JpGU-AGU Joint Meeting 2020

Presentation information

[J] Poster

O (Public ) » Public

[O-04] Poster presentations by senior high school students

convener:Tatsuhiko Hara(International Institute of Seismology and Earthquake Engineering, Building Research Institute), Katsuyoshi Michibayashi(Department of Earth and Planetary Sciences, Nagoya University), Miwa Kuri(Japan Meteorological Agency), Keiko Konya(Japan Agency for Marine-Earth Science and Technology)

[O04-P60] Fine laminated structure of stromatolite suggests summer and winter in cretaceous period?

*Taiga Tsujimoto1 (1.Saitama prefectural Kasukabe High School)

Keywords:stromatolite, cyanobacteria

I studied formation processes of fine laminated structures of three types with different lithology stromatolites in the El Morino formation (latter term of cretaceous period) in the Andes, Bolivia in South America. According to observation of thin sections, fine laminated structures consist of the thin layers of light layers and dark layers less than 2mm thickness, made from calcium carbonate(CaCO3). Light layers and dark layers are acknowledged the differences of variation width of layer thickness and particle sizes and shapes of CaCO3. Especially, difference in size of thickness is remarkable. That`s because there is a difference in crystallization amount of CaCO3 with variation of carbon dioxide concentration in sea water. And I considered variation of carbon dioxide concentration by relating the amount of photosynthesis of cyanobacteria and carbon dioxide solubility. As a result, I concluded that fine laminated structures are corresponded seasonal seasonal changes.