Tectonic Evolution And Depositional Environments Of Jeju And Socotra Basins In The Southernmost Continental Shelf Of The South Sea, Korea

This study focuses on the tectonic evolution and depositional environment change of the Jeju and Socotra basins in the southernmost continental shelf of the South Sea, Korea, based on the analyses of seismic stratigraphy, geologic structures, and seismic facies on the multi-channel seismic profiles acquired by KIOST (Korea Institute of Ocean Science and Technology). The Jeju and Socotra basins commonly occur as the local basement lows surrounded by large-scale basement highs. The basin-filling sedimentary sequences are divided into 4 megasequences (MS1-MS4) by regional unconformities and their correlated conformities. The chronostratigraphy of megasequences from Eocene to Plio-Pleistocene is established based on published biostratigraphic data from the existing hydrocarbon exploration wells. Geologic structures in the Socotra Basin are characterized by rift-stage normal faults involved with basement rotation, and subsequent folds and local normal faults in Oligocene sequence interval, The Jeju Basin, by contrast, shows predominant occurrence of reverse faults and folds within Eocene to Miocene sequences. Based on the acoustic characters and reflection geometries, 6 types of seismic facies are classified, and interpreted as geologic basements (B1), volcanic-sedimentary complexes (B2), inner-shelf deposits (S1), fluvio-lacustrine deposits (S2), coastal deposits (S3), and volcanic sills or volcanic edifices (S4), respectively. By integrating all these results, we present the reconstructions of tectonic evolution and depositional environment change in Jeju and Socotra basins.