Biosignatures & Paleobiology

New Method For Studying Early Life In Ancient Rocks

By Keith Cowing
Press Release
University of Alberta
July 17, 2019
Filed under
New Method For Studying Early Life In Ancient Rocks
Biogenetic fabrics in the mat-related structures. The MRS textures are shown through SEM images. a Tufted microbial fabrics developed above the poorly-sorted quartz sandstone. Yellow and blue arrows point to tufts and quartz grains, respectively. b A void-filling titanium oxides that may have filled an oxygen bubble produced within the microbial mat. c Nearly-circular void filled with titanium oxides at the tip of a cone-like feature (green arrows) Detrital dioctahedral micas (e.g., muscovite) are shown by purple arrows
University of Alberta

Scientists have developed a new method for detecting traces of primordial life in ancient rock formations using potassium.

The method relies on searching for high concentrations of potassium in ancient sedimentary rocks, rather than traditional methods that look for carbon, sulfur, or nitrogen–which can appear in ancient rocks through processes unrelated to ancient life.

“Our findings show that microbial biofilms trapped potassium from ancient seawater and facilitated its accumulation into clay minerals that were buried on the seafloor,” explainedKurt Konhauser, professor in the University of Alberta’s Department of Earth and Atmospheric Sciences and co-author on the study. “This is critical because there is no abiotic mechanism that can be used to explain the potassium enrichment aside from life itself.”

The study examined clay particles from the Francevillian Formation located in Gabon, on the west coast of central Africa. This 2.1 billion-year-old formation hosts well-preserved microfossils in clay.

2.1 billion year old sediment from Gabon with ancient microbial mat features and biologically-induced potassium enrichment.

“In our quest to find evidence of early life on Earth, we have been limited to looking for a number of signatures that have all proven ambiguous, because, unfortunately, the signatures can be explained by both bacterial and abiotic processes,” explained Konhauser. “Our results indicate that a different signature–potassium–is potentially a more unique tracer, as it could only have been created through the metabolism of living bacteria.”

The research was led by Jérémie Aubineau and Abder El Albani from the University of Poitiers, France. The paper, “Microbially induced potassium enrichment in Paleoproterozoic shales and implications for reverse weathering on early Earth,” was published in Nature Communications (doi: 10.1038/s41467-019-10620-3).

Microbially induced potassium enrichment in Paleoproterozoic shales and implications for reverse weathering on early Earth, Nature Communications

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