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# Geologic Timescale

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     MYA3 Epoch       | Period4 and 5                          | Era           | Eon           |
     0 - - - - - - + -| - - - - - - - - - - - - - - - - - - -|- - - - - - - -|- - - - - - - -|
     | Holocene       |              Quaternary              | Cenozoic      | Phanerozoic   |
     | Pleistocene    |                                      |               |               |
     1.5              | - - + - - -| - - + - - - - - - - - - |               |               |
     | Pliocene       | Neogene    | Tertiary                |               |               |
     | Miocene        |            |                         |               |               |
     23               | - - + - - -|                         |               |               |
     | Oligocene      |            |                         |               |               |
     | Eocene         | Palaeogene |                         |               |               |
     | Paleocene      |            |                         |               |               |
     64.3* - - - - + -| - - - - - -|- - - - - - - - - - - - -|- - - - - - - -|               |
     |                  Cretaceous                           |  Mesozoic     |               |
     |                                                       |               |               |
     |                                                       |               |               |
     146 - - - - - - - - - - - - - - - - - - - - - - - - - - |               |               |
     |                  Jurassic                             |               |               |
     |                                                       |               |               |
     208 - - - - - - - - - - - - - - - - - - - - - - - - - - |               |               |
     |                  Triassic                             |               |               |
     251.1*- - - - - - - - - - - - - - - - - - - - - - - - - |- - - - - - - -|               |
     |                  Permian                              |  Palaeozoic   |               |
     286 - - - + - - - - - - - - - - - - - - - - - - - - - - |               |               |
     |                  Pennsylvanian      | Carboniferous1  |               |               |
     325 - - - - - - - - - - - - - - - - - |                 |               |               |
     |                  Mississippian      |                 |               |               |
     360 - - - + - - - - - - - - - - - - - |                 |               |               |
     |                  Devonian                             |               |               |
     408.5*- - - - - - - - - - - - - - - - - - - - - - - - - |               |               |
     |                  Silurian                             |               |               |
     443.5*- - - - - - - - - - - - - - - - - - - - - - - - - |               |               |
     |                  Ordovician                           |               |               |
     |                                                       |               |               |
     490*- - - - - - - - - - - - - - - - - - - - - - - - - - |               |               |
     |                  Cambrian                             |               |               |
     545*- - - - - - - - - - - - - - - - - - - - - - - - - - |- - - - - - - -|- - - - - - - -|
     |                  Neoproterozoic2                      | Proterozoic   | Precambrian   |
     900 - - - - - - - - - - - - - - - - - - - - - - - - - - |               |               |
     |                  Mesoproterozoic                      |               |               |
     1600 - - - - - - - - - - - - - - - - - - - - - - - - - -|               |               |
     |                  Palaeoproterozoic                    |               |               |
     2500- - - - - - - - - - - -+- - - - - - - - - - - - - - |               |               |
     |                  Archaean                             |               |               |
     3800- - - - - - - - - - - - - - - - - - - - - - - - - - |               |               |
     |                  Hadean                               |               |               |
     :                                                       :               :               :

1) In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods

2) Discoveries in the past quarter century have substantially changed the view of geologic and paleontologic events immediately prior to the Cambrian. The nomenclature has not stabilized the term Neoproterozoic? is used here, but other writers might equally well have used one or more of the terms 'Ediacarian', 'Vendian', 'Varangian', 'Precambrian', 'Protocambrian', 'Eocambrian', or might have extended the Cambrian further back in time. All of these terms are usually treated as a subset of the Proterozoic? rather than a period between the Paleozoic? and the Proterozoic?.

3) Dates are slightly uncertain with differences of a few percent between various sources being common. This is largely due to uncertainties in radiodating? and the problem that deposits suitable for radiodating? seldom occur exactly at the places in the geologic column where we would most like to have them. Dates with an * are radiometrically determined based on internationally agreed to GSSPs.

4) Paleontologists often refer to faunal stages rather than geologic Periods. The Stage Nomenclature is quite complex. See http://flatpebble.nceas.ucsb.edu/public/harland.html for an excellent time ordered list of faunal stages. Also see the artile on GSSPs.

5) 'Both the lowest level subdivision -- e.g. Cambrian, Pliocene and the Next higher subdivision e.g. Tertiary -- are called 'Periods' in the current articles. I doubt very much that it is correct although I've never worried much about what the correct nouns are. Anyway, it probably needs to be fixed.'

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Last edited August 16, 2001 2:42 pm (diff)
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