Geology of Iran - Knowledge

1300: 1758: 19: 907:(e.g., Alborz, East of Iran, Zagros). There is strong stratigraphic evidence that transition from Vendian to Lower Cambrian was a progressive one, without hiatuses; there is no evidence for any orogenic or epeirogenic movements in Iran at this time (e.g., south of Zanjan, Valiabad Chalus, Shahin Dezh). Early Cambrian started with an alternation of shale, phosphate-bearing limestone, and dolomite sitting conformably and transitionally over Vendian dolomites. Transition from Soltanieh Formation to 580:, is formed on the Hercynian metamorphosed basement at the southwestern margin of the Turan Platform. The belt is composed of about 10 kilometres of Mesozoic and Tertiary sediments (mostly carbonates) and, like the Zagros, was folded into long linear northwest–southeast trending folds during the last phase of the Alpine Orogeny, in the Miocene and Plio-Pleistocene time. No magmatic rocks are exposed in Kopet Dagh except for those in the basement in the Aghdarband and some 2672: 1074:. Transition from Middle to Upper Triassic coincides with Early Cimmerian orogenic episode, which led to the segmentation of the sedimentary basin into three sub-basins: Zagros in the south and southwest, Alborz in the north, and Central Iran. The Lower Jurassic rocks conformably overlie the Upper Triassic units; so are the Early Cretaceous deposits over the Upper Jurassic strata (e.g., Zagros). In North and Central Iran, the Upper Triassic and Lower–Middle 2682: 625:. Alborz is characterized by the dominance of platform-type sediments, including limestone, dolomite, and clastic rocks. Rock units from Precambrian to Quaternary have been identified, with some hiatuses and unconformities in Paleozoic and Mesozoic. Unlike its northern and southern boundaries, (Caspian Sea and Central Iran, respectively) there is not a consensus regarding the eastern and the western limits of Alborz. The 135:–bearing sutures. Other criteria such as structural style, crustal character and age of basement consolidation, age and intensity of deformation, age and nature of magmatism, are used to subdivide these major zones into smaller elements. The three major units and their main constituents could be defined as the southern, central and northern units. The southern unit has a crystalline basement consolidated in the 2279: 588:, it was covered with a vast continental shelf sea. In this period of time and due to transgression as well as rapid subsidence basin, the western part became deeper. In this basin, a thick sequence of continuous marine and continental sediments was deposited (about 10 km). No major sedimentary gap or volcanic activities during 1907:

and played a great role in the geological evolution of Iran. This event started under a compressional regime, followed by an extensional one. The compressional regime, that was associated with significant intrusive magmatic activities, led to the closure of the oceanic basins and Neothetyan rifts. In

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situated in the southeast of the Caspian Sea and in much smaller portions in the central and western parts of the Central Alborz Range. The central part of the Central Alborz Range is formed predominantly of the Triassic and Jurassic rocks, while the northwestern section of the range is made chiefly

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was closed and the Arabian Plate collided with the Iranian Plate and was pushed against it, and with the clockwise rotation of the Eurasian Plate towards the Iranian Plate and their final collision, the Iranian Plate was pressed against the Turan Platform. This collision folded the entire rocks that

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or coloured melange of Zabol–Baluch Zone). Located to the west of Zabol–Baluch Zone, Lut Block is the main body of Eastern Iran. Lut Block extends for about 900 kilometres (560 mi) in a north–south direction. It is bounded in the north by Dorooneh fault and in the south by Jazmurian depression.

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The Late Cimmerian orogeny occurred as a significant tectonic event in Iran in Late Jurassic–Early Cretaceous times. This event is represented by folding, facies changes in sedimentary environments, angular unconformity, magmatism, and metamorphism (e.g., Alborz, Sanandaj–Sirjan, and Central Iran).

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have a widespread occurrence in Iran and can be grouped as follows: Ultramafic and mafic units of Late Precambrian–Early Cambrian. Although comparable to modern ophiolites, these rocks do not display all typical features of an oceanic crust. The term “old ophiolite” might be a misnomer. These rocks

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This sedimentary complex provides suitable conditions for accumulation of hydrocarbons. Kopet Dagh sedimentary rocks were placed in their current position due to uplifting at the end of the Miocene. The Kopet Dag Range, itself, is made chiefly of Cretaceous rocks with a smaller portion of Jurassic

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with an age of 630–530 million years have been reported from many localities in Iran, particularly in Central Iran and Azerbaijan. These magmatic rocks seem to be related to the Pan-African tectonic-magmatic episode. Most magmatic rocks of this time bear an alkaline nature. The following magmatic

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depression to the northern mountains of Tabriz (Mishu, Morou) and northwest of Azerbaijan and the Caucasus. This event divided Azerbaijan into two blocks, one block in the northeast with subsidence and sedimentation in Early Devonian and the other in the southwest which remained high until Late

223:. The northern unit represents a marginal strip of the Hercynian realm of Central Asia- broadly overlapped by the Alpine realm. It was deformed and largely consolidated by the Early Cimmerian folding and the Late Alpine folding. The northern unit comprises the South Caspian Depression and the 360:

eras. As far as the trends, and particularly the folding style is concerned, some researchers consider the Sanandaj–Sirjan Zone as being similar to Zagros; however, considerable differences exist in rock types, magmatism, metamorphism, and orogenic events. There are some similarities between

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as the Arabian Plate collided with the Iranian Plate and was pushed against it, and with the clockwise movement of the Eurasian Plate towards the Iranian Plate and their final collision, the Iranian Plate was pressed from both sides. The collisions finally caused the folding of the Upper

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began, therefore, with Eocene volcanism in southwestern and south-central parts of the Alborz and continued with the uplift and folding of the older sedimentary rocks in the northwestern, central and eastern parts of the range during the orogenic phases of importance that date from the

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begins with the Cretaceous–Paleocene boundary that is characterized by striking changes in sedimentary environments (e.g., Alborz, Central Iran). An unconformity has been reported from many locations in Iran. Both continuous and discontinuous transitions have been discovered between

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in Central Iran. This tectonic phase started with tension or extension leading to the formation of rifts and generation of oceanic crust (e.g., in Takab and Anarak) and ended with folding, closure, metamorphism, growth of the continental crust, and development of regional faults.

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sediments have a detrital nature, consisting mainly of shale and sandstone with thicknesses varying from a few meters to more than 3,000 metres (9,800 ft). The presence of plant remains and coal beds suggest a continental or lagoon environment for the deposits. The

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marine deposits has yet been discovered in Iran. Upper Carboniferous deposits are not significantly present in Iran and have only been identified in several localities from index goniatites. After a general regression and a distinct hiatus in Upper Carboniferous,

768:. According to some authors, the northeastern corner could be included in Alborz and the southeastern part in Sanandaj–Sirjan. Some believe that most of Azerbaijan lies in a zone called Azerbaijan–Alborz, and as they indicate, this zone is bounded in the north by 170:

The central unit, which comprises the central Iran and the Alborz, is interpreted as an assemblage of fragments that were in the vicinity of the Arabian Plate and formed a marginal section of Rodinia and Pannotia in the Neoproterozoic and of Gondwana in the

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volcano-sedimentary deposits with a strip of Paleozoic rocks and a band of Triassic and Jurassic rocks in the southern parts, both in a northwest–southeast direction. With the northward movement of Africa and the Arabian plate and with the closure of the

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volcanic belt is supposed to have resulted from the collision of the Arabian and Central Iranian continental plate margins. It is represented by sub-alkaline volcanics that vary in composition from basaltic through andesitic to rhyolitic composition.

219:. Finally there is the northern unit which is separated from the central unit by the North Iran Suture. It is characterized by continental crust including remnants of more or less cratonized former Paleozoic oceanic crust that seems to reflect the 1645:. Ultramafic and mafic rocks also occur in association with large gabbroic intrusions. This type probably resulted from differentiation in a large mafic magma chamber, comparable to those of the layered mafic intrusions. Examples occur in Sero, 1908:

some areas, slices of the oceanic crust have obducted onto the continental margins producing what could be called ophiolite assemblages or coloured melanges (e.g., mostly seen suture zone between Sanandaj–Sirjan and Zagros, and alongside

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can be recognized. Central Iran in a broad sense, comprising the whole area between the North and South Iranian ranges. Within the Iranian plate the Central-East Iran microplate is bordered by the Great Kavir Fault in the north, by the

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rocks in Iran consist mainly of limestone, sandstone, shale and volcanic materials, known as Niur Formation in Central Iran. The Lower Devonian rocks have been reported from several localities in Central Iran (e.g., Tabas, Sourian,

307:. In the Elevated Zagros or the Higher Zagros, the Paleozoic rocks could be found mainly in the upper and higher sections of the peaks of the Zagros Mountains along the Zagros main fault. On the both sides of this fault, there are 2013:. The Pasadenian orogeny is the most important phase in forging the current shape of Iran. Some younger orogenic events might be the continuation of this orogenic phase (e.g., Alborz–Azerbaijan axis, Zagros, Central Iran). 1769:

in Iran is controversial; the Hercynian in Iran is largely represented by extensional rather than compressional tectonics (e.g., Sanandaj–Sirjan). Iranian microplates east and northeast of the Zagros were detached from

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the Carboniferous magmatic activities in northwestern Iran and normal faulting and tilted blocks in the High Zagros Belt which, taken together, support extensional deformation related to the Variscan or Hercynian

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are a typical example. There is strong evidence for significant magmatic activities in Late Paleozoic–Early Mesozoic (Early Permian to Early Jurassic) in Iran. Examples include: magmatic rocks in the Southern

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and faults like Shahr-e-Babak and Abadeh, and to the south-southwest by the main thrust fault of Zagros. A striking feature of this zone is the presence of immense volumes of magmatic and metamorphic rocks of

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orogenic events that caused continental and oceanic rifting, followed by closures and collisions in vast areas of Iran (e.g., Sanandaj–Sirjan). The Mesozoic magmatic rocks can be divided into three groups:

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in the east, although the continuation of the Alborz, bear features comparable to those of Central Iran. The Alborz mountain range is only 60–130 km wide and consists of sedimentary series dating from

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was accompanied by faulting and fragmentation that led to a different sedimentary facies in Azerbaijan. This orogenic episode generated the Tabriz fault, extending in a northwest–southeast direction from

247:. Zagros is in fact the northeastern edge of the Arabian Plate. Some important features of Zagros include: Absence of magmatic and metamorphic events after Triassic, and low abundance of the outcrops of 831:

by various authors. Isotopic data of Iranian basement rocks give ages between 600 and 900 Ma. A similar range of isotopic data had been obtained for Arabian Shield rocks. An important post-Pan-African

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in the northern Iran and tensional tectonics in the south. There is evidence that the compressional phase was preceded by tension and rift development. The compressional phase, happening in the

143:–type Paleozoic development and comprises the Zagros folded belt, southern and southwestern parts of the Zagros. This section made a part of the Arabian Plate that was located on the margin of 343:

This zone is located to the south-southwest of Central Iran and the northeastern edge of Zagros range. In the north and northeast, this zone is separated from Central Iran by depressions like

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The effects of this orogenic episode in Iran can be traced from the Late Devonian. Due to the scarcity of magmatism, metamorphism, and folding related to this episode, the role of the

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in Iran is characterized by facies change in sedimentary basins, hiatuses, and epeirogenic movements (e.g., parts of Alborz, Zagros, and Central Iran). This phase, starting from Late

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sediments are sitting on the Vendian sediments through an angular unconformity. In the Late Ordovician, most parts of Iran were affected by epeirogenic movements; this coincides with

381:, runs east and almost parallel to the Sanandaj–Sirjan Zone, and owes its existence to the widespread and intensive volcanic activity which developed on the Iranian plate from the 705:

are found mainly in the southwestern and south-central parts of the range. The far northwestern part of the Alborz that constitutes what is called the Western Alborz Range or the

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in front of the Iranian Plate. The process of collision continues to the present and as the Arabian Plate is being pushed against the Iranian Plate, the Zagros Mountains and the

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Considering geological and structural units of Iran, three main structural units or zones could be distinguished in Iran. These units or zones are separated from each other by

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With regards to the geological evidence, this event was of compressional nature. This tectonic phase is represented by significant changes in the sedimentary environments,

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Fault in the east. It is surrounded by the Upper Cretaceous to Lower Eocene ophiolite and ophiolitic melange. The microplate consists of different structural components;

1193: 773: 70: 476:, whereas the western boundary with Central Iran is Nayband fault and Shotori Mountains. The oldest units include upper Precambrian Lower Cambrian schists overlain by 410:

Located in a triangle in the middle of Iran, Central Iran is one of the most important and complicated structural zones in Iran. In this zone, rocks of all ages, from

1397:. They are mainly alkaline in nature and are more abundant in Sanandaj–Sirjan. In Jurassic–Cretaceous, intrusive rocks exceed volcanic rocks; a significant number of 828: 903:. The influence of the orogenic episode is evident at the base of the Vendian sediments. Deposition of shallow marine sediments covered large areas in Iran during 552:

fault being the most important one. Along these faults lies large section of ophiolite series. The oldest rocks in this zone are the ophiolites of Late Cretaceous–

488:) to the east. In contrast to Lut Block, the Flysch Zone is highly deformed and tectonized and consists of thick deep-sea sediments like argillaceous and silicic 516:, and subordinate serpentinized ultramafic rocks. The basement is likely composed of an oceanic crust. Most rock units in this zone fall into three main groups: 848: 45: 952: 944: 852: 621:

mountain range forms a barrier between the south Caspian and the Iranian plateau. This range is located in northern Iran, parallel to the southern margin of

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Volcanic rocks of andesitic-basaltic composition accompany Upper Paleozoic sedimentary strata in many areas all over Iran. Basaltic rocks associated with

1157: 1124:). Oligocene sediments in most parts of Iran are of shallow marine character, turning into marine facies in Upper Oligocene through Lower Miocene (e.g., 1087:

affects most parts of Iran, leading to uplift, folding, and faulting. This is a prelude to significant developments in the geological evolution of Iran.

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rocks on the both sides. The Folded Zagros (the mountains south of the Elevated Zagros and almost parallel to the main Zagros fault) is formed mainly of

75: 50: 295:. This collision primarily happened during the Miocene and folded the entire rocks that had been deposited from the Carboniferous to the Miocene in the 2242:"Foraminiferal-based paleobiogeographic reconstructions in the Carboniferous of Iran and its implications for the Neo-Tethys opening time: a synthesis" 1312: 1037: 1013: 956: 916: 80: 1825:

is one of the most important tectonic events in the geological history of the earth. Many diverse features are associated with this phase, including

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Series in Northern Sanandaj–Sirjan. Ultramafic and mafic rocks and their metamorphosed equivalents could be observed in Eastern Iran (Fariman area),

1241: 1165: 1048: 1041: 1021: 1017: 908: 876: 872: 844: 473: 60: 887:, and Anarak metamorphic units. The sedimentary facies of Precambrian–Lower Cambrian rocks in Northern Iran is different from that of Central Iran. 1288: 1284: 1173: 1169: 924: 880: 868: 864: 55: 1341: 1161: 1149: 227:

Range. These three main structural units are divided into some smaller geological and structural subdivisions which include the following zones:

827:, partial granitization and partly by intense folding took place in the Late Precambrian. This event has been attributed to the 'Baikalian' or 777: 769: 2637: 1794: 1373:: These rocks occurred mainly as a result of extension or tension related to the continental rifting, or subduction of the developed oceanic 537: 65: 30: 1083:

deposits, characterized by diverse sedimentary facies, are widespread all over Iran. In Late Cretaceous, tectonic movements related to the

884: 40: 1739:, caused the marine facies of Barut and Zaigoon Formations to change into the continental facies of Lalun Formation, and continued on to 1240:

composition, in Ghareh Dash, Azerbaijan. Volcanic rocks associated with Kushk Series in the Bafq area. Volcanic rocks of Rizu, Dezu, and

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age. The oldest rocks in Iran belong to the Kushk Series consisting of clastic sediments, acidic volcanic, tuff, and carbonates (mainly

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stages are characterized by rapid subsidence, deposition, and facies changes in both marine and continental sedimentary basins (e.g.,

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marine transgression deposits cover most parts of Iran (e.g., Alborz, Zagros, Central Iran); The Permian sediments are represented by

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series can be attributed to this phase: Doran-type intrusions in Azerbaijan. Narigan and Zarigan-type intrusive bodies extend from

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The Neo-Tethys opening and rifting of Iran from the northern margin of Gondwana has probably occurred sometime between the latest

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about 1.78 million years ago and after several known eruptions around 600,000 and 280,000 years ago, it finally erupted in the

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Map showing geology, oil and gas field, and geologic provinces of Iran pubs.usgs.gov/of/1997/ofr-97-470/OF97-470G/Iranmap.pdf

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Map showing geology, oil and gas field, and geologic provinces of Iran pubs.usgs.gov/of/1997/ofr-97-470/OF97-470G/Iranmap.pdf

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are getting higher and higher. The Zagros mountain range, itself, has a totally sedimentary origin and is made primarily of

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is characterized by marine transgression, particularly in Alborz, that extends into Lower Carboniferous. With exception of

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dolomites in Central Iran. A continuous Permian–Triassic sequence has been reported from several areas in Iran, including

191:. They were submerged, moved northwards, and were finally attached to the Eurasian section of the northern supercontinent 2561: 480:

limestone and other Paleozoic sedimentary rocks. Flysch Zone (Zabol–Baluch) is located between Lut Block to the west and

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of Middle and Late Cambrian age. In some areas, the Late Cambrian carbonate facies turns transitionally into Ordovician

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rocks in the southeastern parts. The mountains were mainly formed in the Miocene during the Alpine orogeny. As the

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is characterized by uplift and regression; however, a renewed progression at this time led to the deposition of

1581:, Shanderman, and Asalem. These rocks display many typical features of modern ophiolites. Ophiolite series of 835:

is documented by the widespread Doran Granite, which cuts the Upper Precambrian rocks and is covered by Lower

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GEOLOGICAL SURVEY OF IRAN - Manuel berberian, www.manuelberberian.com/Berberian%201976%20-%20Report%2039.pdf.

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GEOLOGICAL SURVEY OF IRAN - Manuel berberian, www.manuelberberian.com/Berberian%201976%20-%20Report%2039.pdf.

1833:, folding, faulting, creation of new basins, and facies change. This event was associated with compressional 2396: 1589:

age show typical features of ophiolitic sequences and are thought to be associated with the closure of the

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Magmatic rocks of this time have been reported from many areas in Iran. Examples include basaltic rocks of

1965:. The northern movement and the final collision of Afro-Arabia (significantly the Arabian Plate) with the 2642: 284: 2601: 2506: 1445:. Data from various structural zones indicate that the volcanic and plutonic activities started in the 2706: 2611: 2328: 2304: 1465:(or Urumiyeh-Dokhtar) volcanic-plutonic belt with a series of famous mountain ranges including the 1385:: Many intrusive bodies of mafic to granitic composition, with ages varying from early Triassic to 843:, rhyolite tuff and basic dikes are known in the Eocambrian formations. In North and Central Iran, 2556: 2521: 2476: 1577:

of Upper Paleozoic occur as metamorphosed as well as non-metamorphosed bodies in some areas like

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and the Southern Azerbaijan is comparable with Central Iran and Western Iran and extends to the

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the northern Paleo-Tethyan affinity of the foraminiferal associations in the late Viséan-late

1593:. These ophiolite series are widespread in Iran. Some of the more important locations include 2566: 2541: 2456: 2436: 2386: 2356: 2346: 378: 2652: 2531: 2526: 2406: 1457:. Some of the more important regions in terms of the Tertiary magmatic activities include: 8: 2626: 2596: 2546: 2501: 2481: 2471: 2371: 2297: 1689: 1683: 1662: 896: 1973:

towards the Iranian Plate caused the Alpine orogeny with the Pyrenean phase in the Late

931:, consisting of limestone, dolomite, and shale, over older units. These formations bear 2571: 2486: 2466: 2351: 2341: 1732: 1726: 1700:, folding, and faulting during Late Precambrian–Early Cambrian in Iran (e.g., south of 1666: 1622: 1518: 1200: 1059: 971: 781: 533: 275:

rocks about 8-10 kilometres in thickness has undergone folding from the Miocene to the

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is equivalent to Asynitic in other parts of the earth. This event was associated with

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is of great concern in Iran because of the great volumes and highly diverse types of

1361: 1299: 765: 680:) rocks, while the western part of the Eastern Alborz Range is made primarily of the 626: 520:

sediments; volcanic, volcanosedimentary, and intrusive rocks; and ophiolitic series.

1757: 1176:). A correlation exists between distribution of magmatic rocks and certain types of 2657: 2576: 2536: 2511: 2491: 2426: 2401: 2391: 2376: 2255: 1913: 1896: 1890: 1582: 1466: 1410: 1268: 1248: 1084: 797: 789: 710: 706: 382: 280: 85: 1036:

sediments in Iran are mainly of shallow marine or continental shelf nature (e.g.,

780:. According to the some authors, the northern part of Azerbaijan continues to the 18: 2496: 2461: 2416: 2320: 1900: 1731:

There was no considerable folding or faulting related to this event in Iran. The

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under the continental lithosphere (e.g., Central Alborz for continental rifting;

1044: 995:, Zagros); however, they seem to be missing in Alborz and parts of Zagros. Upper 860: 585: 300: 204: 1761:

Late Carboniferous paleogeography (about 320 Ma) with the Paleo-Tethys indicated

548:. The northern part is characterized by dominance of east–west trending faults, 2283: 2246: 2038: 2030: 1982: 1970: 1962: 1933: 1542: 1482: 1382: 1128:). The Middle to Upper Miocene sediments are mostly of continental nature. The 744: 631: 152: 609:

or basin from the Jurassic to the Miocene and formed the Kopet Dag Mountains.

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in age. The most remarkable occurrence of ophiolite could be observed in the

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and following this orogenic episode, shallow marine sediments formed in Late

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of this orogenic phase. With an elevation of 5,610 metres (18,410 ft),

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of Kolah Ghazi, Shir Kuh, and Shah Kuh was made during this orogenic phase.

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core. Continental conditions regarding sedimentation are reflected by thick

1943: 1921: 1826: 1701: 1693: 1618: 1506: 1430: 1406: 1304: 1121: 1070:(the continuation of the Taurus in Turkey), north of Kandovan and Southern 824: 806: 564:. The whole sequence is deformed prior to Early Miocene. Thick sequence of 541: 419: 236: 112: 2226: