Geologic time scale: Difference between revisions

{{Short description|System that relates geologic strata to time}}

<!--Use |group=note for {efn}}-->

[[File:GeologicTimeScale-WikiLeadImage.svg|alt=Geologic time scale with proportional representation of eons/eonothems and eras/erathems. Cenozoic is abbreviated to Cz. The image also shows some notable events in Earth's history and the general evolution of life.|thumb|Geologic time scale with proportional representation of eons/eonothems and eras/erathems. Cenozoic is abbreviated to Cz. The image also shows some notable events in Earth's history and the general evolution of life.|upright=1.35]]

The '''geologic time scale''' ('''GTS''') is a representation of [[time]] based on the [[Geologic record|rock record]] of [[Earth]]. It is a system of [[chronological dating]] that uses [[chronostratigraphy]] (the process of relating [[Stratum|strata]] to time) and [[geochronology]] (scientific branch of [[geology]] that aims to determine the age of rocks). It is used by primarily by [[Earth science|Earth scientists]] (including [[Geologist|geologists]], [[Paleontology|paleontologists]], [[Geophysics|geophysicists]], [[Geochemistry|geochemists]], and [[Paleoclimatology|paleoclimatologists]]) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as [[Lithology|lithologies]], [[Paleomagnetism|paleomagnetic]] properties, and [[Fossil|fossils]]. The definition of standardized international units of geologic time is the responsibility of the [[International Commission on Stratigraphy]] (ICS), a constituent body of the [[International Union of Geological Sciences]] (IUGS), whose primary objective<ref name="ICS_statutes">{{Cite web |title=Statutes |url=https://stratigraphy.org/statutes |access-date=2022-04-05 |website=stratigraphy.org |publisher=International Commission on Stratigraphy}}</ref> is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC)<ref name="ICC_Cohen_2013">{{Cite journal |last=Cohen |first=K.M. |last2=Finney |first2=S.C. |last3=Gibbard |first3=P.L. |last4=Fan |first4=J.-X. |date=2013-09-01 |title=The ICS International Chronostratigraphic Chart |url=http://www.episodes.org/journal/view.html?doi=10.18814/epiiugs/2013/v36i3/002 |journal=Episodes |language=en |edition=updated |volume=36 |issue=3 |pages=199–204 |doi=10.18814/epiiugs/2013/v36i3/002 |issn=0705-3797}}</ref> that are used to define divisions of geologic time. The chronostratigraphic divisions are in turn used to define geochronologic units.<ref name="ICC_Cohen_2013" />

While some regional terms are still in use,<ref name="GTS2012_Precambrian">{{Citation |last=Van Kranendonk |first=Martin J. |title=A Chronostratigraphic Division of the Precambrian |date=2012 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780444594259000160 |work=The Geologic Time Scale |pages=299–392 |publisher=Elsevier |language=en |doi=10.1016/b978-0-444-59425-9.00016-0 |isbn=978-0-444-59425-9 |access-date=2022-04-05 |last2=Altermann |first2=Wladyslaw |last3=Beard |first3=Brian L. |last4=Hoffman |first4=Paul F. |last5=Johnson |first5=Clark M. |last6=Kasting |first6=James F. |last7=Melezhik |first7=Victor A. |last8=Nutman |first8=Allen P.}}</ref> the table of geologic time presented on this page conforms to the [[nomenclature]], ages, and colour codes set forth by the ICS as this is the standard, reference global geologic time scale.<ref name="ICS_statutes" />

== Principles ==

{{See also|Age of Earth|History of Earth|Geological history of Earth}}

The geologic time scale is a way of representing [[deep time]] based on events that have occurred throughout [[History of Earth|Earth's history]], a time span of about [[Age of Earth|4.54&nbsp;±&nbsp;0.05&nbsp;Ga]] (4.54 billion years).<ref name="Dalrymple 2001 AoE">{{cite journal |last=Dalrymple |first=G. Brent |date=2001 |title=The age of the Earth in the twentieth century: a problem (mostly) solved |journal=Special Publications, Geological Society of London |volume=190 |issue=1 |pages=205–221 |bibcode=2001GSLSP.190..205D |doi=10.1144/GSL.SP.2001.190.01.14 |s2cid=130092094}}

</ref> It chronologically organizes strata, and subsequently time, by observing fundamental changes in stratigraphy that correspond to major geological or paleontological events. For example, the [[Cretaceous–Paleogene extinction event]], marks the lower boundary of the [[Paleogene]] System/Period and thus the boundary between the [[Cretaceous]] and Paleogene Systems/Periods. For divisions prior to the [[Cryogenian]], arbitrary numeric boundary definitions (GSSAs) are used to divide geologic time. Proposals have been made to better reconcile these divisions with the rock record.<ref name="Shields_2022_pre-Cryogenian">{{Cite journal |last=Shields |first=Graham A. |last2=Strachan |first2=Robin A. |last3=Porter |first3=Susannah M. |last4=Halverson |first4=Galen P. |last5=Macdonald |first5=Francis A. |last6=Plumb |first6=Kenneth A. |last7=de Alvarenga |first7=Carlos J. |last8=Banerjee |first8=Dhiraj M. |last9=Bekker |first9=Andrey |last10=Bleeker |first10=Wouter |last11=Brasier |first11=Alexander |date=2022 |title=A template for an improved rock-based subdivision of the pre-Cryogenian timescale |url=http://jgs.lyellcollection.org/lookup/doi/10.1144/jgs2020-222 |journal=Journal of the Geological Society |language=en |volume=179 |issue=1 |pages=jgs2020–222 |doi=10.1144/jgs2020-222 |issn=0016-7649}}</ref><ref name="GTS2012_Precambrian" />

Historically, regional geologic time scales were used<ref name="GTS2012_Precambrian" /> due to the litho- and biostratigraphic differences around the world in time equivalent rocks. The ICS has long worked to reconcile conflicting terminology by standardizing globally significant and identifiable stratigraphic [[Horizon (geology)|horizons]] that can be used to define the lower boundaries of chronostratigraphic units. Defining chronostratigraphic units in such a manner allows for the use of global, standardised nomenclature. The ICC represents this ongoing effort.

The relative relationships of rocks for determining the chronostratigraphic positions use the overriding principles of:

* [[Superposition principle|Superposition]] – Newer rock beds will lie on top of older rock beds unless the succession has been overturned.

* [[Principle of original horizontality|Horizontality]] – All rock layers were originally deposited horizontally.{{Efn|It is now known that not all sedimentary layers are deposited purely horizontally, but this principle is still a useful concept.|name=horizontality|group=note}}

* [[Principle of lateral continuity|Lateral continuity]] – Originally deposited layers of rock extend laterally in all directions until either thinning out or being cut off by a different rock layer.

* Biologic succession (where applicable) – This states that each stratum in a succession contains a distinctive set of fossils. This allows for correlation of stratum even when the horizon between them is not continuous.

* [[Cross-cutting relationships]] – A rock feature that cuts across another feature must be younger than the rock it cuts.

* [[Law of included fragments|Inclusion]] – Small fragments of one type of rock but embedded in a second type of rock must have formed first, and were included when the second rock was forming.

* Relationships of [[Unconformity|unconformities]] – Geologic features representing periods of erosion or non-deposition, indicating non-continuous sediment deposition.

== Terminology{{Anchor|Terminology}} ==

{{See also|Stratigraphy|Chronostratigraphy|Biostratigraphy|Magnetostratigraphy|Lithostratigraphy|Geochronology}}

The GTS is divided into chronostratigraphic units and their corresponding geochronologic units. These are represented on the ICC published by the ICS; however, regional terms are still in use in some areas.

<em>Chronostratigraphy</em> is the element of [[stratigraphy]] that deals with the relation between rock bodies and the relative measurement of geological time.<ref name="ICS_chronostrat">{{Cite web |title=Chapter 9. Chronostratigraphic Units |url=https://stratigraphy.org/guide/chron |access-date=2022-04-02 |website=stratigraphy.org |publisher=International Commission on Stratigraphy}}</ref> It is the process where distinct strata between defined stratigraphic horizons are assigned to represent a relative interval of geologic time.

A <em>chronostratigraphic unit</em>{{Anchor|Chronostratigraphic unit}} is a body of rock, layered or unlayered, that is defined between specified stratigraphic horizons which represent specified intervals of geologic time. They include all rocks representative of a specific interval of geologic time, and only this time span.<ref name="ICS_chronostrat">

Eonothem, erathem, system, series, subseries, stage, and substage are the hierarchical chronostratigraphic units.<nowiki><ref name="ICS_chronostrat"> </nowiki>

<em>Geochronology</em> is the scientific branch of geology that aims to determine the age of rocks, fossils, and sediments either through absolute (e.g., [[radiometric dating]]) or relative means (e.g., [[Law of superposition|stratigraphic position]], [[Paleomagnetism]], [[Stable isotope ratio|stable isotope ratios]]).<nowiki><ref name="ICS_definitions"></nowiki>{{Cite web |title=Chapter 3. Definitions and Procedures |url=https://stratigraphy.org/guide/defs |access-date=2022-04-02 |website=stratigraphy.org |publisher=International Commission on Stratigraphy}}</ref>

A <em>geochronologic unit</em>{{Anchor|Geochronologic unit}} is a subdivision of geologic time. It is a numeric representation of an intangible property (time).<ref name="ICS_definitions" /> Eon, era, period, epoch, subepoch, age, and subage are the hierarchical geochronologic units.<ref name="ICS_chronostrat" /> <em>[[Geochronometry]]</em> is the field of geochronology that numerically quantifies geologic time.<ref name="ICS_definitions" />

A <em>[[Global Boundary Stratotype Section and Point]]</em> (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundaries of stages on the geologic time scale.<ref name="ICS_GSSP">{{Cite web |title=Global Boundary Stratotype Section and Points |url=https://stratigraphy.org/gssps/ |access-date=2022-04-02 |website=stratigraphy.org |publisher=International Commission on Stratigraphy}}</ref> (Recently this has been used to define the base of a system)<ref name="Knoll_2006_Ediacaran">{{Cite journal |last=Knoll |first=Andrew |last2=Walter |first2=Malcolm |last3=Narbonne |first3=Guy |last4=Christie-Blick |first4=Nicholas |date=2006 |title=The Ediacaran Period: a new addition to the geologic time scale |url=http://doi.wiley.com/10.1080/00241160500409223 |journal=Lethaia |language=en |volume=39 |issue=1 |pages=13–30 |doi=10.1080/00241160500409223}}</ref>

A <em>[[Global Standard Stratigraphic Age]]</em> (GSSA)<ref name="Remane_1996_GSSP">{{Cite journal |last=Remane |first=Jürgen |last2=Bassett |first2=Michael G |last3=Cowie |first3=John W |last4=Gohrbandt |first4=Klaus H |last5=Lane |first5=H Richard |last6=Michelsen |first6=Olaf |last7=Naiwen |first7=Wang |last8=the cooperation of members of ICS |date=1996-09-01 |title=Revised guidelines for the establishment of global chronostratigraphic standards by the International Commission on Stratigraphy (ICS) |url=http://www.episodes.org/journal/view.html?doi=10.18814/epiiugs/1996/v19i3/007 |journal=Episodes |language=en |volume=19 |issue=3 |pages=77–81 |doi=10.18814/epiiugs/1996/v19i3/007 |issn=0705-3797}}</ref> is a numeric only, chronologic reference point used to define the base of geochronologic units prior to the Cryogenian. These points are arbitrarily defined.<ref name="ICS_chronostrat"> They are used where GSSPs have not yet been established. Research is ongoing to define GSSPs for the base of all units that are currently defined by GSSAs.

The numeric (geochronometric) representation of a geochronologic unit can, and is more frequently subject to, change when geochronology refines the geochronometry, while the equivalent chronostratigraphic unit remains the same, and their revision is less common. For example, in early 2022 the boundary between the [[Ediacaran]] and [[Cambrian]] [[Period (geologic time)|Periods]] (geochronologic units) was revised from 541 Ma to 538.8 Ma but the rock definition of the boundary (GSSP) at the base of the Cambrian, and thus the boundary between the Ediacaran and Cambrian [[System (stratigraphy)|Systems]] (chronostratigraphic units) has not changed, merely the geochronometry has been refined.

The numeric values on the ICC are represented by the unit [[Megaannum|Ma]] (megaannum) meaning "million [[Year|years]]", i.e., {{Period start|Jurassic}} {{Period start error|Jurassic}} Ma, the lower boundary of the [[Jurassic]] Period, is defined as 201,300,000 years old with an uncertainty of 200,000 years. Other [[Si prefix|SI prefix]] units commonly used by geologists are [[Gigaannum|Ga]] (gigaannum, billion years), and [[Kiloannums|ka]] (kiloannum, thousand years), with the latter often represented in calibrated units ([[Before Present|before present]]).

=== Divisions of geologic time {{Anchor|Divisions of geologic time}} ===

An <em>eon</em> is the largest (formal) geochonologic time unit and is the equivalent of a chronostratigraphic [[eonothem]].<nowiki><ref name="dictionary_of_geology_2020"></nowiki>{{Cite book |url=https://www.worldcat.org/oclc/1137380460 |title=A dictionary of geology and earth sciences |date=2020 |others=Michael Allaby |isbn=978-0-19-187490-1 |edition=Fifth |location=Oxford |oclc=1137380460}}</ref> {{As of|2022|April|bare=}} there are three formally defined eons/eonothems: the [[Archean]], [[Proterozoic]], and [[Phanerozoic]].<ref name="ICC_Cohen_2013" /> The [[Hadean]] is an informal eon/eonothem, but is commonly used.<ref name="dictionary_of_geology_2020" />

An <em>era</em> is the second largest geochonologic time unit and is the equivalent of a chronostratigraphic [[erathem]].<ref name="ICS_chronostrat" /><ref name="dictionary_of_geology_2020" /> {{As of|2022|April|bare=}} there are currently ten defined eras/erathems.<ref name="ICC_Cohen_2013" />

A <em>period</em> is a major rank below an <em>era</em> and above an <em>epoch</em>. It is the geochronologic equivalent of a chronostratigraphic [[System (stratigraphy)|system]].<ref name="ICS_chronostrat" /><ref name="dictionary_of_geology_2020" />{{As of|2022|April|bare=}} there are currently 22 defined periods/systems.<ref name="ICC_Cohen_2013" /> As an exception two subperiods/subsystems are used for the [[Carboniferous]] Period/System.<ref name="ICS_chronostrat" />

An <em>epoch</em> is the second smallest geochronologic unit, between a <em>period</em> and an <em>age</em>. It is the equivalent of a chronostratigraphic [[Series (stratigraphy)|series]].<ref name="ICS_chronostrat" /><ref name="dictionary_of_geology_2020" /> {{As of|2022|April|bare=}} there are currently 37 defined and one informal <em>epochs/series</em>. There are also 11 subepochs/subseries which are all within the [[Neogene]] and [[Quaternary]].<ref name="ICC_Cohen_2013" /> The use of subseries/subepochs as formal ranks/units in international chronostratigraphy was ratified in 2022.<ref name="Aubry_2022_subseries">{{Cite journal |last=Aubry |first=Marie-Pierre |last2=Piller |first2=Werner E. |last3=Gibbard |first3=Philip L. |last4=Harper |first4=David A. T. |last5=Finney |first5=Stanley C. |date=2022-03-01 |title=Ratification of subseries/subepochs as formal rank/units in international chronostratigraphy |url=http://www.episodes.org/journal/view.html?doi=10.18814/epiiugs/2021/021016 |journal=Episodes |language=en |volume=45 |issue=1 |pages=97–99 |doi=10.18814/epiiugs/2021/021016 |issn=0705-3797}}</ref>

An <em>age</em> is the smallest hierarchical geochonologic unit and is the equivalent of a chronostratigraphic [[Stage (stratigraphy)|stage]].<ref name="ICS_chronostrat" /><ref name="dictionary_of_geology_2020" /> {{As of|2022|April|bare=}} there are currently 96 formal and five informal ''ages/stages''.<ref name="ICC_Cohen_2013" />

A <em>chron</em> is a non-hierarchical formal geochronology unit of unspecified rank and is the equivalent of a chronostratigraphic [[chronozone]].<ref name="ICS_chronostrat" /> These correlate with [[Magnetostratigraphy|magnetostratigraphic]], [[Lithostratigraphy|lithostratigraphic]], or [[Biostratigraphy|biostratigraphic]] units as they are based on previously defined stratigraphic units or geologic features.

The <em>Early</em> and <em>Late</em> subdivisions are used as the geochronologic equivalents of the chronostratigraphic <em>Lower</em> and <em>Upper</em>, e.g., Early [[Triassic]] Period (geochronologic unit) is used in place of Lower Triassic Series (chronostratigraphic unit).

In essence, it is true to say that rocks representing a given chronostratigraphic unit are that chronostratigraphic unit, and the time they were laid down in is the geochronologic unit, i.e., the rocks that represent the [[Silurian]] Series ''are'' the Silurian Series and they were deposited ''during'' the Silurian Period.

{| class="wikitable mw-collapsible" style = "margin-left: auto; margin-right: auto; border: none;"

|+Formal, hierarchical units of the geologic time scale (largest to smallest)

!Chronostratigraphic unit (strata)

!Geochronologic unit (time)

!Time span{{Efn|Time spans of geologic time units vary broadly, and there is no numeric limitation on the time span they can represent. They are limited by the time span of the higher rank unit they belong to, and to the chronostratigraphic boundaries they are defined by.|group=note|name=timespan}}

|Eonothem

|Eon

|Several hundred millions of years

|Erathem

|Era

|Tens to hundreds of millions of years

|System

|Period

|Millions of years to tens of millions of years

|Series

|Epoch

|Hundreds of thousands of years to tens of millions of years

|Subseries

|Subepoch

|Thousands of years to millions of years

|Stage

|Age

|Thousands to years to millions of years

|}

== Naming of geologic time ==

The names of geologic time units are defined for chronostratigraphic units with the corresponding geochronologic unit sharing the same name with a change to the suffix (e.g. [[Phanerozoic]] Eonothem becomes the Phanerozoic Eon). Names of erathems in the Phanerozoic were chosen to reflect major changes of the history of life on Earth: [[Paleozoic]] (old life), [[Mesozoic]] (middle life), and [[Cenozoic]] (new life). Names of systems are diverse in origin, with some indicating chronologic position (e.g., Paleogene), while others are named for [[lithology]] (e.g., Cretaceous), [[geography]] (e.g., [[Permian]]), or are tribal (e.g., [[Ordovician]]) in origin. Most currently recognised series and subseries are named for their position within a system/series (early/middle/late); however, the ICS advocates for all new series and subseries to be named for a geographic feature in the vicinity of its [[stratotype]] or [[Type locality (geology)|type locality]]. The name of stages should also be derived from a geographic feature in the locality of its stratotype or type locality.<ref name="ICS_chronostrat" />

Informally, the time before the Cambrian is often referred to as the pre-Cambrian or Precambrian (Supereon).<ref name="Shields_2022_pre-Cryogenian" />{{efn|Precambrian or pre-Cambrian is an informal geological term for time before the Cambrian period|name=Precam|group=note}}

{| class="wikitable mw-collapsible" style = "margin-left: auto; margin-right: auto; border: none;"

|+Time span and [[etymology]] of eonothem/eon names

!Name

!Time Span

!Etymology of name

|[[Phanerozoic]]

|{{Period span/brief|Phanerozoic|1}}

|From the Greek words φανερός (''phanerós'') meaning 'visible' or 'abundant', and ζωή (''zoḯ'') meaning 'life'.

|[[Proterozoic]]

|{{Period span/brief|Proterozoic|1}}

|From the Greek words πρότερος (''próteros'') meaning 'former' or 'earlier', and ζωή (''zoḯ'') meaning 'life'.

|[[Archean]]

|{{Period span/brief|Archean|1}}

|From the Greek word [[Ἀρχή|αρχή]] (''arche''), meaning 'beginning, origin'.

|[[Hadean]]

|~{{Period span/brief|Hadean|1}}

|From [[Hades]], the Greek god.

|}

{| class="wikitable mw-collapsible" style = "margin-left: auto; margin-right: auto; border: none;"

|+Time span and etymology of erathem/era names

!Name

!Time Span

!Etymology of name

|[[Cenozoic]]

|{{Period span/brief|Cenozoic|1}}

|From the Greek words καινός (''kainós'') meaning 'new', and ζωή (''zoḯ'') meaning 'life'.

|[[Mesozoic]]

|{{Period span/brief|Mesozoic|1}}

|From the Greek words μέσο (''méso'') meaning 'middle', and ζωή (''zoḯ'') meaning 'life'.

|[[Paleozoic|Paleozoic]]

|{{Period span/brief|Paleozoic|1}}

|From the Greek words παλιός (''palaiós'') meaning 'old', and ζωή (''zoḯ'') meaning 'life'.

|[[Neoproterozoic]]

|{{Period span/brief|Neoproterozoic|1}}

|From the Greek words νέος (''néos'') meaning 'new' or 'young', πρότερος (''próteros'') meaning 'former' or 'earlier', and ζωή (''zoḯ'') meaning 'life'.

|[[Mesoproterozoic]]

|{{Period span/brief|Mesoproterozoic|1}}

|From the Greek words μέσο (''méso'') meaning 'middle', πρότερος (''próteros'') meaning 'former' or 'earlier', and ζωή (''zoḯ'') meaning 'life'.

|[[Paleoproterozoic]]

|{{Period span/brief|Paleoproterozoic|1}}

|From the Greek words παλιός (''palaiós'') meaning 'old', πρότερος (''próteros'') meaning 'former' or 'earlier', and ζωή (''zoḯ'') meaning 'life'.

|[[Neoarchean]]

|{{Period span/brief|Neoarchean|1}}

|From the Greek words νέος (''néos'') meaning 'new' or 'young', and ἀρχαῖος (''arkhaîos'') meaning 'ancient'.

|[[Mesoarchean]]

|{{Period span/brief|Mesoarchean|1}}

|From the Greek words μέσο (''méso'') meaning 'middle', and ἀρχαῖος (''arkhaîos'') meaning 'ancient'.

|[[Paleoarchean]]

|{{Period span/brief|Paleoarchean|1}}

|From the Greek words παλιός (''palaiós'') meaning 'old', and ἀρχαῖος (''arkhaîos'') meaning 'ancient'.

|[[Eoarchean]]

|{{Period span/brief|Eoarchean|1}}

|From the Greek words Ηώς (''Iós'') meaning 'dawn', and ἀρχαῖος (''arkhaîos'') meaning 'ancient'.

|}

{| class="wikitable mw-collapsible" style = "margin-left: auto; margin-right: auto; border: none;"

|+Time span and etymology of system/period names

!Name

!Time Span

!Etymology of name

|[[Quaternary]]

|{{Period span/brief|Quaternary|1}}

|First introduced by [[Jules Desnoyers]] in 1829 for sediments in [[France]]'s [[Seine]] Basin that appeared to be younger than [[Tertiary]]{{efn|The Tertiary is a now obsolete geologic system/period spanning from 66 Ma to 2.6 Ma. It has no exact equivalent in the modern ICC, but is approximately equivalent to the merged Palaeogene and Neogene systems/periods.|name=Tertiary|group=note}} rocks.<ref name="Desnoyers_1829">{{cite journal |last1=Desnoyers |first1=J. |title=Observations sur un ensemble de dépôts marins plus récents que les terrains tertiaires du bassin de la Seine, et constituant une formation géologique distincte; précédées d'un aperçu de la nonsimultanéité des bassins tertiares |journal=Annales des Sciences Naturelles |date=1829 |volume=16 |pages=171–214, 402–491 |url=https://www.biodiversitylibrary.org/item/29350#page/177/mode/1up |trans-title=Observations on a set of marine deposits [that are] more recent than the tertiary terrains of the Seine basin and [that] constitute a distinct geological formation; preceded by an outline of the non-simultaneity of tertiary basins |language=fr}} [https://www.biodiversitylibrary.org/item/29350#page/199/mode/1up From p. 193:] ''"Ce que je désirerais … dont il faut également les distinguer."'' (What I would desire to prove above all is that the series of tertiary deposits continued – and even began in the more recent basins – for a long time, perhaps after that of the Seine had been completely filled, and that these later formations – ''Quaternary'' (1), so to say – should not retain the name of alluvial deposits any more than the true and ancient tertiary deposits, from which they must also be distinguished.) However, on the very same page, Desnoyers abandoned the use of the term "Quaternary" because the distinction between Quaternary and Tertiary deposits wasn't clear. From p. 193: ''"La crainte de voir mal comprise … que ceux du bassin de la Seine."'' (The fear of seeing my opinion in this regard be misunderstood or exaggerated, has made me abandon the word "quaternary", which at first I had wanted to apply to all deposits more recent than those of the Seine basin.)</ref>

|[[Neogene|Neogene]]

|{{Period span/brief|Neogene|1}}

|Derived from the Greek words νέος (''néos'') meaning 'new', and γενεά (''geneá'') meaining 'genesis' or 'birth'.

|[[Paleogene]]

|{{Period span/brief|Paleogene|1}}

|Derived from the Greek words παλιός (''palaiós'') meaning 'old', and γενεά (''geneá'') meaining 'genesis' or 'birth'.

|[[Cretaceous]]

|{{Period span/brief|Cretaceous|1}}

|Derived from <em>Terrain Crétacé</em> used in 1822 by [[Jean d'Omalius d'Halloy]] in reference to extensive beds of [[chalk]] within the [[Paris Basin]].<ref name="d'Halloy 1822">{{cite journal | author = d’Halloy, d’O., J.-J. | year = 1822 | title = Observations sur un essai de carte géologique de la France, des Pays-Bas, et des contrées voisines |trans-title=Observations on a trial geological map of France, the Low Countries, and neighboring countries | journal = Annales des Mines | volume = 7 | pages = 353–376 | url = https://books.google.com/books?id=c-ocAQAAIAAJ&pg=PA353}} From page 373: "La troisième, qui correspond à ce qu'on a déja appelé formation de la craie, sera désigné par le nom de terrain crétacé." (The third, which corresponds to what was already called the "chalk formation", will be designated by the name "chalky terrain".)</ref> Ultimately derived from the [[Latin]] crēta meaning (''chalk'').

|[[Jurassic]]

|{{Period span/brief|Jurassic|1}}

|Named after the [[Jura Mountains]]. Originally used by [[Alexander von Humboldt]] as 'Jura Kalkstein' (Jura limestone) in 1799.<ref name="Humboldt_1799">{{Cite book |last=Humboldt |first=Alexander von |url=https://books.google.co.in/books?id=oZ5PAAAAcAAJ&newbks=0&hl=en&redir_esc=y |title=Ueber die unterirdischen Gasarten und die Mittel ihren Nachtheil zu vermindern: ein Beytrag zur Physik der praktischen Bergbaukunde |date=1799 |publisher=Vieweg |language=de}}</ref> [[Alexandre Brongniart]] was the first to publish the term Jurassic in 1829.<ref name="Brogniart_1829">{{Cite book |last=Brongniart |first=Alexandre (1770-1847) Auteur du texte |url=https://gallica.bnf.fr/ark:/12148/bpt6k255061 |title=Tableau des terrains qui composent l'écorce du globe ou Essai sur la structure de la partie connue de la terre . Par Alexandre Brongniart,... |date=1829 |language=fr}}</ref><ref name="GTS2012_Jurassic">{{Citation |last=Ogg |first=J.G. |title=Jurassic |date=2012 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780444594259000263 |work=The Geologic Time Scale |pages=731–791 |publisher=Elsevier |language=en |doi=10.1016/b978-0-444-59425-9.00026-3 |isbn=978-0-444-59425-9 |access-date=2022-05-01 |last2=Hinnov |first2=L.A. |last3=Huang |first3=C.}}</ref>

|[[Triassic]]

|{{Period span/brief|Triassic|1}}

|From the <em>Trias</em> of [[Friedrich August von Alberti]] in reference to a trio of formations widespread in southern [[Germany]].

|[[Permian]]

|{{Period span/brief|Permian|1}}

|Named after the historical region of [[Perm Governorate|Perm]], [[Russian Empire]].<ref name="Murchison_1842">{{Cite book |last=Murchison |url=https://books.google.co.in/books?id=MDoAAAAAQAAJ&oe=UTF-8&redir_esc=y&hl=en |title=On the Geological Structure of the Central and Southern Regions of Russia in Europe, and of the Ural Mountains |last2=Murchison |first2=Sir Roderick Impey |last3=Verneuil |last4=Keyserling |first4=Graf Alexander |date=1842 |publisher=Print. by R. and J.E. Taylor |language=en}}</ref>

|-

|[[Carboniferous]]

|{{Period span/brief|Carboniferous|1}}

|Means 'coal-bearing', from the [[Latin]] carbō (''coal'') and ferō (''to bear, carry'').<ref name="Phillips_1835">{{Cite book |last=Phillips |first=John |url=https://books.google.com.au/books?hl=en&lr=&id=-7-ZqIkYBOMC&oi=fnd&pg=PA1&ots=RzJtkyaij-&sig=V-sym2NhvCYHReO6Dlq5ILQ0ndw&redir_esc=y#v=onepage&q&f=false |title=Illustrations of the Geology of Yorkshire: Or, A Description of the Strata and Organic Remains: Accompanied by a Geological Map, Sections and Plates of the Fossil Plants and Animals ... |date=1835 |publisher=J. Murray |language=en}}</ref>

|-

|[[Devonian]]

|{{Period span/brief|Devonian|1}}

|Named after [[Devon]], England.<ref name="Sedgwick_1840">{{Cite journal |last=Sedgwick |first=A. |last2=Murchison |first2=R. I. |date=1840-01-01 |title=XLIII.--On the Physical Structure of Devonshire, and on the Subdivisions and Geological Relations of its older stratified Deposits, &c. |url=https://books.google.com/books?id=QknWzPRnVRQC&pg=PA701 |journal=Transactions of the Geological Society of London |language=en |volume=s2-5 |issue=3 |pages=633–703 |doi=10.1144/transgslb.5.3.633 |issn=2042-5295}}</ref>

|-

|[[Silurian]]

|{{Period span/brief|Silurian|1}}

|Named after the [[Celts|Celtic]] tribe, the [[Silures]].<ref name ="Murchison_1835">{{Cite journal |last=Murchison |first=Roderick Impey |date=1835 |title=VII. On the silurian system of rocks |url=https://www.tandfonline.com/doi/full/10.1080/14786443508648654 |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |language=en |volume=7 |issue=37 |pages=46–52 |doi=10.1080/14786443508648654 |issn=1941-5966}}</ref>

|-

|[[Ordovician]]

|{{Period span/brief|Ordovician|1}}

|Named after the Celtic tribe, [[Ordovices]].<ref name="Lapworth_1879">{{Cite journal |last=Lapworth |first=Charles |date=1879 |title=I.—On the Tripartite Classification of the Lower Palæozoic Rocks |url=https://www.cambridge.org/core/product/identifier/S0016756800156560/type/journal_article |journal=Geological Magazine |language=en |volume=6 |issue=1 |pages=1–15 |doi=10.1017/S0016756800156560 |issn=0016-7568}}</ref><ref>{{Cite journal |last=Bassett |first=Michael G. |date=1979-06-01 |title=100 YEARS OF ORDOVICIAN GEOLOGY |url=http://www.episodes.org/journal/view.html?doi=10.18814/epiiugs/1979/v2i2/003 |journal=Episodes |language=en |volume=2 |issue=2 |pages=18–21 |doi=10.18814/epiiugs/1979/v2i2/003 |issn=0705-3797}}</ref>

|-

|[[Cambrian]]

|{{Period span/brief|Cambrian|1}}

|Named for [[Cambria]], a [[latin|latinised]] form of the Welsh name for [[Wales]], ''Crymu''.<ref>{{cite EB1911|wstitle=Cambria}}</ref>

|-

|[[Ediacaran]]

|{{Period span/brief|Cryogenian|1}}

|Named for the [[Ediacara Hills]]. Ediacara is possibly a corruption of the [[Kuyani]] words 'Yata Takarra' meaning hard or stony ground.<ref name="Butcher_2004">{{cite web |last=Butcher |first=Andy |date=26 May 2004 |title=Re: Ediacaran |url=http://listserv.linguistlist.org/cgi-bin/wa?A2=ind0405&L=australian-linguistics-l&D=1&P=264 |url-status=dead |archive-url=https://web.archive.org/web/20071023012434/http://listserv.linguistlist.org/cgi-bin/wa?A2=ind0405&L=australian-linguistics-l&D=1&P=264 |archive-date=23 October 2007 |access-date=19 July 2011 |work=LISTSERV 16.0 - AUSTRALIAN-LINGUISTICS-L Archives}}</ref><ref name="AHD_Ediacara_Fossil_Site">{{cite web |title=Place Details: Ediacara Fossil Site – Nilpena, Parachilna, SA, Australia |url=http://www.environment.gov.au/cgi-bin/ahdb/search.pl?mode=place_detail;place_id=105880 |url-status=live |archive-url=https://web.archive.org/web/20110603074010/http://www.environment.gov.au/cgi-bin/ahdb/search.pl?mode=place_detail;place_id=105880 |archive-date=3 June 2011 |access-date=19 July 2011 |work=Australian Heritage Database |publisher=Commonwealth of Australia |department=Department of Sustainability, Environment, Water, Population and Communities |df=dmy-all}}</ref>

|-

|[[Cryogenian]]

|{{Period span/brief|Cryogenian|1}}

|From the Greek words κρύος (''krýos'') meaning 'cold', and, γένεσις (''génesis'') meaning 'birth'.<ref name="GTS2012_Precambrian" />

|-

|[[Tonian]]

|{{Period span/brief|Tonian|1}}

|From the Greek word τόνος (''tónos'') meaning 'stretch'.<ref name="GTS2012_Precambrian" />

|-

|[[Stenian]]

|{{Period span/brief|Stenian|1}}

|From the Greek word στενός (''stenós'') meaning 'narrow'.<ref name="GTS2012_Precambrian" />

|-

|[[Ectasian]]

|{{Period span/brief|Ectasian|1}}

|From the Greek word ἔκτᾰσῐς (''éktasis'') meaning 'extension'.<ref name="GTS2012_Precambrian" />

|-

|[[Calymmian]]

|{{Period span/brief|Calymmian|1}}

|From the Greek word κάλυμμᾰ (''kálumma'') meaning 'cover'.<ref name="GTS2012_Precambrian" />

|-

|[[Statherian]]

|{{Period span/brief|Statherian|1}}

|From the Greek word σταθερός (''statherós'') meaning 'stable'.<ref name="GTS2012_Precambrian" />

|-

|[[Orosirian]]

|{{Period span/brief|Orosirian|1}}

|From the Greek word ὀροσειρά (''oroseirá'') meaning 'mountain range'.<ref name="GTS2012_Precambrian" />

|-

|[[Rhyacian]]

|{{Period span/brief|Rhyacian|1}}

|From the Greek word ῥύαξ (''rhýax'') meaning 'stream of lava'.<ref name="GTS2012_Precambrian" />

|-

|[[Siderian]]

|{{Period span/brief|Siderian|1}}

|From the Greek word σίδηρος (''sídiros'') meaning '[[iron]]'.<ref name="GTS2012_Precambrian" />

== History of the geologic time scale ==

{{See also|History of geology|History of paleontology}}

=== Early history ===

While a modern geological time scale was not formulated until 1911<ref name="Holmes_1911">{{Cite journal |date=1911-06-09 |title=The association of lead with uranium in rock-minerals, and its application to the measurement of geological time |url=https://doi.org/10.1098/rspa.1911.0036 |journal=Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character |volume=85 |issue=578 |pages=248–256 |doi=10.1098/rspa.1911.0036 |issn=0950-1207}}</ref> by [[Arthur Holmes]], the broader concept that rocks and time are related can be traced back to (at least) the [[Philosopher|philosophers]] of [[Ancient Greece]]. [[Xenophanes|Xenophanes of Colophon]] (c. 570–487&nbsp;[[Common era|BCE]]) observed rock beds with fossils of shells located above the sea-level, viewed them as once living organisms, and used this to imply an unstable relationship in which the sea had at times [[Marine transgression|transgressed]] over the land and at other times had [[Marine regression|regressed]].<ref name="Fischer_2009">{{Cite journal |last=Fischer |first=Alfred G. |last2=Garrison |first2=Robert E. |date=2009 |title=The role of the Mediterranean region in the development of sedimentary geology: a historical overview |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-3091.2008.01009.x |journal=Sedimentology |language=en |volume=56 |issue=1 |pages=3–41 |doi=10.1111/j.1365-3091.2008.01009.x}}</ref> This view was shared by a few of Xenophanes' contemporaries and those that followed, including [[Aristotle]] (384–322&nbsp;BCE) who (with additional observations) reasoned that the positions of land and sea had changed over long periods of time. The concept of [[deep time]] was also recognised by [[History of science and technology in China|Chinese naturalist]] [[Shen Kuo]]<ref name="Nathan 1995">{{Cite book |last=Nathan. |first=Sivin, |url=http://worldcat.org/oclc/956775994 |title=Science in ancient China : researches and reflections |date=1995 |publisher=Variorum |isbn=0-86078-492-4 |oclc=956775994}}</ref> (1031–1095) and [[Islam|Islamic]] [[scientist]]-philosophers, notably the [[Brethren of Purity|Brothers of Purity]], who wrote on the processes of stratification over the passage of time in their [[Encyclopedia of the Brethren of Purity|treatises]].<ref name="Fischer_2009" /> Their work likely inspired that of the 11th-century [[Persians|Persian]] [[polymath]] [[Avicenna]] (Ibn Sînâ, 980–1037) who wrote in ''[[The Book of Healing]]'' (1027) on the concept of stratification and superposition, pre-dating [[Nicolas Steno]] by more than six centuries.<ref name="Fischer_2009" /> Avicenna also recognised fossils as "petrifications of the bodes of plants and animals",<ref name="Adams_1938">{{Cite book |last=Adams |first=Frank D. |url=http://worldcat.org/oclc/165626104 |title=The Birth and Development of the Geological Sciences |date=1938 |publisher=Williams & Wilkins |isbn=0-486-26372-X |oclc=165626104}}</ref> with the 13th-century [[Dominican Order|Dominican]] [[bishop]] [[Albertus Magnus]] (c. 1200–1280) extending this into a theory of a petrifying fluid.<ref name="Rudwick_1985">{{Cite book |last=Rudwick |first=M. J. S. |url=https://www.worldcat.org/oclc/11574066 |title=The meaning of fossils : episodes in the history of palaeontology |date=1985 |publisher=University of Chicago Press |isbn=0-226-73103-0 |edition= |location=Chicago |oclc=11574066}}</ref>{{verification needed|date=April 2022|reason=The reference to Albertus Magnus and a petrifying fluid is a hangover from the original [[Geologic time scale]] article. I cannot confidently corroborate the source material against this statement.}} These works appeared to have little influence on [[Scholar|scholars]] in [[Middle Ages|Medieval Europe]] who looked to the [[Bible]] to explain the origins of fossils and sea-level changes, often attributing these to the '[[Genesis flood narrative|Deluge]]', including [[Restoro d'Arezzo|Ristoro d'Arezzo]] in 1282.<ref name="Fischer_2009" /> It was not until the [[Italian Renaissance]] when [[Leonardo da Vinci]] (1452–1519) would reinvigorate the relationships between stratification, relative sea-level change, and time, denouncing attribution of fossils to the 'Deluge':<ref name="McCurdy_1938">{{Cite book |last=McCurdy |first=Edward |url=https://www.worldcat.org/search?q=no:2233803&qt=advanced&dblist=638 |title=The notebooks of Leonardo da Vinci |date=1938 |publisher=Reynal & Hitchcock |location=New York |language=English |oclc=2233803}}</ref><ref name="Fischer_2009" />

{{blockquote|text=Of the stupidity and ignorance of those who imagine that these creatures were carried to such places distant from the sea by the Deluge...Why do we find so many fragments and whole shells between the different layers of stone unless they had been upon the shore and had been covered over by earth newly thrown up by the sea which then became petrified? And if the above-mentioned Deluge had carried them to these places from the sea, you would find the shells at the edge of one layer of rock only, not at the edge of many where may be counted the winters of the years during which the sea multiplied the layers of sand and mud brought down by the neighboring rivers and spread them over its shores. And if you wish to say that there must have been many deluges in order to produce these layers and the shells among them it would then become necessary for you to affirm that such a deluge took place every year.}}

These views of da Vinci remained unpublished, and thus lacked influence at the time; however, questions of fossils and their significance were pursued and, while views against [[Genesis creation narrative|Genesis]] were not readily accepted and dissent from [[Religion|religious]] doctrine was in some places unwise, scholars such as [[Girolamo Fracastoro]] shared da Vinci's views, and found the attribution of fossils to the 'Deluge' absurd.<ref name="Fischer_2009" />

=== Establishment of primary principles ===

Niels Stensen, more commonly known as Nicolas Steno (1638–1686), is credited with establishing four of the guiding principles of stratigraphy.<ref name="Fischer_2009" /> In ''De solido intra solidum naturaliter contento dissertationis prodromus'' Steno states:<ref name="Steno_1669">{{Cite book |last=Steno |first=Nicolaus |url=https://books.google.de/books?id=xz28AAAAIAAJ&printsec=frontcover&hl=de#v=onepage&q&f=false |title=Nicolai Stenonis de solido intra solidvm natvraliter contento dissertationis prodromvs ad serenissimvm Ferdinandvm II ... |date=1669 |publisher=W. Junk |language=la}}</ref><ref name="Kardel_2018">{{Citation |last=Kardel |first=Troels |title=2.27 The Prodromus to a Dissertation on a Solid Naturally Contained Within a Solid |date=2018 |url=http://link.springer.com/10.1007/978-3-662-55047-2_38 |work=Nicolaus Steno |pages=763–825 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |language=en |doi=10.1007/978-3-662-55047-2_38 |isbn=978-3-662-55046-5 |access-date=2022-04-20 |last2=Maquet |first2=Paul}}</ref>

<blockquote>

* When any given stratum was being formed, all the matter resting on it was fluid and, therefore, when the lowest stratum was being formed, none of the upper strata existed.

* ...strata which are either perpendicular to the horizon or inclined to it were at one time parallel to the horizon.

* When any given stratum was being formed, it was either encompassed at its edges by another solid substance or it covered the whole globe of the earth. Hence, it follows that wherever bared edges of strata are seen, either a continuation of the same strata must be looked for or another solid substance must be found that kept the material of the strata from being dispersed.

* If a body or discontinuity cuts across a stratum, it must have formed after that stratum.

</blockquote>

Respectively, these are the principles of superposition, original horizontality, lateral continuity, and cross-cutting relationships. From this Steno reasoned that strata were laid down in succession and inferred relative time (in Steno's belief, time from [[Creation myth|Creation]]). While Steno's principles were simple and attracted much attention, applying them proved challenging.<ref name="Fischer_2009" /> These basic principles, albeit with improved and more nuanced interpretations, still form the foundational principles of determining correlation of strata relative geologic time.

Over the course of the 18th-century geologists realised that:

* Sequences of strata often become eroded, distorted, tilted, or even inverted after deposition

* Strata laid down at the same time in different areas could have entirely different appearances

* The strata of any given area represented only part of Earth's long history

=== Formulation of a modern geologic time scale ===

The apparent, earliest formal division of the geologic record with respect to time was introduced by [[Thomas Burnet]] who applied a two-fold terminology to mountains by identifying "''montes primarii''" for rock formed at the time of the 'Deluge', and younger "''monticulos secundarios"'' formed later from the debris of the "''primarii"''.<ref name="Burnet_1681">{{Cite book |last=Burnet |first=Thomas |title=Telluris Theoria Sacra: orbis nostri originen et mutationes generales, quasi am subiit aut olim subiturus est, complectens. Libri duo priores de Diluvio & Paradiso |publisher=G. Kettiby |year=1681 |location=London |language=la}}</ref><ref name="Fischer_2009" /> This attribution to the 'Deluge', while questioned earlier by the likes of da Vinci, was the foundation of [[Abraham Gottlob Werner]]'s (1749–1817) [[Neptunism]] theory in which all rocks precipitated out of a single flood.<ref name="Werner_1787">{{Cite book |last=Werner |first=Abraham Gottlob |url=https://archive.org/details/bub_gb_DdhAAAAAcAAJ |title=Kurze Klassifikation und Beschreibung der verschiedenen Gebirgsarten |date=1787 |publisher=Walther |others= |location=Dresden |language=de}}</ref> A competing theory, [[Plutonism]], was developed by [[Anton Moro]] (1687–1784) and also used primary and secondary divisions for rock units.<ref name="Moro_1740">{{Cite book |last=Moro |first=Anton Lazzaro |url=https://books.google.com.au/books?id=03RBAAAAYAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false |title=De'crostacei e degli altri marini corpi che si truovano su'monti |date=1740 |publisher=Appresso Stefano Monti |language=it}}</ref><ref name="Fischer_2009" /> In this early version of the Plutonism theory, the interior of Earth was seen as hot, and this drove the creation of primary igneous and metamorphic rocks and secondary rocks formed contorted and fossiliferous sediments. These primary and secondary divisions were expanded on by [[Giovanni Targioni Tozzetti]] (1712–1783) and [[Giovanni Arduino (geologist)|Giovanni Arduino]] (1713–1795) to include tertiary and quaternary divisions.<ref name="Fischer_2009" /> These divisions were used to describe both the time during which the rocks were laid down, and the collection of rocks themselves (i.e., it was correct to say Tertiary rocks, and Tertiary Period). Only the Quaternary division is retained in the modern geologic time scale, while the Tertiary division was in use until the early 21st century. The Neputism and Plutonism theories would compete into the early [[19th century]] with a key driver for resolution of this debate being the work of [[James Hutton]] (1726–1797), in particular his ''[[Theory of the Earth]]'', first presented before the [[Royal Society of Edinburgh]] in 1785.<ref name="Hutton_1788">{{Cite journal |last=Hutton |first=James |date=1788 |title=X. Theory of the Earth; or an Investigation of the Laws observable in the Composition, Dissolution, and Restoration of Land upon the Globe . |url=https://www.cambridge.org/core/product/identifier/S0080456800029227/type/journal_article |journal=Transactions of the Royal Society of Edinburgh |language=en |volume=1 |issue=2 |pages=209–304 |doi=10.1017/S0080456800029227 |issn=0080-4568}}</ref><ref name="Hutton_1795v1">{{Cite book |last=Hutton |first=James |url=https://www.gutenberg.org/ebooks/12861 |title=Theory of the Earth |year=1795 |volume=1 |location=Edinburgh}}</ref><ref name="Hutton_1795v2">{{Cite book |last=Hutton |first=James |url=https://www.gutenberg.org/ebooks/14179 |title=Theory of the Earth |year=1795 |volume=2 |location=Edinburgh}}</ref> Hutton's theory would later become known as [[uniformitarianism]], popularised by [[John Playfair]]<ref name="Playfair_1802">{{Cite book |last=Playfair |first=John |url=http://archive.org/details/NHM104643 |title=Illustrations of the Huttonian theory of the earth |date=1802 |publisher=Neill & Co |others=Digitised by London Natural History Museum Library |location=Edinburgh}}</ref> (1748–1819) and later [[Charles Lyell]] (1797–1875) in his ''[[Principles of Geology]]''.<ref name="Lyell_1832v1">{{Cite book |last=Lyell |first=Sir Charles |url=https://books.google.com/books?id=mmIOAAAAQAAJ&newbks=0&hl=en |title=Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation |date=1832 |publisher=John Murray |volume=1 |location=London |language=en}}</ref><ref name="Lyell_1832v2">{{Cite book |last=Lyell |first=Sir Charles |url=https://books.google.com/books?id=TlwPAAAAYAAJ&newbks=0&hl=en |title=Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation |date=1832 |publisher=John Murray |volume=2 |location=London |language=en}}</ref><ref name="Lyell_1834v3">{{Cite book |last=Lyell |first=Sir Charles |url=https://books.google.com/books?id=UrIJAAAAIAAJ&newbks=0&hl=en |title=Principles of Geology: Being an Inquiry how for the Former Changes of the Earth's Surface are Referrable to Causes Now in Operation |date=1834 |publisher=John Murray |volume=3 |location=London |language=en}}</ref> Their theories strongly contested the 6,000 year age of the Earth as suggested determined by [[James Ussher]] via Biblical chronology that was accepted at the time by western religion. Instead, using geological evidence, they contested Earth to be much older, cementing the concept of deep time.

During the early 19th century [[William Smith (geologist)|William Smith]], [[Georges Cuvier]], [[Jean Baptiste Julien d'Omalius d'Halloy|Jean d'Omalius d'Halloy]], and [[Alexandre Brongniart]] pioneered the systematic division of rocks by stratigraphy and fossil assemblages. These geologists began to use the local names given to rock units in a wider sense, correlating strata across national and continental boundaries based on their similarity to each other. Many of the names below erathem/era rank in use on the modern ICC/GTS were determined during the early to mid-19th century.

=== The advent of geochronometry ===

During the 19th century, the debate regarding Earth's age was renewed, with geologists estimating ages based on [[denudation]] rates and sedimentary thicknesses or ocean chemistry, and physicists determining ages for the cooling of the Earth or the Sun using basic [[thermodynamics]] or orbital physics.<ref name="Dalrymple 2001 AoE" /> These estimations varied from 15,000 million years to 0.075 million years depending on method and author, but the estimations of [[William Thomson, 1st Baron Kelvin|Lord Kelvin]] and [[Clarence King]] were held in high regard at the time due to their pre-eminence in physics and geology. All of these early geochronometric determinations would later prove to be incorrect.

The discovery of [[radioactive decay]] by [[Henri Becquerel]], [[Marie Curie]], and [[Pierre Curie]] laid the ground work for radiometric dating, but the knowledge and tools required for accurate determination of radiometric ages would not be in place until the mid-1950s.<ref name="Dalrymple 2001 AoE" /> Early attempts at determining ages of uranium minerals and rocks by [[Ernest Rutherford]], [[Bertram Boltwood]], [[Robert Strutt, 4th Baron Rayleigh|Robert Strutt]], and Arthur Holmes, would culminate in what is considered the first international geological time scales by Holmes in 1911 and 1913.<ref name="Holmes_1911" /><ref name="Holmes 1913">{{Cite book |last=Holmes |first=Arthur |url=http://archive.org/details/ageofearth00holmuoft |title=The age of the earth |date=1913 |publisher=London, Harper |others=Gerstein - University of Toronto}}</ref><ref name="Lewis_2001">{{Cite journal |last=Lewis |first=Cherry L. E. |date=2001 |title=Arthur Holmes’ vision of a geological timescale |url=http://sp.lyellcollection.org/lookup/doi/10.1144/GSL.SP.2001.190.01.10 |journal=Geological Society, London, Special Publications |language=en |volume=190 |issue=1 |pages=121–138 |doi=10.1144/GSL.SP.2001.190.01.10 |issn=0305-8719}}</ref> The discovery of [[Isotope|isotopes]] in 1913<ref>{{Cite journal |last=Soddy |first=Frederick |date=1913-12-04 |title=Intra-atomic Charge |url=https://www.nature.com/articles/092399c0 |journal=Nature |language=en |volume=92 |issue=2301 |pages=399–400 |doi=10.1038/092399c0 |issn=0028-0836}}</ref> by [[Frederick Soddy]], and the developments in [[mass spectrometry]] pioneered by [[Francis William Aston]], [[Arthur Jeffrey Dempster]], and [[Alfred O. C. Nier]] during the early to mid-[[20th century]] would finally allow for the accurate determination of radiometric ages, with Holmes publishing several revisions to his ''geological time-scale'' with his final version in 1960.<ref name="Dalrymple 2001 AoE" /><ref name="Lewis_2001" /><ref name="Holmes_1960">{{Cite journal |last=Holmes |first=A. |date=1959-01-01 |title=A revised geological time-scale |url=http://trned.lyellcollection.org/cgi/doi/10.1144/transed.17.3.183 |journal=Transactions of the Edinburgh Geological Society |language=en |volume=17 |issue=3 |pages=183–216 |doi=10.1144/transed.17.3.183 |issn=0371-6260}}</ref><ref name="GTS1960">{{Cite journal |date=1960 |title=A Revised Geological Time-Scale |url=https://www.nature.com/articles/187027d0 |journal=Nature |language=en |volume=187 |issue=4731 |pages=27–28 |doi=10.1038/187027d0 |issn=0028-0836}}</ref>

=== Modern international geologic time scale ===

The establishment of the IUGS in 1961<ref name="Harrison_1978">{{Cite journal |last=Harrison |first=James M. |date=1978-03-01 |title=THE ROOTS OF IUGS |url=http://dx.doi.org/10.18814/epiiugs/1978/v1i1/005 |journal=Episodes |volume=1 |issue=1 |pages=20–23 |doi=10.18814/epiiugs/1978/v1i1/005 |issn=0705-3797}}</ref> and acceptance of the Commission on Stratigraphy (applied in 1965)<ref name="ICS_statutes_1986">{{Cite book |last=International Union of Geological Sciences. Commission on Stratigraphy |url=https://www.worldcat.org/oclc/14352783 |title=Guidelines and statutes of the International Commission on Stratigraphy (ICS) |date=1986 |publisher=Herausgegeben von der Senckenbergischen Naturforschenden Gesellschaft |others=J. W. Cowie |isbn=3-924500-19-3 |location=Frankfurt a.M. |oclc=14352783}}</ref> to become a member commission of IUGS led to the founding of the ICS. One of the primary objectives of the ICS is "the establishment, publication and revision of the ICS International Chronostratigraphic Chart which is the standard, reference global Geological Time Scale to include the ratified Commission decisions".<ref name="ICS_statutes" />

Following on from Holmes, several ''A Geological Time Scale'' books were published in 1982,<ref name="GTS82">{{Cite book |url=https://www.worldcat.org/oclc/8387993 |title=A geologic time scale |date=1982 |publisher=Cambridge University Press |others=W. B. Harland |isbn=0-521-24728-4 |location=Cambridge [England] |oclc=8387993}}</ref> 1989,<ref name="GTS1989">{{Cite book |url=https://www.worldcat.org/oclc/20930970 |title=A geologic time scale 1989 |date=1990 |publisher=Cambridge University Press |others=W. B. Harland |isbn=0-521-38361-7 |location=Cambridge |oclc=20930970}}</ref> 2004,<ref name="GTS2004">{{Cite book |url=https://www.worldcat.org/oclc/60770922 |title=A geologic time scale 2004 |date=2004 |publisher=Cambridge University Press |others=F. M. Gradstein, James G. Ogg, A. Gilbert Smith |isbn=0-511-08201-0 |location=Cambridge, UK |oclc=60770922}}</ref> 2008,<ref name="GTS2008">{{Cite journal |last=Gradstein |first=Felix M. |last2=Ogg |first2=James G. |last3=van Kranendonk |first3=Martin |date=2008-07-23 |title=On the Geologic Time Scale 2008 |url=http://www.schweizerbart.de/papers/nos/detail/43/63825/On_the_Geologic_Time_Scale_2008?af=crossref |journal=Newsletters on Stratigraphy |language=en |volume=43 |issue=1 |pages=5–13 |doi=10.1127/0078-0421/2008/0043-0005 |issn=0078-0421}}</ref> 2012,<ref name="GTS2012">{{Cite book |url=https://www.worldcat.org/oclc/808340848 |title=The geologic time scale 2012. Volume 2 |date=2012 |publisher=Elsevier |others=F. M. Gradstein |isbn=0-444-59448-5 |edition=1st |location=Amsterdam |oclc=808340848}}</ref> 2016,<ref name="GTS2016">{{Cite book |last=Ogg |first=James G. |url=https://www.worldcat.org/oclc/949988705 |title=A concise geologic time scale 2016 |date=2016 |publisher=Elsevier |others=Gabi Ogg, F. M. Gradstein |isbn=0-444-59468-X |location=Amsterdam, Netherlands |oclc=949988705}}</ref> and 2020.<ref name="GTS2020">{{Cite book |url=https://www.worldcat.org/oclc/1224105111 |title=Geologic time scale 2020 |date=2020 |others=F. M. Gradstein, James G. Ogg, Mark D. Schmitz, Gabi Ogg |isbn=0-12-824361-9 |location=Amsterdam, Netherlands |oclc=1224105111}}</ref> However, since 2013, the ICS has taken responsibility for producing and distributing the ICC citing the commercial nature, independent creation, and lack oversight of the by ICS on the prior published GTS versions (GTS books prior to 2013) although these versions were published in close association with the ICS.<ref name="ICC_Cohen_2013" /> Subsequent ''Geologic Time Scale'' books (2016<ref name="GTS2016" /> and 2020<ref name="GTS2020"/>) are commercial publications with no oversight from the ICS, and do not entirely conform to the chart produced by the ICS. The ICS produced GTS charts are versioned (year/month) beginning at v2013/01. At least one new version is published each year incorporating any changes ratified by the ICS since the prior version.

{{Timeline geological timescale}}

== Major proposed revisions to the ICC ==

=== Proposed Anthropocene Series/Epoch ===

{{Main|Anthropocene}}

First suggested in 2000,<ref =name"Crutzen_2021">{{Citation |last=Crutzen |first=Paul J. |title=The ‘Anthropocene’ (2000) |date=2021 |url=https://link.springer.com/10.1007/978-3-030-82202-6_2 |work=Paul J. Crutzen and the Anthropocene: A New Epoch in Earth’s History |volume=1 |pages=19–21 |editor-last=Benner |editor-first=Susanne |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-82202-6_2 |isbn=978-3-030-82201-9 |access-date=2022-04-15 |last2=Stoermer |first2=Eugene F. |editor2-last=Lax |editor2-first=Gregor |editor3-last=Crutzen |editor3-first=Paul J. |editor4-last=Pöschl |editor4-first=Ulrich}}</ref> the <em>Anthropocene</em> is a proposed epoch/series for the most recent time in Earth's history. While still informal, it is a widely used term to denote the present geologic time interval, in which many conditions and processes on Earth are profoundly altered by human impact.<ref>{{Cite web |title=Working Group on the ‘Anthropocene’ {{!}} Subcommission on Quaternary Stratigraphy |url=https://quaternary.stratigraphy.org/working-groups/anthropocene/ |archive-url=https://web.archive.org/web/20220407193255/https://quaternary.stratigraphy.org/working-groups/anthropocene/ |archive-date=2022-04-07 |access-date=2022-04-17 |language=en-US}}</ref> {{As of|2022|April}} the Anthropocene has not been ratified by the ICS; however, in May 2019 the [[Anthropocene Working Group]] voted in favour of submitting a formal proposal to the ICS for the establishment of the Anthropocene Series/Epoch.<ref name="Subramanian_2019">{{Cite journal |last=Subramanian |first=Meera |date=2019-05-21 |title=Anthropocene now: influential panel votes to recognize Earth’s new epoch |url=http://www.nature.com/articles/d41586-019-01641-5 |journal=Nature |language=en |pages=d41586–019–01641-5 |doi=10.1038/d41586-019-01641-5 |issn=0028-0836}}</ref> However, the definition of the Anthropocene as a geologic time period rather than a geologic event remains controversial and difficult.<ref name="Gibbard_2021">{{Cite journal |last=Gibbard |first=Philip L. |last2=Bauer |first2=Andrew M. |last3=Edgeworth |first3=Matthew |last4=Ruddiman |first4=William F. |last5=Gill |first5=Jacquelyn L. |last6=Merritts |first6=Dorothy J. |last7=Finney |first7=Stanley C. |last8=Edwards |first8=Lucy E. |last9=Walker |first9=Michael J. C. |last10=Maslin |first10=Mark |last11=Ellis |first11=Erle C. |date=2021-11-15 |title=A practical solution: the Anthropocene is a geological event, not a formal epoch |url=http://www.episodes.org/journal/view.html?doi=10.18814/epiiugs/2021/021029 |journal=Episodes |language=en |doi=10.18814/epiiugs/2021/021029 |issn=0705-3797}}</ref><ref name="Head_2021">{{Cite journal |last=Head |first=Martin J. |last2=Steffen |first2=Will |last3=Fagerlind |first3=David |last4=Waters |first4=Colin N. |last5=Poirier |first5=Clement |last6=Syvitski |first6=Jaia |last7=Zalasiewicz |first7=Jan A. |last8=Barnosky |first8=Anthony D. |last9=Cearreta |first9=Alejandro |last10=Jeandel |first10=Catherine |last11=Leinfelder |first11=Reinhold |date=2021-11-15 |title=The Great Acceleration is real and provides a quantitative basis for the proposed Anthropocene Series/Epoch |url=http://www.episodes.org/journal/view.html?doi=10.18814/epiiugs/2021/021031 |journal=Episodes |language=en |doi=10.18814/epiiugs/2021/021031 |issn=0705-3797}}</ref><ref name="Zalasiewicz_2021">{{Cite journal |last=Zalasiewicz |first=Jan |last2=Waters |first2=Colin N. |last3=Ellis |first3=Erle C. |last4=Head |first4=Martin J. |last5=Vidas |first5=Davor |last6=Steffen |first6=Will |last7=Thomas |first7=Julia Adeney |last8=Horn |first8=Eva |last9=Summerhayes |first9=Colin P. |last10=Leinfelder |first10=Reinhold |last11=McNeill |first11=J. R. |date=2021 |title=The Anthropocene: Comparing Its Meaning in Geology (Chronostratigraphy) with Conceptual Approaches Arising in Other Disciplines |url=https://onlinelibrary.wiley.com/doi/10.1029/2020EF001896 |journal=Earth's Future |language=en |volume=9 |issue=3 |doi=10.1029/2020EF001896 |issn=2328-4277}}</ref><ref name="Bauer_2021">{{Cite journal |last=Bauer |first=Andrew M. |last2=Edgeworth |first2=Matthew |last3=Edwards |first3=Lucy E. |last4=Ellis |first4=Erle C. |last5=Gibbard |first5=Philip |last6=Merritts |first6=Dorothy J. |date=2021-09-16 |title=Anthropocene: event or epoch? |url=https://www.nature.com/articles/d41586-021-02448-z |journal=Nature |language=en |volume=597 |issue=7876 |pages=332–332 |doi=10.1038/d41586-021-02448-z |issn=0028-0836}}</ref>

=== Proposals for revisions to pre-Cryogenian timeline ===

==== Shields et al. 2021 ====

An international working group of the ICS on pre-Cryogenian chronostratigraphic subdivision have outlined a template to improve the pre-Cyrogenian 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 pre-Cambrian,{{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 |last=Strachan |first=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.}}</ref> Their recommend revisions<ref name="Shields_2022_pre-Cryogenian" /> of the pre-Cryogenian geologic time scale were (changes from the current scale [v2022/02] are italicised):

* 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–<em>2450</em> Ma)

*** Paleoarchean (4000–<em>3500</em> Ma)

*** Mesoarchean (<em>3500–3000</em> Ma)

*** Neoarchean (<em>3500–2450</em> Ma)

**** <em>Kratian</em> (no fixed time given, prior to the Siderian) – from Greek word ''κράτος'' (krátos), meaning strength.

**** Siderian (?–<em>2450</em> 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 (<em>2450–1800</em> Ma)

*** <em>Skourian</em> (<em>2450</em>–2300 Ma) – from the Greek word σκουριά (''skouriá''), meaning 'rust'.

*** Rhyacian (2300–2050 Ma)

*** Orosirian (2050–1800 Ma)

** Mesoproterozoic (<em>1800</em>–1000 Ma)

*** <em>Statherian</em> (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 v2022/02 as the formal definition for the base of the Cambrian has not changed.|name=EdiacaranDate|group=note}}

*** <em>Kleisian</em> or <em>Syndian</em> (<em>1000–800</em> Ma) – respectively from the Greek words κλείσιμο (''kleísimo'') meaning 'closure', and σύνδεση (''sýndesi'') meaning 'connection'.

*** Tonian (<em>800</em>–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>

Current ICC pre-Cambrian timeline (v2022/02), 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:-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: -2500 till: -538.8 text:Proterozoic color:proterozoic

from: -4000 till: -2500 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: -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: -4000 till: -3600 text:Eoarchean color:eoarchean

from: start till: -4000 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>

==== Van Kranendonk et al. 2012 (GTS2012) ====

The book, ''Geologic Time Scale 2012,'' was the last commercial publication of an international chronostratigraphic chart that was closely associated with the ICS.<ref name="ICC_Cohen_2013" /> It included a proposal to substantially revise the pre-Cryogenian time scale to reflect important events such as the [[Formation and evolution of the Solar System|formation of the solar system]] and the [[Great Oxidation Event]], among others, while at the same time maintaining most of the previous chronostratigraphic nomenclature for the pertinent time span.<ref name="GTS2012">{{cite book |last=Van Kranendonk |first=Martin J. |title=The geologic time scale 2012 |date=2012 |publisher=Elsevier |isbn=978-0-44-459425-9 |editor=Felix M. Gradstein |edition=1st |location=Amsterdam |pages=359–365 |chapter=16: A Chronostratigraphic Division of the Precambrian: Possibilities and Challenges |doi=10.1016/B978-0-444-59425-9.00016-0 |editor2=James G. Ogg |editor3=Mark D. Schmitz |editor4=abi M. Ogg}}</ref> {{As of|2022|April}} these proposed changes have not been accepted by the ICS. The proposed changes were (changes from the current scale [v2022/02] are italicised):

* Hadean Eon (<em>4567–4030</em> Ma)

** [[Chaotian (geology)|Chaotian]] Era/Erathem (4567–4404 Ma) – the name alluding both to the [[Chaos (cosmogony)|mythological Chaos]] and the [[Chaos theory|chaotic]] phase of [[planet formation]].<ref name="GTS2012" /><ref name="Goldblatt_2010">{{cite journal |last1=Goldblatt |first1=C. |last2=Zahnle |first2=K. J. |last3=Sleep |first3=N. H. |last4=Nisbet |first4=E. G. |date=2010 |title=The Eons of Chaos and Hades |journal=Solid Earth |volume=1 |issue=1 |pages=1–3 |bibcode=2010SolE....1....1G |doi=10.5194/se-1-1-2010 |doi-access=free}}</ref><ref>{{cite journal |last=Chambers |first=John E. |date=July 2004 |title=Planetary accretion in the inner Solar System |url=http://www.astro.washington.edu/courses/astro321/Chambers_EPSL_04.pdf |journal=Earth and Planetary Science Letters |volume=223 |issue=3–4 |pages=241–252 |bibcode=2004E&PSL.223..241C |doi=10.1016/j.epsl.2004.04.031}}</ref>

** <em>Jack Hillsian</em> or <em>Zirconian</em> Era/Erathem (<em>4404–4030</em> Ma) – both names allude to the Jack Hills Greenstone Belt which provided the oldest mineral grains on Earth, [[Zircon|zircons]].<ref name="GTS2012" /><ref name="Goldblatt_2010" />

* Archean Eon/Eonothem (<em>4030–2420</em> Ma)

** Paleoarchean Era/Erathem (<em>4030–3490</em> Ma)

*** <em>Acastan</em> Period/System (<em>4030–3810</em> Ma) – named after the [[Acasta Gneiss]], one of the oldest preserved pieces of [[continental crust]].<ref name="GTS2012" /><ref name="Goldblatt_2010" />

*** <em>Isuan</em> Period (3<em>810–3490</em> Ma) – named after the [[Isua Greenstone Belt]].<ref name="GTS2012" />

** Mesoarchean Era/Erathem (<em>3490–2780</em> Ma)

*** <em>Vaalbaran</em> Period/System (<em>3490–3020</em> Ma) – based on the names of the [[Kapvaal craton|Kapvaal]] (Southern Africa) and [[Pilbara Craton|Pilbara]] (Western Australia) [[Craton|cratons,]] to reflect the growth of stable continental nuclei or proto-[[Craton|cratonic]] kernels.<ref name="GTS2012" />

*** <em>Pongolan</em> Period/System (<em>3020–2780</em> Ma) – named after the Pongola Supergroup, in reference to the well preserved evidence of terrestrial microbial communities in those rocks.<ref name="GTS2012" />

** Neoarchean Era/Erathem (<em>2780–2420</em> Ma)

*** <em>Methanian</em> Period/System (<em>2780–2630</em> Ma) – named for the inferred predominance of [[methanotrophic]] [[prokaryotes]]<ref name="GTS2012" />

*** Siderian Period/System (<em>2630–2420</em> Ma) – named for the voluminous [[Banded iron formation|banded iron formations]] formed within its duration.<ref name="GTS2012" />

* Proterozoic Eon/Eonothem (<em>2420</em>–538.8 Ma){{efn|name=EdiacaranDate|group=note}}

** Paleoproterozoic Era/Erathem (<em>2420–1780</em> Ma)

*** <em>Oxygenian</em> Period/System (<em>2420–2250</em> Ma) – named for displaying the first evidence for a global oxidizing atmosphere.<ref name="GTS2012" />

*** <em>Jatulian</em> or <em>Eukaryian</em> Period/System (<em>2250–2060</em> Ma) – names are respectively for the Lomagundi–Jatuli δ¹³C isotopic excursion event spanning its duration, and for the (proposed)<ref name="El_Albani_2014">{{cite journal |last1=El Albani |first1=Abderrazak |last2=Bengtson |first2=Stefan |last3=Canfield |first3=Donald E. |last4=Riboulleau |first4=Armelle |last5=Rollion Bard |first5=Claire |last6=Macchiarelli |first6=Roberto |display-authors=etal |year=2014 |title=The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity |journal=PLOS ONE |volume=9 |issue=6 |pages=e99438 |bibcode=2014PLoSO...999438E |doi=10.1371/journal.pone.0099438 |pmc=4070892 |pmid=24963687 |doi-access=free}}</ref><ref name="El_Albani_2010">{{cite journal |last1=El Albani |first1=Abderrazak |last2=Bengtson |first2=Stefan |last3=Canfield |first3=Donald E. |last4=Bekker |first4=Andrey |last5=Macchiarelli |first5=Roberto |last6=Mazurier |first6=Arnaud |last7=Hammarlund |first7=Emma U. |display-authors=etal |year=2010 |title=Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago |url=http://www.afrikibouge.com/publications/Article%20Albani.pdf |journal=Nature |volume=466 |issue=7302 |pages=100–104 |bibcode=2010Natur.466..100A |doi=10.1038/nature09166 |pmid=20596019 |s2cid=4331375}}{{Dead link|date=February 2022|bot=InternetArchiveBot|fix-attempted=yes}}</ref> first fossil appearance of [[Eukaryota|eukaryotes]].<ref name="GTS2012" />

*** <em>Columbian Period/System</em> (<em>2060–1780</em> Ma) – named after the [[supercontinent]] [[Columbia (supercontinent)|Columbia]].<ref name="GTS2012" />

** Mesoproterozoic Era/Erathem (<em>1780–850</em> Ma)

*** <em>Rodinian</em> Period/System (<em>1780–850</em> Ma) – named after the supercontinent [[Rodinia]], stable environment.<ref name="GTS2012" />

Proposed pre-Cambrian timeline (GTS2012), shown to scale:

<timeline>

ImageSize = width:1200 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:rodinian value:rgb(0.996,0.75,0.478)

id:paleoproterozoic value:rgb(0.968,0.263,0.44)

id:columbian value:rgb(0.968,0.459,0.655)

id:eukaryian value:rgb(0.968,0.408,0.596)

id:oxygenian 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:siderian value:rgb(0.976,0.7,0.85)

id:methanian value:rgb(0.976,0.65,0.8)

id:mesoarchean value:rgb(0.968,0.408,0.662)

id:pongolan value:rgb(0.968,0.5,0.75)

id:vaalbaran value:rgb(0.968,0.45,0.7)

id:paleoarchean value:rgb(0.96,0.266,0.624)

id:isuan value:rgb(0.96,0.35,0.65)

id:acastan value:rgb(0.96,0.3,0.6)

id:hadean value:rgb(0.717,0,0.494)

id:zirconian value:rgb(0.902,0.114,0.549)

id:chaotian value:rgb(0.8,0.05,0.5)

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: -2420 till: -538.8 text:Proterozoic color:proterozoic

from: -4030 till: -2420 text:Archean color:archean

from: -4567 till: -4030 text:Hadean color:hadean

from: start till: -4567 color:white

bar:Erathem/Era

from: -850 till: -538.8 text:Neoproterozoic color:neoproterozoic

from: -1780 till: -850 text:Mesoproterozoic color:mesoproterozoic

from: -2420 till: -1780 text:Paleoproterozoic color:paleoproterozoic

from: -2780 till: -2420 text:Neoarchean color:neoarchean

from: -3490 till: -2780 text:Mesoarchean color:mesoarchean

from: -4030 till: -3490 text:Paleoarchean color:paleoarchean

from: -4404 till: -4030 text:Zirconian color:zirconian

from: -4567 till: -4404 text:Chaotian color:chaotian

from: start till: -4567 color:white

bar:System/Period fontsize:7

from: -630 till: -538.8 text:Ed. color:ediacaran

from: -850 till: -630 text:Cr. color:cryogenian

from: -1780 till: -850 text:Rodinian color:rodinian

from: -2060 till: -1780 text:Columbian color:columbian

from: -2250 till: -2060 text:Eukaryian color:eukaryian

from: -2420 till: -2250 text:Oxygenian color:oxygenian

from: -2630 till: -2420 text:Siderian color:siderian

from: -2780 till: -2630 text:Methanian color:methanian

from: -3020 till: -2780 text:Pongolan color:pongolan

from: -3490 till: -3020 text:Vaalbaran color:vaalbaran

from: -3810 till: -3490 text:Isuan color:isuan

from: -4030 till: -3810 text:Acastan color:acastan

from: start till: -4030 color:white

</timeline>

Current ICC pre-Cambrian timeline (v2022/02), shown to scale:

<timeline>

ImageSize = width:1200 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:-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: -2500 till: -538.8 text:Proterozoic color:proterozoic

from: -4000 till: -2500 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: -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: -4000 till: -3600 text:Eoarchean color:eoarchean

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: -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>

The following table summarises the major events and characteristics of the divisions making up the geologic time scale of Earth. This table is arranged with the most recent geologic periods at the top, and the oldest at the bottom. The height of each table entry does not correspond to the duration of each subdivision of time. As such, this table is not to scale and does not accurately represent the relative time-spans of each geochronologic unit. While the [[Phanerozoic]] Eon looks longer than the rest, it merely spans ~539 million years (~12% of Earth's history), whilst the previous three eons{{Efn|name=Precam|group=note}} collectively span ~3,461 million years (~76% of Earth's history). This bias toward the most recent eon is in part due to the relative lack of information about events that occurred during the first three eons compared to the current eon (the Phanerozoic).<ref name="Shields_2022_pre-Cryogenian" /><ref>{{cite web |title=Geological time scale |url=https://www.digitalatlasofancientlife.org/learn/geological-time/geological-time-scale/ |access-date=January 17, 2022 |work=Digital Atlas of Ancient Life |publisher=Paleontological Research Institution}}</ref> The use of subseries/subepochs has been ratified by the ICS.<ref name ="Aubry_2022_subseries"/>

The content of the table is based on the official ICC produced and maintained by the ICS who also provide an online interactive version of this chart. The interactive version is based on a service delivering a machine-readable [[Resource Description Framework]]/[[Web Ontology Language]] representation of the time scale, which is available through the [[Commission for the Management and Application of Geoscience Information]] [[GeoSciML]] project as a service<ref name="web_GTSelements">{{cite web |title=Geologic Timescale Elements in the International Chronostratigraphic Chart |url=http://resource.geosciml.org/classifier/ics/ischart/ |access-date=2014-08-03}}</ref> and at a [[SPARQL]] end-point.<ref name="web_Cox_SPARQL_GTS">{{cite web |last=Cox |first=Simon J. D. |title=SPARQL endpoint for CGI timescale service |url=http://resource.geosciml.org/sparql/isc2014 |url-status=dead |archive-url=https://archive.today/20140806164132/http://resource.geosciml.org/sparql/isc2014 |archive-date=2014-08-06 |access-date=2014-08-03}}</ref><ref name="Cox_2014">{{cite journal |last1=Cox |first1=Simon J. D. |last2=Richard |first2=Stephen M. |year=2014 |title=A geologic timescale ontology and service |journal=Earth Science Informatics |volume=8 |pages=5–19 |doi=10.1007/s12145-014-0170-6 |s2cid=42345393}}</ref>

!Eonothem/<br/>Eon

!Erathem/<br/>Era

!System/<br/>Period

!Series/<br/>Epoch

!Stage/<br/>Age

!Major events

!Start, million years ago<br/>{{efn|The dates and uncertainties quoted are according to the [[International Commission on Stratigraphy]] International Chronostratigraphic chart (v2022/02). A ^* indicates boundaries where a [[Global Boundary Stratotype Section and Point]] has been internationally agreed upon.|name="ICC-dates"|group=note}}

| rowspan="102" style="background:{{period color|Phanerozoic}}" |[[Phanerozoic]]

| rowspan="24" style="background:{{period color|Cenozoic}}" |[[Cenozoic]]<br/>{{efn|name=Tertiary|group=note}}

| rowspan="7" style="background:{{period color|Quaternary}}" |[[Quaternary]]

| rowspan="3" style="background:{{period color|Holocene}}" |[[Holocene]]

| style="background:#fcf0f2" |[[Meghalayan]]

|[[4.2-kiloyear event]], [[Austronesian expansion]], increasing [[Industrial Revolution|industrial]] [[Carbon dioxide in the Earth's atmosphere|CO₂]].

| style="background:#fcf0f2" |{{Period start|meghalayan}} {{Period start error|meghalayan}}^*

| style="background:#fcf0e8" |[[Northgrippian]]

|[[8.2-kiloyear event]], [[Holocene climatic optimum]]. [[Sea level]] flooding of [[Doggerland]] and [[Sundaland]]. [[Sahara]] becomes a desert. End of Stone Age and start of [[recorded history]]. Humans finally expand into the [[Arctic Archipelago]] and [[Greenland]].

| style="background:#fcf0e8" |{{Period start|northgrippian}} {{Period start error|northgrippian}}^*

| style="background:#fcf0de" |[[Greenlandian]]

|Climate stabilizes. Current [[interglacial]] and [[Holocene extinction]] begins. [[Neolithic revolution|Agriculture begins]]. Humans spread across the [[wet Sahara]] and [[Arabia]], the [[Extreme North]], and the Americas (mainland and the [[Caribbean]]).

| style="background:#fcf0de" |{{Period start|greenlandian}} {{Period start error|greenlandian}}^*

| rowspan="4" style="background:{{period color|Pleistocene}}" |[[Pleistocene]]

| style="background:{{period color|Upper Pleistocene}}" |[[Late Pleistocene|Upper/Late]] ''('[[Tarantian]]')''

|[[Eemian]] [[interglacial]], [[last glacial period]], ending with [[Younger Dryas]]. [[Toba catastrophe theory|Toba eruption]]. [[Quaternary extinction|Pleistocene megafauna (including the last terror birds) extinction]]. Humans expand into [[Near Oceania]] and the [[Americas]].

| style="background:{{period color|upper Pleistocene}}" |{{Period start|Late pleistocene}} {{Period start error|Late pleistocene}}

| style="background:{{period color|Middle Pleistocene}}" |[[Chibanian]]

| style="background:{{period color|Middle Pleistocene}}" |{{Period start|middle pleistocene}}{{Period start error|middle pleistocene}}^*

| style="background:{{period color|Calabrian}}" |[[Early Pleistocene|Calabrian]]

| style="background:{{period color|Calabrian}}" |{{Period start|calabrian}} {{Period start error|calabrian}}^*

| style="background:{{period color|Gelasian}}" |[[Gelasian]]

|Start of [[Quaternary glaciation|Quaternary glaciations]] and unstable climate.<ref name="Hoag_2017">{{Cite journal |last=Hoag |first=Colin |last2=Svenning |first2=Jens-Christian |date=2017-10-17 |title=African Environmental Change from the Pleistocene to the Anthropocene |url=https://www.annualreviews.org/doi/10.1146/annurev-environ-102016-060653 |journal=Annual Review of Environment and Resources |language=en |volume=42 |issue=1 |pages=27–54 |doi=10.1146/annurev-environ-102016-060653 |issn=1543-5938}}</ref> Rise of the [[Pleistocene megafauna]] and [[Homo habilis]].

| style="background:{{period color|Gelasian}}" |{{Period start|gelasian}} {{Period start error|geliasian}}^*

| rowspan="8" style="background:{{period color|Neogene}}" |[[Neogene]]

| rowspan="2" style="background:{{period color|Pliocene}}" |[[Pliocene]]

| style="background:{{period color|Piacenzian}}" |[[Piacenzian]]

|[[Greenland ice sheet]] develops<ref name="Bartoli_2005">{{cite journal |last1=Bartoli |first1=G |last2=Sarnthein |first2=M |last3=Weinelt |first3=M |last4=Erlenkeuser |first4=H |last5=Garbe-Schönberg |first5=D |last6=Lea |first6=D.W |year=2005 |title=Final closure of Panama and the onset of northern hemisphere glaciation |journal=Earth and Planetary Science Letters |volume=237 |issue=1–2 |pages=33–44 |bibcode=2005E&PSL.237...33B |doi=10.1016/j.epsl.2005.06.020 |doi-access=free}}</ref> as the cold slowly intensifies towards the Pleistocene. Atmospheric {{O2}} and {{CO2}} content reaches present day levels while landmasses also reach their current locations (e.g. the [[Isthmus of Panama]] joins the [[North America|North]] and [[South America|South Americas]], while allowing [[Great American Interchange|a faunal interchange]]). The last non-marsupial metatherians go extinct. [[Australopithecus]] common in East Africa; [[Stone Age]] begins.<ref name="Tyson_2009">{{cite web |last=Tyson |first=Peter |date=October 2009 |title=NOVA, Aliens from Earth: Who's who in human evolution |url=https://www.pbs.org/wgbh/nova/hobbit/tree-nf.html |access-date=2009-10-08 |publisher=PBS}}</ref>

| style="background:{{period color|Piacenzian}}" |{{Period start|piacenzian}} {{Period start error|piacenzian}}^*

| style="background:{{period color|Zanclean}}" |[[Zanclean]]

|[[Zanclean flood|Zanclean flooding]] of the [[Mediterranean Basin]]. Cooling climate continues from the Miocene. First [[equines]] and [[Elephantimorpha|elephantines]]. [[Ardipithecus]] in Africa.<ref name="Tyson_2009" />

| style="background:{{period color|Zanclean}}" |{{Period start|zanclean}} {{Period start error|zanclean}}^*

| rowspan="6" style="background:{{period color|Miocene}}" |[[Miocene]]

| style="background:{{period color|Messinian}}" |[[Messinian]]

| rowspan="2" |[[Messinian Event]] with hypersaline lakes in empty [[Mediterranean Basin]]. [[Greenhouse and Icehouse Earth|Moderate icehouse climate]], punctuated by [[Ice age|ice ages]] and re-establishment of [[East Antarctic Ice Sheet]]. [[Choristodera|Choristoderes]], the last non-crocodilian [[Sebecosuchia|crocodylomorphs]] and [[creodonts]] go extinct. After [[Gorilla-human last common ancestor|separating from gorilla ancestors]], [[Chimpanzee–human last common ancestor|chimpanzee and human ancestors]] gradually separate; [[Sahelanthropus]] and [[Orrorin]] in Africa.

| style="background:{{period color|Messinian}}" |{{Period start|messinian}} {{Period start error|messinian}}^*

| style="background:{{period color|Tortonian}}" |[[Tortonian]]

| style="background:{{period color|Tortonian}}" |{{Period start|tortonian}} {{Period start error|tortonian}}^*

| style="background:{{period color|Serravallian}}" |[[Serravallian]]

| rowspan="2" |Middle Miocene climate optimum temporarily provides a warm climate. <ref name="Gannon_2013_BryantUniHons">{{Cite journal |last=Gannon |first=Colin |date=2013-04-26 |title=Understanding the Middle Miocene Climatic Optimum: Evaluation of Deuterium Values (δD) Related to Precipitation and Temperature |url=https://digitalcommons.bryant.edu/honors_science/11 |journal=Honors Projects in Science and Technology}}</ref> Extinctions in [[middle Miocene disruption]], decreasing shark diversity. First [[Hippo|hippos]]. Ancestor of [[great apes]].

| style="background:{{period color|Serravallian}}" |{{Period start|serravallian}} {{Period start error|serravallian}}^*

| style="background:{{period color|Langhian}}" |[[Langhian]]

| style="background:{{period color|Langhian}}" |{{Period start|langhian}} {{Period start error|langhian}}

| style="background:{{period color|Burdigalian}}" |[[Burdigalian]]

| rowspan="2" |[[Orogeny]] in [[Northern Hemisphere]]. Start of [[Kaikoura Orogeny]] forming [[Southern Alps in New Zealand]]. Widespread forests slowly [[Photosynthesis|draw in]] massive amounts of {{CO2}}, gradually lowering the level of atmospheric {{CO2}} from 650 ppmv down to around 100 ppmv during the Miocene.<ref name="Royer_2006">{{cite journal |last1=Royer |first1=Dana L. |year=2006 |title=CO₂-forced climate thresholds during the Phanerozoic |url=http://droyer.web.wesleyan.edu/PhanCO2%28GCA%29.pdf |url-status=dead |journal=Geochimica et Cosmochimica Acta |volume=70 |issue=23 |pages=5665–75 |bibcode=2006GeCoA..70.5665R |doi=10.1016/j.gca.2005.11.031 |archive-url=https://web.archive.org/web/20190927033455/http://droyer.web.wesleyan.edu/PhanCO2%28GCA%29.pdf |archive-date=27 September 2019 |access-date=6 August 2015}}</ref>{{efn|For more information on this, see [[Atmosphere of Earth#Evolution of Earth's atmosphere]], [[Carbon dioxide in the Earth's atmosphere]], and [[Climate variability and change|climate change]]. Specific graphs of reconstructed {{CO2}} levels over the past ~550, 65, and 5 million years can be seen at [[:File:Phanerozoic Carbon Dioxide.png]], [[:File:65 Myr Climate Change.png]], [[:File:Five Myr Climate Change.png]], respectively.|name="atmospheric-carbon-dioxide"|group=note}} Modern [[bird]] and mammal families become recognizable. The last of the primitive whales go extinct. [[Grass|Grasses]] become ubiquitous. Ancestor of [[apes]], including humans.<ref name="web_LS_2017">{{cite web |date=10 August 2017 |title=Here's What the Last Common Ancestor of Apes and Humans Looked Like |url=https://www.livescience.com/60093-last-common-ancestor-of-apes-humans-revealed.html |website=[[Live Science]]}}</ref><ref name="Nengo_2017">{{Cite journal |last=Nengo |first=Isaiah |last2=Tafforeau |first2=Paul |last3=Gilbert |first3=Christopher C. |last4=Fleagle |first4=John G. |last5=Miller |first5=Ellen R. |last6=Feibel |first6=Craig |last7=Fox |first7=David L. |last8=Feinberg |first8=Josh |last9=Pugh |first9=Kelsey D. |last10=Berruyer |first10=Camille |last11=Mana |first11=Sara |date=2017 |title=New infant cranium from the African Miocene sheds light on ape evolution |url=http://www.nature.com/articles/nature23456 |journal=Nature |language=en |volume=548 |issue=7666 |pages=169–174 |doi=10.1038/nature23456 |issn=0028-0836}}</ref> Afro-Arabia collides with Eurasia, fully forming the [[Alpide Belt]] and closing the Tethys Ocean, while allowing a faunal interchange. At the same time, Afro-Arabia splits into [[Africa]] and [[Arabian Plate|West Asia]].

| style="background:{{period color|Burdigalian}}" |{{Period start|burdigalian}} {{Period start error|burdigalian}}

| style="background:{{period color|Aquitanian}}" |[[Aquitanian age|Aquitanian]]

| style="background:{{period color|Aquitanian}}" |{{Period start|aquitanian}} {{Period start error|anquitanian}}^*

| rowspan="9" style="background:{{period color|Paleogene}}" |[[Paleogene]]

| rowspan="2" style="background:{{period color|Oligocene}}" |[[Oligocene]]

| style="background:{{period color|Chattian}}" |[[Chattian]]

| rowspan="2" |[[Eocene–Oligocene extinction event|Grande Coupure]] extinction. Start of widespread [[Late Cenozoic Ice Age|Antarctic glaciation]].<ref name="Deconto_2003">{{Cite journal |last1=Deconto |first1=Robert M. |last2=Pollard |first2=David |year=2003 |title=Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2 |journal=Nature |volume=421 |issue=6920 |pages=245–249 |bibcode=2003Natur.421..245D |doi=10.1038/nature01290 |pmid=12529638 |s2cid=4326971}}</ref> Rapid [[evolution]] and diversification of fauna, especially [[Mammal|mammals]] (e.g. first [[Macropodiformes|macropods]] and [[Pinnipedia|seals]]). Major evolution and dispersal of modern types of [[Flowering plant|flowering plants]]. [[Cimolesta|Cimolestans]], miacoids and condylarths go extinct. First [[Cetacea|neocetes]] (modern, fully aquatic whales) appear.

| style="background:{{period color|Chattian}}" |{{Period start|chattian}} {{Period start error|chattian}}

| style="background:{{period color|Rupelian}}" |[[Rupelian]]

| style="background:{{period color|Rupelian}}" |{{Period start|rupelian}} {{Period start error|rupelian}}^*

| rowspan="4" style="background:{{period color|Eocene}}" |[[Eocene]]

| style="background:{{period color|Priabonian}}" |[[Priabonian]]

| rowspan="3" |[[Greenhouse and Icehouse Earth|Moderate, cooling climate]]. Archaic [[Mammal|mammals]] (e.g. [[Creodont|creodonts]], [[Miacoidea|miacoids]], "[[Condylarth|condylarths]]" etc.) flourish and continue to develop during the epoch. Appearance of several "modern" mammal families. [[Archaeoceti|Primitive whales]] and [[sea cows]] diversify after returning to water. [[Birds]] continue to diversify. First [[kelp]], [[Diprotodontia|diprotodonts]], [[bears]] and [[simians]]. The multituberculates and leptictidans go extinct by the end of the epoch. Reglaciation of Antarctica and formation of its [[ice cap]]; End of [[Laramide Orogeny|Laramide]] and [[Sevier orogeny|Sevier Orogenies]] of the [[Rocky Mountains]] in North America. [[Hellenic orogeny|Hellenic Orogeny]] begins in Greece and [[Aegean Sea]].

| style="background:{{period color|Priabonian}}" |{{Period start|priabonian}} {{Period start error|priabonian}}^*

| style="background:{{period color|Bartonian}}" |[[Bartonian]]

| style="background:{{period color|Bartonian}}" |{{Period start|bartonian}} {{Period start error|bartonian}}

| style="background:{{period color|Lutetian}}" |[[Lutetian]]

| style="background:{{period color|Lutetian}}" |{{Period start|lutetian}} {{Period start error|lutetian}}^*

| style="background:{{period color|Ypresian}}" |[[Ypresian]]

|Two transient events of global warming ([[Paleocene–Eocene Thermal Maximum|PETM]] and [[Eocene Thermal Maximum 2|ETM-2]]) and warming climate until the [[Eocene Climatic Optimum]]. The [[Azolla event]] decreased {{CO2}} levels from 3500 ppm to 650 ppm, setting the stage for a long period of cooling.<ref name="Royer_2006" />{{efn|name="atmospheric-carbon-dioxide"|group=note}} [[Indian subcontinent|Greater India]] collides with Eurasia and starts [[Geology of the Himalaya|Himalayan Orogeny]] (allowing a [[biotic interchange]]) while Eurasia completely separates from North America, creating the [[North Atlantic Ocean]]. [[Maritime Southeast Asia]] diverges from the rest of Eurasia. First [[passerines]], [[ruminants]], [[pangolins]], [[bats]] and true [[primates]].

| style="background:{{period color|Ypresian}}" |{{Period start|ypresian}} {{Period start error|ypresian}}^*

| rowspan="3" style="background:{{period color|Paleocene}}" |[[Paleocene]]

| style="background:{{period color|Thanetian}}" |[[Thanetian]]

| rowspan="3" |Starts with [[Chicxulub impact]] and the [[K-Pg extinction event]], wiping out all non-avian dinosaurs and pterosaurs, most marine reptiles, many other vertebrates (e.g. many Laurasian metatherians), most cephalopods (only [[Nautilidae]] and [[Coleoidea]] survived) and many other invertebrates. [[Greenhouse and Icehouse Earth|Climate tropical]]. [[Mammals]] and [[birds]] (avians) diversify rapidly into a number of lineages following the extinction event (while the marine revolution stops). Multituberculates and the first [[rodents]] widespread. First large birds (e.g. [[ratites]] and [[terror birds]]) and mammals (up to bear or small hippo size). [[Alpine orogeny]] in Europe and Asia begins. First [[Proboscidea|proboscideans]] and [[plesiadapiformes]] (stem primates) appear. [[Australidelphia|Some marsupials]] migrate to Australia.

| style="background:{{period color|Thanetian}}" |{{Period start|thanetian}} {{Period start error|thanetian}}^*

| style="background:{{period color|Selandian}}" |[[Selandian]]

| style="background:{{period color|Selandian}}" |{{Period start|selandian}} {{Period start error|selandian}}^*

| style="background:{{period color|Danian}}" |[[Danian]]

| style="background:{{period color|Danian}}" |{{Period start|danian}} {{Period start error|danian}}^*

| rowspan="30" style="background:{{period color|Mesozoic}}" |[[Mesozoic]]

| rowspan="12" style="background:{{period color|Cretaceous}}" |[[Cretaceous]]

| rowspan="6" style="background:{{period color|Late Cretaceous}}" |[[Late Cretaceous|Upper/Late]]

| style="background:{{period color|Maastrichtian}}" |[[Maastrichtian]]

| rowspan="12" |[[Flowering plant|Flowering plants]] proliferate (after developing many features since the Carboniferous), along with new types of [[Insect|insects]], while other seed plants (gymnosperms and seed ferns) decline. More modern [[teleost]] fish begin to appear. [[Ammonoids]], [[Belemnoidea|belemnites]], [[rudist]] [[Bivalve|bivalves]], [[sea urchins]] and [[sponges]] all common. Many new types of [[Dinosaur|dinosaurs]] (e.g. [[Tyrannosauridae|tyrannosaurs]], [[Titanosauridae|titanosaurs]], [[Hadrosauridae|hadrosaurs]], and [[Ceratopsidae|ceratopsids]]) evolve on land, while [[Crocodilia|crocodilians]] appear in water and probably cause the last temnospondyls to die out; and [[Mosasaur|mosasaurs]] and modern types of sharks appear in the sea. The revolution started by marine reptiles and sharks reaches its peak, though ichthyosaurs vanish few million years after being heavily reduced at the [[Bonarelli Event]]. Toothed and [[Neornithes|toothless avian birds]] coexist with pterosaurs. Modern [[monotremes]], [[Metatheria|metatherian]] (including [[marsupials]], who migrate to South America) and [[Eutheria|eutherian]] (including [[placentals]], [[Leptictida|leptictidans]] and [[Cimolesta|cimolestans]]) mammals appear while the last non-mammalian cynodonts die out. First [[terrestrial crabs]]. Many snails become terrestrial. Further breakup of Gondwana creates [[South America]], [[Africa|Afro-]][[West Asia|Arabia]], [[Antarctica]], [[Oceania]], [[Madagascar]], [[Indian subcontinent|Greater India]], and the [[South Atlantic]], [[Indian Ocean|Indian]] and [[Antarctic Ocean|Antarctic Oceans]] and the islands of the Indian (and some of the Atlantic) Ocean. Beginning of [[Laramide Orogeny|Laramide]] and [[Sevier Orogeny|Sevier Orogenies]] of the [[Rocky Mountains]]. [[Atmosphere of Earth|Atmospheric]] oxygen and carbon dioxide levels similar to present day. [[Acritarch|Acritarchs]] disappear. Climate initially warm, but later it cools.

| style="background:{{period color|Maastrichtian}}" |{{Period start|maastrichtian}} {{Period start error|maastrichtian}}^*

| style="background:{{period color|Campanian}}" |[[Campanian]]

| style="background:{{period color|Campanian}}" |{{Period start|campanian}} {{Period start error|campanian}}

| style="background:{{period color|Santonian}}" |[[Santonian]]

| style="background:{{period color|Santonian}}" |{{Period start|santonian}} {{Period start error|santonian}}^*

| style="background:{{period color|Coniacian}}" |[[Coniacian]]

| style="background:{{period color|Coniacian}}" |{{Period start|coniacian}} {{Period start error|coniacian}}

| style="background:{{period color|Turonian}}" |[[Turonian]]

| style="background:{{period color|Turonian}}" |{{Period start|turonian}} {{Period start error|turonian}}^*

| style="background:{{period color|Cenomanian}}" |[[Cenomanian]]

| style="background:{{period color|Cenomanian}}" |{{Period start|cenomanian}} {{Period start error|cenomanian}}^*

| rowspan="6" style="background:{{period color|Early Cretaceous}}" |[[Early Cretaceous|Lower/Early]]

| style="background:{{period color|Albian}}" |[[Albian]]

| style="background:{{period color|Albian}}" |~{{Period start|albian}} {{Period start error|albian}}^*

| style="background:{{period color|Aptian}}" |[[Aptian]]

| style="background:{{period color|Aptian}}" |~{{Period start|aptian}} {{Period start error|aptian}}

| style="background:{{period color|Barremian}}" |[[Barremian]]

| style="background:{{period color|Barremian}}" |~{{Period start|barremian}} {{Period start error|barremian}}

| style="background:{{period color|Hauterivian}}" |[[Hauterivian]]

| style="background:{{period color|Hauterivian}}" |~{{Period start|hauterivian}} {{Period start error|hauterivian}}^*

| style="background:{{period color|Valanginian}}" |[[Valanginian]]

| style="background:{{period color|Valanginian}}" |~{{Period start|valanginian}} {{Period start error|valanginian}}

| style="background:{{period color|Berriasian}}" |[[Berriasian]]

| style="background:{{period color|Berriasian}}" |~{{Period start|berriasian}} {{Period start error|berriasian}}

| rowspan="11" style="background:{{period color|Jurassic}}" |[[Jurassic]]

| rowspan="3" style="background:{{period color|Late Jurassic}}" |[[Late Jurassic|Upper/Late]]

| style="background:{{period color|Tithonian}}" |[[Tithonian]]

| rowspan="11" |Climate becomes humid again. [[Gymnosperm|Gymnosperms]] (especially [[Conifer|conifers]], [[Cycad|cycads]] and [[cycadeoids]]) and [[Fern|ferns]] common. [[Dinosaur|Dinosaurs]], including [[Sauropod|sauropods]], [[Carnosaur|carnosaurs]], [[Stegosaur|stegosaurs]] and [[Coelurosaur|coelurosaurs]], become the dominant land vertebrates. Mammals diversify into [[Shuotheriidae|shuotheriids]], [[Australosphenida|australosphenidans]], [[eutriconodonts]], [[multituberculates]], [[symmetrodonts]], [[dryolestids]] and [[Boreosphenida|boreosphenidans]] but mostly remain small. First [[Avialae|birds]], [[Squamata|lizards, snakes]] and [[turtles]]. First [[brown algae]], [[Batoidea|rays]], [[shrimps]], [[crabs]] and [[lobsters]]. [[Parvipelvia|Parvipelvian]] ichthyosaurs and [[Plesiosaur|plesiosaurs]] diverse. Rhynchocephalians throughout the world. [[Bivalve|Bivalves]], [[Ammonoid|ammonoids]] and [[Belemnoidea|belemnites]] abundant. [[Sea urchin|Sea urchins]] very common, along with [[Crinoid|crinoids]], [[starfish]], [[Porifera|sponges]], and [[Terebratulida|terebratulid]] and [[Rhynchonellida|rhynchonellid]] [[Brachiopod|brachiopods]]. Breakup of [[Pangaea]] into [[Laurasia]] and [[Gondwana]], with the latter also breaking into two main parts; the [[Pacific]] and [[Arctic Ocean|Arctic Oceans]] form. [[Tethys Ocean]] forms. [[Nevadan orogeny]] in North America. [[Rangitata Orogeny|Rangitata]] and [[Cimmerian Orogeny|Cimmerian orogenies]] taper off. Atmospheric {{CO2}} levels 3&#x2013;4 times the present day levels (1200&#x2013;1500 ppmv, compared to today's 400 ppmv<ref name="Royer_2006" />{{efn|name="atmospheric-carbon-dioxide"|group=note}}). [[Crocodylomorph|Crocodylomorphs]] (last pseudosuchians) seek out an aquatic lifestyle. [[Mesozoic marine revolution]] continues from late Triassic. [[Tentaculita|Tentaculitans]] disappear.

| style="background:{{period color|Tithonian}}" |{{Period start|tithonian}} {{Period start error|tithonian}}

| style="background:{{period color|Kimmeridgian}}" |[[Kimmeridgian]]

| style="background:{{period color|Kimmeridgian}}" |{{Period start|kimmeridgian}} {{Period start error|kimmeridgian}}

| style="background:{{period color|Oxfordian}}" |[[Oxfordian stage|Oxfordian]]

| style="background:{{period color|Oxfordian}}" |{{Period start|oxfordian}} {{Period start error|oxfordian}}

| rowspan="4" style="background:{{period color|Middle Jurassic}}" |[[Middle Jurassic|Middle]]

| style="background:{{period color|Callovian}}" |[[Callovian]]

| style="background:{{period color|Callovian}}" |{{Period start|callovian}} {{Period start error|callovian}}

| style="background:{{period color|Bathonian}}" |[[Bathonian]]

| style="background:{{period color|Bathonian}}" |{{Period start|bathonian}} {{Period start error|bathonian}}^*

| style="background:{{period color|Bajocian}}" |[[Bajocian]]

| style="background:{{period color|Bajocian}}" |{{Period start|bajocian}} {{Period start error|bajocian}}^*

| style="background:{{period color|Aalenian}}" |[[Aalenian]]

| style="background:{{period color|Aalenian}}" |{{Period start|aalenian}} {{Period start error|aalenian}}^*

| rowspan="4" style="background:{{period color|Early Jurassic}}" |[[Early Jurassic|Lower/Early]]

| style="background:{{period color|Toarcian}}" |[[Toarcian]]

| style="background:{{period color|Toarcian}}" |{{Period start|toarcian}} {{Period start error|toarcian}}^*

| style="background:{{period color|Pliensbachian}}" |[[Pliensbachian]]

| style="background:{{period color|Pliensbachian}}" |{{Period start|pliensbachian}} {{Period start error|pleinsbachian}}^*

| style="background:{{period color|Sinemurian}}" |[[Sinemurian]]

| style="background:{{period color|Sinemurian}}" |{{Period start|sinemurian}} {{Period start error|sinemurian}}^*

| style="background:{{period color|Hettangian}}" |[[Hettangian]]

| style="background:{{period color|Hettangian}}" |{{Period start|hettangian}} {{Period start error|hettangian}}^*

| rowspan="7" style="background:{{period color|Triassic}}" |[[Triassic]]

| rowspan="3" style="background:{{period color|Late Triassic}}" |[[Late Triassic|Upper/Late]]

| style="background:{{period color|Rhaetian}}" |[[Rhaetian]]

| rowspan="7" |[[Archosaur|Archosaurs]] dominant on land as [[Pseudosuchia|pseudosuchians]] and in the air as [[Pterosaur|pterosaurs]]. [[Dinosaurs]] also arise from bipedal archosaurs. [[Ichthyosaur|Ichthyosaurs]] and [[Nothosaur|nothosaurs]] (a group of sauropterygians) dominate large marine fauna. [[Cynodont|Cynodonts]] become smaller and nocturnal, eventually becoming the first true [[mammals]], while other remaining synapsids die out. [[Rhynchosaur|Rhynchosaurs]] (archosaur relatives) also common. [[Seed ferns]] called ''[[Dicroidium]]'' remained common in Gondwana, before being replaced by advanced gymnosperms. Many large aquatic [[Temnospondyli|temnospondyl]] amphibians. [[Ceratitida|Ceratitidan]] [[ammonoids]] extremely common. [[Scleractinia|Modern corals]] and [[teleost]] fish appear, as do many modern [[insect]] orders and suborders. First [[starfish]]. [[Andes Mountains|Andean Orogeny]] in South America. [[Cimmerian Orogeny]] in Asia. [[Rangitata Orogeny]] begins in New Zealand. [[Hunter-Bowen Orogeny]] in [[Northern Australia]], Queensland and [[New South Wales]] ends, (c. 260&#x2013;225&nbsp;Ma). [[Carnian pluvial event]] occurs around 234-232 Ma, allowing the first dinosaurs and [[lepidosaurs]] (including [[Rhynchocephalia|rhynchocephalians]]) to radiate. [[Triassic-Jurassic extinction event]] occurs 201&nbsp;Ma, wiping out all [[conodonts]] and the [[Procolophonidae|last parareptiles]], many marine reptiles (e.g. all sauropterygians except [[plesiosaurs]] and all ichthyosaurs except [[Parvipelvia|parvipelvians]]), all [[Crocopoda|crocopodans]] except crocodylomorphs, pterosaurs, and dinosaurs, and many ammonoids (including the whole [[Ceratitida]]), bivalves, brachiopods, corals and sponges. First [[diatoms]].<ref name="Medlin_1997">{{cite journal |last1=Medlin |first1=L. K. |last2=Kooistra |first2=W. H. C. F. |last3=Gersonde |first3=R. |last4=Sims |first4=P. A. |last5=Wellbrock |first5=U. |year=1997 |title=Is the origin of the diatoms related to the end-Permian mass extinction? |journal=Nova Hedwigia |volume=65 |issue=1–4 |pages=1–11 |doi=10.1127/nova.hedwigia/65/1997/1 |hdl=10013/epic.12689}}</ref>

| style="background:{{period color|Rhaetian}}" |~{{Period start|rhaetian}} {{Period start error|rhaetian}}

| style="background:{{period color|Norian}}" |[[Norian]]

| style="background:{{period color|Norian}}" |~{{Period start|norian}} {{Period start error|norian}}

| style="background:{{period color|Carnian}}" |[[Carnian]]

| style="background:{{period color|Carnian}}" |~{{Period start|carnian}} {{Period start error|carnian}}^*

| rowspan="2" style="background:{{period color|Middle Triassic}}" |[[Middle Triassic|Middle]]

| style="background:{{period color|Ladinian}}" |[[Ladinian]]

| style="background:{{period color|Ladinian}}" |~{{Period start|ladinian}} {{Period start error|ladnian}}^*

| style="background:{{period color|Anisian}}" |[[Anisian]]

| style="background:{{period color|Anisian}}" |{{Period start|anisian}} {{Period start error|anisian}}

| rowspan="2" style="background:{{period color|Early Triassic}}" |[[Early Triassic|Lower/Early]]

| style="background:{{period color|Olenekian}}" |[[Olenekian]]

| style="background:{{period color|Olenekian}}" |{{Period start|olenekian}} {{Period start error|olenekian}}

| style="background:{{period color|Induan}}" |[[Induan]]

| style="background:{{period color|Induan}}" |{{Period start|induan}} {{Period start error|induan}}^*

| rowspan="48" style="background:{{period color|Paleozoic}}" |[[Paleozoic]]

| rowspan="9" style="background:{{period color|Permian}}" |[[Permian]]

| rowspan="2" style="background:{{period color|Lopingian}}" |[[Lopingian]]

| style="background:{{period color|Changhsingian}}" |[[Changhsingian]]

| rowspan="9" |[[Landmass|Landmasses]] unite into [[supercontinent]] [[Pangaea]], creating the [[Urals]], [[Ouachitas]] and [[Appalachian Mountains|Appalachians]], among other mountain ranges (the superocean [[Panthalassa]] or Proto-Pacific also forms). End of Permo-Carboniferous glaciation. Hot and dry climate. A possible drop in oxygen levels. [[Synapsida|Synapsids]] ([[Pelycosaur|pelycosaurs]] and [[Therapsid|therapsids]]) become widespread and dominant, while [[Parareptile|parareptiles]] and [[Temnospondyli|temnospondyl]] [[Amphibian|amphibians]] remain common, with the latter probably giving rise to [[Lissamphibia|modern amphibians]] in this period. In the mid-Permian, lycophytes are heavily replaced by ferns and seed plants. [[Beetles]] and [[Fly|flies]] evolve. The very large arthropods and non-tetrapod tetrapodomorphs go extinct. Marine life flourishes in warm shallow reefs; [[Productida|productid]] and [[Spiriferida|spiriferid]] brachiopods, bivalves, [[Foram|forams]], ammonoids (including goniatites), and [[Orthocerida|orthoceridans]] all abundant. [[Sauria|Crown reptiles]] arise from earlier diapsids, and split into the ancestors of [[Lepidosauromorpha|lepidosaurs]], [[Kuehneosauridae|kuehneosaurids]], [[Choristodera|choristoderes]], [[Crocopoda|archosaurs]], [[Testudinata|testudinatans]], [[Ichthyosauromorpha|ichthyosaurs]], [[thalattosaurs]], and [[Sauropterygia|sauropterygians]]. Cynodonts evolve from larger therapsids. [[Olson's Extinction]] (273 Ma), [[Capitanian mass extinction event|End-Capitanian extinction]] (260 Ma), and [[Permian-Triassic extinction event]] (252 Ma) occur one after another: more than 80% of life on Earth becomes extinct in the lattermost, including most [[Retaria|retarian]] plankton, corals ([[Tabulata]] and [[Rugosa]] die out fully), brachiopods, bryozoans, gastropods, ammonoids (the goniatites die off fully), insects, parareptiles, synapsids, amphibians, and crinoids (only [[Articulata (Crinoidea)|articulates]] survived), and all [[Eurypterid|eurypterids]], [[Trilobite|trilobites]], [[Graptolite|graptolites]], [[hyoliths]], [[Edrioasteroidea|edrioasteroid crinozoans]], [[Blastoid|blastoids]] and [[acanthodians]]. [[Ouachita Orogeny|Ouachita]] and [[Innuitian orogeny|Innuitian orogenies]] in North America. [[Uralian orogeny]] in Europe/Asia tapers off. [[Altai Mountains|Altaid]] orogeny in Asia. [[Hunter-Bowen Orogeny]] on [[Australia (continent)|Australian continent]] begins (c. 260&#x2013;225&nbsp;Ma), forming the [[MacDonnell Ranges]].

| style="background:{{period color|Changhsingian}}" |{{Period start|changhsingian}} {{Period start error|changhsingian}}^*

| style="background:{{period color|Wuchiapingian}}" |[[Wuchiapingian]]

| style="background:{{period color|Wuchiapingian}}" |{{Period start|wuchiapingian}} {{Period start error|wuchiapingian}}^*

| rowspan="3" style="background:{{period color|Guadalupian}}" |[[Guadalupian]]

| style="background:{{period color|Capitanian}}" |[[Capitanian]]

| style="background:{{period color|Capitanian}}" |{{Period start|capitanian}} {{Period start error|capitanian}}^*

| style="background:{{period color|Wordian}}" |[[Wordian]]

| style="background:{{period color|Wordian}}" |{{Period start|wordian}} {{Period start error|wordian}}^*

| style="background:{{period color|Roadian}}" |[[Roadian]]

| style="background:{{period color|Roadian}}" |{{Period start|roadian}} {{Period start error|roadian}}^*

| rowspan="4" style="background:{{period color|Cisuralian}}" |[[Cisuralian]]

| style="background:{{period color|Kungurian}}" |[[Kungurian]]

| style="background:{{period color|Kungurian}}" |{{Period start|kungurian}} {{Period start error|kungurian}}

| style="background:{{period color|Artinskian}}" |[[Artinskian]]

| style="background:{{period color|Artinskian}}" |{{Period start|artinskian}} {{Period start error|artinskian}}^*

| style="background:{{period color|Sakmarian}}" |[[Sakmarian]]

| style="background:{{period color|Sakmarian}}" |{{Period start|sakmarian}} {{Period start error|sakmarian}}^*

| style="background:{{period color|Asselian}}" |[[Asselian]]

| style="background:{{period color|Asselian}}" |{{Period start|asselian}} {{Period start error|asselian}}^*

| rowspan="7" style="background:{{period color|Carboniferous}}" |[[Carboniferous]]<br/>{{efn|The [[Mississippian (geology)|Mississippian]] and [[Pennsylvanian (geology)|Pennsylvanian]] are official sub-systems/sub-periods.|name=CarboSub|group=note}}

| rowspan="4" style="background:{{period color|Pennsylvanian}}" |[[Pennsylvanian (geology)|Pennsylvanian]]<br/>{{efn|group=note|name=MissiPenns|This is divided into Lower/Early, Middle, and Upper/Late series/epochs}}

| style="background:{{period color|Gzhelian}}" |[[Gzhelian]]

| rowspan="4" |[[Pterygota|Winged insects]] radiate suddenly; some (esp. [[Protodonata]] and [[Palaeodictyoptera]]) of them as well some [[Millipede|millipedes]] and [[Scorpion|scorpions]] become very large. First [[coal]] forests ([[Lepidodendron|scale trees]], ferns, [[Sigillaria|club trees]], [[Calamites|giant horsetails]], ''[[Cordaites]]'', etc.). Higher [[Atmosphere of Earth|atmospheric]] [[oxygen]] levels. [[Permo-Carboniferous|Ice Age]] continues to the Early Permian. [[Goniatite|Goniatites]], brachiopods, bryozoa, bivalves, and corals plentiful in the seas and oceans. First [[woodlice]]. Testate [[Foram|forams]] proliferate. [[Euramerica]] collides with [[Gondwana]] and Siberia-Kazakhstania, the latter of which forms [[Laurasia]] and the [[Uralian orogeny]]. Variscan orogeny continues (these collisions created orogenies, and ultimately [[Pangaea]]). [[Amphibian|Amphibians]] (e.g. temnospondyls) spread in Euramerica, with some becoming the first [[amniotes]]. [[Carboniferous Rainforest Collapse]] occurs, initiating a dry climate which favors amniotes over amphibians. Amniotes diversify rapidly into [[synapsids]], [[parareptiles]], [[Captorhinidae|cotylosaurs]], [[protorothyridids]] and [[diapsids]]. [[Rhizodont|Rhizodonts]] remained common before they died out by the end of the period. First [[sharks]].

| style="background:{{period color|Gzhelian}}" |{{Period start|gzhelian}} {{Period start error|gzhelain}}

| style="background:{{period color|Kasimovian}}" |[[Kasimovian]]

| style="background:{{period color|Kasimovian}}" |{{Period start|kasimovian}} {{Period start error|kasimovian}}

| style="background:{{period color|Moscovian}}" |[[Moscovian (Carboniferous)|Moscovian]]

| style="background:{{period color|Moscovian}}" |{{Period start|moscovian}} {{Period start error|moscovian}}

| style="background:{{period color|Bashkirian}}" |[[Bashkirian]]

| style="background:{{period color|Bashkirian}}" |{{Period start|bashkirian}} {{Period start error|bashkrian}}^*

| rowspan="3" style="background:{{period color|Mississippian}}" |[[Mississippian (geology)|Mississippian]]<br/>{{efn|group=note|name=MissiPenns}}

| style="background:{{period color|Serpukhovian}}" |[[Serpukhovian]]

| rowspan="3" |Large [[Lycopodiophyta|lycopodian primitive trees]] flourish and amphibious [[Eurypterid|eurypterids]] live amid [[coal]]-forming coastal [[Brackish water|swamps]], radiating significantly one last time. First [[gymnosperms]]. First [[Holometabola|holometabolous]], [[Paraneoptera|paraneopteran]], [[Polyneoptera|polyneopteran]], [[Odonatoptera|odonatopteran]] and [[Ephemeroptera|ephemeropteran]] insects and first [[barnacles]]. First five-digited [[tetrapods]] (amphibians) and [[land snails]]. In the oceans, [[Bony fish|bony]] and [[Chondrichthyes|cartilaginous fishes]] are dominant and diverse; [[Echinoderm|echinoderms]] (especially [[Crinoid|crinoids]] and [[Blastoid|blastoids]]) abundant. [[Coral|Corals]], [[Bryozoa|bryozoans]], [[Orthocerida|orthoceridans]], [[Goniatite|goniatites]] and brachiopods ([[Productida]], [[Spiriferida]], etc.) recover and become very common again, but [[Trilobita|trilobites]] and [[Nautiloid|nautiloids]] decline. [[Karoo Ice Age|Glaciation]] in East [[Gondwana]] continues from Late Devonian. [[Mayor Island/Tuhua|Tuhua Orogeny]] in New Zealand tapers off. Some lobe finned fish called rhizodonts become abundant and dominant in freshwaters. [[Siberia (continent)|Siberia]] collides with a different small continent, [[Kazakhstania]].

| style="background:{{period color|Serpukhovian}}" |{{Period start|serpukhovian}} {{Period start error|serpukhovian}}

| style="background:{{period color|visean}}" |[[Viséan]]

| style="background:{{period color|visean}}" |{{Period start|visean}} {{Period start error|visean}}^*

| style="background:{{period color|Tournaisian}}" |[[Tournaisian]]