researchers

“The chert exhibits micron-scale alternating layers of carbonaceous and siliceous materials. δ13C isotope data of carbonaceous matter (CM), together with stratigraphic relationships, indicate a biogenic origin of the kerogen, marking this, to our knowledge, as the oldest directly dated rock with a confirmed biosignature.”

researchers · said date not stated · reported 2026-08-18

The researchers describe alternating layers and isotope data indicating a biogenic origin of kerogen in the chert.