Physical and geoacoustic properties of surface sediments off eastern Geoje Island, South Sea of Korea

In order to characterize and map the surface sediments of the shelf off eastern Geoje Island, the South Sea of Korea, sediment texture, physical, and geoacoustic properties were measured and calculated on eighteen core samples collected from the study area. The surface sediments are characterized by both Holocene sediments (mostly supplied from the Nakdong River) and Quaternary sediments (e.g., relict sediments, due to a rising of sea level during the Quaternary) depending on seafloor bathymetry. Based on the properties analyzed, the study area is divided into three different geoacoustic provinces: (1) Province I, affected directly by the Nakdong River discharge; (2) Province II, covered by the southern branch of the Nakdong River discharge; and (3) Province III, dominated by relict sediments. Mean grain size, velocity, and bulk density decrease from Province I (7.4ϕ, 1528 m/s, and 1.6 g/cm3, respectively) to Province II (8.1ϕ, 1485 m/s, and 1.5 g/cm3), and then increase rather rapidly in Province III (1.4ϕ, 1664 m/s, and 2.2 g/cm3). Porosity, on the other hand, exhibits an opposite trend, increasing from Province I (64.5%) to Province II (73.9%), and then decreasing significantly in Province III (32.9%).