The Geometric and Kinematic Analysis of Soltan Anticline in Zagros Fold-Thrust Belt; An Evaluation of the Dehram Group Closure

Soltan anticline is located in northwest of the Zagros fold-thrust belt in the Lorestan Province. Geometric and kinematic analyses of the anticline have been carried out to estimate the closure of the Dehram Group in order to evaluate its potential for gas reservoirs. Geometric analyses of the Soltan anticline indicate that the fold geometry is rather similar to that of the Trishear type of fault propagation folds. However, considering the competency contrasts between various rock units in the anticline that control the fold's geometry, together with the rounded and relatively wide outline of the anticline at surface, the Soltan anticline can also be compared to faulted detachment folds that hold the same geometry as the fault propagation folds. On the other hand, the very low values of finite strain measured on clastic rocks collected from the anticline and its typical smaller scale fold constraint, and the low values of the layer parallel shortening are comparable to the kinematics of fault propagation folds. Based on the data from the geometric and kinematic analyses, seven structural cross sections across the anticline are drawn, and using the cross sections, a structural contour map and a 3D model for Dehram Group are constructed. The calculated values for the anticline closure prohibits this structure as an appropriate host to gas reservoirs, unless the Soltan anticline is connected to the adjacent, Rit, anticline.