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 6 timescales which overlap this one. show

• Obsolete Names for ICS Units
• Ten Million Year Bins
• Devonian Subages
• Devonian of Germany
• Devonian of Czechoslovakia
• Devonian of Eastern North America

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 57 collections