Paleostress from calcite twins of limestone and its tectonic implication in South Korea

초록

In order to examine paleostress and tectonic implications, calcite twins in limestone distributed in South Korea were used. The average twin thickness and intensity increase with increasing the total twin strain. Calcite twins in the study area as an indicator of deformation temperature might be produced at temperatures lower than 2008C approximately, being considered for the total twin strain, the average twin thickness and intensity and morphology of calcite. The maximum shortening axes calculated from calcite twins show the NE-SW or NEE-SWW, NW-SE or NWW-SEE and N-S or NNWSSE directions. These maximum shortening directions are consistent with many fault directions developing in the study area, in particular with the NE-SW main tectonic direction in the Korean Peninsula. Paleostress results from present and other previous studies suggest that the NE-SW maximum shortening direction during the Late Permian to Early Triassic Songrim orogeny in the Korean Peninsula can be compatible with the Indosinian orogeny in China and the Sangun orogeny in the Japanese Island. The NW-SE maximum shortening direction during the Jurassic to Early Cretaceous Daebo orogeny can be compatible with the Yanshanian orogeny in China and the Hida orogeny in the Japanese Island and the N-S maximum shortening direction during the Late Cretaceous to Early Tertiary Bulgugsa orogeny can be compatible with the Sichuanian orogeny in China.

키워드