Japan Geoscience Union Meeting 2016

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS17] Paleoclimatology and paleoceanography

Tue. May 24, 2016 3:30 PM - 5:00 PM A04 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Minoru Ikehara(Center for Advanced Marine Core Research, Kochi University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University), Ikuko Kitaba(Research Centre for Palaleoclimatology, Ritsumeikan University), Akihisa Kitamura(Institute of Geosciences, Faculty of Science, Shizuoka University), Masaki Sano(Research Institute for Humanity and Nature), Ryuji Tada(Department of Earth and Planetary Science, Graduate School of Science, The Univeristy of Tokyo), Takeshi Nakagawa(Ritsumeikan University), Akira Hayashida(Department of Environmental Systems Science, Doshisha University), Chair:Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University)

3:30 PM - 3:45 PM

[MIS17-31] “Diatomaceous ocean weathering”: a new concept to understand the paleoceanic environment

*Tasuku Akagi1 (1.Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University)

Keywords:diatoms, weathering, Nd isotope ratio

“Diatomaceous ocean weathering” is a novel physiological action of diatoms, where diatoms disintegrate silicate minerals and incorporate metals in the minerals into their frustules.

The action was inferred in discussing the rare earth element (REE) composition of siliceous matter in diatom-rich settling particles in the Bering Sea. Since then, we have foraged pieces of evidence for the radical action of diatoms. The evidence includes: 1) a fully-consistent picture of the oceanic REE cycling, 2) a balance in REE budget in a water column identified using Nd isotope ratios, 3) evenly-distributed SEM images of Al in diatom frustules, 4) presence of authigenic Al, which is spectroscopically different from that in clay minerals, and 5) numerous earlier analytical studies reporting failure to separate elements in clay and those in diatom frustules.

In this paper, how the new knowledge on the diatomaceous action will affect the interpretation of the distribution of Nd isotope ratios. An example to apply the action to Nd isotope variation recorded in ferromanganese crusts will be presented. It will be shown that quite distinct, but surprisingly reasonable changes in the paleoceanic environment (pCO2 and Si concentration) will be emerged from the discussion.