نشریه کواترنری ایران
پیاپی 1 (بهار 1394)

1-Introduction Geographical and natural potentials of Zagros and archaeological findings from the studies suggest that this cultural area has been used for human societies from pre-history to the present days. Many devastating earthquakes (The earthquake of 872 AD Saymareh) and a lot of landslides in the Zagros, caused severe environmental changes in this region. Landslide occurrence in Kabir Kuh,blocking the Kashkan and Seymareh river and subsequently formation of the Jaydar and Saymareh lake are among the most important environmental changes in this region. Kashkan River is one of the environments that provides a suitable environment to settlement in this area from past to the present. But environmental changes, especially Kashkan river redirections and formation of the Jaydar Lake, had significant effects on the settlement pattern of archaeological environments in the past. Therefore, the aim of this study is to investigate changes in settlement patterns of archaeological sites in the area of the jaydar lake after occurrence of kabir kuh landslide. 2-Materials and methods The Jaydar Lake located in the western parts of Pole-Dokhtar is considered as studied area. Field and descriptive-analytical research methods along with tools such as topographic maps, geologic, satellite images, GPS and other software like Arc GIS and Global Mapper are used to assess the changing process of the settlement patterns of archaeological sites. Then, extensive field studies have been done in the area and with observing the lake deposits at several points on the periphery of Khorramabad- Poldokhtar road;and then recording their heights, Lakes area has been drawn based on 740 meter contour. In the next stage, the position and period of archaeological sites on the lake area have been overlapped and using investigation of the height and thickness changes of sediments in the lake, the settlement pattern changes of the archaeological sites after formation of Jaydar Lake during the different periods have been analyzed. Finally, at the end of this study the results are presented. 3-Results and discussion kabirkuh Landslide, is the world's largest landslide and based on Thermoluminescence dating method on deep lake sediments amples of Saymareh lake, Kabir Kuh landslide time has been determined equal to about 15700 ± 2500 years. After the occurrence of landslides and blocking Kashkan river, Jaydar lake has been formed behind apile of sediments slide. Jaydar lake formation has coincided with the formation of the first stage of Saymareh lake. Because only in the first step, landslides had the most volume and vastness so that it blocked the Kashkan river path. Based on field studies Jaydar Lake area is calculated around 88 square kilometers. Chronologically, 27 archaeological sites have been identified in the area Show that archaeological sites have been created in the prehistoric, historic and Islamice period.The distribution pattern of the identified 27 Archaeological sites show that all the ancients ites are located in adjacent too rat a distance of less than 1000 meters far from the Kashkan River. Proximity to the waterand flatness of its surface have been the most important factors that affect the formation and distribution of archaeological sites adjacent to the lake. Other factors such as topography and fertile land are important in the formation of archaeological sites, have been affected by the water level of the lake and then by the river. So that the rise in water level is directly related to the height of archaeological site and the fertile lands in the margin of river. Investigating changes in the height and thickness of the lake sediments show that in the Bronze period we can observe the formation of a permanent establishment(or perhaps semi-permanent establishment) and adjacent cemetery for the first time. In addition, during this period we can see the formation of archaeological site on these dimentary terrace at the end of these dimentation basin of Jaydar lakes. 4- Conclusion The study of 27archaeological sites from the EpiPaleolithic period to the late of the Islamic period in the Jaydar lake sedimentation area showed that during this period, major changes in the settlement pattern of archaeological sites in the lake area have been occurred. All of these changes are directly related to the occurrence of kabir kuh landslides and the subsequent formation of Jaydar lake and its remaining sediments.Gradual risein water level, brought about loss of 6 human kind settlements in the late period of Epipaleolithic with average height of 695 meters from the open waters of in the lake margin and for cible migration to more elevated areas. It looks like that water in the Neolithic period reach to its highest level, 740 meters,and up to the end of this period remains at the same level. With beginning of the Chalcolithic period the height of the archaeological site areais reducedand areas that have already been buriedunder the water, in this period once they become residential. Formation of the first permanent settlement with in the Jaydar lake, coincides with the Bronze Age. In addition, residents of this area in this period of time for the first time build graveson lake and river sediments. Two periods of drought during the Iron Age cause the formation of Iron Age sites in the alluvium mountain path and near the river Kashkan. In the historical period(Achaemenid, Parthianand, Sasanian) much of the lake sediments(probably up to the entrance of Poldokhtar) have been dried. In historical period, archaeological sites to access the river have been formed in the closest parts to the river.The pattern of settlement in the early Islamic periodis not much different from the previous period. But at the end of the Islamic period and After over 5000 years, the basin sediments of Jaydar lake are dried and conditions for the formation of new settlements especially in the Jaydar plain area are provided.

Iranian plateau with its outstanding geographical and climatic conditions has been considered a key region in the study of Pleistocene human societies. So far numerous Paleolithic sites have been discovered throughout Iran; however, our knowledge concerning the Upper Paleolithic occupations was limited to Zagros region. The Upper Paleolithic occupations of northern Alborz Mountains and southern Caspian Sea has been remained unknown. In this context, the discovery of the open air site of Garmrud 2 by the French-Iranian Paleoanthropological Project (FIPP) in 2005 was a major breakthrough in case of filling the mentioned gaps between older Paleolithic materials and those of Mesolithic from the southeastern of the Caspian Sea (e.g., Komishan, Huto, Kamarband, Al Tepe).
Materilas and The southeastern of the Caspian Sea is a strategic region for those interested in prehistoric human movements and dispersions. This regain is one of the proposed migratory corridors for prehistoric societies. The studied area is located between two geographical barriers: in the north is located the Caspian Sea and in the south of the Alborz Mountains. Between these barriers, there are Mazandaran and Gilan Plains with high rate of precipitations and numerous permanent and seasonal rivers. Such geographical conditions have made these plains so fertile, and attracted human societies since prehistoric times. Even today this area represents one of the densest human populations in Iran.
First, it was Carlton S. Coon who conducted several field missions at the southeastern of the Caspian Sea leading to the discovery and excavation of two famous caves of Huto and Kamarband (Coon, 1951, 1952). Later Charles McBurney from University of Cambridge followed Coon’s footsteps and excavated sites of Key-Aram I and Al Tepe (Ali Tepe). In most recent years, another Mesolithic site (Komishan Cave) was excavated in the region (Vahdati Nasab et al., 2011). The astonishing point conserving these sites chronology is the fact that none belonged to the Upper Paleolithic (Key-Aram I consist of Middle Paleolithic and Mousterian materials and the rest was assigned to the Mesolithic period). For some reasons it was believed that the Upper Paleolithic is the lost period in the north and northeastern of Alborz. Similar scenarios have been observed in Turkmenistan and Tajikistan, which provoked some researchers to claim due to some climatic obstacles of these geographical regions were abandoned during the Upper Paleolithic period. That is why the discovery of a well dated site of Garm Rud 2 could shed light on some of the key aspects of this enigma. This site, which is situated at the river cut of Garm Rud River nearby the Baliran village in Amol, has witnessed three consecutive excavations producing immense amount of data in form of lithic, bones, and shells. The absolute calibrated dating of 33878±3300 plus dominance of balde/ bladelet knapping technologies leave no room for any doubt to associate Garm Rud 2 with the Upper Paleolithic period. Evidence of fauna remains in close association with lithic materials indicates that Garm Rud 2 was a butchering station, which was occupied for a brief time period. Lithic assemblages of the first excavation season were the subject of this research. In this regard, only 2.6% of the assemblage belongs to core/core fragments. Such fact plus low quantity of cortical pieces indicate that the initial preparation stages were taken place somewhere outside of the site.
Bladelets are in largest quantity followed by flakes with no secondary edge work and blades. Considerable number of flake debitage implies that they have been byproducts of bladelet/blade production sequences.
In case of comparative studies, Garm Rud 2 represents close affinities with the two Upper Paleolithic open air sites of Sefid-Ab and Delazian both located at the southern hills of Alborz Mountains. At the same time it deviates significantly from the Upper Paleolithic cave site of Yafteh in Zagros. Prior to apply any stylistic explanations, the geomorphological formations of these sites must be taken into considerations. In addition, the site formation and usage of the sites must be taken into account. Yafteh is a Karstic cave in Zagros, which based on its strategic location and abundance number of lithic/fauna materials had been a base camp during the beginning of the Upper Paleolithic period. On the other hand, as it was mentioned earlier Garm Rud 2 was a butchering station with short occupation period; therefore, comparing lithic techno-typologies of Yafteh and Garm Rud 2 might not provide comprehensive results. Up until present Garm Rud 2 is the only well dated Upper Paleolithic settlement at the north of Iranian plateau.

Intruduction: The research specifically examines the Quaternary magmatism of Kurdistan (Bijar) and its relationship with the region's tectonics. Due to parallelism with Zagros main fault and continental collision zone, it seems that such magmatism indicates continental collision zone as well. But the reason of this magmatism is not clear. However, there are examples in the world that can represent magmatism in this region continued even with 15 million years interval. Considering the breadth of the magma composition, thickness of the lithosphere can be an important parameter in understanding of magma petrogenesis. Reported thickness of the lithosphere in the study area is about 150-200 km. The thickness of lithosphere causes changes in the composition and chemistry of magma in the region. One of the points in this research is phase delay activing after the closure of Neotethys Ocean till Quaternary magmatism. Allen et al. (2013) provided a model for melting involving subduction and dewatering of sediment of Arabian passive margin beneath the Eurasian plate as a result of melting of the Eurasian lithosphere. In this study, it was necessary to consider more precisely these three reservoirs of magma in terms of petrography and chemistry and then rising of these magmas and its relation with Area’s tectonic. Observations show three sources of magma in different combinations and sometimes different chemistry. So, magmatism of Bijar can provide a good view of the processes that control the composition of the continental lithosphere.
Field study and systematic sampling were performed in vertical and horizontal orientation from the volcanic flows. 70 samples were taken in order to thin section preparation and petrography. 30 samples were selected for chemical analysis and investigation of major and trace elements. Samples from new units and nonmethamorphic area were analyzed by the methods like XRF (S4) (in determination of major elements), ICP (in determination of trace elements) and XRD (in order to mineralogy of powder samples) in geological survey of Iran.
Bomb fragments, Lapilli, ash and scories can be seen around the crater of the volcano. The Gneissic xenoliths in Quaternary basalts can be seen. It created Porphyiric texture that contains fine-grained or sometime glassy context with big crystals in it. Although in some thin sections, Microlite and intergranular texture were observed. The main minerals are Olivine, Pyroxene and Plagioclase. Subsidiary minerals are visible as apatite and Opak minerals. According to geochemical investigations, rocks in this area are located in Sodic-Potasic alkaline or potasic zone. In the process of some of the elements such as MgO, SiO2, TiO2, Sr, Rb, Zr, Y, Th, Pb, Zr/ Y, Rb/ Th increasing and in some of the elements such as CaO, Co, Ga reduction can be seen. In some cases on the variation diagrams, samples are sporadic and do not show a clear linear trend. The slope of diagram of REE distribution pattern- chondrite (Nakamura, 1974) in the rocks of the area is negative and LREE elements are more enriched than HREE elements. The rocks do not show negative Eu anomaly. In the distribution pattern diagram of trace elements of the area rocks versus mantle rocks (Wood et al., 1979) Titan depletion is observed. Niobium and tantalum also show a slight depletion. Given that the basalts of the area were alkaline, they got compared to alkaline basalts of the Afar and Kenya Rift (Eastern African Rift). Tectono-magmatic diagrams are also used somewhat to determine tectonical environment associated with eruption of these magmas. Microscopic studies show that the texture of rocks in this area is more hyaloporphyry, microlitic porphyry, hyalomicrolitic porphyry, and sometimes intergranular. Phenocrysts of clinopyroxene, olivine and plagioclase in Microlitic context are made of the same minerals and glass. Petrographic studies show that differentiation, digestion and pollution have contributed to the formation of rocks in this area. The evidence of differentiation in these rocks is presence of minerals like Glomeroporphyritic and Glomerocryst and also the presence of olivine, clinopyroxene, Plagioclase with Labradorit- bentonite composition in basaltic rocks. Evidence for digestion and pollution is presence of quartzic Gezenocrysts with reactive margin of pyroxen and presence of gneiss zenolite.
According to the major elements diagrams, the rocks belong to the series of alkaline basaltic. In terms of amount of potassium, they located in the range of potassium from moderate to high. According to the major elements changes diagram versus DI, crustal contamination and subtraction have been effective in the process of rocks formation. Considering the trace elements changes diagram versus DI, it can be also concluded that differentiation process has been effective in the formation of rocks. According to the distribution that is sometimes seen in these diagrams, and the high average of crustal elements abundance (Elements that have a high concentration in the crust, such as Rb) and vertical trends, it can be said that in addition to differentiation, the phenomenon of magma contamination with crust is also effective in rocks formation. The selective diagrams of trace elements also indicates that in addition to differentiation, other processes such as magma contamination have been involved in the petrogenesis of intermediate magmatic rocks. It can concluded from the negative slope of REE diagram namely the high LREE versus HREE, the difference between pattern of rocks in this area with diagonal basalt pattern, similarity of the sedentary element pattern like Y, Yb, Sr to the OIB alkaline basalts pattern (resulting of low grade partial melting of the enriched asthenospheric mantle) and also the alkaline composition of basalts in this area which the origin of basaltic magma was not from a depleted mantle source but rather originated from an enriched mantle source and is a result of relatively low degree partial melting. The high LREE is not necessarily the reason for the low component melting and generally factors such as magma origin (asthenosphere or lithosphere). Mineralogy and composition of minerals entered during melting, the degree of partial melting, fractional crystallization, magma subtraction and the volatiles can cause this condition. Considering distinctive tectonical diagrams and evidences in continental crust, tectonical environment is a continental inter plate environment. These diagrams reinforce hypothesis of rocks formation in a tensile environment. Especially that these lavas belong to Quaternary and there is not any active subduction system in Iran right now.

Wind erosion is considered as the most important factor in degradation of Iran desert areas in Quaternary period and at the present time, 30 million hectares of surfaces are affected by the wind (Ahmadi and Feiznia, 1999: 429). Plains vast space, inadequacy or lack of vegetation, abundance of fine particles, looseness or detachedness of particles are some of the factors that have provided necessities for the wind to form interior plains (Alaei Taleghani, 2005: 295). Vegetation limits transportation of sediments by reducing wind speed. This action causes accumulation of wind sediments around vegetation and formation of Nebkha landscapes in result. In other words, Nebkha is the result of interaction between wind erosion and vegetation. Khalaf (1995: 275) argues that morphology of Nebkha is controlled by growth patterns of plant species to a large extent. Stallins (2006, 4) states that understanding of ecogeomorphological landscapes takes place by considering ecology and geomorphology processes and feedback between them. Therefore, the type of plant species forming the Nebkha and the connection among characteristics of plant ecology and Nebkha cones morphometry are the most important topics in Nebkha sediments morphology and systematic analyzes. This study tries to rely on quantitative characteristics in geomorphology. Also, relationships among factors of Nebkhas landscape will determine yielding Nebkhas. Since several factors are involved in Nebkha morphology, this study tries to investigate the importance of vegetation in the Nebkha morphology without changing some of the other factors. In other words, by selecting a limited area of study, climatic factors (wind, rain and ...), sedimentary factors (size, grading and ...) and time is assumed constant. Therefore, changes and communications made by performances of plant species forming Nebkha have investigated. The main purpose of the research is to investigate relationship between vegetation morphology and Nebkha morphometry characteristics based on statistical analyzes.
First, by using aerial region images, then by using field study, the study area and then the Nebkhas territory were determined. Sampling took place along transects that cover the entire area then the morphometric characteristics of Nebkha were measured along each transect. Sample size determined by Nebkhas locations along the deployed transects locations. Totally, 60 species of Capparis Spinosa were evaluated. In order to study characteristics of Nebkha, the morphological factors like attributes, height, slope (North, South, East and West mean slopes) and base diameter were measured and in order to evaluate the vegetation forming Nebkha, plant morphology factors such as mean length of the branches and number of branches were measured. The technique for measuring the relationship between plant traits and morphological traits has been stabilized by simple and multiple regression analysis using SPSS software. Regression equations such as linear, quadratic and cubic are tested for optimizing the results.
Pearson linear correlation analysis results between Nebkha morphometric characteristics and plant morphology characteristics suggest that the most correlation is between the branch numbers and Nebkhas height, to the extent level of 0.94 degree. Also, the correlation between the mean length of branches and Nebkha height is to the extent level of 88.0 degree. And also, the regression analysis results of comparison between Nebkha morphometric characteristics and plant morphology characteristics suggest that the largest relationship for linear, quadratic and cubic equations with probable error level of less than 0.01 is between the mean length of branches and Nebkha height to the extent level of 77 percent.
Results of multiple regression analysis have used to investigate the amount of all plant variables effect on the morphometric Nebkhas. Model 1 justifies multiple correlation analysis, between components of Nebkha height and the mean length of branches and the branch numbers with the mean coefficient of 0.89. Model 2 has designed for the relationship between two variables the mean length of branches and the branch numbers with Nebkha base diameter and the model coefficient is 0.743. Model 3 stated the relationship between the mean length of branches and the branch numbers with the mean slope cone. In this model, the regression coefficient is equal to 0.722.
In geomorphological studies, figures of the earth are reflections of surface processes and their systematic structure. Investigating structure and function of these systems would cause access to their past and also ability to draw their future evolutionary path. Research results show that a strong correlation between the components of Nebkha morphometry and plant morphology can be seen in the study area. Results indicate that the numbers of Capparis Spinosa species branches have the greatest impact on sedimentation of wind deposits.

Received: November 10, 2014 Accepted: March 15, 2015
Paleoshorelines are the most important key landforms for studying evolutionary trend of coastal sedimentary environments. Hormozgan province is one of the Iranian coastal provinces at the north of the Persian Gulf and the Oman Sea representing high variety of geological settings influenced by regional and local geological events. According to large scale coastal landmarks, sedimentary environments have been formed mainly since the late-Quaternary. Intrusion of the Precambrian salt domes, structural development of rocky coasts, and the Quaternary glacial and interglacial events have contributed in shaping of Hormozgan province’s coastal area. Fossil beaches as landmarks of regression coasts can be observed at 12 large coastal dune fields. They demonstrate superficial evidences of sea level fall tracts especially since the late-Quaternary. Recognition of the mid-Holocene mechanism of land progradation and rate of shoreline mobility is required for interpretation of regional coastal sedimentary environments. Therefore, main aim of this research was determination of evolutionary trend of paleoshorelines along the Hormozgan province.
The research method was included application of geographic information system (GIS), surveying of geo-indicators, and dating of fossils using 14C. Therefore, digital topographic maps (1:25,000 scales) and satellite image (IRS, 2006) of spatial resolution 6 m, and numerous aerial photos (flown in 1967 at an approximate scale of 1:20,000) as materials in order to obtain the research objectives were used. Thus, mapping of paleoshorelines and fossil beaches was carried out using GIS tools. Additionally, survey of coastal features, check of maps accuracy, and collect of in-situ fossils from paleoshorelines were implemented during field observations. The Kerian and Band-e-Moalem were chosen as master areas for 14C dating from east and west of the study area, respectively. The 14C dating (Ultra Low Level Liquid Sintillation Counting on Benzene) of fossil samples was conducted using a Quantulus 1220 instrument calibrated with oxalic acid I with a detection limit of DL = 1-2 pMC at the Laboratory of Gamma Spectrometry of Iran’s Atomic Energy Organization. Resulting data was calibrated by using CalPal-2007-HULU software, Cologn radiocarbon calibration & paleoclimate research pacage, Germany.
Paleoshorelines and their distribution were identified at 12 dune fields where superficial evidences of sea transgression (TS) and falling stage system tract (FSST) have been formed since the mid- Holocene. Details of the most reliable landmarks of shoreline mobility at Kerian and Band-e- Moalem areas were obtained. As results, S4, S24 and B1 were dated 4329±64 BP, 1787±43 BP, and 1306±14 BP, respectively. Height of paleoshorelines was calculated to be 10.21, 5.58, and 3.76 m using DGPS where they are located at 4570, 500, and 244 m far from the present coastline.
Therefore, the mean rate of shoreline mobility of S4, S24 and B1 were calculated to be 1.05, 0.28, and 0.186 m yr-1, respectively.
Present research has concluded that rate of sediment supply, tectonic movements, and hydrodynamic condition had been relatively constant between 4000 BP and 2000 BP. Accordingly, coastal ridges have been distributed parallel to the shoreline uniformly without considerable disruption. Results confirmed that regression coasts at the eastern coasts have been created wider and completed than the western coasts. Superficial evidences of the mid-Holocene sea level fall in the study area have provided opportunity to find out regional evolutionary trend of paleoshorelines and to sketch sea level curve for the Persian Gulf and the Oman Sea. Therefore, importance of Quaternary landmarks along the north of the Persian Gulf and the Oman Sea was highlighted by present research for further investigation of coastal zones formation.

Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. This phenomenon is the result remolds sand particles. Soil liquefaction occurs in loose, saturated cohesionless soil units (sands and silts) and sensitive clays when a sudden loss of strength and loss of stiffness is experienced. Sometimes it is resulting of large, permanent displacements of the ground. Even thin lenses of loose saturated silts and sands may cause an overlying sloping soil mass to slide laterally along the Liquefied layer during earthquakes. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world. Destruction of buildings, roads, land subsidence, and even loss of life is one of the dangers of liquefaction.
Liquefaction hazard evaluations generally deal with three issues: liquefaction susceptibility, initiation of liquefaction, and effects of liquefaction. The issues are generally addressed in the order listed, since the latter issues are dependent on the former. Assuming a soil is judged to be susceptible to liquefaction. Its potential for initiation under the anticipated earthquake loading conditions is then judged. This process is usually described as an evaluation of the soil’s liquefaction potential. There are various methods to evaluate the liquefaction potential of the soils. Using the Soil Penetration Test results is the one of the important method to investigate of the liquefaction potential in uncemented deposits. Seed and Idriss are the pioneers of the using SPT to investigation of liquefaction potential (Seed & Idriss, 1971). In recent decades, evaluation of the liquefaction potential by shear wave velocity has also been recommended by National Institute of Standards and Technology (NIST, 1998). Cone penetration test (CPT) results have also been used to evaluation of soil liquefaction potential by Robertson and Wride (1998).
In this research, the liquefaction potential of the Imam Khomeini Port has been investigated. The port is situated at South-West of Iran at the North of Persian Gulf. In recent decades, numerous numbers of infrastructures and oil & gas facilities have been developed in this area. According to geological investigation the studied area is in the folded Zagros structural zone. No volcanic activities have been reported since Mesozoic. The sedimentary rocks are the main geological formation in this region. The large part of the port has been constructed on low level quaternary deposits without any rock outcrops in the studied area. The quaternary deposits are mainly loose and uncemented. The ground water level of the region normally is high due to penetration of the saline water from Persian Gulf. Considering to high level of groundwater table at sea coastline, the site could be vulnerable to liquefaction during possible earthquakes. It should be mentioned, Zagros folded zone is one the most active part of the Iranian structural zones.
In this study, Standard Penetration Test (SPT) and shear wave velocity (Vs) measurements have been used to evaluate the liquefaction potential of the alluvial. Simplified procedure of Seed and Idriss (1971) has been used to evaluate the liquefaction potential based on SPT method. The cyclic stress ration (CSR) and the cyclic resistance ratio (CRR) were evaluated in 160 borehole data and the safety factor was given in each borehole. The correction factors for depth and cementation of the soils have been applied based on Seed & Idriss (1982) and EPA (1995). The site area is evaluated high liquefaction potential based on this analysis. On the other hand, the liquefaction potential assessed using the Vs measurements based on the method proposed by National Institute of Standards and Technology (NIST) in 1998. In this study, 160 borehole data were studied considering the soil type and ground water level. The safety factor at different depths and liquefaction Potential Index at different boreholes were compared. Generally, results of the two methods are in agreement, especially in shallow depth for SPT method and in lower deep for shear wave velocity method. Based on the analysis results and considering to seismicity of the region, the liquefaction potential is high in some part of the studied area. The result of liquefaction potential evaluation of the studied site has been presented based on different peak ground acceleration. The results showing the most of area are highly vulnerable to liquefaction even by 0.3 PGA. Therefore, we recommend the soil of the area should be treated before any construction in the site. Since the thickness of the loose deposits considerably is high, dynamic soil treatment method specially suggested.

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.