Sedimentology
Ali Hossein Jalilian; Mohammad Ali Kavoosi
Abstract
The Hauterivian-Barremian Gadvan Formation represents the depositional sequence in central and eastern regions of Zagros Mountains. Field and petrographic investigations of this formation in Khaneh-Kat anticline togheter with wireline logs and cuttings analysis of two drilled wells in the Dashtak and ...
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The Hauterivian-Barremian Gadvan Formation represents the depositional sequence in central and eastern regions of Zagros Mountains. Field and petrographic investigations of this formation in Khaneh-Kat anticline togheter with wireline logs and cuttings analysis of two drilled wells in the Dashtak and Bandubast gas fields (Interior Fars area) indicate important events in the basin evolution, especially the changes in the sedimentation regime and platform evolution during the time period. The key point is upward grading of the thick-bedded, feature forming Berriasian-Valanginian carbonates into shale, marl and argillaceous limestone interbeds of the Gadvan Formation. The vertical changes is consisten with a prominent decrease in carbonate production and a definite change in the nature of the Fars platform. The intense bioturbation and mostly mud-dominated texture of skeletal limestones indicate Gadvan Formation deposited in a mixed carbonate-siliciclastic platform. In the drilled wells, these changes correspond to a significant increase in gamma-ray and sonic wireline logs. The Khalij Member shows the regional continuity, indicates an increase of carbonate production in the mixed platform. Considering tectonic quiescence of Fars area during Early Cretaceous, the mentioned changes can be the result of interplay between tropical climate and short-term fluctuations in the context of global sea level rise.
Stratigraphy and Palaeontology
Abdolvahab Kazemi; Nasrollah Abbassi
Abstract
Agha Jari Formation (Miocene-Pliocene, 788 m) comprises alternations of sandstone, siltstone, and marl in red to brown color layers in the east Gotvand, north Khuzestan province, southwest Iran. Numerous vertebrate footprints have been found in the middle part of the Formation, which includes footprints ...
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Agha Jari Formation (Miocene-Pliocene, 788 m) comprises alternations of sandstone, siltstone, and marl in red to brown color layers in the east Gotvand, north Khuzestan province, southwest Iran. Numerous vertebrate footprints have been found in the middle part of the Formation, which includes footprints of wetland small bird (Aviadactyla media, Gruipeda dominguensis), artiodactyls (Lamaichnum alfi, Lamaichnum isp., Pecoripeda satyri, Pecoripeda isp.), canids (Canipeda isp.) and large reptiles (Hatcherichnus sanjuanensis). Frequency of artiodactyl imprints are more than the other footprints. These footprints proof the living of camels and crocodiles in the Zagros basin for the first time. The ichnotaxa diversity of the footprints in the studied section is more than the other reports of Agha Jari Formation in Iran and its stratigraphic equivalent in the adjacent countries.
Stratigraphy and Palaeontology
Saeedeh senemari; Narges Monjezi
Abstract
Pabdeh Formation to Asmari Formation transition deposits were studied in the stratigraphic section of Khaviz located in the northeast of Behbehan. In the present research, the deposits of the upper part of Pabdeh Formation consisting shale and interbedded of argillaceous gray limestone with a thickness ...
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Pabdeh Formation to Asmari Formation transition deposits were studied in the stratigraphic section of Khaviz located in the northeast of Behbehan. In the present research, the deposits of the upper part of Pabdeh Formation consisting shale and interbedded of argillaceous gray limestone with a thickness of about 66 m were studied, which are followed by deposits of the lower part of Asmari Formation with a thickness of about 21 m, including cream-colored clay limestone. As a result of this study, 33 species belonging to 15 genera of calcareous nannofossils were identified. Based on the recorded bio-events and associated fossil assemblages, the bio-zones of Sphenolithus pseudoradians Zone, Ericsonia subdisticha Zone, Helicosphaera eticulate Zone, Sphenolithus predistentus Zone, Sphenolithus distentus Zone were determined. The studied zones are consistent with CNE20- CNO4/ CNO5 from Agnini et al. (2014) zonation. Based on the introduced bio-zones, the age of the upper part of Pabdeh Formation in the studied section of the Priabonin-early Rupelian and the age of the lower part of the Asmari Formation Rupelian-Chattian are suggested. In this study, the boundary between Pabdeh and Asmari formations is continuous, which indicates sedimentation with decreasing depth in the boundary of these two formations.
Petrology
Ayoub Veisinia; Mohammad Ebrahimi; Bahman Rahibzadeh; rasoul Esmaeili
Abstract
Kamyaran ophiolitic complex located in the northeast Zagros orogeny along the crush zone between Arabian-Iranian plates. This complex outcropped between the Harsin ophiolites in southeast and Sarwabad ophiolite in northwest. Field observation reveal the fact that the Garmab Ophiolite in the northeast ...
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Kamyaran ophiolitic complex located in the northeast Zagros orogeny along the crush zone between Arabian-Iranian plates. This complex outcropped between the Harsin ophiolites in southeast and Sarwabad ophiolite in northwest. Field observation reveal the fact that the Garmab Ophiolite in the northeast of Kamyaran is a tectonic mélange including peridotites and gabbros cut by microgabbroic dikes. Olivine, clinopyroxene and orthopyroxene with chromian spinel made the peridotites minerals with mesh and porphyroclastic fabrics and Gabbros include plagioclase, clinopyroxene and minor amphibole with intergranular, pegmatoidic and interstitial texture. According to the geochemical results, gabbros have tholeiitic to calk-alkaline nature and show the MORB to island arc characteristics. According to the geochemical and geotectonic results, Garmab peridotites plotted to the abyssal peridotites area that represent from the residual mantle spinel lherzolite after extraction of 15–20% partial melting. The break-off of Neo-Tethyan slab and subduction of this slab branch beneath the oceanic lithosphere during cretaceous led to cessation of the Neo-Tethyan subduction beneath the Sanandaj-Sirjan block, and forming arc-back arc basin (second step of subduction) and related rocks in the Kamyaran ophiolite. Presence of tholeiitic to calc-alkaline magmatism is in response to the slab retreat in the Eurasian continental margin.
Stratigraphy and Palaeontology
Arash shabanpour Haghighie; Lida Bakhshandeh; Tayebeh Mohtat; Masood Zamanipedram; Seyed hamid Vaziri
Abstract
In this research the Gurpi Formation in the Zagros Basin outcropping in the Dasht-e Arjan section, Shiraz province ,for the purpose of biozonational and Paleobathymetric studies were investigated. The thickness of these sediments is about 130 m and consists of Limestones and Shales.To determine the palaeobathymetry ...
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In this research the Gurpi Formation in the Zagros Basin outcropping in the Dasht-e Arjan section, Shiraz province ,for the purpose of biozonational and Paleobathymetric studies were investigated. The thickness of these sediments is about 130 m and consists of Limestones and Shales.To determine the palaeobathymetry of the Gurpi Formation, Planktonic and benthic foraminifera were investigated . A depth of about 270m to 510m was determined for these sediments based on the ratio of planktonic foraminifera to the total assemblages of foraminifera after omitting infaunal benthic foraminifera (%P*) by using the equation D = e (3.58718+(0.03534 × %P* )).In this study sixty-two species of planktonic foraminifera belonging to eighteen genera were recognised .According to the studied planktonic foraminifera the Upper Cretaceous deposits in this area were divided into nine biozones as following :biozone1- Dicarinella concavata Interval Zone. Biozone2- Dicarinella asymetrica Total Range Zone. Biozone3- Globotruncanita elevata Partial range zone .Biozone4- Globotruncana ventricosa Interval Zone. Biozone5- Radotruncana calcarata Interval zone. Biozone 6- Globotruncanella havanensis Partial Range Zone. Biozone7- Globotruncana aegyptiaca Interval Zone. Biozone 8- Gansserina gansseri Interval Zone. Biozone 9- Contusotruncana contusa Interval ZoneBased on the studied planktonic foraminifera the Early Santonian to Maastrichtian ages were determined for the sediments .
Petrology
Azad karimi; ali ahmadi; Monireh Kheirkhah; Abdolreza Partabian
Abstract
The peridotites from Marivan-Kamyaran ophiolite suite (MKO), outer Zagros ophiolite belt, western Iran, are studied for the petrological and geochemical characteristics. Both mantle and crustal peridotites are present in the Marivan-Kamyaran ophiolitic sequence. Extensive compositional variations in ...
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The peridotites from Marivan-Kamyaran ophiolite suite (MKO), outer Zagros ophiolite belt, western Iran, are studied for the petrological and geochemical characteristics. Both mantle and crustal peridotites are present in the Marivan-Kamyaran ophiolitic sequence. Extensive compositional variations in MgO, Al2O3, Cr, Ni and Al2O3 / SiO2, combined with the abyssal (MOR) and supra-subduction zone (SSZ) nature of the peridotites, are indicative of variant degrees of depletion of the mantle peridotites. Various degrees of depletion are consistent with a wide range of partial melting percentages (10-15%) obtained from non-modal backward partial melting models. The enrichment in HFSE such as Hf, Ti, Ta and Th indicates melt-rock interaction in the mantle peridotites; while, the enrichment in U and LIL elements such as Cs, Rb, Pb is most probably related to the fluid-rock interaction. It is suggested here that MOR nature of a part of the mantle peridotites in the region has been changed to SSZ characteristics in later stages through processes such as melt-rock interaction. It is likely that, similar to other occurrences of outer Zagros ophiolite belt, mantle peridotites from MKO with MOR and SSZ characteristics had been originated in MOR setting, before their composition were modified in a SSZ environment.
Sedimentology
Ali Hossein Jalilian
Abstract
The Mesozoic sequence in the Zagros Region (SW Iran) consists dominantly of carbonates especially dolomite that play the role of reservoir in many oil and gas fields of the region. To investigate the function of sedimentary and diagenetic processes in the formation of Triassic-Neocomian dolomites of ...
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The Mesozoic sequence in the Zagros Region (SW Iran) consists dominantly of carbonates especially dolomite that play the role of reservoir in many oil and gas fields of the region. To investigate the function of sedimentary and diagenetic processes in the formation of Triassic-Neocomian dolomites of the easthern High Zagros, this study focuses on petrography and geochemistry of the carbonates crop out in the Khaneh Kat anticline. Field and laboratory data led to the recognition of four different dolomitization models within the studied carbonates. The Lower-Middle Triassic and Upper Jurassic dolomites are medium to thick-bedded and composed of fine to medium-grained relatively ordered dolomite. The stoichiometric chemistries and heavier oxygen isotope ratios of these dolomites as well as the considerable presence of evaporites indicate the favorable conditions for the formation of early dolomite due to downward-percolating of concentrated evaporate brines (reflux model). The Upper Triassic dolomitic portion of the Zagros consists of medium to coarse-crystalline, massive-bedded dolomites with relatively light isotopic composition. Mineralogy and geochemistry of these dolomites indicate a high temperature origin as well as their relationship to diagenetic processes, including recrystallization in a deep-subsurface environment (burial model). In the Upper Jurassic portion of the succession, dolomites are ...
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
Mehdi Tavakoli Yaraki; Seyyed Ahmad Alavi; Mohammad Reza Ghassemi; Iraj Abdollahie fard
Abstract
The significance of mechanical stratigraphy of rocks in kinematics of folds has long been of interest to structural geologists. Parameters such as sedimentary facies variations and thickness of incompetent layers play major role in activity of these layers as detachment horizons. The purpose of this ...
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The significance of mechanical stratigraphy of rocks in kinematics of folds has long been of interest to structural geologists. Parameters such as sedimentary facies variations and thickness of incompetent layers play major role in activity of these layers as detachment horizons. The purpose of this study is to investigate the role of mechanical stratigraphy on fold geometry in the Aghajari and Pazanan anticlines within the Dezful Embayment zone. For this purpose, we have used seismic profiles, stratigraphic data and petrophysical logs as well as the previous stratigraphic works in study area. Results show that the Garau Formation is the major intermediate detachment level in the Aghajari structure, and has a significant control on folding geometry of the competent sequences of the Fahliyan to Asmari Formations. The Dashtak Formation and other incompetent evaporatic Formations of Middle-Upper Jurassic also have been active in the Aghajari structure. In contrast, in most parts of the Pazanan structure, the Garau and the Jurassic Formations do not have appropriate mechanical properties to act as intermediate detachment levels due to their change into hemipelagic facies and limestone (Surmeh Formation) respectively. Based on the evidences, the facies change in the abovementioned Formations occurs between the Pazanan and Aghajari anticlines. It seems that activity of the Hendijan-Izeh paleo-high also has some control on facies of the Garau Formation. Based on geometric characteristics and a geometric conceptual model provided for development of these structures, the folding style of the anticlines is suggested as an asymmetric faulted detachment fold type.
Stratigraphy and Palaeontology
faeze Amiri; E Zarei
Abstract
The Gurpi formation in Bishe-deraz Section, south of Ilam, consists of 201m marl with intercalations of limy marl with two formal members of Seymareh (Lopha) and Emam-Hasan. The formation overlies the Ilam Formation and is gradationally overlain by the purple shales of the basal part of the Pabdeh Formation. ...
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The Gurpi formation in Bishe-deraz Section, south of Ilam, consists of 201m marl with intercalations of limy marl with two formal members of Seymareh (Lopha) and Emam-Hasan. The formation overlies the Ilam Formation and is gradationally overlain by the purple shales of the basal part of the Pabdeh Formation. The Gurpi Formation was divided to 9 biozone on the basis of planktonic foraminifera which almost are cosmopolitan and consist of: 1- Radotruncana calcarata Taxon-Range Zone. 2- Globotruncanita stuartiformis Partial-Range Zone. 3- Globotruncana aegyptiaca Interval Zone. 4-Gansserina gansseri Interval Zone. 5- Contusotruncana contusa Interval Zone. 6- Abathomphalus mayaroensis Interval Zone. 7- Praemurica uncinata Interval Zone. 8- Morozovella angulata Interval Zone. 9- Globanomalina pseudomenardii Interval Zone. The formation was deposited from upper Campanian through late Paleocene (Selandian-Thanetian?) according to the planktonic foraminifera recorded. A distinct hiatus was confirmed at the Cretaceous-Paleogene boundary according to microbiostratigraphic and sedimentologic studies and also field work observation.
Geophysics
Mohammadreza Jamalreyhani; Abdolreza Ghods; Seyyed Khalil Mottaghi; Esmail Shabanian; Morteza Talebian; Beijing Chen
Abstract
One of the main issues in Zagros is the extent that basement and the thick sedimentary layer participate in the observed seismicity. During Nov. 2013, five magnitude ~5 Mw events hit a region in the western end of Lurestan arc of Simply Folded Belt (SFB) of Zagros. We used the Iran-China temporary network ...
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One of the main issues in Zagros is the extent that basement and the thick sedimentary layer participate in the observed seismicity. During Nov. 2013, five magnitude ~5 Mw events hit a region in the western end of Lurestan arc of Simply Folded Belt (SFB) of Zagros. We used the Iran-China temporary network and data from regional permanent networks to relocate the events using a multiple event relocation method, calculate regional moment tensor and centeriod depths for the five moderate events and estimate a velocity model for the two nearby seismic stations using joint inversion of the receiver functions and dispersion curves. Our results show a seismic cluster of about 30 km long and 15 km width. The moment tensor solutions of the five moderate events indicate an almost pure thrust mechanism. The aftershock cloud indicate a low angle east dipping fault plane (i.e., , dip in the range of 23 o -39 o ) as the causative fault plane. The calculated centeroid of the five moderate events are about 14 km and the focal depth of all events calculated by multiple event relocation are about 10-16 km. The results indicate that the thickness of sedimentary column is less than 8 km and thus showing the whole seismic cluster happened within the basement. This observation proves wrong the hypothesis of vertical separation of mainshock and aftershocks in Ssimply folded belt FB of Zagros (Nissen et al. 2011) and implies that in the Lurestan arc the sedimentary layers are deformed aseismically.
Stratigraphy and Palaeontology
kiana kiarostami; Darioush Baghbani; Seyed Mohsen Aleali; Seyed Ali Aghanabati; Mohammad Parandavar
Abstract
Lithostratigraphy and biostratigraphy studies on the Sarvak Formation in type section (Tang- e Sarvak, Northwest of Behbahan) show that this Formation has 710 meter thicknesses that divided in to four lithostratigraphic units. The Sarvak Formation in type section rests on the Kazhdumi Formation conformably ...
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Lithostratigraphy and biostratigraphy studies on the Sarvak Formation in type section (Tang- e Sarvak, Northwest of Behbahan) show that this Formation has 710 meter thicknesses that divided in to four lithostratigraphic units. The Sarvak Formation in type section rests on the Kazhdumi Formation conformably with gradational contact (black shales and black argillaceous limestone) and under the Gurpi Formation with disconformity boundary. In this study 8 genus and 9 species of planktonic foraminifera and 34 genera and 33 species of benthic foraminifera have been reported. Four biozones based on (wynd, 1965) and two biozone based on) Premoli Silva and Verga 2004) have been reported as follow; Four biozones based on Wynd 1965: 1- Favusella washitensis range Zone # 23,2- '' Oligostegina'' facies # 26,3- Rudist debris # 24, 4- Nezzazata– Alveolinids Assemblage Zone # 25, Tow biozones based on Premoli Silva and Verga 2004: 1-Muricohedbergella planispira Zone, 2-Ticinella primula Zone. It can propose an Albian- Cenomanian age for Sarvak Formation based on these biozones and also it can recognize Albian-Cenomanian boundary on occurrence of Muricohedbergella planispira and Whiteinella sp. in lower part of this Formation.
Stratigraphy and Palaeontology
s senemari
Abstract
In order to study biostratigraphy of the Pabdeh Formation in the Northeast Kazerun, Murdak section was selected. In this section, Pabdeh Formation is mainly consists of marl, shale and marly limestone. The study of calcareous nannofossils led to the recognition of 70 species and 28 genera. According ...
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In order to study biostratigraphy of the Pabdeh Formation in the Northeast Kazerun, Murdak section was selected. In this section, Pabdeh Formation is mainly consists of marl, shale and marly limestone. The study of calcareous nannofossils led to the recognition of 70 species and 28 genera. According to the first and last occurrence of index species and assemblages fossil, the following biozones based on global standard zonations are identified: Discoaster multiradiatus Zone (NP9/CP8a/CNP11), Tribrachiatus contortus Zone (NP10/ CP8b-CP9a/ CNE1- CNE2), Discoaster binodosus Zone (NP11/ CP9b/ CNE3), Tribrachiatus orthostylus Zone (NP12/ CP10/ CNE4), Discoaster lodoensis Zone (NP13/ CP11/ CNE5), Discoaster sunlodoensis Zone (NP14/ CP12/ CNE6- CNE8), Nannotetrina fulgens zone (NP15/ CP13/ CNE9-CNE11), Discoaster tanii nodifer Zone (NP16/ CP14a/ CNE12-CNE15), Discoaster saipanensis Zone (NP17/ CP14b/ CNE15- CNE16), Chiasmolithus oamaruensis Zone (NP18/CP15a/CNE17-CNE18), Isthmolithus recurvus Zone (NP19/CP15b/CNE18-CNE19), Sphenolithus pseudoradians Zone (NP20/ CP15b/ CNE20), Ericsonia Subdisticha zone (NP21/CP16a-b/CNE21-CNO1), Helicosphaera reticulate Zone (NP22/ CP16c/ CNO2), Sphenolithus predistintus Zone (NP23/ CP17- CP18 / CNO3- CNO4). As a result of this study and based on the obtained biozones, the age of Pabdeh Formation in Murdak section, is Late Paleocene (Thanetian) to Oligocene (Rupelian-Chatian).
Stratigraphy and Palaeontology
Zahra Hosseini Asgarabadi; Nasrollah Abbassi; Hassan Mohseni; Saeed Khodabakhsh
Abstract
The Pabdeh Formation (Paleocene to Oligocene in age) comprises alternation of marl and limestone with the Purple Shale at the base is well exposed on the flanks of the Kabir-Kuh. Thalassinoides, Rhizocorallium, Planolites, Chondrites, cf. Rosselia, Spirophyton and Zoophycos were found in the limestone ...
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The Pabdeh Formation (Paleocene to Oligocene in age) comprises alternation of marl and limestone with the Purple Shale at the base is well exposed on the flanks of the Kabir-Kuh. Thalassinoides, Rhizocorallium, Planolites, Chondrites, cf. Rosselia, Spirophyton and Zoophycos were found in the limestone beds, among which trace fossils of Zoophycos group (Spirophyton and Zoophycos) are the most abundant. Structural variations of trace fossils of Zoophycos group were utiliized for recognition of five morphotypes including Rhizocorallium-shaped, branched Zoophycos, Spirophyton, short and fan-shaped lobate Zoophycos and long lobate Zoophycos morphotypes. Occurrence of these morphotypes in the studied sections implies an evolutionary trend, i.e. Rhizocorallium-shaped and branched Zoophycos morphotypes are developed in the lower parts of studied sections, whereas Spirophyton morphotype, is arranged in the mid-part of the Pabdeh Formation. Finally, short and fan-shaped lobate and long lobate Zoophycos morphotypes are abundant in the upper part of the formation. Seemingly, these morphotypes variation were adopted with switch of stable and calm water to unstable and relatively high energy environments.
H. Kianimehr; F. Yaminifard; M. Tatar; E. Kissling
Abstract
The Zagros fold and thrust belt contains a near continuous sedimentary cover which overlies the late Precambrian-Cambrian Hormuz salt formation. The information about this structure is only limited to the study of salt domes. As the density variation of salt is not noticeable with depth, it is expected ...
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The Zagros fold and thrust belt contains a near continuous sedimentary cover which overlies the late Precambrian-Cambrian Hormuz salt formation. The information about this structure is only limited to the study of salt domes. As the density variation of salt is not noticeable with depth, it is expected this structure has a significant role in the decrement of P-wave velocity relative to top layers. The 9 April, 2013 Kaki earthquake (MW 6.2), occurred in a part of the Simply Folded Belt of Zagros Mountains where there are two salt domes. So, in case of studying salt structures as low velocity zones at depth, the 1-D inversion was done using 10459 P-arrival times of 978 aftershocks. The results of this study indicate that the two top layers with overall 4km thickness and average low velocities might be related to incompetent and upper-mobile groups. Sudden seismic velocity increment from 3.9 km/s to 5.45 km/s in depth of 4 km can be considered as an indicator for transformation from the upper-mobile to the competent group. Furthermore, an average low velocity zone from 8 km to 12 km is observed that confirms the Hormuz salt series at depth.
P. Rajabi
Abstract
Taleh Zang Formation is shallow carbonate facies of the Paleogene Zagros Basin. According to the area, including depth, tectonic and sedimentary sedimentation rate and other factors of the formation with Kashkan and Shahbazan sometimes with different thicknesses of semi-deep and deep Papdeh facies were ...
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Taleh Zang Formation is shallow carbonate facies of the Paleogene Zagros Basin. According to the area, including depth, tectonic and sedimentary sedimentation rate and other factors of the formation with Kashkan and Shahbazan sometimes with different thicknesses of semi-deep and deep Papdeh facies were deposited locally. According to the study Taleh Zang Formation calcareous stratigraphic section thickness of 185 meters (true thickness) were measured from 15 genera and 10 species of 110 sample benthic foraminifera identified by study and introduced 3 biozones 2 Assemblage zone and a Acrozon, late Paleocene (thanetian) and lower Eocene (ypresian) is intended for the stratigraphic section.
Geophysics
Mohammad Reza Ebrahimi; Mohammad Tatar
Abstract
Impoundment of a reservoir and changes in the lake levels can trigger / induce the seismicity. In this research, the strength changes are modeled across the Golestan fault, due to loading effect of Gotvand-e Olya reservoir which is located in the Zagros Mountain of SW Iran. The formulas based on 3D Boussinesq ...
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Impoundment of a reservoir and changes in the lake levels can trigger / induce the seismicity. In this research, the strength changes are modeled across the Golestan fault, due to loading effect of Gotvand-e Olya reservoir which is located in the Zagros Mountain of SW Iran. The formulas based on 3D Boussinesq solutions were used to calculate normal and shear stresses on a given fault plane. Geometry and mechanism of the Golestan fault were precisely determined using local earthquakes recorded by a local seismological network. For a better analysis, we did the calculations in three different dips of 55, 60 and 65 degrees for the Golestan fault. Since the lake is located on the hanging wall of the Golestan fault, it is expected that loading effect of the reservoir causes delay on occurrence of earthquakes and make the fault more stable. Analysis of induced stresses confirms this too, the results in all dips in most parts of the fault from 7 km to 20 km depth, which are in closer distance to the reservoir, indicate on stabilization. Only in a small part of the fault, located at shallow depths between 5 and 7 km, the destabilizing effect is observed. The calculated strengths, which leads to destabilizing the Golestan fault ranges between -0.243 bars and 0. The observed seismicity in vicinity of the Golestan fault for before and after the impoundment confirms the the results of stress modelling in different parts of the fault.
A. Zohdi; S. A. Moallemi; M. A. Salehi
Abstract
In the Zagros sedimentary basin, the maximum thickness of the Guri Member carbonates is belonging to the eastern parts of the Bandar-Abbas region. In this research, the Guri Member in five outcrops at the Bandar-Abbas region has been sedimentological and stratigraphic studied. The Guri Member mainly ...
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In the Zagros sedimentary basin, the maximum thickness of the Guri Member carbonates is belonging to the eastern parts of the Bandar-Abbas region. In this research, the Guri Member in five outcrops at the Bandar-Abbas region has been sedimentological and stratigraphic studied. The Guri Member mainly consists of limestone with interbedded marl with a variable thickness from 540 m at the Handun outcrop to 52 m at the Nakh outcrop. According to facies study and using the 87Sr/86 Sr isotopic ratio (amounts 0.708522 and 0.708790 values) of the basal carbonate layers of this member, the beginning sedimentation of these deposits occur during the Burdigalian and Langian times within the five carbonate facies. Fieldwork observations and facies distribution suggested a shelf carbonate platform for deposition of the Guri Member at the Bandar-Abbas region. Petrographic investigation in addition to trace elements (Sr, Mn and Fe) and isotopic (oxygen and carbon) geochemical analyses, also indicate the main influence of the marine to shallow-burial diagenetic process with the marine fluids after primary deposition of the Guri Member. The comparison of the oxygen and carbon isotope values of the Guri samples with the least-altered oxygen and carbon range for the early to middle Miocene marine calcite and also the more variations of the oxygen isotope values (between -1.19‰ to -5.39‰ PDB), and lees variations of carbon isotope values (between -1.05‰ to 2.2‰ PDB), indicate the effects of shallow-burial fluids (marine-phreatic) on the carbonate of the Guri Member.
P Gholami Zadeh; M.H Adabi; M Hosseini-Barzi; A Sadeghi; M.R Ghassemi
Abstract
The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two ...
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The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two sections are 424 and 440 m respectively and contain red and green sandstone, conglomerate and marl which are bounded unconformably between the Jahrum Formation and Bakhtiari conglomerate. Based on the field and petrographic studies, 14 sedimentary facies related to proximal, mid fan-delta; transition zone, delta slope and prodelta have been recognized for the Miocene succession. Due to the slope facies formed by the turbidity currents, grain fall and debris flows, the coarse grained clasts and poorly sorted texture, a fan-delta model is suggested for the succession. Also, the development of the slope facies indicates a paleo-slope and slope-type, deep-water fan-delta. The frequent intra-formational disconformities, irregular changes in grain size and present of gravity flows indicate an active tectonic sedimentary basin and reflux of coarse grained sediments (catastrophic events) to the proximal parts of Zagros Basin.
P Gholami Zadeh; M.H Adabi; M Hosseini-Barzi; A Sadeghi; M.R Ghassemi
Abstract
Petrography and geochemistry of the Neyriz Miocene sediments at RoshanKuh and Kuh-e Asaki sections were carried out to determine their provenance, tectonic setting and paleoclimate conditions in the proximal part of Zagros Basin. The Miocene sediments are limited to the Zagros Main Fault at the northeast ...
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Petrography and geochemistry of the Neyriz Miocene sediments at RoshanKuh and Kuh-e Asaki sections were carried out to determine their provenance, tectonic setting and paleoclimate conditions in the proximal part of Zagros Basin. The Miocene sediments are limited to the Zagros Main Fault at the northeast and the Neyrizophiolite zone at the southwest in the Neyriz region. They contain about 700 m red and green sandstone, conglomerate and marl which overlay the Jahrum Formation with a disconformity and covered by Bakhtiari conglomerate with an angular unconformity.Petrography of thin sections indicates that the rock fragments are the most constituent, and then quartz and feldspar respectively. The low compositional and textural maturity of the studied samples (angular grains and poorly sorted sandstones) shows the proximity to the source area. Petrography of the rock fragments and the bulk chemical composition of samples display that their provenance is multiple and the sediments were derived from Sanandaj-Sirjan Zone (Cretaceous limestone- metamorphic rocks- Eocene volcanic) and Zagros Zone (ophiolite sequence- radiolarites- Eocene limestone). Also, point-count data plotted on the QFL and QmFLt triangles indicate the recycled orogen and magmatic arc provenance. Based on geochemical data tectonic setting of Neyriz Miocene sediments is continental island arc and active continental margin. The averages of Cullers' index, CIW΄ (for calculation of the chemical weathering), ICV Index (to determine the maturity source), and SiO2versus Al2O3 + K2O + Na2O diagram for these sediments show a poor weathering and dry climatic condition during their deposition which is supported by the high percentage of calcareous cement and frequency of the rock fragments. The results of this study suggest a sedimentlogical framework for the proximal part of Zagros Basin and the Miocene syn-depositional processes.
M Hamidian Shirazi; A Saeedi; A Solgi; K Yazdjerdi
Abstract
The Zagros orogen is located along the central part of the of Alpine-Himalayan orogenic belt, and is one of the world’s youngest orogenic systems. Geological and deformational characteristics of this orogen are completely different from other parts of the Alpine orogenic belt. Of the most obvious ...
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The Zagros orogen is located along the central part of the of Alpine-Himalayan orogenic belt, and is one of the world’s youngest orogenic systems. Geological and deformational characteristics of this orogen are completely different from other parts of the Alpine orogenic belt. Of the most obvious structural features of the Zagros orogen are the occurrence of large-scale folds. The lack of geometrical uniformity along their axes is the most important character of these folds. General trend of the structures formed in the Zagros region (folds and major faults) is northwest–southeast, which is locally deflected due to different reasons such as effects of large fault zones. In some places, the changes in the initial pattern of folds may be related to more than one tectonic parameter. The simultaneous operation of two or more parameters such as faulting or salt penetration can also significantly change the fold patterns. The Ahmadi anticline, which is located 50 km east of Shiraz, is one of such folds where this property (i.e. changes in fold pattern) can be investigated. The fold has a box fold model with the axis trending NNW-SSE, and is located south of the Main Zagros Thrust Fault, as well as close and parallel to it. It is also situated in the Zagros folded zone and forms the northern boundary of the Sarvestan plain. The Ahmadi anticline is an open and symmetric fold, trending along NNW-SSE direction. Along the anticline, the fold axis is never straight and has been deflected at several points. The most significant fold axis deflection is observed along the eastern termination of the anticline, where the fold axis is deflected by about 62 degrees toward south.
Z Mohammadipour; F Yaminifard; M Tatar
Abstract
Nearly one-third of the shortening in Iran plateau due to Arabia-Eurasia convergence is accommodated in the Zagros fold and thrust belt, which is seismically one of the most active regions among the continental collision zones in the world. Deploying a temporary seismic network in the north of Bandar ...
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Nearly one-third of the shortening in Iran plateau due to Arabia-Eurasia convergence is accommodated in the Zagros fold and thrust belt, which is seismically one of the most active regions among the continental collision zones in the world. Deploying a temporary seismic network in the north of Bandar Abbas in Hormozgan Province, which consisted of 32 three-component seismograph stations operating for a duration of about 3.5 months, provided appropriate data for studying the upper crustal structure of the easternmost Zagros by usingLocal Earthquake Tomography. Three dimensional velocity model obtained from the conversion of P-wave arrival times indicates southwestward overthrusting of the lower crust of northern parts, supporting active underthrusting of the Arabian plate beneath Central Iran in the easternmost Zagros. A very low velocity zone is also observed in the eastern part of the study area that could be associated with the Zendan-Minab-Palami fault system.
M Mohammadi; H Amiri Bakhtiar; F Amraee
Abstract
This study aimed to compare Asmari Formation in two sections in Maleh-Kuh and Amiran anticlines based on benthonic foraminifera. In this study, 26 species and 16 genera of benthonic foraminifera from the Maleh-Kuh section yielded 2 biozones of Elphidiumsp. 14 – Peneroplis, farsenensisandBorelismelocurdica ...
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This study aimed to compare Asmari Formation in two sections in Maleh-Kuh and Amiran anticlines based on benthonic foraminifera. In this study, 26 species and 16 genera of benthonic foraminifera from the Maleh-Kuh section yielded 2 biozones of Elphidiumsp. 14 – Peneroplis, farsenensisandBorelismelocurdica – Borelismelomeloweresuggesting an age of Aquitanian – Burdigalian for the formation. In Amiran anticline based on 27 species and 20 genera only the biozone of Borelismelocurdica – Borelismelomelo (Burdigalian)was recorded.Based on this study, the Asmari sequence in Maleh-kuh Section (with a thicknessof 310m) deposited earlier In Aquitanian. But in Amiran section (with a thickness 162m) deposition started in Burdigalian and ended synchronously in both sections. In both sections the Asmari Formation overlain Shahbazan Formation disconformably and is in turn under lain by Ghachsaran Formation concordantly-transitionally in Maleh-Kuh and by a sharp contact in Amiran Section.
A Asadi; M.R Majidi fard; S.H Vazirii; M Yousefi rad
Abstract
Considering importance of ammonite fauna in biostratigraphy and sedimentary basins and due to the lack of studies on the ammonite fauna in the Kazhdumi Formation, the Nar stratigraphic section was selected and studied in the coastal Fars, northeast of Kangan (East Bushehr). The formation with a ...
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Considering importance of ammonite fauna in biostratigraphy and sedimentary basins and due to the lack of studies on the ammonite fauna in the Kazhdumi Formation, the Nar stratigraphic section was selected and studied in the coastal Fars, northeast of Kangan (East Bushehr). The formation with a thickness of 87 meters in the studied section contains alternation of cream to brown limestone and brownish red marl. The lower boundary with the carbonate of the underlying Dariyan Formation is unconformable and in the upper boundary is gradually covered by the Madoud Member of Sarvak Formation. In the present study, 110 ammonites have been collected which are belong to three genera and seven species. These include Knemiceras sp., Knemiceras persicum, Knemiceras dubertreti, Knemiceras syriacum, Knemiceras comperessum, Tegoceras camatteanum and Lyelliceras lyelli. Based on these one subzone was differentiated indicating a late Early to Middle Albian age for the formation.
A Shamszadeh; S.A Alavi; M Valinejad; M Tavakoli Yaraki
Abstract
Babahabib and Sarkan oilfields are located in southwest of the Lurestan Province and 10km west of Pul-dokhtar City. The study area is situated in the Lurestan tectonostratigraphic region, northwest of the folded Zagros structural sub-zone. Although the Lurestan region is part of the Zagros sedimentary ...
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Babahabib and Sarkan oilfields are located in southwest of the Lurestan Province and 10km west of Pul-dokhtar City. The study area is situated in the Lurestan tectonostratigraphic region, northwest of the folded Zagros structural sub-zone. Although the Lurestan region is part of the Zagros sedimentary basin, it shows essential differences in terms of sedimentary conditions and types, folding and thickness of strata sequences when compared with the Dezful and Fars basins. Information obtained from seismic profiles, well logs and four cross-sections (AA´ to DD´) drawn perpendicular to structural trend indicates the effect of the detachment surfaces on structural geometry of folds in study area. Of the most important dataset used in this study are 2D and 3D seismic lines along with well logs, which were used in geometrical analysis of sub-surface structures. According to surface and subsurface structural geometries of fold in central part of the Lurestan region, two detachment surfaces including (1) Garu Formation as the middle detachment surface and (2) Amiran Formation as the upper detachment surface are interpreted to have affected subsurface anticlines (Bangestan group) and small surficial anticlines, respectively. The thickening of the upper detachment surface in western part of the study area has resulted in the development of folds with short wavelength and amplitude in outcrops. This thickness change causes disharmonic folding in surficial anticlines relative to the subsurface anticlines. The geometry of the Sarkan and Baba-Habib anticlines is represented as asymmetric detachment fold in which the increased stress in middle parts of the anticlines plus back-thrust structures have developed a geometry resembling Mitras’s (2002) model-1 faulted detachment fold. This model is formed by the high competency contrast between the Garu shaly units at the base and the overlying competent formations of the Bangestan group. Relay geometry of thrusts, which have been initiated from incompetent lower units, is one of the most important factors in controlling the en-echelon arrays of sub-surface anticlines in the area. Surficial geometries of the anticlines have been controlled by the upper detachment surface.
