Editing Geologic time scale (section)

==== Shields et al. 2021 ====
The ICS Subcommission for Cryogenian Stratigraphy has outlined a template to improve the pre-Cryogenian geologic time scale based on the rock record to bring it in line with the post-Tonian geologic time scale.<ref name="Shields_2022_pre-Cryogenian" /> This work assessed the geologic history of the currently defined eons and eras of the Precambrian,{{Efn|name=Precam|group=note}} and the proposals in the "Geological Time Scale" books ''2004,''<ref name="GTS2004_Precambrian">{{Citation |last=Bleeker |first=W. |title=Toward a "natural" Precambrian time scale |date=2005-03-17 |url=https://www.cambridge.org/core/product/identifier/CBO9780511536045A067/type/book_part |work=A Geologic Time Scale 2004 |pages=141–146 |editor-last=Gradstein |editor-first=Felix M. |edition=1 |publisher=Cambridge University Press |doi=10.1017/cbo9780511536045.011 |isbn=978-0-521-78673-7 |access-date=2022-04-09 |editor2-last=Ogg |editor2-first=James G. |editor3-last=Smith |editor3-first=Alan G.}}</ref> ''2012,''<ref name="GTS2012_Precambrian" /> and ''2020.''<ref name="GTS2020_Precambrian">{{Citation |last1=Strachan |first1=R. |title=Precambrian (4.56–1 Ga) |date=2020 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780128243602000164 |work=Geologic Time Scale 2020 |pages=481–493 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-824360-2.00016-4 |isbn=978-0-12-824360-2 |access-date=2022-04-09 |last2=Murphy |first2=J.B. |last3=Darling |first3=J. |last4=Storey |first4=C. |last5=Shields |first5=G.|s2cid=229513433 }}</ref> Their recommend revisions<ref name="Shields_2022_pre-Cryogenian" /> of the pre-Cryogenian geologic time scale were as below (changes from the current scale [v2023/09] are italicised). This suggestion was unanimously rejected by the International Subcommission for Precambrian Stratigraphy, based on scientific weaknesses.
* Three divisions of the Archean instead of four by dropping Eoarchean, and revisions to their geochronometric definition, along with the repositioning of the Siderian into the latest Neoarchean, and a potential Kratian division in the Neoarchean.
** Archean (4000–''2450'' Ma)
*** Paleoarchean (4000–''3500'' Ma)
*** Mesoarchean (''3500–3000'' Ma)
*** Neoarchean (''3000–2450'' Ma)
**** ''Kratian'' (no fixed time given, prior to the Siderian) – from Greek κράτος (''krátos'') 'strength'.
**** Siderian (?–''2450'' Ma) – moved from Proterozoic to end of Archean, no start time given, base of Paleoproterozoic defines the end of the Siderian
* Refinement of geochronometric divisions of the Proterozoic, Paleoproterozoic, repositioning of the Statherian into the Mesoproterozoic, new Skourian period/system in the Paleoproterozoic, new Kleisian or Syndian period/system in the Neoproterozoic.
** Paleoproterozoic (''2450–1800'' Ma)
*** ''Skourian'' (''2450''–2300 Ma) – from Greek σκουριά (''skouriá'') 'rust'.
*** Rhyacian (2300–2050 Ma)
*** Orosirian (2050–1800 Ma)
** Mesoproterozoic (''1800''–1000 Ma)
*** ''Statherian'' (1800–1600 Ma)
*** Calymmian (1600–1400 Ma)
*** Ectasian (1400–1200 Ma)
*** Stenian (1200–1000 Ma)
** Neoproterozoic (1000–538.8 Ma){{Efn|Geochronometric date for the Ediacaran has been adjusted to reflect ICC v2023/09 as the formal definition for the base of the Cambrian has not changed.|name=EdiacaranDate|group=note}}
*** ''Kleisian'' or ''Syndian'' (''1000–800'' Ma) – respectively from Greek κλείσιμο (''kleísimo'') 'closure' and σύνδεση (''sýndesi'') 'connection'.
*** Tonian (''800''–720 Ma)
*** Cryogenian (720–635 Ma)
*** Ediacaran (635–538.8 Ma)
Proposed pre-Cambrian timeline (Shield et al. 2021, ICS working group on pre-Cryogenian chronostratigraphy), shown to scale:{{Efn|Kratian time span is not given in the article. It lies within the Neoarchean, and prior to the Siderian. The position shown here is an arbitrary division.|name=kratian|group=note}}
<timeline>
ImageSize = width:1300 height:100
PlotArea = left:80 right:20 bottom:20 top:5
AlignBars = justify
Colors =
  id:proterozoic value:rgb(0.968,0.207,0.388)
  id:neoproterozoic value:rgb(0.996,0.701,0.258)
  id:ediacaran value:rgb(0.996,0.85,0.415)
  id:cryogenian value:rgb(0.996,0.8,0.36)
  id:tonian value:rgb(0.996,0.75,0.305)
  id:kleisian value:rgb(0.996,0.773,0.431)
  id:mesoproterozoic value:rgb(0.996,0.705,0.384)
  id:stenian value:rgb(0.996,0.85,0.604)
  id:ectasian value:rgb(0.996,0.8,0.541)
  id:calymmian value:rgb(0.996,0.75,0.478)
  id:paleoproterozoic value:rgb(0.968,0.263,0.44)
  id:skourian value:rgb(0.949,0.439,0.545)
  id:statherian value:rgb(0.968,0.459,0.655)
  id:orosirian value:rgb(0.968,0.408,0.596)
  id:rhyacian value:rgb(0.968,0.357,0.537)
  id:archean value:rgb(0.996,0.157,0.498)
  id:neoarchean value:rgb(0.976,0.608,0.757)
  id:mesoarchean value:rgb(0.968,0.408,0.662)
  id:paleoarchean value:rgb(0.96,0.266,0.624)
  id:hadean value:rgb(0.717,0,0.494)
  id:black value:black
  id:white value:white
Period = from:-4600 till:-538.8
TimeAxis = orientation:horizontal
ScaleMajor = unit:year increment:500 start:-4500
ScaleMinor = unit:year increment:100 start:-4500
PlotData = 
 align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5)
  bar:Eonothem/Eon
    from: -2450 till: -538.8 text:Proterozoic color:proterozoic
    from: -4000 till: -2450 text:Archean color:archean
    from: start till: -4000 text:Hadean color:hadean
  bar:Erathem/Era
    from: -1000 till: -538.8 text:Neoproterozoic color:neoproterozoic
    from: -1800 till: -1000 text:Mesoproterozoic color:mesoproterozoic
    from: -2450 till: -1800 text:Paleoproterozoic color:paleoproterozoic
    from: -3000 till: -2450 text:Neoarchean color:neoarchean
    from: -3300 till: -3000 text:Mesoarchean color:mesoarchean
    from: -4000 till: -3300 text:Paleoarchean color:paleoarchean
    from: start till: -4000 color:white
  bar:System/Period fontsize:7
    from: -635 till: -538.8 text:Ed. color:ediacaran
    from: -720 till: -635 text:Cr. color:cryogenian
    from: -800 till: -720 text:Tonian color:tonian
    from: -1000 till: -800 text:?kleisian color:kleisian
    from: -1200 till: -1000 text:Stenian color:stenian
    from: -1400 till: -1200 text:Ectasian color:ectasian
    from: -1600 till: -1400 text:Calymmian color:calymmian
    from: -1800 till: -1600 text:Statherian color:statherian
    from: -2050 till: -1800 text:Orosirian color:orosirian
    from: -2300 till: -2050 text:Rhyacian color:rhyacian
    from: -2450 till: -2300 text:?Skourian color:skourian
    from: -2700 till: -2450 text:Siderian color:neoarchean
    from: -3000 till: -2700 text:?Kratian color:neoarchean
    from: start till: -3000 color:white
</timeline>

ICC pre-Cambrian timeline (v2024/12, current {{As of|2025|01|lc=y}}), shown to scale:
<timeline>
ImageSize = width:1300 height:100
PlotArea = left:80 right:20 bottom:20 top:5
AlignBars = justify
Colors =
  id:proterozoic value:rgb(0.968,0.207,0.388)
  id:neoproterozoic value:rgb(0.996,0.701,0.258)
  id:ediacaran value:rgb(0.996,0.85,0.415)
  id:cryogenian value:rgb(0.996,0.8,0.36)
  id:tonian value:rgb(0.996,0.75,0.305)
  id:mesoproterozoic value:rgb(0.996,0.705,0.384)
  id:stenian value:rgb(0.996,0.85,0.604)
  id:ectasian value:rgb(0.996,0.8,0.541)
  id:calymmian value:rgb(0.996,0.75,0.478)
  id:paleoproterozoic value:rgb(0.968,0.263,0.44)
  id:statherian value:rgb(0.968,0.459,0.655)
  id:orosirian value:rgb(0.968,0.408,0.596)
  id:rhyacian value:rgb(0.968,0.357,0.537)
  id:siderian value:rgb(0.968,0.306,0.478)
  id:archean value:rgb(0.996,0.157,0.498)
  id:neoarchean value:rgb(0.976,0.608,0.757)
  id:mesoarchean value:rgb(0.968,0.408,0.662)
  id:paleoarchean value:rgb(0.96,0.266,0.624)
  id:eoarchean value:rgb(0.902,0.114,0.549)
  id:hadean value:rgb(0.717,0,0.494)
  id:black value:black
  id:white value:white
Period = from:-4567 till:-538.8
TimeAxis = orientation:horizontal
ScaleMajor = unit:year increment:500 start:-4500
ScaleMinor = unit:year increment:100 start:-4500
PlotData = 
 align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5)
    bar:Eonothem/Eon
    from: -2500 till: -538.8 text:Proterozoic color:proterozoic
    from: -4031 till: -2500 text:Archean color:archean
    from: start till: -4031 text:Hadean color:hadean
  bar:Erathem/Era
    from: -1000 till: -538.8 text:Neoproterozoic color:neoproterozoic
    from: -1600 till: -1000 text:Mesoproterozoic color:mesoproterozoic
    from: -2500 till: -1600 text:Paleoproterozoic color:paleoproterozoic
    from: -2800 till: -2500 text:Neoarchean color:neoarchean
    from: -3200 till: -2800 text:Mesoarchean color:mesoarchean
    from: -3600 till: -3200 text:Paleoarchean color:paleoarchean
    from: -4031 till: -3600 text:Eoarchean color:eoarchean
    from: start till: -4031 color:white
  bar:Sytem/Period fontsize:7
    from: -635 till: -538.8 text:Ed. color:ediacaran
    from: -720 till: -635 text:Cr. color:cryogenian
    from: -1000 till: -720 text:Tonian color:tonian
    from: -1200 till: -1000 text:Stenian color:stenian
    from: -1400 till: -1200 text:Ectasian color:ectasian
    from: -1600 till: -1400 text:Calymmian color:calymmian
    from: -1800 till: -1600 text:Statherian color:statherian
    from: -2050 till: -1800 text:Orosirian color:orosirian
    from: -2300 till: -2050 text:Rhyacian color:rhyacian
    from: -2500 till: -2300 text:Siderian color:siderian
    from: start till: -2500 color:white
</timeline>