[M-IS17] 古気候・古海洋変動

[MIS17-25] 海洋酸素同位体ステージ3の海水準低下によるBonaparte湾の堆積環境変化

*石輪 健樹^1,2、横山 祐典^1,2、宮入 陽介¹、オブラクタ スティーブン³、池原 実⁴、佐々木 猛智⁵、上原 克人⁶、北村 晃寿⁷ (1.東京大学大気海洋研究所、2.東京大学理学系研究科、3.秋田大学国際資源学部、4.高知大学海洋コア総合研究センター、5.東京大学総合研究博物館、6.九州大学応用力学研究所、7.静岡大学大学院理学研究科)

キーワード：海水準変動、古環境復元、放射性炭素年代測定

During the Marine Isotope Stage 3 (MIS 3), ice volume changed in the short period and increased to the maximum volume in the Last Glacial Maximum (LGM). Accurate relative sea level records at far-field site, remote form ice-covered area, provide the ice volume information. However, the MIS 3 sea level records at far-field site are limited by the availability of dataset. The Bonaparte Gulf, northwestern Australia, is tectonically stable region and located at the far field. This Gulf has the carbonate platforms, which were exposed during the sea level lowstand. We show the paleoenvironmental change associated with sea level drop during MIS 3 using the marine sediments core from the Bonaparte Gulf. The primary information for the timing of exposure is calcium variation standardized by titanium. Total organic carbon, C/N ratios, and ¹⁴C age offset (offset between the carbonate and organic matter age) also provide the paleoenvironmental information on the exposure of carbonate platform. We concluded that sea level drop occurred at ca. 26 ka, which is consistent with previous works as Huon Peninsula records. This drop is associated with Heinrich event 2.