Despite the absence of fossil, the Jangsan Formation was conventionally interpreted as lowermost strata of the Cambrian-Ordovician Joseon Supergroup on the basis of conformable contact with overlying Myobong Formation. Recent study, however, suggest that geologic age of the Jangsan Formation is Neoproterozoic, which is based on U-Pb detrital zircon age dating and unconformable contact with overlying Myobong Formation in Dongjeom section. One of a key to this controversy is regional correlation study with boundary characteristic between the Jangsan and Myobong Formations. However, previous studies are limited to a few regions. To adopt these approach, this study carry out sedimentological study of newly discovered section so that try to correlate with previous studies.
Sedimentary facies of the Jangsan Formation in the study area are divided into four types: Slightly stratified sandstone(Ss); Gravelly sandstone(Sg); Graded sandstone(Sgr); Massive mudstone(Fm). Slightly stratified sandstone and Gravelly sandstone facies are classified into lithic subarkose(group A) and arkosic litharenite(group B), respectively. Provenance of sandstone from Group A and B is on field of recycled orogen and transitional arc tectonic setting, respectively. In the facies association, the study area is interpreted to be mainly controlled by sediment supply and eustasy. Depositional environments of the study area are interpreted as transition from river-dominated delta to continental shelf by transgression with time.
Compared with previous studies, many sedimentological differences are confirmed, including petrology, provenance and depositional environments. This study suggests that more regional sedimentological studies should be carried out before studying the boundary characteristics between Jangsan and Myobong Formations.