Editing Archean Eon (section)

=== Carbon Isotopes (Carbon-12 and Carbon-13) ===

* The ratio of carbon-13 (¹³C) to carbon-12 (¹²C) in carbonaceous deposits (like kerogen, carbonate rocks, and fossilized plant material) can shed light on the presence of biological activity. Photosynthetic organisms preferentially incorporate the lighter ¹²C isotope, leading to an enrichment of ¹³C in the residual environment. Significant deviations from the expected natural abundances of these isotopes can indicate biological processes. Biologic material will often have a composition that is enriched in lighter isotopes compared to the surrounding rock it's found in.
* Changes in the carbon isotope ratios over time can provide insights into the composition of the Earth's atmosphere, including fluctuations in CO₂ levels and the presence of methane-producing organisms.