جستجوی مقالات مرتبط با کلیدواژه « granulometry » در نشریات گروه « علوم پایه »

Land subsidence is one of the environmental hazards that are detrimental consequences cities, facilities, communications facilities and agricultural land in the long term. This research has done through field works such as sampling plains deposits, measuring the thickness of stratifications, the type of formations, granulometry and drawing related Charts with Imaging, reviews documents, experimental and laboratory methods. The maximum thickness of alluvial deposits accumulated (Quaternary) is more than 160 meters according to geological section at the highest level subsidence in Hadishahr plain and in Harzandat plain is more than 200 meters. Quaternary alluvium huge with large stones, associated with strong floods, especially in the early Holocene and violence roughness in the past is interpreted and explained. The thickness of materials along the Pir Eshagh-Zal valley from 20 meters in the village of Pir Eshagh is variable to 110 meters in the East Village of Zal. In fact, Harzandat , Hadishahr and Gollfaraj plains with an area 165 km2, are Graben cumulative plains where are develop and evolution within Horst fault zones. The form of structural stratifications of the plain and Horst following the directions of the lateral and vertical forces along with north-west folding have found faulting and due to tectonic uplifting and sinking the level of local area, the main channels have been cased the typical fluvial terraces at the top of the alluvial fan deposits with drilling and digging

Information of coastal sediment granulation plays an important role in conducting studies related to the organization and analysis of coastal water behavior. The purpose of this research is to identify sedimentary properties and determine the origin and identify the factors of enrichment of chemical elements in shallow sediments of Chabahar coasts. The research methods were included library studies, field operations, laboratory, processing and conclusions. Elemental analyzes were performed by ICP-OMS and ICP OES methods. In order to obtain accurate estimates of particle size distribution, granulometry steps, statistical calculations and plotting were performed with Sediment Size sedimentology software. SPSS23 software was used to classify the elements, calculations related to correlation coefficient, cluster diagram and factor test. In this research, 12 sedimentary facies including two groups of sandy facies and mud facies were identified. The results show that a dual sedimentation regime prevails, which means that when the sea level rises, carbonate deposition occurs and destructive deposition stops, and when the sea level drops and destructive particles enter Sedimentary basin, carbonate deposition is stopped and destructive deposition takes place. Also, the order of increasing the concentration of heavy metals in the sediments of the study area is Cd <Cu <Pb <Zn <Ni <Cr. Chromium, nickel and lead with average concentrations of 96.9, 55.3 and 11.2 have the highest concentrations in Moddy sediments. Elemental enrichment in the sediments of the study area is related to four sources: geogenic (Terrestrial), biochemical, anthropogenic (Environmental) and chemical (Evaporative).

Rip current is one of the most important phenomena in coastal areas. Due to the importance of rip currents, which are directly related to human lives, they have been studied and evaluated from different approaches. This research aimed to determine rip currents' effect on the sediments' granulometry through sampling of the sediments in the rip channel and its surrounding area on the Caspian Sea coast. In this study, one station was selected in Noor city, Mazandaran province. Various factors such as lack of private property, easy access, lack of human manipulation, and knowledge of drowning rescuers about the location of the drowned were considered in the selection of the station. Then, in two seasons, winter (December and March) and spring (May and June), with the help of lifeguards and existing signs, the location of the rip canal was identified in the station and at least three sediment samples were taken from the channel and three samples from the environment around the channel using Grab. In addition, the water depths were estimated in the sediment sampling points using Echo sounder. The sediment samples were transferred to the laboratory and sediment particles were separated based on grain size using a shaker and multiple sieves (with a network mesh of 30, 50, 60, 80, 100, 140, 200, and 230). The data obtained from the shaker were entered into the excel page of GRADISTAT software and the characteristics of sediment samples including mean diameter (D50), mean degree of sorting, skewness, and kurtosis were calculated by Folk and Ward method. All sediment particle characteristics were compared between the rip channels and surrounding areas using an unpaired t-test. The results showed that among the sedimentation characteristics, no significant difference was observed between the channel and surrounding areas in the degree of sorting and kurtosis neither in the winter nor in the spring. In addition, the results of granulometry showed that D50, mean particle size, and skewness of grain distribution of sediment particles were significantly different between the rip channel and the surrounding areas in the spring. The highest amount of D50 (with an average of 185.8 mm), mean (with an average of 202.7 mm) and skewness (0.48) of sediment particles were observed in the rip channel. These significant differences in particle characteristics were not observed in the winter samples probably due to the turbulent weather and sea currents. In addition, the average water depth of the rip channel was obtained at ca. 120 cm, while the average water depth of surrounding areas was estimated at ca. 85 cm. Therefore, we can state that some of the channel sediments have been removed by water flow in the channel. The higher energy and velocity of the flow in the channel than the surrounding environment has caused the transfer of sediments. On the other hand, sediment transport is directly related to other parameters such as sediment grain size. The present study showed that rip channels have sediments with significantly different characteristics than the surrounding sediments. The higher flow rate in the rip channel probably causes the removal of some fine-grained sediments and is not able to remove coarse-grained sediments. Removal of fine-grained sediments causes a change in the texture of the remaining sediments towards larger grains and these changes have caused a significant granulometric change between the rip channel and the surrounding environment, especially in the spring.

The origin and geochemistry of the sediments that make up the Khuzestan plain as one of the key areas of southwestern Iran has always been discussed. Detailed geochemical studies of these sediments, in addition to determining their origin, can provide appropriate information about weathering, erosion, ancient tectonics and environmental pollution in the Khuzestan plain. In this research, after library studies, 276 different points for field surveys were determined with the help of satellite images. Sampling was done from designated points in spring and summer when soil moisture was minimal. The collected samples were sent to the Central Laboratory of Tehran Geological Survey for geochemical experiments after sizing by sieving device of Ahvaz Center of Geology. Findings from sediment granulometry studies show that most of the grains studied have bad to very bad sorting and contain about 70% of particles equal to and larger than silt. In addition, the findings of geochemical studies show that CaO, SiO2 and Al2O3 are the most abundant oxides in these sediments and Ti, Zr, V, Ce and La are also the most abundant by-products. The classification of the sediments based on geochemical indicators shows that these sediments are mainly in the range of Vaki and iron-bearing shales. It is noteworthy that the sediments of this plain are enriched with elements such as As, Bi, Cd, Co, Cu and U, which need to be studied more closely. The results of the study of these findings show that the deposits of the Khuzestan Plain, often in a short time with a high-energy environment. These conditions are more evident in the northern part of Khuzestan province, which is often composed of larger grain particles than the southern parts of Khuzestan province. In addition, geochemical studies performed to determine the ancient tectonics of Khuzestan plain sediments show that the primary origin of these sediments were Continental Island Arc and Active Continental Margin, which corresponds to the Zagros tectonic conditions and can indicate the primary origin of this Sediments are from Sanandaj zone of Sirjan (especially in the northern parts of Khuzestan province). Environmental studies on the collected samples show that these sediments are in a warning state due to the presence of elements such as As, Bi, Cd, Co, Cu and U.

In the Azarbayeghan Gharbi Province, Bozesina and Dalamper mountains are located through Oshnavieh and Uromieh devisions and near the frontiers of Iran, Iraq and Turkey. This area as mountainous curve are overlook to Margavar plain. Dalamper summit which is located in the north of Bozsina with 3 kilometers distance. Bozesina is located in the northern section of Zagros Mountain Range and through the Sanandaj-Sirjan geologic zone, which is fractured by the pressures of Arabian Tectonic plate on western areas of Iran. These glaciers are begun from 3483 m asl and its components are continued to 2500 m asl. There are some small and big cirques and many glacial valleys in the vicinity of Bozesina. In this study, we have investigated the glacial evidences of Bozesina and Dalamper mountains. Based on synoptic data of Uromieh and Oshnavieh’s weather stations in the period 1995-2012, we have deduced that annual rainfall in this region is 325 to 448 mm, 68% of the total precipitation occur in cold period, the mean of temperature is C 11º and snow cover on the mountain can remain until the late September. The study area is mainly influence of western moist air masses from Mediterranean Sea and Atlantic Ocean. Snow melting provides water flows in permanent tributaries of Baranduz River.
Data and The interested area was initially extracted from topographic maps, scale of 1:25000, Digital Elevation Model from Aster sensor and observation in a field campaign from late August to early September in 2012-2014. Some samples were taken from the valleys’ sediments of the mountain and sediments’ sites were recorded by GPS. At first, some large and small cirques have been detected in this study area that they have extended in the northeast. This field work was very laborious in the harsh insecure and inhospitable region. Through the field of studies, we detected some cirques with unique characteristics. In Bozsina glacier valley, there are many evidences of glacial sedimentation in altitudes of 2600-3005 meters. There are many alluvial terraces downstream the rivers of Baranduz river. These terraces indicate the changing of climate in the past of the region. From detection of their sources we could achieve, 50 coarse grains have been prepared for roundness and sphericity analysis and 200 g of each sample for granulometric analysis.
The regression model of Temperature - height and coincidence with field’s evidences have created three domains on the slopes of the Bozsina and Dalampr mountains. Some large cirques have been presented in the cirque realm spatially in the slopes of Bozesina. The most obvious Bozesina cirque includes three cirques. The cirque which is located in the northeast is larger than two others. Also, there are some cirques exists between Dalampr and Bozesina such as Myrgehfal; furthermore some big glacial valleys be on the slopes of dalamper and Bozesina Mountains. Three to four river terraces can be seen in downstream river of Baranduz. These terraces indicate that the changing of past climate in this region. Heavy snowfall in Dalamper Mountain is continued from October to May in this region and the rivers are originated from the mountain and left some sediments as alluvial fans and terraces. Snow melting at the end of ices age produced powerful flows draining and these materials evacuated from mountainous’ area. The investigation indicated that these sediments of the terraces are very angular grains and originated from Dalamper and Bozesina Mountains.
The glacial periods have left their traces and evidence such as cirques, valleys, craved lines on hard rocks. The evidences of the effecting of glacial erosion indicate the prevalence and dominance of ice and permanent snow. Accumulation effects of the glaciers include types of some moraines. These aforementioned explanations represent peri-glacial areas or freeze- thaw activity in quaternary. The results of field observations and sedimentology analyses indicated that in the last cold period the glaciers were dominant in that region and remained their traces, cirques and glacial valleys. The comparison between the roundness and sphericity coefficient with the researches of Powers (1953) demonstrated that the particles are relatively angular, stretched and not completely rounded and these indicate their durability and movements inside the ice. Given that the samples were taken from glacial valleys, with increase in distance from Bozesina cirque, 1 any significant differences in these samples. This is the typical of movements of glacier tongue in glacial period.