Chemical composition of marine surface sediments in the area offshore from northwestern Kyushu, Japan (Cruise GB23)

We determined the concentrations of 23 elements in 186 marine surface sediment samples collected in the area offshore from northwestern Kyushu, and report the chemical composition data and spatial trends.CaO is the most abundant element in the samples, with a wide concentration range of 2.63-50.2wt%.The study area is divided into three regions (the Gotonada Sea area, the area around the Hiradoshima-Genkainada Sea, and the Tsushima Strait) with distinct chemical compositions.The samples from the Gotonada Sea area have high concentrations of 18 elements and low concentrations of K2O, CaO, Rb, Sr, and Ba.The relationships among the major elements concentrations in samples from this area differ from those in samples from the other two areas.These results suggest that the Gotonada Sea samples received a large contribution of mafic clastic material.The concentrations of K2O, Rb, and Ba in the samples from the Hiradoshima-Genkainada Sea are higher than those in samples from the other two areas, indicating that some of the Genkainada Sea samples contain terrigenous particles.Samples from the Tsushima Strait have high concentrations of CaO and Sr, and differ from river sediments in Tsushima due to the dilution effect of the CaO component of biogenic debris particles (carbonate minerals).A comparison of the elemental compositions of river and marine sediments in the coastal zone suggests a low rate of sediment discharge from the present-day terrestrial environment to the marine environment.