جستجوی مقالات مرتبط با کلیدواژه "پادگانه" در نشریات گروه "جغرافیا"

Terraces are important archives for paleontology. In this research, the paleotemperature changes and discharge frequency of Jajroud basin in the northeast of Tehran have been investigated based on the sedimentology and geochemistry characteristics of the reservoirs. First, the sediment samples were analyzed with calcimetry, EC, XRF, and PH techniques, and then these data were correlated with the indices of salinity, chemical weathering, acidity, and maturity of the sedimentary layers of the defenses. The results show three periods of flow changes, during the alternation of cold and warm periods of the river. One is at the peak of the glacial period, when the accumulation of snow and ice in the mountainous part has reduced the discharge (before the Holocene). In the second stage, by passing from the glacial period to the warm period (11 to 8 thousand years ago), Jajrud has experienced its highest discharge. Because the melting of glaciers has been accompanied by rainfall. The existence of very coarse layering in the early Holocene terraces indicates the occurrence of floods in this period. In the third stage, the dominance of recent hot and dry conditions (8 thousand years ago until now) and the lack of glacial deposits have led to a decrease in river flow. Based on this, the geochemical studies of the reservoirs can provide valuable data to recover the dynamic changes of flow and discharge during the Quaternary period and can be generalized to other similar basins.

River terraces represent a history of river stratigraphy and provide valuable information for understanding the interactions of tectonics, erosion, and climate change. The high altitude of the Jajrood basin has resulted in extensive glacial remnants, especially the accumulation of moraines upstream of the basin. The extent of moraine depositions under the upstream basins of the Jajrood River is not evident in the structure of river terraces and they do not have a uniform elevation. Moreover, the relations of old glacial conditions in the sedimentary interference of terraces cannot be easily reconstructed and discriminated, and there is no regular order in the stratigraphic sequence and sedimentological conditions of the river terraces. The moraine deposition seemingly has had a major role in the differences in river terrace sequences from upstream to downstream of the study area, which calls for further investigation and is also addressed in this study. Many studies have delved into the analysis of the evolution of the river terraces. Other important areas of study include paleontology and sedimentology and their effects on the canal sustainability against flow dynamics. This study aimed to explore the climatic and neo-tectonic developments of the Jajrood River Basin and the role they have played in creating terrace sequences.

This pure research investigated the role of neo-tectonic developments and climate change on the formation and evolution of terraces in the Jajrood River Basin. The research was based on analytical calculations and reports prepared through surveys as well as remote sensing methods to examine the effects of tectonics in the area. In addition, sedimentological evidence was studied to see how climate change has affected the formation and evolution of these terraces. The primary research tools were topographic and geological maps alongside aerial photographs and satellite images. Other fieldworks such as terrace morphometry using GPS measurements and sedimentological analysis helped to add insight to the findings. Then, the data was analyzed in ArcGIS. Here, the Jajrood Canyon was divided into three sections to better examine the morphogenesis of the terraces. Next, the transverse profiles and stratigraphic sections were drawn up to investigate the sedimentary strata in each section through morphometry, and then the evolution of the terraces was analyzed and reconstructed. The tectonics were studied using radar images to determine vertical displacement through the small baseline subset (SBAS) time series. Here, 27 Sentinel-1 images were used for the period from Oct. 14, 2014, to Oct. 27, 2016. which was performed using Generic Mapping Tools (GMT) in Linux OS. After preparing the interferogram maps, a map of the displacement in the study area was generated using the SBAS method (Zhao, 2013). Moreover, changes in the climate were studied using sedimentological and stratigraphic evidence.

The research findings can be classified into two parts. First, neo-tectonics was investigated through remote sensing methods and the analysis of vertical displacement across the region. Then, the effects of these neo-tectonic processes on the genesis and evolution of terraces were examined. In the second part, the effect of climate change on terrace developments was explored using sedimentological and stratigraphic evidence. In the first part, the region's tectonics was analyzed using radar imagery. In doing so, the vertical displacement was measured using SBAS time series and 27 Sentinel-1 imagery during the period from Oct. 14, 2014, to Oct. 27, 2016. The specifications of the research images are presented in Table 1. The images were selected based on the research purpose and the baseline of the images relative to each other. The VV polarization was used for all images since co-polarizations exhibit a stronger backscatter. Some sensors have different polarizations, and images with different polarizations can inform interpretations to a great extent.After preparing the images, for measuring displacement using the SBAS method, first, the temporal and spatial baseline of the images was examined and image pairs were selected for interferogram generation (Table 2 and Figure 3), which was performed using GenericMapping Tools (GMT) in Linux OS. After preparing the interferogram maps, a map of the displacement in the study area was generated using the SBAS method. In the end, the role of morphotectonic relations in the morphogenesis (i.e., origin and development) of the terraces were examined.

These findings suggest that terraces in the Jajrood Canyon are highly heterogeneous in terms of sedimentological structures, stratigraphy, and altitude. For instance, the T3 to T1 terraces, respectively, were located 130, 90, and 80 m above the river. These terraces have also experienced three intermittent processes. These three river terraces were created through the combined effects of climate change, tectonic uplifts, and the formation of dam lakes. The results of SAR interferometry (InSAR) and fieldworks also confirm the effect of active tectonic uplift differences along the main canal. These differences reflect the differences in their morphogenetic processes. The altitude of the terraces at the Oushan River tributary (Section 1) is nearly 130 meters. However, this section's altitude downstream (near Hajiabad Village) is estimated at 90 m. This difference cannot be merely due to baseline discrepancies. Evidence indicates that a sedimentary interference originating in the lake due to a past landslide downstream of the study area (Hajiabad landslide) is the cause of the higher altitude of the terraces in this section. The terrace sequences were not the same in any of the three sections. To be more precise, there are three identifiable terrace levels in Section 1, two in Section 2, and one in Section 3. In addition to the differences in the tectonic baseline, three factors—namely climate change, moraine, and the formation of a landslide-dam lake downstream—were identified for the genetic diversity, sequence differences, and terrace sequences throughout the three sections. In addition to morphometric differences, there were great differences in the genesis of the terrace sediments. The river has contributed the most to the formation and structure of terraces and their genesis. Nevertheless, the interference of landslide-dam lake deposits, moraines, and alluvial deposits, consecutively or simultaneously, have affected particularly sections 1 and 2 through differences in flow dynamics. Meanwhile, greater uniformity can be seen upstream, particularly in the Garmābdar basin (Section 3), such that upstream terraces in this section are predominantly glacial.

During the Quaternary, tectonic forces have been implicated in climate change as a result of landforms or deformations in the ancient forms of the Haraz Valley. The terraces are solid landforms from the Quaternary period whose study of environmental changes during this period. But in the studied basin, in addition to climate change and intrusive fault-tectonics, volcanic activity has had the greatest impact on the processes governing the region. Haraz basin Although it has an area of more than 3779 square kilometers and is located on the border between East and Central Alborz, its basin is different from other neighboring basins. So that their forms and processes are genetically incompatible with processes in the region and exhibit specific structural complexity. One of the available forms is the diversity of alluvial surfaces that can be observed along the Haraz valley. Given that the totality of these alluvial surfaces, due to the youngness of the Haraz Valley, does not coincide with the present river process, the most important issue that may arise here is that these erosional surfaces have their effects on the slope. The Haraz Mountains are visible, were they merely influenced by the flow dynamics of the Haraz River? Otherwise what factor or factors contributed to the formation of these levels. There are three hypotheses for achieving the morphogenesis of Haraz terraces in the study area:A: Damavand lava intrudes through the valleys into the main valley of Haraz and forms a barrier lake in its upstream, forming morphogenesis of alluvial terraces of Haraz;B: Morphogenesis of haraz terraces is caused by glacier activity in the area;C: Damavand volcano deposited its pyroclastic material along the main arterial path of the Haraz and formed this vast surface of alluvial terraces in the area;

To this end, analytical and temporal reconstruction methods of change have been employed. The technique is based on comparing the morphometry of lake terraces and glacier-pyroclastic dams with four methods of rehabilitating the study area, comparing the height and thickness of alluvial sediments, determining the extent of lake sediment distribution, and recovering the extent of barrier confinement.

Investigating the findings of the research and their comparisons and analyzes, it can be concluded that the terraces of the Haraz valley in this area are significantly different in terms of the thickness and height of the sediment and in the processes affecting their formation and alteration. The height of the alluvial surfaces at the outlet of the Gazane valley is 630 m. However, the height of alluvial surfaces in the Abe Ask reaches 200 meters above the river bed. The highest elevation of the terrace is at the outlet of Fire Valley to Haraz 2065 m. Therefore, this difference in altitude of the alluvial surfaces is not only related to the change in the basement level, but also to the interplay of glacial and volcanic activity of Damavand. The sequence of alluvial terraces is not evident in all the studied periods. While in the water of the ski in the travertine (interval 1) four levels, in the six intervals, four levels and in the Nova range three levels are visible. Other areas have an alluvial terrace surface. The genesis of the sediments of the terraces under study indicates a significant difference. Although the glacier has the most significant activity in producing and consequently the formation of alluvial terraces in this region and is dominant in genus, volcanic pyroclastic sediments have been active in sync with the glacier and evidence of temperature volcanic activity is observed among all glacial sediments. So that they are sometimes deposited on ice in the form of a Lahar layer and occasionally as a layer of ash or other pyroclastic material.Various researchers have already commented on the creation of lava barrier lakes in the Haraz Valley and the valleys around Damavand Peak (Alaei Taleghani, 2012; Yamani et al., 1977). Many are full of ice, not yet. Damavand's new volcano, which coincides with glacial and interglacial periods, has been able to throw pyroclastic and lava materials out of successive eruptions.

The results showed that the elevation levels of the terraces had both an elevation difference and an irregular sequence. The highest level of alluvial terrace in the Nell Mountains is 630 m above the Haraz valley bed, indicating that in addition to changing the basin level, glacial processes have been a factor in elevating alluvial levels in the area. Surveys showed that the lake was formed during two periods due to the closure of the valley by the activity of glacier and volcano together. This lava barrier was gradually broken during the Holocene and nowadays the depositions of the old lake are visible across the Haraz valley.

Review of river terraces is main issues related to river geomorphology. They are areas with low slope that is parallel to the axis of the river valley and are in the higher levels of the river bed and created through cutting the river bed and response to changes in external factors such as climate, tectonics and base level. Ghezel owzan River is as one of the longest river systems in the country, responded well to changes in external factors (climate, tectonics and base level). For this purpose, after dividing the river into nine periods, Profile was drawn on the terraces adjacent faults in order to study in terms of height level and symmetry. In order to assess the effect of Tectonic activity on Ghezel owzan Catchment area, Four sub-basin are studied: Divandareh, Zanjan rood, Gharanghochay and Hashtchin- Tarom, from Upstream to downstream , With the help of two indicators, River Gradient length (SL) and Valley floor width to valley height (Vf) by determined sections, The results indicate the relationship building terraces with tectonic factors. This means that form terraces in downstream river is more a reflection of the effects of neo-tectonics and tectonic if they originate, reflecting the effects of tectonics. Feedback such activities is in basin downstream for nested alluvial fans and vertical-walled terraces in bedrock and in the mirage nested terraces in alluvial sediments with low sides slope.

Introduction
Investigation of river terraces is one of the main issues in the field of river geomorphology. River terraces, as a medium of alluvial landforms and heritage of stratigraphy, are widely investigated by geomorphologists to understand the tectonic and climatic time. The formation of alluvial terraces is primarily the result of tectonic rise alongside the cycling cycles. The edges of a river that is hard and resistant to geology are wall-bound or steep sloping, similar to water-breakers, and limit the number of the steppes to the alluvial terraces; but on the sides with a looser lithology, alluvial terraces are formed with a slight slope. Go up or down to the basin or the sea level changes are accompanied by a change in the slope along the river, creating tectonics alluvial terraces. Ghezel Owzan River, as one of Iran''s longest river systems, has well responded to lithological and tectonic factors. The Ghezel Ozan Basin is located in the northwest of Iran, and in latitude of 34° 53'' 21" to 37 ° to 56'' 2" north and longitude is 46 ° 27'' 43" to 49 ° 19'' 43 "east. The origin of the Ghezel Ozan River is from the heights of Chehel Cheshmeh Kordestan and with a length of more than 550 km, after crossing Zanjan, East Azarbaijan and Ardebil provinces, along with several streams along its path, intersects in the Guilan province with the river Shahroud and enters the reservoir of the Sefidrood Dam.
Accordingly, river terraces are lithologically divided into marl, crystallized and conglomerate periods with the help of geological (1/100000) and topographic (1/50000) maps and using computer software such as Arc, GIS, Global Mapper, and Excel. River path is also lithologically and tectonically divided into eight periods and profiles of each period are drawn. In order for the collection of information, we have translated several English articles and examined various internal sources related to the subject matter of the research. With the help of geological maps and field observations of the region, we investigated the effect of tectonics and lithology on topography (symmetric-asymmetric) on alluvial terraces. Using the Global Mapper, the cross-sectional profile was mapped along the river''s perpendiculars and analyzed.
Results show that from among the major lithologies of Ghezel Owzan terraces (marl, crystallized, and conglomerate), marl terraces are more asymmetric and crystallized terraces are more symmetric in areas without tectonic movements. Symmetrical terraces are formed in areas without tectonic movements or in areas with the same tectonic movements on both sides with resistant lithology. Asymmetrical terraces are also formed in areas where tectonic movements are not the same on both sides or in areas where there are marls in-between geological layers. Marl lithology, which is the dominant lithology of the basin, has the greatest impact on the asymmetry of terraces on this river. Tectonic has been active in A, C, E, F & H periods and inactive during B, D & G periods.
Discussion and Conclusion On the bed of the Ghezel Ozan River and major parts of Dyvandra to the Miyaneh, Qareaghaj and the greater part of the province of Tarom, it is overcome with Marl Lithology (Hashtchin to Khalkhal, upper and lower part of Hashtrood and Turkmen Chay, southern provinces of Miyaneh and Zanjan, middle section of Sojas). The conglomerate sediments are the dominant lithology of Qazlazan from Soltaniyeh to Nikpay and the upper of most major branches. The irregular dispersion of lithology and faults in different parts of the Ghezel Ozan River makes it impossible to sequentially divide the alluvial terraces. In resistant lithology, alluvial terraces of symmetrical are formed and in the marl lithology, the slope of the arches of the arches provided the possibility of a deep cut and, with deep erosion and common landslides in the transverse surfaces, low-calorie alluvial terraces is created with low altitude difference. Another factor in the asymmetric of the alluvial terrace is the lithology of the basalt and limestone of the Ghezel Ozan River terrace that act as a barrier and by reducing the river slope and reducing the erosion of the water, the river is forced to move horizontally before the strait, the degradation of the compressive levels has led to asymmetry of the terraces and denser plains.

An area of 2900 square kilometers of the Dashtiari district of Chabahar, which is about 3450 square kilometer wide in total, was studied. Research on the evolution of landforms in different sectors shows that the features of the region have come to their current form by orogenic and epeirogenic processes as well as external processes. However, these processes exhibit dry characteristics of Dashtiar. The oldest rocks in the north are related to the late Cretaceous and the north of colored mélange, and the oldest deposits are in Dashtiari, belonging to late Miocene, and consisting of a set of rocks and fine-grained marl-conglomerate. The coastal landscapes of the Omani coast include Hezar-Darreh (a thousand valleys), muddy flows of the marl, hills of the tafoni caverns, deep watercourses of coastal plains, two sandy beach lanes, sandy hills, desert zones of clay marl. The geomorphologic phenomena of the Omani coast include mud volcanos, sea terraces, coastal, foothill and alluvial plains, alluvial cones and hills. In the glacial period and the period between glacial periods, water and wind are the dominant factor of erosion respectively, and the laminated terraces and exploratory and mechanical erosion are evidences of rainy periods in this region.