People

Yusuke Kuwahara(D3)

Research Interest

I have been researching the geochemical cycles of elements during Cenozoic environmental changes (especially, glacial-interglacial cycles, and Eocene hyperthermals). In my Ph.D. study, I am focusing on the chemical weathering of silicate minerals, which has been playing an important role in controlling atmospheric pCO2. I am trying to elucidate whether and how silicate weathering contributes to the recovery from the extreme global warming events in the early Paleogene through the isotopic analyses (mainly, osmium isotopes) of marine sediments.

I am also trying to reconstruct the ancient marine environment from the chemical composition of iron- and manganese-rich sediments (umber) deposited during the Mesozoic or Paleozoic. 

In the future, I would like to try to decode the Earth's environment in the Precambrian era. My goal is to elucidate the mechanisms of environmental change in the 4.6 billion years of Earth history and to understand the coevolution of life and the Earth.


Lab experiences

  • Major and trace element analyses by operating X-ray fluorescence (XRF) and ICP-QMS.
  • Re-Os isotope analyses by operating multi-collector ICP-MS (MC-ICP-MS)
  • Stable isotope analyses (d13C, d18O)
  • Mineralogical analyses by X-ray diffraction (XRD)


Research Gate

Yusuke Kuwahara (researchgate.net)



Research Publications

  1. Kuwahara, Y., Fujinaga, K., Nozaki, T., Ohta, J., Yano, M., Yasukawa, K., Nakamura, K., Kato, Y., 2022. Iron deposition during recovery from Late Devonian oceanic anoxia: Implications of the geochemistry of the Kawame ferromanganese deposit, Nedamo Belt, Northeast Japan. Global and Planetary Change 216, 103920. https://doi.org/10.1016/j.gloplacha.2022.103920
  2. Kuwahara, Y., Yasukawa, K., Fujinaga, K., Nozaki, T., Ohta, J., Sato, H., Kimura, J.-I., Nakamura, K., Yokoyama, Y., Kato, Y., 2021. Rapid coupling between solid earth and ice volume during the Quaternary. Scientific Reports 11, 5695.  https://doi.org/10.1038/s41598-021-84448-7
  3. Fujinaga, K., Nakamura, K., Ohta, J., Yano, M.,  Kuwahara, Y., Yasukawa, K., Takaya, Y., Nakayama, K., Nozaki, T., Kato, Y., 2021. Umber as a lithified REY-rich mud in Japanese accretionary complexes and its implications for the osmium isotopic composition of Middle Cretaceous seawater, Ore Geology Reviews 142(3-4),104683. https://doi.org/10.1016/j.oregeorev.2021.104683.


Conference Presentations

  1. Kuwahara, Y., Yasukawa, K., Ohta, J., Yano, M., Mimura K., Tanaka E., Fujinaga, K., Nakamura, K., Kato, Y. The Paleogene Seawater Os Isotope Record of the Indian Ocean: Implications for the chemical weathering feedback against Eocene Hyperthermal Events. 12th In­ter­na­tional Con­fer­ence on Cli­matic and Bi­otic Events of the Pa­leo­gene (CBEP12), A-108 (Poster), Bremen, Germany, Aug. 25, 2022.
  2. Kuwahara, Y., Yasukawa, K., Ohta, J., Yano, M., Mimura, K., Tanaka, E., Fujinaga, K., Nakamura, K., Kato, Y. The Paleogene seawater osmium isotope record reconstructed from carbonate sediments in the Indian Ocean: Implications for the chemical weathering feedback against the Eocene hyperthermals. Japan Geoscience Union Meeting 2022, MIS18-22, Makuhari, Chiba, Japan, May 2022.
  3. Ikegami, K., Yasukawa, K., Tanaka, E., Ohta, J., Kuwahara, Y., Yano, M., Fujinaga, K., Nakamura, K., Kato, Y. Chemical weathering and volcanism during the early Paleogene hothouse constrained from the marine osmium isotope record in the central North Pacific Ocean. Japan Geoscience Union Meeting 2022, MIS18-21, Makuhari, Chiba, Japan, May 2022.
  4. Kuwahara, Y. Geochemistry of the ODP Site 762C core from the Indian Ocean: Implications for the Eocene Hyperthermals. JURC-DES Annual meeting, O-08, Kochi, Japan, February 2022.
  5. Kuwahara, Y., Yasukawa, K., Fujinaga, K., Nozaki, T., Ohta, J., Sato, H., Kimura, J.-I., Nakamura, K., Yokoyama, Y., Kato, Y., Fluctuation of Marine Osmium Isotope Ratio during the Quaternary Climate Cycles. Goldschmidt 2021 Virtual,  July 6, 2021. https://doi.org/10.7185/gold2021.5491.
  6. Kuwahara, Y., Fujinaga, K., Nozaki, T., Ohta, J., Yasukawa, K., Nakamura, K., Kato, Y. Geochemistry of the Kawame ferromanganese deposit in the Hayachine Belt: Implications for the oceanic environment in the Late Devonian. Japan Geoscience Union Meeting 2021, BCG04-03, online conference, June 2021.
  7. Ikegami, K., Yasukawa, K., Tanaka, E., Ohta, J., Kuwahara, Y., Yano, M., Fujinaga, K., Kato, Y. Chemical weathering feedback during the early Paleogene hyperthermals based on osmium isotope analysis. Japan Geoscience Union Meeting 2021, MIS16-P23, online conference, June 2021.
  8. Oda, Y., Ohta, J., Tanaka, E., Yasukawa, K., Kuwahara, Y., Yano, M., Fujinaga, K., Nakamura, K., Kato, Y. Depositional ages of multiple REY peaks in deep-sea sediments around Minamitorishima Island based on osmium isotope stratigraphy. Japan Geoscience Union Meeting 2021, MIS28-05, online conference, June 2021.
  9. Kuwahara, Y., Ishida, M., Kobayashi, M., Ohnuma, K., Kato, Y. Re-discovering the Lake Towada area as a geological heritage: A key to the revitalization of the local community. Japan Geoscience Union Meeting 2020, MIS21-P07, online conference, July 2020.
  10. Kuwahara, Y., Yasukawa, K., Fujinaga, K., Nozaki, T., Ohta, J., Sato, H., Kimura, J.-I., Nakamura, K., Kato, Y. Feedback responses of solid earth to the Quaternary glacial-interglacial climate cycles: A constraint from the osmium isotopic mass-balance in the ocean. The 126th Annual Meeting of the Geological Society of Japan, R22-O-8, Yamaguchi, Japan. September 2019. (in Japanese) https://doi.org/10.14863/geosocabst.2019.0_287
  11. Kuwahara, Y., Yasukawa, K., Fujinaga, K., Nozaki, T., Ohta, J., Sato, H., Kimura, J.-I., Nakamura, K., Kato, Y. Os isotope record of the Quaternary seawater derived from pelagic sediment in the Lau Basin, western South Pacific Ocean, and its implications for global climate changes. Japan Geoscience Union Meeting 2019, MIS19-21, Makuhari, Chiba, Japan, May 2019.



Awards

  1. Outstanding Student Presentation Award, Japan Geoscience Union Meeting 2022, Japan Geoscience Union. May 2022.
  2. Student Presentation Award, JURC-DES Annual meeting. March 2022.
  3. Tamaki Award of Faculty of Engineering, the University of Tokyo. March 2020. (Academic Excellence)
  4. Dean Award of Faculty of Engineering, the University of Tokyo. March 2018. (Academic Excellence) 
  5. 7th International Earth Science Olympiad (Mysore, India), Silver Medal.



Project/grant

  • April 2020 to March 2023: Research Fellowship for Young Scientists, funded by Japan Society for the Promotion of Science (JSPS). “Elucidation of the causal relationship between Paleogene environmental changes and the concentration of elements based on multi-element isotope ratios”



Others

  • April 2019 to March 2023: World-leading Innovative Graduate Study Program innovations for Future Society, the University of Tokyo
  • The Field Study Program (フィールドスタディ型政策協働プログラム), The University of Tokyo
  • Curator license
  • The Bioclassification Test (Animal Section) 2nd Grade, Japan Wildlife Research Center  
  • The Japan Kanji Aptitude Test Grade 2, Japan Kanji Aptitude Testing Foundation 



Hobbies

I have been collecting fossils and minerals since I was a child (about 3 years old). I often go out to excavate and collect fossils and minerals on my days off. I also collect old coins, ancient earthenware, and stone tools. Recently, I have started to collect insects (especially Carabidae).

In addition, I sometimes enjoy beachcombing, collecting mollusc shells and ceramic shards (especially fragments of celadon made in the Southern Song Dynasty). I have also been studying and collecting lichens since I was in elementary school.

I also enjoy traveling and have visited many places in Japan and abroad. I also enjoy visiting museums and art galleries, both in the natural history and humanities fields, and I always try to stop by a museum when I travel.