Abstract
The purpose of this study is to examine how basin floor sedimentation responds to coastal environmental changes with relative sea-level changes. We investigated the turbidite frequency and composition of sedimentary organic matter (kerogen) in the basin floor sediments in the Kumano Trough deposited during the end of Last Glacial Maximum to post glacial ages. Composition of sedimentary organic matter changed from those rich in pollen, spores and herbaceous organic matter to those poor in these materials during the rapid transgressive stage (about 7,800 cal. yr. BP) in the submarine-fan sediments. Most of pollen, spores and herbaceous organic matter were trapped and deposited in the estuary mouth and thus the compositional changes of organic matter indicate that the bay (Ise Bay) had not been present in the upstream parts of the Kumano Trough before 7,800 cal. yr. BP. Turbidites were also deposited during the slowly transgressive stage (before 9,300 cal. yr. BP) in the submarine fan. During the slowly transgressive stage, fluvial sediments were deposited in the coastal area. The frequency of turbidity currents decreases with development of the bay (Ise Bay) during the rapid transgressive stage. The changes of sedimentary organic matter composition and turbidite frequency in the proximal environment of basin-floor fan followed by that in the distal environment. The study of turbidite frequency and organic matter composition revealed that the coastal environmental changes with relative sea-level rise affect the basin floor sedimentation.
