Geologic timescale

A timeline of geologic periods in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy.

The Earth is thought by geologists to be 4.6 billion years old. The geologic or "deep" time of Earth's past has been organized into various periods according to events which took place in each period.

(not shown to scale)

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

2) The Proterozoic, Archean and Hadean are often collectively referred to as Precambrian Time, and sometimes also as the Cryptozoic.

3) Dates are slightly uncertain with differences of a few percent between various sources being common. This is largely due to uncertainties in radiometric dating and the problem that deposits suitable for radiometric dating 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. The dates quoted above are according to the International Commission on Stratigraphy 2004 time scale. All dates given are for the end of the interval in question.

4) Paleontologists often refer to faunal stages rather than geologic Periods. The Stage Nomenclature is quite complex. See Harland (http://flatpebble.nceas.ucsb.edu/cgi-bin/bridge.pl?action=startScale) for an excellent time ordered list of faunal stages. Also see the article on GSSPs.

5) In common usage the Tertiary-Quaternary and Paleogene-Neogene-Quaternary Periods are treated as equivalents to the Mesozoic and Paleozoic Periods. The term 'Period|Age' (e.g. 'Neogene Period|Age') is sometimes used instead of 'Period'.

6) The time shown in the "Years Ago" column is that of the end of the interval named beside it.

7) Hadean was sometimes called Priscoan.

8) The GSSP for the base of the Ediacaran, ratified in 2004, is a climatic/geochemical marker rather than biostratigraphic. It represents the end of a widespread glaciation event.

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 id:period value:rgb(1,0.7,0.7) # light red
 id:age    value:rgb(0.7,1,0.7) # light green
 id:era    value:rgb(1,1,0.7)   # light blue
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 id:black  value:black

Period = from:-4500 till:0 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:500 start:-4500 ScaleMinor = unit:year increment:100 start:-4500

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 bar:eon color:eon

 at:      0   align:right  $markred
 at:   -545   align:left   $markred
 from: -545   till:    0   text:Phanerozoic
 from:-2500   till: -545   text:Proterozoic
 from:-3800   till: -2500  text:Archaean
 from: start  till: -3800  text:Hadean

 bar:era color:era

 from:  -64.3 till:    0   text:C~z shift:(0,1.5)
 from: -251.1 till:  -64.3 text:Meso~zoic shift:(0,1.5)
 from: -545   till: -251.1 text:Paleo~zoic shift:(0,1.5)
 from: -900   till:  -545  text:Neoprote-~rozoic shift:(0,1.8)
 from:-1600   till:  -900  text:Mesoproterozoic
 from:-2500   till: -1600  text:Paleoproterozoic
 from:-2800   till: -2500  text:Neo-~archean shift:(0,1.5)
 from:-3200   till: -2800  text:Meso-~archean shift:(0,1.5)
 from:-3600   till: -3200  text:Paleo-~archean shift:(0,1.5)
 fontsize:7
 from:-3800   till: -3600  text:Eo-~arch-~ean shift:(0,2)
 from:start   till: -3800  

 bar:period color:period

 fontsize:6
 from:   -1.6 till:    0
 from:  -64.3 till:   -1.6
 from: -146   till:  -64.3
 from: -208   till: -146
 from: -251.1 till: -208
 from: -286   till: -251.1
 from: -360   till: -286
 from: -408.5 till: -360
 from: -443.5 till: -408.5
 from: -490   till: -443.5
 from: -545   till: -490

 from: -620   till:  -545  text:Ed. 
 from: -850   till:  -620  text:Cryo-~genian
 from: -1000  till:  -850  text:Ton-~ian
 from: -1200  till:  -1000 text:Sten-~nian
 from: -1400  till:  -1200 text:Ect-~asian
 from: -1600  till:  -1400 text:Calym-~mian
 from: -1800  till:  -1600 text:Stath-~erian
 from: -2050  till:  -1800 text:Oro-~sirian
 from: -2300  till:  -2050 text:Rhy-~acian
 from: -2500  till:  -2300 text:Sid-~erian
 from: start  till:  -2500

</timeline>

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   id:period value:rgb(1,0.7,0.7) # light red
   id:age    value:rgb(0.7,1,0.7) # light green
   id:era    value:rgb(1,1,0.7)   # light blue
   id:eon    value:rgb(1,0.7,1)   # light purple
   id:filler value:gray(0.8)      # background bar
   id:black  value:black

Period = from:-545 till:0 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:100 start:-500 ScaleMinor = unit:year increment:10 start:-540

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 bar:eon color:eon
 at:      0   align:right  $markred
 at:   -545   align:left   $markred
 from: -545   till:    0   text:Phanerozoic
 bar:era color:era
 at:      0   align:right  $markgreen
 at:    -64.3 align:left   $markgreen
 from:  -64.3 till:    0   text:Cenozoic
 from: -251.1 till:  -64.3 text:Mesozoic
 from: -545   till: -251.1 text:Paleozoic

 bar:period color:period fontsize:8
 from:   -1.6 till:    0
 from:  -64.3 till:   -1.6 text:Tertiary
 from: -146   till:  -64.3 text:Cretaceous
 from: -208   till: -146   text:Jurassic
 from: -251.1 till: -208   text:Triassic
 from: -286   till: -251.1 text:Permian
 from: -360   till: -286   text:Carboniferous
 from: -408.5 till: -360   text:Devonian
 from: -443.5 till: -408.5 text:Silurian
 from: -490   till: -443.5 text:Ordovician
 from: -545   till: -490   text:Cambrian

 bar:age color:age fontsize:6
 from: start  till:  end
 from: -23    till:  -1.6  text:Neo-~gene             shift:(0,0.5)
 from: -64.3  till: -23    text:Paleo~gene          shift:(0,0.5)
 from: -286   till: -251.1 # mark end of Paleozoic
 from: -325   till:  -286  text:Pennsyl-~vanian shift:(0,0.5)
 from: -360   till:  -325  text:Missis-~sippian shift:(0,0.5)

</timeline>

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Period = from:-65.5 till:0 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:10 start:-60 ScaleMinor = unit:year increment:1 start:-65

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 bar:era color:era
 at:     0  align:right $markgreen
 at: start  align:left  $markgreen
 from:start  till:  0    text:Cenozoic

 bar:period color:period
 from: -1.6  till:  0    text:Qua~ter~nary fontsize:6 align:left shift:(-7,5)
 from:start  till: -1.6  text:Tertiary

 bar:age color:age
 from: -1.6  till:  0
 from: -23   till:  -1.6 text:Neogene
 from:start  till: -23   text:Paleogene

 bar:epoch color:epoch
 from: -0.1  till:  0
 from: -1.6  till: -0.1  text:P
 from: -5    till: -1.6  text:Plio~cene shift:(0,1) fontsize:6
 from:-23    till: -5    text:Miocene
 from:-38    till:-23    text:Oligocene
 from:-55    till:-38    text:Eocene
 from:start  till:-55    text:Paleocene

</timeline>

See also

• Age of the Earth
• Fossils and the geological timescale
• Cosmological timeline
• Lunar geologic timescale
• Anthropocene
• Logarithmic timeline

References

• GeoWhen Database (http://www.stratigraphy.org/geowhen/)
• International Commission on Stratigraphy Time Scale (http://www.stratigraphy.org/gssp.htm)

Capitalization

When used in formal writing, specific geological and historical periods and events are capitalized. Some examples: the Silurian Period, the Ice Age, the Neolithic, the Archean; however, when not specific, some historical events remain uncapitalized, as in ice ages.

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