[M-IS16] 古気候・古海洋変動

[MIS16-12] Characteristic of radiocarbon dates in response to sea-level changes in the Bonaparte Gulf, Northwestern Australia

*石輪 健樹^1,2,3、横山 祐典^2,3,4、オブラクタ スティーブン⁵、上原 克人⁶、奥野 淳一^1,7、池原 実⁸、宮入 陽介² (1.国立極地研究所、2.東京大学大気海洋研究所、3.東京大学理学系研究科、4.海洋研究開発機構、5.秋田大学大学院国際資源学研究科、6. 九州大学応用力学研究所、7.総合研究大学院大学複合科学研究科、8.高知大学海洋コア総合研究センター)

キーワード：放射性炭素年代測定、海水準変動、古潮汐モデル

Radiocarbon dating is an essential method for constraining Late Quaternary age models and applied to carbon-containing materials. Past climate and sea-level changes influence depositional process so that paleoenvironmental reconstruction is needed to select an appropriate dating material. We present radiocarbon dates variation performed on macrofossils, foraminifers, and acid-insoluble carbon (AIC), as well as paleo-tidal modeling results from the Bonaparte Gulf in northwestern Australia. The varied topography and large tidal range of this gulf are the dominant factors of the past depositional process in response to sea-level change. We will reveal the variation of radiocarbon dates in response to sea-level changes, which appear as changes in paleowater depth and paleotide. Carbonate fossil material reveals a more reliable depositional age than acid insoluble carbon at sea level below -70 m because of little lateral transport caused by reduced tidal activity. On the other hand, acid insoluble carbon ages are more reliable at sea level above – 70 m because redeposition of old fossil influences carbonate fossils ages due to enhanced tidal activity. Our results indicate that the age models' reliability has changed over time, especially on the continental shelf, where environmental changes due to sea-level fluctuations are significant.