Sediment provenance of the Gunsan Basin and its relationship to regional tectonics in the Yellow Sea

Structural and stratigraphic history of Gunsan Basin in the Yellow Sea has long intrigued geologists. However, detrital provenance and changes relevant to the basin evolution have not been thoroughly investigated. This study investigated the sediment composition of the Gunsan Basin through petrographic observations and X-ray diffraction analysis of drill cuttings from five exploratory wells. The petrography and mineralogy of the sediments from each drilled well showed compositional heterogeneity in the lowermost seismic unit (SU-1), whereas the upper seismic units (SU-2 and SU-3) showed remarkable similarities. These findings reveal that the source areas underwent a significant change in association with regional tectonic events, marked by a basin-wide unconformity between SU-1 and SU-2. During the initial stage of basin subsidence, from the Cretaceous to the Eocene, sediments were derived locally from adjacent uplifts and volcanic terrenes, resulting in spatially heterogeneous sediment composition. After a major tectonic inversion and subsequent subsidence since the Early Miocene, the sediments appeared to have been derived from a single yet extensive highland, most likely the Sulu Orogenic Belt. These findings provide fundamental information on sediment composition and provenance and offer insights into the relationship between sediment characteristics and basin configuration driven by regional tectonics.