Department of Geology, Faculty of Sciences, Tarbiat Modares University


The NNW-trending Dena Fault, with 140 km length, cuts the major structures of Zagros Fold-Thrust Belt in Borujen region. The fault has divided the region in two zones, in which different structural, andmorphological features as well assedimentation and seismtectonic characteristics have developed. This study presents a new interpretation for the kinematics of Dena Fault based on field evidence. Precise field mapping and structural analysis in four structural traverses across the Dena fault zone indicates that it composes of several sub parallel surface fault segments with right-lateral strike-slip to reverse right-lateral fault mechanism. Coincidence of the Dena Fault with the T-11 aeromagnetic lineament as well as evidence on the fault activity on isopach maps from Cretaseous to Miocene time implies that the north segment of the Dena Fault has kinematics relation to this lineament. The low angle between the general trending of the mapped fault segments on the surface with the trend of the aeromagnetic lineament implies their close relationship. Therefore, it is proposed that the mapped fault segments are the Riedel shear faults of an active deep-seated strike-slip fault on the surface. In addition, the proposed kinematics for the Dena Fault is compatible with the focal mechanism of earthquakes epicentered along the fault. The result of this interpretation documents that the Dena Fault is a basement fault with right-lateral strike-slip mechanism.