The introduction of Kouh-sorkh nappe thrust system in north of Taknar wedge, in NE Iran.

Abstract Adjacent to the northern margin of the Taknar wedge, south of the Sabzevar zone, and along to the Kuh Sorkh Mountain, there are huge conglomeratic blocks have been attributed to Oligocene. These blocks were dispersed onto the sedimentary beds with almost same age and material. Based on the Kadkan geological quadrangle map, a pronouncedunconformity was considered between these litho-stratigraphical units. The extensive field excursions as well as satellite image studies led us to have a different idea regarding the relationship between the two mentioned units.  The evidences such as a clear and extensive detachment zone between the units, several overturned to recumbent folds with vergences toward northeast, a number of northeast and southwest dip-slip thrusts, a pervasive shear lineament, and a tectonic window in the southwest of Kadkan, however, totally represent a huge thrust-nappe system along the Kuh Sorkh Mountain.  Indeed, the thrust-nappe system described here is composed of a huge north- to northeast-verging recumbent fold, which its southwestern limb moved probably a few hundred meters upon the northeastern limb. Accordingly, the huge dispersed conglomeratic blocks are the remnants of the resistant part of the southwestern allochthonous fold’s limb.We call these remnants as the Kadkan klippe assemblage.The existence of such a thrust-nappe system could represent a considerable shortening perpendicular to the Kuh Sorkh strike after the Oligocene time.  This reality could also document the notable distribution of strain around the Sangerd fault.