Tectonics
Rojin Hamidi; mohamad reza ghassemi; mohammadreza sheikholeslami
Abstract
Continuation of the compressional regime within the convergence zone between the Central Iran and Turan rigid blocks caused thrusting of old rock complexes over the recent sediments. As a result of multiple thrusts and folds, the area uplifted at the same time and the Binalud range have been shortened. ...
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Continuation of the compressional regime within the convergence zone between the Central Iran and Turan rigid blocks caused thrusting of old rock complexes over the recent sediments. As a result of multiple thrusts and folds, the area uplifted at the same time and the Binalud range have been shortened. This study attempts to evaluate the amount of shortening of the Binalud mountains by reconstruction of a balanced cross-section. Field data from the Dulat-Abad-Neyshbur transect, study of the geological units and décollements along the section, and the Move® software environment are used as the basis for this research. Based on these information, four tests were carried out for balancing the cross section in question. The first test, which used the arc and polygon method for the horizons and a listric fault without floor thrust, failed to display the deformed section. In the second test the section was drawn, however the deformed structure did not balance the section in the process of unfolding the fault bend folds. In the third and fourth tests, we used the kink method to restore the deformed state to an undeformed section. For the third test, deformation was proceeded from the hinterland, and in the process of restoration, a shortening of about 65% was revealed. The fourth test was proceeded from the foreland, and taking into account both the foreland uplifts and shortening, the amount of shortening of Binalud range was estimated to about 26%. The final structural model defined a thin-skinned fold and thrust belt which included fault-bend-folds with out-of-sequence and in sequence duplexes. Major décollement horizons defined in the region include: 1) shale horizons within the Silurian-Devonian rock units, 2) medium-bedded dolomite and limestone layers within the Bahram Formation, and 3) evaporitic layers in the Eocene sediments.
M Khademi; F Ghaemi; S.K Hosseini; F Ghaemi
Abstract
In this paper, the feedback or interaction between tectonic and surface processes in the Binaloud Mountains and Neyshabour plain has been investigated. To achieve this, we have used topographic data, recorded earthquake data provided by the Geophysical Institute of Tehran University (Mashhad center) ...
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In this paper, the feedback or interaction between tectonic and surface processes in the Binaloud Mountains and Neyshabour plain has been investigated. To achieve this, we have used topographic data, recorded earthquake data provided by the Geophysical Institute of Tehran University (Mashhad center) and field surveying results. Surface processes affect the propagation of tectonic thrust wedges in orogenic belts. In regions where tectonic processes have led to an increase in the surface slopes due to development of mountain highs, surface processes will justify the uplifted areas by smoothing the slopes, eventually shedding off a massive load of clastic sediments into the foreland basin. Because of their huge weight and volume, these sediments prevent the forward propagation of the wedge and therefore increase the accumulation rate of stress in the orogenic wedge. Also the increase of fault-plane dips in the orogenic wedge will make the slip along the fault planes hard or even impossible. Formation of out-of-sequence faults and back-rotation of preexisting thrust faults may be considered as results of these accumulated stresses. North Neyshaboor thrust fault is a later or secondary structure and can be considered as an out-of-sequence thrust because it cuts other thrust sheets and limbs of folds. Our research shows that the high volume of Paleogene/Neogen sediments in the Neyshabour foreland basin has prevented the forwards (southwestward) propagation of the Binaloud mountain range as the orogenic wedge. Releasing of the accumulated forces has therefore led to the development of the North Neyshaboor out-of-sequence fault and back-rotation of former thrust faults.
M Allameh; S Saadati Jafarabadi
Abstract
The Dalichai Formation is among marine deposits in Jurrasic period that has a geographic expansion in north of Iran. In order to palynological studies in eastern part of the BinaloudMountains an outcrop of this formation, in the bar village was selected. The thickness in bar village section is 255 meters ...
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The Dalichai Formation is among marine deposits in Jurrasic period that has a geographic expansion in north of Iran. In order to palynological studies in eastern part of the BinaloudMountains an outcrop of this formation, in the bar village was selected. The thickness in bar village section is 255 meters includes dark gray shales. The study of 112 slides of 28 samples taken from this formation showed that the most of the samples contain palynomorphs specifically dinoflagellates. 53 species belonging to 27 genera of dinoflagellates were identified. According to dinoflagellates, a middle Jurassic age was determined for the Dalichai Formation in the Bar village section. Based on the study of three main groups of phytoclasts, marine palynomorphs and amorphic organic matters and result of the statistical studies of different factors, sedimentary environment of the Dalichai Formation in studied section was open marine basin with shallow and low oxygen condition.
