Miocene diatoms of the upper part of the Arakawa Group distributed in the Karasuyama area, Tochigi Prefecture, central Japan (part 2): Paleobathymetric change.

Abstract

Paleobathymetric change is reconstructed for the upper Miocene sequence of the upper Arakawa Group distributed in eastern Tochigi Prefecture, central Japan, based on quantitative diatom analysis combined with analyses of benthic foraminifers and molluscs. The upper Arakawa Group constitutes a single sedimentary cycle with a upward bathymetric transition from outer sublittoral through middle bathyal to outer sublittoral environment. The middle part of the sequence represents an middle bathyal environment and includes three maximum flooding surfaces. Of the three, the first maximum flooding surface is the largest slightly above the base of the Tanokura Formation, where diatom bathymetric indices show a maximum value.