Movement history of the Andong Fault System: Geometric and tectonic approaches

The Andong Fault is one of the E-W trending boundary faults that separate the Cretaceous Gyeongsan Basin from the surrounding basement. Several reverse faults are developed parallel to the Andong Fault, and these faults together with the Andong Fault are named collectively the Andong Fault System. The fault system is characterized by significant fault drags. Structural features enable us to analyze the geometry and slip vectors of faults, on the basis of which we can develop an understanding of the related tectonic setting. The results of the analysis of the fault drags indicate that the Andong Fault System had a largely reverse motion. The major movement of the hanging wall was mainly toward and southeast and partly toward the south. The ages of pre- and post-reverse faulting plutons indicate that the reverse movement of Andong Fault System occurred between the Cretaceous and the Early Tertiary times. In addition, considering the distribution of strata, the Andong Fault might have played the role of a transfer fault during the E-W extension of the Gyeongsang Basin, from the early stage of the opening and throughout the basin development.