Development of regional uplift and uplift-related strata in Gunsan Basin, Yellow Sea: implications for Cenozoic crustal extension

Abstract

The Mesozoic–Cenozoic Gunsan Basin is the northeastern part of the Northern South Yellow Sea Basin between eastern China and the Korean Peninsula. On the basis of seismic interpretation, this study presents and interprets geologic features of regionally uplifted structures, the Haema Arch, located in the central western part of the basin. The Haema Arch is defined as dome-shaped uplift complexes, 95 km long and 60 km wide. It is characterized by prominent basement uplifts along its margin and plunging syncline inside the arch. The marginal large-scale uplifts are bounded by outward-dipping faults. The uplift-related strata are identified on the hanging wall block of the bounding faults and within the Haema Arch, which can be divided into pre-, syn-, and post-uplift units. The pre-uplift unit rests on the acoustic basement and shows an upturned stratal pattern near the marginal large-scale uplift. The syn-uplift unit locally occurs on the hanging wall block of the bounding faults along the northern and southern margins. The uplift of the Haema Arch and its coeval fault-controlled subsidence possibly occurred during the late Oligocene. The post-uplift unit initially formed on remnant topographic lows during the early Miocene and subsequently covered the overall area of the Haema Arch and the Gunsan Basin. The late Oligocene uplifting of the Haema Arch can be interpreted as an isostatic response to tectonic unloading by the arch-bounding faults that possibly extend to detachment faults. We suggest that the Gunsan Basin underwent crustal thinning and extensional deformation during the late Oligocene, which accounts for the coeval uplifting and fault-controlled subsidence in the study area.