Chronology
−1600 —
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−1580 —
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−1560 —
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−1540 —
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−1520 —
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−1500 —
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−1480 —
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−1460 —
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−1440 —
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−1420 —
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−1400 —
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Breakup of the supercontinent Columbia
Etymology
Name formality
Formal
Usage information
Celestial body
Regional usage
Global (ICS)
Time scale(s) used
ICS Time Scale
Definition
Chronological unit
Stratigraphic unit
Time span formality
Formal
Lower boundary definition
Defined chronometrically
Lower GSSA ratified
1991[1]
Upper boundary definition
Defined chronometrically
Upper GSSA ratified
1991[1]
The Calymmian Period (from Ancient Greek: κάλυμμα, romanized: 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 started to break up during the Calymmian some 1500 Mya.
The Volyn biota have been dated to 1500 Mya.