Japan Geoscience Union Meeting 2016

Presentation information

International Session (Poster)

Symbol B (Biogeosciences) » B-CG Complex & General

[B-CG04] Earth and Planetary Science Frontiers for Life and Global Environment

Sun. May 22, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Yohey Suzuki(Graduate School of Science, The University of Tokyo), Yoshinori Takano(Japan Agency for Marine-Earth Science and Technology (JAMSTEC)), Shingo Kato(Japan Agency for Marine-Earth Science and Technology), Katsunori Yanagawa(Graduate School of Social and Cultural Studies, Kyushu University), Tadashi Yokoyama(Department of Earth and Space Science, Graduate School of Science, Osaka University)

5:15 PM - 6:30 PM

[BCG04-P01] Transition of microbial communities and laminated structures in travertines: a case study in northern Sumatra, Indonesia

Chiya Sugihara1, *Akihiro Kano1, Katsunori Yanagawa1, Tomoyo Okumura2, Chizuru Takashima3 (1.Graduate School of Social and Cultural Studies, Kyushu University, 2.JAMSTEC, 3.Saga University)

Keywords:travertine, sulfur bacteria, stromatolite

Travertines, carbonate developed in calcareous and high pCO2 hot spring. Because these often exhibit laminated structures similar with stromatolites that had been extensively developed in ocean in Archean and Proterozoic. Previous researches of the modern analogs of the ancient stromatolites have indicated that cyanobacteria played a central role to form the laminated structure in previous studies. However, this may contradict to very low oxygen concentration in Archean. To solve this paradox, we researched a travertine-bearing hot spring at Dolok Tinggi Raja in northern Sumatra, Indonesia. Here, the water of 62 degrees, high in H2S and CO2 discharged from the vent formed a travertine mound of ~50 m wide as a consequence of geochemical and microbial processed. The water rapidly degassed H2S and CO2 immediately after discharge, increased dissolved oxygen concentration and pH and CaCO3 saturation index, and precipitated carbonate mineral (aragonite and calcite) along the flow passages. Responding to the change in the watery chemistry from upstream to downstream, the dominant microbes changed in order: chemical synthesis bacteria, purple sulfur bacteria, green non-sulfur bacteria, green sulfur bacteria. Although cyanobacteria were recognized in the downstream sites, they were subordinate. In the environment of high H2S, anoxygenic photosynthesis (sulfur bacteria) can be more profitable than oxygenic photosynthesis (cyanobacteria), and takes first priority. In the places where microbial mat is developed, the travertines often form laminated structure. The travertines with sulfur bacterial mat appear the structures that resemble the daily lamination reported from Nagayu hot spring in Oita Prefecture and Pancuran Pitu in Java. Anoxygenic sulfur bacteria have a potential to form the stromatolitic lamination, and therefore, ancient stromatolites were not necessarily made by cyanobacteria.