Document Type : Original Research Paper
Authors
1 Assistant Professor, Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran
2 Associated Professor, Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran
3 Ph.D., Geological Survey of Iran, Tehran, Iran
4 Assistant Professor, International Institute of Earthquake Engineering and Seismology(IIEES), Tehran, Iran
5 Professor, Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran
Abstract
The Kaseh Mast anticline located in the south of the Lurestan zone, is one of the small-scale anticlines in the Lurestan (in north) and the Dezful Embayment (in south) zones in the Zagros fold-thrust belt. This anticline and the adjacent anticlines are affected by the Balarud blind thrust fault zone, which is a part of the Mountain Front Fault. The Mountain Front Fault is a major topographic front that be traced along the Zagros fold-thrust belt in the Izeh, Fars, Lurestan and Dezful Embayment. The field observations and geometric analysis indicated that the axial trend of the Kaseh Mast anticline has been changed and shows asymmetrical, noncylindrical and disharmonic fold, with vergence to southwest. The class of folding is 1C subclass of Ramsay's classification. To determine the geometry of the fold the termsof open for tightness, wide for aspect ratio and subrounded for relative curvature are suggested. In addition, this anticline is analyzed by using of geometrical models. Basically, this model allows quantitatively predicting the Balarud blind thrust fault zone trajectory and displacement from the geometric characteristics of this anticline. The comparison of the anticline with the theoretical fault-related folding models suggests the Kaseh Mast anticline as an Asymmetrical Detachment Fold that is affected by the Balarud fault zone. It is probable that the folding process of the Kaseh Mast anticline is in early states of the formation of a detachment fold. However, the folding mechanism of the adjacent anticlines is fault-propagation folding. The changing of the folding mechanisms of this anticline and the adjacent anticlines from detachment (in Kaseh Mast anticline) to fault-propagation folding (in the Siah Kuh and Chenareh anticlines) is probably referred to several parameters. These include the effect of thrust, the position of the Kaseh Mast anticline in Zagros fold-thrust belt, the distance of the anticlines related to the Balarud fault zone and the potentiality of the changing of the folding mechanisms of triple fault-related folding to each other.
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