--> Abstract: Basin-Forming Tectonics of the Cretaceous Gyeongsang Basin in Southeast Korea and Its Implication on Crustal Evolution in the Eastern Asian Continent, by Daekyo Cheong and Kosuke Egawa; #90039 (2005)

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Basin-Forming Tectonics of the Cretaceous Gyeongsang Basin in Southeast Korea and Its Implication on Crustal Evolution in the Eastern Asian Continent

Daekyo Cheong and Kosuke Egawa
Kangwon National University, Chuncheon, South Korea

The early-stage basin-forming tectonics of the Cretaceous Gyeongsang Basin in South Korea was revealed from analysis of conglomerate provenance for the Sindong Group, the lower part of the Cretaceous Gyeongsang Supergroup, and description of a newly defined cataclasite belt along the Jurassic Honam strike-slip duplex. The conglomerates of the Sindong Group include granite, quartzite, blackish quartzite, mylonite, ultramylonite, and mudstone gravels, which are rich in the gravels derived from the basement rocks in and around the Yecheon Shear Zone, especially from the Taebaeksan Gneiss and Schist Complex distributed around the Homyeong Fault, whereas rare in the gravels derived from the Daebo Granites. A large amount of the mylonite gravels in the basin strongly suggest that the Honam strike-slip duplex had been already cropped out before the formation of the Gyeongsang Basin, which is evidenced by uplift of the southern Korean Peninsula in the duration between the Jurassic dextral and Cretaceous sinistral strike-slip motions. Activity of the Homyeong Fault was likely concerned in formation of the Nakdong Trough according to the study of conglomerate provenance, and also implies tectonic inversion from the Middle Jurassic dextral to Early Cretaceous sinistral strike-slip movements.To consider paleoposition of the pre-Cretaceous Japanese Islands, the Gyeongsang Basin is regarded as a pull-apart basin formed by effect of a slip on divergent fault segments because the basin had been sandwiched between the Hida Marginal Island Arc Belt of SW Japan and Honam strike-slip duplex which include the Early Cretaceous cataclasite zones. It presumably had a large influence to formation of the Nakdong Trough that the Japanese Islands elongated in the north-south direction had been rapidly converged nearby the Nakdong Trough by the sinistral deformation and displacement mainly in Barremian to Aptian.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005