Allen M.B.,Durham University |
Talebian M.,Geological Survey of Iran
Geological Magazine | Year: 2011
Structure varies along strike in the Zagros fold-and-thrust belt of Iran, which is a principal element in the Arabia-Eurasia continental collision. Pre-collision, Late Cretaceous ophiolite nappes (Kermanshah, Neyriz) and related nappes of deep marine sediments (Radiolarite Series) were emplaced next to two regions (Pusht-e Kuh arc, Fars) which later developed a consistent structural style across the range from the High Zagros Fault to the foreland limit of deformation. The intervening area has a zone of highly imbricated Arabian plate strata (the Bakhtyari Culmination) thrust southwest towards and over a low relief, low elevation region (the Dezful Embayment). There are no ophiolite nappes northeast of the Bakhtyari Culmination. Isopachs reflect these different structural patterns from Late Cretaceous time but not earlier. In Late Cretaceous time the Dezful Embayment recorded less deposition than adjacent areas to the northwest and southeast. In the Palaeogene there was little net difference between the Dezful Embayment and its margins. The Dezful Embayment has been a depocentre since roughly 35 Ma, which is the likely time of initial collision between Arabia and Eurasia. We propose that the syn-collision structure and stratigraphy of the Zagros is therefore strongly influenced by the variation in Late Cretaceous ophiolite emplacement, but the original cause of this variation is not clear. © 2011 Cambridge University Press.
Allen M.B.,Durham University |
Kheirkhah M.,Geological Survey of Iran |
Neill I.,Durham University |
Emami M.H.,Geological Survey of Iran |
And 2 more authors.
Journal of Petrology | Year: 2013
New whole-rock and Sr-Nd isotopic analyses of Quaternary lavas from Kurdistan Province, western Iran, shed light on the nature of orogenic plateau magmatism during continental collision and the possible role of accessory minerals during mantle partial melting in this tectonic setting. The sampled lavas are from the Turkish- Iranian plateau within the Arabia-Eurasia collision zone. Compositions are typically basanite, hawaiite and alkali basalt, with minor rhyolite. Most of the basic samples from the Qorveh- Bijar region have elevated abundances of large ion lithophile elements (LILE) and light rare earth elements (LREE) (e.g. 76 ppm
Allen M.B.,Durham University |
Kheirkhah M.,Geological Survey of Iran |
Emami M.H.,Geological Survey of Iran |
Jones S.J.,Durham University
Geophysical Journal International | Year: 2011
New offset determinations for right-lateral strike-slip faults in Iran revise the kinematics of the Arabia-Eurasia collision, by indicating along-strike lengthening of the collision zone before a change to the present kinematic regime at ~5 Ma. A series of right-lateral strike-slip faults is present across the Turkish-Iranian plateau between 48°E and 57°E. Fault strikes vary between NW-SE and NNW-SSE. Several of the faults are seismically active and/or have geomorphic evidence for Holocene slip. None of the faults affects the GPS-derived regional velocity field, indicating active slip rates are ≥2 mm yr-. We estimate total offsets for these faults from displaced geological and geomorphic markers, based on observations from satellite imagery, digital topography, geology maps and our own fieldwork observations, and combine these results with published estimates for fault displacement. Total right-lateral offset of the Dehu, Anar, Deh Shir, Kashan, Ab-Shirin-Shurab, Kousht Nousrat, Qom, Bid Hand, Indes, Soltanieh and Takab faults is ~250 km. Other faults (North Zanjan, Saveh, Jorjafk, Rafsanjan, Kuh Banan and Behabad) have unknown or highly uncertain amounts of slip. Collectively, these faults are inferred to have accommodated part of the Arabia-Eurasia convergence. Three roles are possible, which are not mutually exclusive: (1) shortening via anticlockwise, vertical axis rotations; (2) northward movement of Iranian crust with respect to stable Afghanistan to the east; (3) combination with coeval NW-SE thrusts in the Turkish-Iranian plateau, to produce north-south plate convergence ('strain partitioning'). This strike-slip faulting across Iran requires along-strike lengthening of the collision zone. This was possible until the Pliocene (≥ 5 Ma), when the Afghan crust collided with the western margin of the Indian plate, thereby sealing off a free face at the eastern side of the Arabia-Eurasia collision zone. Continuing Arabia-Eurasia plate convergence had to be accommodated in new ways and new areas, leading to the present pattern of faulting from eastern Iran to western Turkey, and involving the westward transport ('escape') of Anatolia and the concentration of thrusting in the Zagros and Alborz mountains. © 2010 The Authors Geophysical Journal International © 2010 RAS.
Aftabi P.,Geological Survey of Iran |
Roustaie M.,Geological Survey of Iran |
Ian Alsop G.,University of Aberdeen |
Talbot C.J.,Uppsala University
Journal of the Geological Society | Year: 2010
Interferometric synthetic aperture radar (InSAR) imaging is a powerful technique that is increasingly used to extract detailed 3D information on Earth surface structures, including exposed diapiric surfaces. We have used InSAR to map, for the first time, the cumulative surface deformation in a 6 km × 3 6 km region surrounding an active salt diapir (Syahoo) and its associated surface salt flow (or namakier) exposed in the Zagros Mountains of southern Iran. Images provided by the European Space Agency were acquired in 12 increments (ranging in length between 35 and 1248 days) over a 14 year interval between July 1992 and May 2006. The deformation of the salt surface is non-steady, with (extrapolated) rates of displacement varying between surficial uplifts of +1.4 mm day-1 (+511 mm a-1) and subsidence of -2.2 mm day-1 (-803 mm a-1). Growth of a central topographic dome occurs following short wet intervals to create a salt fountain morphology, which then slowly decays during the intervening long dry periods. Salt associated with dynamic 'bulging' of the central dome during wet intervals may flow laterally via gravity spreading into the surrounding salt sheet, resulting in deflation and subsidence of the dome, which is counteracted by growth and inflation of the adjacent namakiers. Salt 'bulges' that migrate down the namakier, resulting in local inflationary and deflationary cycles of the surface, may be regarded as episodic pulses of gravity spreading. Areas of inflation and deflation are also observed to commonly reverse during dry to wet periods, as the overall salt system effectively self regulates as it continually strives for dynamic equilibrium. As long as the source of salt remains undepleted, gravity spreading of the dome ultimately results in more buoyancy-driven salt flowing up the diapiric neck to replenish and feed the extrusion and maintain the gross fountain morphology. © 2010 Geological Society of London.
Keshavarzi B.,Shiraz University |
Moore F.,Shiraz University |
Najmeddin A.,Shiraz University |
Rahmani F.,Geological Survey of Iran
Science of the Total Environment | Year: 2012
Selenium (Se) deficiency is reported by some authors to be an important factor in the etiology of esophageal cancer (EC) in the Golestan province of Iran. In order to further investigate the role of Se and selected trace elements in the occurrence of EC disease, 663 samples including 206 cultivated soils, 247 sediments, 45 loess deposits and 165 grain samples from 45 villages in the Golestan province of Iran were collected and analyzed. Villages in the study area were classified into 2 groups according to the EC incidence in the local population. The results of this study demonstrate that, contrary to the expected trend, total Se concentrations in soil, grain, sediment, and loess samples increase from the low to the high EC areas suggesting that Se deficiency does not play a major role in the etiology of EC. On the other hand, antimony (Sb), and strontium (Sr) content in soil, grain, loess, and sediment samples is much higher in the high esophageal cancer area, which may be a significant factor. Total zinc (Zn) concentrations in soil, grain, loess, and sediment samples decrease from the low to the high cancer areas. Therefore, Zn deficiency may be a significant factor in EC incidence rate in the Golestan province. © 2012 Elsevier B.V.
Wilmsen M.,Senckenberg Naturhistorische Sammlungen Dresden |
Fursich F.T.,Friedrich - Alexander - University, Erlangen - Nuremberg |
Majidifard M.R.,Geological Survey of Iran
Cretaceous Research | Year: 2013
The Shah Kuh Formation of the Khur area (Central Iran) consists of predominantly micritic, thick-bedded shallow-water carbonates, which are rich in orbitolinid foraminifera and rudists. It represents a late(est) Barremian - Early Aptian carbonate platform and overlies Upper Jurassic - Barremian continental and marginal marine sediments (Chah Palang and Noqreh formations); it is overlain by basinal deposits of the Upper Aptian - Upper Albian Bazyab Formation. The lithofacies changes at both, the base and top of the Shah Kuh Formation are gradational, showing that the formation is part of an overall transgressive sedimentary megacycle, and that the formational boundaries are potentially diachronous on larger distances. Analyses of facies and stratal geometries suggest that the Shah Kuh carbonate system started as a narrow, high-energy shelf that developed into a large-scale, flat-topped rudist platform without marginal rim or steep slope. The Shah Kuh Platform is part of a large depositional system of epeiric shallow-water carbonates that characterized large parts of present-day Iran during Late Barremian - Aptian times (" Orbitolina limestones" of NW and Central Iran, the Alborz and the Koppeh Dagh). Their biofacies is very similar to contemporaneous deposits from the western Tethys and eastern Arabia, and they form an important, hitherto poorly known component of the Tethyan warm-water carbonate platform belt. © 2012 Elsevier Ltd.
Ghassemi M.R.,Geological Survey of Iran
Earth-Science Reviews | Year: 2016
A database of Iranian earthquakes during the instrumental period (1900-2014) is used to analyze geometric and kinematic aspects of the surface ruptures in different seismotectonic regions of the country. Majority of the ruptures have occurred along or associated with known geological or active faults. Thrust and strike-slip faults show a maximum surface rupture length of 85 and 125 km respectively. Excluding the distributed displacements on bedding thrusts during the 1979 Tabas earthquake, which was summed up differently to ~1.5 and ~3.0 m, maximum displacement on individual faults of thrust mechanism is 1.5 m, while strike-slip faults show a maximum horizontal displacement of 4.5 m. Surface rupture zone width of ~3 km is observed in an strike-slip event, and a ~4 km distance between the known active fault and the surface rupture of an event suggests that care should be taken in evaluation of setback zone for rupture hazards of some faults with complex geometry/kinematics. Partitioning in space and time of ruptures in earthquakes requires a better understanding of exact kinematics of active fault zones. While rerupturing of a fault segment in alternating events complicates the rupture history of the segment, simultaneous rupture of several fault segments and sympathetic faulting should be taken into account for evaluation of earthquake hazard in specific regions with such possible seismotectonic setting. Secondary ruptures and fractures, either in the presence or absence of primary surface ruptures, develop via different mechanisms, and complicate the surface deformations. While surface ruptures are frequently associated with earthquakes in eastern Iran, these features are very rare in Zagros and Makran regions. Empirical relations are suggested among surface rupture length, maximum displacement and moment magnitude for different earthquake fault mechanisms in Iran, which may be more compatible to the events within Iran. Using these relations the maximum surface rupture length, maximum surface displacement, and the associated maximum credible earthquakes are suggested for different regions in Iran. The suggested values may also be used for estimation of earthquake magnitudes in paleoseismological studies. © 2016 Elsevier B.V.
Sheikholeslami M.R.,Geological Survey of Iran |
Kouhpeyma M.,Geological Survey of Iran
Journal of Geodynamics | Year: 2012
The Binalud Mountains are situated in the south of the Kopeh Dagh as a transitional zone between the Alborz and Central Iran zones. The Palaeotethys suture of the north Iran is located in this area. The Binalud Mountains consists of relatively thick successions of sedimentary, metamorphic and igneous rocks. The earliest deformation, a polyphase synmetamorphic deformation which occurred entirely in ductile conditions, is distinguished in the metamorphic rocks of the eastern part. D1, D2 and D3 deformation phases are related to this deformation. The D4 deformation affected the area after a period of sedimentation and erosion. The thrust faults of the central and southern part of the eastern Binalud were classified as structures related to the D5 tectonic event. From the geodynamic point of view, in Late Palaeozoic times the studied area formed an oceanic trench generated by the subduction of the Palaeotethys oceanic lithosphere beneath the Turan Plate. In the Late Triassic, the Early Cimmerian Event resulted in a collisional type orogeny generating a transpression polyphase deformation and the metamorphism of Permian and older sediments. Following this collision, granite intrusions were emplaced in the area and caused contact metamorphism. The exhumation and erosion of the rocks deformed and metamorphosed during Early Cimmerian Event caused the formation of molassic type sediments in a Rhaetian-Lias back arc basin. The continuation of convergence between the Turan and Iran Plates caused the metamorphism of these sediments and their transformation to phyllite and meta-sandstone. During Late Mesozoic and Early Cenozoic times, the convergence between Central Iran and Turan Plates continued and a NE compression caused folding of the Cretaceous and older rocks in the Kopeh Dagh area. In the Binalud area this deformation caused the generation of several thrust fault systems with S to SW vergence, resulting in a thrusting of Palaeozoic and Mesozoic successions on each other and on the Neogene sediments at the southern border of the Binalud Mountains. © 2012 Elsevier Ltd.
Atapour H.,Geological Survey of Iran
Environmental Earth Sciences | Year: 2012
In order to investigate the environmental geochemistry of groundwaters in the urban areas of Kerman city, 50 samples of natural groundwaters, urban groundwaters and drinking waters were collected. High values of salinity (5. 8 ‰), electrical conductivity (10,270 μS/cm), total dissolved solids (TDS) (5,140 mg/kg), fluorine (4. 9 mg/kg), chlorine (3,974 mg/kg), bromine (1. 6 mg/kg) and sulfate (4,306 mg/kg) in the northern part of the studied area are caused by dissolution of evaporate bed rocks and Quaternary salt plains. Low values of salinity (0. 5 ‰), electrical conductivity (973 μS/cm), TDS (486 mg/kg), fluorine (0. 8 mg/kg), chlorine (297 mg/kg), bromine (0. 25 mg/kg) and sulfate (262 mg/kg) are only reported in the southern part of the Kerman city. High values of nitrate (NO3 -) range from 134 to 725 mg/kg and nitrite (NO2 -) content is variable between 0. 04 to 23. 45 mg/kg. These values indicate mixing of groundwaters with wastewaters. The heavy metal values in groundwaters around the Kerman city show 20. 5 μg/kg Cu, 5. 88 μg/kg Mo, 16. 2 μg/kg Pb, 70 μg/kg Zn, 11. 6 μg/kg Cr, 1. 99 μg/kg Co, 4. 13 μg/kg Ni, respectively. Furthermore, the natural aquifers of Kerman city contain 24 μg/kg Cu, 8. 15 μg/kg Mo, 18. 25 Pb, μg/kg, 193 μg/kg Zn, 14. 7 μg/kg Cr, 3. 97 μg/kg Co and 7. 45 μg/kg Ni, respectively. The results demonstrate that the main sources of contamination are related to the natural evaporates, mixing of groundwaters with wastewaters and constructional materials in the area. © 2012 Springer-Verlag.
Beiki M.,Uppsala University |
Pedersen L.B.,Uppsala University |
Nazi H.,Geological Survey of Iran
Geophysics | Year: 2011
This study has shown that the same properties of the gravity gradient tensor are valid for the pseudogravity gradient tensor derived from magnetic field data, assuming that the magnetization direction is known. Eigenvectors of the pseudogravity gradient tensor are used to estimate depth to the center of mass of geologic bodies. The strike directions of 2D geological structures are estimated from the eigenvectors corresponding to the smallest eigenvalues. For a set of data points enclosed by a square window, a robust least-squares procedure is used to estimate the source point which has the smallest sum of squared distances to the lines passing through the measurement points and parallel to the eigenvectors corresponding to the maximum eigenvalues. The dimensionality of the pseudogravity field is defined from the dimensionality indicator I, derived from the tensor components. In the case of quasi-2D sources, a rectangular window is used in the robust least-squares procedure to reduce the uncertainty of estimations.Based on synthetic data sets, the method was tested on synthetic models and found to be robust to random noise in magnetic field data. The application of the method was also tested on a pseudogravity gradient tensor derived from total magnetic field data over the Särna area in west-central Sweden. Combined with Euler deconvolution, the method provides useful complementary information for interpretation of aeromagnetic data. © 2011 Society of Exploration Geophysicists.