Cenozoic deformation history of the area around Yangnam-Yangbuk, SE Korea and its tectonic significance

Detailed mapping and structural analysis were carried out to establish the Cenozoic deformation history of the Yangnam-Yangbuk area, SE Korea. All structural elements were analyzed to establish the chronological sequence, based on the classification of the fracture systems and the ages of the rocks. Two detailed grid maps represent the deformation history, based on the cross–cutting relationship between deformation fabrics.We established the Cenozoic deformation history in the studied area by synthesizing the analysis of structural elements in rocks of different ages and observing cross–cutting relationships on grid maps. Results using these two approaches, with two independent data sets, are consistent. The deformation history is comparable to that proposed from previous studies. Restoration of the structural elements suggests tilting and rotation in this area.There is clear evidence of tectonic inversion, which was observed in a previous trench study of the Eupchon Fault. This implies that normal faults related to the right-lateral Yangsan Fault associated with opening of the East Sea (Japan Sea) may have been reactivated as thrust faults in the Quaternary period.