Formation and Preservation of Microbial Palisade Fabric in Silica Deposits from El Tatio, Chile

Type Article
Date 2020-04
Language English
Author(s) Gong Jian1, 5, Myers Kimberly D.1, Munoz-Saez Carolina2, Homann MartinORCID3, 6, Rouillard Joti1, Wirth Richard4, Schreiber Anja4, Van Zuilen Mark A.1
Affiliation(s) 1 : Univ Paris, CNRS, Inst Phys Globe Paris, Equipe Geomicrobiol, Paris, France.
2 : Univ Chile, CEGA, FCFM, Dept Geol, Santiago, Chile.
3 : European Inst Marine Studies, CNRS, Lab Geosci, UMR6538, Technopole Brest Iroise, Plouzane, France.
4 : GeoForschungsZentrum, Sect Interface Geochem 3 5, D-14473 Potsdam, Germany.
5 : MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA.
6 : UCL, Dept Earth Sci, London, England.
Source Astrobiology (1531-1074) (Mary Ann Liebert, Inc), 2020-04 , Vol. 20 , N. 4 , P. 500-524
DOI 10.1089/ast.2019.2025
WOS© Times Cited 22
Keyword(s) Silica sinter, Biosignature, El Tatio, Sheathed cyanobacteria, Experimental diagenesis, Mars

Palisade fabric is a ubiquitous texture of silica sinter found in low temperature (<40 degrees C) regimes of hot spring environments, and it is formed when populations of filamentous microorganisms act as templates for silica polymerization. Although it is known that postdepositional processes such as biological degradation and dewatering can strongly affect preservation of these fabrics, the impact of extreme aridity has so far not been studied in detail. Here, we report a detailed analysis of recently silicified palisade fabrics from a geyser in El Tatio, Chile, tracing the progressive degradation of microorganisms within the silica matrix. This is complemented by heating experiments of natural sinter samples to assess the role of diagenesis. Sheathed cyanobacteria, identified as Leptolyngbya sp., were found to be incorporated into silica sinter by irregular cycles of wetting, evaporation, and mineral precipitation. Transmission electron microscopy analyses revealed that nanometer-sized silica particles are filling the pore space within individual cyanobacterial sheaths, giving rise to their structural rigidity to sustain a palisade fabric framework. Diagenesis experiments further show that the sheaths of the filaments are preferentially preserved relative to the trichomes, and that the amount of water present within the sinter is an important factor for overall preservation during burial. This study confirms that palisade fabrics are efficiently generated in a highly evaporative geothermal field, and that these biosignatures can be most effectively preserved under dry diagenetic conditions.

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Supplementary Data S1 1 32 KB Open access
Supplementary Data S2-S3 1 32 KB Open access
Supplementary Figure S1 1 694 KB Open access
Supplementary Figure S2 1 248 KB Open access
Supplementary Figure S3 1 303 KB Open access
Supplementary Figure S4 1 901 KB Open access
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Gong Jian, Myers Kimberly D., Munoz-Saez Carolina, Homann Martin, Rouillard Joti, Wirth Richard, Schreiber Anja, Van Zuilen Mark A. (2020). Formation and Preservation of Microbial Palisade Fabric in Silica Deposits from El Tatio, Chile. Astrobiology, 20(4), 500-524. Publisher's official version : , Open Access version :