This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Numerous geologic time scales, both published and unpublished, are currently in use.
None is considered the official or standard time scale.
This report presents, in tabular format, a compilation of the age estimates assigned to the major time boundaries by several commonly used or readily available time scales. It is not an exhaustive collection and is provided solely as a means of comparison. Some time scales may be more suited to a particular time period than others.