Discussion on structural development and stratigraphy of the Kyokpo Pull-Apart Basin, South Korea and tectonic implications for inverted extensional basins

Abstract

S. B. Kim, S. S. Chun & S. K. Chough write: Lambiase & Bosworth (1995) suggested that the Kyokpo Basin, southwest Korea opened as a pull-apart basin in the Late Cretaceous and underwent inversion (transpression) and uplift in the late Miocene. They attributed both the basin opening and inversion to the India–Asia collision, assuming that the tectonic history of the basin was analogous to that of neighbouring rift basins in eastern China. This led them to the conclusion that the inversion tectonics of the basin resulted from local changes in stress along a strike-slip fault system. They stated 'All the structural features observed in the Kyokpo Basin actually are the product of a complex, but single, regional tectonic event (India–Asia collision)' and thus 'It is neither necessary nor desirable to invoke major changes in regional structural geometries to explain the evolution of this basin' (p. 469) (our italics). It is, however, unrealistic to attribute the formation of the Kyokpo Basin to the India–Asia collision. The collision occurred after 70–65 Ma ( Klootwijk et al. 1992 , 1994 ), whereas sediment filling of the Kyokpo Basin had already commenced prior to 97–75 Ma, as indicated by the ages of andesite and basalt flows interlayered within the lower part of the sedimentary sequence of the basin (Table 1). Moreover, the age of opening of other Cretaceous strike-slip basins (akin to the Kyokpo Basin) in Korea is known to be as early as Valanginian–Hauterivian ( Seo 1985 ; Choi et al. 1995 ). Also, the neighbouring basins in eastern