مجله زمین ساخت
پیاپی 24 (زمستان 1401)

Diapir is a process in which material with a lower specific weight rises from the upper layers, breaks them and appears on the surface of the earth. In this process, the type of salt's response to the applied stresses creates specific geomorphological forms, which study is important due to the presence of oil resources, the establishment of human settlements, and the passage of communication routes.Failure to pay attention to salt diapirism studies in construction projects can cause their failure.In this research, which was conducted with the aim of investigating the geomorphology caused by salt diapirs, in the south of Semnan privance and with field, library and Remote Sensing methods, it was found that salt deposits cause the creation of specific geomorphological structures and shapes through the creation of tension. local cracks, surface dislocations and tensile fractures.Also, the fluidity of salt has been created on the surface structures and their dimensions are effective, and these structures, in turn, create local forces and control the morpho-geo-structural situation of the region.In addition, the dissolution process has played an important role in the formation of salt karsts in the region and has created significant shapes.Based on this, the geomorphological forms resulting from the Salt diapirismof the region were identified and in three groups of building forms including salt domes, salt anticlines and salt walls, salt karsts including dolines, ponors, karns and forms resulting from hydrological processes including valleys, springs, salt fluxes and salt glaciers were classified.

The Pazanan anticline is one of the most important condensate gas reservoirs in Iran, which is located in the southeastern part of the Dezful Embayment with a northwest-southeast trend.The structural analysis and deformation of this anticline based on the interpretation of existing subsurface data(including 3D-seismic data and drilled wells data) indicates that the folding style of this anticline in the Asmari reservoir and older formations is faulted asymmetric detachment folding.Based on the structural interpretation of the tops of the Asmari, Sarvak, Fahliyan, Gotnia formations and a deeper horizon(probably top of the Kangan) in the transversal seismic sections of the Pazanan anticline, it could be divided into 3 main culminations known as southeastern, central and northwestern, which are separated from each other by saddles.The interpretation of the observed seismic data and stratigraphic column clearly shows that the sedimentation thickness of formations, especially the Late Cretaceous and Paleocene,have been reduced due to the uplift of the Hendijan-Izeh Paleo-high, so that the Ilam and Gurpi formations have not been deposited or eroded in the Paleo-high area.The interpretation of the Asmari reflector in the seismic time slices, with assuming that the changes in the spatial dimension (along the axis of the Pazanan anticline) are equivalent to the changes in the time dimension(during the folding time of the anticline);shows folds growth in the central and southeastern culminations of the Pazanan anticline were simultaneously but separately,while the northwestern culmination of this anticline started to folding after increasing the deformation and finally connected to the central culmination.

Until now comprehensive studies have been carried out by various researchers on the structural and geometric model of the Mosha-North Tehran fault system. As a structural lozenge with an general WNW- ESE trend, this fault system is located in the southern flank of Alborz Mountain range where is considered a part of Alpine-Himalayan orogenic belt. The mentioned system consists of Mosha fault zone to the NNE and North Tehran fault zone to the SSW which has experienced various left-lateral or right-lateral strike slip mechanisms with contractional or extensional components during the geological time. NW-striking thrusts, the Purkan- Vardij Thrust (PVT) and Emamzadeh-Davud Fault (EDF) are also considered as other remarkable structural features of the region. The studied structural zone has gone through several uplifts and subsidences from the Mesozoic to the present day. This means that in the study area, the phenomenon of inversion tectonics has occurred many times and so, extensional and contractional regimes have interchanges alternately to each other. For example, during Oligo-Miocene, due to the northwestward movement of the South Caspian Basin with respect to the Eurasia, inversion tectonics turned a transtensional (right- lateral with extensional component) environment into a transpressional (left- lateral with small contractional component) one. In this research, a new structural model has been presented, based on which the study area is formed by an interchangeable half-negative flower structure and half-positive flower structure.

Land subsidence is a natural hazard characterized by gradual movement, resulting in financial losses and, occasionally, loss of life. This research employs interferometric radar techniques to study morphological changes in the Kahrez Plain aquifer. The extent of land subsidence in the Kahrez Plain aquifer is investigated using Sentinel-1 satellite imagery from 2014 to 2023. This aquifer is situated in the western subsidence of Lake Urmia and is predominantly composed of limestone lithology. The geological structure in the area comprises inclined layers and the effects of fault activity. Microscopic examinations of rocks from the region reveal dual fractures, displacement, collision, and simultaneous rotational phenomena, indicating the role of tectonics in shaping the existing structures in the area. According to the interferometric analysis results, no land subsidence has been observed in the Kahrez Plain aquifer during the study period, and the uplift ranges from 0.34 to 1.51 meters. Regional deformation, resulting from changes in landforms such as earthquakes or tectonic activities, could be a significant factor contributing to the notable uplift.

Structural and petrological evidence suggests an asymmetric and two-sided subduction of the Sistan oceanic lithosphere under the Lut and Afghan blocks. The subduction under the Lut block was characterized by a steeper dip angle and a higher subduction rate, leading to the retreat of the plate boundary towards the ocean and subsequent back-arc extension. Studies on the geochemistry and possible origin of the mafic-intermediate igneous rocks of the Lut block corroborate the occurrence of crustal thinning and back-arc extension, highlighting the significant role of subduction in their formation. In this research, we employed laboratory or analog modeling with scale lengths to simulate the characteristics of the Sistan oceanic lithosphere subduction and the geodynamic processes in eastern Iran. We investigated the parameters controlling the style of subduction by examining the sinking of a thin viscoelastic silicone putty sheet with varying geometric and rheological properties in a glucose syrup-filled reservoir. Our findings revealed that an increase in length and thickness, coupled with a low viscosity ratio of the lithosphere and asthenosphere, accelerates the subduction rate. We also identified a significant correlation between the dip angle and the subduction rate. In summary, the deformation of the back-arc region was analyzed through kinematic investigation in the performed experiments. The experimental outcomes, which confirm the high rate and dip angle of subduction, and also the back-arc extension, can be identified as characteristics of the Sistan Ocean’s subduction zone under the Lut block.

The folded Zagros is a part of the active Zagros belt in the southwest of Iran. This area has main faults and active rock formations, the activity of these faults has somehow affected the strata and sediments of different geological periods. In this study First, by studying satellite images and aerial photographs, five locations were selected in different parts of Fars and the hinterland of Bandar Abbas, and finally, the tectonostratigraphy of these locations was compared with each other. The sinology column and the paleogeographical map of these regions in the Miocene period were reconstructed Using the data obtained from five places of folded Zagros (Bastak, Bahar anticline, Arjan plain, Saadi mountain and Yasouj). The obtained results and the resulting diagrams were obtained using the RockWorks geological program. the minimum and maximum stratified thicknesses of the Miocene period formation in these five studied points are related to Arjan Plain and Saadi mountain sections By comparing the obtained results and the Hesar diagrams and the isopach map. It was done between the studied locations, which shows the highest thickness of this formation in the Arjan plain section and the lowest thickness is in Saadi Mountain. The facies changes of sedimentary rocks of the Miocene period seem to be due to the operation and activity of bedrock faults such as Kare Bes, Sabzpushan, Sarvestan and Kazeron faults in this region.