Era· The columns of time
Mesozoic
252 Ma → 66 Ma
A hundred and eighty-six million years between two catastrophes: the only era on the chart that both begins and ends with a mass extinction.
What the evidence shows
It begins in the wreckage of the end-Permian event and ends at 66 million years, when an asteroid struck what is now Yucatán. The Chicxulub impact is among the best-documented events in deep time: the crater, the worldwide ejecta layer, the iridium anomaly and the extinction all agree. Between those two disasters, dinosaurs dominate the land for a hundred and thirty million years, more than four hundred times as long as our own species has existed.
Bounds and conventions
Both of its bounds are dated more tightly than most on the chart, because each falls on an event that left its trace across the whole planet at once. What the era is popularly known for, the reign of the dinosaurs, is a fair description of the land and a poor one of the sea.
Sources
- Cohen, K. M., Finney, S. C., Gibbard, P. L., Fan, J.-X. (2013). The ICS International Chronostratigraphic Chart. Episodes 36(3), 199–204, mise à jour continue, voir Cohen et al. (2025), Episodes.
- Shen et al. (2011), Science · Calibrating the end-Permian mass extinction
- Schulte et al. (2010), Science · The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary