Ontake-Katamachi tephra: Marine-terrestrial correlation of a time marker of marine isotopic stage 5b in NE Japan, the Japan Sea, and the NW Pacific

Abstract

We characterized Ontake volcano-derived tephras on the basis of their shard major- and trace-element compositions to distinguish between tephras by different multiple large eruptions of Ontake volcano during marine isotopic stage (MIS) 5. Then we reconsidered the ages of the tephras and their correlations between proximal and distal areas in light of their stratigraphic relationships with other widespread tephras and the δ18O stratigraphy of deep-sea sediments of the Pacific Ocean. As a result, we were able to discriminate Ontake-Katamachi tephra (On-Kt), a previously identified Ontake volcano-derived tephra in deep-sea sediments of Holes C9001C and ODP1150A off NE Japan, from other tephras in the proximal area. In addition, we suggest that previous studies may have miscorrelated On-Kt in terrestrial sequences at some locations in NE Japan to proximal Ontake-Pumice 1 (On-Pm1). Therefore, On-Kt is recognized here for the first time as a widespread tephra covering NE Japan and parts of the Japan Sea and the Pacific Ocean. The On-Kt horizon in Pacific Ocean deep-sea sediments corresponds to MIS 5b in the reported δ18O stratigraphy, and it occurs below Aso-4 (ca. 87 ka), a widespread tephra derived from Aso caldera in the Kyushu arc. As a widespread tephra covering a wider area than previously thought, On-Kt is expected to be useful for constraining the ages of regional tephras in central Japan, NE Japan, the Japan Sea, and the NW Pacific.