for doing paleostress analysis in North-Tehran tectonic wedge, which is restricted between Mosha and North-Tehran faults. Using these data and paleostress methods, the studied area is divided into 15 smaller stable stress regions and the mean stress tensor related to each region is determined. Then, stress events are separated using Multiple Inverse Method. Based on mean stress tensors -obtained from stress regions- and rotation of fault data orientation -based on Anderson’s theory in compressional tectonic regimes-, the stress trajectory map is sketched for mean stress tensors acting in the regions during geological time. Configurations of trajectories show that they seem to obey the overall tectonic regime in Iran. This result refutes that the North-Tehran tectonic wedge could be a dynamic wedge.
A. Ghaderi; A. Aghanabati; B. Hamdi; A. Saeedi
Abstract
To study the Shirgesht Formation biostratigraphy in Kalmard Horst in relation to its conodont content, the Miyugodar (Miangodar) stratigraphic section was selected which is located in southwest of Tabas city. The Shirgesht Formation in the mentioned section is mainly composed of siliciclastic rock units ...
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To study the Shirgesht Formation biostratigraphy in Kalmard Horst in relation to its conodont content, the Miyugodar (Miangodar) stratigraphic section was selected which is located in southwest of Tabas city. The Shirgesht Formation in the mentioned section is mainly composed of siliciclastic rock units and overlay unconformably on Kalmard Formation (attributed to Pre-Cambrian) and is overlain by Gachal Formation (Carboniferous). Thirty five rock samples were selected from appropriate rock units (Shirgesht and Gachal Formation). Samples were studied in laboratory for more details. According to the extracted conodont from Shirgesht Formation in Miyugodar section, the age of this formation can be regarded as Early Ordovician (Tremadocian – Arenigian). Three conodont assemblage zones were recognized in Early Ordovician units. They are: Cordylodus spp., Deltifer and Proteus Global Standard Conodont biozones. The recognized biozones are as followed:
1- Oneotodus - Drepanodus Assemblage Zone
2- Acodus deltatus - Protopanderodus Assemblage Zone
3- Acodus - Oistodus Assemblage Zone
M. Pirouz; A. Bahroudi; M.R. Ghasemi; A. Saeidi
Abstract
The study area is located in Zagros simply folded belt, south of Firuzabad city. We have considered sedimentary basin floor deformation, initial time of folding and salt structure upwelling by using isopach data. Moreover, these data can be used to indicate ...
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The study area is located in Zagros simply folded belt, south of Firuzabad city. We have considered sedimentary basin floor deformation, initial time of folding and salt structure upwelling by using isopach data. Moreover, these data can be used to indicate the expanding development. We have used NIOC isopach data for the Permian to Paleocene and Oligomiocene. If isopach data values are reversed and the 3D patterns calculated, they can show sedimentary basin floor shape. According to the 3D patterns, sedimentary basin evolution pattern, primary time of salt structures movements and basement faults movement in Firouzabad area were obtained. Mengharak basement fault with N-S trend activated with vertical displacement in the Permian and its movement changed left lateral strike slip after Triassic. In addition, extensional structures formed in the east of Mengharak fault continued to middle Cretaceous. At the same time, Neothetys was closed and the extension structures were converted to compression structures and also Mengharak fault movement changed to right lateral strike slip. Activity of salt structures (Jahani and Firuzabad) began in Permian and its activation increased during the Cretaceous in the Mengharak fault zone.