The Calymmian (from Greek "calymma", "cover") is the first
geologicperiod in the MesoproterozoicEra and lasted from 1600 Ma to 1400 Ma (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.
supercontinentColumbia broke up during the Calymmian some 1500 Ma.
*cite web | title=Calymmian Period | work=GeoWhen Database | url=http://www.stratigraphy.org/geowhen/stages/Calymmian.html | accessmonthday=January 5 | accessyear=2006
*cite journal | author=James G. Ogg | title=Status on Divisions of the International Geologic Time Scale. | journal=Lethaia | year=2004 | volume=37 | issue= | pages=183–199 | url=http://www.stratigraphy.org/precambrian/Ogg_2003.pdf | doi=10.1080/00241160410006492
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