Deep-sea sedimentation controlled by sea-level rise during the last deglaciation, an example from the Kumano Trough, Japan

Abstract

An approach combining interpretation of seismic reflection data with analysis of core lithology, especially analysis of the depositional ages of turbidites, showed that depositional patterns in the deep-sea basin of the eastern Kumano Trough, which is a forearc basin along an active convergent plate margin, were different during sea-level lowstand, slow transgressive, rapid transgressive, and highstand stages. During the lowstand and early transgressive stages, turbidites were deposited on the deep-sea basin floor where they formed a submarine fan composed of terrigenous sediments supplied by rivers via a submarine canyon. Subsequent coastline retreat and bay development during the rapid transgression stage caused a decrease in the amount of coarse-grained terrigenous sediments reaching the basin floor. However, turbidites were still deposited within the submarine canyon during the rapid transgressive and highstand stages. These deposits contain shelf sediments that have been reworked by tidal currents and storms, and sediments from slope failures caused by submarine earthquakes, but they do not contain the terrigenous sediments that are characteristic of the turbidites of the lowstand and slow transgression stages.