Mesozoic tectonics in Korea

Mesozoic tectonism in Korea is characterized by polycyclic and reiterated intracratonic deformations, which include (a) strike-slip movement of ductile or brittle-ductile shearings, (b) compressive phase of folding, thrusting and transpression of strike-slip movement and (c) extensional phase of basin formation by normal or domino fault system and transtension of strike-slip movement. It occurred during three events; Songnim, Daebo and Bulgugsa orogeneis. Late Permian to Early Triassic Songnim orogeny can be divided into two stages. In the early stage, ductile shearing has affected the southwestern part of the Ogcheon Belt and northwest-trending folds developed in the Paleozoic sedimentary sequences. During the late stage, folding and thrust movement have affected the Paleozoic rocks and produced northwest-trending folds and thrusts which moved toward the southeast. When the Songmin orogeny was diminished, post-tectonic granites were emplaced and the Daedong basins were formed by extensional tectonic fields. The Daebo orogeny follows the deposition of the Later Triassic to Early Jurassic Daedong Group, which inclues northeast-trending folds and thrusts. This phase was continued on the Songnim phase, in which folds and thrust faults had similar trends and transport directions. The Songnim phase was then associated with high angle thrust faults. During the late stage, brittle-ductile strike-slip faults predominated, and produced pull-apart basins along the contact boundary of the Ogcheon belt. S-type granites were emplaced with the northeast trend. From the Late Cretaceous to Early Tertiary periods, the Bulgugsa orogeny produced east-west trending folds and thrusts. Thrust movements prevailed ini the northeastern part of the Ogcheon belt, whereas other areas were affected by east-west trending folds. Sedimentary rocks in the pull-apart basins were affected by transpression and produced en-echelon arrays of folds and flower structures. Mesozoic tectonism in Korea can be correlated to Indosinian, Yanshanian, and Sichuanian tectonisms in China.