Geology of the Deogsan-myeon area, Jecheon-gun, Chungcheongbuk-do, Korea: contact between the Choseon and Ogcheon supergroups

The study area is located in the Deogsan-myeon area, Jecheon-gun, Chungcheongbuk-do, where the contact between the Ogcheon and Choseon supergroups is exposed. The limestone sequence in the area can be divided into three formations based on the lithology: 1) Deogsanri, 2) Otiri, and 3) Dojeonri Formations in ascending order. The Deogsanri Formation is correlated to the Mungog Formation whereas the Otiri Formation to the Yeongheung Formation of the Yeongweol-type sequence (Choseon Supergroup). The lithofacies of the Dojeonri Formation is different from any other formations of the Yeongweol-type sequence and conformably overlies the Otiri Formation. The contact between the Choseon and Ogcheon supergroups appears to be conformable at the Bonghwajae section. The Seochangri Formation overlies the Choseon Supergroup and is conformably overlain by the Puknori Formation. The lowermost part of the Seochangri Formation consists of quartzite (27 min thickness). Amphibolite occurs in the contact area between the Choseon and Ogcheon supergroups. The lowermost boundary with the quartzite of the Seochangri Formation shows an intrusive contact, whereas other boundaries are diffused. At a few sites, the vesicular structures in the amphibolite are well preserved and amphibolite did not affect to the Puknori Formation. Therefore, the emplacement of the amphibolite occurred after the deposition of the Seochangri Formation and before the deposition of the Puknori Formation.