Calymmian

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.

Calymmian
1600 – 1400 Ma Pha. Proterozoic Archean Had'n
Paleoglobe of the Earth at the start of Calymmian
Chronology
Events of the Calymmian -1600 — – -1580 — – -1560 — – -1540 — – -1520 — – -1500 — – -1480 — – -1460 — – -1440 — – -1420 — – -1400 — – P ♇ M e s o p r o t e r o z o i c Statherian Calymmian Ectasian     ← Breakup of the supercontinent Columbia Events of the Calymmian Period. Axis scale: millions of years ago.
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Period
Stratigraphic unit	System
Time span formality	Formal
Lower boundary definition	Defined chronometrically
Lower boundary GSSP	N/A
GSSP ratified	N/A
Upper boundary definition	Defined chronometrically
Upper boundary GSSP	N/A
GSSP ratified	N/A

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.