|Time span formality||Formal|
|Lower boundary definition||Defined chronometrically|
|Lower GSSA ratified||1991|
|Upper boundary definition||Defined chronometrically|
|Upper GSSA ratified||1991|
The Calymmian Period (from
Mya to 1400 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.
The period is characterised by expansion of existing
platform covers, or by new platforms on recently cratonized basements.
The supercontinent Columbia started to break during the Calymmian some 1500 Mya.
- Boring Billion – Earth history, 1.8 to 0.8 billion years ago
- Jotnian – Oldest known sediments in the Baltic area that have not been subject to metamorphism
- "Calymmian Period". GeoWhen Database. Archived from the original on May 12, 2006. Retrieved January 5, 2006.
- James G. Ogg (2004). "Status on Divisions of the International Geologic Time Scale". Lethaia. 37 (2): 183–199.