U-Series Ages for Solitary Coral Species from the Middle Pleistocene Kunosan Formation in the Udo Hills, Shizuoka, Central Japan

摘要

The middle Pleistocene Kunosan Formation is distributed in the Udo Hills (Shizuoka, central Japan) that was tectonically uplifted about 300m during the late Quaternary. The formation consists of about 200-m-thick of coarse-grained fan-delta deposits. The thorium-230 age of a species of solitary coral from the Kunosan Formation in the eastern Udo Hills (Muramatsu Gravel-Silt Member) is 176.5_(-3.6)~(+3.7)ka (error is 1 σ). This radiometric age means that the Kunosan Formation was deposited during marine isotope stage 6.5. This interpretation is consistent with previously published chronologic information for the middle and upper Pleistocene in the Udo Hills.%静岡市，有度丘陵（最高標高307m）の東縁に分布する中部更新統久能山層（村松礫・シルト部層）から産した単体サンゴに，αスペクトル~(230)Th／~(234)U法を適用し，176.5_(-3.6)~(+3.7)ka（誤差は1σ）の年代値を得た．この年代値から，久能山層堆積期間は海洋酸薧赝惶濂攻譬`ジ6.5に対応することが明らかとなった．