Layered rock in India shows potential signs of microbial life dating to 3.5 billion years ago
A team of researchers reports that they may have found rock containing some of the earliest forms of microbial life on Earth. Their study, published in the Proceedings of the National Academy of Sciences, describes the biosignatures found in this 3.5-billion-year-old, carbon-rich, layered rock, called chert.
Researchers have discovered what may be some of the earliest evidence of microbial life on Earth, dating back 3.5 billion years ago. This finding was made in a 3.5-billion-year-old, carbon-rich rock called chert in the Singhbhum Craton in eastern India. Chert is a type of sedimentary rock that forms from the accumulation of silica and carbonaceous material, which in this case appeared to resemble the remains of a microbial mat.
The team of scientists, whose study was published in the Proceedings of the National Academy of Sciences, used uranium-lead dating to determine the age of zircon crystals found within the chert. The results confirmed that the rock was around 3.497 billion years old, suggesting that sediment deposition occurred at this time. They also examined the carbon isotope ratios and used Raman spectroscopy to analyze the carbon content.
The ratio of carbon isotopes was consistent with biological materials, and the poorly ordered kerogen indicated that the carbon likely originated from ancient, biological processes.
The researchers concluded that the chert exhibits alternating layers of carbonaceous and siliceous materials, with the carbonaceous matter showing a biogenic origin. This finding marks this chert as the oldest directly dated rock with a confirmed biosignature. However, further research is needed to confirm these results and validate the depositional age and biological interpretation.
Independent studies will also assess the zircon crystals' accuracy in dating the chert's deposition and evaluate the biological implications of this discovery.
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