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A geologic time scale (GTS2004) is presented that integrates currently available stratigraphic and geochronologic information. Key features of the new scale are outlined, how it was constructed, and how it can be improved. Major impetus to the new scale was provided through:
(a) advances in stratigraphic standardization and refinement of the International Chronostratigraphic Scale;
(b) enhanced methods of extracting linear time from the rock record, leading to numerous high-resolution ages;
(c) progress with the use of global geochemical variations, Milankovitch climate cycles, and magnetic reversals as important stratigraphic calibration tools;
(d) improved statistical techniques for extrapolating ages and associated uncertainties to the relative stratigraphic scale, using high-resolution biozonations, including composite standards, that scale stages.
CONSTRUCTION OF GTS2004
The components of GTS2004
The Geologic Time Scale 2004 (GTS2004) project, that commenced in 1998, has compiled integrated scales of selected components of Earth history including:
Formal international subdivisions of the “rock-time” chronostratigraphic scale as ratified, or being considered, by the International Commission on Stratigraphy (ICS). The brief historical review of these subdivisions shows the progress toward the goal of a full international standard for chronostratigraphy. Due to space limitations, correlations of selected regional stratigraphic scales to the international standard are only included for some periods. The choice was ours.