Stratigraphic Implications Of The Pyeongchang Group (Joseon Supergroup) In Korea

The early Paleozoic Joseon Supergroup in Korea has been divided into Taebaeg, Yeongwol, Pyeongchang, Yongtan and Mungyeong groups, depending on the sequence of lithology. Among than the Pyeongchang Group distributed in Pyeongchang area is composed of the Jeongseon and Iptani formations. Because the Jeongseon Formation shows the similar lithological characteristics in the Pyeongchang and Yongtan groups, the basic difference between the two groups is the presence of the Iptani Formation. Schist and crystalline carbonate rocks are present in the lower part of the Iptani Formation and crystalline limestone becomes dominant upwards. In the uppermost part dark and light crystalline carbonate rocks are intercalated. Because the Iptani Formation is distributed along the strike direction of the Jeongseon Formation, stratigraphic interpretation of the Iptani Formation is not reasonable. Also, Because the schist (or phyllite) of the Iptani Formation are stratigraphically equivalent to the shale (or phyllite) of the Jeongseon Formation and the stratigraphic position of the intercalations of dark grey and milky white limestone are similar in both formations, the Iptani Formation should be considered to be the Jeogseon Formation which was altered and recrystallized by magma intrusion during the Mesozoic. Therefore, the Pychang Group should be regarded as the Yongtan Group.