Were the Tehran faults formed as a result of the movement of the Caspian Sea plate towards the Alborz Mountains?

The seismically active Alborz mountains of northern Iran are an integral part of the Arabia-Eurasia collision. Linked strike-slip and thrust/reverse-fault systems in this mountain belt are characterized by slow loading rates, and large earthquakes are highly disparate in space and time. Similar to other intracontinental deformation zones such a pattern of tectonic activity is still insufficiently understood, because recurrence intervals between seismic events may be on the order of thousands of years, and are thus beyond the resolution of short term measurements based on GPS or instrumentally recorded seismicity. This study bridges the gap of deformation processes on different time scales. In particular, my investigation focuses on deformation on the Quaternary time scale, beyond present-day deformation rates, and it uses present-day and paleotectonic characteristics to model fault behavior. The study includes data based on structural and geomorphic mapping, faultkinematic analysis, DEM-based morphometry, and numerical fault-interaction modeling. In order to better understand the long- to short term behavior of such complex fault systems, I used geomorphic surfaces as strain markers and dated fluvial and alluvial surfaces using terrestrial cosmogenic nuclides (TCN, 10Be, 26Al, 36Cl) and optically stimulated luminescence (OSL). My investigation focuses on the seismically active Mosha-Fasham fault (MFF) and the seismically virtually inactive North Tehran Thrust (NTT), adjacent to the Tehran metropolitan area. Fault-kinematic data reveal an early mechanical linkage of the NTT and MFF during an earlier dextral transpressional stage, when the shortening direction was oriented northwest. This regime was superseded by Pliocene to Recent NE-oriented shortening, which caused thrusting and sinistral strike-slip faulting. In the course of this kinematic changeover, the NTT and MFF were reactivated and incorporated into a nascent transpressional duplex, which has significantly affected landscape evolution in this part of the range. Two of three distinctive features which characterize topography and relief in the study area can be directly related to their location inside the duplex array and are thus linked to interaction between eastern MFF and NTT, and between western MFF and Taleghan fault, respectively. To account for inferred inherited topography from the previous dextral-transpression regime, a new concept of tectonic landscape characterization has been used. Accordingly, I define simple landscapes as those environments, which have developed during the influence of a sustained tectonic regime. In contrast, composite landscapes contain topographic elements inherited from previous tectonic conditions that are inconsistent with the regional present-day stress field and kinematic style. Using numerical fault-interaction modeling with different tectonic boundary conditions, I calculated synoptic snapshots of artificial topography to compare it with the real topographic metrics. However, in the Alborz mountains, E-W faults are favorably oriented to accommodate the entire range of NW- to NE-directed compression. These faults show the highest total displacement which might indicate sustained faulting under changing boundary conditions. In contrast to the fault system within and at the flanks of the Alborz mountains, Quaternary deformation in the adjacent Tehran plain is characterized by oblique motion and thrust and strike-slip fault systems. In this morphotectonic province fault-propagation folding along major faults, limited strike-slip motion, and en-échelon arrays of second-order upper plate thrusts are typical. While the Tehran plain is characterized by young deformation phenomena, the majority of faulting took place in the early stages of the Quaternary and during late Pliocene time. TCN-dating, which was performed for the first time on geomorphic surfaces in the Tehran plain, revealed that the oldest two phases of alluviation (units A and B) must be older than late Pleistocene. While urban development in Tehran increasingly covers and obliterates the active fault traces, the present-day kinematic style, the vestiges of formerly undeformed Quaternary landforms, and paleo earthquake indicators from the last millennia attest to the threat that these faults and their related structures pose for the megacity.

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Geometric-kinematic characteristics of the Khazar fault, roughly 600 km long along the North Alborz- South Caspian boundary, are investigated using field evidence and satellite images. The fault trace along the strike and the fault zone architecture has been determined. This study indicates the northern margin of the Alborz mountains is complicated by the presence of four main fault systems, the Khazar, Sari, North Alborz, and Langrud faults from the east to the west, respectively. The results of this study show the western termination of the Khazar fault in the eastern Alborz lies somewhere in the east of the Neka city (Longitude: ∼53°20ˈE), and where laterally juxtaposes to the North Alborz fault through Sari fault. According to the recent movement of the Khazar and North Alborz faults, an extensional area has been created along the Sari fault zone in the middle part of the northern Albors mountains. Moreover in the western Alborz, the Langrud fault and the western segment of the North Alborz fault have created a transpressional deformation zone. The collision of Iranian plateau with the South Caspian basin, in the late Miocene, has made curved shape of the eastern and western parts of the Alborz mountains that progressively wrapped it with anticlockwise and clockwise rotations, respectively. Geodetic rotation rates indicate the Alborz mountains currently have anticlockwise rotation since its amount decreases from east to west.

In this research, the interaction of strong mid-tropospheric vortices in the Caspian Sea with Alborz Mountains leading to formation of significant perturbations in the lee of Alborz Mountains is studied in two cases of 6th January and 3rd February 2008. In addition to the usual synoptic-dynamic analysis using the analyzed GFS data and various diagnostics including isentropic maps of potential vorticity, results from the numerical experiments using MM5 model are presented to uncover the extent and nature of the complex interaction between the vortices and the Alborz Mountains as well as their impact on weather in these cases.

In both cases, low-level flow blocking and positive pressure anomaly induced by Alborz Mountains can weaken the cyclonic vortice in the windward. The "frontal retardation" caused by Alborz Mountains is followed by pressure drop, enhanced baroclinicity, and formation of surface cyclone in the leeward side; the characteristics of the first phase of lee cyclogenesis.

In the case of 6th January, the interaction of surface cyclone and preexisting mid-tropospheric synoptic cyclone/ PV streamer in the leeward leads to deepening and extension of cyclone throughout the depth of troposphere: characteristics of the second phase of lee cyclogenesis. But in the case of 3rd February, orographic development is restricted to the lower levels. This may be due to the strong ridge development on the western Caspian Sea and rapid weakening of upper level through/ PV streamer in the lee of the Alborz Mountains.

The cases studies exhibit characteristics of "orographically modified cyclogenesis", not "orographically induced cyclogenesis"

Geologically, the Caspian Sea is located in the northern part of the Alpine-Himalayan belt. It is limited to the Alborz Trust Belt from the south, to the marginal mountains of Talesh from the west, and to Kopeh Dagh and Qaraqorum from the east. The Caspian Sea is divided into three parts: the northern part includes the ocean-like bedrock located on the Precambrian platform with north[1]south folds, the central part with Hersinian bedrock and NW-SE stretches and the southern part with basaltic bedrock. They are formed with a thickness of 15 to 20 km. The speed of P waves in the southern part varies between 6.6 to 7 km / s. This part is surrounded by granite crust. The thickness of the southern part varied between 15 and 25 km, which remained almost unchanged. Excavations indicate the thickness of sediments in this area, which can indicate the subsidence of the Caspian Sea along the Alborz or Caspian faults and Talesh or Astara faults. By examining the available geological, tectonic and geophysical data, the evolution of the Caspian region and the depression of the southern Caspian can be achieved. The initial Jurassic tensile phase resulted in the emergence of the Swan-Accra-Qara Dagh ocean in northern central Iran, which stretched between two European plates and a central Iranian plate. Subduction of the existing oceanic crust below the active edge of the Little North Caucasus has led to the formation of the Caucasus-Talesh and Western Alborz-type magmatic arcs and local tension in the southern Caspian region in the form of an arcuate opening with alkaline rift volcanism. According to the available evidence, it has become a depression at least since the Pliocene-Pleistocene south of the Caspian Sea by inverted major faults. In Plio-Pleistocene the extent of the Caspian Sea was very high and even included the Aral Sea. In pre-Pleistocene, the Aral Sea, the Black Sea, and the Caspian Sea formed a single sea, and this continued until the Quaternary glaciation. In the Middle Miocene, pressure from the Saudi plate closed the Black Sea to the Caspian Sea. The Caspian has undergone at least two tensile phases; One during the Mesozoic and the other in the Paleogene. This study tries to study the geology of the Caspian Sea and the water salinity crisis.Caspian. Sea. Orogeny. Tethys. Salt. Oceanic Crust. Subduction.

In Iranian geology, ophiolite is a collection of mafic and ultramafic rocks that may be regular and layered or mixed with each other due to tectonic stresses. Accompanying sedimentary rocks in deep areas is called "ophiolite complex" or "melange ophiolite". Iranian ophiolites are mostly in the form of narrow and more or less continuous bands that are often exposed along the main longitudinal faults. Geological evidence, especially the study of the chemistry of these assemblages in terms of isotopic ratios of Sr 86 / Sr 87 and the distribution of rare earth elements, indicates that their chemical composition is similar to that of oceanic rocks, so it is accepted that the assemblage Iranian ophiolites are the remnants of intercontinental derivations formed by rift and their escape, and during the movement of continents and subcontinents, are located in the location and along the land of ancient Paleotte seams. Phenomena such as rift of the shell and its escape due to the collision of the plates and the retention of these assemblies in the place of seams are the basis for the formation of these structures. Due to the tectonic and geological situation of Iran, the role of rift phenomenon is more. Although the type of magma formed in this system or the type of sediments along with the Iranian ophiolite series show differences and discrepancies with other ophiolite bands in the world, but in the eastern regions of Iran, the presence of destructive sediments such as flysch Silica shales, which are not compatible with the deep oceanic environment, are the reason why the ophiolite formation environment is close to the continental margin. Examination of the Iranian ophiolite bands shows that these assemblages formed during two separate phases. The first phase, an extension regime, created a deep rift in the earth's crust. These fissures, which extend to the asthenosphere, have been a good route for the placement of basaltic magmas. The second stage involves a compression phase that closes the initial rift, pushing ophiolite assemblages to the edge of adjacent continents. In this paper, we try to deal with the conditions of melange ophiolite formation in the west of Zarghan village, which is affected by the Zamand-Zarghan .

The Caspian Sea is the largest lake in the world, between latitudes 7 و and ˚47 to ΄33 and ˚36 and east longitude ́ 43 and ˚46 to ΄50 and 454. About 130 rivers discharge into the Caspian Sea, the most important of which is the Volga River, while the share of rivers in northern Iran in supplying water to the Caspian Sea has been very small. The water quality of the Caspian Sea changes significantly from north to south and from west to east, and its quality is constantly decreasing, the main reason being the main inflow of fresh water from the north, especially the Volga. According to the available evidence, at least since the Pliocene, the Pleistocene south of the Caspian Sea has been turned into a depression by the main inverted faults, and now this depression is characterized by a fall along the Caspian reverse fault in the south and the Absheron[1]Balkan fault in the north. . The Caspian is located in a place that has undergone at least two tensile phases. One is in the Mesozoic length, which is related to the formation of the Swan-Accra-Qara Dagh oceanic crust and the expansion of its arcuate basin, and the other in the Paleogene is associated with the formation of an arcuate basin with the Central Iranian igneous arc. This issue was due to the subduction of the Zagros oceanic crust. The chemical quality of Caspian Sea water in terms of chemical composition is magnesium, calcium and sulfate and its salinity varies between 3.7 to 18.5 grams per liter and its average is equal to 12.04 grams per liter, which is approximately ⅓ salinity ( Water-soluble salts are the water of the high seas and oceans (the average salinity of the waters of the seas and oceans is about 35 grams per liter). On the way to the south, the salinity is constantly increasing. This study tries to address the geological features of the Caspian Sea and its salinity crisis. The morphology of the Caspian Sea floor is heterogeneous in the three parts of north, center and south and is dominated by morphological anomalies. This morphology has caused the distribution and spread of sediments that enter the sea by erosion agents to be uncoordinated. Annually, about 90 million tons of sediment enters the Caspian Sea, which is mainly carried by rivers. These sediments are scattered in different parts of the sea depending on the grain size and carrying capacity of the submarine currents and waves. Clay is the main deposit of the Late Quaternary (Pliocene) time since the separation of this sea from the Black and Mediterranean Seas, which are located on the rocks of different geological periods with different thickness.

From the point of view of historical geomorphology, the Caspian Sea rocks are different in different parts of it. The bedrock, in parts of the northern part, is made of Siberian shield metamorphic rocks (Zankovich, 1956) and in parts of it, the semi[1]oceanic crust forms the Russian Precambrian continental platform (M. Berberian, 1982). The central part has a Hersinian rock with continental characteristics, the trend of which is northwest-southeast and is located on the Cambrian rock. The southern part, which is the most important part of the sea in terms of tectonics, has a basaltic bed with a thickness of 15 to 20 km, which is surrounded by granite crust (M. Berberian, 1982). He described the basalt rock as an elaborate oceanic crust rather than a major oceanic crust. The thickness of soft deposits in the Caspian Sea floor has been determined from 40 meters in the northern and central parts and up to about 1200 meters in the southern part (quoted by Russian experts, presented on the 50th anniversary of geophysical exploration for oil and gas in the Caspian Sea in Baku , 1991). Discussion Birth of Caspian (Oligomiocene -Paratethys) Rogel (1999) has extensively studied the Paratethys Basin. Based on stratigraphic and paleontological findings, from the confluence of basins, plains, and depressions from the "River Gene" in Western Europe to Asia. Central to the Miocene was the Paratethys Basin, which ranged from west to east, including the Gene River Basin, the Middle Danube Basin, the Pannonian Basin, and the Black Sea and Caspian Seas to the east, respectively. The tectonic implications of this vast continent are surrounded by sub-continents such as Iran, Anatolia, and Rhodope (Bulgaria). For this reason, the Southern Caspian Basin and the Black Sea have an oceanic crust on which smaller continents float. The closing of the Tethys Ocean occurred during the Late Eocene. At that time, two seas formed simultaneously in the western part of the ocean, including the Mediterranean Sea and the Eurasian sedimentary basins within Parattis, where the hydrocarbon territory of the southern Caspian basin was formed. The consequences of this event, changes in water depth, movement Parts of the crust, and the elevation of the marginal boundaries of Parattis, have created different geographical areas in this area.

At different time points, depending on the ancient geographical conditions, ridges, altitudes, waterways, and elevations in different parts of the basin and in the continental parts of the area are created and the face of the basin from the reconstruction of Cenozoic time fragments of the associated basin It is formed by large deformations in it. Among these major changes in the Parattis Basin is the formation of the Eocene during the Eocene during the Eocene with a north-southward trend (corresponding to the Urals) and the formation of the Caspian Basin with a decrease in salinity in the early Oligocene. There have been native and special creatures in it. From the Middle Oligocene with the reopening of the basin, maximum contact with the Indian Ocean was established during the "Late Oligocene and Early Miocene". Opening and closing of waterways and establishing and disconnecting intermittent communication between these affected areas and the expansion of native organisms in the basin are the characteristics of the Late Bordicalin and Middle Miocene. During the Middle Sarvalin, the last communication routes of Paratethys were cut off, and since the time of Sarmasin, the salinity of the water has decreased and the ecological conditions of the creatures in the basin have completely prevailed. The connection between the ocean waters of the "Pacific India" and the Mediterranean Sea has been established until the Late Burdical. (Figures 1, 2 and 3):

With the collision of Saudi Arabia and Anatolia during the Late Bordigalin period, only one bridge-like land remained for mammalian migration. By the time of Langin, the coast had receded to land, and finally by the time of Serravalin, the basin was completely closed (15 million years ago in the late Miocene, the Sarmasin Sea formed in part of the eastern and central Parattis area). It covers large areas from the Pannonian Plain and Pit to the Aral Sea, and may have extended as far as Central Asia. Although the Lower Sarmasin Sea has a salinity of about 20 grams per liter, which is slightly lower than the average of the high seas and oceans, it is comparable to the current salinity of the Black Sea, which houses the creatures and animals of ordinary marine environments Is. 11.5 million years ago, the Pannonian saltwater sea formed independently, and native organisms specific to southern waters of 12 to 15 grams per liter appeared very rapidly in this sea. After 1.5 million years, the salinity of the Upper Sarmasin Sea is slightly lower and in 10 million years ago it reached about 6 to 17 grams per liter, and the native organisms of the saline environments specific to this sea, which had a different animal species from the Pannonian Sea These environments are inhabited. About 5.8 million years ago, the upper Sarmasin Sea transformed into the "Miocene-specific sea" and its salinity was slightly reduced from 6 to 15 grams per liter. Decreasing water salinity has made the Sarmasin Sea creatures more specific. Shortly afterwards, about 7 million years ago, in the late Miocene, the Miocene Sea was replaced by the Poseidian Sea, and immediately the native creatures of the sea around it settled in abundance. The emergence of native organisms in this environment is not an independent process in this basin, but rather the connection with the "Pannonian" and "Aegean" basins has led to the unique creation of these creatures. The salinity of the Ponsin Sea is close to the salinity of the Miocene, with evidence of low[1]salt fluctuations in the range of 12 to 15 g / L. It should be noted that only a few representatives of the Miocene Sea have survived in the New Sea. This continuity of survival had nothing to do with the change in water salinity because the rate of salt change was not significant and it is thought that this continuity and survival of the offspring was likely due to the association with the Pannonian and Aegean basins. (Figure 4)

About 6 million years ago, the Pontic Sea was divided into the "Upper Pontic" and "Babajan" seas. First, the Black Sea or the Auxin Basin is formed, and then the southern Caspian basin is filled. High Pontic sea salinity remains in the range of 10 to 15 grams per liter, while drier climates have increased the amount of Babajan sea salt to more than 15 to 30 grams per liter. About 5 million years ago, on the Miocene[1]Pliocene boundary, the Pannonian Sea suddenly emptied into the Black Sea and possibly the Aegean Basin. Salinity lost 42 grams per liter of salt and was replaced by a freshwater environment that housed many native animal species. About a million years before the complete emptying of the Pannonian Sea, only the small, limited Balaton Sea remained, where all species of freshwater species have become extinct. At the same time, about 5 million years ago, the upper Pontic Sea became the Sea of Cimmerin, with a salinity of less than 5 to 12 grams per liter. Then, 3.5 million years ago, the Sea of Cimmerine was replaced by the Sea of Coyle Nietzsche or Agriss, which had almost the same salinity. About two million years ago, the "Gori" sea was replaced by less salinity, about 5 to 8 grams per liter. The sea is similar to the Pannonian Basin, but with a slower desalination process; For this reason, native animals of the brackish environment have been slowly replaced one by one and by other related species. About 5 million years ago and perhaps shortly before that, the very saline Balakhani Sea, which is the production sequence and reservoir rock of the Southern Caspian Basin, was formed. Such a high concentration of salt, estimated at more than 300 g / l, has been created under highly active evaporative and very dry environments (arid sandstones); The presence of highly saline organisms in the Balakhani reservoir proves this hypothesis. About three million years ago, the humid climate and the increase in the inflow of surface water into the Balakhani Sea led to the emergence of the brackish sea "Aq Chgil" with a salinity of 5 to 12 grams per liter and many native animals that had an unknown evolutionary process lived in it. Have found. The Aq Chgil Sea has been replaced in several stages in the Caspian Basin in succession by several water areas that more or less housed living organisms. Of these 5 water areas, 5 seas were more important. Apsheron Sea with a salinity of 5 to 12 grams per liter and similar to Aq Chgil has been formed in a period of less than about 2 million years ago. | About 7.1 million years ago, the Baku Sea replaced the Apsheron Sea, which again had the same salinity range. After that and about 400,000 years ago, the Caspian Basin was created with a salinity of 5 to 12 grams per liter. The Caspian Basin gave way to the Khawalin Sea about 100,000 years ago, which had a lower salinity in the range of 3 to 8 grams per liter, and finally the existing Caspian Sea, which is actually the current environment of the Caspian Sea, was formed. In fact, the sea began to form 500 to 700 years before the beginning of the Holocene. Geographical evolution, biodiversity and salinity of water.

The Caspian Sea is originally the largest lake on Earth, so called. It is unique in size and is even larger than the "Great American Seas" and the Victoria Sea in Africa. In addition to its size, this sea has other obvious differences with other seas. The water of the Caspian Sea is not sweet and is so-called "salty" and each liter of it has between 10 and 13 grams of salt, which is three times sweeter than the average of the world's open seas and oceans. Despite being less saline than the oceans, the water of the Caspian Sea is not suitable for drinking or agriculture. The main reason for this salinity difference is the separation of the Caspian Sea as a remnant of the old Tethys Sea. In fact, the Caspian Sea is a bay-shaped part and remnant of the Parattis Sea that has inherited some of the marine properties of this vast ocean; An ocean that has connected the Atlantic and Pacific Oceans in a vast canal since 60-50 million years ago. With the gradual movement of small and large continental platforms, the connection between the Atlantic and Pacific Oceans on either side of the Parattis gradually came to an end, and in the Pacific and Atlantic Oceans as independent waters, and the remnants of the Parattis each in the form of the Black Sea. The Mediterranean and the modern Caspian are derived from it. Accordingly, a significant portion of the salinity of the Caspian Sea is associated with this rift. After the formation of the Caspian Sea in the form of an independent water zone, the volume of water in the Caspian Sea, more than affecting the general salinity of the high seas, was affected by the formation of independent cycles from the catchment area of the surrounding rivers. Natural waters have flowed in this basin. Meanwhile, the eastern Caspian region, which has a warm and desert nature, is constantly extracting large volumes of salt from the Caspian Sea through the Nagorno-Karabakh system. The complex history of the Caspian Sea has also affected its inhabitants. From this perspective, the only place comparable to the Caspian Sea is Australia. In fact, both of these systems, at the time of their formation in the form of isolated and single climates, have their own exclusive conditions, which, by gaining independence from other interconnected climates, each have their own evolutionary process with the creation of animals. Very rare related to themselves. In fact, the separation of the two systems has provided independent habitats for the creation of rare and special organisms. Many zoologists consider the Australian continent and the Caspian Sea to be the habitat of living animal fossils. These two ecosystems have each gone through a unique and relevant bio-evolutionary process. Just as marsupials and ducks (Echidna and Ornithring) are specific to Australian habitats, the sturgeon and estrogen families are also found in the Caspian Sea, dating back 200 million years to the dinosaur age, despite the evolution of bony fish compared to They have been able to maintain their current form. Currently, more than 90% of the world's sturgeon and estrogen fish live in the Caspian Sea. In fact, it is the only Caspian Sea that has been able to provide suitable environmental conditions for this species of fish. In addition to estrogenic and sturgeon fish, many other animal species such as croutons and mollusks with their own unique characteristics live only in this sea.

Changes in salinity The salinity of the Caspian Sea water has not been uniform over time and due to the phenomenon and dry and wet intervals, this salinity has changed. In hot and dry climates, the rate of evaporation is more than the amount of precipitation and the amount of salt in the Caspian Sea leads to salinity, and in cold and rainy times, with the addition of fresh water, the salinity is less. It has been. Glacial processes have not been ineffective in this regard, and as the glaciers melt, the amount of fresh water entering the Caspian Sea increases, which reduces its salinity. In total, what has happened in the past has led to the current salinity of the Caspian Sea, which is three times lower than the average salinity of the world's oceans (35 g / L), about one-third. Salinity is the water of the oceans. The most important inorganic component of the Caspian Sea is the salinity of seawater. The average salinity of Caspian Sea water is 12.85 g / l. The waters of the three northern, central and southern parts, as well as the waters of the Gulf of Karabakh, each have different salinities. The lowest salt accumulation is in the waters of the Northern Caspian Sea. In the Northern Caspian, the average salinity of water is about 5 to 10 grams per liter; However, in certain areas near the delta of the Volga, Ural, and Turkic rivers, the salinity of the water affected by the large volume of fresh water entering is much lower and fluctuates in the range of 2 to 4 g / l. In the shallow areas of the east coast North Caspian, sometimes the salinity of seawater is very little above the average of 5 to 10 grams per liter. Occasionally, in some coastal bays of the North Caspian Sea, such as the "Mertoviti Koltok" and "Kadiak" areas, the salinity is more than 30 grams per liter. The salinity of the middle Caspian water is 12.7 g / l, which decreases in the Sulak River Delta. Due to the fact that no river enters the eastern part of the middle Caspian and the amount of rainfall is low and the amount of evaporation is high, the amount of salinity in the surface horizons of stagnant water sometimes reaches 13 to 13.5 grams per liter. The highest accumulation and concentration of salt in the Caspian Sea is related to the Gulf of Karabakh. The surface evaporation rate of salt in this pond is 1500 mm per year. The amount of rainfall in this area does not exceed 70 mm per year. Because of this, the bay acts like a huge evaporating pan in the Caspian Sea, sometimes bringing the salinity of the bay water to 300 to 350 grams per liter and even more. In this unique evaporative pan, the salts of "Mirabilite", "Astrakhanite" (sodium sulfates), and halite are constantly being produced. The water entering the bay can produce about 130 to 150 million tons of salt, which is about 10 times what all Caspian waters produce. For this reason, the Nagorno-Karabakh Gulf can be called the Caspian "desalination" system, which removes a huge amount of dissolved salt from the Caspian Sea from the water cycle. Without this bay, the amount of salt in the Caspian Sea would be much higher. In addition, large amounts of minerals have been deposited in the bottom of the bay by conventional evaporation or deposition. Based on what has been said and based on the salinity of the water mass, the Caspian Sea can be divided into three parts:

1- Water of "Caspian" North Caspian region

2- Water in the middle and southern part of "semi-saline"

3- Qara Baghaz Bay area "very salty"

Water Temperature The temperature change of the Caspian Sea is very different and unusual from place to place depending on the seasons and geographical location of the place. Overall, the Caspian Sea has a distinct continental climate. The water temperature in the south of the Caspian Sea does not reach less than 13 degrees Celsius in winter, and in summer it usually reaches above 25 degrees Celsius and even 30 degrees Celsius. Significant temperature changes in the Caspian Sea are usually specific to the Middle Caspian. In winter, the average temperature of surface water is only 6 degrees Celsius, while in mid-summer, the average sometimes reaches 25 degrees Celsius. Most of the seasonal temperature changes are related to the Northern Caspian. In winter, part of this zone is covered with ice and the water temperature reaches about zero degrees and below, while in mid-summer, the average temperature of sea water in this part is 24 degrees Celsius. In "calm waters" and in shallow bays, the water temperature sometimes reaches 35 degrees Celsius. Also, the water temperature in the shallow areas of the eastern sea, such as the Gulf of Qarabagh, can even reach more than 40 degrees Celsius. Contrary to the marked temperature changes observed in the surface water horizon of the Caspian Sea, the water bodies in the lower parts experience a constant temperature during winter and summer. In the northern Caspian, no definite and horizontal biological depths can be detected based on horizontal changes in water temperature, while in the Karabakh Gulf, "warm-blooded creatures" are visible in shallow areas. Therefore, each of the mentioned regions in the Caspian Sea has its own behavior depending on temperature changes. (Figure 5)

General Features of The Iranian Part of The Caspian Coast.

The southern shores and the Iranian part of the Caspian Sea have beaches with detrital grains that, unlike many common coastal platforms, do not have hardened floors and bedrock. From different geologists' point of view, different sedimentation rates have been reported for the Caspian Sea (between 0.1 and 4.5 mm per year). Thus, the Caspian Basin is known as one of the basins with very high sedimentation rates in the world. This high sedimentation rate causes the sediments to remain loose and unstable in the form of non-hydrated and hard, before leaving the water and without going through different stages of rocking to great depths. Excavation of sedimentary sequences in Sardar Jangal Square has shown that from the seabed, the sediments of "Ahd", "Neo-Caspian", Baku layers, and at least up to the lower part of the layers of Apsheron Formation (Pleistocene sedimentary sequences up to 2 million years ago) ), Sediments are completely "hard" and "not hardened". In general, the body of sediments excavated from light clay to light gray to dark shale, sometimes olive-colored, with sand particles (poor rounding and sorting) whose sand components are predominantly quartz, followed by feldspar. And juicy mica is formed with rare cement. This means that at least about 1000 m of this sedimentary sequence is loose, watery, unstable, and not hard. The short distance from the sedimentary origin of the Iranian Caspian coast, as well as the type of flow carrying these sediments, as well as the intermittent change of energy of the flow carrying incoming sediments in different seasons, which is the result of dry or "wet" condition of the catchment, In sedimentary deltas, the transported grains appear clumped, turbulent, or "poorly sorted." Also, due to the thinness of the shoreline and the ineffectiveness of the tidal phenomenon in the Caspian Sea (due to its closure, it is not possible to regularly granulate and sift particles in the shoreline area. Thus, the face of the southern Caspian coast is mainly affected by the regime of waves and currents, short-term and long-term catchment water level, physicochemical status, water temperature, and sediment type of detrital origin. The effects of past deltas and old coastlines along it have been observed on land today from 140 m above sea level and on the sea floor today up to 50 m above sea level (website of the National Institute of Oceanography and Atmospheric Sciences). Important elements that make up the Caspian Sea coast are primarily geological processes that have shaped the public appearance of the coast for the past two million years. River sediments, along with waves, and declining water levels are other factors shaping the Caspian coast. Many local rivers flow from the coast of Iran into the Caspian Sea, but Sefidrud and Gorganrud are the only rivers that currently form a delta inside the sea. The coasts of Iran are mainly sand that turns to rubble in the central parts and muddy shores in the eastern part. Typically, there are low-slope areas on the periphery of continents called the continental shelf. The continental shelf is, in fact, part of the "continental marine realm" which, with its low slope, is considered a land. sequel. This area of the coast is the site of sedimentation of nritic sediments that have been transported from the destructive origin of the basin, sediments of different materials and grains. Some scholars have attributed the continental shelf to the retreat of the coast (destroyed plateau) and others to the "continuous occupation of sediments in which the particles gradually become smaller towards the sea." In fact, the continental shelf is part of the land that has been submerged. Not only submarine river networks, but also the presence of karst and "lapis" grooves and channels in the erodible surfaces at the calcareous depths of these plateaus confirm that the continental shelf areas are part of the land. In situations where the performance of geological factors occurs over long periods of time and during this period the wave and current regime do not change significantly, the fluctuation of the Caspian Sea water level is the most important factor in the formation of the coast. Changes in the water level of the Caspian Sea change the level of wave and current performance and change the groundwater level, resulting in new morphological features in terms of sex and slope of the coast. The shores of the Caspian Sea can be divided into two general categories of deltaic coasts and non-deltaic coasts according to the type of dominant processes in it (marine processes such as water level, wave, current) and effective land (river) processes. Although on the Iranian Caspian coast, many local rivers flow into the sea and carry large amounts of water and sediment, but the only river that can form a large delta on this side is the Sefidrud River. Also, the eastern part of the Caspian Sea in the Turkmen region, with its arid climate, is now almost devoid of rivers and deltas. Fluctuations in the Caspian Sea water level at the geological scale have had major effects on the formation of deltas. As the water advanced, the old deltas were covered by the sea and the new deltas retreated to land. At the time of the retreat of the sea, the rivers were advancing into the sea by breaking the old deltaic sediments. The best condition for the development of large deltas is the water level stability of the basin. Large sedimentary loads have formed on the shores of the deltas during the relative stability of the Caspian Sea water level. The most important geological phenomenon of the Iranian coast is the existence of the Alborz mountain range that surrounds the Iranian coast and is distinguished from the coast by several large faults with a very high altitude difference. Based on the size of sediment particles, the coasts of Iran can be divided into three types of sandy coasts of Gilan and East Mazandaran, rubble (west of Mazandaran), and mud (Golestan). In proportion to the coastal sediments, with increasing depth, the bed sediments become finer, which depends on the slope of the bed, the energy of the waves, and the flow of river sediments. Therefore, the slope and extent of the shore on land are also different. In the western part of Gilan and Mazandaran, the coast is narrow and steep. Thus, in most of the shallow bed of the Iranian coast, sandy sediments are predominant and as a result of the action of the waves, the sediments move downstream and form underwater loads. In addition, the Caspian Sea coast is affected by wind patterns and water cycles under the influence of "parallel currents with the coast", which, along with other patterns of water movement, contribute to further erosion of the coast. The effect of clay minerals on the change of clay water concentration in sedimentological concepts refers to all sediment particles smaller than 4 microns in terms of size. Also, in terms of chemical composition, they are called aluminum silicates with sheet structure, which usually appear in small size in sediments. Clay minerals are hydrated aluminum silicates that consist of one of two basic quadrilateral silica and octahedral alumina base units. Each quadrilateral unit is composed of four oxygen atoms, which are called a silicon atom. Each quadrilateral unit is composed of four oxygen atoms, which are called a silicon atom. The combination of quadrilateral units is placed between the common quadrilaterals. Octagonal units consist of six hydroxyl atoms enclosing an aluminum atom. The combination of octagonal aluminum hydroxyl units produces an octagonal sheet. This sheet is also called Gibbsite sheet. Sometimes in octagonal units, the magnesium atom replaces the aluminum atom, in which case the octagonal sheet is called the brucite sheet. In a sheet of silica, each silicon atom with a positive capacity of four is bonded to four oxygen atoms with a negative total capacity of eight. But each oxygen atom is attached to a quadrilateral base with two silicon atoms. This means that the upper oxygen atom of each quadrilateral unit has a unit valence charge that is unbalanced and must be balanced. Hence, oxygen atoms replace hydroxyl to neutralize valent bonds. Unlike kaolinite, which has a hydrogen bond between its layers, in the crystal structure of Montmorillonites, an octahedral layer is trapped between two quadrilateral layers, and the only available force is the weak van der Waals forces. Therefore, when in contact with water, the crystalline structure of montmorillonites easily absorbs water molecules and swells up to six times their original volume. (Figure 6):

Clay particles carry a net negative charge on their surface. This phenomenon is due to both isomorphic substitution and failure of molecular structure cohesion at the edges. The larger the specific surface area of the clay mineral (surface area by mass), the larger the negative charge. Some positively charged areas may also be present at the edges. In dry clay, the negative charge effect is balanced by various cations such as the metal ions calcium, magnesium, sodium, and potassium, which surround the particles held by electrostatic attraction. When water is added to the clay, the above cations and a number of anions float around the clay particles. This phenomenon is called double scattering. In the double layer, the concentration of cations decreases with distance from the particle surface. Water molecules are polar; As a result, the water molecule acts like a rod with a positive charge at one end and a negative charge at the other. In the bilayer, water dipole molecules are absorbed by both the negative charge surface of the clay particles and the cations. Cations, in turn, are adsorbed by clay particles. The third mechanism by which water is adsorbed to clay particles is hydrogen bonding, in which the hydrogen atoms of the water molecule are adsorbed by oxygen atoms on the surface of the clay particles. Some partially hydrated cations in the pore water are also adsorbed to the surface of the clay particles. These cations absorb water dipole molecules. Depending on the molecular and atomic structure and chemical properties of clays, it can be the reason for the adhesion and absorption of a high percentage of water by these minerals, sediments, or soils, or why they are difficult to dissolve in water after a long time Receive sediment and justify the action of these substances in nature.

Geology of The Southern Caspian Basin and Adjacent Areas

Northern Iran, which is actually within the seam line of the old tennis sea, with different mechanisms, includes two pressure zones, one in the east, called the Kopeh Dagh basin, and the other with tensile features, called the southern Caspian in the west. Different opinions have been expressed about the allocation of Kopeh Dagh basin to Eurasia and Gondwana. Kope Daghe foundation stone Kope Dagh with Eurasian Rock Foundation In Paleozoic times, there was an ocean called Tethys or Paleottes between the continents of Eurasia and Gondwana. The Iranian plate is part of the Gondwana subcontinent, located on the southern shore of the Paleottec Ocean. The Turan plate is located on the southern edge of the Eurasian subcontinent on the northern shore of the Tethys Ocean. In the middle carboniferous, the oceanic crust is broken and its "subduction" begins below the Turan plate. Subduction of the Paleottes oceanic crust beneath the Turan continental crust has caused the continental shelf to emerge from the water and sedimentation to stop. This process results in the formation of a series of chip-like thin sheets consisting of oceanic crusts, turbidite sediments, and deep-sea deposits known as "rising nodes." These balls are driven on the oceanic crust of Turan. These processes are attributed to the orogenic phase of Hersinin (Alavi, 1991). Ophiolites south of Mashhad and north of Fariman are remnants of these specimens. Field observations and (also Alavi, 1991). As a result, the Lias deposits of the Aq Darband area with obvious discontinuities are located on the "Upper Middle Triassic pyroclastic deposits". This sequence itself is located on a large thickness of red detrital sediments - similar to the Upper Permian molasses and the lower Triassic of the Turan Plateau - and discontinuously covers the Hersinian bedrock. This sequence is not related to the micro-sediments of the Iranian continent and is comparable to the stratigraphic sequence of Turkmenistan. With these documents, which are presented with other evidences in the following, the border between Iran and Turan plate inside the territory of Iran and at the base of Kopeh Dagh sedimentary basin is considered. Kope Dagh with Gondwana Stone Foundation Contrary to the proponents of the Eurasian theory, Iftikharnejad and Behrozi believe that the Late Precambrian-Paleozoic rocks in the Robat Qarabil area are identical to the deposits of Central Iran and eastern Alborz, and mention the Devonian-Carboniferous facades of Aq Darband as similar to the Jiroud and Mubarak formations in Central Alborz. And conclude that the Kope Dagh zone belongs to the Gondwana zone. Apart from the above two theories, the ultramafic and oceanic remains around Mashhad, which is of Late-Middle Permian age, can support an intercontinental rift in the late Carboniferous and early Permian, which, at the same time or later, forms the Kopeh Dagh basin as an independent sedimentary basin. And has raised the issue of incompatibility with Central Iran and Eastern Alborz (Aghanbati, 2004). As mentioned, the ophiolites south of Mashhad and Fariman and the Aq Darband sequence in the southeast of Mashhad are more in line with the collision of two crusts, not an oceanic rift. Triassic volcanogenic sediments in this section are related to an "arcuate basin" or in the "arcuate basin" zones of oceanic-continental crust (Alavi, 1991). It should be noted that from Devon to Triassic, geological events and sedimentation in Kopeh Dagh and Binalood show a completely different process that indicates the separation of these two zones from each other. Afshar Harb (1373) considers Gorgan, Jajarm, and Esfarayen regions as part of the territory of Kopeh Dagh and in analyzing its geography and ancient environment, points to the post-Cambrian rock units that are similar to Central Iran and Alborz. He uses the same words for naming, which can confirm that this area belongs to the Gondwana complex. However, geological findings indicate that some of the rocky facies of Kopeh Dagh, which are present in the areas of Binalood, south of Bojnourd, and south of Gorgan, are "misplaced sheets" that follow alpine movements and consequently faults on The northern margins of Alborz have been driven to great distances (Aghanbati, 2004). Geology of the time before the formation of the southern Caspian basin of northern Alborz can be considered as the border between Eurasia and Gondwana. Late Triassic to Jurassic Shemshak with limited outcrops around Neka valley and south of Gorgan in eastern Alborz are visible. On the Mesozoic sequence, which includes the Shemshak Formation to the Late Cretaceous limestones, rock assemblages dating to pre-Cimmerian orogenic times have been driven. This complex includes the Gorgan schist and the modified Upper Ordovician[1]Lower Silurian sequence, which is driven southward to the top of the Mesozoic sequence. In the Talesh area of western Alborz, the Shanderman complex, which consists of ophiolite remnants and misplaced driver plates of the deep oceanic crust, is driven on Jurassic sequences and is comparable to a sequence similar to the Caucasian varice. In the south of the Shanderman complex, the Upper Paleozoic and Carboniferous slates below the Lower Jurassic Formation of Shemshak are signs of metamorphic phases before the Cimmerian. Thus, it can be said that the southern shore of the Caspian Sea is the western tail of the Kopeh Basin. Examination of sedimentary rows in the south of the Caspian Sea from Gonbad to Moghan plain shows that Middle Miocene and later deposits, sometimes up to 4500 m thick, have a total detrital and saline nature and are significantly different from the sediments of their time in Alborz (Aghanbati 2004). Oil drilling shows that the Cenozoic sediments of the southern Caspian Sea east of Parattis have retreated from their old shores due to subsidence and declining water levels. Gorgan plain, with the effect of regression and progress of the Miocene and old Caspian Sea, accommodates a large volume of sediments, which varies from a few tens of meters in the east of Gorgan to more than three thousand meters in the east of the Caspian. Sarmasin sediments have been deposited in this plain but Ponsin sediments are absent. Also, there are Chelknin (Middle Lower Pliocene) and Agh Chanilin (Upper Pliocene) deposits in this plain, which are covered with Quaternary Caspian facies (Mousavi Ruhbakhsh, 2001). Destruction represents "Ziva".Analysis of detrital particles and sedimentary components of Zivah Formation (formerly "Zivar") attributes the formation environment of this sequence to active "arcuate" assemblages. The main sedimentary system of this sequence is mainly of river-deltaic environments and corresponds to the platform section of the south coast of "Caspian sedimentary basin". The three main sedimentary cycles of small-scale to large-scale in the supply of sedimentary components in this formation are considered distinct and distinguishable. These sedimentary cycles, from case of several meters and several tens of meters, to several hundred meters thick, depending on the case. It seems that the main reason for the formation of Ziveh Formation is tectonic changes in the basin. As mentioned, in the sedimentary environment of this formation, three factors have changed the volume and water level. The elevation of the basin floor and its subsidence have caused small and medium scale changes in the environment, and global changes in sea level (Eustace) have caused large scale changes. In the formation of basin sediments, the activity of active faults in the periphery of the environment is very important. Material, nature, and sedimentary thickness of the formation depend on the rock sequence of the sedimentary origin, erosion and weathering, distance from the sedimentary environment, energy of sediment-carrying currents, sedimentary origin changes, as well as type of fault and tectonic processes during sedimentation in The environment is relevant. The facies of Ziveh Formation have been of "progressive delta" - "regressive" type to the southern regions of the southern Caspian basin. These facies are as deep as expected to their northeastern regions. Numerous coastal currents have been responsible for the transport and distribution of sediments in the "deltaic slope" of the formation. In parts of this formation, horizons rich in organic matter and coal have been reported. This formation has been introduced as the main reservoir rock in extensive studies conducted in the region by the French Oil Company. However, no economic hydrocarbon reserves have been reported in the area so far.

Geology of The Southern Border of The Caspian Basin (Central Alborz)

The southern boundary of the Southern Caspian Basin consists mainly of Neogene detrital deposits, which are located next to the limited red and brown sedimentary sequences of the Southern Caspian Basin and are themselves the origin of deposits in the Southern Caspian Basin. Degradation and erosion of the heights of each area during geological times can expose the structure and stratigraphic history of the surrounding basins of that area. When erosive currents flow from the heights to the pits of each basin, they carry the particles extracted from the heights with them and deposit them downstream. As a result, detrital particles always record evidence of the tectonic history and long-term climate of the basin. Coarse-grained sediments associated with this erosion process are deposited near the "origin" and at the forehead of subsidence basins. Sediment volume is affected by area erosion rates, tectonic activity, and bedrock composition. Corrosion faults and the formation of erosive discontinuities in the basin margins are related to tensile or compressive processes in the mountain belt, while regional erosion may be affected by climate change and changes in the water level of the area. By analyzing and interpreting the geological events of a region, one can get an accurate view of the history of the formation of the basin and the region.

Alborz Regional Geology :

The Alborz Mountains are part of the folded belt of faults in the northern regions of Iran, which has structural features of the southern Caspian basin and is connected to central Iran from the south. The result of the confluence of the two zones of central Iran and the southern Caspian basin (Eurasia) is the creation of the Alborz mountain range. The construction process, which covers 200 to 500 km of the Neuttis seam at the junction of Saudi Arabia and Asia. As mentioned, the southern ridge has geological features similar to central Iran, while the northern slope events are influenced by geological events in the southern Caspian basin. It is believed that both sides of this region have started to form a continuous tectonic[1]sedimentary unit at the site of the Eurasian collision since the beginning of the Pliocene. According to Walter's law (1860-1937), facies that adaptively appear in a vertical sequence can also appear laterally in immediate environments. Gradual advances and regressions can help predict vertical facies changes. Retreat facies: The shoreline shifts to the depths of the basin. Advance refers to the migration of sediments and facies to the depth of the basin, and generally the facies are shallow upwards in a vertical section. Progressive facies: The shifting of the coastline to the land is called advancing. In such a case, the sediments deepen in an upward vertical column. The seam line and collision of these two pieces are considered in the north of Gorgan, northeast of Mashhad, and in the northeast of Talesh, in the current area of the Alborz belt. Gorgan schists located in the northeastern region of Alborz represent a part of the northern parts of the Paleontis seam line, which contains slightly modified "fine-grained sediments" of Late Ordovician igneous assemblages. The assemblage is driven southward and upward in a severely deformed Late Paleozoic sequence to the Middle Triassic. After the collision process and during the reopening of the basin during the Early Jurassic (Toronin), detrital siliceous sediments of the Shemshak-Kashfarud Formation were deposited in the front of the basin during the Retin-Lias period. Since then, seawater depositional conditions have led to the formation of a carbonate platform during the Late Jurassic and Cretaceous. Upper Cretaceous sedimentary sequence consists of carbonate marine marls that sometimes show different facies on two different sides of east and west of Alborz. In the western and northern parts of this basin, sediments include tuff and lava, while in the southern and eastern parts of Alborz, volcanic activity decreases. In the northern parts, the marine sediments of the shallow Paleocene areas are initially sloping, in limited areas above the Cretaceous carbonate sediments. Regional tension in the southwestern parts of Eocene in the Eocene has caused very hot currents and magmatism that has affected all areas of the Neuttis subduction zone in eastern Central Iran and southern Alborz. Northern Alborz and Kopeh Dagh have not been greatly affected by this phenomenon. The Eocene marine volcanic sedimentary sequence in southern Alborz is three to four km thick. This sequence has spread throughout the Alborz, with its widest outcrop in the western regions, which gradually narrows in the eastern regions and has less continuity. This marine sequence has evaporative sediments and limestone in its upper part. This process has been observed in Central Alborz, but in the southwestern parts of the Alborz Mountains, the earth's surface is often covered with submarine volcanic sedimentary deposits that persist until the Oligocene. Volcanic acid rocks are seen in this area as a different stratigraphic unit that is discontinuously located on volcanic sedimentary rocks. In addition, this sequence (like similar and similar sequences in Azerbaijan) provides quartz and feldspar detrital particles (quartzite and arcose sandstone), clay minerals (feldspar alteration), and destructive mica of the basin and itself with layers. Neogene light is covered discontinuously. In some places, a basal conglomerate has formed in some outcrops. Also, the building pits between the heights of the Alborz Mountains are filled with these continental detrital fragments, which are red layers and the remains of "evaporative pans". Following the retreat of the sea in the time after Bordigalin, there is a thick sequence that is up to 5 km thick. This thick sequence in the western parts of Alborz has outcrops that are mainly detrital and volcanic, has Neogene age and are located in several local basins, among the regional roughness. These detrital sediments originate from the elevated heights of Alborz. In the Iranian part of the Caspian Basin, marls, sandstones and conglomerates and red evaporitic deposits with or without volcanic rocks are related to a wide age range from the Oligocene to Pliocene. These deposits are collectively known as Neogene red layers.

Geology of The North Alborz Cenozoic

Northern Alborz has experienced a different geological history during the Cenozoic. In the northern part, no sedimentation took place before the beginning of the Miocene. The Neogene marine layers are located above the Late Cretaceous and Early Paleocene limestones, on which are coarse-grained and destructive continental layers of the Pliocene age. During the Early Pliocene, in the Caspian Sea, the sea level dropped abnormally and abruptly to about 400 meters. This event occurred at the end of the Messinian period and is similar to a simultaneous event across the Mediterranean between 7,246 to 5,332 million years ago, resulting in a kind of drought and a sudden increase in salinity. Following this phenomenon, the sea area at that time was reduced to half its current level. Surrounding rivers were allowed to advance, creating special deltas that could deposit "masses" and large volumes of detrital particles into "more remote areas" within the basin. The Pliocene sequence in the northern Alborz region includes a conglomerate with between sandstone and mudstone layers that is covered with conglomerate, sandstone and Upper Pliocene marls. The passage between these two horizons is discontinuous in some cases and gradual in other places. Neogene formations and Paratethys facies do not protrude at the site of the northern Alborz fault. Meanwhile, the thickness of the Late Pliocene-Quaternary layers in the northern part of the Parattis area increases dramatically from east to west and from land to sea and along the Caspian coastline of the South Caspian. Are drilled by the National Iranian Oil Company. This evidence indicates an increase in basin subsidence in the western Caspian Sea; Where the White River delta is the main source of sediments. Morphology of Tertiary stratigraphic sequence based on the studies of its predecessors, morphology and early formation of Alborz was initially located along the main structures of northern Alborz and the mountain belt and elevations. These faults, as the case may be, mark the structural boundaries between the two main zones introduced above, which include the areas east of Paratethys, central Iran, as well as north and south of Alborz. In addition, the amount and manner of sedimentation along the axis and the trend of the Alborz Mountains have obvious changes. Caspian marine facies in the northern part of Alborz in the north of the North Alborz Talesh fault zone, the sedimentary sequence of the Caspian Sea includes Cretaceous sediments and younger rocks. In the northwestern regions of Alborz, the Upper Cretaceous sequence is composed of Cretaceous tuff deposits with lava and to a lesser extent limestone layers that gradually and laterally turn into silty and calcareous marls in the northwestern regions of Alborz. This evidence indicates a decrease in Cretaceous magmatic activity to the east. Paleogene sequences in the northern Alborz in the form of "Lower Paleocene marine sediments" are absent in other areas, except in a few limited locations that cover Cretaceous sediments and older formations without discontinuity. The absence of Eocene-Oligocene layers in most areas of Talesh and Northern Alborz is related to orogenic processes along the Talesh North Alborz fault and erosion following this sedimentary sequence, after which the thickness of Paltogen sediments are affected and reduced in thickness. Neogene and Quaternary layers in the Caspian sequence have been identified and described in several cross sections. These sections are related to and well comparable with the drilling operations of exploratory wells and regional outcrops in the northwest of the basin in Azerbaijan and east of the basin in Turkmenistan. Neogene sequences have been affected by relative changes in the water level of the Caspian Sea and the rise of the Alborz Mountains. This process is the result of erosion or lack of sedimentation process and has caused interruption and temporal rupture of geological sequences of Caspian facies in northern Alborz. The red marl formation of the Middle Miocene was first introduced by Ernie (1931) in the Alborz Mountains. The formation consists of purple-red marine marls with interbedded limestone, sandstone, red conglomerates, basalts, and gypsum layers that are discontinuously located above the Late Cretaceous to Early Paleocene layers, indicating an erosive phase. Before deposition begins the marine sequence. Next to the formation are layers of clay, marl, sandstone, and greenish-gray bioclastic sediments containing ospaniodontella fossil oysters. Also, the upper Miocene layers containing "folate" are continuously placed on top of it. This sequence consists of clay, sandstone, marl, marl limestone that has a "fossil oyster's fossil's shell" and gradually turns upwards into sarcomasin layers. The upper parts of the Sarmasin layers do not exist due to the effect of the destructive phase of the Pliocene, which probably coincided with the retreat of the Caspian Sea. A thick sequence (more than 1,700 m thick) containing a conglomerate with intermittent marl, sandstone, and fossil limestone, called continental series or brown layers, is discontinuously located above the upper Miocene layers. Takes. This lack of folds between the Sarmasin layers and the continental series is difficult to detect and may have lasted for millions of years. The continental series is the oldest detrital sediment in northern Alborz. This sequence consists of Paleozoic spherical rocks with Eocene components that confirm the deep and significant erosion in the "backbone" of the northern Alborz during the Early Pliocene. The continental series is followed by Late Pliocene layers and sequences known as the Aq Chgil Unit (Formation). Geologists of the National Iranian Oil Company have also used the term colored zone to refer to the Aq Chgil Formation. This stratigraphic unit consists of conglomerate, marl, and sandstone at the base and loess at the top. A marked discontinuity at the base of the Agh-e-Chaghil Formation during the Middle Pliocene۔High in exploratory drilled wells and in seismic profiles of the Southern Caspian Basin has been detected by the National Iranian Oil Company. At the top of the Aq Chgil unit are Quaternary leads with a thickness of more than 2600 meters. These Quaternary layers are deposited under active subsidence conditions, along the Caspian edges and in front of the Alborz Mountains. Within the Alborz Mountains, about two million years ago, continental series sequences were replaced horizontally by more than 3,500 meters of sediments driven along the Caspian Fault. The first thousand meters of this sequence is located above sea level in the south of the Caspian fault and is evident in deep drilled wells in the southern Caspian basin. In turn, this sequence falls below 1,600 to 2,000 meters of younger sediments. This sedimentary trend is a sign of rapid subsidence of the basin, which has played a role in the formation of this stratigraphic column. In general, the rate of subsidence increases from the east to the west of the basin and from the land to the sea. The depth of Aq Chaghl base in drilled wells in the east (Gorgan-Gonbad areas) increases from about 600 to 700 meters to 1300 to 1400 meters in the central parts (Mazandaran) and to 2610 meters in the western areas (Anzali). The Quaternary sequence begins with the Apsheron Formation, which consists of green-blue-gray marls and fine-grained sandstones between volcanic ash layers. Although the Apsheron Formation is officially considered to belong to the Late Pliocene, Nikki Fora (1968) attributes it to the Early Quaternary (Mousavi Ruhbakhsh, 2001). The sequence is covered with detrital mudstones and less hardened sea sand, with thin gravel layers within the Old Caspian basement. This sequence itself leads to sediments of the new Caspian basement, including uncharged sand and gravel. In the Gorgan region in the east of Alborz, the Pleistocene is present in the Caspian sediments of the present era. These sediments can be related to the time intervals between glaciers and steppe weather conditions. Sediments with thin lamination related to the marine environment along with landslide sediments are often visible in the northern Alborz. Many of these landslides occurred during the Pleistocene glacial period, when the weather was considerably wetter than it is today. The stratigraphic column of the formations of this period is as follows (Figure 7):

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In general, a large part of the Paleogene Alborz magmatic sequence forms the Karaj Submarine Formation with the Middle Eocene age, which includes tuffs and interlayer lavas. In the southern Talesh mountains, this formation is very thick, the widest extension of which is in Tarom and the southern Talesh mountains. In this area, Karaj Formation includes different components of lava flow and sand layers and tuff mud deposits that have been deposited in the marine environment. Paleogene layers of the western Alborz are more magmatic than the central eastern Alborz. The Oligocene sequence is characterized by onshore volcanic deposits more than 6 km thick. The Acapel igneous massif in this area has a Late Paleocene, which is probably a prelude to the extensive Middle Eocene magmatic activity. Meanwhile, since the Middle Eocene, a scattered horizontal of red, laterite, and ignembrite sediments (fused tuffs within the semi-marine sequence of the Karaj Formation appear randomly and unexpectedly). Major changes in igneous rocks occur during the Oligocene. Early Oligocene igneous rocks in some outcrops contain red conglomerates that are separated by a discontinuous horizon in several sections from the older horizons of the Karaj Formation. In the central-western Alborz, the age of interlayer basalts that are discontinuously located on the lavas of the Karaj Formation (Eocene age), the Eocene-Oligocene boundary has been determined. An intrusive igneous mass has cut off other Oligocene volcanic rocks. Evaporative red and green sandstones, silt, and marls with volcanic flows and detrital fragments of the Lower Red Formation following sea retreat during the Eocene, deposited in several lagoon basins simultaneously with the rise of Central Iran during the Eocene-Oligocene have became. This formation has different shapes in different places and in general in western areas, it is more conglomerate and interdigital or in the form of semi-marine basaltic lava flows, while in more eastern areas, it has more saline facies. , Sand, shale, and gypsum marls and detrital igneous facies are seen. After the advance of the Tethys Sea in the Middle-Late Oligocene, marine conditions prevail in most parts of Central Iran, which is the culmination of the beginning of the Miocene. During this time, limestone of Qom Formation is deposited in Central Iran, the stratigraphic equivalent of which is less visible in Alborz at that time. Marine limestone layers are locally visible on the southern edge of Alborz. A layer of indicator basal limestone is placed on the lower red formation in the same shape as the slope, which is gradually covered by the upper red formation. In some outcrops of western Alborz, this limestone is conglomerate and has between its layers in its lower part. The Oligomycin Sea to the north gradually turns into detrital and riverine sediments near the coast. Marls and layers of red gypsum sandstone are also deposited in the eastern regions. Towards the mountainous areas of Alborz in the northern part, no clear boundary between the upper and lower red formation is clear. The similarity of oligomycin sediments and red layers makes it difficult to distinguish the upper and lower red formations as well as the non-marine part of the Qom Formation. Therefore, in several sections, the totality of this non-marine sequence is referred to as Neogene red layers or Neogene sediments. Also above the Neogene red layers are Pliocene age conglomerates that are inseparable from their underlying layers. Along the southern edge of the Alborz, an erosive discontinuity separates them from the lower units, but elsewhere this passage is gradual or steep. There is a limitation to determine the age of the upper parts of the Upper Red Formation due to the lack of detectable fossils. Quaternary sediments of volcanic rocks and Quaternary detrital sediments are identified in several geological sections in the center and southern Alborz, especially around Damavand peak. Damavand mountain with a height of more than 5600 meters is a composite cone that has a volume of more than 400 cubic kilometers and is made of Thracian-andesitic lavas and detrital igneous rocks. This magmatic activity is associated with the removal of pressure from molten material. The age of these reactions dates back to 1.8 million years to 700,000 years ago. Volcanic rocks along with Damavand igneous rocks are concentrated in its central areas and at a distance of 40 to 50 km from the current position of the peak. Many sediments are the result of severe erosion of these roughnesses in the area. The last volcanic activity in western Alborz occurred shortly before the Late Pliocene (2 million to 830 thousand years ago). The volcanic sequences associated with these eruptions are on deformed and almost deformed river sedimentary rocks, which may sometimes be Quaternary in age. Landslide sediments, filled local seas, detrital sediments, and wells travertine deposits are present within the Quaternary layers of the southern Alborz. In the northern regions of Alborz, many large landslides may have occurred in wet Pleistocene environments. These debris have blocked rivers and created local sea basins. Landslides in the present day may also have been caused by strong tremors caused by large earthquakes in the mountain belt. Also, destructive and transported loess sediments related to the Pleistocene time are visible in the lower part of the Sefidrud valley. Expansion of The Brown Layer Formation The so-called "brown layers" formation, known in the Republic of Azerbaijan as the "production series", are protruding in some areas of Alborz. From the aggregation of the reports of the National Iranian Oil Company and the initial geological maps prepared, no specific practical information is obtained. Perhaps one of the most important reasons is the lack of scientific and research communication between researchers working in the Caspian Basin in the territories of neighboring countries. It is certain that due to the long history of drilling and extraction of hydrocarbon reserves, especially in the last century, and due to its importance at the basin and local scale, the sedimentary sequence of the Caspian Basin in the former Soviet Union and its moons have been studied, while The knowledge of researchers active in Iran is limited to field surveys and scientific and operational observations of wells drilled in this area. In this regard, it is important to mention a few. In the country of Iran, most of the specific sequences of the Caspian Basin are hidden by the vegetation of the region in terms of hidden and due to the humid and sultry weather of the region. Although the available strata were first described and distinguished by geologists, the entire sedimentary sequence can be described in terms of sediments from mudstone to conglomerate with reddish-brown color and poor cementation. The condition of the cementation and the nature of the facies determine the formation of this sequence in the offshore or freshwater zone. Due to the rate of degradation and high sedimentation rate and the destructive nature of the Cenozoic sequence of the Southern Caspian Basin and the possibility of "re[1]transporting" its sedimentary components to higher sequences, dating of ostracod or pollen-containing and palynomorphic layers has no operational value during the drilling process; Although it helps a lot in detailed studies and analysis of the basin. During a report prepared for the Caspian Oil Company in 2005, Sahabi briefly refers to the study records of this sequence. Accordingly, Ernie first described the outcrops of this sequence in 1310 and 1311, when preparing a geological map for the National Iranian Oil Company on the banks of the Tajan River in Mazandaran (based on internal reports of the National Oil Company). Iran). "Stocklin" in 1320 AD, when preparing the geological map of Mazandaran officially, described the sequence of the brown layer formation (equivalent to the red or chalky layers in Turkmenistan), which is equivalent to the formation of production series in the Republic of Azerbaijan in the Caspian he does. Shortly afterwards, in 1930, Ernie again referred to the sequence equivalent to the Chelken or Production Series, which belongs to the Middle Pliocene, as the "Continental Series" until in 1961, "William et al." Russian scholars name the series "Chelken" after the above sequence (Sahabi, 2005). During the project, Sahabi (2005) states that sedimentation until the Late Miocene due to general regression affected by the Laramide orogenic phase, has not been done in the basin and Late Miocene and sometimes Early Pliocene sediments on the Cretaceous sedimentary sequence are discontinuous Are. In the east and southeast of the Caspian they are deposited only 45 meters from the lowest part of the Paleocene. He considered the formation environment of Middle Pliocene layers as intercontinental and related to shallow and marginal closed environments and this sequence in Golestan and Mazandaran plains (especially in Alamdeh, Javaram, Gorgan A3 and Ghezel Tappeh 2 wells). , And in the north of the dome of Kavous has observed Gilan and Moghan). He considers the lower unit of this sequence to have components of dry continental and coarse-grained environments and believes that the re-advance of the sea during the Late Miocene (Sarmasin-Ponsin) was the reason for its formation. In this analysis, it is not clear how the Late Miocene Sea advance caused the deposition of terrestrial sediments, or whether the Caspian Basin margins appear to have risen at this time based on compressive tectonic activity (low Caspian aquifer level) It has fallen and caused the formation of detrital components and its transportation into the basin. These two basins have undergone a separate evolutionary process according to the origin of sedimentary load, tectonics, and depth of the basin. Both basins are covered by a very thick sedimentary sequence in the southern Caspian basin. The boundaries of Kopeh Dagh and Alborz basins coincide with Mazandaran and Alborz faults. It is natural that tabs from the deposits of the Southern Caspian Basin in the remote areas towards the "central pit of the basin", sit on the sedimentary sequence of Kopeh Dagh and Alborz basins. Towards the far coast and the center of the southern Caspian Basin, the thickness of the Neogene sediment sequence increases significantly (Technical Report of Meysam and Meqdad Wells). Also, in Sahabi report, the thickest section is mentioned near Shirgah and Javaram with about 269 meters thickness and the lowest thickness is related to Anzali region. It seems that after the Hersinin incident, two basins were formed in the southern edge of Turan, including Kopeh Dagh with a trend to the northwest and Alborz with a trend to the southwest. He states that in the southwestern margin of the Caspian Sea, southeast of Golestan province, and north of Gonbad, no brown sequence has been formed and the Aq Chanel Pliocene sediments are located directly on the Lower Cretaceous sequence. According to its findings, the nebula suggests that from now on, instead of the Chelknin sedimentary sequence (Middle Early Pliocene), the name "Javaram Formation" and instead of the Agh-Chanilin sequence with the end Pliocene age, the name "Gonbad" Formation on deposits Let's choose the territory of Iran. However, the above sequence in the "land sector" of Iran is not significantly thick and can not be clearly separated and mapped in this area. In the Moghan plain, especially in the Garmi and Parsabad areas, Neogene rows are widespread. In this plain, the lower and middle Sarmasin deposits are mostly of brown clays, gypsum siliceous marls, and a little lime, which are about 2500 meters thick. Upper Sarmasin and Lower Pliocene rows have not been reported in the Moghan Plain, but Upper Pliocene deposits with a thickness of 500 m consisting of oyster marls below and sandy marls above are present with a small amount of tuff and conglomerate. The Moghan Quaternary deposits are of the alluvial barracks and coniferous deposits of the present era, which are located directly on the Upper Pliocene deposits (Aghchil Formation). According to the stratigraphic history, it can be concluded that from the beginning of the Paleocene to the Late Miocene, there was no orogenic movement in the Moghan region. The first orogenic phase in this region coincided with the Athenian event, which occurred in the late Miocene, and as a result of which the old sediments were folded and the young sediments of the Aq Chgil Formation were placed on them intermittently. Due to the function of this orogenic phase, there are no Pliocene sediments at the beginning of Chelkan Formation in Moghan plain (Aghanbati, 2004). Salt Compounds of Sea Water Seawater salts and ions play a decisive role in its biological and non-biological properties. In addition, the study of salinity and ion changes, especially for lakes such as the Caspian, can reflect the periodic impact of water-feeding rivers or geological events. In this section, the results of Abtahi 2003 and Russian researchers are used. The salinity of the coastal waters of the Nur region is 13ppm, which is consistent with the results of research conducted by Russian researchers. The salinity of the Caspian Sea in the Gorgan Bay region (eastern part of the southern Caspian) is 16ppm. Due to the lack of river water and also the intensity of evaporation in the eastern part, the salinity of surface water in all seasons is higher than other parts. The amount of chloride in the light region is 5516ppm. The amount of sodium ions in the light region is 4470ppm and in the Gulf of Gorgan 5533ppm, which is higher than the information provided in Russian sources. The amount of sodium ions in the mentioned sources is 3160ppm. The ratio of sodium ion to chloride ion in light is 0.81 and in Gorgan is 0.80 .The amount of sulfate ion in open water is 2700ppm and its ratio to chloride is 0.14, so in any case the relative amount of sulfate in the Caspian Sea is much higher than in open water. The amount of magnesium ion in the light region was 500ppm and in Gorgan Bay was 737ppm. According to studies conducted in 1933, this ion was 740ppm in the southern Caspian and 750ppm in 1962. The ratio of magnesium ion to chloride in light was 0.09 and in wolf was 0.11 . Potassium ion was measured at 100ppm in the light region and 260ppm in the Gulf of Gorgan. A measurement made in the Southern Caspian in 1933 showed the amount of this ion to be 100ppm. The ratio of potassium ion to chloride in light is 0.02 and in Gorgan Bay is 0.04 . This ratio has been mentioned by Russian researchers as 0.019. Potassium ion in open water is 400ppm and its ratio to chloride ion is 0.02 equal to this ratio in the Caspian Sea. The amount of calcium ion in light waters was 160ppm and in Gorgan Bay was 247ppm. According to studies conducted in 1933, the amount of this ion in the Southern Caspian was 330ppm and in 1962, 360ppm. The ratio of calcium ion to chloride ion was calculated to be 0.03 in light and 0.04 in wolf. The ratios obtained in this study are less than the value presented in the sources of Russian researchers; 0.062 and 0.066 . The amount of calcium in open water is 400ppm and its ratio to chloride ion is 0.021 .Therefore, the relative amount of calcium ion to chloride ion in the Caspian Sea is slightly higher than that in the high seas. Conclusion According to research; Closure of the Caspian Basin, severe dependence on the Volga River, high evaporation rate and limited freshwater inflow, can be concluded climate change, unprincipled oil and gas extraction, water transfer projects and in general any factor that the distribution system Chemical compounds of salt and fresh water inhibit the Caspian Sea inflow can exacerbate environmental hazards and saline conditions in the eastern Caspian Sea in other parts of the country, including the southern basin and the Caspian Sea of Iran.