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Stratigraphy

Precambrian

The consolidation of the Iranian basement by metamorphism, partial granitization and partly by intense folding took place in the Late Precambrian. This event has been attributed to the ‘Baikalian’ or Pan–African Orogeny 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 magmatism is documented by the widespread Doran Granite, which cuts the Upper Precambrian rocks and is covered by Lower Cambrian sediments. Late Precambrian postorogenic volcanics, mainly alkali rhyolite, rhyolite tuff and basic dikes are known in the Eocambrian formations. In North and Central Iran, Kahar and Gharehdash Formations and the lower half of the Soltanieh Formation are of Precambrian age. The oldest rocks in Iran belong to the Kushk Series consisting of clastic sediments, acidic volcanic, tuff, and carbonates (mainly dolomite). Other formations of Late Precambrian–Early Cambrian ages include Rizu volcanic-sedimentary Formation, Dezu and Tashk Formations, Aghda limestone, Kalmard Series, Shorm Beds, and Anarak metamorphic units. The sedimentary facies of Precambrian–Lower Cambrian rocks in Northern Iran is different from that of Central Iran.

Paleozoic

With the Pan-African orogeny and following this orogenic episode, shallow marine sediments formed in Late Vendian. 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 Paleozoic (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 Barut, Zaigoon, and Laloon Formations is very difficult to recognize in the field. Middle Cambrian is characterized by uplift and regression; however, a renewed progression at this time led to the deposition of Mila and Kuhbonan Formations, consisting of limestone, dolomite, and shale, over older units. These formations bear trilobites and brachiopods of Middle and Late Cambrian. In some areas, the Late Cambrian carbonate facies turns transitionally into Ordovician graptolite shales, known as Lashkarak Formation in Alborz, Shirgasht Formation in Central Iran and Ilbeyk and Zardkuh Formations in Zagros. In Kalmard area, Ordovician sediments are sitting on the Vendian sediments through an angular unconformity. In Late Ordovician, most parts of Iran were affected by epeirogenic movements; this coincides with Caledonian orogeny in Europe and some other parts of the earth. The epeirogeny caused a distinct hiatus at the Ordovician–Silurian boundary. Where present, the Silurian 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, Kerman, Zagros); however, they seem to be missing in Alborz and parts of Zagros. Upper Devonian is characterized by marine transgression, particularly in Alborz, that extends into Lower Carboniferous. With exception of Tabas area, no record of Middle Carboniferous 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, Permian marine transgression deposits cover most parts of Iran (e.g., Alborz, Zagros, Central Iran); The Permian sediments are represented by Dorood sandstones, Ruteh and Nesen limestones in Alborz.

Mesozoic

The Lower Triassic sediments in Iran are mainly of shallow marine or continental shelf nature (e.g., Doroud sandstones and Elika dolomites in Alborz, Sorkh shales and Shotori dolomites in Central Iran. A continuous Permian–Triassic sequence has been reported from several areas in Iran, including Jolfa (northwest of Iran), Abadeh (Southern Central Iran), and Southern Urumiyeh (the continuation of the Taurus in Turkey), north of Kandovan and Southern Amol. 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 Jurassic sediments have a detrital nature, consisting mainly of shale and sandstone with thicknesses varying from a few meters to more than 3,000 m. The presence of plant remains and coal beds suggest a continental or lagoon environment for the deposits. The Cretaceous deposits, characterized by diverse sedimentary facies, are widespread all over Iran. In Late Cretaceous, tectonic movements related to the Laramide orogeny affects most parts of Iran, leading to uplift, folding, and faulting. This is a prelude to significant developments in the geological evolution of Iran.

Cenozoic

In Iran the Cenozoic 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 Paleocene and Eocene strata; as is the case with Eocene and Oligocene (e.g., Central Iran). The Oligocene and Miocene stages are characterized by rapid subsidence, deposition, and facies changes in both marine and continental sedimentary basins (e.g., Mahneshan and Halab south of Zanjan). Oligocene sediments in most parts of Iran are of shallow marine character, turning into marine facies in Upper Oligocene through Lower Miocene (e.g., Qom). The Middle–Upper Miocene sediments are mostly of continental nature. The Quaternary is the prominent feature of the plains of Iran.

Geological and Structural Units

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 ophiolite–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 Precambrian time and a platform–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 Rodinia and Pannotia in the Neoproterozoic, and of Gondwana in the Paleozoic and Mesozoic. 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 Cambrian, Ordovician, Silurian and Devonian. These fragments were detached from Gondwana in the Carboniferous. They were submerged, moved northwards, and were finally attached to the Eurasian section of the northern supercontinent Laurasia in the Late Triassic. These fragments or microplates were fused together and made the Iranian Plate which was rejoined by Gondwanic Afro-Arabia in the Late Cretaceous. As Afro-Arabia moved northwards towards Eurasia, the Arabian Plate ultimately collided with the Iranian Plate in the Miocene. 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 Paleotethys. 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 Kopet Dagh Range.

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

Zagros

This zone extends from Bandar Abbas in the south to Kermanshah in the northwest and continues through to Iraq. 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 Paleozoic rocks. Structurally, it consists of large anticlines and small synclines and continuous marine sedimentation from the Carboniferous to the Miocene. On the whole, a sequence of Precambrian to Pliocene rocks about 8-10 kilometres in thickness has undergone folding from the Miocene to the Recent time in the Zagros Mountains. The Zagros fold and thrust belt was formed by the collision of two tectonic plates — the Iranian Plate and the Arabian Plate. This collision primarily happened during the Miocene and folded the entire rocks that had been deposited from the Carboniferous to the Miocene in the geosyncline 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 Iranian Plateau are getting higher and higher. The Zagros mountain range, itself, has a totally sedimentary origin and is made primarily of limestone. 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 Mesozoic rocks, a combination of Triassic and Jurassic rocks that are surrounded by Cretaceous 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 Tertiary rocks, with the Paleogene rocks south of the Cretaceous rocks and then the Neogene rocks south of the Paleogene rocks.

Sanandaj–Sirjan

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 Lake Orumiyeh, Gavkhouni 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 Paleozoic and Mesozoic 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 Sanandaj–Sirjan and Central Iran.

Sahand–Bazman Volcanic Belt

This volcanic belt, which is usually called the Central Iranian Range, 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 Upper Cretaceous to Recent time. The peak of this volcanism happened in the Eocene. The Sahand-Bazman 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.

Central Iran

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 Precambrian to Quaternary, and several episodes of orogeny, metamorphism, and magmatism 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 Nain–Baft Fault in the west and southwest and by the Harirud 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; Kerman-Tabas Block, Yazd Block and Anarak-Khur Block.

Eastern Iran

Eastern Iran can be divided into two parts: Lut Block and Flysch Zone (flysch 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 km in a north–south direction. It is bounded in the north by Dorooneh fault and in the south by Jazmurian depression. In the east, it is separated from Flysch Zone by the Nehbandan fault, whereas the western boundary with Central Iran is Nayband fault and Shotori Mountains. The oldest units include upper Precambrian Lower Cambrian schists overlain by Permian limestone and other Paleozoic sedimentary rocks. Flysch Zone (Zabol–Baluch) is located between Lut Block to the west and Helmand (in Afghanistan) 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 shales, radiolarite, and pelagic limestone and volcanic rocks such as basalt, spilitic basalt, diabase, andesite, dacite, rhyolite, 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: flyschoid sediments; volcanic, volcanosedimentary, and intrusive rocks; and ophiolitic series.

Southeastern Iran or Makran

Southeastern Iran or Makran zone is located to the south of Jazmurian depression. Its western boundary is Minab fault; to the south, it is restricted by the Gulf of Oman, and to the east, it extends into Pakistan. The northern part is characterized by dominance of east–west trending faults, Bashagard 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–Paleocene overlain by a thick sequence (about 5,000 m) of sandstone, shale, and marl. The whole sequence is deformed prior to Early Miocene. Thick sequence of Neogene rock units, in excess of 5,000 m, covers the older series.

Kopet Dagh

The northeastern active fold belt of Iran, the Kopet Dagh, 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 Triassic basic dikes. This basin was located in the northeastern Iran. From Middle Jurassic, 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 Jurassic to Miocene have ever been reported. 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 rocks in the southeastern parts. The mountains were mainly formed in the Miocene during the Alpine orogeny. As the Tethys Sea 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 had been deposited in this geosyncline or basin from the Jurassic to the Miocene and formed the Kopet Dag Mountains.

Alborz

The Alborz 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 Caspian Sea. Alborz is characterized by the dominance of platform-type sediments, including limestone, dolostone, 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 Binalud Mountains in the east, although the continuation of the Alborz, bear features comparable to those of Central Iran. The Alborz mountain range is only 60–۱۳۰ km wide and consists of sedimentary series dating from Upper Devonian to Oligocene, prevalently Jurassic limestone over a granite core. Continental conditions regarding sedimentation are reflected by thick Devonian sandstones and by Jurassic shales containing coal seams. Marine conditions are reflected by Carboniferous and Permian strata that are composed mainly of limestones. In the Eastern Alborz Range, the far eastern section is formed by the Mesozoic (chiefly Triassic and Jurassic) rocks, while the western part of the Eastern Alborz Range is made primarily of the Paleozoic rocks. The Precambrian rocks can be found chiefly south of the city of Gorgan 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 of Jurassic rocks. Very thick beds of the Tertiary (mostly of the Eocene) green volcanic tuffs and lavas 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 Talish Mountains is made mainly of the Upper Cretaceous 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 Tethys Sea 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 Paleozoic, Mesozoic, and Paleogene rocks, and the Cenozoic (chiefly the Eocene) volcanism to form the Alborz Mountains mainly in the Miocene. The Alpine orogeny 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 Miocene and the Pliocene epochs.

Azerbaijan

There is no agreement regarding the geological setting of Azerbaijan. 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 Alborz fault, in the west by Tabriz–Urumiyeh fault, and in the south by Semnan fault. According to the some authors, the northern part of Azerbaijan continues to the Caucasus Mountains in Caucasia and the Pontus Mountains in Turkey and the Southern Azerbaijan is comparable with Central Iran and Western Iran and extends to the Taurus Mountains in Turkey. The significant structural event occurring in Early Devonian 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 Zanjan 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 Carboniferous.

Pirzal Perched syncline

In the Kohgiluyeh and Boyer Ahmad province in the southwest of Iran, along the road of Dehdasht to Sarfariab city, when pass through the pirzal gorge, we enter to the plain between the two mountains “Siah” and “Mondon”. The two mountains, Siah and Mondon, are anticlines that extend along the northwest to the south-east. In the plain between the two anticlines, there is a beautiful perched syncline.

Syncline is a geologic feature like a “V” fold in layered sedimentary ground, which often occurs when the layers tend to go horizontally, but twisted by the tectonic forces. In analogy, an “anticline” is the convex opposite form, where the sedimentary layers form a dome, and a “monocline” is flat.

A “perched syncline”, or “perched synclinal”, differenciates itself by the fact it stands elevated from the surrounding terrain. Contrary to the monoclines, they form very characteristic mountains, looking like fortresses surrounded by walls.

In fact, a perched syncline is formed when the central layers of syncline (younger) have more resistance than the outer layers (older) against erosion. In this case, the outer stones are eroded and the strong rocks remains in the center. These strong rocks remain in the form of a ship stands elevated from the surrounding terrain and form a perched syncline.

In center of Pirzal perched syncline, thick to medium bedded limestone (Asmari formation – Oligomiocene in age) and on the sides, alternation of Marl and thin bedded limestone (Pabdeh formation – Eocene to Oligocene) have been outcropped. Over the time, marls have been eroded, and strong limestones remain in the center.

This beautiful photo was taken by M.S.Zangeneh looking northward.

Keywords: Iran , Kohgiluyeh , Zagros , Anticline , Syncline , Perched syncline , dehdasht , sarfaryab , geology , geotourism , asmari formation , pabdeh formation , mondon anticline , kuh e siah anticline , pirzal gorge , zamingasht

Abarkuh Sinkholes

The Sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes—for example, the chemical dissolution of carbonate rocks or suffusion processes. Sinkholes vary in size from 1 to 600 m both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.(wikipedia)

Abarkuh County in south-west of Yazd province in center of IRAN have faced with some sinkhole occurrences in recent years which have caused significant damages to agriculture lands and other infrastructures of villages in this area.

From 2000 to 2005 more than 30 sinkholes had happened near Faizabad village. According the geological map of this area, sinkholes have formed on quaternary layers with maximum 13.5 meters and minimum 0.5 meters deep.

Photo by: Siamak Mohammadi Sivandi

 

Keywords: Abarkuh , Geology , Geotourism , Iran , Quaternary , Sediment , sinkhole , underground water , zamingasht

Mila Formation in Central Alborz

The Mila Formation is one of the Cambrian formations in Alborz.  The Mila Formation has 5 measurable members in type section (Mila Kuh, Damghan City). This formation overlies conformably the Early Cambrian Lalun Formation and underlies disconformably the Early Devonian red conglomerates. But on the Chalus road in Central Alborz, four members of this formation are visible and measurable.

The first member is a white base quartzite (BQ), which in the past was a member of the lower formation (Lalun), but according to detailed studies, the boundary of this unit with underlying sandstone layers is considered to be discontinuous.

The Second member consist of Dolomite with interbedded of yellow Shale and Marl. Third member is well bedded Limestone with a few shale. Forth member is course grained glauconitic limestone. Fifth member consist of Siltstone, Sandstone, Glauconitic limestone and Marl.

In the Image, Mila formation outcrops in Chaloos road, near Hasanakdar Village. Because of the tectonic forces, the rocky layers are cut, broken, and displaced by faults.

The lower boundary of this formation with the Lalun Formation is para unconformity and indicated with the white quartzite layers. The upper boundary of this formation in this area is determined by the Hassanakdar fault and the outcrop of lava in the Geirud Formation. All the thickness of the Mila Formation (without quartzite) in the Karaj valley is 395 meters (Lorenz, 1964). In this region without the quartzite member, only three members of the Mila Formation have been identified.

In the photo, the formations of Lalun (La), Mila (Mi), Ruteh (Ru), Jeyrud (Je), Elika (El) and quartzite member of the Mila Formation (BQ) are seen.

Keywords: Iran , Central Alborz , Geology , Geotourism , formation , Mila , ruteh , jeyrud , elika , chaloos road , limestone , sandstone , siltstone , dolomite , shale , marl , zamingasht

Star Valley

The Star Valley, which is called “Estareh Kafteh” in local dialect, is one of the most important erosional phenomena in Iran. this valley is located in south east of Qeshm Island in Persian Gulf. In this valley there is variety of geomorphological phenomena which shaped several interconnected branches of small valleys.

Besides the mechanical erosion of water which is the main factor of shaping this area, there are many other factors such as different types of rocks with different resistance, the intercalation of gypsum and the different regional tectonic activities.

The walls of the valley are formed by two types of layer: the thick and soft layer in bottom and the thin and hard layer on top. As the top layer has calcareous cement, is more resistance than the loose lower one; so it acts as the protector. Therefor where ever the top layer was destroyed or has some joints, erosion effects quickly and it causes the small valley’s forming.

Referring to the mentioned causes; the layers of this valley are so brittle, so even the weight of just one person can be dangerous and causes collapsing. Although the upper layer may seems to be strong, but the lower layers may has been destroyed due to erosion.

The Mishan formation is the main formation of the Star Valley. In Qeshm Island this formation includes the alternation of marl and silty marl in olive green to grey color with some lenses of intra formation conglomerate which intercalates with sandstones.

The age of formation in star valley back to Middle or late Miocene (5 to 10 million years ago), but the phenomena relates to several thousand years ago.

In sedimentary sequences of Mishan formation, there is variety of structures such as thin – middle – thick and massive layering, fossiliferous limestone and sandstone in the channel shapes, graded bedding, plane lamination, lens form lamination and other structures can be found.

From the structural geology point of view, the layers in the Star Valley have low dip or they are horizontal. Due to tectonic activites in Mishan formation, the systematic joints have been created in this area. The gravity force and weathering and erosional phenomena are the main reason of joints opening.

In local ancient’s belief, this valley has been formed by impact a meteorite and rising up of stones and soils and freezing there. On the other hand, they believed this valley was the resort goblins and the voice of howling the wind was because of their movements.

Keywords: Erosion , Geo site , Geology , Geotourism , Iran , Limestone , Marl , Mishan formation , Persian gulf , Qeshm Island , Sandstone , Star Valley

Asmari formation

The Oligocene–Miocene Asmari Formation of the Zagros Basin is a thick sequence of shallow water carbonate. Asmari formation is the youngest and most important reservoir rock of the zagros Basin in the south-west of Iran.

The Asmari formation has been divided into two members: one is the Sandstone Member of Ahwaz in the south-west of the Khuzestan area and the other one is the Evaporate Member of Kalhor in the Lorestan Province. This formation is divided into three units: the lower Asmari with an Oligocene age, the Middle Asmari with an Aquitanian age, and Upper Asmari with a Burdigalian age. However, these divisions do not exist everywhere.

Also, in some parts of Iran, the lower boundary of Asmari formation is in contact with the Pabdeh Shale formation which is of Paleocene-Oligocene age, but in central Lorestan this formation is overlying the Late Eocene Shahbazan formation and in internal Fars it show a paraconformable contact with the Jahrum formation (Eocene).

The Asmari formation is covered by anhydrites of the Gachsaran formation which is of Early Miocene age, and in internal Fars the upper boundary of Asmari formation is in contact with the Early Miocene Razak formation.

The photo shows the Asmari limestone formation (As) and Gachsaran formation (Gs) Along the shore of Karun 4 Lake Dam near Lordegan city in Chahar mahal va bakhtiyari Province.

Keywords: Asmari formation , Bakhtiyari formation , Gachsaran formation , Geotourism , Iran , Iran Geology , Iran Geotourism , Pabdeh formation , Zagros Mountain , zamingasht

Badab-e Surt

Badab Soort (Persian: باداب سورت‎‎) is a natural site in Mazandaran Province in northern Iran, 95 kilometres south of the city of Sari, and 7 kilometres west of Orost village. It comprises a range of stepped travertine terrace formations that has been created over thousands of years as flowing water from two mineral hot springs cooled and deposited carbonate minerals on the mountainside.

Badab is a Persian compound of Bād “gas” + āb “water”, translating to “gassed water”, referring to the springs’ waters being carbonated mineral waters. Soort is an old name for the Orost village and a Persian word meaning intensity.

Badab Soort’s springs are two distinct mineral springs with different natural characteristics, located at 1,840 metres above sea level. The first spring contains very salty water that gathers in a small natural pool; its water is considered to have medicinal properties, especially as a cure for rheumatism and some types of skin diseases and skin conditions. The second spring has a sour taste and is predominately orange mainly due to the large iron oxide sediments at its outlet.

badab02-zg

Badab Soort’s terraces are made of travertine, a sedimentary rock deposited by flowing water from the two distinct mineral springs; they were formed during Pleistocene and Pliocene geological periods. When the water, supersaturated with calcium carbonate and iron carbonate, reaches the surface, carbon dioxide degases from it, and mineral carbonates are deposited. The depositing continues until the carbon dioxide in the water balances the carbon dioxide in the air. Iron carbonate and calcium carbonate are deposited by the water as soft jellies, but they eventually harden into travertine.

badab01-zg

As a result, over the course of thousands of years the water from these two springs emanating from the mountain range have combined and resulted in a number of orange-, red- and yellow-colored pools shaped as a naturally formed staircase. The surrounding vegetation to the north consists of pine forests while to the east it mainly consists of short trees and shrubs; and rock quarries can be seen to the west of the site.

Photos taken by M.S.Mirkazemian.

جزیره قشم

Qeshm Island

Qeshm is the largest island in the Persian Gulf, with rocky coastlines that protects a mountainous and often beautiful interior. Qeshm Island is located a few kilometers off the southern coast of Iran (Persian Gulf), opposite the port cities of Bandar Abbas and Bandar Khamir. Qeshm has about 60 villages which are dotted mostly by coasts .Qeshm was always a high rated area because of its strategic location. The people there has a mixture of cultures which is good to mention you will be able to see the history through the left cultures. Historical records concerning the Qeshm island date far back into the pre-Islamic era. Names as Qeshm, Kish and Tunb mark the lengthy stay of Ilamids in the area, several centuries BC.

The island has an abundance of wildlife, including birds, reptiles, dolphins and turtles. Local communities are heavily involved in projects to protect the environment, and there is some disquiet about the effect that the country’s first heavy oil refinery, currently being constructed on the island’s southern coast, might have on the hitherto pristine natural landscape. Construction of the refinery is scheduled for completion in 2013.

Qeshm is also a supposed site of the Garden of Eden according to Cassells Bible.

Fishing is a leading occupation practiced by the inhabitants of the island. On what little cultivated land there is, dates andmelons are grown. Salt is mined on the southeastern coast. Qeshm is famous for its wide range of ecotourist attractions such as the Hara marine forests. According to environmentalists, about 1.5% of the world birds and 25% of Iran’s native birds annually migrate to the forests, which are the first national geo park in Iran. The language in Qeshm is localized Persian with a mixture of Arabic, Indian, Portuguese and English which are added through different chapters of time.

Based on similarities between Qeshm Islands’ anticlines and Zagros anticlines, it is assumed that Qeshm Island could be part of southern Zagros. Another determining factor would be the Salt Dome which has been pulling up on the western part of the island causing morphologic and tectonic changes. Finally, erosion which is mainly caused by wind, sea waves, and seasonal rainstorms, could be considered as a determining factor in forming the present geomorphology of Qeshm Island. Based on abundant natural resources and unique landscapes, especially exceptional geological formations, the Qeshm Global Geopark was established in the Western part of Qeshm Island. Qeshm Geopark as the only Geopark in the Middle-East has been registered by the Global Network of Geoparks

(GGN) in Paris, on 21st March 2006. As of October 2010, 77 Geoparks in 25 Member States had joined GGN, assisted by UNESCO. Obviously, Qeshm Geopark is of high importance due to its strategic location in the Persian Gulf, representing a region between East Asian and European Geoparks. In terms of geological diversity as well as variety of its sites, the Qeshm Geopark enjoys from an ecological and cultural diversity.

Some of important Geosites in this Island as follows:

Stars Valley:

Located near Berkeh Khalaf Village, not far from the Town of Qeshm, the Star Valley is at present the most visited among all Geosites. The Star Valley is a unique example among all Geosites to study erosion. The local name for this area is “Estalah-kaftah” which means “the Fallen Star”. The reason for naming this area as such is that the locals believe that once upon a time a star (commit) (meteor) has hit the earth at this site and as a result of this collision, the stones and soil have been thrown in the air and been frozen, forming these geological structures. There are also local beliefs regarding the presence of Ghosts and “Jinns” in this Valley during the dark which may be due to the unusual geological forms and wind blowing into the Valley at night. The geological morphology of this site is the result of erosion by rainstorms, wind and gravity on various layers. In areas where the geological structures are more resistant to erosion, they have remained intact, however in areas with softer geological structures, erosion has altogether degraded and vanished those parts. In the walls of this Valley, one can observe two different types of layers: A thick and soft layer of light color (beige or light grey) underneath a thinner layer of harder nature, in white or dark grey. The bottom layer due to its soft structure usually gets eroded while the layer above because of having some kind of natural cement (limestone), is more resistant to erosion, protecting the whole structure. In areas where the upper layer is eroded, smaller canyon-like structures have been formed. In some areas within this Valley, geological structure in form of “Pillars” columns may be observed,some of which are needle-shaped. One of the factors which have caused these structures is rainstorm water that is in general seasonal, washing away in circles the soft parts of the geological structure, leaving the harder parts intact as pillars columns or needle shapes. The remnant of hard structures sometimes are “Hat-like” cap rock which almost protects the pillar column from further erosion, while the rest of the structure has been already eroded and disappeared. Various layers in this Valley are thus very vulnerable and fragile, some of them may not even tolerate the weight of a human being. Thus stepping on geological structures could be very dangerous as they might fall apart. Despite a harmonious strong appearance, some areas are critically soft and vulnerable as the bottom layers have already been emptied by erosion. Please note that although by stepping on these structures they do not fall apart right away, the upper layers may get thinner and more fragile by trembling and as a result of narrow cracks these geological structures may get degraded more easily in the future. Thus, avoiding to walk on top of the structures overlooking the Valley may help in protecting this geological heritage for future generations to observe.

Roof of Qeshm:

The Roof of Qeshm is one of the main attractions among all Geosites. It is a semi-high plateau that is located in the central parts of the island, continuing into the western parts of the island and overlooking the northern coastline. It is called the Roof of Qeshm because it is the largest and highest plateau in the island and offers a unique opportunity for visitors to observe the beautiful landscapes from above. The Roof of Qeshm overlooks the Tandis Valley from the north, where its beautiful geomorphology may be observed. The top layers at the Roof of Qeshm are formed from hard structures (mainly limestone) covered by numerous fossils (mainly bivalves), while in its peripheral sections, presence of silt and marl as well as sand, has resulted in heavy erosion. A good way to access this Geosite is to travel through Tabl-Salakh road which through a gravel road and ١۵ minute hike could lead to the Roof of Qeshm. When arrived at the main plateau, the remnants of an ancient village (Kalat-Koshtaran) may be observed where relics of walls, “Aghols” and “Anbars” still remain. In addition, pieces of pottery that probably date back to the Islamic period may be found among the ruins. It is worth noting that limestone was used in forming these manmade structures which has probably been extracted from the upper layers of the plateau. The presence of a traditional water reservoir (Ab-anbar) with a roof shows that in recent years the villagers (from Table and Salakh) may have been using the area more as a picnic ground during the hot season. The Roof of Qeshm offers a unique opportunity to observe beautiful landscapes of the northern coastline, the Harra Mangrove forest, and the azure blue waters of the Persian Gulf as well as the mainland, encouraging the visitor to take a moment to think and breathe in fresh air, and enjoy the clear skies, also suitable for astronomy.

Tandis ha Valley:

This Valley is located south of the Harra Forest. It is known for its beautiful geological structures that represent a highland that has been heavily eroded. In fact, the Tandis Valley is remnant of a high plateau that has been once connected to the Roof of Qeshm. As the island has risen and the seawater has retrieved gradually, the surface area of the island has increased. The Tandis Valley is part of those areas which have been once underneath the water, and when pulled up, it has been heavily eroded by sea waves among other factors. This type of erosion gets reduced gradually while moving more towards the Roof of Qeshm, which has remained intact. In the Tandis Valley, similarly to other geosites, whenever the upper and harder structures (mainly limestone) that usually protect the softer layers beneath, have been degraded, erosion has been a determining factor in forming the geomorphology. However, if these harder structures remain, softer ones are also protected. This is the main reason high plateaus are observed among lower and heavily eroded lands in Qeshm Island.
At this geosite, interesting forms may be observed as if nature has been powerfully carving them through ages.

In some areas of the Valley numerous fossils may be found including fossils of bivalves, in some areas as colonies. Another interesting geological phenomena in the Tandis Valley is sedimentation forming muddy mud cracks, which has created beautiful and interesting landscapes. During and after the rainfall, it is important to pay attention to muddy areas where sometimes the mud is very sticky and dangerous to walk on at this geosite.

Chahkuh gorge:

Chahkuh gorge is on the north-western part of the island not far from Table Village. This Geosite is an exceptional example of erosion through rainstorm water. Heavy rainstorms (that are also rare) quickly flush water through geological structures. Erosion however has been a secondary factor in forming this beautiful valley In fact, it has primarily been affected by the Salt Dome and related anticline. An anticline is a fold that is convex up and formed
due to tectonic compression. While under pressure, these arch-like structures may break in areas that are weaker, forming grooves on the walls. Chahkuh has been initially formed by these geological phenomena, and secondarily been washed away by erosion. Vertical to the main valley axis, there is a second valley, which has also been formed through tectonic pressures. In general, anticlines and areas around them could be counted as «unstable”
as they are more or less exposed to tectonic pressures and compression causing numerous joints and faults in formations.
The presence of concave and round structures or linear and oval structures on the walls of the valley is the result of erosion by water. One of the main characteristics of geological formation of this geosite is its impermeability to water, which keeps the water in holes and grooves, causing further erosion. The locals have taken advantage of this structure by digging wells inside the main axis of the valley to act as water reservoirs. Considering the low level of rainfall on the island, and the scarcity of freshwater, this was a very innovative way to gather water from rainstorms and use it during dry seasons. Chahkuh is aesthetically very attractive, and it is very important to warn the visitors against writing any graffiti on its walls.

Namakdan complex:

The Salt Dome is located on the south western part of Qeshm of island, and hosts the longest salt cave of the world (Namakdan Cave) that is 6km in length.Salt domes are formed when a huge amount of salt moves towards the earth’s surface due to its light structure compared to its surrounding structures. Salt domes emerge in areas which have weak surface structures and openings, and appear as Salt domeon the earth surface.
The Salt domes have many interesting aspects such as salt falls, salt springs and salt caves, with various geological formationsthat have been prone to erosion and dissolution processes.Rainwater gradually penetrates the Salt Dome through its crevices, allowing the water dissolve the salt and enter the dome. Similarto other calcareous caves of the world, the formation of the Salt Cave has been following a Karst-like mechanism, by which waterpenetrating through a joint may gradually dissolve the surrounding areas, forming open and large cave-like structures.As the dissolution process is not the same for all areas, size and shape of these caves and openings differ, giving rise to largeand open spaces in some areas, while in other areas very narrow corridors are formed where one only can get through the caveby crawling.
Some of the most amazing structures that may be found inside the Salt Cave are Stalactites and Stalagmites, as well as saltcrystals (such as needle-shaped, round, or multi-facet) formed by sedimentation of salt. In addition, in some areas where waterhas penetrated to the ground, some beautiful ponds have been formed with salt crystals at the bottom.One of the main attractions around the Salt Dome and the Salt Cave, are geological structures that are composed of various layersof colorful minerals and stones. These are indeed gifts from the depths of the earth which have been brought to the surface throughthe rise of the Salt dome. The age difference between these minerals andother geological structures on the island is over millions of years, anddifferent color in minerals represent different chemical elements. Forexample, the red color represents the Iron, and the yellow color reflectsthe presence of Sulfur.
Another interesting phenomena around the Salt Dome, is the presenceof very shiny and silvery particles, reflecting the presence of Oligist (atype of Iron oxide )that may be observed on the sandy beaches, creatinga beautiful landscape. These are the remains of large Oligists that havebroken down and eroded, and widely distributed. Oligists and other Ironoxides may be found in abundance around Salt domes.While visiting the Salt Dome and the Salt Cave, one has to be extremelycautious not to fall, as there are many holes that have been formed bydissolution process and are sometime hidden and covered by a thin layerof salt, which is hard to distinguish at first sight.
It is important to note that this geosite is very vulnerable to visitation,as the Salt Dome and the Salt Cave and their related structures havetaken thousands of years to form. Each piece of salt crystal that has beenformed inside the Salt Dome and Salt Cave, if damaged, needs anotherhundreds of years to be formed. Therefore, extreme caution by visitors ishighly required and advised to protect and conserve this unique geositefor the next generations.

Naaz Island:

Naz Island in Qeshm is set to emerge as one of the important tourist destinations in Iran. The island is located almost one km to the east of Qeshm and expands over three hectares but lacks sandy coasts. It is surrounded by cliffs rising close to 10 meters. The island is totally flat and when there is a low tide, a narrow patch of land connects Naz to Qeshm Island. Presently there are no dwellers on the island and local fishermen have built arbors there as temporary resting places.

Hara Mangrove forests:

Mangrove forests are unique wetland ecosystems that are established directly in theintertidal zone. Mangrove forests of southern Iran mainly consist of Avicennia marina, aspecies that was named after the great Iranian scientist, Avicennia (or Abu-Ali Sina). The Harra forestconstitutes the most western limits of the mangrove forests of south-east Asia. Harra Protected Areais located in the Khuran Straits, between Qeshm Island and mainland (Khamir Port), consisting ofmangrove forests that have grown more or less densely in the wet and muddy areas of this intertidalwetland. Daily tidal change is the main determining factor in forming the Harra ecosystem. Althoughthe Harra forest is quite homogenous in its composition, with low diversity of plant species, it ishome to a very diverse fauna. This Protected Area is also on the list of Internationally ImportantWetlands (Ramsar Convention).

The Unique Ecosystem of Harra

The Harra forest is a mangrove forest that is only found in coastal areas in tropical regions. Athigh tide, the tree coverage may only be seen above the water level (salt water), while the rest ofthe tree parts are underneath the water. Only at low tide, one can see the trunk and aerial roots ofmangroves. Mangrove forests can easily grow in salt water. Mangroves may have been floweringplants that were pushed to their limits due to lack of capacity in competing with other terrestrialplants. They have then adapted to the difficult conditions of the intertidal zone, which has formedthis unique ecosystem.

High and low-tide in Mangroves

High and low-tide have been critical in shaping the mangrove forests and its related biodiversity.Mangrove forests host a variety of water birds,which, at low tide feed on the muddy intertidalzone. In fact, each bird species is well adaptedto feed on very specific organisms that live atcertain depths in salt water or the mud.

Fighting salinity

In general mangroves can’t use sea water,because the salt that enters the plant throughthe sea water, after evaporation of water fromthe surface of the leaf , will form a salt solutionin the leafs. To address this issue, the rootsof mangroves act as a goal-oriented filter, andallow distilled water to pass through them,preventing the salt to enter. Only minimallevels of salt that are necessary for normal cellfunctions may enter the plant and get stockedin the leaf cells. Leafs with too much salt fall,and in this way, the salt is eliminated. Anothermechanism to eliminate the salt is the glandsthat are located underneath the leafs.

Reference: Qeshm Island Geopark

Oligocene red deposits

After Pyrenean orogeny, central of Iran was under the influence of weathering and erosion. Caused materials were deposited in alluvial environments, floodplains or temporary tropical lakes.
These deposits are located between the upper Eocene rocks (mostly pyroclastic and igneous rocks) and Late Oligocene in “Central Iran” (one of the tectonostratigraphy state of Iran plateau) as “Lower red formation” are known.
The “Lower red” was first proposed by Ganser for the red deposits between Eocene volcano-sedimentary rocks and Oligocene-Miocene marine layers (Qom formation) in 1955.
This formation represents the red Oligocene continental deposits in west of Central Iran, particularly are widespread in Qom, Tafresh, southeast of Tehran, north of Garmsar and north of Semnan .
The picture was taken from Lower red formation near Ghezeljeh village in the 20 kilometers northwest of the Tafresh. In this area, the alternation of red sandy marl and conglomerates with intercalations of green and gray sandstone are deposited that called Lower red formation.

Oligomiocene sandstone was located on the Lower red formation with unconformity.