Cretaceous and Cenozoic Epochs

An 'epoch' is a 'third-order units' of the geologic time scale, equivalent to a 'stage' in the chronological time scale. The names of each 'epoch' and 'stage' are the same, except that within 'epochs' divisions can be termed 'Early' 'Middle' and 'Late' whereas within stages the equivalent divisions are 'Upper', 'Middle' and Lower'.
Hence the
'Lower Campanian Stage of the Upper Cretaceous System' of the chronological time scale is the
'Early Campanian Epoch of Late Cretaceous Period' of the geological time scale.

The Epochs of each Period have been defined and standardised, although there are some minor differences between the European and American names.

(The dates given below ought to show variance ('degree of certainty') and the figures for these (and other details) can all be seen in the complete chart which is given at International Stratigraphic Chart. The minor maths inconsistencies also reflect this possibility of error as well as 'rounding'.)

Cretaceous Epochs

Cenozoic Epochs

Whilst the Cenozoic era is subdivided into Tertiary and Quaternary sub-eras (or Periods), it is more formally subdivided into 7 epochs(or stages). The names of these epochs are from Greek roots, and are as follows:

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Each epoch is further sub-divided into ages, the "fourth-order units of geological time". These however, are not discussed further.
Within this discussion of Portsdown geology, the divisions are now that of 'formations', which are themselves further subdivided into 'members'. These are lithostratigraphic divisions, which are dependent solely on the rock strata and not (by definition) related in any way to age. (Ages have been applied to each formation; but the scale is no longer the geologic, or chronostratigraphic, scales discussed thus far, but a scale that does not involve age.)

To read more about the Chalk formations seen in Portsdown, please go on to Chalk Formations.

For any comments, suggestions or contributions, please e-mail me at: portsdown@bbm.me.uk