Geological structures of the Taean formation in the Gomseom area, southwestern Gyeonggi massif

The western Gyeonggi Massif, where records evidence of Phanerozoic subduction/collision tectonics, is an important area to understand the crustal evolutionary history of the Korean Peninsula. This study presents geometric and kinematic characteristics of the geological structures of the Taean Formation in the Gomseom area, southwestern Gyeonggi Massif. We interpreted the geometric relationships between structural elements, and conducted stereographic and down-plunge projections for structural domains. As a result, at least three different deformational events (D₁, D₂ and D₃) are recognized in the study area. In the first deformational event (D₁), regional foliations being well defined by the preferred orientation of muscovite and biotite were formed. In the second deformational event (D₂), NNE-trending low-angle contractional faults and related crenulation lineations/ cleavages were formed. The crenulation lineations shallowly plunge toward SSW~SSE or NNW~NNE. In the third deformational event (D₃), SE-plunging folds and NE-trending high-angle faults were formed as ‘fault-related fold’ and ‘fold-accommodation fault’, indicating that the D₃ folds and faults are genetically linked to each other. This contribution provides important insights into the structural evolution of the Taean Formation along western Gyeonggi Massif, where had evolved as subduction/collisional orogenic belts in the East Asia.