International Commission on Stratigraphy

node · earth · International

The body within the International Union of Geological Sciences that defines and maintains the geological time scale, publishes the International Chronostratigraphic Chart, and ratifies GSSPs proposed by its subcommissions. It is the reason deep-time dates are comparable between papers at all: without a single ratified chart, every laboratory would attach its own ages to its own boundaries. The Commission is also a useful corrective to the idea that the time scale is settled. Chart versions are reissued regularly and numerical ages change between them as new high-precision dates arrive — the base of the Cambrian appears as 541.0 ± 1.0 Ma on charts widely cited through the 2010s and as 538.8 ± 0.2 Ma on more recent ones. Nothing about the rocks changed; the measurement improved and the definition stayed where it was.