The Gongsuwon Thrust in the Taebaeksan Basin is one of the important regional structures for the Phanerozoic tectonic evolution of the Korean Peninsula. The late Early Jurassic Bansong Group (Daedong Supergroup) is structurally overlain by the early Paleozoic Joseon Supergroup along the thrust in the Yeongwol area. We present four lines of evidence indicating that the siliciclastics of the Bansong Group suffered a prelithified deformation within the fault zone of the Gongsuwon Thrust; (1) strainfree quartz clasts both in the hinge and limb areas of isoclinal folds of the sandstone layer, indicating granular flow, (2) intact gravels in the conglomerate with pressure shadows filled by sandstone or shale matrix, (3) injection of mud into sandy layers, and (4) lensoidal marble blocks (Joseon Supergroup) with plastically deformed calcite grains within siliciclastics of the Bansong Group. We suggest that the deposition of the Bansong Group and the thrusting were coeval during the middle Mesozoic Daebo tectonic event.
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ACKNOWLEDGMENTS: We appreciate the detailed and constructive comments by S.K. Chough and an anonymous reviewer. We also thank D.K. Choi and S.K. Chough for the introduction of the fault zone outcrop to us and helpful discussions. This work was supported by the Korea Research Foundation Grant (KRF-2007-313-C00763) to J.-H. Ree.
- Bansong Group
- Daebo tectonic event
- Gongsuwon Thrust
- Granular flow
ASJC Scopus subject areas
- General Environmental Science
- General Earth and Planetary Sciences