Radiolarians from dredged sedimentary rocks from off southeast Boso Peninsula

Abstract

We report radiolarian fossils from sedimentary rocks recovered from off southeast Boso Peninsula, central Japan to determine the age of the rocks. Rock samples were collected from sites D03 and D04 on the steep slopes close to the Katsuura Submarine Canyon using a dredge during the cruise KT-12-35. The radiolarian assemblages suggested a geologic age of 8.84–7.74 Ma (middle Late Miocene) for the site D03 (southeast slope of the Awa-Bank) and two geologic ages of 4.5–4.3 Ma (middle Pliocene) and 11.8–9.0 Ma (early Late Miocene) for the site D04 (north slope from the Katsuura Submarine Canyon). These ages correspond to depositional ages of the Amatsu Formation of the Miura Group (forearc basin deposits), the Nishizaki Formation (accretionary prism) and the Minami-Boso Group (trench slope basin deposits) exposed on the Boso Peninsula.