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

Abstract

The middle Pleistocene Kunosan Formation is distributed in the Udo Hills (Shizuoka, central Japan) that was tectonically uplifted about 300 m 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 +3.7 -3.6 ka (error is 1s). 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.

静岡県有度丘陵に分布する中部更新統久能山層産の単体サンゴ化石のウラン系列年代

日本語要旨

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230Th/234U法を適用し，176.5 +3.7 -3.6 ka (誤差は1s)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素同位体ステージ6.5に対応することが明らかとなった．