Paleoglobe NO 1590 mya-vector-colors.svg
Paleoglobe of the Earth at the start of Calymmian
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Chronological unitPeriod
Stratigraphic unitSystem
Time span formalityFormal
Lower boundary definitionDefined chronometrically
Lower GSSA ratified1991
Upper boundary definitionDefined chronometrically
Upper GSSA ratified1991

The Calymmian Period (from Ancient Greek: κάλυμμα, romanizedkálymma, 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 started to break during the Calymmian some 1500 Mya.

See also

  • 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

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