Transport process of sand grains from fluvial to deep marine regions estimated by luminescence of feldspar: example from theKumano area, centralJapan

Abstract

AbstractUsing the concept of bleaching in optical dating, a new index of sediment sample bleaching percentage (BLP‐2) was developed and applied to evaluate sand grain transport from riverine to deep‐marine environments. As bleached grains in modern sediments have no optically stimulated luminescence (OSL)/infrared stimulated luminescence (IRSL) signal, bleached and unbleached feldspar grains are distinguished byIRSLintensity. TheBLP‐2 distribution of present deposits around theKumano area, on thePacific coast of centralJapan, suggests that sand grains in surface turbidites obtained from the bottom of theKumanoTrough are of flood/storm origin rather than seismogenic origin. The distribution ofBLP‐2 tentatively suggests sand grain erosion–transport–depositional processes; for example, origin and transport agencies of shelf sand, and influence of coastal erosion on the beach deposit. Although the presentBLPanalysis is not yet supported by a rigorous statistical test, it is useful to distinguish recent deposition and remobilization of sand grains. Furthermore, if the depositional age and the luminescence age of sand grains are accurately estimated, sand grain transport processes of old (lateQuaternary) sediments may be estimated by the methodology similar to that of the present study.