H Safari; M. R. Ghassemi; M. Agh- Atabay; R. Razavi pash
Abstract
Lahijan fault zone is one of the transverse faults in western Alborz which with, sinistral mechanism caused structural deformations in this region. In this research, with using of field investigations, Remote Sensing techniques and statistical structural analysis methods, the structural analysis of Lahijan ...
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Lahijan fault zone is one of the transverse faults in western Alborz which with, sinistral mechanism caused structural deformations in this region. In this research, with using of field investigations, Remote Sensing techniques and statistical structural analysis methods, the structural analysis of Lahijan fault zone is performed and consequently, the fault zone (Geometry) is constructed. On the basis of results of this research, the Lahijan fault with attitude N 55/70-SE has 30 Km width. This fault zone is considered as sinistral fault zones which have different related fractures. The fractures related fault zone are ordered as syntethic and Antithetic faults. Most of faults in this fault zone have Net- slip movements and the angle of these to main fault zone, specified their mechanisms so, the parallel faults zone have left- lateral movements and in opposite, the faults with angle of 75˚ related to fault zone trend, have Right- lateral movements. Due to progressive sinistral deformation, all of structures rotated counter- clockwise and placed in lesser angle relative to this shear zone.
M Royatvand; A Bahroudi; M. Qoreshi; M. R. Ghasemi; S. A. Aghahosseini
Abstract
The Oligocene salt in the Garmsar and Eyvankey plateau, south–central Alborz, has extruded on the quaternary sediments and formed a salt glacier. This open-toe salt glacier is about 24×17 km that is unique continental salt glacier in the world, dimensionally. Also, this ductile substrate ...
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The Oligocene salt in the Garmsar and Eyvankey plateau, south–central Alborz, has extruded on the quaternary sediments and formed a salt glacier. This open-toe salt glacier is about 24×17 km that is unique continental salt glacier in the world, dimensionally. Also, this ductile substrate has affected on structural styles of this region. However, little systematic work has done on it. To investigate the structural styles of the region that affected by a ductile substrate and adjacent region with a frictional decollement, and also the structures of the salt glacier,series of models were done which were scaled sandbox models. These sandbox models simulated the propagation of deformation of thin-skinned simultaneous shortening above adjacent ductile and frictional of two end member of decollement. Model results illustrate that above a ductile substrate, deformation propagates further and more rapidly than above a frictional substrate as we can see in the nature that the region with a ductile substrate is so broader than the adjacent region with a frictional decollement. Like the models, toward the north in the nature where the Decollement is frictional, from North Tehran Fault as a frontal fault to Mosha and Kandovan Faults in the core of Alborz Mountain, the dip of the faults are increased and only forward-vergent imbricate faults, whereas above the ductile substrate the dip of faults has not a definite pattern of dip and also, both foreland and hinterland imbricate faults develop.
A. R Shafeii; M. R. Ghassemi
Abstract
The present research is aimed at investigation of geometry and kinematics of joints, relationships and temporal and spatial distribution of the joints regarding the two deformational events within the Purkan-Vardij thrust sheet. We also studied the relationships between development of different joint ...
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The present research is aimed at investigation of geometry and kinematics of joints, relationships and temporal and spatial distribution of the joints regarding the two deformational events within the Purkan-Vardij thrust sheet. We also studied the relationships between development of different joint sets and the lithological characteristics of layers of the Karaj Formation. Considering outcrops of volcaniclastic and igneous rocks of variable lithology, we have divided them into five different rock units including thick-bedded to massive tuffs, thin- to medium-bedded tuffs, tuff-shale-sandstone sequence, shale, and igneous units. Joint study was carried out using selection method, and in part using listing method, which are useful for quick survey and statistical purposes. Joint classification was carried out using concentrations of pole to joint planes. We have used the fracture spacing index (FSI), which is an important parameter in controlling morphology and erodibility of the rock units; it is also useful for prediction of joint spacing in other layers and in surrounding areas. These characteristics are useful in road construction, tunneling and other engineering projects. A comparison of the FSI in different rock units indicates that the intrusive bodies and thick-bedded units develop a highly variable FSI with a wide range of spacings, which in most cases due to lower concentration of the joints show lower erodibility as compared to the other rock units, and therefore have more relief in their outcrops. Two major joint sets, J1 and J2, show the highest frequency within the classified joint sets. Both of these sets are of extension joint type, and their strikes indicate the s1 direction during their development. Our study in this research confirms that amount of the strain produced by the joints is very small.
M Ramazani; M. R. Ghassemi; A Zanchi; M. R Sheikholeslami
Abstract
Theerosional window of Aghdarband , located in NE Iran to the SE of Mashhad is a unique place for study of the Eo-Cimmerian event. This event (Late Triassic-Middle Jurassic) resulted from clousureof thePaleothetys ocean and collision between the Iran and Turan plates. These two plates were separated ...
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Theerosional window of Aghdarband , located in NE Iran to the SE of Mashhad is a unique place for study of the Eo-Cimmerian event. This event (Late Triassic-Middle Jurassic) resulted from clousureof thePaleothetys ocean and collision between the Iran and Turan plates. These two plates were separated from each other before Late Triassic, and therefore they had different tectonic and sedimentary histories. At this time the Aghdarband area was located on active margin of Eurasia, and therefore the units that are exposed in the erosional wiondow of Aghdarband have basic differences with their counterparts in other places of Iran. During the Eo-Cimmerian event, the Aghdarband area was affected by a sinistraltranspression. Strain in this transpressional zone was intensively partitioned, and three major structural domains with different structural characteristics were formed in it. A sinistral strike-slip fault zone and an imbricate thrust fault zone were formed respectively in northern and southern part of the Aghdarband area. Development of this transpressional zone may be attributed to the oblique convergence between Iran and Turan plates during above mentioned time interval.
M Ramazani; M. R. Ghassemi; A. Zanchi; M. R. Sheikholeslami
Abstract
The Dare Anjir and Fariman complexes in NE of Iran are considered as remnants. These complexes considering were located close to Palaeotethys suture zone, and thus they record its structural evolution. considering structural and petrological evidences and against previous opinions that considered Fariman ...
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The Dare Anjir and Fariman complexes in NE of Iran are considered as remnants. These complexes considering were located close to Palaeotethys suture zone, and thus they record its structural evolution. considering structural and petrological evidences and against previous opinions that considered Fariman complex as an accretionary wedge, these complexes seem to be remnants of a magmatic arc that formed as a result of subduction of the Palaeotethys beneath Turan plate in Permian-Triassic. Fariman complex may be divided into upper and lower parts. At least two deformation phases may be recognized in upper part of the Fariman complex. second deformation phase caused creation fault propagation folds, and probably was coeval with main deformation phase of Eo-Cimmerian that affected Aghdarband basin. Deformation style in Fariman and DareAnjir complex is compatible with strain partitioning proposed for Aghdarband transpressional zone as a result of oblique convergence between Iran and Turan during Eo-Cimmerian event.
Z. Hosseinmardi; M. Ghorashi; M. R. Ghassemi; M. Talebian
Abstract
The outcrop of northern part of North Eshtehard Thrust has been selected for study of structural evolution and geological processes. The study area includes folding structures with different scales from regional to outcrop which belong to fault related folding category. Analysis of joints in the region ...
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The outcrop of northern part of North Eshtehard Thrust has been selected for study of structural evolution and geological processes. The study area includes folding structures with different scales from regional to outcrop which belong to fault related folding category. Analysis of joints in the region among upper red formation strata shows two main sets which are usually tensional (j1 & j2). These joints are visible in sandstone units of upper red formation and most of them are filled with gypsum. It is obvious that the j1 joints are younger than j2. j1 and j2 joints are related to folding processes. The local stress field which could be measured from the joint study is σ1=337/75, σ2=189/13 and σ3=077/03 and corresponds with the given paleostress direction for southern part of central Alborz.
M Foroutan; H. Nazari; B. Meyer; M. Sébrier; M. Fattahi; K. Le Dortz; M. Ghorashi; Kh. Hessami; M. R. Ghassemi; M. Talebian
Abstract
The evaluation of seismic potential along the Dehshir fault with 550-km length (by count of northern and southern splays) is critical considering that more than 3.5 million people live in cities and towns located at vicinity of the fault. The Dehshir fault is considered as westernmost limit ...
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The evaluation of seismic potential along the Dehshir fault with 550-km length (by count of northern and southern splays) is critical considering that more than 3.5 million people live in cities and towns located at vicinity of the fault. The Dehshir fault is considered as westernmost limit of N-striking dextral strike-slip faults set that slice Central and eastern Iran. Due to the lack of large recorded earthquakes (instrumental and historical) in Central Iran, access to seismic potential of active faults by studying the earthquake catalogs seems to be impossible. No instrumental earthquake has been recorded greater than mb 4.7 around the Dehshir fault and also historical data shows no evidence for occurrence of large earthquake around the fault. No sign of destruction in Marvast historical castle (at a less than 10 km far from the Dehshir fault) built in Islamic period (~700-1250), shows any remarkable seismic activity until 750-1300 years ago. However, several evidence of geomorphologic markers such as drainages, gullies, streams and alluvial fans offsets, represent activity of the Dehshir fault in Late Quaternary. Of Geomorphic evidence at Marvast and Harabarjan sites record dextral - slip on the Dehshir fault during the Late Pleistocene-Holocene as major movement with minor dip - slip component. Rake of the fault movement has been considered for assessing to amount of horizontal and vertical slip rate on the Dehshir fault. This value in the North Marvast site has been calculated ~10 degrees and according to right bank offset on the Marvast river is ~7 degrees with horizontal and vertical displacements of 13 m and 1.5 m, respectively. Combining cumulative offset markers with OSL dating implies the Dehshir fault in Late Pleistocene-Holocene time period slips at horizontal and vertical components about 1±0.3 and 0.1 mm yr-1, respectively. We observed a minimum dextral offset along the Marvast fault segment in west of Harabarjan about 2 m that allow us assuming the related magnitude and date of last large paleoearthquake on the Dehshir fault is about Mw 7 and 2000 years ago, respectively.
M. Esterabi - Ashtiani; A. Yassaqi; H. R. Javadi; M. Shahpasandzadeh; M. R. Ghassemi
Abstract
Dorouneh Fault is located in the north of Central Iran Microplate with left-lateral strike-slip mechanism and plays an important role in the formation of Iran plateau's morphology. Dorouneh fault, with bend geometry and 900 km length, extends from HyrmandRiver in the Afghanistan border to Anarak area ...
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Dorouneh Fault is located in the north of Central Iran Microplate with left-lateral strike-slip mechanism and plays an important role in the formation of Iran plateau's morphology. Dorouneh fault, with bend geometry and 900 km length, extends from HyrmandRiver in the Afghanistan border to Anarak area in the Central Iran. Dorouneh Fault terminates in the Jandaq area as sub-parallel branches. Towards west, general trend of Dorouneh Fault System changes from northeast-southwest to north-south in the north of Talmessi Mine. Fault branches are observed as left-lateral strike-slip faults with normal dip-slip component in the Jandaq-Talmessi area that is introduced as a trailing extensional imbricate fan. But, considering slip sense inversion along Dorouneh Fault, the main mechanism for formation of western termination before slip sense inversion is a trailing compressional imbricate fan.
M. Koohpeyma; M.R. Sheykholeslami; M.R. Ghasemi
Abstract
The metamorphic rocks around Mashhad city were suffered by several stages of metamorphism and deformation. Special mineral and structural elements were formed in these stages. Metamorphic grade in the pellitic rocks changes from green schist to amphibole facies. Foliations generally are steep toward ...
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The metamorphic rocks around Mashhad city were suffered by several stages of metamorphism and deformation. Special mineral and structural elements were formed in these stages. Metamorphic grade in the pellitic rocks changes from green schist to amphibole facies. Foliations generally are steep toward northeast. Lineations predominantly have gentel to moderate plunge (less than 30°) toward northwest. Kinematic analysis of ductile structures in outcrop and microscopic scale shows dextral strike slip shearing with reverse component from northwest to southeast in shear zones. Contrasting of kinematic analysis of mesoscopic folds coeval deformation with shear sense obtained from ductile shear zones indicates the strain partitioning in the area. Based on field analysis and microscopic studies, the rocks were deformed by two stages of ductile deformation and followed by brittle-ductile and brittle deformation in later stages. The first and second stages of deformation occurred in a progressive and continuous manner accompanied by the higher grade of metamorphism in the area. The main stage of metamorphism is contemporaneous with early Cimmerian orogenic phase.
M. Asadi sarshar; A. Bahroudi; M. Qorashi; M. R. Ghassemi
Abstract
Estimate of moment rate is comparatively reckoned as a new method for dealing with tectonic activities rate in different regions and it prepares the way for putting together different methods. In fact, moment rate states rate of energy which exists in deformation system. There are three different approaches ...
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Estimate of moment rate is comparatively reckoned as a new method for dealing with tectonic activities rate in different regions and it prepares the way for putting together different methods. In fact, moment rate states rate of energy which exists in deformation system. There are three different approaches to state moment rate that each one express tectonic motion and movement of a region from a particular view. These three approaches consist of: geodetic (surveying), seismic and geology methods. Geodetic method which is determined on the basis of gained strain rate tensor from geodetic data, shows deformation rate (including seismic and aseismic) that is happening in the region at this moment in time. Moment rate which has gained on the basis of historical and instrumental catalogues, shows the total released seismic energy during quake events which are available in earthquake of region and geologic moment rate which gained with geometric parameters of faults, reveals potential of the faults in releasing stored elastic energy in. Geodetic moment rate, seismic moment rate (on the basis of historical and instrumental earthquake data) and geologic moment rate are estimated for Central Alborz region. The most moment rate in the study area belongs to geodetic approach (8.83×1019 Nm/yr) and then geologic moment rate (0.12×1019 Nm/yr) and finally the least quantity belongs to seismic moment rate (0.022×1019- 0.046×1019 Nm/yr). Considering, distribution of earthquake epicenters, the most seismic energy is released in the south parts of Central Alborz and considering high geodetic and geologic moment rates in north parts, it seems, north parts of Central Alborz have higher seismic potential.
H. Amini; M. Fattahi; M. R. Ghassemi
Abstract
Doruneh is an active left- lateral strike- slip fault in North-East Iran. Surface trace of this fault is about 700 km long, and cuts across Quaternary and Tertiary deposits. In some places along the fault, sediments of Paleogene. Neogene, and alluvial fans of Quaternary age are displaced ...
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Doruneh is an active left- lateral strike- slip fault in North-East Iran. Surface trace of this fault is about 700 km long, and cuts across Quaternary and Tertiary deposits. In some places along the fault, sediments of Paleogene. Neogene, and alluvial fans of Quaternary age are displaced by the fault. Left- lateral displacement between 91-457 m are evident in Landsat images between east of Beiragh and east of Khalil-abad. Displacements are also evident in streams that are incised over the above mentioned deposits. We have tried to estimate the recent history of activity on the fault on the basis of the measured displacements and estimated slip rates of the fault. Estimated age of left- lateral movement inception on the fault is very much younger than the displaced geologic units. These observations indicate that Doruneh Fault has been mostly active during the last few millions, which in turn proves the fault to be an active structure.
H. R. Javadi; M. R. Ghassemi; M. Shahpasandzadeh; M. Estrabi Ashtiani
Abstract
Dorouneh Fault System (DFS) is located along northern border of Central Iran microplate. Its mechanism is left-lateral strike-slip with reverse dip-slip component. Considering curve geometry of DFS, it is divided into three major parts: eastern, middle and western. Middle part extends from Torbat-e-Heidarieh ...
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Dorouneh Fault System (DFS) is located along northern border of Central Iran microplate. Its mechanism is left-lateral strike-slip with reverse dip-slip component. Considering curve geometry of DFS, it is divided into three major parts: eastern, middle and western. Middle part extends from Torbat-e-Heidarieh city in the east to Anabad village in the west. It passes through Quaternary loose alluviums. DFS is composed of different segments in this part. Bend and right-lateral en echelon geometry at surface and left-lateral strike-slip movement of DFS cause local transpression that is observed as young folding. Fold core is composed of Neogene marl, sandstone and siltstone and fold limbs are composed of Pleistocene loose gravely sediments. Mentioned folds were formed by two different mechanisms: first, Anticlines that formed in right-step bends of DFS and second, pressure ridges that are limited among parallel branches and overlaps of DFS. Estimation of relative uplift rate along mentioned folds indicates that more earthquakes occur in regions with higher uplift rate.
H. Sa’adatnia; A. Javaherian; I. Abdollahi Fard; M. R. Ghassemi
Abstract
One of the duties of seismic interpreter is interpretation of the geological structures likely to be found at deeper levels. Such constructions form a key to the understanding of regional tectonics and they often play a vital role in industry. The exploration for oil and gas in particular ...
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One of the duties of seismic interpreter is interpretation of the geological structures likely to be found at deeper levels. Such constructions form a key to the understanding of regional tectonics and they often play a vital role in industry. The exploration for oil and gas in particular requires the best possible control on underground structures in order to locate drill holes for exploration investigation or for producing wells. Because the primary data are always incomplete and may be in part contradictory, the final interpretation should be at least geometrically validated. A powerful and independent test for the validity of a structural interpretation is the restoration of the structure to the shape it had before deformation. Restoration is a fundamental test of the consistency of the interpretation. It is best described by transformation equations which incorporate rigid translation and rotation plus deformation. A map or cross section can usually be restored by methods based on more than one kinematic model, and different methods will produce somewhat different restored geometries. It follows that any given restoration doesn’t necessarily represent the exact pre-deformation geometry. The internal consistency of the restoration by any technique constitutes a validation of the interpretation. In this study, the main aim is introducing the balancing of seismic interpretation and its application to decrease the errors of interpretation. For this purpose, length and area balancing were done at a sample seismic cross section from 3D seismic data of two oilfields at the East of Khuzestan (SW Iran). As a result, the primary interpretation was corrected and finally the corrected interpretation was compared with primary interpretation. For balancing of seismic sections in this area, the flexural slip technique is selected as optimum technique through testing line-length, vertical simple shear and flexural slip techniques.
A. Lashkari; M. R. Ghassemi; M. Qorashi
Abstract
The Caspian (Khazar) fault is the boundary between the Caspian plain and AlborzMountain. As a major tectonic feature, this fault may be considered as the northern mountain front fault of the AlborzRange. Subsidence of the Caspian Sea in north, uplift of the Alborz Mountain, and its over thrusting on ...
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The Caspian (Khazar) fault is the boundary between the Caspian plain and AlborzMountain. As a major tectonic feature, this fault may be considered as the northern mountain front fault of the AlborzRange. Subsidence of the Caspian Sea in north, uplift of the Alborz Mountain, and its over thrusting on southern part of South Caspian basin has occurred along the Caspian fault. In this paper, a segment at the fault which is located between longitudes 52° 30׳ and 53° 00׳ - in the northern part of geological map of Qaemshahr - is considered as a segment that does not outcrop. This paper introduces the general structural and morphotectonic characteristics of this zone and describes the characteristics of the active anticlines (growing folds) and morphotectonic effects in this zone such as effects on rivers.
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.
B. Vahdati Daneshmand; M.R. Ghassemi; M. Ghorashi; N. Haghipour
Abstract
According to historical maps of Iran, changing the course of Sepidrud from Dastak to Kiyashahr has occurred in a very recent time. Although migration of meandering streams over the delta plain is a natural phenomenon and oscillations of Caspian Sea might have affected the course ...
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According to historical maps of Iran, changing the course of Sepidrud from Dastak to Kiyashahr has occurred in a very recent time. Although migration of meandering streams over the delta plain is a natural phenomenon and oscillations of Caspian Sea might have affected the course of SepidrudRiver, the deflection of Sepidrud between Astaneh and Koochesfahan is probably related to activity of concealed structures wit
hin the delta deposits. This research uses calculation of morphotectonic indexes to study effects of active range boundary within range faults in study area on drainage pattern and river streams.
