Calymmian

The Calymmian (from Greek calymma, "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.

The period is characterised by expansion of existing platform covers, or by new platforms on recently cratonized basements.

The supercontinent Columbia broke up during the Calymmian some 1500 Mya.

References

• "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. doi:10.1080/00241160410006492. 

Preceded by Archean Eon	2.5 Ga - Proterozoic Eon - 542 Ma										Followed by Phanerozoic Eon
	2.5 Ga - Paleoproterozoic Era -1.6 Ga				1.6 Ga - Mesoproterozoic Era -1.0 Ga			1.0 Ga - Neoproterozoic Era -542 Ma
	Siderian	Rhyacian	Orosirian	Statherian	Calymmian	Ectasian	Stenian	Tonian	Cryogenian	Ediacaran