1-Introduction: Examinations 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.

Wetlands are the remnants of pluvial lakes which have evolved following the retreat of glaciers in the late Pleistocene era and have overcome the hot conditions and the development of evaporative deposits in the Holocene era. Most arid and semi- arid areas, desert lakes, PLAYAS and similar landforms have been disturbed as a result of human activities. Recently, mineral extraction prompts destruction of the playa surfaces and irregularities in the incoming water in order to create a new evolution in these geo- systems. This new evolution provides a suitable situation to change the micro- landforms, and these irregularities or turbulences in geodynamic systems are the best evidence for converting them to other systems and, also, they can be studied by fractal geometry. In this study field studies were conducted in the winter of 2015 in order to examine the situation of the Gavkhuni playa southeastern Isfahan Province and the changes in micro- landforms and, in these, 109 mud cracks in the wetland zone of Gavkhuni playa were examined. Among them, 61 well developed mud cracks were used in the calculations. By using the fractal geometry perimeter-area model on these micro- landforms, their turbulence could be examined, and the DAP, derived from the fractal model, was valued at between 1.27 – 1.44; this expresses the confusion and irregularities in the micro-landforms of that region. The logarithmic graph of the fractal model showed a linear relationship between the log of perimeter and the log of area on that micro landform and, so, the correlation coefficient R2 is greater than 0.96. Increasing chaos in the Gavkhuni playa shows the evolution in the geodynamic system and its transformation into a new ecosystem that it can yield to produce serious risks in this area.

In drylands, both dust storms and ephemeral salt lakes (PLAYAS) are common. Observations using remote sensing and ground studies have shown that these PLAYAS can be major sources of saline dust storms. Some basins have recently become desiccated as a result of water abstraction by humans, and these have become significant sources of dust. The timing and amounts of dust emissions depends on such factors as rainfall and drought events, the availability of sediment, and the nature of surface crust materials.

This study was done in the wet marginal part of the Siahkooh playa (Kevir) in Yazd, Iran, which is located in the northwest of Ardakan. The abundance of Ca and S04 iones led to gypsum crystallization near the water table in the soil. From depth to the soil surface, the CaCO3- CaSO4 , 2H2O -NaCl-H2O-PCO2 soil and water system change to CaSO4, 2H2ONa2SO4- NaCl-H2O. From water table (100 cm under soil surface) to the soil surface, ionic power was decreased and activity coefficient was in crased respectively. Therefore, near ground table, gypsum form and high concentration of Ca iones from gypsum lead to low amounts of exchangeable Na. This influence has been continued up to soil surface to achieve a relative balance. Replacement of Na with Ca on the exchangeable surfaces of soil and existance of SO4 iones formed NaSO4 inerals. The precipitation of 1800ton per hectar natrium salts (sulfatic & coloridic) was estimated with respect to the mean of annual evaporation (roughly 900mm) in the studied site. The result also showed that the seventh bands of Landsat 7 are more important to differentiate between sulfate and chloride salts as well as sodium and calcium salts.

Introduction Playa refers to internal regions, which are typically flat and covered by salt or salty fine-grained clastic sediments. Playa is the deepest part of a closed basin of a desert area, which has smooth surface with slight slope and is covered by fine-grained sediments. These surfaces have either no or little vegetation. Basically, due to the high water table of underground waters and the lack of appropriate drainage, the soils around the PLAYAS in Iran are always subject to saltiness because intense evaporation and presence of capillarity force result in accumulation of salt in different soil horizons and surface zones of the PLAYAS, which leads to inappropriate ecological conditions for establishment of plants. Creation of PLAYAS in Iran is a geological phenomenon in which human plays no role; since, as a result of dynamic movements during Mio-Pliocene period in recent 7million years, many of the Iranian deserts such as Dasht-e-Lut and Dasht-e-Kavir (also known as Great Salt Desert) have been created, which currently have growing desertification trend. During the rainy (glacial) stage, surface of the PLAYAS was expanded, saltiness of water was reduced, and sediments were mainly clay-silty at center and coarse-grained at boundaries; however, during the interglacial stage, similar to the current period, surface of the PLAYAS were smaller, waters were saltier, and sediments were mainly evaporite and gypsum. The internal depressions in Iran in quaternary (fourth) period have been formed as a result of the folds during Oligocene period and then have been filled with erosive matters such as molasses (soft greensand along with maroon and conglomerate). These sediments have been folded by the last Plio-Pleistocene phase of Alpine orogeny. The PLAYAS in Iran have generally surrounded all the internal plates as well as many of the inter-mountain depression. The major environmental conditions that cause formation of PLAYAS in Iran include: petrologic characteristics, structure, depth and elevation, drainage status, and climatic conditions of environment. Methods and Material Respecting the subject and objective of the present study, it was conducted via statistical analysis and field survey. For this purpose, various data, statistics, and information were collected from the study area, and various methods were selected and used for data analysis. Therefore, in general, the present study is aimed to investigate the geomorphological changes of the playa in Meydan Gel in Qatruyeh during quaternary period. The topographic maps used in this study, which covered the entire Iran, included maps with 1: 250000 and 1: 50000 scale compiled by Geographical Organization of Armed Forces. Also, these maps covered the PLAYAS in Meydan Gel including: Neyriz NH40-9, Meydan Gel 6948II, Beshneh 6948I, Vazireh 6947I, Darab NH40-13. As for the geological maps of the study area, the 1: 250000 map pf Neyriz (H-II) and 1: 100000 map of Qatruyeh provided by GSI Organization (Geological Survey & Mineral Explorations of Iran) were used. Moreover, the geological 1: 100000 map pf Darab provided by GSI was used as well. Results and Discussion Since, under hydromophological conditions rivers, waterways network, and lakes exhibit different behaviors as regular flow, mixed flow, mud flow, and flood flow, measurement of the sediment particles' diameter and determination of their weight percentage is called granulometry. During the quaternary period, the climate has had some fluctuations and has passed warm and cold epochs. During the cold epochs in regions such as Zagros, internal regions of Iran, and Alborz, some pluvial lakes have been formed, most of which are currently dried due to evaporation resulting in formation of PLAYAS in Iran. In quaternary period, three main processes were important: erosion, sedimentation, and soil formation. These processes have been active from the highest to the deepest points of the world, including Iran. Therefore, from high elevations toward internal basins (PLAYAS), various processes have been active, which include: glacial processes, aeolian processes, limnic processes, glaci-aeolian processes, glaci-aquatic processes, marine processes, mass wasting (also known as mass movement), volcanic activities, fluvial processes, soil formation processes. Sediments are of an inevitable significance in aeolian and aquatic erosion studies, so that qualitative and quantitative investigation of sediments plays an outstanding role in identifying and controlling the dominant erosive processes. In both quaternary glacial and interglacial epochs, various erosion processes have occurred. In quaternary period, at glacial regions of physical weathering (degradation), the weathering process is dominant, and consequently the small and large pieces become angled. As a result of freezing process, the soil is disrupted and some disturbances are created in its structure, resulting in sedimentation. Once the ices are melted ad water is flown, the rocks collide together, the smashing of which results in sedimentation in depressions and lakes. Conclusions Results of the present study showed that at the borderline of playa and erosive plain, the water table would be at higher level, which is dependent on the genus of sediments in this part; so that, the medium-grained sediments are placed at this section and then tend toward fined-grained and wet salty sediments by moving toward the playa. The water level variations occur as a result of fluctuations of the rate of input and output water (evaporation) from the basin. The high water level causes carbonated (calcite and dolomite) sedimentation, while in case of low water level, the sulfated sediments, including gypse and then magnesium sediments, are deposited. Through a complete deposition cycle in PLAYAS and limnic environments, the clastic, carbonated, sulfated, and chlorinated sedimentation process occur in a downward (top-down) direction. In such case, the minerals' content variations from clastic to chlorinated along the playa's core must exhibit a regular reduction; whereas, due to the climatic changes and water level variations, such trend is not seen in Qatruyeh playa. The water level variations can be investigated using the minerals found in playa. The water level variations are commonly associated with sulfated-to-carbonated phase conversion (increased water level) and carbonated-to-sulfated phase conversion (reduced water level). Alternation of evaporativeclastic minerals in PLAYAS is an excellent paleoclimatological evidence, so that during periods with wetter climate, due to the increased sedimentary load of rivers, mainly the clastic minerals entered the river; while, during the warmer periods, the evaporative sediments' content was increased.

Introduction: Playa is one of the most important landscapes in arid regions which covers about 1% of the world's total land area. Study of PLAYAS is important from different points of view especially pedology, sedimentology, mineralogy, environmental geology, groundwater and surface water chemistry. More than 60 PLAYAS have been identified in Iran. Considering the fact that PLAYAS and surrounding landforms are important archive of landscape evolution and paleoenvironmental variations, it seems that less attention has been paid to them so far. Soils are known as indicators of the landscapes evolution. Previous studies in arid regions of Iran imply different periods of deposition and soil formation in playa and alluvial fans or pediments. Bajestan playa is one of the known playa in northeastern Iran, and the largest clay flat exists in this playa. There is no information on the soils and their evolution in Bajestan playa. The objective of this study were to 1) identify the soils in different landforms along a transect from alluvial fan to clay in Bajestan playa 2) determine the morphological, micromorphological and mineralogical characteristics of these soils 3) determine the periods of soil and landform evolution and 4) comparison of soils evolution of the study area to other arid regions of Iran.

The source of sandy dunes has been the main question in desert regions. Several theories have been already presented about this question around the world. In addition, several methods have been already invented and applied to find the source of sandy dunes. In this research, the relationship between playa and sandy area in Yazd province was studied using GIS. At first, the maps of sand dunes and playa in the province as well as neighboring areas were produced. Then, the distance and direction of all sandy polygons to the nearest playa was calculated. Meanwhile, the geographic center of sandy polygons and playa polygons were identified. According to the results, around 60% of sandy polygons had a distance less than 10 kilometers to the playa, and their average distance to the nearest playa was calculated to be 12745 meter. In more than 79% of sandy dunes, the nearest playa was located in the North West. The average angle of PLAYAS to the sandy dunes was 332 degree (N), matching with the main windroses and sandroses of province. Therefore, if all sandy dunes and PLAYAS are converted to one place, we will have one sandy dune with an average area of 4717 hectares as well as a playa with an average area of 220506 hectares in the northwest of sand dune. Eventually, according to the prevailing wind direction, the hypothesis of the role of PLAYAS as the main source of sand dunes in the Yazd province is reinforced.

The purpose of this study is to investigate the morphology of the sand dunes located in Zarin Erg in the northwest of the city of Yazd and its accordance with the wind data provided by the surrounding synoptic stations. The results showed that the sand dunes have different morphologies, including simple dunes, seif, barchans, star, and complex dunes. The complexity and variety of the dunes indicates the drastic variation of wind regimes seasonally, annually as well as periodically. Also, they do not match with any wind data of the surrounding synoptic stations. The presence of barchans in the quadrilateral erg is indicative of directional winds. The local winds are the main cause of the formation of these dunes and their morphology. Indeed, due to the difference of height between the central Iranian PLAYAS and upstream mountainous, the PLAYAS of this part of Iran often serve as thermal low-pressure centers on the Earth surface, and their marginal sand dunes are always moved by these winds. The accumulation of large amounts of sand in the southeastern part of the erg and the formation of star dunes with a height of more than 200 meters are signs of prevailing north-west winds in the warm season and the severe winds of the southeast in the cold season. These winds reinforce the power of local convergent winds.

This research was performed to evaluate the potentials of Landsat MSS data for mapping land features in arid zones of southeastern Esfahan, Iran. Databases of the area were formed using all available relevant maps and reports which were supported by fieldwork.A supervised image classification approach was used and thirty-two training areas were applied. Separability of the spectral classes was examined using feature space plots of imagery data and self-classification of training areas. The accuracy of the classification was examined by using test and random pixels. The results show the potential of Landsat data for the discrimination of landforms and zones of the PLAYAS. Sand deposits (deflated sands and Barchans) expressed different spectral reflectance which could be due to mineralogy of these features. Soil classes differing in moisture content and salinity located on the soil line and limestone classes located along the soil line. The applied imagery data disable to discriminate Barchans from Bare soil I and Andesitic fans from Grey limestone. After image classification the spectral classes were merged to form landforms. The main landforms were mountains, piedmonts, sand dunes, valleys and PLAYAS. The results indicate that integration of field observation and supervised classification can compensate for the lack of detailed topographic maps in some areas.

Due to the land use changes like increased acreage for agriculture, digging deep and semideep wells has increased rapidly in recent decades in Marvast area as these wells are the main source of water supply at the present time unlike the past which rivers and aqueducts had this role. The main purpose of this study was to monitor land use changes on soil salinity using satellite images and GIS. Our other purpose was to investigate soil salinity changes in each land unit. With using satellite information from 1984 and 2002 years and proposed method for mapping soil salinity, land use and soil salinity maps were produced and then land use and soil salinity changes were studied. The study area had a total land area of 88980 hectares in Marvast, Yazd province. Results showed that land area of PLAYAS, deserts and rangelands respectively decreased to 7.8, 2.9 and 1.5 percent versus increase of agriculture and urban land area to 77.8 and 153 percent respectively. Also during this period, sever increase, increase and decrease of soil salinity was respectively recorded for playa, agricultural and rangelands, and deserts while no changes was detected for other regions. According to results, under ground water resources and saline waters of PLAYAS have undergone serious changes as with increase in average soil surface salinity, the ecosystem has shown negative changes.