Tectonics
Zahra Tavazo; Ebrahim Gholami; Hossien Motamedi; Bahman Soleimany
Abstract
Numerous mechanisms are active during folding in folded-thrust belts, such as the role of salt movement, the role of multiple detachments in sedimentary cover, interference between different phases of deformation, and the role of basement during folding. The performance of these mechanisms plays an important ...
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Numerous mechanisms are active during folding in folded-thrust belts, such as the role of salt movement, the role of multiple detachments in sedimentary cover, interference between different phases of deformation, and the role of basement during folding. The performance of these mechanisms plays an important role in the formation of different structures and geological features in geological units and folds geometry. In this research, such structures have been introduced and studied in Takhteh, Nahreh and Kuh-e-Lar anticlines in the north of Fars Paleo-High during field observations and measurement of geometric features of anticlines such as Aspect ratio, axial distance and half wavelength. These structures mainly include growth strata, geometry of tectonic synchronous strata, structures associated with shallow detachment such as rabbit ear structures, faults that are themselves structures that control the geometry and kinematics of structures, and sulfur springs that related to faults and rheology of exposed formations. The present study shows that the anticlines have an aspect ratio less than ten and are part of the detachment folds in which the detachment horizons have played a role and have a dextral arrangement. The formation of these anticlines occurred at the same time, which will be connected to each other, and these anticlines are associated with basement faults. The location of these anticlines is suitable for the presence of hydrocarbons but the basement fault in the southern flank of Takhteh anticline may affect the reservoir. The presence of water gaps and wind gaps in the region is a sign of uplift and activity of the region.
Tectonics
Ebrahim Gholami; Asghar Ahmadi; mohammadmahdi Khatib; Saeed Madanipour
Abstract
Located at the Arabia-Eurasia collision zone, the E-W trending Bozgoosh Mountain aligned perpendicularly to N-S trending Chehel-Nour Mountain in the northwest of the Iranian Plateau. There is not any thermochronometry study has been performed to determine the initial time of their uplift and exhumation. ...
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Located at the Arabia-Eurasia collision zone, the E-W trending Bozgoosh Mountain aligned perpendicularly to N-S trending Chehel-Nour Mountain in the northwest of the Iranian Plateau. There is not any thermochronometry study has been performed to determine the initial time of their uplift and exhumation. Our low-temperature Thermochronometry analysis in the apatite U-Th/He (AHe) system in combined with previously unpublished data set at central Bozghush Mountains and structural data show that the onset of the Late Cenozoic uplift and exhumation of the Bozgoosh Mountain (~19-25 Ma) is a bit older than Chehel-Nour - Gaflankuh Mountain (~15 Ma). It seems that deformation of the Bozgoosh Mountains started at with respect to middle Miocene unset time of deformation at Chehl-Nour and Gaflankuh Mountain. Then it can be concluded that these two perpendicular maountain ranges have not been formed in a single phase of partitioned deformation. On the other hand N-S trending Chehel-Nour and Ghaflankuh Mountains have similarly deformedsynchronous with the N-S trending part of the southern Talesh Mountains in its eastern border. Our results have also document that the Bozgoosh and Chehl-Nour mountains intersection is actually a part of Bozgoosh mountain.
M Shayanfar; M Ghorashi; S.J Ahmadi; A Saeedi; A.R Shahidi
Abstract
The existence of a sedimentary basin with a large thickness of Neogene sediments(Lower Red Formation) in the Anarak-Talmessi region of central Iran with a basement of Precambrian metamorphic rocks, high rate of erosion processes, and more importantly its safety necessity led us to define the structural ...
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The existence of a sedimentary basin with a large thickness of Neogene sediments(Lower Red Formation) in the Anarak-Talmessi region of central Iran with a basement of Precambrian metamorphic rocks, high rate of erosion processes, and more importantly its safety necessity led us to define the structural pattern and analyze its active tectonics and seimotectonics. In this regard, field observations, processing of satellite images, and investigation of eroded landforms were used. According to the lack of Qom and Upper Red Formations and faulting plus aseismic characteristics of the area up to a radial distance of 86 km, it can be concluded that a combination of a stair-step uplift-erosion system has controlled the basin, which caused its scarp shape and lack of younger sediments.
M Nazemi; M Qurashi; M.R Ghassemi; M Arian
Abstract
Geomorphic characteristics of alluvial fans on the sides of the ShotoriMountains in east of Tabas represent two different groups . The first group is older and is more dominant with their heads near the ShotoriMountains' hillside and their toe spreading to the central parts of the plain. These alluvial ...
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Geomorphic characteristics of alluvial fans on the sides of the ShotoriMountains in east of Tabas represent two different groups . The first group is older and is more dominant with their heads near the ShotoriMountains' hillside and their toe spreading to the central parts of the plain. These alluvial fans on which no main recent channel sedimentation is occurring, are often consisted of old alluvial sediments with a thin cover of newer ones. The second group includes younger and active alluvial fans consisted of more recent sediments of stream bed, which are located at the termination of the first group or at the southern foothills of the ShotoriMountains. It can be said that in the first group, recent active sedimentation process by the main channel has been transferred to the lower parts and toe of the alluvial fan, but in the latter group sedimentation has been done on top of the alluvial fan and on older sediments. In other words, the first group consists of two obvious old and active (recent) parts, while the second group only includes recent and active alluvial fans. Our investigations indictaes that geomorphic pattern of these two alluvial fan groups has a clear relation with location and mechanism of active faults and geomorphic surfaces in the plain of Tabas and eastern slopes of the Shotori Mountains; in other words, it is related to the mechanism of structural evolution of this mountain. According to this pattern, wherever there is the active fault of the catastrophic 1978 earthquake at the front of mountain along which the ShotoriMountains are being uplifted, the second type of alluvial fans is formed. Where the fault is located in central parts of the plain as a result of deformational front propagation, and the old part of the alluvial fan and mountain are being uplifted along it, the first type of alluvial fans (with two separate parts) is formed. This uplift is accommodated by active faulting and folding associated with bedding plane faulting. Migration of deformational front during geologic evolution of the ShotoriMountains has caused four different geomorphic levels along with three generations of alluvial fans. It is concluded that investigating on geomorphic pattern of alluvial fans will provide valuable data about the location of active Quaternary faults in alluvial plains. This pattern shows an active fault near Boshruyeh (east of the ShotoriMountains). Although no major earthquake has been reported from the fault, all morphotectonic evidences show its activity and thus the occurrence of large earthquakes in the future is expected.
N Bagha; M Ghorashi; M Arian; M Pourkermani; A Solgi
Abstract
Structural development, caused by active tectonics leads to deformation of morphology features. The Mosha-North Tehran fault zone, located in south edge of the Central Alborz consists of significant tectonic structures. Hence, study on morphotectonic signs is a proper method for evaluation of relative ...
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Structural development, caused by active tectonics leads to deformation of morphology features. The Mosha-North Tehran fault zone, located in south edge of the Central Alborz consists of significant tectonic structures. Hence, study on morphotectonic signs is a proper method for evaluation of relative tectonic activities in the area. In this research, six main morphometric indices such as stream length-gradient (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height(Vf), drainage basin shape (Bs), and mountain front sinuosity(Smf)were considered. The computations and probes of these indices indicate three classes of relative tectonic activity in the study area from low to high level. Consequently, the drainage basins with high class of tectonic activity mostly coincide with the main faults in south edge of the Central Alborz.
