Geochemistry and provenances of core sediments from the Shikoku Basin

Abstract

Provenances of pelagic sediments are a less well‐known and key problem of sedimentation in the deep sea. Two sediment cores from the south and middle Shikoku Basin are selected for grain size analysis and element geochemical analysis in this paper. Grain size analysis for the studied cores shows that the grain sizes become coarser upwards gradually, especially for subsurface sediments. It probably reveals the enhancement of terrigenous clastic material. Rare elements analysis reveals that two cores are enriched in Ba and Th. However, the other elements are more or less the same as those of the North American Shales (NAS). Through the NASC‐normalized REE distribution, curves are nearly aclinic, and there are no Ce and Eu anomalies. The geochemical characteristics of elements indicate that the sediments in the Shikoku Basin should mainly be regarded as hemipelagic and pelagic sediments. The comparison of samples from the Nankai Trough, Kyushu Ridge and Izu Island Arc and the analysis of DSDP and ODP cores jointly show that the sediments of the core SG1‐2 have an apparent ‘affinity’ with the Nankai Trough. The core SG1‐1 is influenced by the submarine volcanic activities, having a relatively complex provenance, and is possibly derived from the spreading centre of the Kyushu Ridge and the central Shikoku Basin. Copyright © 2016 John Wiley & Sons, Ltd.