The Geological Time Scale
First published: 2013
Brief summary
ICS chart/source for geological time units and boundaries.
Article
The International Chronostratigraphic Chart organises Earth history into a hierarchy of eons, eras, periods, epochs and ages. It provides the standard names, order and numerical boundary ages used in international stratigraphy.
Chronostratigraphic units refer to bodies of rock formed during specified intervals, while corresponding geochronological units refer to the intervals of time themselves. The chart places these parallel systems together so that rock units and time units can be compared consistently.
Many boundaries are defined by Global Boundary Stratotype Sections and Points, commonly called golden spikes. These reference points are selected in accessible stratigraphic sections and are tied to distinctive fossil, geochemical, magnetic or other markers that can be correlated internationally.
The numerical ages and formal divisions are revised as evidence improves and new boundaries are ratified. The chart is therefore a maintained scientific standard rather than a fixed historical table, and users should consult the current edition for official terminology and ages.
Source details and credits
- Source / publisher: International Commission on Stratigraphy
- Source type: Reference / chart
- URL type: WWW
- Credits: International Commission on Stratigraphy
- URL: https://stratigraphy.org/chart