The BGS Geological Timechart provides colourful reference material, for use in schools, colleges and the home, setting out the geological timescale and geochronological terms we use at the British Geological Survey.
Several geological timescales exist, reflecting the use of differing datasets and methods of interpretation.
The BGS Geological Timechart is based on the timescale of Gradstein and Ogg (1996) for the Phanerozoic and that of Cowie and Bassett (1989) for the Proterozoic (Precambrian).
Subdivision of the Archaean follows an unpublished decision by the Precambrian Subcommission of the IUGS.
The result is a composite geological timechart that will be updated as improved timescales become available.
The principal chart shows the Phanerozoic (Cambrian to Quaternary) timescale. The names of the individual periods are links: each one leads to a more detailed chart showing the epochs and ages for that period.
The charts for the individual periods are all drawn to the same scale.
Where there is insufficient or contradictory data on the dating of age boundaries, the ages are given an average duration within the limits of the appropriate epoch boundaries.
These age boundaries appear as dotted lines on the charts. Generally there is one period per chart except for the Palaeogene/Neogene/Quaternary, Permian/Triassic and Ordovician/Silurian.
A chart for the Archaean and Proterozoic (Precambrian) is also included.
Cowie, J.W. & Bassett, M.G. 1989. International Union of Geological Sciences 1989 Global Stratigraphic Chart. Episodes 12, (2), Suppl.
Gradstein, F. M. and Ogg, J. 1996. A Phanerozoic time scale. Episodes, 19:3-5, plus fold-out chart.