[M-IS14] Paleoclimatology and paleoceanography

[MIS14-P12] Oxygen isotope-magnetostratigraphy combined with beryllium isotope data during the early Pleistocene super interglacial period from the Otadai Formation, central Japan

★Invited Papers

*Yuki Haneda¹, Riku Nakagawa^2,3, Hiroto Kajita², Masayuki Utsunomiya¹, Yusuke Suganuma⁴, Motohiro Hirabayashi⁴, Hiroyuki Matsuzaki⁵, Takeyasu Yamagata⁵, Daisuke Kuwano⁶, Yoshimi Kubota⁷, Makoto Okada⁸ (1.Geological Survey of Japan, AIST, 2.Hirosaki University, 3.Shizuoka Prefectural Government, 4.National Institute of Polar Research, 5.The University Museum, The University of Tokyo, 6.Kyoto University, 7.National Museum of Nature and Science, 8.Ibaraki University)

Keywords:super interglacial, benthic foraminifera, geomagnetic field, chronostratigraphy, Calabrian

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.