Geological Museum KIGAM

Cenozoic strata are characterized by subbasins... Cenozoic strata are characterized by subbasins scattered along the East Sea coastline, and are composed of Tertiary Miocene (23-7 Ma) land deposit the Yangnam Group, marine deposit the Yeonil Group, and others. There were lots of extrusions of basalts during these times, continued until the Quaternary times, and formed volcanic islands such as Ulleung and Jeju Islands and Chugaryeong Rift Zone.

Mesozoic strata are mainly land deposits... Mesozoic strata are mainly land deposits composed of the Daedong Group and the Gyeongsang Supergroup. the Daedong Group was accummulated in Early Jurassic times (ca. 230-170 Ma), and is mainly distributed over Gangwon-do (Yeongwol area), Chungcheongnam-do (Boryeong area), Chungchengbuk-do (Danyang area), Gyeongsangbuk-do (Mungyeong area), and mid-region of Pyeongannam-do. Compared to the Daedong Group, the Gyeongsang Supergroup accummulated during the Cretaceous times (ca. 140-65 Ma) is widely distributed over mainly the Gyeongsangnam-do and the Gyeongsangbuk-do.
Due to diastrophism (Songnim) that started in the Middle Triassic times, the Daedong Group accummulated in land depositional environment different from the Pyeongan Supergroup of the late Paleozoic times, the Daebo diastrophism occurred at the end of deposition of the Daedong Group during Late Jurassic to Early Cretaceous times. Due to igneous activities that followed during the times of these two diastrophisms, Songnim Granites and Daebo Granites each intruded widely over the Korean Peninsula. At the late stage of accummulation of Gyeongsang Supergroup in the Cretaceous sedimentary basin, acidic or basic volcanic rocks extruded and Bulguksa Granites intruded.

Paleozoic strata are divided into the Cambrian-Ordovician... Paleozoic strata are divided into the Cambrian-Ordovician (ca. 540-440 Ma) Joseon Supergroup and the Carboniferous-Permian (ca. 320-250 Ma) Pyeongan Supergroup based on sedimentation times. The Joseon Supergroup mainly accummulated in a marine environment, and is distributed over Gangwon-do and Pyeongannam-do regions. Campared to the Joseon Supergroup, the Pyeongan Supergroup was accummulated at an environment that started from a shallow marine one, then gradually transitioned into a land deposit that had lacustrine or wetland environment. The Pyeongan Supergroup is mainly distributed over Taebaek and Yeongwol areas of Gangwon-do, and mid-region of Pyeongannam-do.

Excluding partial Archean rocks distributed... Excluding partial Archean rocks distributed over the Nangnim Massif and the Gyeonggi Massif, the Precambrian strata are composed of metamorphic complexes formed by repeated Paleoproterozoic recycling of crust-forming material extracted from the mantle mostly during the Neoarchean times. These metamorphic complexes form the basement bodies for the Nangnim, Gyeonggi, and Yeongnam massifs which are major component blocks of the Korean Peninsula. At Meso- to Neoproterozoic times, Meso- to Neoproterozoic strata of the Sangwon Group, lower Okcheon Group, and others accummulated along the southern Nangnim Massif and Okcheon Belt, and there were multiple intrusions by granitoids along the western Gyeonggi Massif.