Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS19] Paleoclimatology and paleoceanography

Wed. May 29, 2019 10:45 AM - 12:15 PM 304 (3F)

convener:Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Michinobu Kuwae(Center for Marine Environmental Studies), Hitoshi Hasegawa(Faculty of Science and Technology, Kochi University), Chairperson:Yusuke Okazaki

11:45 AM - 12:00 PM

[MIS19-05] Paleoclimate reconstruction using fossil pollen analyses from a sedimentary sequence around the Matuyama-Brunhes polarity transition in the Chiba composite section

*Makoto Okada1, Hitomi Takizawa1, Yuki Haneda2, Yusuke Suganuma3,4, Quentin Simon5 (1.Department of Earth Sciences, College of Science, Ibaraki University, 2.Graduate school of Science and Technology, Ibaraki University, 3.National Institute of Polar Research, 4.Graduate University for Advanced Studies, 5.Aix-Marseille University)

Keywords:Chiba Composite Section, fossil pollen analysis, Matuyama-Brunhes reversal

To examine the “Svensmark effect”, linking climate cooling and geomagnetic field strength decrease, during the time of geomagnetic reversal, we have conducted a pollen analysis in the Chiba Composite Section including the Matuyama-Brunhes polarity reversal boundary, and correlated the quantitative paleoclimatic variation deduced by the modern analog method with the paleomagnetic and 10Be records.
The samples used in this study are from 33 horizons in a stratigraphic interval between 4-31 m above the Byk-E tephra bed where the sample density of pollen fossil data used in the previous study (Suganuma et al., 2018) is low. Samples were subjected to KOH-acetolysis treatment (Moore et al., 1991) and hydrofluoric acid treatment as pretreatment to extract pollen fossils. As a result of microscopic examination with an optical microscope, we identified 27 genera in total of 3 families, 24 genera of woody pollen, 2 genus pollen grasses and 2 spores. The abundant pollen fossils are Pinus, and some other genera distributed in the subarctic to cool temperate zones such as Picea, Tsuga, Fagus, etc.
Applying the modern analog method (Nakagawa et al., 2002) to the pollen assemblage data, the reconstructed paleoclimatic parameters show lower overall temperatures than the current study area. Comparing various climatic parameters from the modern analog method with the oxygen isotope records, insolation, 10Be showing the penetration of galactic cosmic ray into the atmosphere and relative paleointensity, the reconstructed climatic parameters showed a variation consistent with paleoceanographic temperatures deduced from oxygen isotopes of planktonic foraminifera. Moreover, we do not recognize any trend of decreasing in air temperature corresponding to geomagnetic field strength collapse at the M-B boundary as reported by Kitaba et al. (2017).