Geological Environment and Engineering
Amir Mahyar Azhdarpour; Mohammad Reza Nikudel; Mashalah Khamehchiyan
Abstract
The central Alborz structural-sedimentary area in the middle part of the Alborz Mountain Range has endured geological events from the Precambrian to the present era, and contains numerous geological structures and formations. Among these, sandstone formations also have a significant expansion. In this ...
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The central Alborz structural-sedimentary area in the middle part of the Alborz Mountain Range has endured geological events from the Precambrian to the present era, and contains numerous geological structures and formations. Among these, sandstone formations also have a significant expansion. In this research, 6 different sandstone formations were sampled in 2 locations and tested to determine their physical and mechanical characteristics. In general, in the sandstone formations of central Alborz, top quartzite has stronger mechanical parameters than other formations. Shemshak Formation has the lowest mechanical parameters among the selected formations. Based on regression analysis, the conversion factor of PLT, BST and CPI parameters to unconfined resistance or UCS showed 20.6, 6 and 20.40 respectively with R2s of 0.75, 0.90 and 0.78. In terms of the Cerchar Abrasivity Index (CAI) as an index that can show the amount of abrasion, top quartzite has the most abrasiveness, which is due to its lithological composition. This sandstone formation is placed in the category of stones with high abrasive ability, and Shemshak Formation has the lowest Cerchar index among the formations and is placed in the group of stones with extremely low abrasiveness.
Stratigraphy and Palaeontology
Fereshteh Sajjadi; Firoozeh Hashemi Yazdi; Hossein Hashemi
Abstract
Reasonably diverse and very well-preserved palynomorphs including miospores, dinoflagellate cysts, foraminiferal test linings, acritarchs (sensu lato) and fungal spores occur in the Dalichai Formation, Yonjehzar, northeastern Tehran, central Alborz. The assemblages embrace 40 species of spores (assigned ...
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Reasonably diverse and very well-preserved palynomorphs including miospores, dinoflagellate cysts, foraminiferal test linings, acritarchs (sensu lato) and fungal spores occur in the Dalichai Formation, Yonjehzar, northeastern Tehran, central Alborz. The assemblages embrace 40 species of spores (assigned to 29 genera), 18 species of pollen (distributed among 10 genera) and 54 species of dinoflagellates (assigned to 28 genera). According to the presence of such miospores species with known worldwide stratigraphic distribution as Klukisporites variegatus, K. scaberis, Concavissimisporites verrucosus, C. pricei, Osmundacidites senectus and Striatella spp. the host strata are conceivably dated as Middle Jurassic. Based on the stratigraphic distribution of miospores, Klukisporites variegatus-Araucariacites australis-Cerebropollenites macroverrucosus Assemblage Zone is recognized. Presence of some index dinoflagellate species led to identification of four biozones in the Dalichai Formation. These include in ascending order, Cribroperidinium crispum Total Range Biozone (late Bajocian), Dichadogonyaulax sellwoodii Interval Biozone (Bathonian - early Callovian), Ctenididinium continuum Interval Biozone (early - middle Callovian) and Subzone a (early - middle Bathonian). Co-ccurrence of dinoflagellate cysts with known vertical ranges, viz., Cribroperidinium crispum, Meiourogonyaulax valensii, Carpatodinium predae, Ctenidodinium combazii and Compositosphaeridium polonicum suggests a Middle Jurassic age (late Bajocian to middle Callovian) for the host strata corroborates the available miospores-based biostratigraphy. The miospores are attributed to the Pterophyta (69%), Coniferophyta (15%), Pteridospermophyta (7%), Cycadophyta (5%), Lycophyta (2%), Ginkgophyta and Bryophytes (1%). Considering the relative abundance of fern spores (69%) and their morphological diversity (19 genera), it can be concluded that fern and fern-allies dominated the coastal vegetation around the sedimentary environments of the studied strata and that they flourished under a warm climate with notable humidity. The study of paleoclimate using the Sporomorph EcoGroups model shows a high ratio of warmer/cooler sporomorphs and a low ratio of drier/wetter sporomorphs, which is another confirmation of this type of climate. Presece of such warm water dinoflagellate cysts as Gonyaulacysta centriconnata, G. jurassica, Nannoceratopsis pellucida, Tubotuberella apatela, Ctenidodinium continuum, Pareodinia halosa, P. ceratophora, paleogeographic reconstruction and geographical location of Iran in the Middle Jurassic supports the generalization proposed.
Petrology
Saeid Samarbakhsh; Mohammad Hashem Emami; Seyed Mojtaba Mortazavi; Mansour Vosoughi-Abedini
Abstract
The study area, situated 50 km north of Ghaemshahr, structurally belongs to the Central Alborz tectonic zone. The volcanic rocks of the area, including basalt, andesite, trachyandesite, and dolerite are the products of fractional crystallization and some contamination processes. Clinopyroxene, olivine, ...
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The study area, situated 50 km north of Ghaemshahr, structurally belongs to the Central Alborz tectonic zone. The volcanic rocks of the area, including basalt, andesite, trachyandesite, and dolerite are the products of fractional crystallization and some contamination processes. Clinopyroxene, olivine, and plagioclase are the main minerals of these rocks. Porphyritic to mega-porphyritic texture with microlithic, glomeroporphyritic, and amygdaloidal matrix are observed in these rocks. Plagioclase, hornblende, and pyroxene can be considered the main mineral phases of these rocks. The rocks are enriched in LIL and LREE elements and depleted in HFS elements. The ratios of trace elements and rare earth elements in the studied region indicate that the basalts were formed by melting a garnet bearing peridotite at great depths and pressures. Negative Ce anomaly, Nb negative anomaly, Pb positive anomaly the role of continental lithosphere in contaminating the magmatic sources of volcanic rock in the study area. The Pb/Ce ratio similar to ocean island basalt (OIB) sources, induces OIB sources, the asthenospheric mantle, in the initial formation of basaltic magma. it can be concluded that the volcanic rocks of the area have formed in an intra-plate environment in an extensional regime.
Akbar Jabbari; Asghar Dolati; Alireza Shahidi; Amin Behrooz
Abstract
Abstract: The Alborz Mountain range is formed by collision between the Central Iran and Eurasia plates, since Late Triassic. Facieses studies on the Alborz and Central Iran indicate sedimentation in shelf and epicontinental shelf in passive margin of Gondwana during Paleozoic Era. This study represents ...
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Abstract: The Alborz Mountain range is formed by collision between the Central Iran and Eurasia plates, since Late Triassic. Facieses studies on the Alborz and Central Iran indicate sedimentation in shelf and epicontinental shelf in passive margin of Gondwana during Paleozoic Era. This study represents direction and paleostress analysis of the Central Alborz based on geometry and kinematics of faults; i.e. strike, dip, slicken line orientation and movement directions for Carboniferous and Permian Periods. Since many tectonic events occur after the Paleozoic Era in the Alborz Mountain range so just growth faults, active during sedimentation, which were not reactivated by later events were used for paleostress analysis. In total 15 stations, including 148 fault data are measured along the Tehran-Chalus road from Carboniferous and Permian outcrops. The data were rotated to the first position based on fold axes, when the layers were horizontal. FSA software (Fault Slip Analysis) was used to calculate orientations of principal stress directions. Primary results indicate a proximately North-South extension in Carboniferous and Permian Periods. Iran and adjacent area, rotated along vertical axis during its movements from Gondwana, in South, to Eurasia, in north, that based on the plate rotation the extension direction for Permian and Carboniferous Periods are NE-SW and ENE-WSW, respectively.
Geophysics
Shahrokh Pourbeyranvand; Mohammad Tatar
Abstract
The Alborz, as one of the important seismotectonic provinces in Iran, has a great vulnerability from natural disasters, especially seismic risk point of view, because of the existence of Tehran megacity in its southern edge. The importance of this area has caused a relatively dense GPS network around ...
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The Alborz, as one of the important seismotectonic provinces in Iran, has a great vulnerability from natural disasters, especially seismic risk point of view, because of the existence of Tehran megacity in its southern edge. The importance of this area has caused a relatively dense GPS network around it. In this study, the earthquake focal mechanism data obtained from different resources was used for stress tensor inversion in the Central Alborz. On the other hand, interpolation of the GPS vectors in rectangular grids and differentiation in the center of each grid cell was used for the study of strain rate in this area. The results showed special variation in principal axes of stress and strain rate, and also the changes in areal and maximum shear strain rates in different parts of the Central Alborz, which shows the geodynamic complexity of the study area. Finally, the angular differences between the maximum horizontal stress and strain rate compressive axis directions were calculated in the location of the clusters of the earthquakes. These calculations showed that the extent of the strain partitioning in the middle parts of the mountain range, where strike-slip motions on Mosha and Firuzkuh faults are observed, has more significant effect on the current deformation processes in the Central Alborz. Meanwhile, in the Northern parts of the range, where dominantly sip slip motions on Khazar Thrust and North Alborz fault occurs, deformation partitioning plays a minor role in the region.
F. Rostami; M. Delavari; S. Amini; A. Dolati
Abstract
The Permian volcanic rocks of Central Alborz (northeast of Baladeh- Siahbisheh) crop out between Ruteh and Nesen Formations. The volcanic rocks are predominantly basaltic and plagioclase- phyric. Ferromagnesian minerals such as clinopyroxene and olivine are not modally abundant and sometimes are totally ...
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The Permian volcanic rocks of Central Alborz (northeast of Baladeh- Siahbisheh) crop out between Ruteh and Nesen Formations. The volcanic rocks are predominantly basaltic and plagioclase- phyric. Ferromagnesian minerals such as clinopyroxene and olivine are not modally abundant and sometimes are totally altered. Based on microprobe data, clinopyroxene and plagioclase are diopside (En34.2-36.4 Wo43.1-47.2 Fs14.9-18.1) and labradorite (50<An%<55), respectively. Clinopyroxene and plagioclase geothermobarometric calculations shows the temperature and pressure ranges of 1050 to 1200 °C and 2 contents (4.94- 7.24 wt. %). Clinopyroxene chemical data display that the parent melt was alkaline basalt, generated in a within plate setting. On the basis of our findings it can be stated that, Central Alborz was a continental passive margin in middle- late Permian at south of Paleo-Tethys and its magmatism was likely triggered by late Paleozoic extensional tectonism of northern margin of Gondwana during the early stages of Neo-Tethyan development.
N Kohansal-Ghadimvand; SH Gholipouri; M.R Majidifard
Abstract
The early carboniferous Mobarak Formation was studied in southern flank of Ayenehvarzan–Dalichai anticline, in Aru and Seyedabad sections, east of Tehran. The aim of this study is to determine microfacies, interpretation of depositional environments and sequence stratigraphy of the Mobarak Formation. ...
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The early carboniferous Mobarak Formation was studied in southern flank of Ayenehvarzan–Dalichai anticline, in Aru and Seyedabad sections, east of Tehran. The aim of this study is to determine microfacies, interpretation of depositional environments and sequence stratigraphy of the Mobarak Formation. In this study, the thickness of Mobarak Formation in Aru and Seyedabad sections varies from 133 to 65 meters and consists of limestone with intercalations of shale and marl. According to lithological characteristics, the Mobarak Formation subdivided into several rock units. The Mobarak Formation is disconformably overlain by Jirud Formation and underlain by Dorod Formation. Ten microfacies have been recognized on the basis of depositional remarks and petrographic analysis. These carbonate facies belong to 4 major sub-environments including beach/tidal flat, lagoon, barrier/sand shoal and open marine. These facies deposited in a homoclinal carbonate ramp and include two sedimentary sequences.
S Soleymani; B Hamdi; A.R Karimi Bavandpur
Abstract
The studied section is located in the southern flank of the Central Alborz, 5 kilometers north of Shahmirzad City in the Semnan province. This section is situated at 35° 48′ 40″ N latitude and 53° 16′ 59″ E longitude. The Mila Formation has 5 measurable members in Type ...
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The studied section is located in the southern flank of the Central Alborz, 5 kilometers north of Shahmirzad City in the Semnan province. This section is situated at 35° 48′ 40″ N latitude and 53° 16′ 59″ E longitude. The Mila Formation has 5 measurable members in Type Section (Mila Kuh, Damghan City) and only in this studied section. This formation overlies conformably the Early Cambrian Lalun Sandstone Formation and underlies disconformably the Early Devonian red conglomerates. Studied Conodonts of this formation are of Proconodontus type belonging to Coniform Groups. 14 species and 6 genera of these conodonts were acquired indicating an age of Mid-Late Cambrian and Early Ordovician. These Conodonts are listed as below: Proconodontus serratus, Proconodontus muelleri, Proconodontus rotundatus, Prooneotodus sp?, Prooneotudus tenuis, Furnishina furnishi, Furnishina asymmetrica,Furnishina sp., Furnishina obliqus-Hirsutodontus?, Westergardodina cf. mossbergensis,Westergardodina fossa, Cordylodus, Cordylodus intermedius, Cordylodus lindstromi,Cordylodus proavus, Oneotodus nakamurai & Problematoconites sp. A remarkable point is the discovery of species Prooneotodus tenuis in the second member of Mila Formation because no conodont has already been reported from this member. Other microfossils such as Trilobites, Brachiopoda, Hyolithes, Eocrinoidae, Rusophycus, Cruziana, Paleoscoleidae and Sponges were also obtained indicating the deposition of Mila Formation in a shallow marine environment. These fossils assemblage are comparable with those from other parts of Iran and neighbor countries.
S Ansari; F Yaminifard; M Tatar
Abstract
In this study, 23 focal mechanisms were calculated by moment tensor inversion of small regionalـlocal earthquakes in the Western Alborz and surrounding areas using wave-form inversion method. Calculated reverse-fault focal mechanisms around the Khazar and Alborz Faults in the Central Alborz, considering ...
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In this study, 23 focal mechanisms were calculated by moment tensor inversion of small regionalـlocal earthquakes in the Western Alborz and surrounding areas using wave-form inversion method. Calculated reverse-fault focal mechanisms around the Khazar and Alborz Faults in the Central Alborz, considering southward-dipping nodal plane as the fault plane, are consistent with relatively low-angle thrusts. It also implies dominant compressionsl regime in the north of the Central Alborz. Focal mechanisms in 1990 Rudbar-Tarom Earthquake region show a combination of strike-slip mechanisms and a complex fault system in the middle of the Western Alborz. A major region of dominant strike-slip mechanisms is observed in the Talesh area, located in the west of the SouthCaspianBasin, and around the Masuleh, Sangavar and Bozqush faults. The only calculated focal mechanism close to the southern margin of the Western Alborz, considering the western part of the North Tehran fault as the fault nodal plane, implies leftـlateral motion in this area. In the south of the western AlborzMountains approaching the Central Iran, two calculated mechanisms indicate dominant reverse movement, similar to the 2002 Changoreh-Avaj Earthquake. Five focal solutions close to the Kushk-e Nosrat and Soltanieh Faults, considering these faults as the fault nodal planes, are consistent with right-lateral motion along them. Depth of the earthquakes in the studied region is in the range of 2 and 20 km, indicating the brittle upper crust in the region.
T Sarbandi Farahani; M.R Majidifard; M.R Kebriaee- Zadeh; M Mohammadi
Abstract
The Middle Jurassic rocks are widely distributed and superbly exposed in the AlborzMountains (Northern Iran). In the central part of the mountain range, near Mahdishahr (Northern Semnan), the Dalichai Formation, from the underlying conglomerate and sandstones of Shemshak Formation to the limestones of ...
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The Middle Jurassic rocks are widely distributed and superbly exposed in the AlborzMountains (Northern Iran). In the central part of the mountain range, near Mahdishahr (Northern Semnan), the Dalichai Formation, from the underlying conglomerate and sandstones of Shemshak Formation to the limestones of the overlying Lar Formation, is completely exposed on the southern slopes of the kuh-e-Rahband. At this area, the sedimentary succession with nearly 122 m thickness subdivided into four members starting with marl and medium to thick-bedded grey limestones to marly limestones. The lower boundary with the siliciclastics of the underlying Shemshak Formation is disconformity, whereas the upper boundary with the light and cliff-forming carbonates of the Lar Formation is rather inconspicuous and transitional. The Dalichai Formation in the east of Mahdishar section is fossiliferous. The ammonite fauna consist of 5 families, 22 genera and subgenera and 40 species, among them 8 species are recorded for the first time from Iran. Based on the ammonite fauna, 9 biozones were recognized that indicated the age of the Dalichai Formation in the investigated area ranges from the Upper Bajocian? to Upper Oxfordian. Pleobigeographically, the fauna shows close relationship to west Europe and sub-mediterranean regions. This indicates a paleogeographic position of the area at the northern Tethys during the Middle Jurassic.
S Alimardan; Sh Solaymani Azad; M Ghorashi; M.R Ghorashi; B Oveisi; A Hatami
Abstract
Due to urban population growth in recent decades and the need for decentralization of cities with limited facilities and increasing marginalization in the larger cities, construction of new cities around large towns has been considered by decision makers to develop a plan to create new cities around ...
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Due to urban population growth in recent decades and the need for decentralization of cities with limited facilities and increasing marginalization in the larger cities, construction of new cities around large towns has been considered by decision makers to develop a plan to create new cities around these towns. One of the most important parameters for the construction of new population centers is seismotectonic studies. Hashtgerd New Town in southern slopes of the Alborz (located 65 km northwest of Tehran) is located on the uplifted deposits of the Plio-Quaternary. Vertical tectonic movements in the range caused the height difference of about 300 m between Hashtgerd and its southern plain elevations. Due to the emplacement of the city on the uplifted Plio-Quaternary deposits, and the lack of information about the causative active fault in this region, an attempt has been made to investigate the morphotectonic characteristics of the area on the basis of survey satellite image, aerial photo, digital elevation model, and field observations. In the present study, an active fault zones with NW-SE trends has been identified with oblique-slip movements (compression with left-lateral strike-slip component). The N-NE stress direction, in regards to the abovementioned trend is oblique, and hence, the result could be a transpressional regime for the area. Recognition of mentioned active faults is very important for earthquake hazard assessment studies for the new town.
M Tatar; S.M Momeni; F Yaminifard
Abstract
The V shape kink of the AlborzMountains at its southern end reaches to the Garmsar city located 100 km southeast of Tehran metropolis. We investigated seismicity and seismotectonic features of the Garmsar area by precisely locating of microearthquakes recorded by our local dense seismological network ...
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The V shape kink of the AlborzMountains at its southern end reaches to the Garmsar city located 100 km southeast of Tehran metropolis. We investigated seismicity and seismotectonic features of the Garmsar area by precisely locating of microearthquakes recorded by our local dense seismological network and by the Iranian Seismological Center (IRSC). Our results indicate high seismic activity at the central and western parts of the Garmsar fault. Three computed focal mechanisms revealed compressional movements of the central part of this fault. Very little seismic activity is observed on the Eyvanekey and the Pishva faults. The only computed focal mechanism for the northern hills of the Garmsar fault shows tensional movements in this area, which refers to strain release among the Garmsar and Sorkheh reverse faults. Most of the calculated focal mechanisms in the Garmsar area indicate compressional and strike slip motions with overall P axis direction of 10° to 35°. The calculated P axis with NW-SE trend, close to the Sorkheh fault, is different from the other calculated P axes that show NNE-SSW direction. This is probably due to rotating of structures in this area, as revealed by recent GPS measurements in this region.
M.R Omidvar Ashkalack; A Khakzad; N Nezafati; M.A.A Mokhtari; B Borna; S Rozbeh Kargar
Abstract
The studied area is located in the western part of the Central Alborz structural zone and contains a bauxitic- lateritic horizon between the Elika and Shemshak formations. This horizon belongs to the middle Triassic, and croups out with E-W trend in the four regions (trends) including Zard Kuh- Loriteh, ...
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The studied area is located in the western part of the Central Alborz structural zone and contains a bauxitic- lateritic horizon between the Elika and Shemshak formations. This horizon belongs to the middle Triassic, and croups out with E-W trend in the four regions (trends) including Zard Kuh- Loriteh, Shagol- Sangrood, Abasak- Hir, and Arsheh Kuh- Zakabar. The complete cross section of bauxitic- lateritic horizon contain dark grey pisolites in the lower part, yellowish red laterite in the middle part, and an upper part with light grey color. Kaolinite and quartz are the main mineral components of this horizon. The minerals such as diaspore, bohemite, anatase, hematite and goethite present as minor phase. The grey- colored upper and lower parts contain high grade of Al2O3 and low grade of Fe2O3 while in the middle part, high grade of Fe2O3 and low grade of Al2O3. The average grades of Al2O3, Fe2O3, SiO2 and TiO2 in the samples are in turn 35%, 14%, 35% and 5%. The maximum grades of Al2O3 in the mentioned four trends are 51%, 61%, 48% and 48%. There is a distinctive negative correlation between Al2O3 and Fe2O3, between Fe2O3 and SiO2, and between Fe2O3 and TiO2. Furthermore, there is a positive correlation between Al2O3 and TiO2. The results of laboratory investigations indicated that the best bauxitic- lateritic horizon in the studied area considering grades of major oxides is the Abasak- Hir trend.
Z. Boroumand; E. Ghasemi- Nejad; M. R. Majidifard
Abstract
The Dalichai Formation at Talu section, 24 kilometers NE of Damghan is studied Palynologically. The Middle Jurassic sediments with a thickness of 168 meters in this section contain grey to green marl and grey marly limestone. A total of 35 samples were collected systematically and 200 palynological sildes ...
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The Dalichai Formation at Talu section, 24 kilometers NE of Damghan is studied Palynologically. The Middle Jurassic sediments with a thickness of 168 meters in this section contain grey to green marl and grey marly limestone. A total of 35 samples were collected systematically and 200 palynological sildes were prepared. Forty nine species of dinoflagellate cysts belonging to 30 genera were identified. A few fungal spores and foraminiferal test lining and spores and pollen grain were also recorded. Although, dinoflagellate species are abundant but all the species recorded were concentrated in lower parts of the section (0-110 meters). Two palynozones were identified; Cribroperidinium crispum Total Range Palynozone (Ccr), Dichadogonyaulax sellwoodii Interval palynozone (Dse). A local palynozoneof Ctenidodinium combazii/Ctenidodinium ornatum ornatum Acme Zone were also established in the succession. An age of Bajocian – Late Callovian was proposed for the succession studied.
Arman Heravi; H. Nazari; A. Shahidi; M. Talebian
Abstract
The Garmsar Fault with a length of about 75 km and E-W trend is located in Garmsar.This Fault observed in north of Garmsar and eastern part of central Alborz with slop toward north, continus east of Eyvanakey Fault. Base of the morphotectonical investigation, along the Garmsar Fault this ...
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The Garmsar Fault with a length of about 75 km and E-W trend is located in Garmsar.This Fault observed in north of Garmsar and eastern part of central Alborz with slop toward north, continus east of Eyvanakey Fault. Base of the morphotectonical investigation, along the Garmsar Fault this fault is devided to 5 segments from east (Dehnamak village) to the west (Eyvanakey), with attention to this segmentation we could consider the branch of kuh-e-sorkh Fault at west of Garmsar in kuh-e-sorkh anticline such as separated fault with slop toward north and pressure mechanism with small left-lateral strike slip component. Base on observations and Paleostress measurment along the Garmsar Fault in Bon-e-kuh station and eastern segment of this fault, we could consider that Paleostress direction around Neogen Time, is N-S with pressure component. However, base of data, is gain from morphotectonical investigations, young and overcome mechanism in eastern segment (Fault segment 1) left-lateral with pressure component, on the other side, in kuh-e-sorkh anticline at western part of research area, considered stress direction at quaternary period E-W under the effect of Thrust fault with left-lateral component. Base of this study from geometry point of view, the Garmsar Fault is a fault with slop toward north which is able to devide in to 5 segments that is strike and geometry of each fault segment mechanism is from left-lateral with pressure component until Tension and the Garmsar Fault is considered as an active fault in quaternary period. Maximum and minimum on the left horizontal displacement measured on the fault equal to 220 meters and 4 meters of a fault on the part of the fault system and third segment on the drainages of Garmsar displaced is visible.
F. Vaez Javadi
Abstract
There is a well-preserved plant macrofossils florizone near the Tiar village, south Amol, Central Alborz, Iran. It contains abundant plant maccrofossils belonging to 9 taxa of various orders, such as Equisetales, Filicales, Bennettitales, Cycadales, Ginkgoales and Coniferales. Based on the occurrence ...
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There is a well-preserved plant macrofossils florizone near the Tiar village, south Amol, Central Alborz, Iran. It contains abundant plant maccrofossils belonging to 9 taxa of various orders, such as Equisetales, Filicales, Bennettitales, Cycadales, Ginkgoales and Coniferales. Based on the occurrence of Equisetites beanii and Elatides thomasii an earlyMiddle Jurassic age is suggested for this assemblage. This florizone can be correlated to the plant macrofossils assemblage of Iva (Baladeh), Rudbarak (NE Semnan), Central Alborz; Golmakan (Binalud, Kopehdagh) and Pabdana and Hashooni (KermanBasin).
M. Asgharian Rostami; E. Ghasemi-Nejad; M. Shafiee Ardestani
Abstract
At this research are studied late cretaceous sediments at Ziarat-kola section, Central Alborz, in order to Palaeobathymetry and sea level change. These sediments are with about 200m thickness consist of monotonous Marl and limy marl. Based on Planktonic foraminifera gain Upper Maastrichtian stage (Abathomphalus ...
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At this research are studied late cretaceous sediments at Ziarat-kola section, Central Alborz, in order to Palaeobathymetry and sea level change. These sediments are with about 200m thickness consist of monotonous Marl and limy marl. Based on Planktonic foraminifera gain Upper Maastrichtian stage (Abathomphalus mayaroensis zone). In order toPalaeobathymetry and sea level change used to three methods common consisting of morphotype Planktonic foraminifera, ratio Planktonic foraminifera to benthic foraminifera and assigning genus and benthic foraminifera species. With morphotype analysis was indicated that third morphotype which are more deep index increase at the initial part and first morphotype that are shallow index increasing at middle section. In this manner, depth change was examinated to use two genus, Globotruncana (deep dweller) and Pseudoguembelina (Mixed layer dweller). In orther to assign paleodepth at this area used to Planktonic foraminifera to total foraminifera minus infaunal Benthic foraminifera and the regression equation [Depth = e (3. 58718 + (0. 03534 × %*p)].examination genus and Benthic foraminifera species depth index and such results gain at above method were indicating that this sediments in upper bathyal and middle bathyal. Thus, results indicate that beginning and end of are deeper from middle section.
P. Navi; M. Yazdi; R. Esmailpur; A. Khakzad
Abstract
Lavij coal deposit is situated at a distance of 48 km SW of Amol, in Central Alborz coalfield, North of Iran. Lavij coal-bearing strata in Central Alborz zone are within the Upper Triassic– Lower Jurassic formation. The coal-bearing sediments in this area are called Shemshak Formation ...
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Lavij coal deposit is situated at a distance of 48 km SW of Amol, in Central Alborz coalfield, North of Iran. Lavij coal-bearing strata in Central Alborz zone are within the Upper Triassic– Lower Jurassic formation. The coal-bearing sediments in this area are called Shemshak Formation (Upper Triassic –Lower Jurassic). This Formation consists mainly of sandstone, shale, calcareous sandstone, argillite and siltstone. Several coal seams with different thickness are interbeded with these sediments. The Shemshak Formation is underlain by the Upper Middle Triassic (thick bedded to massive dolomitic limestone) oolitic limestone (Elika Formation). It is also overlain in western section by the Upper Permian cherty limestone (Nesen Formation). The present paper deals with maceral, mineral and geochemical composition of these coals. Petrographical studies showed that the main macerals of these coals are vitrinite to semivitrinite, fusinite and exinite. The minerals of these coals are mainly clays like argillite, carbonates like calcite and sulphides like pyrite.
Seven samples were analyzed from ash of coal seam in the Lavij area. The samples were analyzed by XRF and ICP-OES for major and minor elements. The data processing showed K, Si, Al, Ti indicating presence of quartz and clay minerals, Fe, As, Mo, Se, Pb indicating presence of sulphides like pyrite, Ca and Mg indicating the presence of carbonates and Rb, Cr, Th, Ga, Ta, Nb, V indicating presence of clay minerals. The coal contained in low ash (17%) and low moisture (1.4%) and high volatile matter (32%) as compared to other coals in central Alborz.
Z. Mardani; M. Ghorashi; M. Arian; Kh. Khosrotehrani
Abstract
Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics.These indices have the advantage of being calculate from ArcGIS and remote sensing packages over large area as a reconnaissance tool to identify geomorphic anomalies possibly related to active tectonics.This ...
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Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics.These indices have the advantage of being calculate from ArcGIS and remote sensing packages over large area as a reconnaissance tool to identify geomorphic anomalies possibly related to active tectonics.This is particulary valuable in west-central Alborz where relatively little work on active tectonics based on this method was done,so this method is new and useful. Based upon values of the stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf),we used an overall index(Iat) that is a combination of the other indices that divides the landscape into four classes of relative tectonic activity. The moderat class of Iat is mainly in the south of Manjel dam,while the rest of the study area has high active tectonics (shahrud drainage basin and sefidrud drainage basin),and high to very high(Taleghan and Alamut drainage basin). The stream network asymmetry (T)was also studied using morphometric measures of Tranverse Topographic Symmetry.Analysis of the drainage basins and subbasins in the study area results in a field of T-vectors that defines anomalous zone of the basin asymmetry.Acomparsion of T index clearly coincide with the values and classes of active tectonics indices and the overall Iat index.
M. mohamadi; M. Yazdi
Abstract
There are many precious microremains of chondrichtyans (cartilage fishes) in calcareous beds of Geirud Formation. These micro remains consist of teeth, branchial denticles and sales species and genus of the family and subfamily: Phoebodontidae, Protacrodontoidea, HybodontoideaandCtenacanthoidea. Geirud ...
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There are many precious microremains of chondrichtyans (cartilage fishes) in calcareous beds of Geirud Formation. These micro remains consist of teeth, branchial denticles and sales species and genus of the family and subfamily: Phoebodontidae, Protacrodontoidea, HybodontoideaandCtenacanthoidea. Geirud Formation consists of alternating silisiclastics and calcareous beds with 1-2 basaltic units well distributed in Central Alborz. The upper Devonian/Lower carboniferous age assigned to Geirud Formation. The name of the Formation has been driven from type locality – Geirud village in north of Tehran. The upper Devonian/Lower carboniferous deposits have been studied along Alborz Mountain range and Central Iran. Faunal similarity between Famennian deposits of Central Iran and Eastern Alborz with Geirud Formation (Hairapetian & Klug 2002) confirm the basin relationship between these areas, also faunal relationship between these fauna and the fauna of Famennian in Morocco and Algeria confirm that these deposits belong to shelves of North Gondwanaland (Ginter & al., 2002). These fauna are associated with conodonts of expansa zone.
M. Asadi sarshar; A. Bahroudi; M. Qorashi; M. R. Ghassemi
Abstract
Estimate of moment rate is comparatively reckoned as a new method for dealing with tectonic activities rate in different regions and it prepares the way for putting together different methods. In fact, moment rate states rate of energy which exists in deformation system. There are three different approaches ...
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Estimate of moment rate is comparatively reckoned as a new method for dealing with tectonic activities rate in different regions and it prepares the way for putting together different methods. In fact, moment rate states rate of energy which exists in deformation system. There are three different approaches to state moment rate that each one express tectonic motion and movement of a region from a particular view. These three approaches consist of: geodetic (surveying), seismic and geology methods. Geodetic method which is determined on the basis of gained strain rate tensor from geodetic data, shows deformation rate (including seismic and aseismic) that is happening in the region at this moment in time. Moment rate which has gained on the basis of historical and instrumental catalogues, shows the total released seismic energy during quake events which are available in earthquake of region and geologic moment rate which gained with geometric parameters of faults, reveals potential of the faults in releasing stored elastic energy in. Geodetic moment rate, seismic moment rate (on the basis of historical and instrumental earthquake data) and geologic moment rate are estimated for Central Alborz region. The most moment rate in the study area belongs to geodetic approach (8.83×1019 Nm/yr) and then geologic moment rate (0.12×1019 Nm/yr) and finally the least quantity belongs to seismic moment rate (0.022×1019- 0.046×1019 Nm/yr). Considering, distribution of earthquake epicenters, the most seismic energy is released in the south parts of Central Alborz and considering high geodetic and geologic moment rates in north parts, it seems, north parts of Central Alborz have higher seismic potential.
R. Khavari; M. Ghorashi; M. Arian; Kh. Khosrotehrani
Abstract
The paper presents a method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography. Indices used include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height ...
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The paper presents a method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography. Indices used include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf). Results from the analysis are accumulated and expressed as an index of relative active tectonics (Iat), which divided into four classes from relatively low to highest tectonic activity. The study area along the south flank of the central Alborz mountain range in north Iran is an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than a single valley or mountain front. The recent investigations show that neotectonism has played a key role in the geomorphic evolution of this part of the Alborz mountain range. Geomorphic indices indicate the presence of differential uplifting in the geological past. The high class values (low tectonic activity) for Iat mainly occur in the south and southeast of the Karaj drainage basin, while the rest of the study area has classes of Iat suggesting moderate to high tectonic activity. Around the Amirkabir Lake, Iat has the highest value. The distribution of the indices defines areas associated with different mountain fronts and estimates of relative rates of tectonic activity. More than half of the study area is classified into classes 2 or 1 of high to very high tectonic activity in terms of the apparent geomorphic response. In different tectonic environments with greater rates of active tectonics, the values of indices would differ as well as their range in value. The stream network asymmetry (T) was also studied using morphometric measures of Transverse Topographic Symmetry. Analysis of the drainage basin and a number of sub-basins in the study area results in a field of T-vectors that defines anomalous zones of the basin asymmetry. We test the hypothesis that areas with great stream migration are associated with indicatives values of Iat.
H. Mosadegh; M. Lankarani
Abstract
The carbonate facies of Permian in Gaduk area (Central Alborz) are dominated by calcareous algae. Study of the facies resulted in recognition of several species of Cyanobacteria, Dasycladacean and Gymnocodiacean green algae and also Phylloid algae. In the studied succession, Phylloid algae are identified ...
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The carbonate facies of Permian in Gaduk area (Central Alborz) are dominated by calcareous algae. Study of the facies resulted in recognition of several species of Cyanobacteria, Dasycladacean and Gymnocodiacean green algae and also Phylloid algae. In the studied succession, Phylloid algae are identified in carbonate shoal facies. Cyanobacteria mostly occurred in tidal to lagoonal facies, as encrusters. Dasycladacean and Gymnocodiacean green algae mostly occurred in inner ramp facies. Gymnocodiaceans were found in deeper parts in comparison to Dasycladaceans. Occurrence of Cyanobacteria in depositional sequences coincides with type-one sequence boundaries. Phylloid algae are identified in the facies related to transgressive surfaces and maximum abundance of Dasycladaceans and Gymnocodiaceans was found around maximum flooding surfaces and in highstand systems tracts. Abundance of the calcareous algae shows an increasing trend from the base to the top of carbonate parasequences. Proliferation of the calcareous algae was found in close relationship to climate warming and ice-house to green-house transition in Permian of Alborz.
M. Shams; K. Seyed-Emami
Abstract
The Dalichai Formation and its ammonite fauna is studied for the first time in the Parvar area, Central Alborz. At Parvar the Dalichai Formation, with a thickness of about 70 m, consist of an alternation of grayish silty marls, marlstones, marly limestone and limestone and is subdivided into 5 members. ...
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The Dalichai Formation and its ammonite fauna is studied for the first time in the Parvar area, Central Alborz. At Parvar the Dalichai Formation, with a thickness of about 70 m, consist of an alternation of grayish silty marls, marlstones, marly limestone and limestone and is subdivided into 5 members. A rich ammonite fauna (407 specimens) have been collected from the member 4 and 5, comprising the following families: Phylloceratidae, Lytoceratidae, Oppeliidae, Haploceratidae, Sphaeroceratidae, Parkinsoniidae, Morphoceratidae and Perisphinctidae. These indicate a Late Bajocian and Bathonian age. Member five consists of greenish to reddish, nodular and flaggy limestones and is a typical condensed horizon.
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.
