JpGU-AGU Joint Meeting 2020

Presentation information

[E] Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS08] Paleoclimatology and paleoceanography

convener:Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University), Benoit Thibodeau(University of Hong Kong), Akitomo Yamamoto(Japan Agency for Marine-Earth Science and TechnologyAtmosphere and Ocean Research Institute), Hitoshi Hasegawa(Faculty of Science and Technology, Kochi University)

[MIS08-P06] Late Eocene travertine in the SE Tibet and cyclical change in its isotopic composition implying the monsoon climate

*Aki Sakuma1, Hirokazu Kato1, Yoshihiro Kakizaki1, Akihiro Kano1, Ryuji Tada2,3, Hongbo Zheng2 (1.Department of Earth and Planetary Science, School of Science, the University of Tokyo, 2.Yunnan University, 3.Chiba Institute of Technology)

Keywords:travertine, late Eocene, Asian monsoon, Jianchuan basin

The Asian monsoon is the most dominant monsoon system in the world but when and how it was established is still under the debate. Recently, its onset during the late Eocene was suggested (Licht et al., 2014) but little geological evidence in the low-latitude region hinder the reliable evaluation of the past climate pattern. In this study, we investigated the sedimentary environment of the late Eocene limestone in the Jianchuan basin by the microfacies and carbon and oxygen isotope analyses. We identified six lithofacies (laminated bindstone, oncoidal grainstone, calcareous conglomerate, wackestone, lime-mudstone, and bafflestone) and the limestone appears regular lamination and encrusted waterweed, which are unique features of travertine. The high δ13C and low δ18O values strongly support the travertine origin and disagree with the previous interpretation of lacustrine carbonate. The high δ13C values resulted from a large proportion of isotopically depleted fraction from endogenic CO2. Furthermore, high-resolution isotopic analysis for the laminated travertine confirms a seasonal pattern that is consistent with the laminated texture observed in the modern travertine. The isotopic pattern of the travertine also indicates humid summer and dry winter in the late Eocene, which are the same as the modern monsoonal climate regime.