New Geology Science published online ahead of print
Geological Society of America
image: Fluid inclusions in halite. view more
Credit: Courtesy Sara Schreder-Gomes.
Boulder, Colo., USA: Primary fluid inclusions in bedded halite from the 830-million-year-old Browne Formation of central Australia contain organic solids and liquids, as documented with transmitted light and UV-vis petrography. These objects are consistent in size, shape, and fluorescent response to cells of prokaryotes and algae, and aggregates of organic compounds. This discovery shows that microorganisms from saline depositional environments can remain well preserved in halite over hundreds of millions of years and can be detected in situ with optical methods alone. This study has implications for the search for life in both terrestrial and extraterrestrial chemical sedimentary rocks.
As halite crystals grow in saline surface waters, it traps parent water in primary fluid inclusions. In addition to trapping parent waters, they can trap any solids that were in the water near/on the crystal face. These solids include tiny crystals of evaporite minerals or organics. Previous studies of modern to Permian halites have documented the presence of prokaryotic and eukaryotic organisms and organic compounds including beta carotene.
This study uses non-destructive, optical techniques to identify and document organic material in primary fluid inclusions in 830-million-year-old halite. Sara Schreder-Gomes, Kathleen Benison, and Jeremiah Bernau had access to core samples from the Neoproterozoic Browne Formation thanks to the Geological Survey of Western Australia.
The halite was well preserved and allowed them to examine halite crystals from 10 halite beds from varying depths. They used transmitted light petrography and UV-visible light petrography to identify primary fluid inclusions and their contents. The team found that solids trapped in fluid inclusions were consistent with prokaryotic and eukaryotic cells, and with organic compounds, based on their size, shape, and fluorescent response to UV-visible light.
This study reinforces the utility of non-destructive optical methods as a first step in examining chemical sediments for biosignatures. The petrographic context of fluid inclusions is vital to ensuring the contents of fluid inclusions represent original parent waters and therefore are the same age as the halite. This study also shows that microorganisms can be preserved in fluid inclusions in halite for millions of years and suggests that similar biosignatures may be able to be detected in chemical sediments from Mars.
830-million-year-old microorganisms in primary fluid inclusions in halite
Sara Schreder-Gomes; Kathleen Benison; Jeremiah Bernau
Contact: Sara Schreder-Gomes, sara.schreder-gomes@snc.edu, West Virginia University, Geology and Geography, Morgantown, West Virginia
https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G49957.1/613521/830-million-year-old-microorganisms-in-primary
GEOLOGY articles are online at https://geology.geoscienceworld.org/content/early/recent . Representatives of the media may obtain complimentary articles by contacting Kea Giles at the e-mail address above. Please discuss articles of interest with the authors before publishing stories on their work, and please make reference to GEOLOGY in articles published. Non-media requests for articles may be directed to GSA Sales and Service, gsaservice@geosociety.org.
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Geology
10.1130/G49957.1
830-million-year-old microorganisms in primary fluid inclusions in halite
6-May-2022
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Geological Society of America
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Sara Schreder-Gomes
West Virginia University
sara.schreder-gomes@snc.edu
Geological Society of America
Copyright © 2022 by the American Association for the Advancement of Science (AAAS)
Copyright © 2022 by the American Association for the Advancement of Science (AAAS)
