Document Type : Original Research Paper
Authors
1 Ph.D. Student, Faculty of Basic Science, Islamic Azad University, North Tehran Branch, Tehran, Iran
2 Associate Professor, Faculty of Basic Science, Islamic Azad University, North Tehran Branch; Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran
3 Professor, Faculty of Basic Science, Islamic Azad University, North Tehran Branch, Tehran, Iran
Abstract
The Kopet Dagh zone has been an area interest for geologists due to its sedimentary and structural similarities to the Zagros zone. In this study, the Jozek-Ghetlish main fault is introduced using the results of field studies, remote sensing, stratigraphic changes and seismic activities. The studies show that in terms of seismicity, the earthquakes of August 1943 (Ms 7.6) and February 1976 (Ms 4.3) are the most important events recorded on this fault. From stratigraphy point of view, the facies changes from Shoorijeh formation to Zard formation from east to west is the most obvious stratigraphic change across the fault. Thickness variation (Isopach) maps of the Shoorijeh formation also show that its sickness decreases westward to zero adjacent to the fault, where the Zard formation thickens in the same direction. Deflected and offset stream channels across the southern part of the fault indicate a sinistral displacement along it. The streams draining the Yemendagh mountains in south of Ashkhane are deflected westward across the fault, and some of them show offsets of about 60 to 130 meters. In addition, in the northern part near the reservoir of Shirin Dareh dam, the axis of the syncline supporting the dam reservoir represents a sinistral displacement in the Aytamir sandstones. Further to NE, also, fold axis displacements in the Amirabad syncline, the Miyansoo anticline and even the Gifan syncline are other indications of the left-lateral motion along the fault. According to the NE-SW trend of the fault, its sinistral mechanism, and its effect on the tectonic zonation of this region, the Jozek-Ghetlish fault can be considered as the structural boundary between the eastern and western Kopet Dagh. Also, based upon stratigraphic thickness and facies variations across the fault (Zard and Shoorijeh formation), it can be a key to understand the Kopet Dagh oil reservoirs.
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