جستجوی مقالات مرتبط با کلیدواژه « هولوسن » در نشریات گروه « زمین شناسی »

In the present study, in order to reconstruct the paleoenvironmental and climatic changes of Jiroft during the last 4000 years, several evidences of sedimentology and biogeochemistry on a sedimentary core have been investigated. Around. 3950 cal yr BP, low values of Ti/Al, Si/Al, C/N and CPI along with high values of δ13COM, and Paq indicate a wet period in Jiroft. evidence indicates a relative decrease in humidity between about 3900 and 3293 cal yr BP. Between 3293 and 2897 cal yr BP, Jiroft was dry and dusty. The results show very dry conditions with a significant increase in the amount of dust around 3200 cal yr BP. A long-wet period from about 2897 to 2302 cal yr BP can be recognized with high Paq values. The highest Ti/Al values along with the lowest δ13COM values indicate increased wind activity and dry conditions between 2100 and 1650 cal yr BP. Jiroft experienced wet conditions between 1540 and 1315 cal yr BP. With the relative decrease of rainfall, a semi-humid climate prevailed in Jiroft between 1315 and 854 cal yr BP.

The subject of paleoclimatology has various aspects of study importance, one of these aspects is in the field of archaeological studies. Archaeologists need accurate and clear information about the environmental and climatic conditions of that region in the past to understand the development of cultures and the rise and fall of civilizations. Lakes provide high-sensitivity and high-resolution documents and evidence, which are required for studying climatic changes and sedimentary environments at the global level. Furthermore, aeolian deposits in lacustrine environments, because of recording drought periods and dust storms, are valuable archives of paleoenvironmental conditions. In this research, to investigate Hamoun as an important water source in the southeast region of Iran, to discover the relationship between climate conditions and several thousand years old civilization in the Shahre-sokhte.

In the present study, besides collecting the previous data, it was attempted to sample three intact sedimentary cores with the maximum depth of 7.3 m and total depth of above 20 m, from the sediments of the lakebed by auger. Sedimentary facies were separated based on their color, grain size; sedimentary composition, grain shape, and type of evaporate minerals.

Regarding the percentage of the particles existing in the sediments of Hamun's bed (depth of up to 7 m), the sediment types were determined in accordance with their frequencies as follows: slightly gravelly sandy mud, sandy mud, sand, slightly gravelly sand, muddy sand, mud, gravelly mud, muddy sandy gravel, sandy silt, silty clay, and clay. Sorting the aeolian sediments was obtained through IGSD equal to 0.75, which was located in the moderate-to-good range. The average skewness in sediments of the taken cores was 0.15, which indicated skewness toward very fine particles. Also, the average kurtosis for the sample taken from pneumatic sand zones was equal to 1.3 (kurtic). The variations in the values of the parameters of some of the samples were due to the combination of different aquatic and aeolian processes in some parts of the sandy zones. Furthermore, the presence of the sediments with moderate to good sorting as well as kurtosis and skewness toward the very fine-grained particles indicated the supply of sediments mainly with aeolian origin and, in some cases, with fluvial origin.

As previously mentioned, activity of the dominant winds of the region is from north toward northwest. Existence of the heights in the west of Hamun, which sometimes reaches 1700m, acts as an obstacle against the dominant winds. In this regard, existence of Rudbandan Valley can act as a channel for the passage of the winds, and reinforce and channelize the winds. This factor can also justify the high thickness of the aeolian sediments at the crater of Rudbandan delta (core H-2). Another effective factor is the feeding of Helmand and Sabari hamuns by rivers of the drainage basin (Helmand and Farah rivers). The sediments of Hamun's lakebed demonstrate the dominance of the aquatic facies; however, such conditions are more prominent for Hamun-e-Helmand due to the great area of the drainage basin and high water volume of Helmand River. Therefore, we can see the alternation of the lacustrine facies (with dominant thickness), fluvial facies (sediments of river channel), and aeolian facies in the core H-3, which are reduced along the sediments toward the cores H-1 and H-2 and is gradually converted into the marginal lacustrine and fluvial (mainly floodplain) as well as aeolian environments (especially in the core H-2). In the core H-2, due to the low area of the drainage basin of Rudbandan, low sedimentary input, and high intensity of the dominant winds, the aeolian sediments are dominant. It seems that the sedimentation rate in the late-Holocene drought period has been very high due to the high volume of the aeolian sediments, or probably no intense erosion has occurred after the sedimentation. In other words, after the drought 4.5 ka BP in Hamun, no intense drought with severe erosion has occurred. The windiness conditions of the region in the late-Holocene have been comparable to the current 120-day winds. However, the case is different for the aeolian sediments found at the depth of 4.5 m, which is equivalent to the drought event of 800 BP and has coarser grains and less thickness. It seems that, due to the high intensity, the power of carrying has been very high, and probably again influenced by erosion after the sedimentation so that a part of the sediments has been re-carried while leaving slight thickness (40 cm). The presence of the sequence of aeolian sediments and lack of plant and animal relicts imply the complete drying of the lakebed in a certain period so that, in this period, sedimentation of the aeolian deposits has been catastrophically concordant with the sedimentation of the silty and muddy deposits of the floodplain sediments.The existence of brown-colored coarse-grained pneumatic sand particles during the early to mid-Holocene period (8.2 ka BP) indicated the occurrence of intense storms in Sistan Basin. Sequence of the fine- and very fine-grained pneumatic sands at the depth of 2.5 m represented the presence of the winds similar to the current "120-day winds" in Sistan plain. Moreover, in this study, two major drought periods (8.2 and 4.5 ka BP) were identified in Holocene sediments of the lakebeds of Hamun-e-Helmand and Hamun-e-Sabari, which indicated drying and expansion of the aeolian sediments on Hamun's lakebed. The subject of paleoclimatology has various aspects of study importance, one of these aspects is in the field of archaeological studies. Archaeologists need accurate and clear information about the environmental and climatic conditions of that region in the past in order to better understand the development of cultures and the rise and fall of civilizations. One of the important issues in this regard is the role of environmental changes over time and its impact on human livelihood and settlement. The decline of the ancient civilization of the burnt city, it shows a good correspondence with the dry period 4500 years ago. Which lasted about 500 to 700 years.

Identification of the climate changes is important for understanding the paleoenvironmental characteristics. Sedimentary evidence of the closed basins can be one of the most important methods for identifying the climatic periods and changes in the sedimentary environments. Gavkhouni Playa, as the lowland of the ZayandehRud River catchment area is located in an inter-mountainous basin in the Central Iran. This area is one of the pits separating the Sanandaj-Sirjan tectonic zone from the Central Iran, located parallel to the Zagros over thrust. A total of 16 sedimentary cores were taken from the inner part of the Gavkhouni Basin, the outer part of the basin, and the surrounding lands in order to investigate the sedimentary environments of the Gavkhouni Playa during the Late Quaternary.

The steps of this research include book studies, field works, laboratory works, data processing and then interpretation and conclusion. To investigate the paleontological climate and conditions of the sedimentary environment, 16 intact sediment cores with the mean depth of the sedimentary cores was equal to 7 m and its maximum depth was equal to 11.5 m. Sedimentary facies were identified and separated based on the sedimentary texture, type of evaporite minerals, presence of organic materials, color changes, and other microscopic components, and sampling was performed based on the changes in types of sediment and sedimentary facies. A total of 80 sediment samples were selected for granulation analysis by two methods of wet sieving for coarse-grained particles and laser particle Sizer Analysette for particles smaller than sand (Silt and Clay). Sedimentology parameters were calculated by the SediLizer software and the results were analyzed statistically by the SPSS software. Also, 3 sediment samples sent to the Marmara Research Center, Earth and Marine Sciences Research Institute in Turkey to age measurement analyzing by the radiocarbon method of organic matters.

In the studied cores, 8 major sedimentary facies identified. The facies often contains clay, silt, sand, gravel, and interstitial sediments along with vegetation and shell fossils which in most cases frequency and interference in the mentioned sediments are often seen. Changes were in particle size between clay to gravel due to process type changes, environment's energy and river input's amounts and sediment color variations concerning sedimentation conditions, presence of organic matter, pH amount, salinity and temperature variations, and drought occurrence, throughout the cores. The results of the analyses indicated the identification of eight sedimentary facies, five sedimentary environments, and two types of wind and water processes, which are effective on the sedimentation of the Gavkhouni Playa sub-surface. The major types of sediments in the Gavkhouni Playa sub-surface, mud, and sedimentary environments included the aeolian, river, deltaic, lake, and playa environments. According to the C14-AMS isotope dating analysis, sedimentation rate is about 0.4 and 0.25 mm in the western and eastern parts per year, respectively. According to dating analysis, the paleogeography of the Gavkhouni Playa and the extent of its expansion have been reconstructed at least 40,000 BP. According to the studies, about 18-40 ka BP, the Gavkhouni area has been influenced by the heavy precipitation so that, the amount of sediment load imported from the west (ZayandehRud River) has been high. The great Delta of ZayandehRud has been formed and the coarse-grained particles have been deposited in the gravel and sand sizes. Since, 11.6 -18 ka BP, along with the coastline regress, the great Delta of ZayandehRud has flowed into north of the basin. The end of Delta stretches until the center of the Playa, and sand dunes have been formed to the west of the basin. With the onset of Holocene and the increase in the temperature, it has led to an increase in the size of the aeolian sand deposits and the expansion of the playa environment until about 8.2 ka BP on the margin of the lake. Since, 4.2-8.2 ka BP, it has been accompanied by a temporary progress of the Gavkhouni Lake, and 4.2 ka BP, it has regressed again with a drought occurred about 200 years ago. The progress of the lake facies has taken place about 3.5 ka BP, after which regression has occurred and playa and aeolian facies have replaced with the lake facies. According to the type of the sediments in the Gavkhouni sub-surface, it can be said that, the conditions of the northern and eastern parts of the Gavkhouni Playa have been similar to the current conditions for at least the last 3000 years and also the conditions of the western part for at least the last thousand years. The increase in the thickness of the layers of evaporite sediments, which are mainly salt, in the upper layers of the playa indicated that the Gavkhouni Playa has become drier than before in the recent centuries.

According to the results the Gavkhouni Basin has extended to the western part of the sand dunes during the Late Pleistocene. During the Early-Middle Holocene, coastline regress and the ZayandehRud Delta progress toward the Playa have occurred in the northern part of the area. During this time, aeolian sands have spread to the Gavkhouni Playa. In the Late Holocene, semi-arid conditions have reduced the water levels, coastline regress has occurred, and playa environment has been dominated in the Gavkhouni margin. But, there were still lake conditions in the center of the Playa. Gavkhouni Playa has experienced an increase in the level and progress of the coast towards the land about 3 ka BP. The creation of arid conditions about 1000 cal BP has turned the entire Gavkhouni zone into a playa environment, and this situation has been dominated the area almost to this day.

Biological soil crusts are a community of cyanobacteria, fungi, lichens, and mosses and play key roles in arid and semi-arid regions including carbon and nitrogen accumulation, soil fertility, dust capture, soil conservation and stability. Recent studies show that the formation of biological soil crusts on mobile dunes areas is extremely difficult due to low vegetation cover, strong sand flow activity, and soil surface instability. If sand activity is controlled by the wind and the soil surface is stabilized by cover establishment and/or mechanical factors, the biological and physical crusts gradually form on the soil surface. These soil crusts play an important role in establishment and evolution of sand dunes. Lichen biological soil crusts and physical crusts are widespread on early Holocene sand dunes in the north of Golestan province. The aim of this study was to investigate the effect of lichen biological soil crusts on surface soil properties and consequently evolution and stability of sand dunes.

Sand dunes around the Alagol wetland located in the north of Golestan province were selected for this study. Lichen biological soil crusts species were collected after extensive filed study and transferred to the laboratory for identification. Three lichen species including Diploschistes diacapsis (Ach.) Lumbsch, Gyalolechia fulgens (Sw.) Søchting, Frödén & ArupFulgensia fulgens (Sw.) and Squamarina lentigera (Weber) were identified. After identification, soil samples were taken from two depths beneath lichen biological soil crusts and physical crusts. Then, soil samples were transferred to laboratory and some of physical, chemical and biological soil properties including total organic carbon, carbohydrate, calcium sulfate, equivalent calcium carbonate, mean aggregate diameter, particle size, pH and electrical conductivity were measured using standard methods. In addition, soil samples were taken from two meter depths (parent material) for particle size analysis. In this research, a completely randomized factorial design with three replications was used to analyze the data. The means were compared using LSD method at p < 0.05. SAS software was utilized to analyze the data, and the figures were drawn using Excel software and GRADISTAT (Version 8.0).

The results showed that presence of lichen biological soil crusts and physical crust changes the surface soil properties. Soils derived from aeolian deposits beneath of various lichen biological soil crusts had higher total organic carbon, carbohydrate and mean aggregate diameter in comparison with physical crusts. D. diacapsis and S. lentigera species had improved physical, chemical and biological soil properties compared to G. fulgens species. The effect of biological soil crusts on soil properties decreased with increasing soil depth. There was a high correlation between mean aggregate diameter with total organic carbon and carbohydrate. Electrical conductivity strongly decreased in soils cover with D. diacapsis and S. lentigera species compared to physical crusts and G. fulgens species in two depths. Calcium sulfate was higher in soil covered by G. fulgens in comparison with D. diacapsis and S. lentigera species. The content of fine sand and coarse silt in soils covered by lichen biological soil crusts was higher than physical crusts. Whereas, the content of fine silt and clay content covered by physical crusts were higher or similar to lichen biological soil crusts. Parent material had greater particle size distribution in comparison with surface soils covered with biological soil crusts and physical crusts. These results show that soil crusts are formed in soils with finer particle size. Biological soil crusts can increase fine particle content with two mechanisms including capture dust and weathering soils. The secretion of extracellular polysaccharides (carbohydrate) and rough surface morphology of biological soil crusts may help to capture dust (fine sand and coarse silt). Soil pH and calcium carbonate were lower in soils covered with lichen biological soil crusts compared to physical crusts.

The presence of biological crusts on soils derived from early Holocene aeolian deposits apparently plays an important role in improving soil properties. Well-developed lichen biological soil crusts including D. diacapsis and S. lentigera species may significantly lead to establishment and stability of soils derived from early Holocene aeolian deposits. It seems that G. fulgens species grow better on coarse-grained soils with higher calcium sulfate content. Lichen biological crusts increase the mean aggregate diameter and consequently increase the stability of the soil surface.  Lichen biological soil crusts have an important role in dust capture and resulted in increased fertility of soils derived from early Holocene aeolian deposits.

Lake basins have spatially and temporally index patterns and represent valuable maps of physical and chemical history. According to this point, that direct survey of climate changes has only been available as machinery in the past few decades, so past’s climate changes indexes can give a better understanding of climate changes in the past era and its causes. Of these, lake sediments have an extraordinary ability to record climatic and environmental events with high sensitivity and resolution and very high- resolution amounts. Therefore, lake sediments can be considered as regions for detecting paleontological environments. Abzalou Lake formed in the northeast of Khuzestan province on the hillsides of folded Zagros and under the Izeh unit in a pit. This study has been tried to by sedimentary examination, identification of sedimentary facies, identification of sedimentary environments and changes of these environments set to the reformation the climatic and environmental conditions of Abzalou wetland in the end Holocene.

The steps of this research include book studies, field works, laboratory works, data processing and then interpretation and conclusion. To investigate the paleontological climate and conditions of the sedimentary environment, 8 intact sediment cores with a maximum depth of 7.5 m and total of 35 m collected with using Auger corer. In this regard, tried to the position of the core be in a way that makes it possible to collect the maximum thickness of wetland bed’s sediments, give maximum coverage to wetland’s sedimentary environments and at least collect one sample in each homogenization work unit as much as possible. Based on field observations, core’s description and lab results, the cores separated into sedimentary units and their stratigraphy columns drew and determined under each sedimentary unit. Also, 3 sediment samples sent to ETH Zürich Institute of geology to age/ date measurement analyzing by the radiocarbon method of organic matters.

in the studied cores, 8 major sedimentary facies identified. The facies often contains clay, silt, sand, gravel, and interstitial sediments along with vegetation and shell fossils which in most cases frequency and interference in the mentioned sediments are often seen. Changes were in particle size between clay to gravel due to process type changes, environmentchr('39')s energy and river inputchr('39')s amounts and sediment color variations concerning sedimentation conditions, presence of organic matter, pH amount, salinity and temperature variations, and drought occurrence, throughout the cores. Three wetland sedimentary, river and alluvial environments identified. According to the age measurement, the average sedimentation rate in the Abzalou wetland is 1.22 mm / year, which this amount is different for various depths. Due to the type of sediments, the Abzalou wetland has undergone human changes for about 600 - 500 years ago. The high water period of the Abzalou wetland has been established between 1800 and 500 years ago. The study of the facies bed sediments of the wetland shows that climate change occurred gradually (not suddenly) about 1800 years ago and this trend has taken at least 200 years. The relatively dry period lasted about 700 years from 2500 years to 1800 years ago and is confirmed with the reported dry periods in the Maharlou lake about 1800 years ago, in the Mir Abad lake about 1500 years ago and in the Urmia lake between 2500 and 1500 years ago. From 4400 years ago to about 2500 years ago, stable and slow wetland conditions prevailed. The conditions for creating a peatland environment have been provided in the wetland and were associated with increasing the amount of organic matter, vegetation and shell fossils and consequently increasing sedimentation rate. This period which lasted for about 1900 years, has been accompanied by extremely humid conditions, high groundwater level and activity of springs feeder in the region. The existence of light brown mud which has the age ranges from 4400 to 4700 years ago, indicates a dry period (300 years). This dry period shows suitable approximate conformity with a dry event of 4200 years ago in the northern hemisphere. This period in the studied region appeared with at least 200 years of temporal delay. After this dry period, we see again a gray sequence with plant and shell fossils that continue to a depth of 7 meters (about 5300 years ago). At depths of 7 to 7.5 m, the existence of brown-muddy sediments along with coarse-grained sediment in size of gravel, pebble and rubble, strengthen the possibility of very strong flood in the region that sent the coarse-grained sediments of around formation to bed of the wetland or maybe has hit to the area of wetland sediments bed in the region.

According to the results of surveys in the Abzalou wetland, at least 3 high water periods with humid climate and at least 2 dry periods during the Late Holocene were identified.  Dry periods appear more suddenly and with more intensity and shorter duration than humid periods in the region and gradually lead to from very dry periods to semi-arid, semi-humid, and eventually humid periods.

There is a direct relationship in evaporative deposit with the changes in the depth of the lake. Therefore?, valuable information is gained regarding the causation of changes in environment over time. Evaporite minerals formation is a natural phenomenon accruing in water-bodies containing deferent mineral Since sulfate is abundant in seawater and saline lakes, it is main component in evaporative minerals (Lewis and Mc Conchie,1994). Playa lake deposits even in small precipitation rates may cause major changes in lake-level, salinity and sedimentary records (Battarbee 1999). The sediments generated in present saline lakes and playas have been studied by numerous researchers in order to determine the paleoclimate (Spencer et al. 1984; Holliday et al. 1996; Crowley and Hook 1996; Li et al. 1996; Enzel and Wells 1997; Menking et al. 1997; Lowenstein et al. 1999; Sinha et al. 2006; Chao et al. 2009).Playas are found in many parts of the world including Western US (Rosen 1991), Australia (Bowler 1986) and Iran (Krinsley 1970). In Iran, the ancient evaporites are present in sedimentary records of the Tertiary evaporites are found mainly in the Zagros Basin and in the Central Iran (Rahimpour-Bonab and Kalantarzadeh 2005, Rahimpour-Bonab et al. 2007a, b). In addition, Holocene evaporite deposits are widespread in numerous playas and lake/playas in various parts of Iran with different characteristics (e.g., Krinsley 1972; Shahrabi 1995; Farpoor and Krouse 2008; Farpoor et al. 2012). In his pioneering work, Krinsley (1970) studied morphology of surficial features of 60 playas within the interior of Iran. He determined characteristics, distribution, and development of the available playas. According to his findings, because the form and bedrock permeability of most of the Iranian basins have remained essentially stable since the late Pleistocene (Würm), subsequent hydrologic changes can be attributed to climatic changes.Rahimpour-Bonab and Abdi (2012) with study on the lake/playa Meyghan Flowing water with low percentage of ions and Na–(Ca)–(Mg)–SO4–Cl–(CO3) types evolve, into a brine with high ions concentration during the geochemical evolution and mineral deposition. The geochemical evolution yields a Na–SO4–Cl type brine.While clastic components (calcite, quartz etc.) show on increasing trend in relation to depth, evaporites abundances show opposite trends. Furthermore, the average grain size of sediments increases with depth indicating higher energy in the past. This study evaluated clastic sediments and evaporite deposits’ changes in the sedimentary core Maharlou lake by using physical and geochemical methods.1-2- Study site (Physical setting)The hypersaline Lake, Maharlou is located in SW Iran with an area of 24910 km2 and 1.5 m depth. The lake lies about 20 km east of Shiraz at 1,455 m above sea level (masl) [Fig. 1]. This lake is fed by direct precipitation and water inflow from surface run-offs, a few seasonal rivers and several karstic springs which compensate for the strong evaporation in a semi-arid climatic context (Dumas et al. 2003). The Maharlou catchment area consist of sedimentary rocks, mainly Precambrian diapiric evaporites associated with Mesozoic and Cenozoic limestone, sandstone, shale and dolomite formations. The formation of this lake goes back to the beginning of the Pleistocene because of its hydrogeological properties, past higher lake level stands and the survival of Pleistocene relict fish species (Krinsley 1970; Dumas et al. 2003).

Lakes are accurate intercontinental ambiences to record past environmental changes. After theorical researches, vibracorer machine took 533cm core sample from the north west of the lake near Kaftarak village. Magnetic susceptibility tool measured the magnetic sensibilities. Sequences identified and analysed after cutting sedimental core. Then, 150 samples with high resolution checked to apply combination method, however only 84 items selected. SEM method and LOI analysing system used for geo-chemistry studies. After particle size analyses, sediments are studied to identify life remains of animal and plant as well as lithologic study by using polarizing and binocular microscopes.

Lakes are accurate intercontinental ambiences to record past environmental changes. After theorical researches, vibracorer machine took 533cm core sample from the north west of the lake near Kaftarak village. Magnetic susceptibility tool measured the magnetic sensibilities. Sequences identified and analysed after cutting sedimental core. Then, 150 samples with high resolution checked to apply combination method, however only 84 items selected. SEM method and LOI analysing system used for geo-chemistry studies (Sabokkhiz et all 2015). After particle size analyses, sediments are studied to identify life remains of animal and plant as well as lithologic study by using polarizing and binocular microscopes (Sabokkhiz et al 2014). Finally, the age of the core measured by δ14c ageing technique and calculation methods. The age of the sedimental core bottom is 10813 ±60 years BP that presents the time period before Holocene. Existence of los like and lack of biological matters in 521 cm depth show the dominance of the last part the Younger drays (late Glacial). This event has the horizon of the fine grain sediments without life remains. Therefore younger dryas phase of the lake Maharlou is cold and dry. Early Holocene ages, 10200±60 years BP were cold and dry. There were evaporates with fine grains and without biological matters. Afterwards evaporate and siliciclastic particles increased, calcium carbonates decreased and fluvial environment dominance appeared followed by warm and dry age. Middle Holocene ages, 4000±60 years BP came to light by the activity of the springs when pleasant warm and wet weather controlled lakes. There were some fluctuating dry weather conditions until late Holocene age. A Hiatus and detached surface appeared in 3062±45 years BP that showed water offgoing from the lake along with surface weathering. Late Holocene starts from 2000±45 years BP. First demonstrated dry fluctuations then raining increase and then core surface which indicated drying trend of playa basin.

4-1- The age of the sedimental core bottom is 10813 ±60 years BP 4-2- Therefore younger dryas phase of the lake Maharlou is cold and dry.  Early Holocene ages, 10200±60 years BP were cold and dry weather and fluvial environment dominance appeared followed by warm and dry age. 4-3- Middle Holocene ages, 4000±60 years BP came to light by warm and wet weather controlled lakes. There were some fluctuating dry weather conditions until late Holocene age 3062±45 years BP that showed water offgoing from the lake along with surface weathering.4-4- Late Holocene starts from 2000±45 years BP. First demonstrated dry fluctuations then raining increase and then core surface which indicated drying trend of playa basin.4-5- These changes are similar to other studies for different lakes in North-West of Zagros mountains such as Parishan lake, Hashilan wetland, Neuor lake in Alborz mountains in late glacial. Recent researches about the time of the early Holocene on Oroumiyeh lake and north Atlantic sea showed lowering in monsoon currents and increase of extreme dryness in middle east, which have similar conclusions to our research on Maharlou lake.

Paleoclimatics studies can respond the many uncertainties about past climate change; an issue that is being studied seriously in the world but less attention has been paid in Iran. The Late Quaternary can be considered as Holocene. Holocene, which spans over 11,000 years ago; In general, it is considered as a period with relatively warm and stable climatic conditions. However, recent studies have shown that the Holocene climate is relatively unstable and characterized by several short-term climate fluctuations. The present study attempts to investigate the events of the late quaternary climate change in Iran. Hence, by studying various internal and external sources, first major climatic changes were identified at the late quaternary, and then these changes were detected in Iran. Then, based on the results of a case study, the results of the studies were tested.This research seeks to answer the following questions:- Is it possible to detect the major events of the Holocene climate change in Iran?- Is there a difference between the time of occurrence of major Holocene climate changes in Iran and other parts of the world?
- How has moisture changes been in cold and hot periods?

This research consists of two sections. In the first, a review has been conducted. In this section, first, using studies in relation to the late Quaternary climate change in the world, major climatic changes were identified in the Late Quaternary. Then, by studying and reviewing existing theories and resources, including books and articles, it has been attempted to determine the overall framework for climate change in Iran at the Late Quaternary. In the second part, the results of a case study were used to confirm the review studies. This case study includes a core length of 8.5 m, taken from the Parishan lake floor. In this section, two proxies were used to carry out analyzes and identify climate changes of late Quaternary, which include the use of palynology and magnetism susceptibility methods. The magnetism susceptibility technique was used to determine the warm-cold periods and the reconstruction of paleo-vegetation was used to determine wet-dry periods. To calculate the AP/NAP index, samples were taken in 10 cm interval from the sedimentary cores and pollens extracted and identified by the method of Moore et al., 1991 (with slightly change). Samples were also used to measure the magnetism susceptibility by use the Bartington Susceptibility Meter with a 1 cm interval.

 The studies on climate change in this period show a number of significant fluctuations, including four cold events: The Younger Dryas, The 8.2 ka cooling event, The Cold period of Migration time and The Little Ica Age (LIA), and 4 warm events: The climatic optimum, The Roman warm period, The Medieval Warm Period (MWP) and The Modern warming period. In the Parishan Lake, 6 major cold and warm periods in Holocene can be identified, for the four of them, it can be found that there is an approximate correspondence with the temperature changes occurring on the planet, but these courses have been delayed.

The results indicate a reverse relationship between the moisture index and the magnetism susceptibility; in fact, during warm periods humidity has increased, and humidity has decreased during cold periods. The rate of moisture index has also decreased with increasing cold intensity; in the Younger Dryas and The 8.2 ka cooling events have lowest temperatures in the region and the lowest moisture index has been recorded in these two periods. The highest moisture content was recorded in The Climatic Optimum.

The results of this study showed that there is a good correlation between cold and warm periods in other parts of the world with Iran, although between these periods in Iran and North Europe and the United States there is a time lag of approximately 200 to 300 years. Also, the existence of cold-dry and warm-wet periods was confirmed in the past of Iran. In the studied region, at the Younger Dryas and The 8.2 ka cooling events, with the lowest temperatures in the area, the amount of tree species has reached almost zero, which indicates the dryness of the area during cold periods. In all warm periods, the moisture index of AP/NAP was higher than the cold periods. It can be concluded that warm periods were generally more humid than cold periods.

The transition from hunter-gatherer to farmer- herder is one of the most important issues in archaeological research of the Holocene period. The Zagros region of Iran, especially its central parts, has had an important role in initial phases of Neolithic research in Iran. Until a decade ago, lack of evidence on the transitional period between the end of the EpiPalaeolithic period and the beginning of the Neolithic period, caused some researchers believe that southern Zagros has received food-producing subsistence from other regions such as the Central Zagros. New investigations in the southern Zagros have shed a new light on the issues regarding the neolithisation process at the region. The region of Kohgiluyeh, at an elevation between 500 to 3600 meters above sea level, located in the southern Zagros highlands, has a high potential to tracking the transition from Epipalaeolithic to the Neolithic period. Based on archaeological surveys of Kohgiluyeh region, 16 sites from early Holocene period were identified. Regarding the typology of the sites, they include 5 mounded sites, 8 open sites, 2 rock shelters and one cave site. Our main criteria for assigning these sites to pre- pottery Neolithic period is the lack of Neolithic potteries on the surface of them and existence of bladelet and bladelet cores with pressure technique. Obviously, the assignment of at least a number of these sites to pre- pottery Neolithic period can be considered cautiously and it is possible that future research confirms or refutes it. The methodology of this research is processing the information fathered from archaeological surveys of the Kohgiluyeh region. The emphasis in this paper is on the lithic analyses collected from the surface of the sites. Geologically, mounded sites of the Neolithic period in the Kohgiluyeh region are formed in various landscapes include rolling hills landscape of the Maroun River, Dehdasht plain and foothills of the Khaeez mountains. The sites are sit at 674 to 1586 m above sea level and their areas are between 3.5 to 0.5 ha. Concentrations of the mounded sites are seen in the southern half of the Kohgiluyeh region which has an arid climate. Formation of these settlements in various landscapes indicates that the region has had a high potential to attract human groups of this period. Open sites are located in two mountainous and marginal landscape of the Sour and Maroun Rivers. These sites are sit at 599 to 1036 m above sea level and their areas are between 3.4 to 0.25 ha. It seems that the main factors in formation of these sites were their proximity to mountain and water sources. Two rock shelters and a cave identified from the survey are located in southeastern parts of the region, about 900 m above sea levels. They are opened to the east and their areas are between 6 to 100m2.        Stone artifacts of chert are the most common classes of raw materials recovered from surface of the sites. It seems that, the chert which is often of dark yellow, green, gray, red and dark red color came from of local origin such as the Bakhtiyari Conglomeratic and river pebbles. Generally, in terms of the technological structure, stone tools can be classified into four main groups including core/core fragments, debitage, tools and debris. Cores include numerous single and double platform bullet cores and few flake and mixed cores (bladelet and flake cores and blade and bladelet cores). The debitage is almost exclusively bladelet and flake based.Tools are the main group of stone artifacts and some of them are include bladelet with continuous fine retouch on one and two edge, backed bladelet, bladelet with inverse retouch on both edges, end-scraper and simple burin on a flake.ConclusionAs mentioned above, 16 sites attributed to the early Holocene period were identified. Of these, 1 site is located in the Dehdasht plain, 5 sites near the Maroun River, 6 sites in mountainous landscape and 4 sites in mouth and inside of the gorges. Generally, settlement and subsistence patterns of these sites are affected by several factors such as plain, river, mountains and gorges. It seems that during this period, the plains have not been under attention enough but the mountainous landscape and margin of the rivers such as Maroun River has had a main role in attracting the human groups.

 The Zagros Mountains range with a northwest-southeast direction covers a large part of western Iran. This range acts as a barrier against mid-latitude westerly airflows and thereby generates significant orographic rainfalls, resulting in a hospitable environment which has been home to ancient civilizations. Major variations in the westerlies can lead to significant environmental changes in this mountain range. Although previous researches have shed some light on the late Pleistocene and Holocene climatic and environmental conditions of the Zagros Mountains, our knowledge on the mechanisms controlling the paleoclimate of this historically important region is yet unknown. Most of our understanding of the Zagros paleoclimate is mainly based on the low-resolution pollen studies carried out on the poorly dated sediment cores. Because the response of the vegetation changes towards climate changes is mainly accompanied by a time-lag, it is difficult to compare the pollen records of the Zagros Mountains with the different climate records of the regions that their paleoclimate response to the climate forcing is well documented. Generating high-resolution sedimentological proxy data which immediately respond to climate variations and comparing them with the regional climate records, can enable us to reveal the response of Zagros paleoclimate to climate forcing. Here, we present a high-resolution Magnetic Susceptibility (MS) and Loss-on-Ignition (LOI) records from a sediment core collected from Hashilan Wetland located at the Central Zagros.  Hashilan Wetland (34° 34 N, 46° 52 E, 1310 m a.s.l.) is a palustrine wetland located at 36 km to the northwest of the town of Kermanshah, Kermanshah Province, W Iran. According to the Köppen climate classification system (Köppen, 1931), the climate of the study area (annual rainfall: 410 mm, mean annual temperature: 15.5 °C and with 5 dry months from May to October) is defined as a Mediterranean type. The wetland is fed by a karst aquifer, called Khorrin aquifer, developed in the pure limestone of Bisotun and does not have any riverine input. The low dynamic storage volume of Khorrin aquifer makes the wetland very sensitive to variations in rainfall (Bagheri Seyedshokri et al., 2015). For example, the area of wetland shrank by 48% in 2007 due to a severe drought (Jafarbigloo et al., 2015).In autumn 2016, a sediment core was retrieved from Hashilan Wetland. Based on 10 radiocarbon ages the 315-cm long core (85-400 cm depth) ranges from 22 to 2.2 ka BP (1 ka: 1000 years). MS and LOI analyses were carried out in this study. The down-core MS scanning was carried out in 1-cm increments using a Bartington MS2C sensor. The Organic Matter content (OM), calcium carbonate content (CaCO3) and minerogenic content of the core was determined by analyzing 85 sediment samples.  The results of MS measurement represent a similar trend to the results of minerogenic content of the core, indicating the role of minerogenic components in controlling the MS signal. While they display an opposite trend to the OM content results. Basically mineral particles can be transported into the wetland by water or wind transportations. If they are transported by the water running from the karst aquifer, no major magnetic mineral is expected to be transposed into the wetland, as the aquifer is developed in a nonmagnetic limestone. Hence, it can be concluded that the correspondence between MS and minerogenic content is as a result of the deposition of magnetic dust particles in the wetland during the enhanced aeolian activities. Therefore, we interpret the MS signal as dust input in our record.Based on variations in the LOI and the MS results the core can be divided into five zones. A) 22-15.4 ka BP: This zone is characterized by minimum OM content, maximum CaCO3 content and very low to negative MS values, indicating a lacustrine environment with no major dust input. The pollen-inferred vegetation corresponding for this period indicates the dominance of a cold, dry Artemisia-Chenopodiaceae steppe (Safaie-Rad et al., 2014). Therefore, although the climate has been drier than present, the smaller amount of precipitation has sustained for a longer time and caused a lake to form under a cold climate in which the evaporation rate was substantially suppressed. B) 15.4-10.5 ka BP: A sharp change in the lithology from marl to gyttja indicates an environmental change from lacustrine to palustrine at 15.4 ka BP onward. This change most likely has occurred due to a notable increase in the temperature which is in agreement with a concurrent rise of the temperature inferred from changes in the diatom assemblages of the nearby Lake Zeribar (Wasylikowa et al., 2006). The increase in the MS values reflects higher dust input in this zone than the underlying zone. C) 10.5-7.8 ka BP: This zone is characterized by maximum minerogenic content and MS values vs. very low OM content (minimum in the Holocene section of the record), indicating intensified dust input into the wetland through the enhanced aeolian activities. The period between 9 and 7.8 ka BP exhibits the peak of dust input, which is in accordance with the desiccation of the wetland and consequently decay of the pollen grains in this time (Safaie-Rad et al., 2014). By contrast, a short-term interval at around 9.2 ka BP, represents an abrupt decline in the dust input probably due to the alleviation of aridity. D) 7.8-6 ka BP: A decrease in the MS signal and minerogenic content reflects a reduction in dust input, suggesting a decrease in aridity in compare to the previous zone. E) 6-2.2 ka BP: This zone is characterized by the Maximum OM content and decline in the MS values and minerogenic content, suggesting a wetting in the climate. This is supported by the expansion of the Zagros oak woodlands at around 6 ka BP (van Zeist and Bottema, 1977; Safaie-rad et al., 2014).These variations in the Holocene climate of the Zagros Mountains are completely opposite to the variations in the Indian Summer Monsoon (ISM) intensity recorded in the speleothem records from Oman and Yemen (Fleitmann et al., 2007), indicating the role of insolation changes in controlling the climate of Zagros Mountains.    In this study we generated the first high-resolution paleoclimate record for the Zagros mountains by measuring MS of a sediment core retrieved from Hashilan Wetland and compared our results with the regional paleoclimate records. Following conclusions can be derived from our results  Hashilan has been a lacustrine environment from 22 ka BP (the bottom of our record) until 15.4 ka BP and changed to a palustrine environment from 15.4 ka BP onwards. The MS signal of Hashilan wetland, as the indicator of dust input, along with the LOI results revealed an out-of-phase relationship between the moisture evolution in the Zagros Mountains and the ISM domain during the Holocene. During the early Holocene (10.5-7.8 ka BP) the Zagros Mountains has experienced a dry climate characterized by enhanced aeolian activities, as reflected in high MS values particularly between 9 and 7.8 ka BP. It is most probably as a result of the longer establishment of the STHPs over the Zagros Mountains which protracts dry summer season. After 7.8 ka BP, the abrupt decrease in the MS values vs. increase in the OM content which culminates at 7.5 BP, suggests an alleviation in aridity. In the period between 7 and 6 ka BP the aridity increases again but does not reach to its intensity in the early Holocene. During the Mid-late Holocene (6-2.2 ka BP [top of our record]), low dust input and high OM content reflect a wetter climate.

1. Overall, authors apparently agree that several Quaternary climate changes occurred in Iran, also on the drier Iranian highlands. However, the timing and direction of changes have been a matter of dispute (Kehl, 2009, 13).The history of the quaternary evolution in Iran, is one of the important issues that have attracted the attention of many researchers over the past decades. Despite many studies on the nature of these changes, there are still many uncertainties about it. There are two main views about the Pleistocene climate in Iran, the First, not only does not accept an increase in precipitation during the glacial periods, but also believes in its reduction from the present values. The second is believed to increase the precipitation on the inner frontier of the Iranian plateau and the highlands. Proponents of the second theory also are two groups. The first group, such as Scharlau, gives rise to a significant increase in rainfall and the other group slight increases (Ayvazi 2013). This study, based on the hypothesis that the conditions in Iran were cold and dry during glacial periods, according to the detailed researches carried out in Iran over the past few decades, as well as in the sub-Saharan Africa, Arabia and Mesopotamia in the Quaternary, intends to find a response for the origins of rainy periods comparatively. A vast area in Iran, along with the sub-Saharan Africa and the Arabian Peninsula, are parts of the dry belt of the planet. According to this fact, this research is based on the assumption that similar mechanisms have affected these regions in the past, and Iran's rainy periods are due to a similar mechanism that affected the sub-Saharan Africa, Arabia and Mesopotamia. Although, the evidences of these changes in the glacial and partly Holocene periods have been documented in Iran, there has not yet been a clear scenario for the mechanism of these changes in a broad sense.
1. In this research on the one hand, it has been attempted in an analytical way, using the significant studies that have been carried out over the past decades in relation to the quaternary and in particular the late quaternary changes in Iran, theories and evidences are described, and the mechanisms and framework of events in glacial and interglacial periods are given.
On the other hand, with a broader view of how the quaternary changes in the neighboring and distant areas, including the sub-Saharan Africa, the Arabian Peninsula, Oman and Mesopotamia, have also been examined. Thus, using the technique of comparison and reviewing existing theories and resources, including numerous books and articles, and establishing a reasonable relationship between the events in Iran and other geographic regions during the late quaternary (Pleistocene-Holocene transition), It has been attempted to determine the general framework of changes in the Iran, during glacial and interglacial periods. In this regard, while paying special attention to the humid conditions of the first half of the Holocene in different regions, including Iran, the possibility of occurrence of periods known as rainy periods or Iran's fluvial conditions in Holocene or in general in interglacial periods is discussed.
1. The set of evidences, including glacial and palynology data, show that during the last glacial period, Iran had a cold and dry conditions. This coldness and dryness were due to the expansion of the Siberian High southward. This system, even today, also governs cold and dry conditions on the territory of Iran. The aridity during the Lateglacial, probably resulted from a combination of climatic factors. The Siberian anticyclone, which today blocks all but the deepest depressions, may have been too strong or too large for low-pressure systems to penetrate into the interior of the Near East. In addition to the southward displacement of the polar front and related storm tracks, the westerlies may also have been weaker. Cyclogenesis may have been inhibited by a weak temperature gradient, and colder temperatures over the Atlantic and Mediterranean may have prevented the incorporation of substantial amounts of moisture (Stevens et al.2001).
At the late Quaternary, the cold and dry conditions of the last glacial period turned into a warm and humid climate in Holocene. The mechanism of this event is related to the changes in Earth’s orbital parameters, which caused an increase in seasonal distribution of the insolation that affected much of the northern hemisphere including African Sahara, Arabia, Oman, India, Middle East, as well as Iran(Kutzbach., 1981; Kutzbach and Guetter., 1986; Kutzbach and Otto-Bliesner., 1982; DeMenocal and Tierney, 2012). Humid condition in Iran was due to reactivation of Westerlies and northward penetration of Indian Monsoon from early to mid-Holocene.
1. In general, the geomorphic evidences, palynological data, climatic models, and archaeological data related to Iran and adjacent territories, indicate that during the last glacial period, Iran has had colder and drier conditions than today. Based on the evidences, the Indian monsoon since the beginning of Holocene, except for limited areas in the northeast, north, northwest, and parts of the west, has affected the country. In the first half of the Holocene, the monsoonal effects during summer, along with the influx of western low pressures in the cold season, led to a very humid condition, especially in the central, eastern, southern and southwestern regions of Iran throughout the year. Thus, the so called Iran’s rainy periods or fluvial periods which its different evidences have been documented, especially in the central regions, caused by these climatic systems.

Bat Guano and sediment deposition in caves have been used as an important source of information for reconstructing paleoenvironment and climate changes. Environmental conditions and climate have been mentioned as the most important factor in the economic-social change, migration and even the collapse and decline of civilizations (DeMenocal, 2001), although this is a global issue, some semi-arid regions of the world, similar to Southwest Asia, where water is a key source of civilized activity, it is more important (Kelley et al., 2015). In caves throughout the world, bats in sufficient populations produce copious amounts of fecal droppings (guano) reported at rates up to 10 cm/year (Hutchinson, 1950). These deposits have been used to examine palaeoenvironments reconstruction for example, the guano geochemical studies, speleothem and cave sediments for reconstruction of paleoenvironment reconstruction, including stable isotopes δ18O, δ13C, , δ15N pollens and micro-charcoal radiocarbon age determination of guano, paleology and paleoecology, bat fossils (Forray et al., 2015, Royer et al., 2015, Wurster et al., 2017, Onac et al., 2015, Stoetzel et al., 2016, Widga and Colburn, 2015, Campbell et al., 2017).
The purpose of this study was to reconstruct environmental change and climate change in Kurdistan province using multi-proxy data derived from geochemical studies (LOI, Oxides, major and trace elements and statical data) derived from a precisely 14C-dated bat guano and cave sediment recovered from kolatarika Cave.
Study site Kolatarrika (mean dark cave) Cave, located in the Ghalojeh Village (Divandarreh city, Kurdistan province). The cave is located at 1910 m a.s.l. in a small karst area. Kolatarrika Cave develops in Oligo-Miocene limestones (Qom Formation), has a total length of 56 m, and no water flows along its passages.
Sampling A 160-cm guano and sediment core were taken by manually pushing an aluminium tube into a vertical wall deposit in the main guano accumulation is located in the Bat Room towards the end of the cave. The core was sampled at 2 cm ± 2mm intervals for geochemical analysis (73 samples) Samples for 14C dating were collected at irregular intervals based on changes of the guano and sediment texture.
Chronology Four accelerator mass spectrometry (AMS) 14C measurements on bulk guano and bulk sediment samples was obtained from the Poznan Radiocarbon Laboratory (Poland) (Goslar et al., 2004),. The AMS 14C dates were then calibrated into The calendar Year Anno Domini (Cal AD) and Before Present (Cal BP) using OxCal4.3.1 software (Ramsey et al., 2013) using the IntCal13 (Reimer et al., 2013) a calibration curve. In the current study, we established the age-depth models using The Bacon2.2 code (Blaauw, 2010, 2011, 2013) running in an R software environment (Team, 2010).
Geochemical analysis X-ray fluorescence (XRF) method was used to determine the Major oxides, trace elements and loss on ignition (LOI).
Statistical analysis Basic statistics including, Correlation coefficient, Cluster analysis, Principal Component Analysis was carried out by using the Paleontological Statistics software (Hammer et al., 2001).
Based on the age-depth model supported by four AMS radiocarbon dates, the sediment layers (85-160 cm) deposited between 4399 yr cal BP and 5686 yr cal BP and the guano deposit (85-0 cm) accumulated between 4399 yr cal BP and the present. The results of statistical studies show that there is a positive correlation between LOI in guano layers with Na2O, MgO, K2O, MnO oxides and Cl, As, Cu, Ni, Pb, and Zn, indicating that these oxides and elements are biological and originated from guano and there is a negative correlation between LOI with SiO2, Al2O3, Fe2O3, CaO, TiO2, P2O5 oxides and Ba, S, Zr, Y, V, Rb elements, indicating that these elements originated either outside of the cave or weathered by surrounding environments.
In the sedimentation layers there is a positive correlation between SiO2, Al2O3, K2O, TiO2, Fe2O3, Ba, Co, Cr, Nb, Pb, Rb, Sr, V, Y, Zr, all of these elements and oxides Have a negative correlation with CaO.
The results of cluster analysis for guano layers show that the two groups of elements can be detected; in group1: (As, LOI, Pb, Cl, MnO, K2O, MgO, Na2O, Ni, Zn) and in group2: (Nb, S, CaO, Sr, Mo, Cu, Ce, Cr, Co, Fe2O3, SiO2, Rb, V, TiO2, Zr, Al2O3, Ba, Y, P2O5). The results of cluster analysis for sedimentary layers show that the two groups of elements can be detected; in the group1 (Mo, MnO, MgO, Zn, Cl, As, Na2O, CaO, P2O5 Ni, S, LOI) and in the group2: (Nb, Sr, Cu, Ce, Cr, Co, Fe2O3, SiO2, Rb, V, TiO2, Zr, Al2O3, Ba, Y, Pb, K2O).
The results of four AMS radiocarbon dates, The age of the sequence of sedimentary layers and bat guano in Kolatarika Cave shows between 1955 cal yr AD and 5686 cal yr BP. The result of this study shows that between 5513 and 5814 yr cal BP, the region had a warm and humid climate and warm and dry climate between 4400 and 5513 yr cal BP. The bats have been gradually settled in Kolatarika Cave with the improvement of the environmental conditions, that is, the increase in humidity and temperature around 4399 cal yr BP. The highest bat accumulation was from 608 to 1122 cal yr BP (828-1342 cal yr AD), linked to the medieval climate anomaly (MCA) or the medieval warm period (MWP), which peaked at 835 cal yr BP (1115 yr cal AD), it coincided with the Seljuq dynasty in Iran. This indicates that the area has a warm and humid climate during this period. After this period, about 380 to 191 yr cal BP, linked to the Little Ice Age period (LIA), the bat accumulation in the cave has gradually diminished due to the cold climate. The lowest accumulation was 291 yr cal BP (1659 yr cal AD), which indicates that the area has a cold and humid climate. This phase, also linked to the Maunder Minimum period when sunspots became exceedingly rare and it has coincided with the Safavid dynasty in Iran. After this period gradually increasing the bat accumulations in the cave when local temperatures increased. The results show that bat guano is a very useful archive for reconstructing paleoenvironments similar to other proxies (tree rings, ice cores, lake and river sediments, loess, and glacier evidence) and are valuable resources in areas where no other paleo proxies are available.

Aeolian deposits are important palaeoclimate archives, partly because they are direct records of past atmospheric circulation (An et al. 2012). Distinguishing aeolian signature from lacustrine sediments is important for understanding the frequency and timing of palaeostorms. Efforts have been invested on deciphering aeolian records from lacustrine sediments in the United States (Dean 1997; Parris et al. 2010), Greenland (Mayewski et al. 2004), New Zealand )McGowan et al. 1996( and Japan )Xiao et al. 1997) providing a continuous record of Holocene aeolian activity.
Sistan Basin is a remarkable environment to study Aeolian activity changes in eastern Iran – southwestern Afghanistan. The area is one of the driest regions in the world whose sparse water resources and fragile ecosystems are very sensitive to climate change. In moist periods, fluviolacustrine and palustrine conditions are dominant while in dry periods, aeolian activities prevail. Hence, variations of aeolian deposits in sedimentary successions could be a useful tool to evaluate palaeoenvironmental conditions over the Sistan Basin during the Holocene.
Material & The closed depression of Sistan, lying on the Iran-Afghanistan border, contains four shallow basins (mean water surface at about 471m asl) that receive the discharge of Hirmand River. Sistan is located whitin the Asian part of the desert belt of the temperate subtropical zone of northern hemisphere, with a semi-desert climate (Whitney 2007). In late spring, throughout summer and early autumn the Sistan basin is dominated by the northerly “wind of 120 days”. The winds are related to the north–south pressure gradient between a persistent cold high-pressure system over the high mountains of the Hindu Kush in northern Afghanistan and a summertime thermal low-pressure system common over the desert lands of eastern Iran and western Afghanistan as a result of sustained surface warming (Alizadeh-Choobari et al 2014).
Two cores of H1 and H2 (6.2m and 6.8m long) were retrieved using a Cobra vibra-corer in west of Kuh-i Khawjeh in the dry lake bed Hamoun-e Hirmand in the Sistan Basin. Magnetic susceptibility (MS) determination (using a MS2C Bartington magnetic susceptibility meter), analyzing features of grain-size frequency curves (using a FRITSCH laser particle sizer) and petrography were conducted on sediment samples.
A bulk sample was selected from the lower half of the core H1 for radiocarbon dating. The calibrated date suggests late-glacial age for lower parts of the core H1 (13.5 ka).
Discussion of Results & The core lithology generally consists of clayey silt, silt and sandy silt layers. Based on basic sedimentological data, MS and sediment color we have recognized three main facies, A (lateglacial - early Holocene), B (early- mid Holocene) and C (late Holocene).
Since the late-glacial, the climatic regime of interior west Asia has been under the influence of various atmospheric circulation patterns and intensities (Fleitmann et al. 2007). High pressure cells of the Siberian Anti-cyclone (Siberian High: SH) from the north, low pressure cells belonging to the Indian summer monsoon (ISM) from the south, and mid latitude westerlies (MLW) governed the regional climate during thid period.
Data revealed that during the lateglacial - early Holocene, dominance of low pressure system of ISM on Sistan Basin and the western Hindu Kush provided a moist environment with less wind action. As shown by primary modal peak of grain-size distribution curves (20-30 µm), massive clayey silts with low MS (4.2 - 5.2 ×10-4 SI) and abundant plant remains, charophytes and carbonate shells in facies A are deposited in a highly productive lake with no signs of wind action. This period is also characterized by weakening MLW as well as elevated sea surface temperature in Atlantic Ocean and Arabian Sea. In addition, this humid period in the Sistan Basin is concurrent with the early Holocene long-term weakening of SH, inferred from increases in concentration of Kþ in GISP2 ice core (Mayewski et al. 2004) causing dramatic decrease in north-south pressure gradient between the Hindu Kush Mountains in northern Afghanistan and the desert lands of the Sistan Basin. High solar irradiance and weakening and northward migration of territory influenced by the SH also pushed the ISM domain northward (Mayewski et al. 2004) affecting Sistan catchment basin.
During the early- mid Holocene gradual weakening ISM (Sirocko et al. 1993) in addition to strengthening SH and MLW (Bradbury et al. 1993) caused dominance of severe wind storms in Sistan, as shown by modal peak more than 100 µm in facies B. During the mid-late Holocene, episodic high aeolian inputs in the basin by high energy dust storms comparable with the present day “winds of 120 days” are evident. Traces of palaeostorms during this time is evidenced by high oscillations of MS and presence of some sand-bearing lacustrine sequences in both cores. During this period, southward migration of ITCZ led to weakening of the ISM (Fleitmann et al. 2007), and consequently drought periods in Sistan Basin and semi-arid conditions over NW Himalaya (Dortch et al. 2013). Establishment of a high pressure gradient between the Sistan depression and the high Hindu Kush Mountains caused the occurrence of severe and frequent dust storms over the area.
Our results suggest that the late Holocene in the Sistan Basin (facies C3) was characterized by frequent changes in MLW and SH activity. Palaeoclimatic records show since the mid Holocene to the present time, the climate of Sistan and its catchment area more or less oscillated around a steady state comparable with modern situations (Hamzeh et al. 2016). During this time, the hydroclimatic regime and Aeolian activity of the Sistan Basin and NW Himalaya have been mostly governed by MLW-associated precipitation. Periods of prolonged droughts are indicated in proxy records of NW Iran such Lake Neor (Sharifi et al. 2015), presumably consistent with high MS values in our record. It is possible that weakening of ISM, along with distal influences of the MLW during the late Holocene exposed the Lake Hamoun basin to frequent droughts. Frequent lake level fluctuations show unstable climate of the Sistan Basin during mid to late Holocene with frequent wind storms.

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.

Paleozoology of Yafteh and Kani Mikaiel caves in center and northwest of Zagros Mountains led to the identification of small mammal's assemblage. Taxonomic determination revealed inclusion of four orders of small mammals including: order Rodentia with families of Muridea, Cricetidae, Calomyscidae, Dipodidae; order Lagomorpha with two families of Ochotonidae and Leporidae; order Soricomorpha with family Talpidae, and order Carnivores with family Mustelidae. These remains were recovered after systematic excavation in these caves. Radiocarbon analysis of these remains showed the oldest sample belonged to Yafteh cave with 35,000 BP. and Pleistocene period, whereas, Kani Mikaiel cave covered the periods from lat Pleistocene (19,000 BP.) to Holocene (17, 00 BP.). Geochronology analysis of Kani Mikaiel sediments showed that the lower layers of this cave belonged to the last glacial age in Pleistocene which gradually has been replaced by the warm weather in Holocene period. With continuing of this weathering varying, faunal spectrum of Pleistocene and Holocene periods has been migrated in cold and warm phases or more spread. The aim of this research, are the study of small mammal remains of Yafteh and Kani Mikaiel caves in center and northwest of Zagros mountains and the research about the study of paleobiodiversity, paleoenvironment conditions and the evolution of microvertebrate on the Iranian plateau.

The Persian Gulf has an area about 240000 km2, considered as the northern part of the counterclockwise movement of Arabian Plate and as a recent example of Holocene carbonated sedimentary environment in dry (arid) climate. The basin volume, regarding to its average depth (36m), is estimated about 87,000km3. The present study was done in order to examine the sea level changes and determine the rate of sedimentation of Holocene deposits in the northeast of Persian Gulf. A complete and undisturbed core from the Holocene deposits (1070 cm length) located in the south of Rajaee port in theHormozgan province was prepared. Following the exact description of this core, based on the objective observations, 52 samples were taken according to the facies divisions and they were sedimentologically and geochemically tested. The granulometric analysis, mineralogy by XRD method, abundance percentage of elements by ICP-OEC device and polarograph, percentage of organic matter by the Rock Eval device, percentage determination of carbonates by automatic calcimeter device were done for all samples and 10 samples were dated by 14C AMS method. The granulometric results indicated that most of the deposits are mud containing sand and gravel. The gravels are mainly related to shell fragments. The amount of carbonates varies from 17 to 84 percent. The silisiclastic deposits include quartz, feldspar, muscovite, pyroxene and clay minerals such as kaolinite, chlorite, montmoryonite, illite and paligorskite. The chemical and biochemical sediments are mainly calcite, dolomite and aragonite. The percentage of organic matter contained in the sediments varies from 0.02 to 0.13. The variation curve of calcium and strontium, which indicates intrabasinal sediments, is correlated to sea level changes in combination with objective evidences such as grain size, sediment type, and amount of organic matter, texture and structure of sediments. The abundance of most elements especially Al, Mg, Mn, Cr, Ba with continental origin, revealed a reversed relation with the sea level variations. In addition, two significant phases of rapid transgression have occurred from 6800 to 3700 and from 9300 to 7900 years ago. The dating results showed that the average rate of sedimentation in the study area is about 1mmper year 966mm/ka).

The Dehshir fault system (DFS) including six fault segments forms the western border of NS-striking active dextral strike-slip fault cutting the Sanandaj-Sirjan, Uromieh-Dokhtar magmatic arc, and Central Iran. This active fault system right-laterally offset Eocene volcanic rocks and Quaternary alluvial fans. Geomorphic evidence implies the activity of the DFS in the Late Quaternary, and paleoseismic investigations revealed seismic movements along the Marvast fault segment during the Late Pleistocene and Holocene timescales. In order to unravel the seismic history of the DFS over the intermediate geologic (103 105- years) time scale, and based on the morphotectonics and sedimentarystratigraphic properties, three paleoseismic sites have been selected along the 35-km-long stretch of the Marvast fault segment. The southern site (Harabarjan) shows steep fault branches of N140±10º strike with sub-horizontal striations in dextral component. Another trench has been excavated at the North Marvast site whitin the Late Pleistocene-Holocene alluvial and colluvial deposits.Optically stimulated luminescence (OSL) analysis of loose, quartz-rich deposits yielded an age of ~72 ka for the oldest exposed sediments. Paleoseismic stduies along the Marvast fault segment provide evidence for the occurrence of several large seismic events associated with surface ruptures along the DFS. The chronology of the paleoearthquakes on the Marvast segment indicates that at least 7 large (≈Mw > 7) earthquakes occurred in the last 43 ka with an average recurrence time of 3650±150 years. The most recent earthquake, event I, occurred ~2200 years ago, which associated with 2-4 m of dextral slip and >40 km surface rupture along the Marvast fault segment. These investigations are compatible with the lack of destruction in the Marvast historical (~1300 years) castle, located <10 km east of the DFS. Seismic pattern of the Marvast fault segment could be classified in three temporal clusters and two deformation spans: 1) with significant seismic activities; and 2) with small seismic activities or aseismic. Assuming such a seismic pattern remains similar until the next seismic cycle, the Marvast fault segment is experiencing the last seismic cluster. Considering the shortest time interval between two successive earthquakes (2000 years) may indicate the immennet threat of another destructive earthquake along the Marvast fault segment.

Considering the economic importance of this region, for the first time some studies on superficial sediments (deposits) foraminifera were carried out in this region. Purpose of these studies was to investigate effect of environmental changes on foraminifera and to use them as bio-indices in diagnosis of contaminations. In the studies regarding foraminifera, 12 genus and14 species were identified and foraminifera with hyaline lime shell had the greatest frequency. The main identified collection is: Ammonia beccarii Linne.And the species accompanying this collection are: Amphistegina lessonii, Elphidiom crispum, Elphidiom craticulatum, Triloculina tricarinata, Quniqueloculina seminulum, Ammonia parkinsoniana, Eponides repandus, Dendritina ambigua After foraminifera with hyaline lime shell, foraminifera with selenosis progeny shell were ranked next in terms of frequency. However, foraminifera with agglutinated shell were not observed in this region. In general, the obtained results from mineralogy studies on deposits of the ebb and flow area is the evidence that major part of the sediments are related to continental environment of the detrital deposit type. In section ecological studies, water's physicochemical factors are measured. Based on these studies,increase of water's temperature and salinity results in decrease of solution oxygen in water and water's acidity degree. However, in general, water's acidity fluctuation is slight and insignificant. The most importantphysicochemical factor affecting development of foraminifera is amount of solution oxygen in water which controls their frequency and diversity. Precipitation of oil carbohydrates and other contaminators produced by petrochemical activities in the region ruins the bio-environment, reduces solution oxygen, and gives rise to release of heavy and toxic metals (mercury and lead) from solid state to liquid which leaves numerous negative effects on marine and environmental ecosystem.

The evaluation of seismic potential along the Dehshir fault with 550-km length (accounting of northern and southern splays) is critical thanks to that more than 3.5 million people live in cities and towns located at vicinity of the fault. The Dehshir fault is considered as westernmost limit of N-striking dextral strike-slip faults set that slice Central and eastern Iran. Due to the lack of large recorded earthquakes (instrumental and historical) in Central Iran, access to seismic potential of active faults by studying the earthquake catalogs seems to be impossible. No instrumental earthquake has been recorded greater than mb 4.7 around the Dehshir fault and also historical data shows no evidence for occurrence of large earthquake around the fault. No sign of destruction in Marvast historical castle (at a distance of less than 10 km far from the Dehshir fault) built in Islamic period (~700-1250), shows any remarkable seismic activity until 750-1300 years ago. However, several evidence of geomorphologic markers such as drainages, gullies, streams and alluvial fans offsets, represent activity of the Dehshir fault in Late Quaternary. Geomorphic evidence at Marvast and Harabarjan sites record dextral - slip on the Dehshir fault during the Late Pleistocene-Holocene as major movement with minor dip - slip component. Rake of the fault movement has been considered for assessing to amount of horizontal and vertical slip rate on the Dehshir fault. This value in the North Marvast site has been calculated ~10 degrees and according to right-bank offset on the Marvast river is ~7 degrees with horizontal and vertical displacements of 13 m and 1.5 m, respectively. Combining cumulative offset markers with OSL dating implies the Dehshir fault in Late Pleistocene-Holocene time period slips at horizontal and vertical components about 1±0.3 and 0.1 mm yr-1, respectively. We observed a minimum dextral offset along the Marvast segment in west of Harabarjan about 2 m that allows assuming the related magnitude and date of most recent large paleoearthquake on the Dehshir fault on the order of Mw 7 and 2000 years ago, respectively.