Late Quaternary tephrostratigraphy of underground sediments in the middle west part of Aizu Basin, Fukushima, northeast Japan

Abstract

Tephra layers were identified from three boring cores in Aizubange Town, middle west part of the Aizu Basin, one of the tectonic basins in the south part of Northeast Japan. Ages of seven horizons were determined by radiocarbon dating. These results clarified the tephrostrati-graphy, chronology, and accumulation rates of subsurface sediments in the study area. Sedi-ments with a depth less than ca. 100m are mainly composed of silt, peat, and sand with several intercalations of gravel beds and tephra layers. These tephra layers can be correlated with Nm-NM (5.4ka), AT (30ka), DKP (55-66ka), Nm-KN, Ag-OK (<85.1ka), TG (129ka), and Sn-MT (180-260ka). Estimated accumulation rates determined for the longest core are 0.46-0.55m/kyrs after the deposition of DKP to present, whereas they are 0.19-0.23m/kyr at the depth between the horizons of DKP and TG.