Early Permian-Devonian = modified slightly from compilations in GTS04.

Main sources of stratigraphic columns The columns are a selected subset of the extensive internal data suite within TimeScale Creator (versions 1.3.5 through 1.4). The majority of these columns are also diagrammed in The Concise Geologic Time Scale (Ogg, Ogg, Gradstein, 2008) [Concise GTS08]. Numerical ages of biostratigraphic datums are consistent with Geologic Time Scale 2004 (Gradstein, Ogg, Smith, 2004) [GTS04], with the exception of some adjusted scalings within the Cambrian and Carboniferous (see The Concise Geologic Time Scale for details). Ages of chronostratigraphic stages and sequences are mainly derived from those biostratigraphic datum assignments. (1) Chronostratigraph