Tectonics
Mohammad Reza Mazinani; Ali Yassaghi; Reza Nozaem
Abstract
The E-W trending Faghan fault system with >180 km in length located in the northern part of the Lut Block and south of the Dorouneh Fault in central Iran. The fault cut through basement rocks and all other younger units from Cambrian to Cenozoic. Kinematic and dynamic analyses of the Faghan fault ...
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The E-W trending Faghan fault system with >180 km in length located in the northern part of the Lut Block and south of the Dorouneh Fault in central Iran. The fault cut through basement rocks and all other younger units from Cambrian to Cenozoic. Kinematic and dynamic analyses of the Faghan fault system is crucial for understanding the tectonic framework of the northern part of the Lut Block. These field based investigation analyses of the Faghan fault system indicates the E-W trending dextral strike- slip shear kinematics for the fault system and as Principal Deformation Zone (PDZ) along which minor sinistral, dextral and dip slip faults have also formed as second order riedel shears. Therefore, like the Kuh-e-Sarhangi fault zone, the Faghan fault system is considered as one of the fundamental fault zone in the north of the Lut Block caused the deformation partitioning in the block during Late Cenozoic. Accordingly, the Faghan fault system divorces the Bardacan-Kashmar and Gonabad micro-blocks from each other and transfers the deformation from the main Lut Block into its northern micro-blocks by Intraplate escaping tectonics.
Tectonics
Ali Bandegani; Ali Yassaghi; Mohsen Eliassi
Abstract
In this paper, the structural evolution of Bamu fault zone located in the Zagros folded belt zone is presented as an example of northeast-trending fault zone in the Zagros, using the kinematic and dynamic analysis of accompanied structures. Based on structural and paleostress analyzes two phases of shortening ...
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In this paper, the structural evolution of Bamu fault zone located in the Zagros folded belt zone is presented as an example of northeast-trending fault zone in the Zagros, using the kinematic and dynamic analysis of accompanied structures. Based on structural and paleostress analyzes two phases of shortening were determined as NE and NNE. In order to define the chronology of the deformation stages in the region, the relationship between fault structures and folds in the folded rock formations has been utilized. The result showed that the first compression stress trend in the area was NE that caused formation of the Bamu transverse Fault with left-lateral strike-slip mechanism and its accompanied structures. Since this stage of deformation has affected the Oligocene- early Miocene formations, more likely occurred at this time. During the next phase the shortening direction, due to change in the collision zone direction of the Arabian-central Iran in the Miocene-Pliocene, has changed to NNE which causes development of younger structures in the form of folding and reverse faulting in the fault zone. This shows that the NE-trending fault zones, like other major NW-faults, in Zagros affected by the change in the convergence of Zagros collision.
Tectonics
Mohammad Ali Ghanbarian; Ali Yassaghi
Abstract
This research has presented the results of the structural and microstructural analyses of the Faryadoun region which is located in the NE of the Fars province. In this research, a new NW-striking belt has been introduced in the central part of Zagros hinterland and NE of the Sanandaj-Sirjan metamorphic ...
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This research has presented the results of the structural and microstructural analyses of the Faryadoun region which is located in the NE of the Fars province. In this research, a new NW-striking belt has been introduced in the central part of Zagros hinterland and NE of the Sanandaj-Sirjan metamorphic belt. The mean attitudes of the foliation and lineation in this new belt are 315˚, 57˚ NE and 23˚, 116˚, respectively. The study of kinematic indicators revealed the occurrence of a sinistral top-to-the NW shear in this new belt which is different with the known dextral deformation in the central region of the Sanandaj-Sirjan metamorphic belt.
Tectonics
Mojtaba Ershadinia; Saeed Madanipour; Ali Yassaghi
Abstract
Faraghun Mountains are located in the south eastern part of the Zagros orogen. Early Ordovician- Permian rock units are deepest stratigraphic units exposed in the central part of the Faraghun Mountains. High Zagros Fault (HZF) is the main structural feature bordering southern flank of these mountains. ...
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Faraghun Mountains are located in the south eastern part of the Zagros orogen. Early Ordovician- Permian rock units are deepest stratigraphic units exposed in the central part of the Faraghun Mountains. High Zagros Fault (HZF) is the main structural feature bordering southern flank of these mountains. Here we combine detailed mapping, field based structural kinematic analysis and cross sections to reconstruct structural evolution of the Faraghun Mountains. Our new structural and stratigraphic analysis document three kinematically and geometrically different western, central and eastern segments for HZF in the Faraghun Mountains. Eastern and western segments of HZF, those are dipping northward, are connected together with Zakin Fault that dipping to south. Late Paleozoic successions have exposed in the hanging wall of Zakin Fault and central segment of HZF in a pop-up geometry. Stratigraphic records document prominent variation in late Cretaceous sequences including Gurpi Formation in the Hanging wall and footwall of the HZF in the Faraghun Mountains. Higher thickness and basal conglomeratic nature of Gurpi Formation in the hanging wall of HZF with respect to its footwall might reflect normal kinematics of the HZF during late Jurassic-early Cretaceous time. All the stratigraphic and structural evidence represent post late Cretaceous compression accompanied by late Cenozoic right lateral transpression in Faraghun Mountains at SE Zagros.
Tectonics
Mohammad Moumeni Taromsari; Maryam Dehbozorgi; Reaza Nozaem; Ali Yassaghi
Abstract
Kalmard fault is considered as one of the fundamental faults in central Iran zone. The Ozbak Kuh mountains with a NE-SW strike are located in central Iran in the Kalmard fault zone. Hence, analyze the folds and faults in this deformed zone can aid in the understanding of structural evolution of this ...
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Kalmard fault is considered as one of the fundamental faults in central Iran zone. The Ozbak Kuh mountains with a NE-SW strike are located in central Iran in the Kalmard fault zone. Hence, analyze the folds and faults in this deformed zone can aid in the understanding of structural evolution of this area in central Iran. In this study, field operations and geometric-kinematic analysis of folds and faults, also study of their structural evolution are integrated in order to provide a better understanding of the structural evolution of the Ozbak Kuh area. The results display that before Cretaceous period the Ozbak-Kuh area was influenced by a compressional regime with a prependicular trend with respect to the Kalmrad fault that it caused the formation of folds and faults paralell to folds axial plane trends, after that compressional regime changing to a dextral strike slip regime in Cenozoic in direction of NE- SW, all structures in the study area such as, faults, folds axial plain and other related structures were influenced by the aforementioned strike slip stress. Generally the geometric- kinematic pattern of faults in the study area regarding to the major and R, P, R', and X faults is kind of simple shear and contraction parallel to deformed zone. In this pattern the simple shear is dominant and compression is trivial component. The mechanism of the faults in the study area shows that the deformation of the Ozbak Kuh mountains is toward the final stages of simple shear. The multiple steps of deformation, simple shear movements and intensity of deformation in the study area caused that the strike of all structures is to be in direction of NE-SW that it is parallel to the main fault zone.
S. A. Atapourfard; A. Yassaghi; M. Rezaian; E. Shabanian
Abstract
In the east of high Zagros – in Faraghan Anticline- sedimentary cover with more than 10 km thickness has decoupled from basement above the Hormuz salt and has deformed. Mention anticline is cut by High Zagros Fault. By attention to lack of paleostress study and kinematic interpretation on north ...
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In the east of high Zagros – in Faraghan Anticline- sedimentary cover with more than 10 km thickness has decoupled from basement above the Hormuz salt and has deformed. Mention anticline is cut by High Zagros Fault. By attention to lack of paleostress study and kinematic interpretation on north east of Fars Arc structures, in this paper we reconstructed stress field and interoperated its role in evolution of Faraghan Anticline. Inversion method used for determination of reduced stress tensor parameters and discrimination faults of every brittle tectonic phase. Maximum shortening axis determined by using Stylolite's and attitude of Minimum main stress determined by using veins. The present stress field was calculated by inversion of earthquake focal mechanism data. According to our data and the deduced results, some of veins developed with an N27° - 29°E direction of σ1 stress axis before late of middle Miocene (before folding and faulting). During the late Miocene, sedimentary cover deformed as detachment and faults related folds in a general compressional stress regime with an N27° - 29°E direction of σ1. The basement faults were reactivated during late Miocene- early Pliocene in a general strike slip regime with an N4°E direction of σ1 stress axis. The High Zagros Fault was reactivated at that time and cross- cuts the entire cover section and its associated structures. In the late Pliocene, direction of σ1 stress axis temporally changed to N025°W in strike slip tectonic regime. Strike- slip and reverse faults were reactived in new stress field. Earthquakes Focal mechanism data analysis indicate that direction of σ1 stress axis is N-S now.
E. Gholami; S. Shoraka; A. Yassaghi
Abstract
The East-West to Northwest-Southeast trending Ashkhaneh fault zone is located in northeast of Iran between the Alborz and Kopeh-dagh tectonic zones. Geometric and kinematic characteristics of Ashkhaneh fault zone was revealed by measuring of fault kinematic indicators such as: S-C structures, asymmetric ...
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The East-West to Northwest-Southeast trending Ashkhaneh fault zone is located in northeast of Iran between the Alborz and Kopeh-dagh tectonic zones. Geometric and kinematic characteristics of Ashkhaneh fault zone was revealed by measuring of fault kinematic indicators such as: S-C structures, asymmetric folds, slip lines and fault steps along eight cross-sections across this fault zone and perpendicular to main structures. Stereographic analysis of the measured structural elements and constructing cross-sections show a dominant reverse mechanism with left-lateral strike-slip component for the Ashkhaneh fault zone. Donghozdagh Anticline in the hanging wall of Ashkhaneh fault zone is a fault-propagation fold. To the east and in the hanging wall of the fault zone, several thrust faults such as Kuh-e-Docheng fault, North Beruj fault and South Beruj fault have the same geometrical characteristics of the Ashkhaneh fault zone. These thrusts in hanging wall of the Ashkhaneh fault zone with dip to north (same as Ashkhaneh fault) are evidences for of the occurrence of greater convergence in southeast than the northwest part of the Ashkhaneh fault zone. Eight structural cross-sections perpendicular to the Ashkhaneh fault zone show evolution of thrusts and fault-related folds, as well as migration of rock units toward south-southwest in this area. The arrangement of these thrust fault systems emphasis that structural growth took place from north to south-southwest in this part of the Kopeh-dagh.
M Ehteshami-Moinabadi; A Yassaghi
Abstract
The assessment of deformation condition of the Mosha Fault during Middle-Late Miocene carried out using microstructure and thermometry of fluid inclusions within calcite veins in the fault zone. Based on intra-crystalline deformation of quartz grains, calcite twin, and thermometry of primary fluid inclusions ...
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The assessment of deformation condition of the Mosha Fault during Middle-Late Miocene carried out using microstructure and thermometry of fluid inclusions within calcite veins in the fault zone. Based on intra-crystalline deformation of quartz grains, calcite twin, and thermometry of primary fluid inclusions in the calcite veins inside the Mosha fault zone, the maximum estimated deformation temperature of the Mosha fault is 350o c during Tertiary. Calculated pressure of the fault zone using fluid inclusion data is an underestimation of real pressure because the calcite veins formed in the last stages of deformation. Considering the tectonic setting of South Central Alborz and assuming a geothermal gradient ranging between 25-35oc/Km for the region from Eocene to the late Miocene, the maximum temperature of 350o c represents the depth between 10 to 14 Km in adiabatic condition. This depth range means a fault zone pressure between 2.5 to 4 kbar for the Mosha Fault zone during Tertiary, which is in correlation to recent seismic data that confirmed maximum fault activity in the depth between 10 to 15 Km.
B Derikvand; A Yassaghi
Abstract
The folding style analysis is one of the initial investigations on hydrocarbon reservoirs anticlines. Nader Anticline is located in the western part of the Eastern Kopeh Dagh zone and on hanging wall of the North Kopeh Dagh Reverse Fault. The structural analysis of the anticline is carried out along ...
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The folding style analysis is one of the initial investigations on hydrocarbon reservoirs anticlines. Nader Anticline is located in the western part of the Eastern Kopeh Dagh zone and on hanging wall of the North Kopeh Dagh Reverse Fault. The structural analysis of the anticline is carried out along eight structural transects across the fold. This analysis showed that the Nader Anticline has two culminations with an en echelon arrangement. These culminations as well as the other folds in the study area are cross cut by a series of NW- and N- trending strike-slip faults. The Nader Anticline first culmination is analyzed as fault propagation fold geometry, while its second culmination is examined as fault detachment fold geometry. Since the Nader Hidden Fault cuts the north limb of the first culmination; the geometry of this culmination can also be considered as faulted detachment fold. The study area faults though have different trends but they dominantly have strike-slip mechanism or strike-slip component and thus, can be considered as Riddle shear faults. Geometric and kinematic analysis of these faults showed that a series of these faults could be considered as shear fractures related to a NW-trending PDZ, while the other faults can be examined as Riddle shears related to a N-trending PDZ. Such development of the Riddle shears faults as well as en echelon arrangement of the Nader Anticline culminations imply that the study area is structurally evolved during a NW-trending oblique-slip fault system more likely related to transpressional activity of the North Kopeh Dagh Reverse fault zone.
M Najafi; A Yassaghi; A Bahroudi
Abstract
Mechanical characterizations of sedimentary cover, especially presence of ductile rock units is a major controlling parameter on deformation style within fold and thrust belts. Interpretation of seismic profiles as well as scaled analogue modeling allows us to determine the influence of ductile levels ...
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Mechanical characterizations of sedimentary cover, especially presence of ductile rock units is a major controlling parameter on deformation style within fold and thrust belts. Interpretation of seismic profiles as well as scaled analogue modeling allows us to determine the influence of ductile levels on structural style in the Central Zagros folded belt. Seismic interpretation indicates that the Miocene Gachsaran Formation forms a major median detachment level decoupling fold geometry in surface structures from Pre-Miocene units below it. In addition, the Infra-Cambrian Hormoz salt or equivalents decouple the folded sedimentary cover from basement. To evaluate the significance of multiple detachment levels, a scaled analogue model was set. Two layers of silicon putty, with thicknesses equal to 15% of total cover thickness, were placed at the base and in the middle of sedimentary cover. The rest of the sedimentary cover was simulated using dry loose sand. The result of modeling supports seismic interpretation of the Central Zagros proposing that thick middle detachment layer totally decouples structural style at surface from depth. However, the open synclines with long wavelength and low angle thrusting are developed at surficial levels, and duplex thrust systems are formed between two detachment levels. Therefore, the role of ductile detachment levels should be obtained before exploring deep hydrocarbon targets in the Zagros fold belt.
S. Sadeghi; A. Yassaghi; M. Fathollahi
Abstract
In this paper, the structural relationship between two main structural features of the Zagros suture zone, that is, the Main Zagros Reverse Fault (MZRF) and the Main Recent Fault (MRF) in Kurdistan area has been studied in more detail. This provides information as to the structural evolution and seismotectonics ...
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In this paper, the structural relationship between two main structural features of the Zagros suture zone, that is, the Main Zagros Reverse Fault (MZRF) and the Main Recent Fault (MRF) in Kurdistan area has been studied in more detail. This provides information as to the structural evolution and seismotectonics of the Zagros suture zone. Around latitude 36, the Sardasht segment of the MRF cut the MZRF and toward southeast part of this intersection, the MRF is the only major fault between the Zagros fold- thrust belt and the Sanandaj- Sirjan zone. Here, segments of the MZRF can be seen in the MRF zone, which represents the younger activity of the MRF. Our investigation show that there is a right- hand bending between the Piranshahr Fault in the northwest and the Marivan Fault in the southeast (between latitudes 35 ̊, 30' and 36 ̊, 30'). On the southwest and northeast edges of this releasing bend, the Sardasht and Baneh faults are located that have both strike-slip and normal components. Considering geometric and kinematic aspects of the curved segment of the MRF (Sardasht Fault), as well as the paleostress studies of this segment, it can be said that the Sardasht Fault with N30W trending fault has deviated from the main displacement vector (N60W) and hence has a normal component. Therefore, this fault accommodates dextral and transpressional movements between the Zagros fold- thrust belt and the Sanandaj-Sirjan zone and its normal movements arising from the right hand bending of the MRF. Paleostress analysis (using the Multiple Inverse Method) shows separate stress fields for different movements. Paleostress fields have a close correlation with the stress fields obtained from the focal mechanism of the earthquakes located along the Zagros suture zone. This correlation shows that the obtained stress fields are belong to younger activity. Displacement of the MZRF by the MRF caused significant heave in the MZRF and thus it does not expose at the surface between latitudes 35 ̊, 20' and 36 ̊, 00'.
A. Yassaghi; H. Narimani; M. Gh. Hasan goodarzi
Abstract
Structures in fold-thrust belts such as Zagros which are developing mainly along the belt strike often terminate at the transverse structures. The Zagros Mountain Front Fault has cut and displace at different parts by transverse structures. At Dowgonbadan area this fault is intersected by the Kharg-Mish ...
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Structures in fold-thrust belts such as Zagros which are developing mainly along the belt strike often terminate at the transverse structures. The Zagros Mountain Front Fault has cut and displace at different parts by transverse structures. At Dowgonbadan area this fault is intersected by the Kharg-Mish transverse structure. The Mish anticline has transported fault propagation geometry and located on hanging wall of the Mountain front fault. The anticline plunges and rotates when it reaches to the Kharg-Mish transverse fault to the west. In the fault footwall, however, the Dil, Pahn, Sarab and Jafarabad anticlines have rounded geometry and low amplitude show characteristics of the Dezful Embayment zone folds. The Dil and Pahn anticlines with bifurcate geometry and outcrop of Asmari Formation develop parallel to the frontal ramp strike and show footwall anticlines that propagated from the frontal ramp at Dashtak formation as delay structures with respect to the hanging wall structures. The Kharg-Mish fault identify as a lateral ramp on the surface by termination of longitudinal structures and at the depth with thickness and facies changes of the Ilam Formation. The structural characteristics of the Dowghonbadan area in the Zagros Fold-Thrust Belt are analyzed as the interaction of the Mountain Front fault and the Kharg-Mish transverse fault as the frontal and lateral ramps, 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.
Z. Davoodi; A. Yassaghi
Abstract
Geometry and kinematics analyses of structures developed along one of the transverse fault zone (Izeh) in the Zagros fold-thrust belt has been presented to document the origin and to present the effect of this fault zone on the belt structures. Surface deformation of Izeh fault zone on the cover sediments ...
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Geometry and kinematics analyses of structures developed along one of the transverse fault zone (Izeh) in the Zagros fold-thrust belt has been presented to document the origin and to present the effect of this fault zone on the belt structures. Surface deformation of Izeh fault zone on the cover sediments are including changes on the Zagros major structures trends and development of minor structures (such as minor folds and faults) that are overprinted on the belt major structures. Detaeled structural mapping showed the precense of three major restraining zones between the mapped subsurface en-echelon faults along the Izeh fault zone in the Zagros fold-thrust belt. Analysis of isopach maps, facies variation of formations together with interpretation of seismic reflection profiles showed that these subsurfase faults are younger orders of the Izeh fault zone reactivation as a basement fault. Oblique convergence of the Arabian Plate toward the Central Iran is in favor for the reactivation of the fault zone and formation of surface deformations along it. Based on earthquake data this reactivation is continuing until the present time. The result of this study can be used for interpretation of deformation on the sedimentary cover along the similar transvers fault zone in the Zagros fold-thrust belt.
A. H. Sadr; Mohammad Mohajjel; A. Yasaghi
Abstract
The style of deformation changes from the hinterland (Sanandaj-Sirjan zone) to the foreland (Zagros) through the Zagros Orogen containing thick-skinned and thin-skinned deformation respectively. NW-SE trending thrust faults dipping to northeast have carried the older rock sequences to the surface. The ...
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The style of deformation changes from the hinterland (Sanandaj-Sirjan zone) to the foreland (Zagros) through the Zagros Orogen containing thick-skinned and thin-skinned deformation respectively. NW-SE trending thrust faults dipping to northeast have carried the older rock sequences to the surface. The Zagros collision zone could be divided into two distinct parts based on deformation mode that is separated by the Main Zagros Thrust. The southwestern part contains imbricate thrust sheets instead, to the northeastern part large amount of shortening is documented by basement deformation with duplex structures. Abundant crystalline deep origin thrust sheets have transported (2 up to 20 km) the metamorphic rock units upon the Zagros suture zone by gravity or tectonic forces. Despite the collision thrust faults, both NW oriented (Main Recent Fault) and NE oriented (named here Azna Fault) basement wrench faults have also activated and caused different style and amount of deformation in the collision zone.
A. Aflatounian; A. Yassaghi; A.H. Ahmadnia
Abstract
Soltan anticline is located in northwest of the Zagros fold-thrust belt in the LorestanProvince. Geometric and kinematic analyses of the anticline have been carried out to estimate the closure of the Dehram Group in order to evaluate its potential for gas reservoirs. Geometric ...
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Soltan anticline is located in northwest of the Zagros fold-thrust belt in the LorestanProvince. Geometric and kinematic analyses of the anticline have been carried out to estimate the closure of the Dehram Group in order to evaluate its potential for gas reservoirs. Geometric analyses of the Soltan anticline indicate that the fold geometry is rather similar to that of the Trishear type of fault propagation folds. However, considering the competency contrasts between various rock units in the anticline that control the fold’s geometry, together with the rounded and relatively wide outline of the anticline at surface, the Soltan anticline can also be compared to faulted detachment folds that hold the same geometry as the fault propagation folds. On the other hand, the very low values of finite strain measured on clastic rocks collected from the anticline and its typical smaller scale fold constraint, and the low values of the layer parallel shortening are comparable to the kinematics of fault propagation folds. Based on the data from the geometric and kinematic analyses, seven structural cross sections across the anticline are drawn, and using the cross sections, a structural contour map and a 3D model for Dehram Group are constructed. The calculated values for the anticline closure prohibits this structure as an appropriate host to gas reservoirs, unless the Soltan anticline is connected to the adjacent, Rit, anticline.
E. Gholami; M. A. A. Nogole sadat; M. M. Khatib; A. Yassaghi
Abstract
Right lateral shear between Central Iran and Afghanestan caused activity of N-S and NW-SE fault zones in eastern Iran. Faults interaction effect on creation of restraining zones and out-crop of ophiolitic rocks along fault zones. Study of geometric and kinematic of structures approache to recognition ...
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Right lateral shear between Central Iran and Afghanestan caused activity of N-S and NW-SE fault zones in eastern Iran. Faults interaction effect on creation of restraining zones and out-crop of ophiolitic rocks along fault zones. Study of geometric and kinematic of structures approache to recognition of structural evolution in fault zones of North-North East Lut plain (north part of Sistan structural zone).
The activation of different structural trends in eastern Iran , Sistan zone , causes a deformation style which is significant different from nearby structural zones. This is referred to the interaction of faults with dominant strike slip mechanism and different N-S and NW-SE trends. This interaction with the greater effect of N-S trends causes development of restraining zones and curved fold axial trends in area between the en-echelon areas of the N-S tending faults.
From point of view of structural geology the study area could be divided in two main parts:
A) Activity of N-S strike slip right-lateral fault zones construct wall damage zones and tip damage zones. En-echelon N-S faults construct link damage zones with ophiolitic out-crops in the overlap area (such as Kasrab and Torshab).
B) Fault zones with NW-SE trend, have right-lateral shear with compressional component mechanism (such as SE Birjand and SE Qaen) that has resulted to a broad and continuous out-crops of ophiolitic rocks. Shortening of folded sedimentary rocks (Tertiary) increased in eastern Sahlabad (Hosseinabad, Pureng, Chakhoo, Shourak, Marghzar, Zahab)from north to south. As an accepted theory displacement increase toward the center part of faults, that could be seen Shooshk- Cheshmehzangi fault zone. This suggests that shortening is related to the fault movement. Unconformity between Tertiary and Cretaceous rocks, out-crop of ophiolitic rocks in the compression area, existence of NE-SW compressional axes along two major trends and growing of fault damage zones in the crossing of two major trends in the NNE Lut plain, demonstrate that major mentioned trends had contemporaneous activity. In the restraining zones , thrust faults causes surface emplacement of older ophiolitic rocks. The more exposure of these older rocks and presence of thrust faults in northern portion of the study area where NW-SE trending faults are abundant, imply the greater effect of the N-S trending faults. Since the major shortening axes in the Sistan zone are considered to be constant , increase in deformation through shortening measurements of the folds also constrain the greater effect of the N-S trending faults.
M. A. Ganjavian; S. Shahriari; A. Yassaqi
Abstract
Fars region in southwest Iran lies at the Zagros foreland and is bounded to the north and east by the Zagros thrust, to the west by the Kazerun fault, and to the south by the HormozStrait and the Persian Gulf. Thrust faults and associated folds are the main structures in the Fars region. The structures ...
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Fars region in southwest Iran lies at the Zagros foreland and is bounded to the north and east by the Zagros thrust, to the west by the Kazerun fault, and to the south by the HormozStrait and the Persian Gulf. Thrust faults and associated folds are the main structures in the Fars region. The structures are trending NW to SE, the same trends as in the Zagros fold- thrust belt. The structural analysis of four anticlines in the interior Fars region based on the interpretation of seismic reflection lines and construction of structural sections on the basis of well data and field measurements indicates that fault propagation folds and fault detachment folds can be distinguished taking into consideration the geometry of the folds and the fault-fold relations. Based on measured parameters, the Ghareh Bulagh anticline is consistent with a fault propagation structure, while the Derz and Shirkhan anticlines with fault detachment structures. According to seismic reflection profiles and structural cross sections, the Chahkileh antiform is converted to a syncline at depth. The extent of shortening, based on the balanced structural cross sections, has been calculated to be around 14 percent.
S. Madanipour; A. Yassaghi
Abstract
Taleqan Mountains located in South-Central Alborz range accommodate one of the best stratigraphic sequences of the range. The area bounded by the Taleqan fault in the north and the Mosha fault in the south. These faults separate Paleozoic-Mesozoic rocks from southern and northern Tertiary rocks. In this ...
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Taleqan Mountains located in South-Central Alborz range accommodate one of the best stratigraphic sequences of the range. The area bounded by the Taleqan fault in the north and the Mosha fault in the south. These faults separate Paleozoic-Mesozoic rocks from southern and northern Tertiary rocks. In this paper structural geometry of these faults is analyzed to unravel structural evolution of the range which interpreted to be initiated as inversion tectonics then followed by transpression tectonics. The Mosha fault in the eastern part of the Mountains has high angle and thrusts Precambrian rocks, cored a large Hangingwall anticline, over the Tertiary rocks accommodate footwall synclines. This geometry constrains the fault as a deep-seated basement fault which has been developed through inversion of an initial normal fault. The Taleqan fault consequently is analyzed as a back thrust to the Mosha fault and the mountain as a pop up zone between them. Detail kinematic analysis of the Taleqan fault show two different reverse movement with right and left lateral components. Given that the fault located on the Mosha fault hangingwall, it has been analyzed that the former movement direction to be related to the Mosha fault inversion from Late Cretaceous while the latter movement direction is the consequence of left lateral transpression tectonics in the range since late Pliocene.
