The interval definitions in this timescale are derived from the following source:

• W. B. Harland, R. L. Armstrong, A. V. Cox, L. E. Craig, A. G. Smith and D. G. Smith. 1990. A Geologic Time Scale 1989. view

There are 12 timescales which overlap this one. show

• Obsolete Names for ICS Units
• Ten Million Year Bins
• Cambrian Epochs
• Ordovician of Britain
• Ordovician of the Baltic
• Ordovician of North America
• Cambrian of China
• Cambrian of Australia
• Cambrian of Siberia
• Cambrian of Kazakhstan
• Cambrian of North America
• Cambrian of West Avalonia

Interval boundaries marked with * have been interpolated based on the differences between the ages for international timescale boundaries quoted in the source and the currently accepted ages for those boundaries.

This timescale is used in the definition of 602 collections