International Commission on Stratigraphy

A global effort to standardize international stratigraphic nomenclature is being conducted by the International Commission on Stratigraphy (ICS), the largest scientific body within the International Union of Geological Sciences (IUGS). It is also the only organization concerned with stratigraphy on a global scale. The ICS is in the process of standardizing the Geological Time Scale. A major purpose of the ICS is to establish global stage boundaries called Global Stratotype Sections and Points (GSSP's).

International Union of Geological Sciences--The IUGS is one of the largest non-governmental scientific organizations in the world. IUGS keeps a non-political and non-governmental stance and is a non-profit making organization. With 116 member countries and 38 affiliated organizations, IUGS represents about 250,000 earth scientists worldwide.

The Union's journal is Episodes (
IUGS website is ICS website is

Global Stratotype Section and Point (GSSP)--The basal boundary of each global stage in this international geologic scale is standardized at a Global Boundary Stratotype Section and Point (GSSP). A GSSP is a point in a single reference section within an interval exhibiting continuous sedimentation that was selected by international agreement as the primary reference level for the geologic stage.

Standard Geologic Time Scale--The Stratigraphic Chart provides a universal language for geo-history and includes a succession of global rock units, the stages, formed during specific intervals of geologic time. It is produced by the International Commission on Stratigraphy under IUGS and is the result of many years of work by thousands of stratigraphers all over the world in their endeavor to relate rock with time. The Geologic Time Scale 2012 by Gradstein et al. (2012) is the successor to The Geologic Time Scale 2004 by Gradstein et al. (2004). The Concise Geologic Time Scale (Ogg et al., 2008) was an update to The Geologic Time Scale 2004. Previous versions of the international chart were published by Remane (2000), Harlan et al. (1990), and Harlan et al. (1982). The current International Stratigraphic Chart is available at The Stratigraphic Chart is based on the sequence of these GSSP's. The chart is continually updated (available at


Gradstein, F. M., Ogg, J. G., Schmitz, M. D., and Ogg, G. M., eds., 2012, The geologic time scale 2012: Elsevier, 1,144 p.

Gradstein, F. M., Ogg, J. G., and Smith, A. G., 2004, A geologic time scale 2004: Cambridge University Press, 589 p.

Harlan, W. B., Armstrong, R. L., Cox, A. V., Craig, L. E., Smith, A. G., and Smith, D. G., 1990, A Geologic Time Scale 1989: Cambridge University Press, 263 p.

Harlan, W. B., Cox, A. V., Llewellyn, P. G., Pickton, C. A. G., Smith, A. G., and Walters, R., 1982, A Geologic Time Scale: Cambridge University Press, 131 p.

Ogg, J. G., Ogg, G., and Gradstein, F. M., 2008, The concise geologic time scale: Cambridge University Press, 177 p.

Remane, J., 2000, International stratigraphic chart, with explanatory note: International Union of Geological Sciences, 16 p., 1 chart.