seyed mohammad zamanzadeh
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در این مطالعه ارزیابی ژئو شیمیایی سنگ مادرهای مستعد در میدان فروزان بر اساس آنالیزهای ژئوشیمیایی پیرولیز راک اول و انعکاس ویترینایت انجام گرفته است. برای این منظور 101 نمونه خرده حفاری جهت پیرولیز راک اول و 11 نمونه جهت آنالیز انعکاس ویترینایت از سازندهای گورپی، سروک، کژدمی، داریان، گدوان، فهلیان بالایی و نیریز در یکی از چاه های میدان فروزان، به منظور تعیین کمیت، کیفیت و بلوغ مواد آلی موجود در سنگ های مادر استفاده شده است. نتایج نشان داد که سازندهای مورد مطالعه میزان مواد آلی در محدوده ضعیف تا خیلی خوب را دارا می باشند. مواد آلی موجود در سازندهای گورپی، سروک، فهلیان بالایی و نیریز بیشتر در محدوده کروژن نوع III قرار دارند که به بلوغ کافی برای تولید هیدروکربن نرسیده اند. با این وجود، مواد آلی سازندهای کژدمی، داریان و گدوان بیشتر از کروژن نوع II تشکیل شده که ابتدای بلوغ قرار داشته و هنوز وارد پنجره نفت زایی نشده اند. بنابراین می توان اظهار کرد که سازندهای کژدمی، داریان و گدوان مستعد سنگ مادر مناسب در میدان فروزان به حساب می آیند. با این وجود، در میدان مورد مطالعه هنوز هیدروکربنی تولید نکرده اند ولی همین سازندها یا معادل آن ها در بخش های ژرف تر حوضه می توانند به عنوان سنگ مادرهای فعال عمل کرده باشند.کلید واژگان: سنگ مادر, پیرولیز راک اول, انعکاس ویترینایت, میدان فروزانGeochemical evaluation of potential source rocks in Foroozan Field is carried out based on Rock-Eval pyrolysis and vitrinite reflectance analyses. For getting the results, 101 samples for Rock-Eval pyrolysis and 11 samples for vitrinite reflectance analysis were selected from Gurpi, Sarvak, Kazhdumi, Dariyan, Gadvan, Upper Fahliyan, and Neyriz Formations cuttings. The results were used to determine the quantity, quality, and maturity of organic matter and show that the average content of organic matter in the studied Formations range from poor to very good. According to the interpretations, the type of organic matter in the Gurpi, Sarvak, Upper Fahliyan, and Neyriz Formations are mostly type III kerogen, and they have not reached to appropriate maturity. However, the Kazhdumi, Dariyan, and Gadvan Formations mostly show type II kerogen which is not mature enough and have not yet entered the oil window. This group of formations can be considered suitable source rocks in the Foroozan field. Despite these formations are at the onset of the oil window, they have not produced hydrocarbon yet. Therefore, these formations or their equivalents in the deeper parts of the basin could be considered as active source rocks.Keywords: Source Rock, Rock-Eval Pyrolysis, Vitrinite Reflectance, Foroozan Field
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امروزه استفاده از روش های یادگیری ماشین در تخمین داده های پتروفیزیکی کاربرد فراوانی دارد. در این مطالعه سعی شده لاگ صوتی برشی از دیگر داده های پتروفیزیکی با روش های یادگیری ماشین محاسبه و با داده های صوتی حاصل از مغزه مقایسه شوند. برای این منظور در ابتدا برای نرمال سازی داده ها روش های محاسباتی انحراف معیار، جنگل انزوا، حداقل کوواریانس و فاکتور پرتی استفاده و مورد مقایسه قرار گرفتند. با توجه به مقدار داده های حذفی و نمودارهای جعبه ای رسم شده، روش انحراف معیار برای نرمال سازی انتخاب شد. روش های یادگیری ماشین استفاده شده شامل جنگل تصادفی، رگرسیون چندگانه، رگرسیون تقویت شده، رگرسیون بردار پشتیبان، K نزدیک ترین همسایه و پرسپترون چندلایه می باشند. رگرسیون چندگانه پایین ترین اندیس ارزیابی (94/0 = R2) را داشت درحالی که رگرسیون جنگل تصمیم گیری با اندیس ارزیابی برابر 98/0، بالاترین همبستگی بین لاگ های صوتی برشی تخمین زده شده و لاگ صوتی اصلی را داشتند. بنابراین برای تخمین نهایی از رگرسیون جنگل تصادفی استفاده شد و برای جلوگیری از کلیت بخشی یا بیش برازش داده ها، از تابع GridSearchCV هایپرپارامترهای بهینه محاسبه و تخمین نهایی انجام شد. لاگ صوتی برشی تخمینی، با داده های صوتی حاصل از مغزه قرابت بسیار بالایی را نشان دادند.
کلید واژگان: پایتون, تخمین, لاگ صوتی برشی, یادگیری ماشینMachine learning methods are widely used today to estimate petrophysical data. In this study, an attempt has been made to calculate shear sonic log (DTS) from other petrophysical data using machine learning methods and compare it with the sonic data obtained from the core. For this purpose, computational methods such as Standard Deviation, Isolation Forest, Min. Covariance, and Outlier Factors were used to normalize the data and were compared. Given the amount of missing data and box plots, the Standard Deviation method was selected for normalization. The machine learning methods used include Random Forest, Multiple Regression, Boosted Regression, Support Vector Regression, K-Nearest Neighbor, and MLP Regressor. Multiple regression had the lowest evaluation index (R2=0.94), while Random Forest regression had the highest correlation between the estimated shear sonic log and the original shear sonic log with an evaluation index of 0.98. Therefore, Random Forest regression was used for the final estimation, and to prevent data generalization or overfitting, the GridSearchCV function was used to calculate optimal hyperparameters and final estimation. The estimated sonic log showed a very high similarity with the core data.
Keywords: Python, Estimation, Shear Sonic Log, Machine Learning -
مجله پژوهش نفت، پیاپی 132 (آذر و دی 1402)، صص 117 -128سازندهای کنگان و دالان به دلیل عمق تدفین زیاد همیشه به عنوان مخازن گازی در نظر گرفته شده اند. این مطالعه به بررسی نوع سیال هیدروکربنی موجود در مخازن کنگان و دالان براساس تفسیر ژیوشیمیایی گاز محلول در گل حفاری همراه با ارزیابی پتروفیزیکی در یکی از چاه های حفاری شده دور از ساحل خلیج فارس پرداخته است. برای رسیدن به این هدف، مطالعه در سه مرحله صورت پذیرفته است. در مرحله اول ارزیابی پتروفیزیکی با فرض کل مخزن به عنوان مخزن نفتی انجام گرفت. در مرحله بعدی نوع سیال براساس تفسیر ژیوشیمیایی گاز محلول در گل حفاری با استفاده از روش های هاورث و پیکسلر شناسایی شد. نوع سیال نهایی براساس انطباق هر دو روش تعیین گردید. در مرحله آخر نیز ارزیابی مجدد پتروفیزیکی در بخش نفتی مستعد انجام گرفت. براساس تفسیر اولیه پتروفیزیکی، سه بخش نفتی شامل K1، K2 و K4 در مخزن وجود دارد. با این حال، براساس تفسیر ژیوشیمیایی گاز محلول در گل، دو بخش K1 و K4 گازی بوده و فقط بخش K2 حاوی هیدروکربن نفتی است. ارزیابی نهایی پتروفیزیکی بخش K2 به عنوان بخش نفتی، تخلخل مفید 6% و اشباع شدگی 29% را نشان داد. نتایج حاصل از این مطالعه آشکار ساخت که توجه به تفسیر ژیوشیمیایی گازهای محلول در گل حفاری در تعیین بازه مناسب مشبک کاری و همچنین انتخاب بخش های مناسب جهت انجام تست های مخزنی باعث کاهش هزینه و زمان نهایی حفاری خواهد شد.کلید واژگان: گاز محلول در گل حفاری, اندیس هاورث, پیکسلر, پتروفیزیک احتمالیPetroleum Research, Volume:33 Issue: 132, 2024, PP 117 -128The Kangan and Dalan formations have long been considered as gas reservoirs due to their deep burial history. However, this study investigated the type of hydrocarbon fluid in these reservoirs based on the geochemical interpretation of mud gas logging and petrophysical evaluation in the Persian Gulf. The study was conducted in three stages. Firstly, well logs were evaluated under the assumption that the reservoir is an oil-type reservoir. In the next step, the type of fluid was identified based on the geochemical interpretation of mud gas logging, using the Haworth and Pixler methods. The final fluid type was determined based on the integration of geochemical methods. In the last step, a petrophysical re-evaluation was done in the susceptible oil zone. According to the primary petrophysical interpretation, there are three oil zones including K1, K2 and K4 in the reservoir. Meanwhile, based on the geochemical interpretation of mud gas logging, K1 and K4 zones are gas type and only the K2 zone contains oil-type hydrocarbon. Petrophysical re-evaluation of the K2 zone (identified as oil-type reservoir zone) indicated an effective porosity of 6% and water saturation of 29%. The results of this study suggest that paying attention to mud gas logging interpretation when determining the appropriate interval for perforation and selecting the appropriate zones for reservoir tests can reduce drilling costs and time.Keywords: Mud gas logging, Haworth indices, Pixler gas ratios, Multimin method
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The presence of water resources, particularly rivers, significantly influences site selection. Throughout history, settling near rivers has brought numerous advantages, but it has also posed certain risks. This study focuses on the sub-basins southeast of the Caspian Sea. Initially, we explore the connection between the layout of ancient settlements and the drainage networks. Additionally, we analyze the relationship between flood risk and the settlement patterns of these ancient sites by estimating the flooding risk based on linear, areal, and relief aspects. This research marks the first time such an analysis has been conducted. The findings underscore the importance of proximity to rivers in site selection, with areas close to rivers with lower stream orders being the most favorable for settlements. The study reveals a decrease in the frequency of sites near higher stream orders in relation to flooding risk. Conversely, there is an increase in the frequency and density of ancient sites near the first stream orders and at greater distances from the rivers, coinciding with an elevated flooding risk in the sub-basins. These results indicate that the inhabitants of the southeastern areas of the Caspian Sea sub-basins were cognizant of the flooding danger and factored it into their decision-making when selecting settlement sitesKeywords: Geoarchaeology, Settlement Pattern, hydro geomorphology, Flood, Southeastern of the Caspian Sea
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پوسته زمین بر اثر عوامل زمین ساختی و حرکات فشارشی و کششی حاصل از آن به طور مداوم در حال تغییر و تحول است. تغییر در شکل نیمرخ طولی رودخانه ها یکی از پیامدهای تاثیرات زمین ساخت فعال بر شبکه های آبراهه ای است. در این پژوهش هدف اصلی بررسی تاثیر زمین ساخت فعال در قالب حرکات امتدادلغز و ترافشارشی گسل دامغان بر روی ساختار مورفولوژیکی ارتفاعات سیاه کوه در شمال دامغان است. بدین منظور با استفاده از اطلاعات ارتفاعی نقشه رقومی ارتفاع 5/12 متر راداری و با استفاده از الگوریتم D8 به استخراج آبراهه های منطقه پرداختیم و 2 رود اصلی بر سطح ارتفاعات سیاه کوه را مورد بررسی قرار دادیم. در این راستا از رابطه توان رودخانه برگرفته شده از دو متغیر اصلی شیب و مساحت زهکشی رود در قالب یک نمودار لگاریتمی به منظور استخراج پارامترهای تندی و فرورفتگی بهره گرفتیم. افزایش پارامتر تندی بیانگر بالاآمدگی رود در پاسخ به فرایش های فعال می باشد؛ درحالی که افزایش پارامتر فرورفتگی بیانگر عدم عملکرد فرایندهای زمین ساختی به شکل فرایشی و یا مقاومت کم سنگ بستر است. بررسی تاثیر فعالیت گسل دامغان بر روی ارتفاعات سیاه کوه با استفاده از رابطه توان رودخانه نشان داد که حرکات امتدادلغز و ترافشارشی گسل دامغان برجستگی سیاه کوه را در قالب ساختار یک خم گرفتاری با مورفولوژی فوربرگی درآورده است. هرجا رود بر سطح فوبرگ جریان دارد؛ مقادیر بالایی از پارامتر تندی را نشان می دهد و هر جا رود از سطح فوربرگ خارج شده و بر روی رسوبات سست کواترنری مخروط افکنه های اطراف جریان یافته از مقادیر پارامتر تندی کاسته شده و بر مقادیر پارامتر فرورفتگی افزوده شده است.
کلید واژگان: سیاه کوه, کواترنری, گسل دامغان, مورفوتکتونیک, نیمرخ طولی رودخانهIntroductionIdentification of active tectonics in an area and its effects on the morphology of landforms is one of the topics that has always been of interest to geomorphologists. Waterways are among the features that flow a wide range of landforms. These features are sensitive to lithological or tectonic changes and react quickly to these changes. The riverbed has been affected by these anomalies and the effects of these anomalies can be studied in the longitudinal profile of the river. In other words, waterways are active tectonic markers that give us information about the characteristics of a landform.
Materials and methodsThe study area is located in the south of the Eastern Alborz Mountains and is known as the Siah-Kuh Heights. This ridge consists of a set of dolomitic and sandstone rocks of Sibzar and Padha Formation and Damghan fault passes along it. The main purpose of this study is to investigate the morphological and tectonic structure of Siah-Kuh using steepness and concavity parameters based on the anomalies of longitudinal profiles of the rivers based on the uplift and subsidence axes. In order to calculate the rate of steepness and concavity of longitudinal profiles, the stream power low formula is used based on the two main parameters of drainage area and slope of river. This formula is based on a logarithmic plot of the slope and drainage area for which the appropriate regression line is determined. In this regression relation, the slope of the line is the concavity parameter and the intercept is steepness parameters.
Results and discussionThe extent of the Siah-Kuh heights among a series of young Quaternary sediments at a distance of 4 km from the main mountain front, the structure of the Siah-Kuh is similar to Foreberg forms. Damghan fault in this area has led to the intersection of Quaternary sedimentary strata related to the surrounding alluvial fans and by creating a transtensional position in the form of a set of trapped traps, the Siah-Kuh Foreberg has appeared as a restraining bend on the surface Which has led to the elevation of the central part and the relative subsidence of both sides of this structure. The eastern part of the Siah-Kuh Foreberg appears to have been covered by Neogene and Quaternary sediments. Its remnants have appeared in the form of deep gorges on the surface. One of the rivers flows on the main surface of Foreberg and the other flows in the drained or buried part of Foreberg. Both rivers have several knick points in their flow path, which are taken from the location of faults and lithological differences of the riverbed. The values of the steepness parameter for the main river and the gully show high values so that the value of this parameter is 121.4 for the main river and 119.96 for the gorges. In contrast, the depression parameter rate in both rivers shows very low and even negative values. (Main river: -0.18 and gorges river: -0.92). Since the sharpness parameter is directly related to the tectonic processes; It can be said that the values of this parameter in both rivers indicate the effect of active tectonics at the level of Foreberg.
ConclusionThe studies performed on the study area show that the two factors of active tectonics and lithology have a great impact on the morphological structure of Siah-Kuh Foreberg. Also, factors related to sedimentary flows originating from the uplands of the area have been effective in changing these landforms in the form of burial. Also, the results showed that the use of the method based on longitudinal profile anomalies of the river in the form of steepness and concavity parameters has an effective role in identifying erosion and subsidence axes related to tectonic situation of features in relation to their topographic changes. Slight difference in the amount of steepness parameter in gorges compared to the river on the main surface of Foreberg, especially in the first trends of both rivers, which show high values of steepness parameter with a small difference (1.44), Indicates the existence of an uplift axis in this area, which somewhat confirms the burial of a structure similar to the Siah-Kuh Foreberg under sediments.
Keywords: Siah-Kuh, Quaternary, Damghan Fault, morphotectonic, Longitudinal profile of river -
نشریه کواترنری ایران، پیاپی 27 (بهار و تابستان 1401)، صص 1128 -1147
ارتفاعات البرز شرقی واقع در شمال پلایای دامغان، به سبب وجود گسل های متعدد همچون گسل آستانه، دامغان، تزره و عطاری جزء نواحی فعال زمین ساختی ایران به شمار می رود. هدف اصلی در این پژوهش شناسایی تغییرات زمین ساختی و فرسایشی این بخش از ارتفاعات البرز و نواحی اطراف آن شامل پلایای دامغان در قالب پیدایش محورهای فرایش و فرورفتگی در طی کواترنری می باشد که منجر به شکل گیری لندفرم های متعددی شده است. در این راستا، از روش تحلیل و بررسی نقشه های همپایه و تفریقی برمبنای ناهنجاری های ایجاد شده در رده های آبراهه ای متاثر از فرایندهای فرایشی و فرسایشی فعال در کواترنری استفاده به عمل آمد. بررسی های انجام شده بر روی منطقه مورد مطالعه نشان می دهد که دو عامل زمین ساخت فعال و سنگ شناسی بر روی ساختارهای مورفولوژیک و لندفرم های منطقه تاثیر بسیار زیادی دارند. نتایج نشان می دهد که گسل های منطقه در طی کواترنری فعال بوده و با سازوکارهای متفاوت رانده و امتدادلغز که در برخی نواحی دارای جایگاه های تراکششی و ترافشارشی نیز بوده اند، مجموعه ای از لندفرم های فرایش یافته یا فروافتاده را در ناحیه دامغان به وجود آورده اند. برخی از این لندفرم ها نشانگر عدم تطابق ساختاری البرز متاثر از فعالیت گسل های ناحیه در ارتباط با عامل مهم سنگ شناسی می باشند.
کلید واژگان: لندفرم, گسل, نقشه همپایه, نقشه تفریقی, دامغانQuaternery journal of Iran, Volume:8 Issue: 27, 2023, PP 1128 -1147IntroductionDamghan area has been considered by earth scientists due to the existence of numerous active faults. These faults with slow and progressive movements have led to changes in the shape of landforms in the area. Even during the history, the activity of these faults led to major earthquakes such as Qumis earthquake in 856 A.D. This earthquake led to the complete destruction of Qumis province in present-day Damghan. Researchers in the area, including Hollingsworth et al 2010., have concluded that major faults in the area, such as the Astaneh and North Damghan faults, have ruptured during the Qumis earthquake. The changes in landforms and high potential of faults in creating seismic events indicate their continuous activity during Quaternary up to now. To study these changes, we need those features that are sensitive to tectonic and erosive events. Rivers are one of these features that react quickly to active tectonic and erosion changes. The main purpose of this study is investigation of the changes in landforms using anomalies in stream orders. Because there is a hypothesis that claims tectonic and erosive changes lead to irregularity in Strahler orders of streams. In this study we use isobase and differential map method to investigate this hypothesis.
Materials and MethodsSensitivity of drainage network to tectonic processes and geological contradictions leads to changes and irregularities in river orders. Isobase maps are extracted from information about the spatial classification of rivers and their elevation information in the environment. In fact, these maps show the relationship between the pattern of waterways and the topography of landscapes. Streams with the same Strahler order are formed by the same geological events, and most likely the same order is the same age. We can draw iso base maps for different stream orders. Early orders (1-3) are mostly more sensitive to tectonic events. These early orders due to flow along seams and fault gaps are representative of neotectonic. Rugged structures in the lithology of the region can limit the evolution and development of the early orders, and therefore in these areas the values of the isobase map increase. But isobase map of evolved orders can represent longer periods, such as the Quaternary or Pleistocene. Because evolved orders are formed over longer periods and are able to show older tectonic and erosive events. Differential maps are obtained from the difference in height between the maps of the evolved orders and the present day topography map.
Results and DiscussionExamination of the isobase map of the primary orders show that most of the values related to the map can be seen in the west and north of the region. These areas are based on mountainous structures. The high values of the isobase map in these areas indicate that the northern and western parts, affected by neotectonic activities and the development of fault gap and seams, have more primary orders of rivers. Because most of these primary orders are formed and developed along these levels of weakness. Resistant lithology of the area has also prevented the development of these orders. The highest value of them is 3830-2312 meters. The differential map prepared from the study area shows a wide range of positive values indicating uplift and negative values indicating subsidence. By examining these values, we can understand the features related to tectonics and geomorphology of various landforms in the region. The highest values of 1191 to 800 meters are related to the high mountain structures of Eastern Alborz in the north and west of the region. The decrease in the value of the differential map indicates the effect of tectonic subsidence on the morphological landforms of the region. The Astaneh pull apart basin in the western part of the region shows the amount of subsidence between -4 to -1 meters. Also, the southern playa of Damghan in the form of a concave foreland basin affected by active faults in the region shows negative values, which indicates the existence of a submerged basin with high sedimentation potential.
ConclusionStudies conducted on the area show that the two factors including active tectonic and lithology have a great impact on the morphological structures and landforms of the area. The results of isobase map and the differential map show and confirm this issue. The methods used in this study to investigate the tectonic activity of the faults in the area indicate their activity during the Quaternary. These faults have different mechanisms of thrust and streak slip which in some areas also have transtensional and transpressional position; they have created a collection of uplifted or concave landforms in Damghan area. The spatial relationship between different values from north to south in the prepared maps indicates the creation of an equivalent states between topographic growth and its destruction in lower altitudes. Based on the studies, we confirm that the preparation of isobase and differential maps can be a suitable method for studying and examining morphological structures. Also studies related to differential map show anomalies in drainage networks and uplift processes associated with active Quaternary landforms can be quantified by these maps. Using baseline and differential maps is one of the appropriate methods to study the Plio-Quaternary tectonics in an area. This study confirms the work of previous researchers based on the available information and documents related to the study area.
Keywords: Landform, Fault, Isobase map, Differential map, Damghan -
نیمرخهای طولی توپوگرافی نواری نیمرخهای (Swath)، از بهترین ابزارها برای به تصویر کشیدن تعادل طولانی مدت چشمانداز در پاسخ به تغییرات متقابل تکتونیک، سنگشناسی و اقلیم است. در پژوهش حاضر برای ارزیابی نقش تکتونیک فعال در تکامل چشمانداز از نظر بالاآمدگی و فرسایش، از نیمرخهای سوات در دو جهت موازی و عمود بر جریان کلی زاگرس در زاگرس شمال غرب استفاده شد. این نیمرخها با استفاده از مدل رقومی ارتفاع، مقادیر میانگین، حداکثر و حداقل ارتفاع، ناهمواری محلی و چارک اول و سوم را مشخص میکنند. همچنین محاسبه شاخص انتگرال هیپسومتری عرضی ارتقا یافته (THi*)، تغییرات هیپسومتریک را در عرض نیمرخ برجستهتر میسازد. نتایج نشان میدهد که در تمام مقاطع بهویژه مقاطع عمود بر زاگرس، مقادیر ناهمواری محلی زاگرس شکسته و چینخورده بالا است. در محدودههایی که مقدارTHi* افزایش یافته محدوده نزدیک به گسلها یا محور تاقدیسهای زاگرس چینخورده مقدار میانگین و چارک سوم به سمت منحنی حداکثر جابه جا شده است که این امر بر جوان بودن ناهمواری دلالت دارد. این مناطق، بر شبکههای زهکشی همراه با درههای پرشیب در حال حفر انطباق دارد؛ علاوه بر این، مقاطع عمود بر زاگرس که تغییرات سوات را در واحدهای مورفوتکتونیکی مجاور هم زاگرس مرتفع، زاگرس چینخورده و پیشژرفای زاگرس نشان میدهند، نسبت به مقاطع موازی با زاگرس امکان بهتری را برای مقایسه پارامترهای مذکور فراهم کردهاند. در مجموع، ناهمواری محلی زیاد و تغییرات گسترده منحنیهای نیمرخهای سوات نشان میدهد که زاگرس، چشماندازی تقطیع شده توسط فرایندهای رودخانهای است که به سمت قسمتهای جنوبیتر منطقه، شرق گسل اصلی زاگرس و غرب گسل جبهه کوهستان کاهش محسوس ناهمواری محلی و ادغام منحنیها به چشماندازی پایدار با حفر کم تا متوسط تغییر میکند.
کلید واژگان: تکتونیک, فرسایش, زاگرس شمال غرب, ناهمواری, SwathIntroductionInteraction between tectonic and surface processes to create and dissect topography is the main area of emphasis in tectonic geomorphology (Burbank & Anderson, 2001: 2). Growing usage of GIS and DEMs have improved techniques of landscape analysis in Tectonic geomorphology. One of the widely used approaches in tectonic geomorphology to recognize general elements on landscape related to tectonic is analyzing topographic patterns by swath profiles (Perez Pena et al, 2017: 136). To avoid arbitrariness of selecting a single profile line, earth scientists use topographic swath profiles (Telbisz et all, 2013: 485). Examining elevation values associated with corresponding coordinates is one of the most common variables to study by swath profiles (Telbisz et all, 2013: 487، Yousefi Bavil & Yousefi Bavil, 2019: 281). In these projected profiles, contours and equally spaced profile lines intersections are determined inside a band (Grohman, 2004: 1059). In the present study, in order to evaluate the long-term equilibrium of northwestern Zagros landscapes in response to internal and external forces that uplift or tear down its topography, Perez-Pena et al (2017) method of extracting swath profiles has been used. We have also used their new transverse hypsometry index for analyzing hypsometry along the swath. Since different parts of the Zagros are subjected to different tectonic force vectors, thereby, the rate of tectonic processes and the resultant forms are not the same. On the other hand, surface processes make these landscapes’ evolution more complex. To simplify the topographic pattern of these complex processes, 10 swath profiles parallel and perpendicular to the Lorestan arc and its adjacent crushed zone trend have been plotted and interpreted.
MethodologyTopographic swath profiles are created by projecting topographic profiles with equal space inside a strip or swath (Perez-Pena et all, 2017; Fielding et al., 1994). This method is applied for sampling and analyzing a value and its changes for representing three-dimensional datasets on a two-dimensional diagram that is more systematic than ordinary profiles with arbitrary cross-profiles (Yousefi Bavil & Yousefi Bavil , 2019; Telbisz, et all. 2013; Hergarten, et al, 2014).In the swath profile, statistical parameters of elevation values (maximum, minimum, mean, quartile 1 and 3 as well as local relief) can be calculated and plotted against the distance (Telbisz et all, 2013: 485). Different methods of constructing swath profiles have been explained by Telbisz et al, 2013; Hergarten et al, 2014, Perez Pena et al, 2017, Yousefi Bavil and Yousefi Bavil, 2019. In this article, Perez Pena et al (2017) approach has been used to extract swath profiles which allows constructing swath profiles for curved features. This kind of swath profile is made up of calculating parallel lines to the baseline and sampling their length with defined step sizes. In addition, considering the deviations of mean elevation to the maximum or minimum elevations, by re-scaling hypsometric integral values in a defined range (between 0.2 and 0.8), an enhanced transverse hypsometry index (or THi*) can provide better comparison of hypsometry along swath profile. All these commands can be implemented in GIS software by swath profiler add-in programmed by Perez-Pena et al (2017). Here digital elevation model is the elevation source and a line or curved feature is the baseline. The step size and total width of profiles also can be changed in the input box of the add-in. In this study, swath profiles with 40 meters step size inside a strip with a width of 20 km (10 meters from each side of baseline or main profile line) for five transects perpendicular to Zagros trend (NE-SW) named P1 to P5 and five transects parallel to its trend (NW-SE) named H1 to H5 (fig. 8) along with their main fault have been extracted (fig. 9 & 10). The NW-SE baselines follow the main Zagros faults (Berberian, 1995) in area (Zagros main reverse fault and Zagros recent fault, high Zagros fault, Zagros mountain front fault, and Zagros foredeep fault). Five NW-SE curve lines cross morphotectonic units of Zagros (Berberian, 1995) which are adjacent (High Zagros thrust belt, Zagros simply folded belt, and Zagros foredeep contains Dezful and Kirkuk embayments).
ResultsIn plotted swath profiles, mean elevation represents general topographic trend of landscape within swath; minimum and maximum elevation show landscape variation perpendicular to the swath, local relief, and quartile describe topographic variation along the swath. Upward deflection of mean elevation to maximum elevation reveals a transite state of landscape adjustment to high uplift rates. Stable state landscapes including basins and plateaus with low incision rates have smoother local relief curve where the swath curves are merged (Perez-Pena et al, 2017: 137). Based on the exported diagrams, higher values of enhanced transverse hypsometry index (Thi*) occurs when the third quartile and in some points mean elevation is closer to the maximum. When swath curves meet the flat areas of Zagros foredeep (Dezful embayment) merging together, Thi* values keep a constant value of about 0.5.
Discussion & ConclusionsResults show that in swath profiles with the direction perpendicular to the Zagros trend, comparing areas with different uplift and incision is better possible. In both perpendicular and parallel swath profiles, high values of the enhanced transverse hypsometry integral (THi*) introduce a young relief that is being incised by a drainage network with steep valleys. These high values of THi* can be observed in the location of anticlines of Zagros simply folded belt unit and as well as in intersections of main faults with swath profiles in most swath diagrams. High local relief and wider variation of curves in most swath profiles, except the end parts of the southwest of the region, can characterize a dissected landscape exposed to high incision or uplift.
Keywords: Erosion, Northwestern Zagros, Relief, Swath, Tectonic -
طی دوره های باستانی، شرایط جغرافیایی هر منطقه، از مهم ترین عوامل تاثیرگذار در تعیین الگوی استقرار سکونتگاه ها بوده و تغییرات محیطی، منجر به تغییر الگوهای استقراری نیز می گردیده است. هدف از این پژوهش، بررسی تاثیر تغییرات دیرینه تراز دریای خزر و همچنین نقش عوامل ژیومورفیک در الگوی استقرار محوطه های باستانی شرق استان مازندران می باشد. در ابتدا، نقشه ارتفاع، شیب و ژیومورفولوژی محدوده مورد مطالعه تهیه گردید و موقعیت نقاط باستانی (از دوره پارینه سنگی تا دوره اسلامی) فراوانی و تراکم آنها در هر یک از طبقات ارتفاعی، شیب و لندفرم های ژیومورفولوژیکی، مورد بررسی و تحلیل قرار گرفت. نتایج ضمن تایید تاثیر پذیری الگوی استقرار از عوامل ژیومورفیک محدوده ی مورد مطالعه نشان داد که در دوره های متفاوت، تاثیر عوامل فوق مورد مطالعه، بر مکان گرینی استقرارگاه ها، متفاوت بوده است. هچنین مطالعه لندفرم ها و پراکندگی نقاط باستانی مشخص نمود که مخروط افکنه ها، متراکم ترین لندفرم محسوب می شوند و متراکم ترین بازه ارتفاعی در محدوده مورد مطالعه، بازه ارتفاعی 0 تا 15 متر بوده که این بازه ارتفاعی دقیقا منطبق بر قاعده مخروط افکنه های موجود در منطقه می باشد.در مرحله بعد، با مطالعه پژوهش های انجام شده بر روی تغییرات سطح اساس دریای خزر طی هزاره های گذشته، ایجاد بانک اطلاعات از داده ها و سپس تطبیق زمان این نوسان ها با دوره های باستانی، تاثیر تغییرات خط ساحلی بر مکان گزینی سکونتگاه-های باستانی حوضه جنوب شرق دریای خزر مورد بررسی قرار گرفت و نتایج نشان داد که در برخی از دوره های باستانی الگوی استقرار به شدت تحت تاثیر پیش روی ها و پس روی های دریای خزر می باشد.
کلید واژگان: زمین باستان شناسی, الگوی استقرار, ژئومورفولوژی, تغییر سطح اساس, جنوب شرق دریای خزرIntroductionHuman interaction with the natural environment has undergone many changes from the past millennia to the present. But geo archaeological studies tell us that although this interaction has changed, the basis of human behavior with the natural environment has been almost the same and based on one thing: Knowledge of the natural environment. Areas located in the southeast of the Caspian Sea, in terms of the relationship between natural and archaeological factors, are one of the most complex areas in Iran. The purpose of this study is to investigate the relationship between geomorphic factors and Paleo sea-level changes in the Caspian Sea with the settlement pattern of ancient sites in the east of Mazandaran province.
MethodologyAt first, using Arc GIS software and the 30-meter DEM, elevation and slope maps was obtained and classified. Then, using satellite images, Google Earth software and topographic map of the area, geomorphological map was prepared and the location of ancient settlements in relation to the slope and elevation, as well as the distribution and density of ancient sites in various landforms were analyzed. After that, in order to investigate the effect of long-term changes in the CS level on the settlement pattern of ancient sites, first the researches in this field were collected and after creating a database of the Paleo sea-level changes in the CS, these changes were temporally accommodated to the ancient periods. Then, the coastline in each ancient period in relation to the location of ancient sites were analyzed.
Results and discussionWith the distance from the coastline, the density gradually increases and in the range of zero to 15 meters, the density reaches its maximum. Increasing altitude with decreasing temperature, flat lands and suitable soil for agriculture and pottery and increasing distance from the sea as a rich source of food, has led to a decrease in the density of ancient settlements. As the slope increases, the conditions for establishing a settlement become unfavorable and the density of archeological sites in the study area gradually decreases. Also, the slope is an important factor in determining the land use and sloping areas may be prone to erosion if cultivated. The density of ancient sites on alluvial fans is higher than other landforms. In addition, as mentioned earlier, the densest elevation range is from 0 to 15, which corresponds exactly to the distal part of alluvial fans in the study area.In the Paleolithic period, the CS experienced a regression (-50m), also experienced high stands up to 0m during the Khvalynian transgression (Mamedov, 1997), but the ancient settlements of this period were not very affected by these changes due to their nomadic lifestyle. The EpiPaleolithic period coincides with the last Khvalynian transgression and CS level reached its maximum (+50). After that, the CS entered the regression phase of Mangyshlak and the maximum regression of that (-92m) occurred at this time (Kroonenberg et al, 2011). It seems that during this period, ancient communities built their settlements near the coastline, in order to have maximum access to the food resources. In the Neolithic period, the accumulation of ancient sites is in the coastal areas. With the advent of agricultural activity, coastal areas became more and more important to ancient societies and the reason is the presence of fertile soil, low slope and access to sufficient water and soil for agricultural activity and pottery. The maximum shoreline recedes during the Chalcolithic period occurred at 7100 BP (-36.5m) (Kroonenberg et al, 2008). And the greatest transgression has occurred in 7000 years ago (-20m) (Raychagov, 1997). This short period of time could have prevented ancient societies from adapting to environmental changes and many settlements near the coastline have been destroyed. In Bronze age, the CS level has fluctuated from -35.5m (Kroonenberg et al, 2008) to -21m (Mamedov, 1997). Along with the shoreline recedes, the settlements also advance towards the sea, and with the re-advance of the coastline, the settlements have been buried under sediments and water. During the later periods, there is an increase in the number of ancient sites in the highlands compared to previous periods. It’s may be due to military security issues during these periods. Because mountainous areas, with more difficult access than coastal areas, have provided more security for its inhabitants.
ConclusionThe purpose of this study is to investigate the relationship between geomorphic factors and Paleo sea-level changes in the CS with the settlement pattern of ancient sites in the east of Mazandaran province. The results show that as the slope and elevation increase, the conditions become unfavorable and the density of archeological sites in the study area decreases. in the range of zero to 15 meters, the density of archaeological sites reaches its maximum and this elevation corresponds to the distal part of alluvial fans where is the densest landform in the study area.One of the most important features of the study area is the intermittent changes in the CS level. After separating from the Black Sea in the Middle Pliocene, the CS has experienced several cycles of sea level fluctuation. In the Paleolithic period, ancient settlements were not very affected by these changes due to their nomadic lifestyle. But in the Epi Paleolithic period, it seems that ancient communities built their settlements near the coastline, in order to have maximum access to the food resources. In the Neolithic period, With the advent of agricultural activity, coastal areas became more important to ancient societies and the reason is the presence of fertile soil, low slope and access to sufficient water and soil for agricultural activity and pottery. During all periods, along with the shoreline recedes, the settlements also advance towards the sea, and then, with the re-advance of the coastline, the ancient settlements have been buried under sediments as well as the sea water. Moreover, in later periods, due to military security issues, the number of ancient sites in the highlands increased. Because mountainous areas, with more difficult access than lowland, have provided more security for its inhabitants.
Keywords: Geo archaeology, Settlement pattern, geomorphology, Sea level change, Southeast of Caspian Sea -
هدف اصلی در این پژوهش بررسی تاثیر نوزمینساخت بر توالی لندفرم های کوهستانی و پایکوهی ناحیه دامغان با استفاده از تغییرات شیب و واکنش فرسایشی - برشی رودهای جاری بر سطح این لندفرم ها به عنوان یکی از عوامل کلیدی تحول چشم اندازها است. در این راستا ابتدا نقشه شیب آبراهه ها و نقشه توان برشی رود منطقه با توجه به پارامترهای تاثیرگذار شامل شیب رودخانه، مساحت حوضه زهکشی، نرخ تندی و بازده فرسایشی رود تهیه شد و سپس نیمرخ طولی برگرفته شده از این نقشه ها از شمال به جنوب منطقه با توجه به عوارض و لندفرم های برجسته ای که در ناحیه وجود دارد، ترسیم و مقایسه شد. از تحلیل نیمرخ های طولی برگرفته شده از نقشه شیب رود و توان برشی رودخانه می توان به این نتیجه رسید که این روش در شناسایی توالی لندفرم های متاثر از فرآیندهای زمینساختی، کاربرد زیادی دارد. هر جا که فعالیت گسل ها به شکل تراکششی منجر به ایجاد نواحی کم ارتفاع و فروافتاده شده است مانند حوضه واچاکیده آستانه، نرخ برش رود در برابر کاهش میزان شیب کانال، کاهش داشته است. در این حوضه نرخ برش رود 59/2 میلی متر در سال در برابر شیب کانال: 46/4 درصد می باشد.اما هر جا فعالیت گسل ها منجر به افزایش ارتفاعات و برآمدگی ها شده است، مانند خم گرفتاری ارتفاعات کرکسی، مجموعه راندگی ارتفاعات سفیدرشته کوه و یا فوربرگ های سربرآورده از میان رسوبات بادبزن های آبرفتی، نرخ برش رود در برابر افزایش شیب کانال، بالا رفته است. برای مثال در ارتفاعات کرکسی نرخ برش رود 12/10 میلی متر درسال در برابر شیب کانال 10/11 درصد می باشد.
کلید واژگان: البرز شرقی, دامغان, زمینساخت فعال, نرخ برش رودخانه, سکانسهای لندفرمیIntroductionThe identification and analysis of the active tectonic or denudation processes through the analysis of the deformation and landform changes consist one of the fundamental objectives of the tectonic geomorphological studies. Rivers are among the groups of geomorphologic elements that flow on a wide range of different landforms and can reveal the critical relationships among uplift, lithology, and denudation of heights. With regard to the evolution of landforms, this group of information and the relations between them are preserved by the bedrock properties. River Incision is the primary mechanism by which landscapes adapt to climate change and tectonic forces. Among the many factors that affect the Incision rate, the distribution of slope and steepness of water channels can be systematically effective. The main purpose of this study is to investigate the sequence of mountainous and foothills landforms in Damghan region using slope changes and erosion-incision reaction of rivers on the surface of these landforms as one of the key factors in landscape evolution.
MethodologyThere are many models for calculating the river incision rate, but the most widely used is the SPIM model, which is presented in the form of the following equation:I=K*A^m*S^nThe SPIM model is based on simple geometric parameters, such as the slope and area of the drainage basin extracted from the DEM elevation map. Some parameters are related to energy considerations, such as the rate of energy consumption in the channel bed and ridges, in which case; m: 0.5 and n: 1 are used as experimental constants in the formula.In order to calculate the values of this index and prepare a river incision map, first the whole study area was divided into 64 sub-basins so that the resulting section values are suitable for surface interpolation. In the next step, the values of effective indicators in the SPIM formula including river slope, drainage surface area and erosion efficiency were calculated for each of the sub-basins. To calculate the erosion efficiency index, first the steepness values of the rivers of each basin were calculated from the formula of stream power incision, based on power regression, in the form of the following equation.S=K_s A^(-θ)In the above formula Ɵ is the amount of concavity and KSN is the amount of steepness.After obtaining the steepness values of rivers in each of the 64 catchments, the erosion efficiency relationship was used as follows:U=〖ksn〗^n*KU is actually the rate of elevation or change in altitude of the area relative to the base level, which was calculated using the radar interfrometry method to determine the amount of vertical displacements in the area.In order to prepare and analyze the slope and incision rate of rivers in Damghan region, and to convert point values into raster levels containing value, the inverse distance weighted interpolation method or IDW was used.
Results and DiscussionComparison of longitudinal profiles taken from the slope map and incision rate of Damghan region shows the close relationship between these two parameters; Both of these parameters together play an important role in analyzing the tectonic status of the areas. In such a way that in examining the condition of the longitudinal profiles of the region from north to south, there are prominent features such as mountain belts or foreberg shapes; The slope rate and incision rate of the river increase and in front of where there are depression constructions such aspull apart basins or the end parts of longitudinal profiles that are based on alluvial plains, the slope rate and the following incision rate of the river decreases.Therefore, the analysis of longitudinal profiles taken from the slope map and incision rate of rivers in Damghan region can be effective in identifying and analyzing the effect of active fault mechanisms on the sequence of landforms in the region. the areas that have mainly high slope and incision rate of the river and are shown prominently in the longitudinal profile, represent the performance of faults in the form of transpressional, which leads to the formation of elevated landforms. In contrast, the concave areas in the longitudinal profile of the slope and incision of the rivers in the region are mainly representative of the areas where the gentle slope has led to a reduction in the slope of river systems and thus reduced river incision capacity.these areas are either mainly based on flat lands which are in the southern part of mountain structure in form of alluvial sediments or they are collapsed structures due to transtentional motion of faults such as Astaneh pull-apart basin.
ConclusionThe activity of faults with different mechanisms causes the uplift or subsidence of landforms to form a series of successive landforms in an active tectonic environment. The rise and fall of these structures have led to an increase or decrease in their slope which will effect on the waterway systems that flow on these landforms. Wherever the fault mechanism leads to an increase in the height and elevation of the landforms, the slope of the river increases and as a result the incision power of the river increases. From the analysis of longitudinal profiles taken from the slope map and the incision of the river, it can be concluded that this method is very useful in identifying the sequence of landforms affected by tectonic processes. In a way, by examining the process of changing these longitudinal profiles, we can understand how active faults function in shaping landforms in compressive or tensile form. Wherever the slope of the waterway is high and the incision rate of the river is high, it indicates the existence of a elevated axis. This landform can be a mountain ridge or even elevated forms among alluvial sediments.wherever the slope and incision rate of channel show low values, it can indicate the existence of a concave tectonic basin.
Keywords: Eastern Alborz, Damghan, Active Tectonic, Incision Rate, Landforms Sequences -
Sarchahan Formation (Silurian) consists of shale and sandstone interbeds in the studied well in the Persian Gulf. Sedimentological characteristic of this formation is presented here for the first time. Based on petrographic studies and wire line logs studies, five petrofacies and three facies associations were identified in the Sarchahan Formation. Variations in facies association in combination with palynological studies represent that deposition of the Sarchahan Formation took place in different subenvironments of a delta environment from prodelta to delta plain. The lower part of the formation is represented by a high amount of black shale and higher total organic carbon values which are the result of deposition in the deeper parts of the basin. Meanwhile, the upper part is composed of sandstone and red mudstone which are the result of deposition in the shallower part of delta environment. Cementation, compaction and dissolution are the main diagenetic features which affected the Sarchahan Formation. Silica and sericite cements are the most abundant cement types in quartzarenite and subarkose petrofacies the development of which resulted in porosity reduction. The comparison with the Arabian plate, the deposition took place in a southward deepening basin into which sediments were introduced from the northern parts. .Keywords: Sarchahan Formation, Delta environment, Persian Gulf, Arabian Plate, Silurian source rocks
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زمین لرزه ها حاصل گسلش و پویایی زمین ساختی هر ناحیه هستند و نسبت به بزرگا، فضا و زمان توزیع فرکتالی دارند. در این تحقیق پارامترهای لرزه خیزی b-value و FD به عنوان رویکرد کمی فرکتالی در تحلیل لرزه خیزی زاگرس شمال غرب بکار رفته است. پارامتر b با توزیع فراوانی-بزرگای گوتنبرگ-ریشتر و پارامتر FD به روش مربع شمار محاسبه و همچنین با استفاده از 30 خوشه تمرکز زمین لرزه و عوامل مهم، پهنه های لرزه خیز با روش آنتروپی مشخص شدند. کاهش b-value رخداد زمین لرزه های با فراوانی کم و بزرگای بالا و افزایش FD عدم خوشه بندی و توزیع یکنواخت زمین لرزه ها را نشان می دهد. همبستگی منفی این دو موید زمین ساخت فعال است. نتایج نشان می دهند که افزایش FD با کاهش b-value (همبستگی منفی 60 درصد) همراه است. منطقه A (غرب کرمانشاه) ، بالاترین میزان (FD (1/02 و پایین ترین میزان b (0/78) را داراست که به معنی توزیع بالای تنش در منطقه (و شاهد آن زمین لرزه اخیر کرمانشاه با بزرگای 7/3) است. منطقه E (محل اتصال گسل های جبهه کوهستان و بالارود)، مشابه A است اما زمین لرزه های آن بزرگای کمتری دارند (5 و 6 ریشتر). منطقه F (محل پیوند گسل های اصلی و جبهه کوهستان زاگرس)، با وجود تراکم بالای گسل و زمین لرزه، نقطه مقابل A است که بیانگر رها شدن تنش در قالب زمین لرزه هایی کوچک است. منطقه C (حاشیه غربی با کمترین تمرکز گسل و فراوانی زمین لرزه)، مشابه F است. مناطق D و B (مجاور گسل های معکوس و رورانده زاگرس، شرایطی زمین ساختی متوسطی دارند. نتایج مدل آنتروپی نتایج FD را تایید می کند و رابطه معکوسی با مقادیر b دارد.
کلید واژگان: لرزه خیزی, زاگرس شمال غرب, فرکتال, آنتروپیIntroductionThe purpose of present study is seismicity analysis of Lorestan folded arc and its adjacent thrust belt using quantitative methods. To reach this aim we performed analysis of seismicity using quantitative methods to find possible vertical and horizontal changes in seismic activity across the main Zagros faults of the northwestern part of Zagros. Firstly, we used fractal geometry and frequency-magnitude distribution of earthquakes by using FD and b-value parameters, respectively. Here b-value is the main factor in Gutenberg-Richter empirical relation which indicates the exponential distribution of earthquake magnitudes (Godano et al, 2014; 1765). This parameter also is known as fractal dimension (Mirabedini & aghatabay,2015: 60). FD is fractal dimension of earthquake epicenters distribution which has been calculated by box-counting method (Turcotte 1997). On the other hand Entropy model has been applied to specify potential of seismicity by using effective factors and 30 points of earthquake concentration. The study area in northwestern part of Zagros was divided to the simply folded arc of Lorestan and faulted-folded belt of high Zagros. Several main faults pass through the area from NW to SE and divide its main morphotectonic units as High, folded and foredeep parts of Zagros (Berberian, 1995: 193).
Material and methodsData in this research can be divided to two part: parameters of earthquakes (magnitude, depth, location of epicenter) and linear data of faults and anticline/syncline axes. These data have been changed into new layers by GIS software extensions (density of epicenter and depth of earthquakes, density of faults and anticline/syncline axes, distance of fault and epicenter of earthquakes, interpolation of epicenter of earthquakes) to be applied in Entropy model, in other hand frequency of magnitude clusters and surface distribution of earthquakes are main data in Gutenberg–Richter relation and Fractal methods respectively. Numerical results of mentioned methods have been calculated and drawn in excel software. Gutenberg–Richter relation (Gutenberg & Richter 1944) is defined as Log N(m)= a-bm, where N is the cumulative number of earthquakes with magnitude larger or equal to m, a is a constant (seismicity level) and b is the slope of frequency-magnitude (size distribution) (Godano, 2014). To calculate fractal dimension of distribution of earthquake epicenters, box counting method suggested by Turcotte (1997) were applied by using Hausdorff dimension, which in two quantity of size (side length of grids) and number (number of grid boxes containing earthquake) are used to calculate FD value (Schuller et al, 2001: 3). In the other section, earthquake epicenters are divided to several clusters with different magnitude, then kernel density of each cluster was applied and subsequently, the maximum concentration of each magnitude cluster was determined as a point layer. Followingly, by overlaying these point layer with effective layers in seismicity analysis, their characteristics was extracted. Finally, an Entropy matrix was calculated and using experts rating and computing the layer’s weight, seismic zones were identified (Zonggi, et al, 2010).
Result and discussionEstimated b-value indicates approximately reciprocal values compared with FD values. Decrease in b-value reveals that stress level and probability of large magnitude earthquakes occurrence is quite high and increase in FD shows that earthquakes are not clustered and are distributed homogeneously along a line in understudy area. Calculated number-size values for earthquakes represent both partial and popular FD changes. Based on partial FD, three populations can be classified: (a) Background with FD larger than popular FD; (b) Threshold with FD lower than 0.7: and (c) Anomaly with FD more than two. Based on popular FD, distribution of earthquakes is linear and transition to chaos phase is not predicted. Comparison between maximum values of Entropy zoning and FD values for each box indicates that these two values show 93% correlation (regardless of the C box values due to incompatibility with value of other boxes).
ConclusionAreas with high FD value and low b-value are more tectonically active. The box labeled A which represent western parts of Kermanshah in folded Zagros, has the highest FD value (1.02) and lowest b-value (0.78). The box labeled F in southern east part is in contrast with it (highest b value:1.02 and one of the lowest FD value: 0.89) in understudy areas. E (Balarud fault) and D (High and folded Zagros) parts have almost the same FD and b values. FD and b values in B (high Zagros) are equal and less than the aforementioned areas. C (that contains a part of mountain front fault) has the lowest value of FD and same b-value as B and the changes of Entropy max values are same as FD values.
Keywords: Seismicity, Northwestern Zagros, fractal, Entropy -
تحولات اقلیمی مهم ترین رویداد دوره کواترنری است که این تحولات به طور وسیعی در ژیومورفولوژی و رسوب شناسی این دوره منعکس شده است و علم پالیوژیومورفولوژی به فهم تغییرات اقلیمی گذشته و پیش بینی این تغییرات در آینده کمک می کند. دریاچه های واقع در چاله های بسته دوره های سرد یا بارانی کواترنر را دریاچه های پلویال می گویند که بعضی از این دریاچه ها به کلی خشک شده و از بین رفته اند، بعضی دیگر در حال حاضر دریاچه های موقتی هستند که در فصل خشک به کویر تبدیل می شوند و برخی دیگر دریاچه های دایمی هستند که در گذشته وسعت بیشتری داشته اند. شناخت دریاچه های پلوویال در مناطق خشک امروز به دلیل تنوع فاکتورها و فرآیندهای پیچیده در تشکیل آن ها مورد توجه محققان است. این پژوهش با هدف تعیین گستره پلایای میقان در کواترنری پسین براساس شواهد رسوبی و ژیومورفیک انجام گرفته است. پلایای میقان در مرکز و جنوب غربی استان مرکزی واقع گردیده و دربرگیرنده دریاچه فصلی و شور توزلوگل، دشت آبرفتی، مخروط افکنه و ..می باشد. داده های مورد استفاده عبارتند از: داده های حاصل از منابع کتابخانه ای، داده های آماری، نمونه های رسوبی، داده های آزمایشگاهی و سنجش از دور. این داده ها در نهایت به روش تحلیلی مورد بررسی قرار گرفته و نتیجه گیری انجام شده است. نتایج حاکی از شواهد رسوبی و ژیومورفولوژیک نشان می دهدکه این دریاچه در گذشته دایمی بوده و وسعت بیشتری نسبت به سطح پلایای فعلی داشته ولی این گسترش در جهات مختلف متفاوت بوده و تفاوت های معناداری به علت موقعیت زمین ساختی منطقه نشان می دهد.
کلید واژگان: پادگانه دریاچه ای, پلایا, کواترنری پسین, تغییرات اقلیمی, چاله میقانIntroductionClimate changesare considered to be the most important event of the Quaternary period largely reflected in the geomorphology and sedimentology of the period.Paleogeomorphology helps us to understand past climate changes and predict future changes. Depending on the Quaternary periods, closed pitlakes are called cold or rainy period lakes.Some of these lakes have completely dried up, others are temporary lakes that change into playas in the dry season, and others have been larger in the past. Researchers can identify pluvial lakes in today’s arid regions, because of the variety of factors and complex processes involved in their formation.Mighan Playa is located in the central and southwestern areas of Markazi province. It includes seasonal and saline Tozlogol Lake, and alluvial plains.
MethodologyThe present study used evidences of playa lake sediments as well as geomorphological evidences(lake terrace) to investigate the extent of MighanLake in Quaternary period. Data included datacollectedfrom library sources, statistical data, field surveys, sedimentary samples, sedimentary evidences, climatic data, remote sensing data received from Landsat TM satellite, ETM, and SRTM digital elevation models(SRTM 90 meters, and Dem10 meters).Initially, previous studies and environmental characteristics of the area were analyzed. Then, lake terracewas investigated to find geomorphic evidences of Pluvial Lakes in Quaternary period. To do so, probable ranges of the lake Terrace were determined using satellite imagery, geological maps, and elevation data of digital models. Probable area was divided into several distinct zones, and finally an area was identified in the western part of the lake and based on the elevation of this zone, the extent of the lake catchment in Quaternary period was determined. During fieldwork, samples were collected from the mountain slope line toward the Playa and lake shore, and then granulometrytests were performed on the 14 collected samples to determine the amount and type of sediments.Sedimentary and graphical analysis were also performed based on Folk classification. The percentage of clay and sand in the new samples collected from the region containing this mountainous area, lake coast and deeper parts of the lake were determined and attributed to past sediments. In this way, the information could be used to determine the extension of lake sedimentsin the past.Based on sedimentary logs (Arak Groundwater Studies Report, Central Water department of Markzani Province), sedimentology studies and percentages (clay-sand-gravel) of present-day samples collected from deep sections of Playa andelevated areas of sediment pits were interpolated in GIS environment and a map of the lake extension in the Mighan catchment areawas prepared.Subsequently based onpaleogeographic studies, paleontological climate of the area and sedimentation rate calculated by Pedrami in 1993, a map was produced to show the extent of sediments and the lake progressions and regressions in the past.
DiscussionThe stratigraphic and sedimentary evidences of logs in the margins of Mighanpit indicates changes in wet and dry periods. Type and size of sediments reflect the climatic conditions in each period, while high percentage of clay sediments reflects lake conditions. Paleontological sedimentological maps of the area show that the clay sediments were more concentrated in the southwestern, western and northwestern regions. Uplift of the Talkhab fault in the northeastern regionhas resulted in tectonic asymmetry of the pitand concentration of sediments in the western and southern parts. According to Krinsley, Bubeck, Pedrami and etc. Lake Mighan has been larger in the past. However, none of these researchers have determined the extent of lake water in the past. In this study, the extent of the lake was determined by reconstruction of clay sediments and using geomorphological evidencescollected from the lake shorelines (lake terrace) near Mighan village (Mashhad). Results indicated a height of 15 m in Quaternary period.
ConclusionSedimentary and geomorphologic evidences indicated that compared to the present playa level, the Lake fluvial was more permanent and vast in the past, but this extension differs in different directions and shows significant differences due to the tectonic location of the area.
Keywords: Terrace lake .playa. Late Quaternary. Climate change. Mighan -
یکی از عوامل زمین ساختی که نقش قابل توجهی در شکل زایی دارد، آتشفشان ها و مواد مذاب ناشی از آن ها است. فوران های آتشفشانی باعث دگرشکلی مورفولوژی و ایجاد ساختمان لندفرمی جدید می شود. آتشفشان دماوند با فوران های متوالی خود، طی کواترنری تغییرات قابل توجهی در پیرامون خود ایجاد نموده است. در این پژوهش، نقش گدازه های دماوند در تغییر مسیر رودخانه ها مورد بررسی قرار گرفته است. برای دستیابی به این هدف، روش تحلیلی و بازسازی زمانی تغییرات به کار گرفته شده اند. تکنیک کار بر مقایسه مورفومتری رودخانه ها و دامنه های مشرف به دره ها به سه روش مقایسه ارتفاع و ضخامت رسوبات آبرفتی، تعیین حدود گسترش رسوبات رودخانه ایی و دریاچه ایی و بازیابی آخرین حد ارتفاعی گدازه های مشرف به دره ها استوار است. رودخانه هراز به طور متوسط 4 کیلومتر، رودخانه دلیچای 3 کیلومتر و رودخانه لار 2 کیلومتر بر اثر گدازه های دماوند به مرور و طی فوران های متوالی تغییر مسیر داده اند. مسیر رودخانه ها عمدتا پس از شکل گیری دریاچه ها بر اثر انسداد دره ها و شکسته شدن سد ایجاد شده اند. قابل ذکر است که سطح اساس رودخانه های مذکور حدود 100 متر بالا آمده است.
کلید واژگان: تغییر مسیر رود, دماوند, دیرینه ژئومورفولوژی, رود هرازIntroductionOne of the tectonic factors that play a significant role in the formation is the activity of volcanoes and the flow of volcanic materials. The volcanic eruptions cause morphology and create new landforms. Damavand volcano with its successive eruptions during the Quaternary has made significant changes to its surroundings. In this study, the role of Damavand lava flows in changing the bed rivers has been investigated. The main purpose of this study was to investigate the effects of the latest Damavand volcanic eruptions on the behavior and direction of these bed rivers around it. Materials and Methods The technique has been based on three main
methods1) Comparison of the height and thickness of sedimentary deposits obtained through the morphometry of transverse profiles on the fieldworks. 2) Determination of the extent of lake sediment distribution in the Haraz, Lar and Delichai areas, which is transmitted on the map based on field data and GPS coordinates. 3) The extent and altitude of the lava flows overlooking the Haraz, Lar and Delichai valleys have been recorded and transferred to the maps. In addition, much of the data was obtained through indirect observations through satellite imagery and then combined with field findings. To achieve this, the length of the rivers is divided into two distinct intervals. Then morphometric data of valleys, sedimentary evidences and dynamics of rivers in the form of the mentioned intervals are studied and compared temporally and spatially. At the analysis stage, the above data have been adjusted with the radial pattern of the drainages around Damavand to the main grid as well as the volcanic cone structure and then the longitudinal routes of the rivers have been reconstructed.
Results and DiscussionEvidence indicates that there was no significant change in the waterway during the Abask interval toward Amol and the outlet of the basin (Interval 1). However, in the Abask-to-Plour (Interval 1) range, the presence of lava gravels carried by the Haraz River and deposited in the northwest of the Abask landslide indicates that the river changes over time. Also, the lava flows overlooking the Haraz valley represent major changes that have occurred in the past. In this regard, the Haraz River has dug up to a depth of 100 meters in the sediments of lakes and rivers. The amount of river diversion at the intersection of the Lasem River to the Haraz River (Interval 1) and the displacement of the river bed is approximately 4400 meters from its present bed. The modified route in the second interval is about 4200 meters. The bed river of the Haraz River redirection from the old Plour Bridge to the intersection of the Haraz and Lasem (interval 1) is about 1600 meters. Reconstruction of the old Haraz River bed route indicates that the stream has stretched past the eastern part of the Tizkuh sedimentary slope. The average redirection of the Haraz River in this interval is estimated at about 1000 meters. In the second interval, the most deliberate distance of the Delichai River is the intersection of this river with the Lar River. This displacement is estimated to be about 4100 meters. Damavand lava flows in this region have created a lava barrier along the Delichai River Route, changing the east-west direction. The mean flow direction of the Delichai River is estimated to be 2500 meters. In addition, studies indicate that as a result of the formation of lava dams, the base level of the above-mentioned rivers has also risen by an average of 100 m above the level of its original base level, prior to the Damavand eruption.
ConclusionThe results indicate that there have been major changes except for one in two intervals, and that these changes have occurred in two major forms. One is the formation of lava dams caused by Damavand eruption, which has caused major changes in the longitudinal profile of the rivers and the deepening, formation of gullies and then filling of the canals are three forms of this process. There are four levels of terrace that illustrate this. Secondly, the diversion of rivers occurred in the second and third intervals, where the presence of river deposits beneath the lava flows as well as the general topography of the valleys can clearly identify the longitudinal paths of the waterways in these two intervals.
Keywords: River diversion, Damavand, Paleogeomorphology, Hazar river -
یکی از عوامل زمین ساختی که نقش قابل توجهی در شکل زایی دارد آتشفشانها و مواد مذاب ناشی از آن ها است. فوران های آتشفشانی باعث دگرشکلی مورفولوژی و ایجاد ساختمان لندفرمی جدید می شود. آتشفشان دماوند به عنوان یک عارضه ساختمانی با فوران های متوالی خود طی کواترنری تغییرات قابل توجهی را در پیرامون خود ایجاد نموده است. در این پژوهش، نقش آخرین گدازه های دماوند در ایجاد دریاچه های سدی مورد بررسی قرار گرفته است. برای دستیابی به این هدف روش تحلیلی و بازسازی زمانی تغییرات به کار گرفته شده اند. تکنیک کار مقایسه مورفومتری پادگانه های دریاچه ای و سدهای گدازه ای به سه روش مقایسه ارتفاع و ضخامت رسوبات آبرفتی، تعیین حدود گسترش رسوبات دریاچه ایی و باز یابی آخرین حد ارتفاعی گدازه های مشرف به دره ها استوار است. دریاچه هراز در ارتفاع 2550متری و با مساحت 04/52 کیلومتر مربع، دریاچه لار در ارتفاع 2580متری با مساحت79/68 و دریاچه دلیچای در ارتفاع 3780 متری از سطح دریا و با مساحت 25 کیلومتر مربع قرار گرفته اند. این سه دریاچه به صورت تقریبا همزمان شکل گرفته اند. جریان های گدازه ای این سه دریاچه را از هم جدا و به صورت متوالی کنار هم قرار داده اند. دریاچه ها از طریق تندآب ها با هم مرتبط بوده که منجر به تشکیل مجرای فعلی شده است.کلید واژگان: دماوند, دریاچه سدی, پادگانه دریاچه ای, دیرینه ژئومورفولوژیOne of the most important structural factors in the formation of volcanoes and molten materials is their formation. Volcanic eruptions cause deformation of morphology and the creation of a new landform. Damavand volcano has made significant changes around its quaternary as a complication with its successive eruptions. In this research, the role of Damavand lava in the creation of dam lakes has been investigated. To achieve this goal, the analytical method and the timing of the change have been applied.The technique of comparing the morphometry of lagoons and lava dams is based on three ways of comparing the height and thickness of alluvial deposits, determining the extent of spreading of sediments of the lakes, and the restoration of the last elevation of lavaes overlooking the valleys. Lake Haraz, at 2550 meters and with an area of ââ54/44 square kilometers, lar lake is located at a height of 2580 meters with an area of ââ68/79 and Dilichai lake at an altitude of 3780 meters above sea level, with an area of ââ25 square kilometers. These three lakes are formed almost simultaneously. The lava streams of these three lakes are separated and consecutively put together. The lakes are connected through the swells, which led to the formation of the current duct.Keywords: Damavand, lake dam, lake paradise, ancient geomorphology
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شناسایی و مدیریت ریسک یکی از رویکردهایی است که برای تقویت و ارتقای اثربخش سیستم ها مورد استفاده قرار می گیرد. در این پژوهش به بررسی تاثیر مخاطرات بر توسعه گردشگری شهرستان سرعین پرداخته شده است. این منطقه یکی از مقاصد گردشگری مهم در ایران محسوب می شود که مانند هر مقصد گردشگری دیگر می تواند از سوی مخاطرات محیطی مورد تهدید قرار گیرد. در همین راستا تحقیق حاضر به روش توصیفی- تحلیلی و به کمک دو جامعه آماری مرتبط با گردشگری یعنی گردشگران داخلی وارد شده به مقصد گردشگری و مسئولین فعال در بخش گردشگری منطقه به بررسی مخاطراتی که بر توسعه گردشگری تاثیر می گذارند، پرداخته است. نتیجه ای که از این تحقیق به دست آمد بیانگر بالا بودن احتمال وقوع مخاطرات بهداشتی و محیطی از دیدگاه گردشگران و همچنین مخاطرات ساختاری- عملکردی از دیدگاه مسئولین فعال در بخش گردشگری می باشد. اما در صورت محاسبه مجموع احتمالات خطر از دیدگاه هر دو گروه این نتیجه حاصل می شود که احتمال تهدید سیستم گردشگری محدوده مطالعاتی، در زمینه احتمال خطرات اقتصادی- مالی با مقدار 29/3 از همه بیشتر می باشد، شاخص احتمال خطرات بهداشتی- محیطی با مقدار 17/3 در رده دوم قرار دارد، بعد از آن شاخص ساختاری- عملکردی با مقدار 93/2 در رده سوم قرار می گیرد.کلید واژگان: مخاطرات, توسعه گردشگری, شهرستان سرعینIntroductionNowadays, tourism is internationally considered as one of the greatest economic sectors. Certainly, tourism is one of economically growing activities. In tourism systems, factors such as tourists, domestic people, the route and destination depend on external factors and the environment (e.g. socio-cultural, economic and political systems). Hence, the route which a tourist goes through from the residence to destination, tourism destination attractions, road network of the region, hoteling and fuel supply systems, visa issuing and official systems and many other factors are wholly considered as part of tourism system. For instance, the iron wall frontier between the North and South Korea in recent years has essentially halted the development of tourism system between these countries. Devastation of an airport in an island due to earthquake or storm possibly affects the development of tourism system.
Tourism hazards are defined as the possibility of occurring unpleasant events during the trip and especially at the destination. Tourism crises are defined as any event that may threaten usual activities and tourism-related operations and impact believes of tourists from fame, safety, attraction and tranquility point of view. These happenings increase cost of living and decrease entrance of tourists so that cause tourism economic loss and disruption of business activities in tourism sector. In the process of tourism development program, it is necessary to recognize and assess harmful factors exactly, so that we can prevent harming factors that cause losses in tourism system. Developing tourism is one of the issues which basically requires correct planning and management. In recent years, crisis management in tourism industry is considered as a basic requirement due to the increase of natural and political disasters in many destinations. Although crisis management researches are almost used in management and business for about 40 years, in 1990s, researchers and managers in tourism started to discuss this issue and presented methods to react against crisis in tourism industry. Generally speaking, tourism activities happen in a less-known environment and are susceptible to any event. Especial geographical environment of Sarein town has made this region as an important tourism destination in Iran. Generally, it is possible that development of tourism in this region is threatened by the hazards similar to the other tourism destinations. As a result, the aim of present research is recognition of hazards that affect the development of tourism in Sarein town and also cause crisis for development of this sector and as a result it is necessary to make suitable plan for them.
Material and MethodsIn this research a questionnaire was used to gather the necessary data. Indices that were used for gathering necessary data from previous studies include the possibility of political, legal, economic-financial, socio-cultural, environmental, technological, structural-operational and safety hazards. For each index some questions were determined and then gathered in a questionnaire.
Results and DiscussionFrom tourist´s viewpoint, the average for political risks is 2.43, from authorities viewpoint is 2.34 and finally the average for this kind of risk is 2.38. The average for legal risks from tourist´s viewpoint is 2.78, from authorities viewpoint is 3.06 and finally the average for this kind of risk is 2.42. The average for economic and financial risks from tourist´s viewpoint is 3.41, from authorities viewpoint is 3.17 and the final average for this kind of risk is 3.29. The average for socio-cultural risks from tourist´s viewpoint is 3.01, from authorities viewpoint is 2.74 and the final average for this kind of risk is 2.87. The average for environmental and sanitary risks from tourist´s viewpoint is 3.69, from authorities viewpoint is 2.66 and the final average for this kind of risk is 3.17. The average for technology risks from tourist´s viewpoint is 2.85, from authorities viewpoint is 2.78 and the final average for this kind of risk is 2.81. The average for structural performance risks from tourist´s viewpoint is 2.67, from authorities viewpoint is 3.20 and the final average for this kind of risk is 2.93. The average for safety and security risks from tourist´s viewpoint is 2.46, from authorities viewpoint is 2.94 and the final average for this kind of risk is 2.70.
For analysis of tourists and authorities view point with regard to risk possibility test (T), two independent samples were used. The test shows that there is not a meaningful difference between tourists and authorities view point with regard to the sum of risk possibility in developing tourism system.
ConclusionNowadays, tourism is interpreted as a system which is composed of different parts such as corporations, tourists, society and environment and each part of it is in relation with others. There are various factors that can threaten one or some parts of the system. This itself unfortunately has a negative impact on the whole system and causes problem for it. These threatening factors can harm tourists or the destinations. Also, occurrence of natural and social hazards in tourist regions through a decrease in the number of tourists harms tourism industry and the development of touristic destination development. The result of this research represented that the possibility of sanitary and environmental hazards occurrence was high from tourists point of view. Also, the possibility of structural-operational hazards occurrence was high from authorities point of view active in tourism sector. However, calculation of total hazards possibility from both tourists and authorities point of view represents that financial-economic hazards possibility with a value of 3.29 is the highest among all hazard categories. Consequently, if financial-economic hazard vulnerability of destination rises, this damages destination and causes problem for the town tourism development. The second and third highest hazards possibility values are 3.17 and 2.93 which are related to sanitary-environmental and structural-operational hazards respectively. As a result, to reduce these damages, we must make careful planning and reduce the vulnerability of tourism system. To show the difference between authorities and tourists view point, T test of two independent samples were used. The results of this test indicate that there is a meaningful difference between tourists and authorities view point about the sum of hazards possibility in development of tourism system.Keywords: Hazards, Tourism development, Sarein town -
تپه های باستانی، صحنه فعالیت انسان ها در گذشته های دور و نزدیک اند. این مکان ها ممکن است از بازمانده های اردوگاهی موقتی و یا ویرانه های یک دهکده یا شهر باشند. این تحقیق به زمین باستان شناسی تپه باستانی میمنت آباد با استفاده از روش میکرومورفولوژی اشاره دارد. این تپه در منطقه رباط کریم و در جنوب شرق روستایی به نام میمنت آباد قرارگرفته است. نتایج تحقیق نشان می دهد که قبل از استقرار ساکنان، شرایط گرم و مرطوب تری بر منطقه حاکمیت داشته است. با توجه به ساختمان میکروسکوپی مکعبی که شاخص نمونه های طبیعی منطقه است، در دوره ای از مقطع E تا مقطع D استقراری وجود نداشته است. مقطع C آخرین مقطع فرهنگی است و بعد از این مقطع، نشانی از آثار فرهنگی دیده نمی شود. در واقع چیزی که باعث شده این تمدن از بین برود، سیلاب حاصل از رودخانه شادچای است.کلید واژگان: تپه باستانی, میکرومورفولوژی, رودخانه شادچای, میمنت آبادThe ancient hills are the humans close and far activities sense. These places may be the transit camp survivors or ruins towns or villages. This paper studies the archaeology of the ancient hill of Meymanabad using micromorphology methods. This hill situated in Robat Kareem_in South-East village called Meymantabad. The result has showed that before the establishment of the site occupations there have been a warm and wetter conditions througout the region. According to the cubic microscopic structure that is the region natural examples index, a period lack of establishment from point E to point D has occurred. The point C is the latest cultural point and after this there are no cultural effects. In fact, what makes this civilization wiped out was the river flooding of Shadchay River resulted in the destruction of the site and caused the peoples to abandon their settlement areas.Keywords: Geoarchaeoogy, Ancient Hills, Micromorphology, Shadchay River, Meymantabad
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تغییرات اقلیمی و زمین ساختی نقش اساسی در تحول و تغییرشکل مخروط افکنه ها دارد. این پژوهش، به نقش تغییرات سطح اساس چاله میقان بر مورفولوژی مخروط افکنه های پیرامون چاله پرداخته است. برای انجام این پژوهش از بررسی های میدانی، داده های مغزه رسوبی چاه ها، تصاویر ماهواره ای و داده های رقومی ارتفاعی استفاده شده است. با مقایسه مغزه رسوبی چاه ها و درون یابی بخش های مشترک آن ها، حداکثر گسترش دریاچه مشخص شد. پس از استخراج مخروط افکنه ها، با توجه به تغییرات سطح اساس، مورفولوژی توالی مخروط افکنه ها، موقعیت زمین شناسی و حوضه های زهکشی، در بخش شمالی و جنوبی چاله مقایسه و تجزیه و تحلیل شد. نتایج نشان می دهد که تغییرات سطح اساس چاله میقان و فرونشست تدریجی چاله هم زمان با برخاستگی بخش حاشیه ای چاله که نشانه عدم تقارن و مورفوتکتونیک است بر مورفولوژی مخروط افکنه های پیرامون اثر گذاشته است. البته، اگرچه عامل تغییر اقلیم بر تغییر مورفولوژی مخروط افکنه های آشتیان، اراک و جزآن نقش اساسی داشته، نقش نوزمین ساخت بر تغییرشکل و تحول مخروط افکنه آشتیان نسبت به سایر مخروط افکنه ها موثرتر بوده است، زیرا در بخش شمالی پنج مخروط قدیمی تا جدید با اختلاف ارتفاع حدود 700 متر باعث عدم تقارن در منطقه شده است، در حالی که در مخروط افکنه های بخش جنوبی این توالی دیده نمی شود.کلید واژگان: تغییرات اقلیمی, تغییر سطح اساس, توالی مخروط افکنه, چاله میقان, نوزمین ساختIntroductionInteraction between of internal and external processes of the earth during time epoch have an important role in formation and deformation and landforms transformation, we can identify course of their processes changes with landform survey. In the inner parts of Iran is apparent several geomorphological evidence of dry and rainy climate changes. Playaes and lakes or generally internal holes had an important role in climate balance and ecological changes in the quaternary in its surrounding areas. Because of this their study has been considered always to determine past climate.Morphology and alluvial fan deposits, contains traces of past enviromental changes. The key issue is that be determined changes in alluvial fan processes, isthe result of which of tectonic factors, climatic and or geomorphological conditions of alluvial fans.Materials And MethodsTo conduct this research from fieldwork, are used sediment core data of wells and further satellite imagery and digital elevation data with different scales in different software enviroment.In this research with comparing the sediment core of wells in surrounding area of Mighan hole and interpolation of their common areas was determined maximum spread of the lake.after was tend to extraction of alluvial fans, then according to region morphology, are compared and analyzed geological structure and location, region drainage basins, base level changes and alluvial fans sequence in northern part of pit (Ashtians alluvial fan) and the southern part of the pit (alluvial fans of Arak, Tamar Abad, Mehr Abad).
Discussion and findngs: Finding from this research are presented as follows: Investigation of evidence of clay deposits of region and interpolation of core wells of Velashjerd, Taremozd and Mashhad Mighan, show about 57 meter water forasmuch as the same formation area for clay layers 90, 80, 120 meter this cores for Mighan lake in the quaternary.
Evidence of sediment of cores and clay sediments abundant in the western and southern proves that maximum deep of lake has been in western and southern slopes of craters and about 8000 to 16000 last year extent of clay sediments indicate wetter climate conditions and reflects the development and progression of the lake at that time.With study of region geological conditions and tectonic it should be state that clearly visible function of Talkhab and Tabrateh faults and also effect of craters subsidence on the drainage basin and alluvial fans surrounding the hole and that has been caused asymmetry on the northern slopes and should be stated that this region has been affected by the impact of Neotectonics.
Also with existance of same climate conditions for sedimentary basin Mighan we determined five base level changeson the northern slopes of the well (hole) for the Ashtian cone that 3 base level related to river redirection has been in effect of neotectonics activities and is not sensible for the next two levels detection of impact of climate and neotectonics function.
Including evidence of base level changes available evidence on the Ashtian alluvial fans indicates considerable activity of neotectonics processes during quaternary are:1) Creation of mound hills on the formations of quaternary epochthat are represented tectonic movements.
2) The effect of Talkhab fault line on quaternary sediments and quaternary landforms.
3) Existence of thick alluvial deposits that starts from 50 meter to 100 meter at the bottom of the cone. But base level change in southern slopes has not been caused alluvial fans sequence, existence large mound hills, fraction of alluvial fans and being abandoned cones level.ConclusionsThe result of the study show that the sequence of fine-grained sediments of silt and clay and sand and gravel in thecore of exploratory wells indicate enviromental changes particularly climate changes in the quaternary.Likewise the cause of climate change on morphology change of alluvial fans surrounding Mighan hole (Ashtian, Arak and etc) has been a major role, but was more effective neotectonics rule on deformation and development of Ashtian alluvial fan than the other alluvial fans.Because it is measurable in the northern part of five old cones to newcones with about 700 meters height difference while this sequence is not found in the alluvial fans of southern part.Base level changes of Mighan hole and hole gradual subsidence with rising marginal part of hole that indicate existence of asymmetry and morphotectonic for this hole, are effected on the morphology of around alluvial fans. In other words, neotectonics effects has been more effective than climate change in base level changes of Mighan hole at this region and this effects is caused asymmetry in North domain. According to the geomorphological evidence can be concluded that this Playa has been placed in dynamic tectonically. And climate change, especially neo-tectonic has been caused base level changes in Mighan playa.Keywords: base level change, climate change, Neotectonic, alluvial fan sequences, Mighan hole -
بهترین راه درجهت پی بردن به ویژگی های طبیعی سکونتگاه های باستانی در زمان برپایی آنها، بررسی های زمین باستان شناسی است. هدف از این پژوهش، بررسی نقش عوامل محیطی در مکان گزینی سکونتگاه های پیش از تاریخ دشت ورامین بوده است. پس از مطالعه ی شرایط محیطی دشت ورامین، هشت مولفه ی محیطی از جمله فاصله از آبراهه، ویژگی های زمین شناختی، آب وهوا، شیب، خاک، پوشش گیاهی، کاربری راضی و ارتفاع منطقه مورد بررسی قرار گرفتند و منطق فازی به عنوان روش مورد مطالعه در جهت دستیابی به نقشه ی پهنه بندی قابلیت های محیطی منطقه مورد استفاده قرار گرفت. سپس مشخص شد، قسمت های میانی مخروط افکنه ی جاجرود، دارای بهترین شرایط محیطی در جهت ایجاد سکونتگاه هستند. این مناطق، بر روی رسوبات آبرفتی دشت قرار گرفته اند که از نظر زمین-شناسی، شرایط مناسب را برای ایجاد سکونتگاه فراهم کرده است. وجود خاک مناسب برای کشاورزی و سفال سازی (خصوصا وجود رسوبات ریزدانه برای سفال سازی)، شیب بسیار ملایم، دسترسی مطلوب به آبراهه ها، داشتن فاصله ی مناسب از راس مخروط افکنه و تا حدی مصون بودن از خطر سیلاب و داشتن آب وهوای مناسب تر نسبت به قسمت های جنوبی مخروط افکنه، از جمله عواملی است که باعث ایجاد شرایط محیطی مناسب در این مناطق شده است و قرار گیری غالب سکونتگاه ها در این منطقه و استمرار سکونت آنها، خود این امرا را تایید میکند.
کلید واژگان: زمین باستان شناسی, عوامل محیطی, سکونتگاه های پیش از تاریخ, دشت ورامین, منطق فازیgeoarchaeological surveys are the efficient way to discover the environmental features of ancient settlements at the time of their establishment.. The purpose of this study was to evaluate the role of environmental factors in the site selecting of the prehistoric settlements in Varamin plain. In the archaeological view, the plains located in the southern foothills of central Alborz Mountains represent the Tehran plain and Varamin plain is laid in south east of Tehran plain, on the alluvial sediments of Jajroud River. After studying the environmental features of Varamin plain, eight characteristics of the natural environment, including the impact of geomorphologic features, geology, climate, vegetation, slope, land use and access to soil and water resources have been investigated and fuzzy logic was used in order to provide an environmental capabilities plain zoning map to establish settlements in Varamin plain. Results showed that the predominant Varamin plain’s prehistoric settlements are sited in areas with the good and very good environmental capability for establishing settlements and the most of these places are located on the central parts of Jajroor fan. Being located on alluvial deposits, suitable soil for farming and pottery, gentle slope, convenient access to streams, sufficient distance from the apex of the alluvial fan and being safe from flood risk And having better weather than the southern part of the alluvial fan are such factors That create suitable environmental conditions in these areas.Keywords: geoarchaeology, environmental factors, prehistoric settlements, Varamin plain, Fuzzy logic -
کوهستان زاگرس در بخش مرکزی با محیط جغرافیایی مساعد، مکان مناسبی برای شکل گیری استقرارها و جوامع انسانی است. وابستگی شدید جوامع انسانی این منطقه به محیط طبیعی سبب شده تا همواره تحت تاثیر شرایط محیطی و تغییرات ناشی از آن قرارگیرند. تغییر محیطی اوایل دوره هولوسن در نتیجه رخداد زمین لغزش کبیرکوه و متعاقب آن شکل گیری دریاچه های سیمره و جایدر، از جمله تغییرات محیطی است که طی هزاران سال الگوهای استقراری جوامع انسانی منطقه را تحت تاثیر قرار داده است. محدوده مورد مطالعه دریاچه جایدر و روش تحقیق توصیفی- تحلیلی و میدانی بود. از ابزارهایی مانند نقشه های توپوگرافی، زمین شناسی، تصاویر ماهواره ای، GPS و نرم افزارهای Arc GIS و Global Mapper جهت بررسی تغییر الگوی استقرار محوطه های باستانی استفاده شده است. مطالعه 27 محوطه باستانی شناسایی شده در حوضه رسوب گذاری دریاچه جایدر از یک سو منجر به شناخت الگوهای استقراری متفاوتی طی دوره زمانی فراپارینه سنگی تا اواخر دوران اسلامی در این محدوده شد؛ و از سوی دیگر، شناخت الگوهای استقراری طی این دوران، باعث روشن شدن وضعیت تغییرات محیطی حوضه رسوب گذاری دریاچه جایدر شد. نتایج نشان داد که الگوی استقرار محوطه های باستانی بعد از رخداد زمین لغزش کبیرکوه و تشکیل دریاچه جایدر، از دوره فراپارینه سنگی تا اواخر دوران اسلامی به تبعیت از تغییرات سطح آب دریاچه و ضخامت رسوبات پادگانه دریاچه بوده است .کلید واژگان: جبر محیطی, دریاچه جایدر, زمین باستان شناسی, محوطه های باستانی1-Introduction Geographical and natural potentials of Zagros and archaeological findings from the studies suggest that this cultural area has been used for human societies from pre-history to the present days. Many devastating earthquakes (The earthquake of 872 AD Saymareh) and a lot of landslides in the Zagros, caused severe environmental changes in this region. Landslide occurrence in Kabir Kuh,blocking the Kashkan and Seymareh river and subsequently formation of the Jaydar and Saymareh lake are among the most important environmental changes in this region. Kashkan River is one of the environments that provides a suitable environment to settlement in this area from past to the present. But environmental changes, especially Kashkan river redirections and formation of the Jaydar Lake, had significant effects on the settlement pattern of archaeological environments in the past. Therefore, the aim of this study is to investigate changes in settlement patterns of archaeological sites in the area of the jaydar lake after occurrence of kabir kuh landslide. 2-Materials and methods The Jaydar Lake located in the western parts of Pole-Dokhtar is considered as studied area. Field and descriptive-analytical research methods along with tools such as topographic maps, geologic, satellite images, GPS and other software like Arc GIS and Global Mapper are used to assess the changing process of the settlement patterns of archaeological sites. Then, extensive field studies have been done in the area and with observing the lake deposits at several points on the periphery of Khorramabad- Poldokhtar road;and then recording their heights, Lakes area has been drawn based on 740 meter contour. In the next stage, the position and period of archaeological sites on the lake area have been overlapped and using investigation of the height and thickness changes of sediments in the lake, the settlement pattern changes of the archaeological sites after formation of Jaydar Lake during the different periods have been analyzed. Finally, at the end of this study the results are presented. 3-Results and discussion kabirkuh Landslide, is the world's largest landslide and based on Thermoluminescence dating method on deep lake sediments amples of Saymareh lake, Kabir Kuh landslide time has been determined equal to about 15700 ± 2500 years. After the occurrence of landslides and blocking Kashkan river, Jaydar lake has been formed behind apile of sediments slide. Jaydar lake formation has coincided with the formation of the first stage of Saymareh lake. Because only in the first step, landslides had the most volume and vastness so that it blocked the Kashkan river path. Based on field studies Jaydar Lake area is calculated around 88 square kilometers. Chronologically, 27 archaeological sites have been identified in the area Show that archaeological sites have been created in the prehistoric, historic and Islamice period.The distribution pattern of the identified 27 Archaeological sites show that all the ancients ites are located in adjacent too rat a distance of less than 1000 meters far from the Kashkan River. Proximity to the waterand flatness of its surface have been the most important factors that affect the formation and distribution of archaeological sites adjacent to the lake. Other factors such as topography and fertile land are important in the formation of archaeological sites, have been affected by the water level of the lake and then by the river. So that the rise in water level is directly related to the height of archaeological site and the fertile lands in the margin of river. Investigating changes in the height and thickness of the lake sediments show that in the Bronze period we can observe the formation of a permanent establishment(or perhaps semi-permanent establishment) and adjacent cemetery for the first time. In addition, during this period we can see the formation of archaeological site on these dimentary terrace at the end of these dimentation basin of Jaydar lakes. 4- Conclusion The study of 27archaeological sites from the EpiPaleolithic period to the late of the Islamic period in the Jaydar lake sedimentation area showed that during this period, major changes in the settlement pattern of archaeological sites in the lake area have been occurred. All of these changes are directly related to the occurrence of kabir kuh landslides and the subsequent formation of Jaydar lake and its remaining sediments.Gradual risein water level, brought about loss of 6 human kind settlements in the late period of Epipaleolithic with average height of 695 meters from the open waters of in the lake margin and for cible migration to more elevated areas. It looks like that water in the Neolithic period reach to its highest level, 740 meters,and up to the end of this period remains at the same level. With beginning of the Chalcolithic period the height of the archaeological site areais reducedand areas that have already been buriedunder the water, in this period once they become residential. Formation of the first permanent settlement with in the Jaydar lake, coincides with the Bronze Age. In addition, residents of this area in this period of time for the first time build graveson lake and river sediments. Two periods of drought during the Iron Age cause the formation of Iron Age sites in the alluvium mountain path and near the river Kashkan. In the historical period(Achaemenid, Parthianand, Sasanian) much of the lake sediments(probably up to the entrance of Poldokhtar) have been dried. In historical period, archaeological sites to access the river have been formed in the closest parts to the river.The pattern of settlement in the early Islamic periodis not much different from the previous period. But at the end of the Islamic period and After over 5000 years, the basin sediments of Jaydar lake are dried and conditions for the formation of new settlements especially in the Jaydar plain area are provided.Keywords: Environmental determinism, Jaydar Lake, Geoarchaeology, Archaeological site
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هدف از این مطالعه، بررسی ترکیبات بار گردوغبار (شامل کانی شناسی، ژئوشیمی، عناصر سنگین و میکروارگانیسم ها) در غرب و جنوب غرب ایران و اثرات بررسی اثرات آن بر سلامت انسان است. به این منظور در طی پنج دوره رخداد گردوغبار در این منطقه، اقدام به نمونه برداری از ذرات گردوغبار شد و جهت تعیین مناطق منشا و گستردگی رخداد گردوغبار در دوره های نمونه برداری شده، از تصاویر شاخص آئروسل سنجنده OMI و مدل HYSPLIT استفاده شده است. جهت تعیین بار گردوغبار از آنالیزهای XRD، XRF، جذب اتمی و بررسی های آزمایشگاهی برای تعیین میکروارگانیزم ها استفاده شد. نتایج نشان می دهد کانی های اصلی گردوغبار ورودی به غرب ایران شامل کربنات ها (کلسیت) و سیلیکات ها (کوارتز) است و فاز فرعی کانی ها نیز شامل ژیپس می باشد. هرگاه منشا ذرات شمال شرق عربستان یا نواحی داخلی عراق در حوزه رسوبات تبخیری رودخانه های دجله و فرات باشد، نمونه های حاوی کانی ژیپس خواهند بود. همچنین اکسیدسیلیس (SiO2) و اکسید کلسیم(CaO)، ترکیبات شیمیایی غالب ذرات گردوغبار را شامل می شوند و درصد هریک از عناصر وابسته به منشا گردوغبار متفاوت خواهد بود. میزان غلظت عناصر سنگین در تمام نمونه ها از حدمجاز تعیین شده برای سلامت انسان بیشتر بوده و میزان آن وابسته به مسیر انتقال ذرات و منشا آن است و بیشینه آن در مناطقی است که ذرات بیشترین تماس را با آلاینده های صنعتی و شهری داشته اند و طولانی ترین مسیر را تا غرب و جنوب غرب ایران طی نموده اند. همچنین بیشترین میکروارگانیزم-های جدا شده شامل انواع باسیلوس برای باکتری ها و آسپرژیلوس برای قارچ ها است. گونه های شناخته شده میکروارگانیزم های فرصت طلب بیماری زا برای انسان و حیوان می باشند. بنابراین گردوغبار مهم ترین مخاطره برای سلامت ساکنان نواحی غربی و جنوب غربی ایران محسوب می شود.
کلید واژگان: گردوغبار, کانی شناسی, ترکیبات شیمیایی, میکروارگانیسم ها, غرب و جنوب غرب ایرانIntroductionDust storm is one of the most important natural phenomena and a kind of severe natural disaster that begins and diffuses under the influence of atmospheric systems. It occurs frequently in desert lands and their surrounding areas in arid and semi-arid regions. The main factors influencing amount of dust in the air are precipitation، vegetation cover، and wind velocity and particle size of soil in source of dust. Over the past decades، Middle East dust storms have caused many problems for the residents of South and South West regions of Iran. Now it is going to change into the main persistent environmental problem in Iran and the Middle East region. The Middle East dust has great impacts on quality of the inhabitant’s lives، visibility and transportation، micro-climate، ecosystem، communication systems and consequent crisis such as، eco – social and environmental problems in the west and south west of Iran. Different aspects of this phenomenon in the Middle East have already been considered by researchers. The aims of this study are to (1) understand the possible source (s) of West of Iran Dust storms and (2) determine the geochemical، mineralogical، trace metals and microbiological characteristics of dust particles in the west of Iran. Study Area: The study area from which sampling was performed، include two provinces of Kermanshah (45. 24-48. 30 E and 33. 36-35. 15 N)، and Khuzestan (47. 42°–50. 39° N and 29. 58°–32. 58°N) which are located close to the Iranian border with Iraq in western Iran. This region comprises 38 cities and a population of more than 6،000،000 people. Topographic elevations in these provinces vary between 0 m (in beaches) and 3701 m (Menar Mountain in Khuzestan province). Fig. 1. The Study AreaMaterial And MethodsIn this study، five severe dust storms in the west and southwest of Iran have been selected. The air sampling was performed in Ahvaz and Mahshar Cities in Khuzestan province، Kermanshah and Qasre-Shirin cities in Kermanshah province. Dust samples were collected to obtain PST by using the high-volume Air (HVA) samplers (Anderson and TCR models) and the fiberglass filters used to get particles. The flow rate of the HVA sampler was 1 M3/min. Also، for some times the sampling was performed by using Low volume Air (LVA) sampler. After the calibration of air sampler، the particles were got from sampling stations، which were located at urban areas in these cities on the height of 2 meter above the ground. The sampler was run continuously for a period of 24 h. Then، the HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) model is applied by using a backward trajectory approach in the study periods. The OMI imagery aerosol Index is used to determine the main sources of dust storm. The mineralogy، Sample elemental analyses، toxic trace elements analysis، Microorganisms Analysis of airborne dust samples were analyzed by XRD، XRF، Atomic Absorption and culture-based assays respectively.Results And DiscussionThe outputs of HYSPLIT model and aerosol index from OMI imagery show that main sources of DS1 are the area between the west bank of Euphrates and east bank of Tigris in middle of Iraq، deserts lands in south east of Iraq and north east of Arabian Peninsula. In DS2، the main sources of dust are south and southeast of Syrian Desert، an area between Euphrates and Tigris، Nafud desert in north of Arabian Peninsula، and the coastal region in east of Arabian Peninsula. The main sources of dust in DS3 are South of Syrian desert، North of Arabian Peninsula (Nafud desert)، middle and south of Iraq. The dust sources in DS4 are Syrian Desert، the area between the west bank of Euphrates and east bank of Tigris، deserts lands in south of Iraq and for DS5 are Syrian Desert، desert lands in west of Iraq، the area between Euphrates and Tigris in middle and south of Iraq. The XRD analysis show that in all samples، quartz، calcite، albeit، muscovite، clinochlore and dolomite are common minerals. But other minerals such as gypsum، orthoclase، actinolite and palygorskite are present in some samples. XRF analyses of dust samples show that chemical compositions are SiO2 (34. 82%)، CaO (20. 48)، Al2O3 (8. 44%)، Fe2O3 (4. 36%) and MgO (4. 22%). Based on Atomic Absorption analysis، the average concentrations of heavy metals include Zn، Pb، Cd، Cu، Ni and Co are 472. 2، 109. 2، 10. 4، 52. 0، 111. 2 and 21. 0 PPM respectively. Ambient airborne dust microorganisms including the six bacteria species belonging to the genus Bacillus، Staphylococcus، Escherichia coli، Klebsiella، Pseudomonas and Enterobacter were found in dust samples. Also four fungi species isolated were Aspergillus، Rhizopus، mucor and Penicillium، that is common in environment.ConclusionThe outputs of HYSPLIT model and aerosol index from OMI imagery show that the main sources of airborne dusts for western Iran are dry lake beds and rivers، alluvial deposits and desert lands in Iraq especially the area between the west bank of Euphrates and east bank of Tigris and Hur-Al-Azim lagoon، east، northeast and southeast of Arabian Peninsula، east of Syria and secondary sources of dust storm in the west of Iran with low level quantity are desert land on Africa and Khuzestan province in Iran. The results of XRD analyses show that the main mineral loads are Quartz، Calcite، Gypsum، Albeit، Muscovite، Clinochlore and Dolomite. XRF analyses of dust samples show that the main chemical compositions are SiO2، CaO، Al2O3، Fe2O3 and MgO. Based on Atomic Absorption analysis the mean of heavy metal in dust storm is more than standard level. The microorganism analysis shows that the dust particles are contaminated with bacteria and fungi.Keywords: Dust, Mineralogy, Chemical Composition, Microorganism, West, Southwest of Iran
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