Paleostress reconstructions based on calcite twins in the Joseon Supergroup, northeastern Ogcheon Belt (South Korea)

초록

Paleostress of the Joseon Supergroup in the northeastern part of the Ogcheon Belt, South Korea, is reconstructed in the Jecheon-Danyang area with the help of calcite twinning. In the study area, the average twin thickness and intensity increase with the total twin strain increase. From the appearance of twins, the average twin thickness and intensity, and the total twin strain, it is estimated that calcite twins were produced under temperatures lower than 200 degrees C. The maximum shortening axis in the study area changes orientation from northeast-southwest to NNW-SSE or northwest-southeast, and finally to north-south. We suggest these three distinct stages with different orientations of the maximum shortening axis can be correlated with: (i) the Paleozoic to Early Jurassic Songrim orogeny; (ii) the Early Jurassic to Late Jurassic Daebo orogeny; and (iii) the Cretaceous Bulgugsa orogeny.

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