- The Calymmian Period (from Ancient Greek: κάλυμμα, romanized: kálymma, meaning “cover”) is the first geologic period in the Mesoproterozoic Era and lasted from 1600 Mya to 1400 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.
- Neoarchean (Wikipedia)
The Neoarchean (/ˌniːoʊ.ɑːrˈkiːən/ NEE-oh-ar-KEE-ən; also spelled Neoarchaean) is the last geologic era in the Archean Eon that spans from 2800 to 2500 million years ago—the period being defined chronometrically and not referencing a specific level in a rock section on Earth. The era is marked by major developments in complex life and continental formation.