سعید رضاییان لنگرودی

IntroductionExaminations of sedimentological and mineralogical characteristics of the closed-basin cores due to the very high susceptibility to precipitation and evaporation balance are beneficial for determination and evolution of late Quaternary sedimentary specification. Orogenic movements and volcanic eruptions at the end of Cretaceous and early Eocene led to formation of Eocene volcanics in the north and some central parts of Iran. As a result of faulting which took place following the volcanism at this area, a graben was formed. This graben formed a closed basin such as Hoz-e-Soltan and Garmsar Playa, which has since become partially filled with interbedded clastic and evaporite sediments. Hoz-e-Soltan Lake with 195 km2 catchment area located at 85 km of southwest of Tehran-Qom highway, in Central Part of Iran. It is sited between 34º 56´ and 35º 31´ north and 50º 53´ and 51º 20´ east at western-north of Hoz-e-Masileh. It is surrounded by Ali-Abad and kushk-e-Nosrat mountains in north and northeast, Manzarieh and Chahar mountains in west and Mohammad-Abad and Badamcheh mountains in south and southeast. The Garmsar Playa, with an area of 700 km2, is located in the north of Central Iran and adjacent to the southern slopes of Central Alborz Mountains (north of Iran). The altitude of the studied area is 750-760 meters above sea level. The geology of the highlands flanking the Garmsar Basin comprises mainly Tertiary sedimentary rocks. Within the Tertiary sedimentary sequence, the Oligocene-Miocene rocks and salt diapirs, which are widely exposed in the north and west, are mainly composed of siliciclastics and evaporites, which are an important source rocks for the Garmsar Playa. The present research is aimed to separate sedimentary sub-environments of Hoz-e-Soltan and Garmsar Playas and it is based on study of sedimentary cores and sedimentary and mineralogical evidencens.
Materials and methodsIn the research, 9 cores were obtained from Hoz-e-Soltan Playa using a handy auger in Feb 2010. Sampling from surface down to 20 cm depth of Garmsar Playa was done. The core samples were then dissected in halves longitudinally, underneath the sediments, Playa environment was detected. In total, 113 samples of sedimentary facies related to Hoz-e-Soltan Playa and 30 samples from Garmsar Playa were prepared and then analyzed using grain and mineral analytical methods such as granulometery and mineralogy. Samples were dried in an oven at 60 ̊C for 48 hours in laboratory. Analysis of particles ˃63μ and ˂63μ was performed by using a wet Vibratory Sieve Shaker and Laser Particle Sizer, respectively. Also the analyses of all clastic, carbonate and evaporite minerals were determined semi-quantitative. Field studies of the Garmsar Playa were conducted in 2008 and 2009. Depositional environment, minerals, color, grain size and other distinctive features were noted. Over forty sediment samples were collected from the Playa surface to 25 cm below the surface. X-Ray Diffraction analyses were performed for more than 20 samples. All of analyses were done in the laboratory of Geological Survey of Iran and Kansaran Binaloud laboratory.
Results and discussionAfter obtaining the results of different laboratory studies such as granulometery, mineralogy, scanning electron microscope, morphometry and morphoscopy from 1 core (HS4) and processing the data, final investigations were done. Sediments in the central part of both Playas is almost entirely chemical (evaporite and carbonate) and in the margin of the Lake is clastic-chemical. Between the carbonate minerals, calcite is the most abundant mineral as cement in the alluvial fans and sand dunes. Quartz and calcite dominated in mud flat and saline mud flat sub-environments of Hoz-e-Soltan Playa. The clastic fraction of the Hoz-e-Soltan Playa sediment consists of quartz, feldspar and clay minerals such as kaolinite and illite, but other minerals such as muscovite, magnetite, hematite, amphibole, and pyroxene were found. Hoz-e-Soltan evaporite minerals include calcite, gypsum, halite, bassanite, thernadite, carnalite along with minor volumes of polyhalite and hexahydrite. Halite is the most abundant lithofacies in the basin. There are two main types of halite: massive halite and hopper halite. Gypsum is in the lens form, semi-translucent prismatic crystals in white, grey and yellowish brown colors. Halite and gypsum dominated in salt pan and ephemeral Lake sub-environment. From north to south, the Garmsar Basin comprises a variety of environments and their deposits including a big alluvial fan, ephemeral fluvial rivers and Playa. Their sediments generally rang from gravel size in the north through sand to mud size in the south. The Garmsar Playa comprises a variety of sub-environments, including gravel/sand sheets, dry mud flat, saline mud flat and saline pan. The sediments found in saline pans consist of alternating layers of crystalline salts and siliciclastic-rich mud. The mineralogy of salt deposits depends on the composition of the inflow waters and ground water discharge. In Garmsar Playa, various evaporite minerals such as halite, gypsum and carnalite were indentified. Halite is the dominant evaporite mineral in the studied area. The salt crusts of Garmsar Playa are characterized by elongate halite crystals chevron and other forms of crystals. Continued dissolution and reprecipition of halite and other soluble salts in the vadose and capillary portion of the crust can destroy much of the initial aligned chevron texture. Complete desiccation of the pan causes the halite crust to break up into polygons and tepees.
ConclusionThe type of sediments in both Playas includ slightly gravelly sandy mud, slightly gravelly muddy sand, mud, sandy mud and muddy sand. In the Hoz-e-Soltan Playa, there are three facies: clastic, carbonate and evaporite. In Garmsar Playa there are three facies: siliceous clastic, mixture of siliceous clastic with evaporative and evaporite. The minerals of the Hoz-e-Soltan Playa are quartz, feldspar, clay minerals, calcite and rarelt aragonite, gypsum, halite, anhydrite, basanite, tenardite, carnalite, polyhalite, thenardite and hexahydrite were found in Hoz-e-Soltan Playa. The minerals of Garmsar Playa are halite, gypsum, calcite, bassanite, carnalite, carnalite ammonium, sylvite, chloride magnesium potash quartz, albite, anortite, muscovite, chlorite and illite. Mud cracks, Aeolian sands, tepees and cauliflower surfaces are the commonest recognized features in both Playas. Sub-environments of both Playas include (from outer parts to inner parts) aluviall fan, snady flat, dry mud flat, saline mud flat, salt pan and ephemeral Lake. Most of the saline pan surface is covered by halite. These sedimentary sub-environments are based on changing of sedimentary environment according affected by climate change in Holocene.

The study of sediments and brine of playa, from economic aspects, has special significance with respect on evaporate deposits and its effect on ecology, environment and regional water. Examinations of sedimentologic and mineralogic characteristics of the closed-basin cores due to the very high susceptibility to precipitation and evaporation balance are beneficial for determination and evolution of late Quaternary sedimentary specification. Hoz-e-Soltan Lake with a 195km2 catchment area, 25-50 cm depth, located at 35 km of north of Qom, in Central Part of Iran. It is sited between 34º56´ and 35º31´ north and 50º53´ and 51º20´ east at western-north of Hoz-e-Masileh. It is surrounded by Ali-Abad and Kushk-e-Nosrat mountains in north and northeast, Manzarieh and Chahar mountains in west and Mohammad-Abad and Badamcheh mountains in south and southeast. This Lake is influenced by the volume of input water including groundwater, intermittent streams and precipitation.
In order to study hydrogeochemistry of brine in the playa, 25 samples of brine were taken from different parts of the Lake. Physic-chemical parameters were measured in the site and chemical analysis of brines was performed. Also, to study sedimentology and mineralogy and to determine salinity, 100 sediment samples were obtained up to 2 m depth by manual auger. By implementing geochemical experiments, ionic compositions of brines were recognized and by mineralogical analysis of sediments, types of minerals which occurred in deposits were determined. Samples were collected in good quality polyethylene bottles of one-liter capacity. Each sample was divided into two separate samples before being sent to the laboratory to enhance the accuracy of the results.At the time of sampling, the chemical and physical parameters of the water samples including pH, EC, TH and TDS were measured using a Hach SensIons system model 156 multi-parameter following a standard operating procedure explained by California State Water Resources Control Board (2002). In order to determination of cations and anions amounts in brine, different methods were used, such as flame photometry for sodium and potassium, atomic absorption for calcium and magnesium, silver nitrate for chlor, alkalinity polls for bicarbonate, and measurement turbidity methods for sulfate. The analytical precision for the measured major ions was within ±5%. All of analyses were done in the laboratory of Geological Survey of Iran.
The average acidity of brine of the sediment area equals to 8 which indicates alkaline nature of brine. The EC values of the samples vary from 1250 to 14280. Inlet (input) waters of Hoz-e-Soltan Lake are poor in bicarbonate ion and its mole ratio is ((HCO3 Hydrochemical studies of inlet waters indicate that mole ratio of ions is HCO3

Geological time has been evaporited sediments form by solar-driven concentration of a surface or nearsurface brine. Large, thick and extensive deposits were dominated by rock-salt (mega-halite) or anhydrite (mega-sulfate) deposits tend to be marine evaporites and can be associated with extensive deposits of potash salts (mega-potash). Examinations of sedimentologic and mineralogic characteristics of the closed-basin cores due to the very high susceptibility to precipitation and evaporation balance are beneficial for determination and evolution of late Quaternary sedimentary specification. Playa defined as an intra-continental arid zone basin with a negative water balance for over half of each year, dry for over 75% of the time, with a capillary fringe close enough to the surface such that evaporation will cause water to discharge, usually resulting in evaporites. The negative water balance includes all sources of precipitation, surface water flow and groundwater flow minus evaporation and evapotranspiration. Hoz-e-Soltan Lake, with 195 km2 catchment area and 25-50 cm depth, locates at 85 km of southwest of Tehran-Qom highway, in Central Part of Iran. It is sited between 34º56´ and 35º31´ north and 50º53´ and 51º20´ east at western-north of Hoz-e-Masileh. The maximum superficial relief is about 1940 m to the north and 1150 to the south. It is surrounded by Ali-Abad and Kushk-e-Nosrat mountains in north and northeast, Manzarieh and Chahar mountains in west and Mohammad-Abad and Badamcheh mountains in south and southeast. Orogenic movements and volcanic eruptions at the end of Cretaceous and early Eocene led to formation of Eocene volcanics in the north and some central parts of Iran, and particularly around the Hoz-e-Soltan basin. As a result of faulting takng place following the volcanism at this area, a graben was formed, which was later filled by the salt Lake. This graben formed a closed basin, which has since become partially filled with interbedded terrigenous-clastic and evaporite sediments. The evaporate facies present conform approximately to a ″tear-drop pattern″. This research was conducted with the aim to determine sedimentary facies and identify evaporate minerals as well as the change in the type of mineral composition within the sediments that were formed during the Holocene period reflecting the balance in water input and output in the studied basin.

Playa is considered as a dry inland with dry negative water balance which is dry in more than ¾ of a year. Its capillary margins are so close to the surface that evaporation resulting from these margins leads to water discharge and evaporates formation. Paleophysical and paleochemical changes of a playa make significant changes in type of sediments which can be applied to determine paleosedimentary environments and their effective sedimentary processes. Sediments and minerals of salty lakes are changed by seasonal and temporal variations of sea level, so by studying sediments and minerals especially evaporate minerals in the past, sedimentary environments can be reconstructed. The present study is aimed to reconstruct and determine Holocene sub-environments in Maharlou Lake as a playa sedimentary environment which is exactly related to input– output balance of water. Maharlou is a salty ephemeral lake. It is located between 29°17´00 and 29°23´30´´ northern latitudes and 52°41´00´´ and 52°49´00´´ eastern longitude. The Lake has maximum area equals to 28 km2 situated in 18 km from southeastern of Shiraz town. The greatest length of the lake is nearly 35 km, maximum width about 15 km and average width 7 km. The Lake's height from sea level is 1455m. There is no permanent river in catchment basin of Maharlou Lake and basin's flooding is entered in the Lake by several flood plains and seasonal (monsoon) rivers.
In the present study, 13 undisturbed cores (sub-surface) were taken from different parts of the Lake up to 170cm under Lake Floor by gravity corer. At first, the cores were described completely based on field evidences. Regarding to texture structure, color and type of sediment, the sub-environments were distinguished 85 samples preparing from the obtained cores. Granulometric analysis, mineralogy by XRD, studying sedimentary components by binocular microscope (Nikon) and Scanning electron Microscope (SEM) were performed.
The results from macroscopic and microscopic characteristics, granulometric analysis and mineralogy of cores were combined and stratigraphical column was plotted. Based on subenvironments determination, sea level of the Lake has been relatively plotted. In other words, from sub-environment of temporal Lake, salt pan, muddy salt pan and mud flat, the sea level of the Lake is reduced. Considering sedimentation rate from 0.13 to 0.3 mm in a year, the sediments under the Maharlou floor, up to the depth of 170 cm, is about the last 5000 years (Lak, 2007), indicating three origins for the sediments: clastic, chemical and evaporative origins. The sediments of central part of the Lake are nearly all chemical type (evaporative and carbonated) and marginal sediments of the Lake are clastic – chemical type. The results from XRD indicate that the minerals in Holocene sediments of Maharlou Lake include quartz, feldspar, calcite, dolomite, aragonite, magnesite, natron, gypsum, basanite, polyhalite, glauberite and clay minerals. Clastic or detrital sediments are consisted of clastic calcareous fragments (calcite and dolomite), gypsum, quartz, feldspar, muscovite and illite. The percent of clastic carbonated sediments is more than the others. Illite is the most common clay mineral in the Lake. In some horizons (layers), there are also phlogopite and polygorskite. Illite is occurred in the outcrops of the Lake’s vicinities. Polygorskite and phlogopite isn’t occurred in the vicinities and have intra-basinally formed. They are formed because of high concentration of Mg ion in the basin. The highest value of clastic sediments occurs in margins of the Lake especially southeastern and northwestern parts. Towards the center of the Lake, the presentation of clastic sediments is reduced and reaches to 2-3 percent of total sediments. In wet periods, the Lake extent is increased and sedimentary sub-environment of ephemeral Lake is developed and clastic sediments will be dominated due to high charging (input) of water. Chemical sediments of Maharlou Lake include carbonated and evaporative minerals. Carbonated minerals are deposited in carbonated zone at the beginning of brine evaporation. They are consisted of aragonite, calcite, dolomite, Magnesite, Natron. Evaporative minerals are gypsum, halite, basanite, glauberite, polyhalite, bischofite. In Maharlou Lake, in addition to magnesite, there is basanite in horizons related to dry periods. Biochemical sediments of Maharlou Lake include fecal pellets related to one of the shrimps called Artemia which is occurred in ephemeral Lake. These pellets are often aragonitic. In general, Maharlou Lake has no sub-environment of permanent Lake and the extension of alluvial fan, sand flat, mud flat and saline mud flat is small like a narrow strip. Mud flat includes silty clay containing sedimentary structures such as mud cracks and sand dunes. In this area, there are gypsum, glauberite and halite. The sediments of muddy-salty pan are clay silt having no sedimentary structure and their color is brown red or black. Aggregation of euhedral crystals of gypsum, glauberite and halite are occurred as replacement. In some parts, sandy dues and layers are observed. There is halite chevron form and fluid inclusions and vertical solution pipes and mixture of mud and salt. In salt pan, there are poor bedding halite and halite mixed with mud (rarely occurred with bedding) and transparent halite. Solution pipes indicate sub-environment of ephemeral Lake. Alternative cycles of evaporative- clastic (more often evaporative) are occurred in the area.
The study of sub-surface sediments of Maharlou Lake, from recent to nearly 5000 years ago, indicates three types of sediments in the Lake: clastic, carbonated (chemical and biochemical) and evaporative sediments. The sediments of central part are nearly all evaporative and carbonated and marginal sediments of the Lake are clastic-chemical. The sediments contain some minerals such as clastic minerals, quartz, feldspar, clay minerals, calcite and dolomite. Carbonated sediments include intra-basinal carbonated minerals like calcite, dolomite aragonite, maganesite, natron, and evaporative minerals such as gypsum, halite, bischofite, glauberite, polyhalite and basanite. Intrabasinal clay minerals are polygorskite, phlogopite and sodoeite. Biochemical sediments include Artemia pellet which is mostly aragonitic. The type of sub-surface sediments is usually sandy clay silt. The Holocene reconstructed sedimentary sub-environments of Maharlou Lake are made of mud flat, saline mud flat, salt pan and ephemeral Lake.

Soil is considered as the most important natural resources of each country. Soil erosion is a serious hazard to human life. Soil erosion not only causes destruction of soil، but also causes much detrimental effects with sediments deposited in waterways، reservoirs and dams which reduce their storage capacity. These sediments، due to their physical and chemical characteristics have the highest erodibility. In this study، the physicochemical properties of marl units on soil erosion have been determined on 31 samples in marl lithologic units based on erosion shapes and thru dominant slopes. Soil physical and chemical properties were determined by standard analytical methods. Analysis of variance and comparing of means was performed. Finally، the factor analysis was used to separate the affording factors on erosion shapes. Erosion increased with increasing SAR، EC، Na، Cl، SO4، silt and clay and decreased with increasing in HCO3، TNV and gravel. EC، SAR، Na، Cl، TNV، HCO3، SO4، gravel، silt and clay have statistically significant difference between erosion types and factor analysis showed that EC، SAR، Na، Cl، silt and clay booster and HCO3، TNV and gravel are halter factors of erosion.

In this research, groundwater quality of Hoz-e-Soltan Lake have been studied for drinking and irrigation uses according to different parameters. This lake with 195km2 catchment area located at 85 km of southwest of Tehran-Qom highway. In order to investigate is groundwater quality characteristics in Hoz-e-Soltan Lake, 34 data from water of well taken in 2008 were selected for processing and interpretation. All data were processed for determination of groundwater quality such as MAR, SSP, RSBC, PI, KR and SAR after editing of data. Base on Piper and Scholler diagram, different groups of water and suitability for drinking and irrigation uses were determined. Results show that Electron Conductivity is equal to 5308.8 μmohs/cm and total dissolve solid is 3446.4 mg/l. The pH value of the aquifer is high indicating an alkaline nature with an average of 8. Total hardness average of samples is equal to 806.8 which shows that the Hoz-e-Soltan groundwater was not suitable. The groundwater type of study area is classified in Na-Cl-SO42- class. Also, base on Na% average equal to 67.1,groundwater resources of the study area belong to the suspicious class.

Hoz-e-Soltan playa catchment area 195 km2, depth 25-50 cm, is located 85 km southwest of Tehran. The objective of this research was to determine the paleoclimate and water table fluctuations in Holocene through sedimentary facies studies. In this research, 9 cores (maximum length of 7 meters) were taken from the lake substrate, and then facies investigations, such as sediments’ characteristics, organic matter contents, colors, crystals of evaporative minerals and sedimentary sub-environment were determined. 155 subsamples were prepared from different sedimentary facies, and then granulometric analysis and mineralogy (XRD) were carried out. Results indicated that there are 5 sedimentary subenvironments,including sand flat, mud flat, saline mud flat, salt pan and ephemeral lake in the studied cores. On the basis of granulometry results, 5 sedimentary types were recognized in the subsurface sediments; slight gravel-bearing sandy mud, slight gravel-bearing muddy sand, mud, sandy mud and muddy sand. Sedimentary sub-environments of HS1 and HS2 cores are in relation to saline-mud flat and mud flat environment, respectively. Also, during Holocene lake water table fluctuation were drown and wet and dry period sediments were defined. Result shows that 6 major drought period exist in this region so during the last few thousand years, the lake had wet and dry conditions. Recent climate change and globalwarming doesnt serious effect on more drying of the lake; these wet and dry periods were frequently repeated.