The Calymmian Period (from Greek κάλυμμα (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. 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. See also
Boring Billion Jotnian
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
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Siderian Rhyacian Orosirian Statherian
Calymmian Ectasian Stenian
Tonian Cryogenian Ediacaran
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