Structural geometry of the Seongjuri syncline, Chungnam Basin

Chungnam Basin has been known as one of the largest Mesozoic basins in Korea, filled mainly with so-called Daedong Supergroup. The basin has evolved as the Early to Middle Jurassic intra-arc volcano-sedimentary basin developed on top of the Late Triassic to Early Jurassic post-collisional basin in this area, recording evolutionary history of the Mesozoic tectonics in the southwestern Korean Peninsula. This study carries out the geometric interpretations of the Seongjuri syncline and its surroundings in the central part of the Chungnam Basin, based on detailed structural field survey. Based on its doubly-plunging fold geometry, the Seongjuri syncline could be subdivided into the southwestern and northeastern domains. On the down-plunge profiles of the southwestern domain of the Seongjuri syncline as well as the underlying Okma fold, the Okma fault shows typical geometry of a basement-involved reverse fault that propagated up to the sedimentary cover. The profiles illustrate that the Seongjuri syncline occurs in front of the tip of the Okma fault, likely implying its origin as a part of the fault-related fold system. The result of this study will provide better insight into the structural interpretation of the Chungnam Basin, and will further provide useful information for the Mesozoic orgenic events of the southwestern Korean Peninsula.