[M-IS14] 古気候・古海洋変動

[MIS14-P12] 上総層群大田代層の前期更新世スーパー間氷期層準における酸素同位体―古地磁気層序とベリリウム同位体記録

★招待講演

*羽田 裕貴¹、中川 陸^2,3、梶田 展人²、宇都宮 正志¹、菅沼 悠介⁴、平林 幹啓⁴、松崎 浩之⁵、山形 武靖⁵、桑野 太輔⁶、久保田 好美⁷、岡田 誠⁸ (1.産業技術総合研究所地質調査総合センター、2.弘前大学、3.静岡県庁、4.国立極地研究所、5.東京大学総合研究博物館、6.京都大学、7.国立科学博物館、8.茨城大学)

キーワード：スーパー間氷期、底生有孔虫、地球磁場、年代層序、カラブリアン期

Marine isotope stage (MIS) 31 is known as a super interglacial period during the early Pleistocene, characterized by high obliquity and eccentricity with the precession minimum, resulting in high insolation in the Northern Hemisphere and remarkable climate warming. Several paleoclimatic and paleoceanographic records have been obtained from most of the world, describing millennial-scale climate variations and the 20 m eustatic sea level rise during MIS 31 relative to modern. High temporal resolution palaeoceanographic record in the northwestern Pacific, however, still lacks, although the ocean contains one of the largest western boundary currents in the globe, the Kuroshio Current, which strongly influences the climate of the Japanese archipelago, East Asia, and the Northern Hemisphere. Additionally, the MIS 31 super interglacial contains the lower transition of the Jaramillo Normal Subchronozone (lower Jaramillo transition), and thus provides an opportunity to investigate the influence of the geomagnetic field minimum associated with the geomagnetic polarity reversal on the remarkably warm climate. The Pleistocene marine Otadai Formation of the Kazusa Group, distributed in the Boso Peninsula, central Japan, is located near the northern boundary of the Kuroshio Current, and covers the whole interval of MIS 31 with a notably high sedimentation rate. We conducted paleomagnetic, foraminiferal oxygen isotope and beryllium isotope analyses for the Otadai Formation to provide a chronological framework for future paleoceanographic studies and to constrain the stratigraphic position of the lower Jaramillo transition in the oxygen isotope stratigraphy. In this presentation, we show preliminary oxygen isotope-magnetostratigraphy and beryllium isotope data, which is a geomagnetic field intensity proxy independent of the paleomagnetic record during MIS 31.