Cretaceous stratigraphy and geologic history of medial Kyongsang Basin: tectonics and volcanism

Abstract

The Palgongsan Fault comprises growth fault, dormant, and strike-slip phases. The strike-slip phase is manifested by the Palgongsan strike-slip fault, which sinistrally offsets the Palgongsan Granite and the earlier strata. The Palgongsan strike-slip fault shows various amounts of slip within the extent of the fault, but the maximum observed slip is about 5.5 km as measured in the Hasandong Formation. During the earlier phases of the Palgongsan Fault, faulting, sedimentation, and igneous activity were inter-related. Identifications of other major faults have enhanced the local stratigraphic study. A border area astriding the Milyang and the Uisong subbasins shows complicated stratigraphy reinforced by the lateral encountering of the stratigraphic schemes of the two subbasins. The stratigraphic complexity is exemplified by the Jindong Formation which is ramified, into local stratigraphic units, the uppermost one being the Konchonri Formation. In spite of doubts on their stratigraphic relationship, our observations prove that the Konchonri Formation overlies the Chaeyaksan Volcanic Formation. The chronological sequence of the volcanisms in the Kyongsang Basin has been summarized.