An integrated stratigraphy around the Plio-Pleistocene boundary interval in the Chikura Group, southernmost part of the Boso Peninsula, central Japan, based on data from paleomagnetic and oxygen isotopic analyses

Abstract

We propose a refined chronostratigraphy for the middle section of the Chikura Group, containing the Plio-Pleistocene boundary, from the southernmost part of the Boso Peninsula, Japan, based on magnetostratigraphy and oxygen isotopic stratigraphic analysis of benthic foraminifers. The stratigraphic interval examined here correlates with the chronostratigraphic interval from the upper Gauss chronozone, including the Kaena sub-chronozone, to the lower Matuyama chronozone. Our chronostratigraphic interpretation strongly suggests that the presently defined stratigraphic interval represents LR04 marine isotope stages (MIS) G16 to 93. The Matuyama—Gauss boundary present within the studied sequence is not within MIS 104, as is described in the LR04 time scale, but is in MIS 103. This interpretation is consistent with that of the boundary's stratigraphic horizon as reported in Mediterranean sapropel stratigraphy.