Tectonics
M. Kouhpeyma; M. Talebian; L. Chen; A. Ghods; M. Ghorashi
Abstract
The Kopeh Dagh and Binalud-Alla Dagh mountains are important structural elements located in the northeastern boundary of Arabia-Eurasia collision zone. Due to existence of large cities with a long history of civilization, there is a relatively rich body of data on historical seismicity in this area. ...
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The Kopeh Dagh and Binalud-Alla Dagh mountains are important structural elements located in the northeastern boundary of Arabia-Eurasia collision zone. Due to existence of large cities with a long history of civilization, there is a relatively rich body of data on historical seismicity in this area. Nonetheless, little adequate instrumental seismic data were available prior to this study. In this paper, we utilized the temporary China-Iran local seismic network data deployed in the area for 13 months. Based on this data, we determined 37 focal solutions through first motion polarity approach suggesting a combination of strike-slip, reverse and normal mechanisms. There is a significant concentration of epicenters and focal mechanisms around the eastern Alborz - Kopeh Dagh boundary along the Atrak River. The southern and western boundaries of the Binalud Mountains also show relatively high seismic activities. The Local magnitude (ML) of the events ranges from 3.5 to 4.9 with depths of up to 20 km, mostly concentrated at ~10 km. The principal stress axes and slip vectors obtained from the focal mechanisms agree well with kinematic state of main faults and tectonic regime of the area, confirming the seismogenic nature of these faults. In addition, they are consistent with right-lateral component of slip along thrust faults in eastern Kopeh Dagh and Binalud and both laft- and right-lateral motions in the central Kopeh Dagh.
S. Dashti Chandanagh; M. R. Sheikholeslami; J. Taheri
Abstract
This study was conducted to determine the deformation pattern of the Mashhad metamorphic rocks which results from the convergence between Turan and Central Iran plates and closure of Paleotethys Ocean during Early Cimmerian event. The results of 2D and 3D strain analysis show that the maximum deformation ...
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This study was conducted to determine the deformation pattern of the Mashhad metamorphic rocks which results from the convergence between Turan and Central Iran plates and closure of Paleotethys Ocean during Early Cimmerian event. The results of 2D and 3D strain analysis show that the maximum deformation is concentrated in the central part of the study area and most strain shape parameters (K) obtained from oriented samples are located within the flattening part of the Flinn diagram. Strain intensity parameter in most cases is less than 0.5 and a maximum strain occurred in the central part which is reduced towards the margins. This is the most characteristic of the typical shear zones in which, the maximum strain is concentrated on the central part. Calculated vorticity numbers is ranged between 0.2 to 1 indicating the presence of both pure shear and simple shear during a transpressional regional deformation.
M.R Sheikholeslami
Abstract
The effects of the Mid-Cimmerian event in the BinaludMountains can be investigated in the Mashhad Phyllite around Mashhad and in the Aghdarband Group in the Aghdarband area. In the Eastern Binalud, this event acted in prehnite-pumpellyite to lower greenschist facies and influenced the Shemshak group, ...
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The effects of the Mid-Cimmerian event in the BinaludMountains can be investigated in the Mashhad Phyllite around Mashhad and in the Aghdarband Group in the Aghdarband area. In the Eastern Binalud, this event acted in prehnite-pumpellyite to lower greenschist facies and influenced the Shemshak group, which deposited as a post Early Cimmerian molasse blanket in a Rhaetian–Lias back-arc basin. The result is transformation of these sediments into the slate, phyllite and metasandstone. Tight to open folds, axial plane foliations and crenulation folds with NW-SE trending are the Mid-Cimmerian deformational structures. Due to the lower grade of metamorphism and deformation, there isn’t any important effect of this event on the rocks, which were previously deformed and metamorphosed by the Early Cimmerian event. The exhumation and erosion of deformed rocks by the Early and Mid-Cimmerian events generated the intramontane basins in the internal part of the eastern BinaludMountains. In the Aghdarband area, this event is characterized by folding of the Sina Formation from the Aghdarband Group, which is unconformably overlain by the Kashafroud Formation.
F. Dabbaghi Sadr; K. Seyed-Emami; M. Majidi Fard
Abstract
Upper Jurassic rocks are well developed at the western part of the Binalud Range (northeast Iran). These consist mainly of limestone, marlstone and marl with few intercalations of sandstone and conglomerate. The thickness of this succession in the study section (Bormahan, northwest of Neyshabour) ...
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Upper Jurassic rocks are well developed at the western part of the Binalud Range (northeast Iran). These consist mainly of limestone, marlstone and marl with few intercalations of sandstone and conglomerate. The thickness of this succession in the study section (Bormahan, northwest of Neyshabour) is 1084 meters and can be subdivided into 6 members. The lower boundary with the dark siliciclasts of ?Kashafrud Formation (Upper Bajocian / Lower4 Bathonian) is sharp. The upper boundary with buff and cliff-forming carbonates of the ?Mozduran Formation (Upper Jurassic) is transitional. Ammonites are the most important and abundant macrofossils.Totally more than 300 specimens have been collected, comprising 21 genera and 36 species.The relative abundances at the family level are: Phylloceratidae (48%), Perisphinctidae (42%), Oppeliidae (6%), Haploceratidae (2%), Aspidoceratidae (1%) Based on the ammonite fauna 15 biozones are recognized which can be fairly good compared with the ammonite biozonation of Sub-Mediterranean Province. According to the ammonite fauna an Early Bathonian to Kimmeridjian age is proposed.The ammonite fauna is closely related to those of the Sub-Mediterranean Province, indicading a permanent faunal exchange.
A. R. Ashouri; M. R. Majidifard; M. Vahidinia; A. Raoufian
Abstract
A thick succession of Middle – Late Jurassic rocks in the western part of BinaludRange has been studied. This succession consists mainly of limestone, marly limestone and marl. The thickness of the succession in the study section (Baghi, north of Neyshabour) is 709 meters and is subdivided into ...
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A thick succession of Middle – Late Jurassic rocks in the western part of BinaludRange has been studied. This succession consists mainly of limestone, marly limestone and marl. The thickness of the succession in the study section (Baghi, north of Neyshabour) is 709 meters and is subdivided into 4 members. The lower boundary with the underlying dark shale and upper boundary with the overlying buff limestone are inconspicuous and transitional. Ammonites are the most important and abundant macrofossils in this section. 43 genera and 76 species have been identified among them 8 species are reported for the first time from Iran. Based on the ammonite fauna, Early Bathonian to Kimmeridjian ages are purposed for these rocks. The fauna show close relationship to Sub- Mediterranean province and there is a great similarity between ammonite fauna of the investigated area with Kope – Dagh and AlborzRange.
