Comment on "Depositional age and petrological characteristics of the Jangsan Formation in the Taebaeksan Basin, Korea-revisited" by Lee, Y.I., Choi, T. and Lim, H.S.

Abstract

An underpinning theme of Lee et al. (2016a, Journal of the Geological Society of Korea, 52, 67-77) is based on an invalid observation/interpretation of "unconformity" between the Jangsan Formation (quartzite) and the overlying Myobong Formation (shale). Re-examination of the Dongjeom outcrop section along the floor of the Nakdong River indicates that the irregular boundary between the two formations is not representative of a depositional (primary) sedimentary structure, but a post-depositional (secondary) deformation structure caused by subsurface faulting. The irregular fault contact is not parallel with bedding of the overlying Myobong Formation. Cataclasite and fault gouge are present along the irregular boundary, and fault gouge is injected into the fractures of the quartzite. Such injection occurs only in the fault zone. There is no evidence of a substantial break of sedimentation or gap in the geologic record across the irregular boundary between the two formations. Their further assertion on the stratigraphy, depositional age, provenance, and the paleogeography of the two formations is thus rootless.