Structural Evolution of the Southern Margin of the Ulleung Basin,

Abstract

Mapping of eleven regional unconformities and the acoustic basement in the southern Ulleung Basin margin, East Sea (Japan Sea), identified from multi-channel seismic reflection data, provides insights into the structural evolution of the area. The four shallow (Late Miocene, Early Pliocene, early Late Pliocene, earliest Pleistocene) unconformities are mappable over the much of the study area; the rest are seen mostly in the northern two thirds of the area, bounded to south by large NEtrending reverse faults. Smaller NE-trending reverse faults are also seen in the northern part of the area. The contractional tectonism, responsible for the reverse faults, consists of at least two phases: (1) the latest Early to late Late Miocene and (2) the late Late Miocene to Quaternary (?) phase. The first phase of uplift created anticlinal structures in the northeastern part of the area. The second phase formed relatively shallow anticlines in the southwestern part of the area. The second phase was accompanied by significant transpressional strike-slip movements in the southeastern part of the area.