[S-GL39] 上総層群における下部ー中部更新統境界GSSP

[SGL39-03] 千葉セクション、大阪湾、北大西洋に共通する軌道スケール、千年スケールの古海洋変動

*兵頭 政幸¹、北場 育子²、加藤 茂弘³、林 広樹⁴、北村 晃寿⁵、岡田 誠⁶ (1.神戸大学　内海域環境教育研究センター、2.立命館大学　古気候学研究センター、3.兵庫県立人と自然の博物館自然・環境評価研究部、4.島根大学総合理工学部、5.静岡大学理学部地球科学教室、6.茨城大学理学部理学科)

キーワード：千葉セクション、マツヤマ－ブリュンヌ境界、大阪湾、北大西洋、海水準変動

Chemical and magnetic data of a 54-m long core drilled near the Chiba section, Tabuchi provide excellent proxies of sea-level variations. The Ca/Ti ratio, magnetic susceptibility, ARM, and ARM/magnetic susceptibility values measured every 1 cm interval show variations well correlated with those from the oxygen isotope data from planktonic foraminifera fossils. The existence of such correlations reflects combined effects of changes in biogenic calcium carbonate production, accumulation rate (a.r.) and grain size of clastics due to sea-level variations. The Ca/Ti curve, a best sea-level proxy, shows precession-related signals correlated with highstands 19.3 and 19.1, and lowstand 19.2. The orbitally tuned Ca/Ti curve represents a number of centennial scale features well correlated with those of sea-level proxies from Osaka Bay and North Atlantic. In consideration of a.r. variability, the age model for the Chiba section was refined with more control points between the orbital scale control points, adjusting to the astronomical time scale for the Osaka Bay core that has a uniform a.r. In the early MIS 19, the highest sea-level peak is preceded by a sea-level fall event, as in Osaka Bay. After MIS 19.2, there are many millennial scale fluctuation features, most of which are observed in the records from Osaka Bay and North Atlantic (IODP site U1313). These features are possibly global, and some of them are affected by eustatic sea-level changes. The MBB is dated at 777 ka in Osaka Bay, and 778 ka in the Chiba section and the North Atlantic.