View source for Geologic time scale

{{Short description|System that relates geologic strata to time}}
{{Use dmy dates|date=July 2016}}
{{Use British English|date=October 2023}}
<!--Use |group=note for {efn}}-->
[[File:Geologic time scale - spiral - ICS colours (light) - path text.svg|upright=1.35|alt=Geologic time scale proportionally represented as a log-spiral. The image also shows some notable events in Earth's history and the general evolution of life.|thumb|The geologic time scale, proportionally represented as a [[Logarithmic spiral|log-spiral]] with some major events in Earth's history. A [[megaannus]] (Ma) represents one million (10<sup>6</sup>) years.]]

The '''geologic time scale''' or '''geological 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]] (a scientific branch of [[geology]] that aims to determine the age of rocks). It is used primarily by [[Earth science|Earth scientists]] (including [[geologist]]s, [[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]]s. The definition of standardised international units of geological 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=Statues & Guidelines |url=https://stratigraphy.org/statutes |access-date=2022-04-05 |website= |publisher=International Commission on Stratigraphy}}</ref> is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC){{ref icc}} that are used to define divisions of geological time. The chronostratigraphic divisions are in turn used to define geochronologic units.<ref name="ICS" />

== 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 through [[History of Earth|Earth's history]], a time span of about [[Age of Earth|4.54&nbsp;±&nbsp;0.05&nbsp;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 organises 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 ([[Global Standard Stratigraphic Age]]s, 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 |last1=Shields |first1=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 |journal=Journal of the Geological Society |language=en |volume=179 |issue=1 |pages=jgs2020–222 |doi=10.1144/jgs2020-222 |bibcode=2022JGSoc.179..222S |s2cid=236285974 |issn=0016-7649|doi-access=free }}</ref><ref name="GTS2012_Precambrian">{{Citation |last1=Van Kranendonk |first1=Martin J. |title=A Chronostratigraphic Division of the Precambrian |date=2012 |work=The Geologic Time Scale |pages=299–392 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780444594259000160 |access-date=2022-04-05 |publisher=Elsevier |language=en |doi=10.1016/b978-0-444-59425-9.00016-0 |isbn=978-0-444-59425-9 |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>

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 standardising 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 International Chronostratigraphic Chart represents this ongoing effort.

Several key principles are used to determine the relative relationships of rocks and thus their chronostratigraphic position.<ref name="ICS_chronostratigraphic_units">{{Cite web |title=International Commission on Stratigraphy - Stratigraphic Guide - Chapter 9. Chronostratigraphic Units |url=https://stratigraphy.org/guide/chron |access-date=2024-04-16 |website=stratigraphy.org}}</ref><ref name="Boggs-2011">{{Cite book |last=Boggs |first=Sam |title=Principles of sedimentology and stratigraphy |date=2011 |publisher=Prentice Hall |isbn=978-0-321-74576-7 |edition=5th |location=Boston, Munich}}</ref>

The [[law of superposition]] that states that in undeformed stratigraphic sequences the oldest strata will lie at the bottom of the sequence, while newer material stacks upon the surface.<ref name="Steno_1669" /><ref name="Hutton_1795v1" /><ref name="Lyell_1832v1" /><ref name="Boggs-2011" /> In practice, this means a younger rock will lie on top of an older rock unless there is evidence to suggest otherwise.

The [[principle of original horizontality]] that states layers of sediments will originally be deposited horizontally under the action of gravity.<ref name="Steno_1669" /><ref name="Lyell_1832v1" /><ref name="Boggs-2011" /> However, it is now known that not all sedimentary layers are deposited purely horizontally,<ref name="Boggs-2011" /><ref name=Mehta_et_al_1994>{{Cite journal |last1=Mehta |first1=A |last2=Barker |first2=G C |date=1994-04-01 |title=The dynamics of sand |url=https://iopscience.iop.org/article/10.1088/0034-4885/57/4/002 |journal=Reports on Progress in Physics |volume=57 |issue=4 |pages=383–416 |doi=10.1088/0034-4885/57/4/002 |bibcode=1994RPPh...57..383M |issn=0034-4885}}</ref> but this principle is still a useful concept.

The [[principle of lateral continuity]] that states layers of sediments extend laterally in all directions until either thinning out or being cut off by a different rock layer, i.e. they are laterally continuous.<ref name="Steno_1669" /> Layers do not extend indefinitely; their limits are controlled by the amount and type of sediment in a [[sedimentary basin]], and the geometry of that basin.

The principle of [[cross-cutting relationships]] that states a rock that cuts across another rock must be younger than the rock it cuts across.<ref name="Steno_1669" /><ref name="Hutton_1795v1" /><ref name="Lyell_1832v1" /><ref name="Boggs-2011" />

The [[law of included fragments]] that states small fragments of one type of rock that are embedded in a second type of rock must have formed first, and were included when the second rock was forming.<ref name="Lyell_1832v1" /><ref name="Boggs-2011" />

The relationships of [[unconformity|unconformities]] which are geologic features representing a gap in the geologic record. Unconformities are formed during periods of erosion or non-deposition, indicating non-continuous sediment deposition.<ref name="Boggs-2011" /> Observing the type and relationships of unconformities in strata allows geologist to understand the relative timing of the strata.

The [[principle of faunal succession]] (where applicable) that states rock strata contain distinctive sets of fossils that succeed each other vertically in a specific and reliable order.<ref name="Smith_1816">{{Cite book |last=Smith |first=William |url=http://www.biodiversitylibrary.org/bibliography/106808 |title=Strata identified by organized fossils, containing prints on colored paper of the most characteristic specimens in each stratum |date=1816-06-01 |publisher=W. Arding |location=London |doi=10.5962/bhl.title.106808}}</ref><ref name="Boggs-2011" /> This allows for a correlation of strata even when the horizon between them is not continuous.

== Divisions of geologic time ==
{{See also|Stratigraphy|Chronostratigraphy|Biostratigraphy|Magnetostratigraphy|Lithostratigraphy|Geochronology}}
The geologic time scale is divided into chronostratigraphic units and their corresponding geochronologic units.

* An '''{{visible anchor|eon}}''' is the largest geochronologic time unit and is equivalent to a chronostratigraphic [[eonothem]].<ref name="dictionary_of_geology_2020">{{Cite book |title=A dictionary of geology and earth sciences |date=2020 |author=Michael Allaby |isbn=978-0-19-187490-1 |edition=Fifth |location=Oxford |oclc=1137380460}}</ref> There are four formally defined eons: the [[Hadean]], [[Archean]], [[Proterozoic]] and [[Phanerozoic]].<ref name="ICS" />
* An '''{{visible anchor|era}}''' is the second largest geochronologic time unit and is equivalent to a chronostratigraphic [[erathem]].<ref name="ICS_chronostrat" /><ref name="dictionary_of_geology_2020" /> There are ten defined eras: the [[Eoarchean]], [[Paleoarchean]], [[Mesoarchean]], [[Neoarchean]], [[Paleoproterozoic]], [[Mesoproterozoic]], [[Neoproterozoic]], [[Paleozoic]], [[Mesozoic]] and [[Cenozoic]], with none from the Hadean eon.<ref name="ICS" />
* A '''{{visible anchor|period}}''' is equivalent to a chronostratigraphic [[system (stratigraphy)|system]].<ref name="ICS_chronostrat" /><ref name="dictionary_of_geology_2020" /> There are 22 defined periods, with the current being the [[Quaternary]] period.<ref name="ICS" /> As an exception, two subperiods are used for the [[Carboniferous|Carboniferous Period]].<ref name="ICS_chronostrat" />
* An '''{{visible anchor|epoch}}''' is the second smallest geochronologic unit. It is equivalent to a chronostratigraphic [[series (stratigraphy)|series]].<ref name="ICS_chronostrat" /><ref name="dictionary_of_geology_2020" /> There are 37 defined epochs and one informal one. The current epoch is the [[Holocene]]. There are also 11 subepochs which are all within the [[Neogene]] and Quaternary.<ref name="ICS" /> The use of subepochs as formal units in international chronostratigraphy was ratified in 2022.<ref name="Aubry_2022_subseries">{{Cite journal |last1=Aubry |first1=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 |journal=Episodes |language=en |volume=45 |issue=1 |pages=97–99 |doi=10.18814/epiiugs/2021/021016 |s2cid=240772165 |issn=0705-3797|doi-access=free }}</ref>
* An '''{{visible anchor|age}}''' is the smallest hierarchical geochronologic unit. It is equivalent to a chronostratigraphic [[stage (stratigraphy)|stage]].<ref name="ICS_chronostrat" /><ref name="dictionary_of_geology_2020" /> There are 96 formal and five informal ages.<ref name="ICS" /> The current age is the [[Meghalayan]].
* A ''{{visible anchor|chron}}'' is a non-hierarchical formal geochronology unit of unspecified rank and is equivalent to 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.

{| class="wikitable mw-collapsible"
|+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 million years to two billion 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 of years to millions of years
|}

The subdivisions {{em|Early}} and {{em|Late}} are used as the geochronologic equivalents of the chronostratigraphic {{em|Lower}} and {{em|Upper}}, e.g., Early [[Triassic]] Period (geochronologic unit) is used in place of Lower Triassic System (chronostratigraphic unit).

Rocks representing a given chronostratigraphic unit are that chronostratigraphic unit, and the time they were laid down in is the geochronologic unit, e.g., the rocks that represent the [[Silurian]] System {{em|are}} the Silurian System and they were deposited {{em|during}} the Silurian Period. This definition means the numeric age of a geochronologic unit can be changed (and is more often subject to change) when refined by geochronometry while the equivalent chronostratigraphic unit (the revision of which is less frequent) remains unchanged. 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 been changed; rather, the absolute age has merely been refined.

=== Terminology ===

{{em|[[Chronostratigraphy]]}} 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}}'''{{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. Eonothem, erathem, system, series, subseries, stage, and substage are the hierarchical chronostratigraphic units.<ref name="ICS_chronostrat"/><!-- this citation cites two previous sentences -->

A '''{{em|geochronologic unit}}'''{{Anchor|Geochronologic unit}} is a subdivision of geologic time. It is a numeric representation of an intangible property (time).<ref name="ICS_definitions">{{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> These units are arranged in a hierarchy: eon, era, period, epoch, subepoch, age, and subage.<ref name="ICS_chronostrat" /> 
{{em|Geochronology}} 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]]s). 
{{em|[[Geochronometry]]}} is the field of geochronology that numerically quantifies geologic time.<ref name="ICS_definitions"/> <!-- this citation cites two previous sentences -->

A {{em|[[Global Boundary Stratotype Section and Point]]}} (GSSP) is an internationally agreed-upon reference point on a [[stratigraphic section]] that 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 |last1=Knoll |first1=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|bibcode=2006Letha..39...13K }}</ref>

A {{em|[[Global Standard Stratigraphic Age]]}} (GSSA)<ref name="Remane_1996_GSSP">{{Cite journal |last1=Remane |first1=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) |journal=Episodes |language=en |volume=19 |issue=3 |pages=77–81 |doi=10.18814/epiiugs/1996/v19i3/007 |issn=0705-3797|doi-access=free }}</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 standard international units of the geologic time scale are published by the International Commission on Stratigraphy on the International Chronostratigraphic Chart. However, regional terms are still in use in some areas. The numeric values on the International Chronostratigrahpic Chart are represented by the unit [[Megaannum|Ma]] (megaannum, for 'million [[year]]s'). For example, {{Period start|Jurassic}} {{Period start error|Jurassic}} Ma, the lower boundary of the [[Jurassic]] Period, is defined as 201,400,000 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]]).

== 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 in 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 International Commission on Stratigraphy 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 [[Precambrian]] or pre-Cambrian (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 geologic eonothem/eon names
!Name
!Time span
!Duration (million years)
!Etymology of name
|-
|[[Phanerozoic]]
|{{Period span/brief|Phanerozoic|1}}
|{{#expr:{{Period start|Phanerozoic}}-{{Period end|Phanerozoic}}}}
|From Greek φανερός (''phanerós'') 'visible' or 'abundant' and ζωή (''zoē'') 'life'.
|-
|[[Proterozoic]]
|{{Period span/brief|Proterozoic|1}}
|{{#expr:{{Period start|Proterozoic}}-{{Period end|Proterozoic}}}}
|From Greek πρότερος (''próteros'') 'former' or 'earlier' and ζωή (''zoē'') 'life'.
|-
|[[Archean]]
|{{Period span/brief|Archean|1}}
|{{#expr:{{Period start|Archean}}-{{Period end|Archean}}}}
|From Greek [[ἀρχή]] (''archē'') 'beginning, origin'.
|-
|[[Hadean]]
|{{Period span/brief|Hadean|1}}
|{{#expr:{{Period start|Hadean}}-{{Period end|Hadean}}}}
|From [[Hades]], {{langx|grc|ᾍδης|Háidēs}}, the god of the underworld (hell, the inferno) in Greek mythology.
|}
{| class="wikitable mw-collapsible" style = "margin-left: auto; margin-right: auto; border: none;"
|+Time span and etymology of geologic erathem/era names
!Name
!Time span
!Duration (million years)
!Etymology of name
|-
|[[Cenozoic]]
|{{Period span/brief|Cenozoic|1}}
|{{#expr:{{Period start|Cenozoic}}-{{Period end|Cenozoic}}}}
|From Greek καινός (''kainós'') 'new' and ζωή (''zōḗ'') 'life'.
|-
|[[Mesozoic]]
|{{Period span/brief|Mesozoic|1}}
|{{#expr:{{Period start|Mesozoic}}-{{Period end|Mesozoic}}}}
|From Greek μέσο (''méso'') 'middle' and ζωή (''zōḗ'') 'life'.
|-
|[[Paleozoic]]
|{{Period span/brief|Paleozoic|1}}
|{{#expr:{{Period start|Paleozoic}}-{{Period end|Paleozoic}}}}
|From Greek παλιός (''palaiós'') 'old' and ζωή (''zōḗ'') 'life'.
|-
|[[Neoproterozoic]]
|{{Period span/brief|Neoproterozoic|1}}
|{{#expr:{{Period start|Neoproterozoic}}-{{Period end|Neoproterozoic}}}}
|From Greek νέος (''néos'') 'new' or 'young', πρότερος (''próteros'') 'former' or 'earlier', and ζωή (''zōḗ'') 'life'.
|-
|[[Mesoproterozoic]]
|{{Period span/brief|Mesoproterozoic|1}}
|{{#expr:{{Period start|Mesoproterozoic}}-{{Period end|Mesoproterozoic}}}}
|From Greek μέσο (''méso'') 'middle', πρότερος (''próteros'') 'former' or 'earlier', and ζωή (''zōḗ'') 'life'.
|-
|[[Paleoproterozoic]]
|{{Period span/brief|Paleoproterozoic|1}}
|{{#expr:{{Period start|Paleoproterozoic}}-{{Period end|Paleoproterozoic}}}}
|From Greek παλιός (''palaiós'') 'old', πρότερος (''próteros'') 'former' or 'earlier', and ζωή (''zōḗ'') 'life'.
|-
|[[Neoarchean]]
|{{Period span/brief|Neoarchean|1}}
|{{#expr:{{Period start|Neoarchean}}-{{Period end|Neoarchean}}}}
|From Greek νέος (''néos'') 'new' or 'young' and ἀρχαῖος (''arkhaîos'') 'ancient'.
|-
|[[Mesoarchean]]
|{{Period span/brief|Mesoarchean|1}}
|{{#expr:{{Period start|Mesoarchean}}-{{Period end|Mesoarchean}}}}
|From Greek μέσο (''méso'') 'middle' and ἀρχαῖος (''arkhaîos'') 'ancient'.
|-
|[[Paleoarchean]]
|{{Period span/brief|Paleoarchean|1}}
|{{#expr:{{Period start|Paleoarchean}}-{{Period end|Paleoarchean}}}}
|From Greek παλιός (''palaiós'') 'old' and ἀρχαῖος (''arkhaîos'') 'ancient'.
|-
|[[Eoarchean]]
|{{Period span/brief|Eoarchean|1}}
|{{#expr:{{Period start|Eoarchean}}-{{Period end|Eoarchean}}}}
|From Greek ἠώς (''ēōs'') 'dawn' and ἀρχαῖος (''arkhaîos'') 'ancient'.
|}
{| class="wikitable mw-collapsible" style = "margin-left: auto; margin-right: auto; border: none;"
|+Time span and etymology of geologic system/period names
!Name
!Time span
!Duration (million years)
!Etymology of name
|-
|[[Quaternary]]
|{{Period span/brief|Quaternary|1}}
|{{#expr:{{Period start|Quaternary}}-{{Period end|Quaternary}}}}
|First introduced by [[Jules Desnoyers]] in 1829 for sediments in [[France]]'s [[Seine]] Basin that appeared to be younger than [[Tertiary (period)|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.<ref name="Head_etal_2008">{{Cite journal |last1=Head |first1=Martin J. |last2=Gibbard |first2=Philip |last3=Salvador |first3=Amos |date=2008-06-01 |title=The Quaternary: its character and definition |journal=Episodes |language=en |volume=31 |issue=2 |pages=234–238 |doi=10.18814/epiiugs/2008/v31i2/009 |doi-access=free |issn=0705-3797}}</ref><ref name ="Gibbard_etal_2010">{{Cite journal |last1=Gibbard |first1=Philip L. |last2=Head |first2=Martin J. |last3=Walker |first3=Michael J. C. |last4=the Subcommission on Quaternary Stratigraphy |date=2010-01-20 |title=Formal ratification of the Quaternary System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma |url=https://onlinelibrary.wiley.com/doi/10.1002/jqs.1338 |journal=Journal of Quaternary Science |language=en |volume=25 |issue=2 |pages=96–102 |doi=10.1002/jqs.1338 |bibcode=2010JQS....25...96G |issn=0267-8179}}</ref>|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]]
|{{Period span/brief|Neogene|1}}
|{{#expr:{{Period start|Neogene}}-{{Period end|Neogene}}}}
|Derived from Greek νέος (''néos'') 'new' and γενεά (''geneá'') 'genesis' or 'birth'.
|-
|[[Paleogene]]
|{{Period span/brief|Paleogene|1}}
|{{#expr:{{Period start|Paleogene}}-{{Period end|Paleogene}}}}
|Derived from Greek παλιός (''palaiós'') 'old' and γενεά (''geneá'') 'genesis' or 'birth'.
|-
|[[Cretaceous]]
|[[Tilde#Common use in English|~]]{{Period span/brief|Cretaceous|1}}
|~{{#expr:{{Period start|Cretaceous}}-{{Period end|Cretaceous}}}}
|Derived from ''Terrain Crétacé'' 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 [[Latin]] ''crēta'' 'chalk'.
|-
|[[Jurassic]]
|{{Period span/brief|Jurassic|1}}
|~{{#expr:{{Period start|Jurassic}}-{{Period end|Jurassic}}}}
|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.com/books?id=oZ5PAAAAcAAJ |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 |last1=Ogg |first1=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}}
|{{#expr:{{Period start|Triassic}}-{{Period end|Triassic}}}}
|From the ''Trias'' of [[Friedrich August von Alberti]] in reference to a trio of formations widespread in southern [[Germany]].
|-
|[[Permian]]
|{{Period span/brief|Permian|1}}
|{{#expr:{{Period start|Permian}}-{{Period end|Permian}}}}
|Named after the historical region of [[Perm Governorate|Perm]], [[Russian Empire]].<ref name="Murchison_1842">{{Cite book |last1=Murchison |url=https://books.google.com/books?id=MDoAAAAAQAAJ |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}}
|{{#expr:{{Period start|Carboniferous}}-{{Period end|Carboniferous}}}}
|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/books?id=-7-ZqIkYBOMC&pg=PA1 |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}}
|{{#expr:{{Period start|Devonian}}-{{Period end|Devonian}}}}
|Named after [[Devon]], England.<ref name="Sedgwick_1840">{{Cite journal |last1=Sedgwick |first1=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 |s2cid=128475487 |issn=2042-5295}}</ref>
|-
|[[Silurian]]
|{{Period span/brief|Silurian|1}}
|{{#expr:{{Period start|Silurian}}-{{Period end|Silurian}}}}
|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}}
|{{#expr:{{Period start|Ordovician}}-{{Period end|Ordovician}}}}
|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 |bibcode=1879GeoM....6....1L |s2cid=129165105 |issn=0016-7568}}</ref><ref>{{Cite journal |last=Bassett |first=Michael G. |title=100 Years of Ordovician Geology |date=1979-06-01 |journal=Episodes |language=en |volume=2 |issue=2 |pages=18–21 |doi=10.18814/epiiugs/1979/v2i2/003 |issn=0705-3797|doi-access=free }}</ref>
|-
|[[Cambrian]]
|{{Period span/brief|Cambrian|1}}
|{{#expr:{{Period start|Cambrian}}-{{Period end|Cambrian}}}}
|Named for [[Cambria]], a [[Latin]]ised form of the Welsh name for [[Wales]], ''Cymru''.<ref>{{cite EB1911|wstitle=Cambria}}</ref>
|-
|[[Ediacaran]]
|{{Period span/brief|Ediacaran|1}}
|~{{#expr:{{Period start|Ediacaran}}-{{Period end|Ediacaran}}}}
|Named for the [[Ediacara Hills]]. Ediacara is possibly a corruption of [[Kuyani]] 'Yata Takarra' '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 |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 }}</ref>
|-
|[[Cryogenian]]
|{{Period span/brief|Cryogenian|1}}
|~{{#expr:{{Period start|Cryogenian}}-{{Period end|Cryogenian}}}}
|From Greek κρύος (''krýos'') 'cold' and γένεσις (''génesis'') 'birth'.<ref name="GTS2012_Precambrian" />
|-
|[[Tonian]]
|{{Period span/brief|Tonian|1}}
|~{{#expr:{{Period start|Tonian}}-{{Period end|Tonian}}}}
|From Greek τόνος (''tónos'') 'stretch'.<ref name="GTS2012_Precambrian" />
|-
|[[Stenian]]
|{{Period span/brief|Stenian|1}}
|{{#expr:{{Period start|Stenian}}-{{Period end|Stenian}}}}
|From Greek στενός (''stenós'') 'narrow'.<ref name="GTS2012_Precambrian" />
|-
|[[Ectasian]]
|{{Period span/brief|Ectasian|1}}
|{{#expr:{{Period start|Ectasian}}-{{Period end|Ectasian}}}}
|From Greek ἔκτᾰσῐς (''éktasis'') 'extension'.<ref name="GTS2012_Precambrian" />
|-
|[[Calymmian]]
|{{Period span/brief|Calymmian|1}}
|{{#expr:{{Period start|Calymmian}}-{{Period end|Calymmian}}}}
|From Greek κάλυμμᾰ (''kálumma'') 'cover'.<ref name="GTS2012_Precambrian" />
|-
|[[Statherian]]
|{{Period span/brief|Statherian|1}}
|{{#expr:{{Period start|Statherian}}-{{Period end|Statherian}}}}
|From Greek σταθερός (''statherós'') 'stable'.<ref name="GTS2012_Precambrian" />
|-
|[[Orosirian]]
|{{Period span/brief|Orosirian|1}}
|{{#expr:{{Period start|Orosirian}}-{{Period end|Orosirian}}}}
|From Greek ὀροσειρά (''oroseirá'') 'mountain range'.<ref name="GTS2012_Precambrian" />
|-
|[[Rhyacian]]
|{{Period span/brief|Rhyacian|1}}
|{{#expr:{{Period start|Rhyacian}}-{{Period end|Rhyacian}}}}
|From Greek ῥύαξ (''rhýax'') 'stream of lava'.<ref name="GTS2012_Precambrian" />
|-
|[[Siderian]]
|{{Period span/brief|Siderian|1}}
|{{#expr:{{Period start|Siderian}}-{{Period end|Siderian}}}}
|From Greek σίδηρος (''sídēros'') '[[iron]]'.<ref name="GTS2012_Precambrian" />
|}
{| class="wikitable mw-collapsible" style = "margin-left: auto; margin-right: auto; border: none;"
|+Time span and etymology of geologic series/epoch names
!Name
!Time span
!Duration (million years)
!Etymology of name
|-
|[[Holocene]]
|{{Period span/brief|Holocene|3}}
|{{#expr:{{Period start|Holocene}}-{{Period end|Holocene}}}}
|From Greek ὅλος (''hólos'') 'whole' and καινός (''kainós'') 'new'
|-
|[[Pleistocene]]
|{{Period span/brief|Pleistocene|3}}
|{{#expr:{{Period start|Pleistocene}}-{{Period end|Pleistocene}}}}
|Coined in the early 1830s from Greek πλεῖστος (''pleîstos'') 'most' and καινός (''kainós'') 'new'
|-
|[[Pliocene]]
|{{Period span/brief|Pliocene|2}}
|{{#expr:{{Period start|Pliocene}}-{{Period end|Pliocene}}}}
|Coined in the early 1830s from Greek πλείων (''pleíōn'') 'more' and καινός (''kainós'') 'new'
|-
|[[Miocene]]
|{{Period span/brief|Miocene|2}}
|{{#expr:{{Period start|Miocene}}-{{Period end|Miocene}}}}
|Coined in the early 1830s from Greek μείων (''meíōn'') 'less' and καινός (''kainós'') 'new'
|-
|[[Oligocene]]
|{{Period span/brief|Oligocene|2}}
|{{#expr:{{Period start|Oligocene}}-{{Period end|Oligocene}}}}
|Coined in the 1850s from Greek ὀλίγος (''olígos'') 'few' and καινός (''kainós'') 'new'
|-
|[[Eocene]]
|{{Period span/brief|Eocene|2}}
|{{#expr:{{Period start|Eocene}}-{{Period end|Eocene}}}}
|Coined in the early 1830s from Greek ἠώς (''ēōs'') 'dawn' and καινός (''kainós'') 'new', referring to the dawn of modern life during this epoch
|-
|[[Paleocene]]
|{{Period span/brief|Paleocene|2}}
|{{#expr:{{Period start|Paleocene}}-{{Period end|Paleocene}}}}
|Coined by [[Wilhelm Philippe Schimper]] in 1874 as a portmanteau of paleo- + Eocene, but on the surface from Greek παλαιός (''palaios'') 'old' and καινός (''kainós'') 'new'
|-
|[[Upper Cretaceous]]
|{{Period span/brief|Upper Cretaceous|2}}
|{{#expr:{{Period start|Upper Cretaceous}}-{{Period end|Upper Cretaceous}}}}
|rowspan="2" |See [[Cretaceous]]
|-
|[[Lower Cretaceous]]
|{{Period span/brief|Lower Cretaceous|2}}
|{{#expr:{{Period start|Lower Cretaceous}}-{{Period end|Lower Cretaceous}}}}
|-
|[[Upper Jurassic]]<br />
|{{Period span/brief|Upper Jurassic|2}}
|{{#expr:{{Period start|Upper Jurassic}}-{{Period end|Upper Jurassic}}}}
|rowspan="3" |See [[Jurassic]]
|-
|[[Middle Jurassic]]
|{{Period span/brief|Middle Jurassic|2}}
|{{#expr:{{Period start|Middle Jurassic}}-{{Period end|Middle Jurassic}}}}
|-
|[[Lower Jurassic]]<br />
|{{Period span/brief|Lower Jurassic|2}}
|{{#expr:{{Period start|Lower Jurassic}}-{{Period end|Lower Jurassic}}}}
|-
|[[Upper Triassic]]
|{{Period span/brief|Upper Triassic|2}}
|{{#expr:{{Period start|Upper Triassic}}-{{Period end|Upper Triassic}}}}
|rowspan="3" |See [[Triassic]]
|-
|[[Middle Triassic]]<br />
|{{Period span/brief|Middle Triassic|2}}
|{{#expr:{{Period start|Middle Triassic}}-{{Period end|Middle Triassic}}}}
|-
|[[Lower Triassic]]
|{{Period span/brief|Lower Triassic|2}}
|{{#expr:{{Period start|Lower Triassic}}-{{Period end|Lower Triassic}}}}
|-
|[[Lopingian]]
|{{Period span/brief|Lopingian|2}}
|{{#expr:{{Period start|Lopingian}}-{{Period end|Lopingian}}}}
|Named for [[Leping|Loping]], China, an anglicization of Mandarin 乐平 (''lèpíng'') 'peaceful music'
|-
|[[Guadalupian]]
|{{Period span/brief|Guadalupian|2}}
|{{#expr:{{Period start|Guadalupian}}-{{Period end|Guadalupian}}}}
|Named for the [[Guadalupe Mountains]] of the American Southwest, ultimately from Arabic وَادِي ٱل (''wādī al'') 'valley of the' and Latin ''lupus'' 'wolf' via Spanish
|-
|[[Cisuralian]]
|{{Period span/brief|Cisuralian|2}}
|{{#expr:{{Period start|Cisuralian}}-{{Period end|Cisuralian}}}}
|From Latin ''cis-'' (before) + Russian Урал (''Ural''), referring to the western slopes of the [[Ural Mountains]]
|-
|[[Pennsylvanian (geology)|Upper Pennsylvanian]]
|{{Period span/brief|Upper Pennsylvanian|2}}
|{{#expr:{{Period start|Upper Pennsylvanian}}-{{Period end|Upper Pennsylvanian}}}}
|rowspan="3" |Named for the US state of [[Pennsylvania]], from [[William Penn]] + Latin ''silvanus'' (forest) + -ia by analogy to Transylvania
|-
|[[Pennsylvanian (geology)|Middle Pennsylvanian]]
|{{Period span/brief|Middle Pennsylvanian|2}}
|{{#expr:{{Period start|Middle Pennsylvanian}}-{{Period end|Middle Pennsylvanian}}}}
|-
|[[Pennsylvanian (geology)|Lower Pennsylvanian]]
|{{Period span/brief|Lower Pennsylvanian|2}}
|{{#expr:{{Period start|Lower Pennsylvanian}}-{{Period end|Lower Pennsylvanian}}}}
|-
|[[Mississippian (geology)|Upper Mississippian]]
|{{Period span/brief|Upper Mississippian|2}}
|{{#expr:{{Period start|Upper Mississippian}}-{{Period end|Upper Mississippian}}}}
|rowspan="3" |Named for the [[Mississippi River]], from Ojibwe ᒥᐦᓯᓰᐱ (''misi-ziibi'') 'great river'
|-
|[[Mississippian (geology)|Middle Mississippian]]
|{{Period span/brief|Middle Mississippian|2}}
|{{#expr:{{Period start|Middle Mississippian}}-{{Period end|Middle Mississippian}}}}
|-
|[[Mississippian (geology)|Lower Mississippian]]
|{{Period span/brief|Lower Mississippian|2}}
|{{#expr:{{Period start|Lower Mississippian}}-{{Period end|Lower Mississippian}}}}
|-
|[[Upper Devonian]]
|{{Period span/brief|Upper Devonian|2}}
|{{#expr:{{Period start|Upper Devonian}}-{{Period end|Upper Devonian}}}}
|rowspan="3" |See [[Devonian]]
|-
|[[Middle Devonian]]
|{{Period span/brief|Middle Devonian|2}}
|{{#expr:{{Period start|Middle Devonian}}-{{Period end|Middle Devonian}}}}
|-
|[[Lower Devonian]]
|{{Period span/brief|Lower Devonian|2}}
|{{#expr:{{Period start|Lower Devonian}}-{{Period end|Lower Devonian}}}}
|-
|[[Pridoli Epoch|Pridoli]]
|{{Period span/brief|Pridoli|2}}
|{{#expr:{{Period start|Pridoli}}-{{Period end|Pridoli}}}}
|Named for the Homolka a Přídolí nature reserve near [[Prague]], Czechia
|-
|[[Ludlow Epoch|Ludlow]]
|{{Period span/brief|Ludlow|2}}
|{{#expr:{{Period start|Ludlow}}-{{Period end|Ludlow}}}}
|Named after [[Ludlow]], England
|-
|[[Wenlock Epoch|Wenlock]]
|{{Period span/brief|Wenlock|2}}
|{{#expr:{{Period start|Wenlock}}-{{Period end|Wenlock}}}}
|Named for the [[Wenlock Edge]] in [[Shropshire]], England
|-
|[[Llandovery Epoch|Llandovery]]
|{{Period span/brief|Llandovery|2}}
|{{#expr:{{Period start|Llandovery}}-{{Period end|Llandovery}}}}
|Named after [[Llandovery]], Wales
|-
|[[Upper Ordovician]]
|{{Period span/brief|Upper Ordovician|2}}
|{{#expr:{{Period start|Upper Ordovician}}-{{Period end|Upper Ordovician}}}}
|rowspan="3" |See [[Ordovician]]
|-
|[[Middle Ordovician]]
|{{Period span/brief|Middle Ordovician|2}}
|{{#expr:{{Period start|Middle Ordovician}}-{{Period end|Middle Ordovician}}}}
|-
|[[Lower Ordovician]]
|{{Period span/brief|Lower Ordovician|2}}
|{{#expr:{{Period start|Lower Ordovician}}-{{Period end|Lower Ordovician}}}}
|-
|[[Furongian]]
|{{Period span/brief|Furongian|2}}
|{{#expr:{{Period start|Furongian}}-{{Period end|Furongian}}}}
|From Mandarin 芙蓉 (''fúróng'') 'lotus', referring to the state symbol of [[Hunan]]
|-
|[[Miaolingian]]
|{{Period span/brief|Cambrian series 3|2}}
|{{#expr:{{Period start|Cambrian series 3}}-{{Period end|Cambrian series 3}}}}
|Named for the {{ill|Miao Ling|zh|苗嶺山脈}} mountains of [[Guizhou]], Mandarin for 'sprouting peaks'
|-
|[[Cambrian Series 2]] (informal)
|{{Period span/brief|Cambrian series 2|2}}
|{{#expr:{{Period start|Cambrian series 2}}-{{Period end|Cambrian series 2}}}}
|See [[Cambrian]]
|-
|[[Terreneuvian]]
|{{Period span/brief|Terreneuvian|2}}
|{{#expr:{{Period start|Terreneuvian}}-{{Period end|Terreneuvian}}}}
|Named for [[Terre-Neuve (New France)|Terre-Neuve]], a French [[calque]] of [[Newfoundland (island)|Newfoundland]]
|}

== History of the geologic time scale ==
{{See also|History of geology|History of paleontology}}

=== Early history ===
The most modern geological time scale was not formulated until 1911<ref name="Holmes_19113">{{Cite journal |last1=Holmes |first1=Arthur |date=1911-06-09 |title=The association of lead with uranium in rock-minerals, and its application to the measurement of geological time |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 |bibcode=1911RSPSA..85..248H |doi=10.1098/rspa.1911.0036 |issn=0950-1207 |doi-access=free}}</ref> by [[Arthur Holmes]] (1890 – 1965), who drew inspiration from [[James Hutton]] (1726–1797), a Scottish Geologist who presented the idea of uniformitarianism or the theory that changes to the Earth's crust resulted from continuous and uniform processes.<ref>{{Cite web |title=James Hutton {{!}} Father of Modern Geology, Scottish Naturalist {{!}} Britannica |url=https://www.britannica.com/biography/James-Hutton |access-date=2024-12-03 |website=www.britannica.com |language=en}}</ref> The broader concept of the relation between rocks and time can be traced back to (at least) the [[philosopher]]s of [[Ancient Greece]] from 1200 BC to 600 AD. [[Xenophanes|Xenophanes of Colophon]] (c. 570–487&nbsp;[[Common era|BCE]]) observed rock beds with fossils of seashells 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_20093">{{Cite journal |last1=Fischer |first1=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 |bibcode=2009Sedim..56....3F |doi=10.1111/j.1365-3091.2008.01009.x |s2cid=128604255}}</ref> This view was shared by a few of Xenophanes's scholars and those that followed, including [[Aristotle]] (384–322 BC) 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 recognized by [[History of science and technology in China|Chinese naturalist]] [[Shen Kuo]]<ref name="Nathan 19953">{{Cite book |last=Sivin |first=Nathan |title=Science in ancient China: researches and reflections |date=1995 |publisher=Variorum |isbn=0-86078-492-4 |oclc=956775994}}</ref> (1031–1095) and [[Islam]]ic [[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_20093" /> 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_20093" /> Avicenna also recognized fossils as "petrifications of the bodies of plants and animals",<ref name="Adams_19383">{{Cite book |last=Adams |first=Frank D. |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), who drew from [[Aristotle|Aristotle's]] natural philosophy, extending this into a theory of a petrifying fluid.<ref name="Johnson">{{Cite journal |last1=Johnson |first1=Chris |last2=Bentley |first2=Callan |last3=Panchuk |first3=Karla |last4=Affolter |first4=Matt |last5=Layou |first5=Karen |last6=Jaye |first6=Shelley |last7=Kohrs |first7=Russ |last8=Inkenbrandt |first8=Paul |last9=Mosher |first9=Cam |last10=Ricketts |first10=Brian |last11=Estrada |first11=Charlene |title=Geologic Time and Relative Dating |url=https://open.maricopa.edu/fallglg102/part/sedimentary-rocks-and-environments/ |journal=Maricopa Open Digital Press |language=en}}</ref> These works appeared to have little influence on [[scholar]]s 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_20093" /> 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_19383">{{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_20093" />

{{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.}}
[[File:Sketch of the Succession pf Strata and their relative Altitudes.jpg|thumb|Sketch of the Succession of Strata and their Relative Altitudes (William Smith)]]
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_20093" /> Although many theories surrounding philosophy and concepts of rocks were developed in earlier years, "the first serious attempts to formulate a geological time scale that could be applied anywhere on Earth were made in the late 18th century."<ref name="Johnson" /> Later, in the 19th century, academics further developed theories on stratification. [[William Smith (geologist)|William Smith]], often referred to as the "Father of Geology"<ref name="earthobservatory.nasa.gov-2008" /> developed theories through observations rather than drawing from the scholars that came before him. Smith's work was primarily based on his detailed study of rock layers and fossils during his time and he created "the first map to depict so many rock formations over such a large area".<ref name="earthobservatory.nasa.gov-2008">{{Cite web |date=2008-05-08 |title=William Smith (1769-1839) |url=https://earthobservatory.nasa.gov/features/WilliamSmith |access-date=2024-12-02 |website=earthobservatory.nasa.gov |language=en}}</ref> After studying rock layers and the fossils they contained, [[William Smith (geologist)|Smith]] concluded that each layer of rock contained distinct material that could be used to identify and correlate rock layers across different regions of the world.<ref name="Smith-1816">{{Cite book |last1=Smith |first1=William |url=https://www.biodiversitylibrary.org/bibliography/106808 |title=Strata identified by organized fossils: containing prints on colored paper of the most characteristic specimens in each stratum |last2=Smith |first2=William |date=1816 |publisher=Printed by W. Arding ..., and sold by the author ..., J. Sowerby ..., Sherwood, Neely, and Jones, and Longman, Hurst, Rees, Orme, and Brown ..., and by all booksellers |location=London |doi=10.5962/bhl.title.106808}}</ref> Smith developed the concept of faunal succession or the idea that fossils can serve as a marker for the age of the strata they are found in and published his ideas in his 1816 book, "Strata identified by organized fossils."<ref name="Smith-1816" />

=== 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_20093"/> 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.com/books?id=xz28AAAAIAAJ |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 |last1=Kardel |first1=Troels |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|title=2.27 the Prodromus to a Dissertation on a Solid Naturally Contained within a Solid }}</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_20093"/> These basic principles, albeit with improved and more nuanced interpretations, still form the foundational principles of determining the correlation of strata relative to 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 during the era of Biblical models by [[Thomas Burnet (theologian)|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_20093"/> [[Anton Moro]] (1687–1784) also used primary and secondary divisions for rock units but his mechanism was volcanic.<ref name="Moro_1740">{{Cite book |last=Moro |first=Anton Lazzaro |url=https://books.google.com/books?id=03RBAAAAYAAJ |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_20093"/> 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_20093"/> 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 Neptunism 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 |s2cid=251578886 |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 |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 |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 |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 ===
[[File:Pierre Lecomte du Noüy - LES AGES DE LA VIE SUR LA TERRE - in L'Homme et sa destinée - 1947.jpg|thumb|One example of an obsolete geological time scale (France, mid-1940s).]]
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 are considered the first international geological time scales by Holmes in 1911 and 1913.<ref name="Holmes_19113"/><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 |bibcode=2001GSLSP.190..121L |s2cid=128686640 |issn=0305-8719}}</ref> The discovery of [[isotope]]s 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 |bibcode=1913Natur..92..399S |s2cid=3965303 |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 |s2cid=129166282 |issn=0371-6260}}</ref><ref name="GTS1960">{{Cite journal |date=1960 |title=A Revised Geological Time-Scale |journal=Nature |language=en |volume=187 |issue=4731 |pages=27–28 |doi=10.1038/187027d0 |bibcode=1960Natur.187T..27. |s2cid=4179334 |issn=0028-0836|doi-access=free }}</ref>

=== Modern international geological time scale ===
The establishment of the IUGS in 1961<ref name="Harrison_1978">{{Cite journal |last=Harrison |first=James M. |title=The Roots of IUGS |date=1978-03-01 |journal=Episodes |volume=1 |issue=1 |pages=20–23 |doi=10.18814/epiiugs/1978/v1i1/005 |issn=0705-3797|doi-access=free }}</ref> and acceptance of the Commission on Stratigraphy (applied in 1965)<ref name="ICS_statutes_1986">{{Cite book |author=International Union of Geological Sciences. Commission on Stratigraphy |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 |title=A geologic time scale |date=1982 |publisher=Cambridge University Press |author=W. B. Harland |isbn=0-521-24728-4 |location=Cambridge [England] |oclc=8387993}}</ref> 1989,<ref name="GTS1989">{{Cite book |title=A geologic time scale 1989 |date=1990 |publisher=Cambridge University Press |author=W. B. Harland |isbn=0-521-38361-7 |location=Cambridge |oclc=20930970}}</ref> 2004,<ref name="GTS2004">{{Cite book |title=A geologic time scale 2004 |date=2004 |publisher=Cambridge University Press |author1=F. M. Gradstein |author2=James G. Ogg |author3=A. Gilbert Smith |isbn=0-511-08201-0 |location=Cambridge, UK |oclc=60770922}}</ref> 2008,<ref name="GTS2008">{{Cite journal |last1=Gradstein |first1=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 |bibcode=2008NewSt..43....5G |issn=0078-0421}}</ref> 2012,<ref name="GTS2012">{{Cite book |title=The geologic time scale 2012. Volume 2 |date=2012 |publisher=Elsevier |author=F. M. Gradstein |isbn=978-0-444-59448-8 |edition=1st |location=Amsterdam |oclc=808340848}}</ref> 2016,<ref name="GTS2016">{{Cite book |last=Ogg |first=James G. |title=A concise geologic time scale 2016 |date=2016 |publisher=Elsevier |others=Gabi Ogg, F. M. Gradstein |isbn=978-0-444-59468-6 |location=Amsterdam, Netherlands |oclc=949988705}}</ref> and 2020.<ref name="GTS2020">{{Cite book |title=Geologic time scale 2020 |date=2020 |author1=F. M. Gradstein |author2=James G. Ogg |author3=Mark D. Schmitz |author4=Gabi Ogg |isbn=978-0-12-824361-9 |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 of oversight by the 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="ICS" /> 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 |last1=Crutzen |first1=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. |series=The Anthropocene: Politik—Economics—Society—Science |s2cid=245639062 |editor2-last=Lax |editor2-first=Gregor |editor3-last=Crutzen |editor3-first=Paul J. |editor4-last=Pöschl |editor4-first=Ulrich}}</ref> the ''Anthropocene'' 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> 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 |last1=Gibbard |first1=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 |journal=Episodes |volume=45 |issue=4 |pages=349–357 |language=en |doi=10.18814/epiiugs/2021/021029 |bibcode=2021Episo..45..349G |s2cid=244165877 |issn=0705-3797|doi-access=free }}</ref><ref name="Head_2021">{{Cite journal |last1=Head |first1=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 |journal=Episodes |volume=45 |issue=4 |pages=359–376 |language=en |doi=10.18814/epiiugs/2021/021031 |s2cid=244145710 |issn=0705-3797|doi-access=free }}</ref><ref name="Zalasiewicz_2021">{{Cite journal |last1=Zalasiewicz |first1=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 |journal=Earth's Future |language=en |volume=9 |issue=3 |article-number=e2020EF001896 |doi=10.1029/2020EF001896 |bibcode=2021EaFut...901896Z |s2cid=233816527 |issn=2328-4277|doi-access=free }}</ref><ref name="Bauer_2021">{{Cite journal |last1=Bauer |first1=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 |page=332 |doi=10.1038/d41586-021-02448-z |pmid=34522014 |bibcode=2021Natur.597..332B |s2cid=237515330 |issn=0028-0836}}</ref>

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 recognise 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 |pmid=32433629 |s2cid=182238145 |issn=0028-0836}}</ref> The formal proposal was completed and submitted to the Subcommission on Quaternary Stratigraphy in late 2023 for a section in [[Crawford Lake (Halton Region)|Crawford Lake]], [[Ontario]], with heightened Plutonium levels corresponding to 1952 CE.<ref>{{cite web |title=Working Group on the 'Anthropocene' |url=https://quaternary.stratigraphy.org/working-groups/anthropocene |website=Subcommission on Quaternary Stratigraphy |publisher=International Commission on Stratigraphy |access-date=23 October 2025}}</ref> This proposal was rejected as a formal geologic epoch in early 2024, to be left instead as an "invaluable descriptor of human impact on the Earth system"<ref>{{cite web |title=Joint statement by the IUGS and ICS on the vote by the ICS Subcommission on Quaternary Stratigraphy |url=https://stratigraphy.org/news/152 |website=International Commission on Stratigraphy |publisher=International Commission on Stratigraphy |access-date=23 October 2025}}</ref>

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

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

==== 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 and the Subcommission on Precambrian Stratigraphy.<ref name="ICS" /> 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="GTS2012b">{{cite book |last=Van Kranendonk |first=Martin J. |chapter=A Chronostratigraphic Division of the Precambrian |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 |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 (changes from the current scale [v2023/09]) are italicised:

* Hadean Eon (4567''–4030'' Ma)
** [[Chaotian (geology)|''Chaotian'']] Era/Erathem (''4567–4404'' Ma) – the name alluding both to the [[Chaos (cosmogony)|mythological Chaos]] and the 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 |archive-url=https://web.archive.org/web/20120419024812/http://www.astro.washington.edu/courses/astro321/Chambers_EPSL_04.pdf |archive-date=2012-04-19 |url-status=live |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>
** ''Jack Hillsian'' or ''Zirconian'' Era/Erathem (''4404–4030'' Ma) – both names allude to the Jack Hills Greenstone Belt which provided the oldest mineral grains on Earth, [[zircon]]s.<ref name="GTS2012" /><ref name="Goldblatt_2010" />
* Archean Eon/Eonothem (''4030–2420'' Ma)
** Paleoarchean Era/Erathem (''4030–3490'' Ma)
*** ''Acastan'' Period/System (''4030–3810'' Ma) – named after the [[Acasta Gneiss]], one of the oldest preserved pieces of [[continental crust]].<ref name="GTS2012" /><ref name="Goldblatt_2010" />
*** ''Isuan'' Period/System (''3810–3490'' Ma) – named after the [[Isua Greenstone Belt]].<ref name="GTS2012" />
** Mesoarchean Era/Erathem (''3490–2780'' Ma)
*** ''Vaalbaran'' Period/System (''3490–3020'' Ma) – based on the names of the [[Kaapvaal craton|Kaapvaal]] (Southern Africa) and [[Pilbara craton|Pilbara]] (Western Australia) [[craton]]s, to reflect the growth of stable continental nuclei or proto-[[craton]]ic kernels.<ref name="GTS2012" />
*** ''Pongolan'' Period/System (''3020–2780'' 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 (''2780–2420'' Ma)
*** ''Methanian'' Period/System (''2780–2630'' Ma) – named for the inferred predominance of [[methanotrophic]] [[prokaryote]]s<ref name="GTS2012" />
*** Siderian Period/System (''2630–2420'' Ma) – named for the voluminous [[banded iron formation]]s formed within its duration.<ref name="GTS2012" />
* Proterozoic Eon/Eonothem (''2420''–538.8 Ma){{efn|name=EdiacaranDate|group=note}}
** Paleoproterozoic Era/Erathem (''2420–1780'' Ma)
*** ''Oxygenian'' Period/System (''2420–2250'' Ma) – named for displaying the first evidence for a global oxidising atmosphere.<ref name="GTS2012" />
*** ''Jatulian'' or ''Eukaryian'' Period/System (''2250–2060'' Ma) – names are respectively for the Lomagundi–Jatuli δ<sup>13</sup>C 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 |article-number=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 |archive-url=https://web.archive.org/web/20240616162702/https://www.afrikibouge.com/publications/Article%20Albani.pdf |archive-date=16 June 2024 |journal=Nature |volume=466 |issue=7302 |pages=100–104 |bibcode=2010Natur.466..100A |doi=10.1038/nature09166 |pmid=20596019 |s2cid=4331375}}</ref> first fossil appearance of [[eukaryote]]s.<ref name="GTS2012" />
*** ''Columbian Period/System'' (''2060–1780'' Ma) – named after the [[supercontinent]] [[Columbia (supercontinent)|Columbia]].<ref name="GTS2012" />
** Mesoproterozoic Era/Erathem (''1780–850'' Ma)
*** ''Rodinian'' Period/System (''1780–850'' 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:-4567.3 till:-538.8
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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: -541 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: -541 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: -541 text:Ediacaran color:ediacaran
    from: -850  till: -630 text:Cryogenian 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>

ICC pre-Cambrian timeline (v2024/12, current {{As of|2025|01|lc=y}}), 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:-4567.3 till:-538.8
TimeAxis = orientation:horizontal
ScaleMajor = unit:year increment:500 start:-4500
ScaleMinor = unit:year increment:100 start:-4500
PlotData = 
 align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5)
  bar:Eonothem/Eon
    from: -2500 till: -538.8 text:Proterozoic color:proterozoic
    from: -4031 till: -2500 text:Archean color:archean
    from: start till: -4031 text:Hadean color:hadean
  bar:Erathem/Era
    from: -1000 till: -538.8 text:Neoproterozoic color:neoproterozoic
    from: -1600 till: -1000 text:Mesoproterozoic color:mesoproterozoic
    from: -2500 till: -1600 text:Paleoproterozoic color:paleoproterozoic
    from: -2800 till: -2500 text:Neoarchean color:neoarchean
    from: -3200 till: -2800 text:Mesoarchean color:mesoarchean
    from: -3600 till: -3200 text:Paleoarchean color:paleoarchean
    from: -4031 till: -3600 text:Eoarchean color:eoarchean
    from: start till: -4031 color:white
  bar:System/Period fontsize:7
    from: -635 till: -538.8 text:Ediacaran color:ediacaran
    from: -720 till: -635 text:Cryogenian 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>

==Table of geologic time==
{{More citations needed section|date=November 2023}}
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 ~538.8 Ma (~11.8% of Earth's history), whilst the previous three eons{{Efn|name=Precam|group=note}} collectively span ~4,028.2 Ma (~88.2% 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"/>

While some regional terms are still in use,<ref name="GTS2012_Precambrian" /> the table of geologic time conforms to the [[nomenclature]], ages, and colour codes set forth by the International Commission on Stratigraphy in the official International Chronostratigraphic Chart.<ref name="ICS_statutes" /><ref name="ICS_IGTS">{{cite web |title=International Commission on Stratigraphy |url=https://stratigraphy.org/ |access-date=5 June 2022 |work=International Geological Time Scale}}</ref> The International Commission on Stratigraphy 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 |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>

{{sticky header}}
{| class="wikitable collapsible sticky-header" style="clear:both;margin:0; font-size:95%"
!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 (v2024/12). An <sup>*</sup> indicates boundaries where a [[Global Boundary Stratotype Section and Point]] has been internationally agreed.|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 peoples|Austronesian expansion]], increasing [[Industrial Revolution|industrial]] [[Carbon dioxide in the Earth's atmosphere|CO<sub>2</sub>]].
| style="background:#fcf0f2" |{{Period start|meghalayan}} {{Period start error|meghalayan}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| style="background:#fcf0de" |[[Greenlandian]]
|Climate stabilises. 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}}<sup>*</sup>
|-
| 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]]
|[[Mid-Pleistocene Transition]] occurs, high amplitude [[100,000-year problem|100 ka]] [[glacial period|glacial cycles]]. Rise of [[Homo sapiens]].
| style="background:{{period color|Middle Pleistocene}}" |{{Period start|middle pleistocene}}{{Period start error|middle pleistocene}}<sup>*</sup>
|-
| style="background:{{period color|Calabrian}}" |[[Early Pleistocene|Calabrian]]
|Further cooling of the climate. Giant [[terror birds]] go extinct. Spread of [[Homo erectus]] across [[Afro-Eurasia]].
| style="background:{{period color|Calabrian}}" |{{Period start|calabrian}} {{Period start error|calabrian}}<sup>*</sup>
|-
| style="background:{{period color|Gelasian}}" |[[Gelasian]]
|Start of [[Quaternary glaciation]]s and unstable climate.<ref name="Hoag_2017">{{Cite journal |last1=Hoag |first1=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 |access-date=5 June 2022 |archive-date=1 May 2022 |archive-url=https://web.archive.org/web/20220501144059/https://www.annualreviews.org/doi/10.1146/annurev-environ-102016-060653 }}</ref> Rise of the [[Pleistocene megafauna]] and [[Homo habilis]].
| style="background:{{period color|Gelasian}}" |{{Period start|gelasian}} {{Period start error|geliasian}}<sup>*</sup>
|-
| 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]]s, 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}}<sup>*</sup>
|-
| style="background:{{period color|Zanclean}}" |[[Zanclean]]
|[[Zanclean flood]]ing of the [[Mediterranean Basin]]. Cooling climate continues from the Miocene. First [[Equus (genus)|equines]] and [[Elephantimorpha|elephantines]]. [[Ardipithecus]] in Africa.<ref name="Tyson_2009" />
| style="background:{{period color|Zanclean}}" |{{Period start|zanclean}} {{Period start error|zanclean}}<sup>*</sup>
|-
| 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]]. Sahara desert formation begins. [[Greenhouse and Icehouse Earth|Moderate icehouse climate]], punctuated by [[ice age]]s and re-establishment of [[East Antarctic Ice Sheet]]. [[Choristodera|Choristoderes]], the last non-crocodilian [[Sebecosuchia|crocodylomorphs]] and [[Creodonta|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}}<sup>*</sup>
|-
| style="background:{{period color|Tortonian}}" |[[Tortonian]]
| style="background:{{period color|Tortonian}}" |{{Period start|tortonian}} {{Period start error|tortonian}}<sup>*</sup>
|-
| 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]]s. Ancestor of [[Hominidae|great apes]].
| style="background:{{period color|Serravallian}}" |{{Period start|serravallian}} {{Period start error|serravallian}}<sup>*</sup>
|-
| style="background:{{period color|Langhian}}" |[[Langhian]]
| style="background:{{period color|Langhian}}" |{{Period start|langhian}} {{Period start error|langhian}}<sup>*</sup>
|-
| 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=CO<sub>2</sub>-forced climate thresholds during the Phanerozoic |url=http://droyer.web.wesleyan.edu/PhanCO2%28GCA%29.pdf |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. [[Poaceae|Grasses]] become ubiquitous. Ancestor of [[ape]]s, 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 |last1=Nengo |first1=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 |pmid=28796200 |bibcode=2017Natur.548..169N |s2cid=4397839 |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}}<sup>*</sup>
|-
| 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|url=http://doc.rero.ch/record/16546/files/PAL_E3220.pdf }}</ref> Rapid [[evolution]] and diversification of fauna, especially [[mammal]]s (e.g. first [[Macropodiformes|macropods]] and [[Pinnipedia|seals]]). Major evolution and dispersal of modern types of [[flowering plant]]s. [[Cimolesta]]ns, 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}}<sup>*</sup>
|-
| style="background:{{period color|Rupelian}}" |[[Rupelian]]
| style="background:{{period color|Rupelian}}" |{{Period start|rupelian}} {{Period start error|rupelian}}<sup>*</sup>
|-
| 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]]s (e.g. [[creodont]]s, [[Miacoidea|miacoids]], "[[condylarth]]s" etc.) flourish and continue to develop during the epoch. Appearance of several "modern" mammal families. [[Archaeoceti|Primitive whales]] and [[Sirenia|sea cows]] diversify after returning to water. [[Bird]]s continue to diversify. First [[kelp]], [[Diprotodontia|diprotodonts]], [[bear]]s and [[simian]]s. 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}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| 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 [[Parts-per notation|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 [[passerine]]s, [[ruminant]]s, [[pangolin]]s, [[bat]]s and true [[primate]]s.
| style="background:{{period color|Ypresian}}" |{{Period start|ypresian}} {{Period start error|ypresian}}<sup>*</sup>
|-
| 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]]. [[Mammal]]s and [[bird]]s (avians) diversify rapidly into a number of lineages following the extinction event (while the marine revolution stops). Multituberculates and the first [[rodent]]s 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]]ns and [[plesiadapiformes]] (stem primates) appear. [[Australidelphia|Some marsupials]] migrate to Australia.
| style="background:{{period color|Thanetian}}" |{{Period start|thanetian}} {{Period start error|thanetian}}<sup>*</sup>
|-
| style="background:{{period color|Selandian}}" |[[Selandian]]
| style="background:{{period color|Selandian}}" |{{Period start|selandian}} {{Period start error|selandian}}<sup>*</sup>
|-
| style="background:{{period color|Danian}}" |[[Danian]]
| style="background:{{period color|Danian}}" |{{Period start|danian}} {{Period start error|danian}}<sup>*</sup>
|-
| 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]]s proliferate (after developing many features since the Carboniferous), along with new types of [[insect]]s, while other seed plants (gymnosperms and seed ferns) decline. More modern [[teleost]] fish begin to appear. [[Ammonoid]]s, [[Belemnoidea|belemnites]], [[rudist]] [[bivalve]]s, [[sea urchin]]s and [[sponge]]s all common. Many new types of [[dinosaur]]s (e.g. [[Tyrannosauridae|tyrannosaurs]], [[Titanosauridae|titanosaurs]], [[Hadrosauridae|hadrosaurs]], and [[Ceratopsidae|ceratopsids]]) evolve on land, while [[crocodilia]]ns appear in water and probably cause the last temnospondyls to die out; and [[mosasaur]]s and modern types of sharks appear in the sea. The revolution started by marine reptiles and sharks reaches its peak, though ichthyosaurs vanish a few million years after being heavily reduced at the [[Bonarelli Event]]. Toothed and [[Neornithes|toothless avian birds]] coexist with pterosaurs. Modern [[monotreme]]s, [[metatheria]]n (including [[marsupial]]s, who migrate to South America) and [[eutheria]]n (including [[placental]]s, [[leptictida]]ns and [[cimolesta]]ns) mammals appear while the last non-mammalian cynodonts die out. First [[terrestrial crab]]s. 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]]s 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]]s disappear. Climate initially warm, but later it cools.
| style="background:{{period color|Maastrichtian}}" |{{Period start|maastrichtian}} {{Period start error|maastrichtian}}<sup>*</sup>
|-
| style="background:{{period color|Campanian}}" |[[Campanian]]
| style="background:{{period color|Campanian}}" |{{Period start|campanian}} {{Period start error|campanian}}<sup>*</sup>
|-
| style="background:{{period color|Santonian}}" |[[Santonian]]
| style="background:{{period color|Santonian}}" |{{Period start|santonian}} {{Period start error|santonian}}<sup>*</sup>
|-
| style="background:{{period color|Coniacian}}" |[[Coniacian]]
| style="background:{{period color|Coniacian}}" |{{Period start|coniacian}} {{Period start error|coniacian}}<sup>*</sup>
|-
| style="background:{{period color|Turonian}}" |[[Turonian]]
| style="background:{{period color|Turonian}}" |{{Period start|turonian}} {{Period start error|turonian}}<sup>*</sup>
|-
| style="background:{{period color|Cenomanian}}" |[[Cenomanian]]
| style="background:{{period color|Cenomanian}}" |{{Period start|cenomanian}} {{Period start error|cenomanian}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| style="background:{{period color|Hauterivian}}" |[[Hauterivian]]
| style="background:{{period color|Hauterivian}}" |~{{Period start|hauterivian}} {{Period start error|hauterivian}}<sup>*</sup>
|-
| style="background:{{period color|Valanginian}}" |[[Valanginian]]
| style="background:{{period color|Valanginian}}" |~{{Period start|valanginian}} {{Period start error|valanginian}}<sup>*</sup>
|-
| 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]]s (especially [[conifer]]s, [[cycad]]s and [[cycadeoid]]s) and [[fern]]s common. [[Dinosaur]]s, including [[sauropod]]s, [[carnosaur]]s, [[stegosaur]]s and [[coelurosaur]]s, become the dominant land vertebrates. Mammals diversify into [[Shuotheriidae|shuotheriids]], [[australosphenida]]ns, [[eutriconodont]]s, [[multituberculate]]s, [[symmetrodont]]s, [[dryolestid]]s and [[boreosphenida]]ns but mostly remain small. First [[Avialae|birds]], [[Squamata|lizards, snakes]] and [[turtle]]s. First [[brown algae]], [[Batoidea|rays]], [[shrimp]]s, [[crab]]s and [[lobster]]s. [[Parvipelvia]]n ichthyosaurs and [[plesiosaur]]s diverse. Rhynchocephalians throughout the world. [[Bivalve]]s, [[ammonoid]]s and [[Belemnoidea|belemnites]] abundant. [[Sea urchin]]s very common, along with [[crinoid]]s, [[starfish]], [[Porifera|sponges]], and [[Terebratulida|terebratulid]] and [[Rhynchonellida|rhynchonellid]] [[brachiopod]]s. Breakup of [[Pangaea]] into [[Laurasia]] and [[Gondwana]], with the latter also breaking into two main parts; the [[Pacific]] and [[Arctic Ocean]]s form. [[Tethys Ocean]] forms. [[Nevadan orogeny]] in North America. [[Rangitata Orogeny|Rangitata]] and [[Cimmerian Orogeny|Cimmerian orogenies]] taper off. Atmospheric {{CO2}} levels 3–4 times the present-day levels (1200–1500 ppmv, compared to today's 400 ppmv<ref name="Royer_2006" />{{efn|name="atmospheric-carbon-dioxide"|group=note}}). [[Crocodylomorph]]s (last pseudosuchians) seek out an aquatic lifestyle. [[Mesozoic marine revolution]] continues from late Triassic. [[Tentaculita]]ns 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}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| style="background:{{period color|Bajocian}}" |[[Bajocian]]
| style="background:{{period color|Bajocian}}" |{{Period start|bajocian}} {{Period start error|bajocian}}<sup>*</sup>
|-
| style="background:{{period color|Aalenian}}" |[[Aalenian]]
| style="background:{{period color|Aalenian}}" |{{Period start|aalenian}} {{Period start error|aalenian}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| style="background:{{period color|Pliensbachian}}" |[[Pliensbachian]]
| style="background:{{period color|Pliensbachian}}" |{{Period start|pliensbachian}} {{Period start error|pliensbachian}}<sup>*</sup>
|-
| style="background:{{period color|Sinemurian}}" |[[Sinemurian]]
| style="background:{{period color|Sinemurian}}" |{{Period start|sinemurian}} {{Period start error|sinemurian}}<sup>*</sup>
|-
| style="background:{{period color|Hettangian}}" |[[Hettangian]]
| style="background:{{period color|Hettangian}}" |{{Period start|hettangian}} {{Period start error|hettangian}}<sup>*</sup>
|-
| 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]]s dominant on land as [[pseudosuchia]]ns and in the air as [[pterosaur]]s. [[Dinosaur]]s also arise from bipedal archosaurs. [[Ichthyosauria|Ichthyosaur]]s and [[nothosaur]]s (a group of sauropterygians) dominate large marine fauna. [[Cynodont]]s become smaller and nocturnal, eventually becoming the first true [[mammals]], while other remaining synapsids die out. [[Rhynchosaur]]s (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]]n [[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. 260–225&nbsp;Ma). [[Carnian pluvial event]] occurs around 234–232 Ma, allowing the first dinosaurs and [[lepidosaurs]] (including [[rhynchocephalia]]ns) 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]]ns), all [[crocopoda]]ns 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 |bibcode=1997NovaH..65....1M |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}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| 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]]es 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]]s and [[therapsid]]s) become widespread and dominant, while [[parareptile]]s and [[Temnospondyli|temnospondyl]] [[amphibian]]s 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]]s, ammonoids (including goniatites), and [[orthocerida]]ns all abundant. [[Sauria|Crown reptiles]] arise from earlier diapsids, and split into the ancestors of [[Lepidosauromorpha|lepidosaurs]], [[Kuehneosauridae|kuehneosaurids]], [[Choristodera|choristoderes]], [[Crocopoda|archosaurs]], [[testudinata]]ns, [[Ichthyosauromorpha|ichthyosaurs]], [[thalattosaurs]], and [[sauropterygia]]ns. Cynodonts evolve from larger therapsids. [[Olson's Extinction]] (273&nbsp;Ma), [[Capitanian mass extinction event|End-Capitanian extinction]] (260&nbsp;Ma), and [[Permian–Triassic extinction event]] (252&nbsp;Ma) occur one after another: more than 80% of life on Earth becomes extinct in the lattermost, including most [[retaria]]n 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]]s, [[trilobite]]s, [[graptolite]]s, [[hyoliths]], [[Edrioasteroidea|edrioasteroid crinozoans]], [[blastoid]]s 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. 260–225&nbsp;Ma), forming the New England Fold Belt.
| style="background:{{period color|Changhsingian}}" |{{Period start|changhsingian}} {{Period start error|changhsingian}}<sup>*</sup>
|-
| style="background:{{period color|Wuchiapingian}}" |[[Wuchiapingian]]
| style="background:{{period color|Wuchiapingian}}" |{{Period start|wuchiapingian}} {{Period start error|wuchiapingian}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| style="background:{{period color|Wordian}}" |[[Wordian]]
| style="background:{{period color|Wordian}}" |{{Period start|wordian}} {{Period start error|wordian}}<sup>*</sup>
|-
| style="background:{{period color|Roadian}}" |[[Roadian]]
| style="background:{{period color|Roadian}}" |{{Period start|roadian}} {{Period start error|roadian}}<sup>*</sup>
|-
| 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}}<sup>*</sup>
|-
| style="background:{{period color|Sakmarian}}" |[[Sakmarian]]
| style="background:{{period color|Sakmarian}}" |{{Period start|sakmarian}} {{Period start error|sakmarian}}<sup>*</sup>
|-
| style="background:{{period color|Asselian}}" |[[Asselian]]
| style="background:{{period color|Asselian}}" |{{Period start|asselian}} {{Period start error|asselian}}<sup>*</sup>
|-
| 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" |Continuation of the [[Variscan orogeny]] ([[Ouachita orogeny|Ouachita]] and [[Alleghanian orogeny|Alleghanian]] orogenies) with growth of the [[Central Pangean Mountains]].<ref name=":2" /> [[Uralian orogeny|Ural orogeny]] continues with continental collision between [[Kazakhstania]] and [[Laurasia|Laurussia]].<ref>{{Cite journal |last=Puchkov |first=Victor N. |date=2009 |title=The evolution of the Uralian orogen |url=https://www.lyellcollection.org/doi/abs/10.1144/SP327.9 |journal=Geological Society, London, Special Publications |volume=327 |issue=1 |pages=161–195 |doi=10.1144/SP327.9}}</ref> Humid, [[Coal forest|coal swamps]] form in [[Foreland basin|foreland basins]] of the Central Pangean Mountains and around [[North China Craton|North]] and [[South China Craton|South China]] cratons.<ref>{{Cite journal |last=Nelsen |first=Matthew P. |last2=DiMichele |first2=William A. |last3=Peters |first3=Shanan E. |last4=Boyce |first4=C. Kevin |date=2016-03-01 |title=Delayed fungal evolution did not cause the Paleozoic peak in coal production |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC4780611/ |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=113 |issue=9 |pages=2442–2447 |doi=10.1073/pnas.1517943113 |issn=1091-6490 |pmc=4780611 |pmid=26787881}}</ref> As the [[Late Paleozoic icehouse|Late Paleozoic Ice Age]] (LPIA) continues, waxing and waning of ice sheets causes rapid changes in global sea level, flooding these regions and depositing [[Cyclothems|cyclothem]] sequences.<ref>{{Cite journal |last=Fielding |first=Christopher R. |date=2021-06-01 |title=Late Palaeozoic cyclothems – A review of their stratigraphy and sedimentology |url=https://www.sciencedirect.com/science/article/pii/S0012825221001124 |journal=Earth-Science Reviews |volume=217 |pages=103612 |doi=10.1016/j.earscirev.2021.103612 |issn=0012-8252}}</ref> Atmospheric oxygen levels rise to over 25% before decreasing again.<ref name=":7">{{Cite journal |last=Cannell |first=Alan |last2=Blamey |first2=Nigel |last3=Brand |first3=Uwe |last4=Escapa |first4=Ignacio |last5=Large |first5=Ross |date=2022 |title=A revised sedimentary pyrite proxy for atmospheric oxygen in the Paleozoic: Evaluation for the Silurian-Devonian-Carboniferous period and the relationship of the results to the observed biosphere record |url=https://www.sciencedirect.com/science/article/pii/S0012825222001465 |journal=Earth-Science Reviews |volume=231 |pages= |doi=10.1016/j.earscirev.2022.104062 |issn=0012-8252}}</ref> Appearance of [[aragonite]] reef builders, including [[algae]] and [[Sponge|sponges]].<ref name=":1" /> Freshwater [[Eurypterid|Eurypterid]]s (sea scorpions). On land, [[Neoptera]] appear, and [[Miomoptera]] show earliest evidence for complete [[metamorphosis]]. First true terrestrial [[Amphibian|amphibians]]. [[Amniote|Amniotes]] appear and split into two groups: [[Sauropsida|sauropsids]] (reptiles) and [[Synapsida|synapsids]] (mammals).<ref name=":8">{{Cite book |last=Parker |first=Steve |title=Evolution: the Whole Story |date=2015 |publisher=Thames & Hudson Ltd |isbn=978-0-500-29173-3 |location=London}}</ref> ''[[Lepidodendron]]'' and ''[[Sigillaria]]'' [[Lycopodiopsida|lycopod]] trees dominate coal swamps, with smaller [[Equisetidae|sphenopsids]] (horsetails) and [[Pteridospermatophyta|seed fern]]s between. [[Gymnosperm|Gymnosperms]], including [[Conifer|conifer]]s and [[Cycad|cycad]]s grow on drier ground.<ref name=":1" /> LPIA peaks at Carboniferous-Permian boundary. A drop in CO<sub>2</sub> levels and increase in arid conditions<ref name=":9">{{Cite journal |last=Montañez |first=Isabel Patricia |date=2022 |title=Current synthesis of the penultimate icehouse and its imprint on the Upper Devonian through Permian stratigraphic record |url=https://www.lyellcollection.org/doi/10.1144/SP512-2021-124 |journal=Geological Society, London, Special Publications |language=en |volume=512 |issue=1 |pages=213–245 |doi=10.1144/SP512-2021-124 |issn=0305-8719}}</ref> leads to change in woodland vegetation ([[Carboniferous rainforest collapse]]).<ref>{{Cite journal |last=Lucas |first=Spencer G. |last2=DiMichele |first2=William A. |last3=Opluštil |first3=Stanislav |last4=Wang |first4=Xiangdong |date=2023-06-14 |title=An introduction to ice ages, climate dynamics and biotic events: the Late Pennsylvanian world |url=https://www.lyellcollection.org/doi/full/10.1144/SP535-2022-334 |journal=Geological Society, London, Special Publications |volume=535 |issue=1 |pages=1–15 |doi=10.1144/SP535-2022-334}}</ref>
| 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}}<sup>*</sup>
|-
| rowspan="3" style="background:{{period color|Mississippian}}" |[[Mississippian (geology)|Mississippian]]<br/>{{efn|group=note|name=MissiPenns}}
| style="background:{{period color|Serpukhovian}}" |[[Serpukhovian]]
| rowspan="3" |Continents form a near circle around the opening [[Paleo-Tethys Ocean]]. Gondwana forms the southern to southwestern margin; Laurussia the west; Siberia, Amuria and Kazakhstania the north; North and South China the northeast; and, Annamia the eastern margin.<ref name=":2" /> The [[Armorican terrane|Armorican terrane]]s collide with southeastern Laurussia during the Variscan orogeny. [[Antler orogeny]] continues, and opening of the [[Slide Mountain Ocean]] along western margin of Laurussia.<ref>{{Cite journal |last=Domeier |first=Mathew |last2=Torsvik |first2=Trond H. |date=2014-05-01 |title=Plate tectonics in the late Paleozoic |url=https://www.sciencedirect.com/science/article/pii/S1674987114000061 |journal=Geoscience Frontiers |volume=5 |issue=3 |pages=303–350 |doi=10.1016/j.gsf.2014.01.002 |issn=1674-9871}}</ref> Closure of [[Ural Ocean]] between Kazakhstania and Laurussia during the Ural orogeny. Development of [[Altai Mountains|Altai]] accretionary complexes along north and eastern margin of the Paleo-Tethys.<ref>{{Cite journal |last=Xu |first=Yan |last2=Han |first2=Bao-Fu |last3=Liao |first3=Wen |last4=Li |first4=Ang |date=2022 |title=The Serpukhovian–Bashkirian Amalgamation of Laurussia and the Siberian Continent and Implications for Assembly of Pangea |url=https://onlinelibrary.wiley.com/doi/abs/10.1029/2022TC007218 |journal=Tectonics |language=en |volume=41 |issue=3 |pages=e2022TC007218 |doi=10.1029/2022TC007218 |issn=1944-9194}}</ref> Main phase of LPIA begins. Drop in global sea levels, extensive glaciation across Gondwana.<ref name=":9" /> Increasing atmospheric oxygen levels.<ref name=":7" /> Change from [[Calcite sea|calcite]] to [[Aragonite sea|aragonite seas]].<ref name=":1" /> [[Evolutionary radiation|Evolutionary radiations]] after the Late Devonian extinctions include brachiopods, bivalves, echinoderms, ammonoids, gastropods, sharks and ray-finned bony fish. [[Placoderm|Placoderm]]s and [[Graptolite|graptolite]]s die out. Proetida only group of trilobites.<ref name=":1" /><ref name=":8" /> First freshwater mollusks and sharks.<ref name=":1" /> ''[[Arthropleura]]'' (millipede) largest ever terrestrial arthropod. First flying insects ''[[Palaeodictyoptera|Paleodictyopora]].'' Fish-like (''[[Pederpes]]'') and semi-aquatic tetrapods (''[[Eucritta]]'') appear on land.<ref name=":8" /> Seedless vascular plants and seed ferns diversify.<ref name=":1" />
| 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}}<sup>*</sup>
|-
| style="background:{{period color|Tournaisian}}" |[[Tournaisian]]
| style="background:{{period color|Tournaisian}}" |{{Period start|tournaisian}} {{Period start error|tournaisian}}<sup>*</sup>
|-
| rowspan="7" style="background:{{period color|Devonian}}" |[[Devonian]]
| rowspan="2" style="background:{{period color|Late Devonian}}" |[[Late Devonian|Upper/Late]]
| style="background:{{period color|Famennian}}" |[[Famennian]]
| rowspan="7" |Paleo-Tethys continues to open as the Armorican Terrane Assemblage (ATA) drifts north and Annamia-South China moves away from Gondwana.<ref name=":2" /><ref>{{Cite journal |last=Golonka |first=Jan |date=2020 |title=Late Devonian paleogeography in the framework of global plate tectonics |url=https://www.sciencedirect.com/science/article/pii/S0921818120300187 |journal=Global and Planetary Change |volume=186 |article-number=103129 |doi=10.1016/j.gloplacha.2020.103129 |bibcode=2020GPC...18603129G |issn=0921-8181}}</ref> [[Rheic Ocean]] closes as ATA collides with Laurussia beginning the Variscan orogeny. Other orogenies: Antler, [[Innuitian orogeny|Ellesmerian]], and [[Acadian orogeny|Acadian]] (Laurussia); Achalian (Argentina); [[Lachlan Fold Belt|Tabberabberan/Lachlan]] (Australia); [[Ross orogeny|Ross]] (Antarctica); Kazakh ([[Kazakhstania]]).<ref name=":2" /> Period of high sea-levels, greenhouse conditions but decreasing atmospheric CO<sub>2</sub> levels and slowly cooling climate with glaciations towards end.<ref name=":6">{{Cite journal |last1=Qie |first1=Wenkun |last2=Algeo |first2=Thomas J. |last3=Luo |first3=Genming |last4=Herrmann |first4=Achim |date=2019 |title=Global events of the Late Paleozoic (Early Devonian to Middle Permian): A review |url=https://www.sciencedirect.com/science/article/pii/S003101821930625X |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |series=Global events of the Late Devonian to Early Permian |volume=531 |article-number=109259 |doi=10.1016/j.palaeo.2019.109259 |bibcode=2019PPP...53109259Q |issn=0031-0182}}</ref> [[Vascular plant]]s increase in size, develop large root systems and spread to upland areas. First forests, seed plants, and modern soil orders appear ([[alfisol]]s and [[ultisol]]s).<ref name=":6" /> Growth of massive reef systems. Major radiation of [[Gnathostomata|jawed fish]] with appearance of [[Actinopterygii|ray-finned]], [[Sarcopterygii|lobe-finned]], and [[Chondrichthyes|cartilaginous]] fish. Appearance of [[tetrapod]]s (evolved from lobe-finned fish). Early amphibians move on to land. First ammonoids.<ref name=":1" /> Emplacement of the Viley and Pripyat–Dniepr–Donets [[Large igneous province|large igneous provinces]] coincide with global marine [[anoxic event]]s and the [[Late Devonian mass extinction|Kellwasser]] (c. 372 Ma) and [[Hangenberg event|Hangenberg]] (c. 359 Ma) mass extinctions.<ref name=":6" /> Kellwasser extinction: c. 20% of families and c. 50% of genera of marine invertebrates lost. [[Tabulata|Tabulate coral]] and [[Stromatoporoidea|stromatoporoid]] reef ecosystems wiped out. Loss of placoderms and many groups of [[Agnatha|jawless fish]]. Hangenberg extinction: loss of c. 16% of marine families and c. 21% of marine genera, including ammonoids, [[ostracod]]s and sharks.<ref name=":6" /><ref>{{Cite journal |last1=Ernst |first1=Richard E. |last2=Rodygin |first2=Sergei A. |last3=Grinev |first3=Oleg M. |date=2020 |title=Age correlation of Large Igneous Provinces with Devonian biotic crises |url=https://www.sciencedirect.com/science/article/pii/S092181811930582X |journal=Global and Planetary Change |volume=185 |article-number=103097 |doi=10.1016/j.gloplacha.2019.103097 |bibcode=2020GPC...18503097E |issn=0921-8181}}</ref>

| style="background:{{period color|Famennian}}" |{{Period start|famennian}} {{Period start error|famennian}}<sup>*</sup>
|-
| style="background:{{period color|Frasnian}}" |[[Frasnian]]
| style="background:{{period color|Frasnian}}" |{{Period start|frasnian}} {{Period start error|frasnian}}<sup>*</sup>
|-
| rowspan="2" style="background:{{period color|Middle Devonian}}" |[[Middle Devonian|Middle]]
| style="background:{{period color|Givetian}}" |[[Givetian]]
| style="background:{{period color|Givetian}}" |{{Period start|givetian}} {{Period start error|givetian}}<sup>*</sup>
|-
| style="background:{{period color|Eifelian}}" |[[Eifelian]]
| style="background:{{period color|Eifelian}}" |{{Period start|eifelian}} {{Period start error|eifelian}}<sup>*</sup>
|-
| rowspan="3" style="background:{{period color|Early Devonian}}" |[[Early Devonian|Lower/Early]]
| style="background:{{period color|Emsian}}" |[[Emsian]]
| style="background:{{period color|Emsian}}" |{{Period start|emsian}} {{Period start error|emsian}}<sup>*</sup>
|-
| style="background:{{period color|Pragian}}" |[[Pragian]]
| style="background:{{period color|Pragian}}" |{{Period start|pragian}} {{Period start error|pragian}}<sup>*</sup>
|-
| style="background:{{period color|Lochkovian}}" |[[Lochkovian]]
| style="background:{{period color|Lochkovian}}" |{{Period start|lochkovian}} {{Period start error|lochkovian}}<sup>*</sup>
|-
| rowspan="8" style="background:{{period color|Silurian}}" |[[Silurian]]
| colspan="2" style="background:{{period color|Pridoli}}" |[[Pridoli epoch|Pridoli]]
| rowspan="8" |Laurentia and Avalonia-Baltica collide as Iapetus Ocean closes, [[Caledonian orogeny|Caledonian]]-[[Scandian orogeny|Scandian]] orogeny, and formation of [[Laurasia|Laurussia]]. Other orogenies: Salinic (Appalachians); Famatinian (South America) tapers off; [[Lachlan Fold Belt|Lachlan]] (Australia).<ref name=":2" /><ref name=":5">{{Cite journal |last1=Golonka |first1=Jan |last2=Porębski |first2=Szczepan J. |last3=Waśkowska |first3=Anna |date=2023-07-15 |title=Silurian paleogeography in the framework of global plate tectonics |url=https://www.sciencedirect.com/science/article/pii/S0031018223002158 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=622 |article-number=111597 |doi=10.1016/j.palaeo.2023.111597 |bibcode=2023PPP...62211597G |issn=0031-0182}}</ref> Series of microcontinents and North China separate opening Paleo-Tethys and closing Paleoasian Ocean.<ref name=":5" /> Rheic Ocean widens between Gondwana and Laurussia. Siberia drifts north of equator.<ref name=":2" /> Temperatures increase as Hirnantian glaciation ends. Sea levels rise. Deposition of black shales, North Africa and Arabia, major [[hydrocarbon]] [[source rock]]s.<ref name=":2" /> Fluctuating climate with glacial advances results in changing ocean conditions causes extinction events, followed by ecological recoveries.<ref>{{Cite journal |last1=Cooper |first1=Roger A. |last2=Sadler |first2=Peter M. |last3=Munnecke |first3=Axel |last4=Crampton |first4=James S. |date=2014 |title=Graptoloid evolutionary rates track Ordovician–Silurian global climate change |url=https://www.cambridge.org/core/journals/geological-magazine/article/abs/graptoloid-evolutionary-rates-track-ordoviciansilurian-global-climate-change/6E1711BC6768CE8FFE72BD02E19FD72B |journal=Geological Magazine |language=en |volume=151 |issue=2 |pages=349–364 |doi=10.1017/S0016756813000198 |bibcode=2014GeoM..151..349C |issn=0016-7568}}</ref> Widespread evaporite deposition and hothouse climate by late Silurian.<ref name=":1" /><ref>{{Cite journal |last1=Scotese |first1=Christopher R. |last2=Song |first2=Haijun |last3=Mills |first3=Benjamin J. W. |last4=van der Meer |first4=Douwe G. |date=2021-04-01 |title=Phanerozoic paleotemperatures: The earth's changing climate during the last 540 million years |url=https://www.sciencedirect.com/science/article/pii/S0012825221000027 |journal=Earth-Science Reviews |volume=215 |article-number=103503 |doi=10.1016/j.earscirev.2021.103503 |bibcode=2021ESRv..21503503S |issn=0012-8252}}</ref> After end-Ordovician mass extinction, major radiation of graptolites, bivalves, gastropods, nautiloids, brachiopods, and crinoids. Increase in trilobites, but never fully recover. Corals and stromatoporiods diversify to produce large reefs. Proliferation of eurypterid arthropods. Earliest jawed fish ([[Acanthodii|acanthodians]]). Appearance of [[ostracoderm]]s. Appearance of [[vascular plant]]s. First land animals including [[Myriapoda|myriapods]]. First freshwater fish.<ref name=":1" />
| style="background:{{period color|Pridoli}}" |{{Period start|pridoli}} {{Period start error|pridoli}}<sup>*</sup>
|-
| rowspan="2" style="background:{{period color|Ludlow}}" |[[Ludlow epoch|Ludlow]]
| style="background:{{period color|Ludfordian}}" |[[Ludfordian]]
| style="background:{{period color|Ludfordian}}" |{{Period start|ludfordian}} {{Period start error|ludfordian}}<sup>*</sup>
|-
| style="background:{{period color|Gorstian}}" |[[Gorstian]]
| style="background:{{period color|Gorstian}}" |{{Period start|gorstian}} {{Period start error|gorstian}}<sup>*</sup>
|-
| rowspan="2" style="background:{{period color|Wenlock}}" |[[Wenlock epoch|Wenlock]]
| style="background:{{period color|Homerian}}" |[[Homerian]]
| style="background:{{period color|Homerian}}" |{{Period start|homerian}} {{Period start error|homerian}}<sup>*</sup>
|-
| style="background:{{period color|Sheinwoodian}}" |[[Sheinwoodian]]
| style="background:{{period color|Sheinwoodian}}" |{{Period start|sheinwoodian}} {{Period start error|sheinwoodian}}<sup>*</sup>
|-
| rowspan="3" style="background:{{period color|Llandovery}}" |[[Llandovery epoch|Llandovery]]
| style="background:{{period color|Telychian}}" |[[Telychian]]
| style="background:{{period color|Telychian}}" |{{Period start|telychian}} {{Period start error|telychian}}<sup>*</sup>
|-
| style="background:{{period color|Aeronian}}" |[[Aeronian]]
| style="background:{{period color|Aeronian}}" |{{Period start|aeronian}} {{Period start error|aeronian}}<sup>*</sup>
|-
| style="background:{{period color|Rhuddanian}}" |[[Rhuddanian]]
| style="background:{{period color|Rhuddanian}}" |{{Period start|rhuddanian}} {{Period start error|rhuddanian}}<sup>*</sup>
|-
| rowspan="7" style="background:{{period color|Ordovician}}" |[[Ordovician]]
| rowspan="3" style="background:{{period color|Late Ordovician}}" |[[Late Ordovician|Upper/Late]]
| style="background:{{period color|Hirnantian}}" |[[Hirnantian]]
| rowspan="7" |Most continents lay in equatorial regions. Gondwana stretched to south pole. Panthalassic Ocean covered northern hemisphere. Avalonia rifted from Gondwana closing Iapetus Ocean in front, opening Rheic Ocean behind. South China close to Gondwana; North China between Siberia and Gondwana. Orogenies: [[Famatinian orogeny|Famatinian]] (South America); Benambran (Australia); [[Taconic orogeny|Taconic]] (Laurentia). Baltica and Siberia drift north.<ref name=":2" /> Early greenhouse climate, cooling to icehouse conditions during [[Hirnantian glaciation|Hirnantian Ice Age]]. Increase in atmospheric O<sub>2</sub>.<ref name=":3">{{Cite journal |last1=Liu |first1=Mu |last2=Bao |first2=Xiujuan |last3=Harper |first3=David A. T. |last4=Algeo |first4=Thomas |last5=Zhao |first5=Mingyu |last6=Saltzman |first6=Matthew |last7=Zhang |first7=Wang |last8=Chen |first8=Daizhao |last9=Yuan |first9=Shuai |last10=Chen |first10=Yihui |last11=Wei |first11=Mengyu |last12=Zhang |first12=Junpeng |last13=Luan |first13=Xiaocong |last14=Zhang |first14=Yuandong |last15=Yang |first15=Xiangrong |date=2025-10-01 |title=Diversification to extinction: oceanic and climatic context of the Ordovician |url=https://www.sciencedirect.com/science/article/pii/S0012825225001552 |journal=Earth-Science Reviews |volume=269 |article-number=105194 |doi=10.1016/j.earscirev.2025.105194 |bibcode=2025ESRv..26905194L |issn=0012-8252}}</ref> [[Great Ordovician Biodiversification Event]], major increase in new genera e.g. brachiopods, trilobites, corals, echinoderms, bryozoans, gastropods, bivalves, nautiloids, graptolites, and conodonts. Very high sea levels expand shallow continental seas, increase range of ecological niches.<ref name=":4">{{Citation |last1=Cooper |first1=R. A. |title=Chapter 20 - The Ordovician Period |date=2012-01-01 |work=The Geologic Time Scale |pages=489–523 |editor-last=Gradstein |editor-first=Felix M. |url=https://www.sciencedirect.com/science/article/pii/B9780444594259000202 |access-date=2025-07-30 |place=Boston |publisher=Elsevier |isbn=978-0-444-59425-9 |last2=Sadler |first2=P. M. |last3=Hammer |first3=O. |last4=Gradstein |first4=F. M. |editor2-last=Ogg |editor2-first=James G. |editor3-last=Schmitz |editor3-first=Mark D. |editor4-last=Ogg |editor4-first=Gabi M.}}</ref> Modern marine ecosystems established.<ref name=":3" /> Earliest jawless fish. Tabulate corals and stromatoporoids dominant reef builders. Nautiloids main predators.<ref name=":1" /> Appearance of eurypterids and asteroids. Spread of early land plants.<ref name=":3" /> [[Late Ordovician mass extinction|Late Ordovician Mass Extinction]], loss of ~85 % of marine invertebrate species. Two pulses: first with onset of glaciation affects tropical fauna; second at end of ice age, warming climate impacts cool water species.<ref name=":1" /> Drastic reduction in trilobite, brachiopod, graptolite, echinoderm, conodont, coral, and chitinozoan genera.<ref name=":4" />
| style="background:{{period color|Hirnantian}}" |{{Period start|hirnantian}} {{Period start error|hirnantian}}<sup>*</sup>
|-
| style="background:{{period color|Katian}}" |[[Katian]]
| style="background:{{period color|Katian}}" |{{Period start|katian}} {{Period start error|katian}}<sup>*</sup>
|-
| style="background:{{period color|Sandbian}}" |[[Sandbian]]
| style="background:{{period color|Sandbian}}" |{{Period start|sandbian}} {{Period start error|sandbian}}<sup>*</sup>
|-
| rowspan="2" style="background:{{period color|Middle Ordovician}}" |[[Middle Ordovician|Middle]]
| style="background:{{period color|Darriwilian}}" |[[Darriwilian]]
| style="background:{{period color|Darriwilian}}" |{{Period start|darriwilian}} {{Period start error|darriwilian}}<sup>*</sup>
|-
| style="background:{{period color|Dapingian}}" |[[Dapingian]]
| style="background:{{period color|Dapingian}}" |{{Period start|dapingian}} {{Period start error|dapingian}}<sup>*</sup>
|-
| rowspan="2" style="background:{{period color|Early Ordovician}}" |[[Early Ordovician|Lower/Early]]
| style="background:{{period color|Floian}}" |[[Floian]]<br />(formerly [[Arenig]])
| style="background:{{period color|Floian}}" |{{Period start|floian}} {{Period start error|floian}}<sup>*</sup>
|-
| style="background:{{period color|Tremadocian}}" |[[Tremadocian]]
| style="background:{{period color|Tremadocian}}" |{{Period start|tremadocian}} {{Period start error|tremadocian}}<sup>*</sup>
|-
| rowspan="10" style="background:{{period color|Cambrian}}" |[[Cambrian]]
| rowspan="3" style="background:{{period color|Furongian}}" |[[Furongian]]
| style="background:{{period color|Stage 10}}" |[[Cambrian Stage 10|Stage 10]]
| rowspan="10" |Gondwana stretched from the south pole to equator, separated from Laurentia and Baltica by the Iapetus Ocean. Siberia lay close to the equator, north of Baltica; North and South China close to equatorial Gondwana. Orogenies: [[Cadomian Orogeny|Cadomian]] (N.Africa/southern Europe); [[Kuunga orogeny|Kuunga]] (central Gondwana); [[Famatinian orogeny|Famatinian]] orogeny (South America); [[Adelaide Superbasin|Delamerian]] (Australia).<ref>{{Cite book |last1=Torsvik |first1=Trond H. |title=Earth history and palaeogeography |last2=Cocks |first2=Leonard Robert Morrison |date=2017 |publisher=Cambridge university press |isbn=978-1-107-10532-4 |location=Cambridge}}</ref> Greenhouse climate. High atmospheric CO<sub>2</sub> levels. Atmospheric oxygen levels rose with increase in photosynthesising organisms.<ref name=":0">{{Cite journal |last1=Pruss |first1=Sara B. |last2=Gill |first2=Benjamin C. |date=2024-07-23 |title=Life on the Edge: The Cambrian Marine Realm and Oxygenation |url=https://www.annualreviews.org/content/journals/10.1146/annurev-earth-031621-070316 |journal=Annual Review of Earth and Planetary Sciences |language=en |volume=52 |issue=52 |pages=109–132 |doi=10.1146/annurev-earth-031621-070316 |bibcode=2024AREPS..52..109P |issn=0084-6597}}</ref> Early aragonite seas replaced by mixed aragonite-calcite seas with many animals developing CaCO<sub>3</sub> skeletons.<ref>{{Cite journal |last1=Xiong |first1=Yi |last2=Wood |first2=Rachel |last3=Pichevin |first3=Laetitia |date=2023 |title=The record of sea water chemistry evolution during the Ediacaran–Cambrian from early marine cements |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/dep2.211 |journal=The Depositional Record |language=en |volume=9 |issue=3 |pages=508–525 |doi=10.1002/dep2.211 |bibcode=2023DepRe...9..508X |issn=2055-4877}}</ref> Rapid diversification of animals ([[Cambrian explosion|Cambrian Explosion]]), most modern animal phyla appear, e.g. arthropods; molluscs; annelids; echinoderms; bryozoa; priapulids; brachiopods; hemichordates; and, chordates. Radiations of [[Small shelly fauna|small shelly fossils]].<ref>{{Citation |last1=Peng |first1=S. |title=Chapter 19 - The Cambrian Period |date=2012-01-01 |work=The Geologic Time Scale |pages=437–488 |editor-last=Gradstein |editor-first=Felix M. |url=https://www.sciencedirect.com/science/article/pii/B9780444594259000196 |access-date=2025-07-30 |place=Boston |publisher=Elsevier |isbn=978-0-444-59425-9 |last2=Babcock |first2=L. E. |last3=Cooper |first3=R. A. |editor2-last=Ogg |editor2-first=James G. |editor3-last=Schmitz |editor3-first=Mark D. |editor4-last=Ogg |editor4-first=Gabi M.}}</ref> Giant [[Anomalocarididae|anomalocarids]] (arthropods) dominant predators. Increase in bioturbation and grazing led to decline in [[stromatolite]]s.<ref name=":1">{{Cite book |last1=Stanley |first1=Steven |title=Earth System Science |last2=Luczaj |first2=John |publisher=W.H.Freeman and Company |year=2015 |isbn=978-1-319-15402-8 |edition=4th |location=New York}}</ref> Varying oxygen levels in oceans led to series of extinction events followed by radiations, including: earliest Cambrian loss of the Ediacaran [[acritarch]]s; [[End-Botomian mass extinction|end-Botomian extinction]], linked to the Kalkarindji [[Large igneous province|Large Igneous Province]] eruptions (c. 514 Ma) with loss of [[Archaeocyatha|archaeocyathids]] (early Cambrian reef builders) and hyoliths; and, end-Cambrian reduction in trilobite diversity.<ref name=":0" /><ref>{{Cite journal |last1=Myrow |first1=Paul M. |last2=Goodge |first2=John W. |last3=Brock |first3=Glenn A. |last4=Betts |first4=Marissa J. |last5=Park |first5=Tae-Yoon S. |last6=Hughes |first6=Nigel C. |last7=Gaines |first7=Robert R. |date=2024-03-29 |title=Tectonic trigger to the first major extinction of the Phanerozoic: The early Cambrian Sinsk event |journal=Science Advances |volume=10 |issue=13 |article-number=eadl3452 |doi=10.1126/sciadv.adl3452 |issn=2375-2548 |pmc=10980278 |pmid=38552008 |bibcode=2024SciA...10L3452M }}</ref><ref name=":1" /> Many fossil [[lagerstätte]]n, including [[Burgess Shale]] and [[Maotianshan Shales|Chengjiang Formation]], formed by rapid burial in anoxic conditions.<ref name=":0" />
| style="background:{{period color|Stage 10}}" |~{{Period start|cambrian stage 10}}
|-
| style="background:{{period color|Jiangshanian}}" |[[Jiangshanian]]
| style="background:{{period color|Jiangshanian}}" |~{{Period start|Jiangshanian}} {{Period start error|Jiangshanian}}<sup>*</sup>
|-
| style="background:{{period color|Paibian}}" |[[Paibian]]
| style="background:{{period color|Paibian}}" |~{{Period start|paibian}} {{Period start error|paibian}}<sup>*</sup>
|-
| rowspan="3" style="background:{{period color|Series 3}}" |[[Miaolingian]]
| style="background:{{period color|Guzhangian}}" |[[Guzhangian]]
| style="background:{{period color|Guzhangian}}" |~{{Period start|guzhangian}} {{Period start error|guzhangian}}<sup>*</sup>
|-
| style="background:{{period color|Drumian}}" |[[Drumian]]
| style="background:{{period color|Drumian}}" |~{{Period start|drumian}} {{Period start error|drumian}}<sup>*</sup>
|-
| style="background:{{period color|Stage 5}}" |[[Wuliuan]]
| style="background:{{period color|Stage 5}}" |~{{Period start|wuliuan}} {{Period start error|wuliuan}}
|-
| rowspan="2" style="background:{{period color|Series 2}}" |[[Cambrian Series 2|Series 2]]
| style="background:{{period color|Stage 4}}" |[[Cambrian Stage 4|Stage 4]]
| style="background:{{period color|Stage 4}}" |~{{Period start|cambrian stage 4}} {{Period start error|cambrian stage 4}}
|-
| style="background:{{period color|Stage 3}}" |[[Cambrian Stage 3|Stage 3]]
| style="background:{{period color|Stage 3}}" |~{{Period start|cambrian stage 3}} {{Period start error|cambrian stage 3}}
|-
| rowspan="2" style="background:{{period color|Terreneuvian}}" |[[Terreneuvian]]
| style="background:{{period color|Stage 2}}" |[[Cambrian Stage 2|Stage 2]]
| style="background:{{period color|Stage 2}}" |~{{Period start|cambrian stage 2}} {{Period start error|cambrian stage 2}}
|-
| style="background:{{period color|Fortunian}}" |[[Fortunian]]
| style="background:{{period color|Fortunian}}" |{{Period start|fortunian}} {{Period start error|fortunian}}<sup>*</sup>
|-
| rowspan="10" style="background:{{period color|Proterozoic}}" |[[Proterozoic]]
| rowspan="3" style="background:{{period color|Neoproterozoic}}" |[[Neoproterozoic]]
| style="background:{{period color|Ediacaran}}" |[[Ediacaran]]
| colspan="3" |Good [[fossil]]s of primitive [[animal]]s. [[Ediacaran biota]] flourish worldwide in seas, possibly appearing after an [[Avalon explosion|explosion]], possibly caused by a large-scale oxidation event.<ref name="Williams_2019">{{Cite journal |last1=Williams |first1=Joshua J. |last2=Mills |first2=Benjamin J. W. |last3=Lenton |first3=Timothy M. |date=2019 |title=A tectonically driven Ediacaran oxygenation event |journal=Nature Communications |language=en |volume=10 |issue=1 |page=2690 |doi=10.1038/s41467-019-10286-x |issn=2041-1723 |pmc=6584537 |pmid=31217418|bibcode=2019NatCo..10.2690W }}</ref> First [[vendozoa]]ns (unknown affinity among animals), [[cnidaria]]ns and [[bilateria]]ns. Enigmatic vendozoans include many soft-jellied creatures shaped like bags, disks, or quilts (like ''[[Dickinsonia]]''). Simple [[trace fossil]]s of possible worm-like ''[[Trichophycus pedum|Trichophycus]]'', etc. [[Taconic Orogeny]] in North America. [[Aravalli Range]] [[orogeny]] in [[Indian subcontinent]]. Beginning of [[Pan-African Orogeny]], leading to the formation of the short-lived Ediacaran supercontinent [[Pannotia]], which by the end of the period breaks up into [[Laurentia]], [[Baltica]], [[Siberia (continent)|Siberia]] and [[Gondwana]]. [[Petermann Orogeny]] forms on [[Australia (continent)|Australian continent]]. Beardmore Orogeny in Antarctica, 633–620&nbsp;Ma. [[Ozone layer]] forms. An increase in oceanic [[mineral]] levels.
| style="background:{{period color|Ediacaran}}" |~{{Period start|ediacaran}} {{Period start error|ediacaran}}<sup>*</sup>
|-
| style="background:{{period color|Cryogenian}}" |[[Cryogenian]]
| colspan="3" |Possible "[[Snowball Earth]]" period. [[Fossil]]s still rare. Late Ruker / Nimrod Orogeny in Antarctica tapers off. First uncontroversial [[Sponge|animal]] fossils. First hypothetical [[Amastigomycota|terrestrial fungi]]<ref name="NaranjoOrtiz_2019">{{cite journal |last1=Naranjo-Ortiz |first1=Miguel A. |last2=Gabaldón |first2=Toni |date=2019-04-25 |title=Fungal evolution: major ecological adaptations and evolutionary transitions |journal=[[Biological Reviews of the Cambridge Philosophical Society]] |publisher=[[Cambridge Philosophical Society]] ([[Wiley Publishing|Wiley]]) |volume=94 |issue=4 |pages=1443–1476 |doi=10.1111/brv.12510 |pmid=31021528 |pmc=6850671 |s2cid=131775942 |issn=1464-7931}}</ref> and [[streptophyta]].<ref name="Zarsky_2022">{{Cite journal |last1=Žárský |first1=Jakub |last2=Žárský |first2=Vojtěch |last3=Hanáček |first3=Martin |last4=Žárský |first4=Viktor |date=2022-01-27 |title=Cryogenian Glacial Habitats as a Plant Terrestrialisation Cradle – The Origin of the Anydrophytes and Zygnematophyceae Split |journal=Frontiers in Plant Science |volume=12 |article-number=735020 |doi=10.3389/fpls.2021.735020 |issn=1664-462X |pmc=8829067 |pmid=35154170|bibcode=2022FrPS...1235020Z |doi-access=free }}</ref>
| style="background:{{period color|Cryogenian}}" |~{{Period start|cryogenian}} {{Period start error|cryogenian}}
|-
| style="background:{{period color|Tonian}}" |[[Tonian]]
| colspan="3" |Final assembly of [[Rodinia]] supercontinent occurs in early Tonian, with breakup beginning c. 800&nbsp;Ma. [[Sveconorwegian orogeny]] ends. [[Grenville Orogeny]] tapers off in North America. Lake Ruker / Nimrod Orogeny in Antarctica, 1,000&nbsp;±&nbsp;150&nbsp;Ma. Edmundian Orogeny (c. 920–850&nbsp;Ma), [[Gascoyne Complex]], Western Australia. Deposition of [[Adelaide Superbasin]] and [[Centralian Superbasin]] begins on [[Australia (continent)|Australian continent]]. First hypothetical [[animals]] (from holozoans) and terrestrial algal mats. Many endosymbiotic events concerning red and green algae occur, transferring plastids to [[ochrophyta]] (e.g. [[diatoms]], [[brown algae]]), [[dinoflagellate]]s, [[cryptophyta]], [[haptophyta]], and [[euglenid]]s (the events may have begun in the Mesoproterozoic)<ref name="Yoon_2004">{{Cite journal |last1=Yoon |first1=Hwan Su |last2=Hackett |first2=Jeremiah D. |last3=Ciniglia |first3=Claudia |last4=Pinto |first4=Gabriele |last5=Bhattacharya |first5=Debashish |date=2004 |title=A Molecular Timeline for the Origin of Photosynthetic Eukaryotes |url=https://academic.oup.com/mbe/article-lookup/doi/10.1093/molbev/msh075 |journal=Molecular Biology and Evolution |language=en |volume=21 |issue=5 |pages=809–818 |doi=10.1093/molbev/msh075 |pmid=14963099 |issn=1537-1719|doi-access=free }}</ref> while the first [[retaria]]ns (e.g. [[forams]]) also appear: eukaryotes diversify rapidly, including algal, eukaryovoric and [[Biomineralization|biomineralised]] forms. [[Trace fossil]]s of simple [[Multicellular|multi-celled]] eukaryotes. [[Neoproterozoic oxygenation event]] (NOE), 850–540 Ma.<ref>{{Cite journal |last1=Och |first1=Lawrence M. |last2=Shields-Zhou |first2=Graham A. |date=2012-01-01 |title=The Neoproterozoic oxygenation event: Environmental perturbations and biogeochemical cycling |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825211001498 |journal=Earth-Science Reviews |language=en |volume=110 |issue=1–4 |pages=26–57 |doi=10.1016/j.earscirev.2011.09.004 |bibcode=2012ESRv..110...26O }}</ref>
| style="background:{{period color|Tonian}}" |{{Period start|tonian}} {{Period start error|tonian}}{{efn|name="absolute-age"|Defined by absolute age ([[Global Standard Stratigraphic Age]]).|group=note}}
|-
| rowspan="3" style="background:{{period color|Mesoproterozoic}}" |[[Mesoproterozoic]]
| style="background:{{period color|Stenian}}" |[[Stenian]]
| colspan="3" |Narrow highly [[Metamorphic rock|metamorphic]] belts due to [[orogeny]] as [[Rodinia]] forms, surrounded by the [[Pan-African Ocean]]. [[Sveconorwegian orogeny]] starts. Late Ruker / Nimrod Orogeny in Antarctica possibly begins. Musgrave Orogeny (c. 1,080–), [[Musgrave Block]], [[Central Australia]]. [[Stromatolite]]s decline as [[algae]] proliferate.
| style="background:{{period color|Stenian}}" |{{Period start|stenian}} {{Period start error|stenian}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Ectasian}}" |[[Ectasian]]
| colspan="3" |[[Platform cover]]s continue to expand. [[Alga]]l [[Colony (biology)|colonies]] in the seas. [[Grenville Orogeny]] in North America. Columbia breaks up.
| style="background:{{period color|Ectasian}}" |{{Period start|ectasian}} {{Period start error|ectasian}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Calymmian}}" |[[Calymmian]]
| colspan="3" |[[Platform cover]]s expand. Barramundi Orogeny, [[McArthur Basin]], [[Northern Australia]], and Isan Orogeny, {{circa}} 1,600&nbsp;Ma, Mount Isa Block, Queensland. First [[archaeplastida]]ns (the first eukaryotes with [[plastids]] from cyanobacteria; e.g. [[Red algae|red]] and [[green algae]]) and [[opisthokonts]] (giving rise to the first [[fungi]] and [[holozoa]]ns). [[Acritarch]]s (remains of marine algae possibly) start appearing in the fossil record.
| style="background:{{period color|Calymmian}}" |{{Period start|calymmian}} {{Period start error|calymmian}}{{efn|name="absolute-age"|group=note}}
|-
| rowspan="4" style="background:{{period color|Paleoproterozoic}}" |[[Paleoproterozoic]]
| style="background:{{period color|Statherian}}" |[[Statherian]]
| colspan="3" |First uncontroversial [[eukaryotes]]: [[protist]]s with nuclei and endomembrane system. [[Columbia (supercontinent)|Columbia]] forms as the second undisputed earliest supercontinent. Kimban Orogeny in Australian continent ends. Yapungku Orogeny on [[Yilgarn craton]], in Western Australia. Mangaroon Orogeny, 1,680–1,620&nbsp;Ma, on the [[Gascoyne Complex]] in Western Australia. Kararan Orogeny (1,650&nbsp;Ma), Gawler craton, [[South Australia]]. Oxygen levels drop again.
| style="background:{{period color|Statherian}}" |{{Period start|statherian}} {{Period start error|statherian}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Orosirian}}" |[[Orosirian]]
| colspan="3" |The [[Atmosphere of Earth|atmosphere]] becomes much more [[oxygen]]ic while more cyanobacterial stromatolites appear. [[Vredefort impact structure|Vredefort]] and [[Sudbury Basin]] asteroid impacts. Much [[orogeny]]. [[Penokean orogeny|Penokean]] and [[Trans-Hudsonian Orogeny|Trans-Hudsonian Orogenies]] in North America. Early Ruker Orogeny in Antarctica, 2,000–1,700&nbsp;Ma. Glenburgh Orogeny, [[Gascoyne Complex|Glenburgh Terrane]], [[Australia (continent)|Australian continent]] {{circa}} 2,005–1,920&nbsp;Ma. Kimban Orogeny, [[Gawler craton]] in Australian continent begins.
| style="background:{{period color|Orosirian}}" |{{Period start|orosirian}} {{Period start error|orosirian}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Rhyacian}}" |[[Rhyacian]]
| colspan="3" |[[Bushveld Igneous Complex]] forms. [[Huronian]] glaciation. First hypothetical [[eukaryote]]s. Multicellular [[Francevillian biota]]. Kenorland disassembles.
| style="background:{{period color|Rhyacian}}" |{{Period start|rhyacian}} {{Period start error|rhyacian}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Siderian}}" |[[Siderian]]
| colspan="3" |[[Great Oxidation Event]] (due to [[cyanobacteria]]) increases oxygen. Sleaford Orogeny on [[Australia (continent)|Australian continent]], [[Gawler craton]] 2,440–2,420&nbsp;Ma.
| style="background:{{period color|Siderian}}" |{{Period start|siderian}} {{Period start error|siderian}}{{efn|name="absolute-age"|group=note}}
|-
| rowspan="4" style="background:{{period color|Archean}}" |[[Archean]]
| style="background:{{period color|Neoarchean}}" |[[Neoarchean]]
| colspan="4" |Stabilization of most modern [[craton]]s; possible [[Mantle (geology)|mantle]] overturn event. Insell Orogeny, 2,650&nbsp;±&nbsp;150&nbsp;Ma. [[Abitibi greenstone belt]] in present-day [[Ontario]] and [[Quebec]] begins to form, stabilises by 2,600&nbsp;Ma. First uncontroversial [[supercontinent]], [[Kenorland]], and first terrestrial [[prokaryotes]].
| style="background:{{period color|Neoarchean}}" |{{Period start|neoarchean}} {{Period start error|neoarchean}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Mesoarchean}}" |[[Mesoarchean]]
| colspan="4" |[[Stromatolite]]s (probably [[Colony (biology)|colonial]] phototrophic bacteria, like cyanobacteria). Oldest [[macrofossil]]s. Humboldt Orogeny in Antarctica. [[Blake River Megacaldera Complex]] begins to form in present-day [[Ontario]] and [[Quebec]], ends by roughly 2,696&nbsp;Ma.
| style="background:{{period color|Mesoarchean}}" |{{Period start|mesoarchean}} {{Period start error|mesoarchean}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Paleoarchean}}" |[[Paleoarchean]]
| colspan="4" |Prokaryotic [[archaea]] (e.g. [[methanogens]]) and [[bacteria]] (e.g. [[cyanobacteria]]) diversify rapidly, along with early [[viruses]]. First known [[phototroph]]ic [[bacteria]]. Oldest definitive [[microfossils]]. First [[microbial mats, stromatolites and MISS]]. Oldest [[craton]]s on Earth (such as the [[Canadian Shield]] and the [[Pilbara craton|Pilbara Craton]]) may have formed during this period.{{efn|The age of the oldest measurable [[craton]], or [[continental crust]], is dated to 3,600–3,800 Ma.|name="Oldest-craton"|group=note}} Rayner Orogeny in Antarctica.
| style="background:{{period color|Paleoarchean}}" |{{Period start|paleoarchean}} {{Period start error|paleoarchean}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Eoarchean}}" |[[Eoarchean]]
| colspan="4" |First uncontroversial [[Life|living organisms]]: at first [[protocell]]s with [[RNA world|RNA-based genes]] around 4000 Ma, after which true [[cell (biology)|cells]] ([[prokaryote]]s) evolve along with [[proteins]] and [[DNA]]-based genes around 3800 Ma. The end of the [[Late Heavy Bombardment]]. [[Napier Mountains|Napier]] Orogeny in Antarctica, 4,000&nbsp;±&nbsp;200&nbsp;Ma.
| style="background:{{period color|Eoarchean}}" |{{Period start|eoarchean}} {{Period start error|eoarchean}}{{efn|name="absolute-age"|group=note}}
|-
| style="background:{{period color|Hadean}}" |[[Hadean]]
| colspan="5" |Formation of [[protolith]] of the oldest known rock ([[Acasta Gneiss]]) c. 4,031 to 3,580 Ma.<ref name="Bowring_1999">{{cite journal |last1=Bowring |first1=Samuel A. |last2=Williams |first2=Ian S. |year=1999 |title=Priscoan (4.00&ndash;4.03 Ga) orthogneisses from northwestern Canada |journal=Contributions to Mineralogy and Petrology |volume=134 |issue=1 |page=3 |bibcode=1999CoMP..134....3B |doi=10.1007/s004100050465 |s2cid=128376754}}</ref><ref name="Iizuka_2007">{{Citation |last1=Iizuka |first1=Tsuyoshi |date=2007 |url=https://linkinghub.elsevier.com/retrieve/pii/S0166263507150313 |volume=15 |pages=127–147 |publisher=Elsevier |language=en |doi=10.1016/s0166-2635(07)15031-3 |isbn=978-0-444-52810-0 |access-date=2022-05-01 |last2=Komiya |first2=Tsuyoshi |last3=Maruyama |first3=Shigenori|title=Chapter 3.1 the Early Archean Acasta Gneiss Complex: Geological, Geochronological and Isotopic Studies and Implications for Early Crustal Evolution |series=Developments in Precambrian Geology }}</ref> Possible first appearance of [[plate tectonic]]s. First hypothetical [[Abiogenesis|life forms]]. End of the Early Bombardment Phase. Oldest known [[mineral]] ([[Zircon]], 4,404&nbsp;±&nbsp;8&nbsp;Ma).<ref name="Wilde_2001">{{Cite journal |last1=Wilde |first1=Simon A. |last2=Valley |first2=John W. |last3=Peck |first3=William H. |last4=Graham |first4=Colin M. |date=2001 |title=Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago |url=http://www.nature.com/articles/35051550 |journal=Nature |language=en |volume=409 |issue=6817 |pages=175–178 |doi=10.1038/35051550 |issn=0028-0836 |pmid=11196637 |bibcode=2001Natur.409..175W |s2cid=4319774}}</ref> Asteroids and comets bring water to Earth, forming the first oceans. Formation of [[Moon]] (4,510 Ma), probably from a [[Giant impact hypothesis|giant impact]]. Formation of Earth (4,543 to 4,540 Ma)
| style="background:{{period color|Hadean}}" |{{Period start|hadean}} {{Period start error|hadean}}{{efn|name="absolute-age"|group=note}}
|}

== Extraterrestrial geologic time scales ==
{{Main|Lunar geologic timescale|Martian geologic timescale|Geology of Venus}}Some other [[Planet#Solar System|planets]] and [[Natural satellite|satellites]] in the [[Solar System]] have sufficiently rigid structures to have preserved records of their own histories, for example, [[Geology of Venus|Venus]], [[Geology of Mars|Mars]] and the Earth's [[Moon]]. Dominantly fluid planets, such as the [[giant planet]]s, do not comparably preserve their history. Apart from the [[Late Heavy Bombardment]], events on other planets probably had little direct influence on the Earth, and events on Earth had correspondingly little effect on those planets. Construction of a time scale that links the planets is, therefore, of only limited relevance to the Earth's time scale, except in a Solar System context. The existence, timing, and terrestrial effects of the Late Heavy Bombardment are still a matter of debate.{{efn|Not enough is known about extra-solar planets for worthwhile speculation.|group=note}}

=== Lunar (selenological) time scale ===
The [[Geology of the Moon|geologic history]] of Earth's Moon has been divided into a time scale based on [[Geomorphology|geomorphological]] markers, namely [[impact crater]]ing, [[volcanism]], and [[erosion]]. This process of dividing the Moon's history in this manner means that the time scale boundaries do not imply fundamental changes in geological processes, unlike Earth's geologic time scale. Five geologic systems/periods ([[Pre-Nectarian]], [[Nectarian]], [[Imbrian]], [[Eratosthenian]], [[Copernican period|Copernican]]), with the Imbrian divided into two series/epochs (Early and Late) were defined in the latest Lunar geologic time scale.<ref name="Wilhelms_1987">{{Cite book |last=Wilhelms |first=Don E. |title=The geologic history of the Moon |series=Professional Paper |publisher=United States Geological Survey |year=1987 |doi=10.3133/pp1348 |bibcode=1987ghm..book.....W }}</ref> The Moon is unique in the Solar System in that it is the only other body from which humans have rock samples with a known geological context.
{{Timeline Lunar Geological Timescale}}

=== Martian geologic time scale ===
The [[geological history of Mars]] has been divided into two alternate time scales. The first time scale for Mars was developed by studying the impact crater densities on the Martian surface. Through this method four periods have been defined, the Pre-Noachian (~4,500–4,100 Ma), Noachian (~4,100–3,700 Ma), Hesperian (~3,700–3,000 Ma), and Amazonian (~3,000 Ma to present).<ref name="Tanaka_1986">{{Cite journal |last=Tanaka |first=Kenneth L. |date=1986 |title=The stratigraphy of Mars |url=http://doi.wiley.com/10.1029/JB091iB13p0E139 |journal=Journal of Geophysical Research |language=en |volume=91 |issue=B13 |article-number=E139 |doi=10.1029/JB091iB13p0E139 |bibcode=1986JGR....91E.139T |issn=0148-0227}}</ref><ref name="Carr_2010">{{Cite journal |last1=Carr |first1=Michael H. |last2=Head |first2=James W. |date=2010-06-01 |title=Geologic history of Mars |url=https://www.sciencedirect.com/science/article/pii/S0012821X09003847 |journal=Earth and Planetary Science Letters |series=Mars Express after 6 Years in Orbit: Mars Geology from Three-Dimensional Mapping by the High Resolution Stereo Camera (HRSC) Experiment |language=en |volume=294 |issue=3 |pages=185–203 |doi=10.1016/j.epsl.2009.06.042 |bibcode=2010E&PSL.294..185C |issn=0012-821X}}</ref>
{{Mars timescale}}
A second time scale based on mineral alteration observed by the OMEGA [[spectrometer]] on board the [[Mars Express]]. Using this method, three periods were defined, the Phyllocian (~4,500–4,000 Ma), Theiikian (~4,000–3,500 Ma), and Siderikian (~3,500 Ma to present).<ref name="Bibring_2006">{{Cite journal |last1=Bibring |first1=Jean-Pierre |last2=Langevin |first2=Yves |last3=Mustard |first3=John F. |last4=Poulet |first4=François |last5=Arvidson |first5=Raymond |last6=Gendrin |first6=Aline |last7=Gondet |first7=Brigitte |last8=Mangold |first8=Nicolas |last9=Pinet |first9=P. |last10=Forget |first10=F. |last11=Berthé |first11=Michel |date=2006-04-21 |title=Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data |url=https://www.science.org/doi/10.1126/science.1122659 |journal=Science |language=en |volume=312 |issue=5772 |pages=400–404 |doi=10.1126/science.1122659 |pmid=16627738 |bibcode=2006Sci...312..400B |s2cid=13968348 |issn=0036-8075}}</ref>
<timeline>
ImageSize  = width:800  height:50
PlotArea   = left:15 right:15 bottom:20 top:5
AlignBars   = early

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

Colors =
  id:sidericol  value:rgb(1,0.4,0.3)
  id:theiicol value:rgb(1,0.2,0.5)
  id:phyllocol  value:rgb(0.7,0.4,1)

PlotData=
 align:center  textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5)

 text:Siderikan  from:-3500  till:0 color:sidericol
 text:Theiikian from:-4000 till:-3500  color:theiicol
 text:Phyllocian from:start till:-4000  color:phyllocol
</timeline>

== See also ==
<!--Please keep entries in alphabetical order & add a short description [[WP:SEEALSO]]-->
{{Portal|Geology}}
{{div col|colwidth=25em}}
* [[Age of the Earth]]
* [[Cosmic calendar]]
* [[Deep time]]
* [[Evolutionary history of life]]
* [[Formation and evolution of the Solar System]]
* [[Geological history of Earth]]
* [[Geology of Mars]]
* [[Geon (geology)]]
* [[History of Earth]]
* [[History of geology]]
* [[History of paleontology]]
* [[List of fossil sites]]
* [[List of geochronologic names]]
* [[Lunar geologic timescale]]
* [[Martian geologic timescale]]
* [[Natural history]]
* [[New Zealand geologic time scale]]
* [[Prehistoric life]]
* [[Timeline of the Big Bang]]
* [[Timeline of evolution]]
* [[Timeline of the geologic history of the United States]]
* [[Timeline of human evolution]]
* [[Timeline of natural history]]
* [[Timeline of paleontology]]
{{div col end}}

== Notes ==
{{Notelist|group=note}}

== References ==
{{reflist|25em}}

==Further reading==
* {{cite journal |date=2009 |last1=Aubry|first1=Marie-Pierre|last2=Van Couvering|first2=John A.|last3=Christie-Blick|first3=Nicholas|last4= Landing|first4=Ed|last5=Pratt|first5=Brian R.|last6=Owen|first6=Donald E.|last7=Ferrusquia-Villafranca|first7=Ismael |title=Terminology of geological time: Establishment of a community standard |journal=Stratigraphy |volume=6 |issue=2 |pages=100–105 |doi=10.7916/D8DR35JQ}}
* {{cite journal |date=2004 |last1=Gradstein |first1=F. M. |last2=Ogg |first2=J. G. |title=A Geologic Time scale 2004 – Why, How and Where Next! |journal=Lethaia |volume=37 |issue=2 |pages=175–181 |url=https://eesc.columbia.edu/courses/w4937/Readings/Gradstein_Ogg_2004.pdf |access-date=30 November 2018 |doi=10.1080/00241160410006483 |bibcode=2004Letha..37..175G |archive-url=https://web.archive.org/web/20180417173639/http://eesc.columbia.edu/courses/w4937/Readings/Gradstein_Ogg_2004.pdf |archive-date=17 April 2018 }}
* {{cite book |date=2004 |last1=Gradstein|first1=Felix M.|last2=Ogg|first2=James G.|last3=Smith|first3=Alan G. |title=A Geologic Time Scale 2004 |url=https://books.google.com/books?id=rse4v1P-f9kC |location=Cambridge, UK |publisher=Cambridge University Press |isbn=978-0-521-78142-8 |access-date=18 November 2011}}
* {{cite journal |date=June 2004 |last1=Gradstein |first1=Felix M. |last2=Ogg |first2=James G. |last3=Smith |first3=Alan G. |last4=Bleeker |first4=Wouter |last5=Laurens |first5=Lucas, J. |title=A new Geologic Time Scale, with special reference to Precambrian and Neogene |journal=Episodes |volume=27 |issue=2 |pages=83–100 |doi=10.18814/epiiugs/2004/v27i2/002 |doi-access=free }}
* {{cite news|url=https://www.npr.org/sections/13.7/2014/09/28/351692717/embracing-deep-time-thinking|last= Ialenti|first=Vincent|title=Embracing 'Deep Time' Thinking.|newspaper= NPR|date= 28 September 2014|publisher=NPR Cosmos & Culture}}
* {{cite news|url=https://www.npr.org/sections/13.7/2014/09/21/350344129/pondering-deep-time-could-inspire-new-ways-to-view-climate-change |last=Ialenti|first=Vincent|title=Pondering 'Deep Time' Could Inspire New Ways To View Climate Change.|newspaper=NPR|date=21 September 2014|publisher=NPR Cosmos & Culture}}
* {{cite journal |date=30 July 2004 |author1-link=Andrew H. Knoll|last1=Knoll|first1=Andrew H.|last2=Walter|first2=Malcolm R.|last3=Narbonne|first3=Guy M.|last4=Christie-Blick|first4=Nicholas |title=A New Period for the Geologic Time Scale |journal=[[Science (journal)|Science]] |volume=305 |issue=5684 |pages=621–622 |url=http://www.ldeo.columbia.edu/~ncb/Selected_Articles_all_files/17_Science%20305.621.pdf |archive-url=https://web.archive.org/web/20111215034718/http://www.ldeo.columbia.edu/%7Encb/Selected_Articles_all_files/17_Science%20305.621.pdf |archive-date=2011-12-15 |url-status=live |doi=10.1126/science.1098803 |access-date=18 November 2011 |pmid=15286353|s2cid=32763298}}
* {{cite book |date=2010 |last=Levin|first=Harold L. |chapter=Time and Geology |chapter-url=https://books.google.com/books?id=D0yl7Cqsu78C&pg=PA29|title=The Earth Through Time |url=https://books.google.com/books?id=D0yl7Cqsu78C |place=Hoboken, New Jersey |publisher=John Wiley & Sons |isbn=978-0-470-38774-0 |access-date=18 November 2011}}
* {{cite book |last=Montenari |first=Michael |url=https://books.google.com/books?id=xzJQDAAAQBAJ |title=Stratigraphy and Timescales |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |date=2016 |isbn=978-0-12-811549-7}}
* {{cite book |last=Montenari |first=Michael |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/2/suppl/C |title=Advances in Sequence Stratigraphy |date=2017 |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-813077-3}}
* {{cite book |last=Montenari |first=Michael |date=2018 |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/3/suppl/C |title=Cyclostratigraphy and Astrochronology |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-815098-6}}
* {{cite book |last=Montenari |first=Michael |date=2019 |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/4/suppl/C |title=Case Studies in Isotope Stratigraphy |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-817552-1}}
* {{cite book |last=Montenari |first=Michael |date=2020 |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/5/suppl/C |title=Carbon Isotope Stratigraphy |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-820991-2}}
*{{cite book |last=Montenari |first=Michael |date=2021 |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/6/suppl/C |title=Calcareous Nannofossil Biostratigraphy |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-824624-5}}
*Montenari, Michael (2022). [https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/7/suppl/C Integrated Quaternary Stratigraphy] (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-323-98913-8.
*Montenari, Michael (2023). [https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/8/suppl/C Stratigraphy of Geo- and Biodynamic Processes] (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-323-99242-8.
* Nichols, Gary (2013). ''[https://books.google.com/books?id=Gcgp5oLFrZMC Sedimentology and Stratigraphy]'' (2nd ed.). Hoboken: Wiley-Blackwell. {{ISBN|978-1-4051-3592-4}}
* Williams, Aiden (2019). ''[https://books.google.com/books?id=etVhxQEACAAJ Sedimentology and Stratigraphy]'' (1st ed.). Forest Hills, NY: Callisto Reference. {{ISBN|978-1-64116-075-9}}

==External links==
{{Commons category|Geologic time scale}}
{{Wikibooks|Historical Geology|Geological column}}
* The current version of the International Chronostratigraphic Chart can be found at [https://stratigraphy.org/chart stratigraphy.org/chart] 
* Interactive version of the International Chronostratigraphic Chart is found at [https://stratigraphy.org/timescale stratigraphy.org/timescale]
* A list of current Global Boundary Stratotype and Section Points is found at [https://stratigraphy.org/gssps/ stratigraphy.org/gssps]
* [https://web.archive.org/web/20050418090602/http://rst.gsfc.nasa.gov/Sect2/Sect2_1b.html NASA: Geologic Time] (archived 18 April 2005)
* [https://web.archive.org/web/20190120115100/https://www.geosociety.org/GSA/Education_Careers/Geologic_Time_Scale/GSA/timescale/home.aspx GSA: Geologic Time Scale] (archived 20 January 2019)
* [http://www.bgs.ac.uk/discoveringGeology/time/timechart/home.html British Geological Survey: Geological Timechart]
* [https://web.archive.org/web/20040623025505/http://www.stratigraphy.org/geowhen/ GeoWhen Database] (archived 23 June 2004)
* [https://web.archive.org/web/20051111150720/http://www.nmnh.si.edu/paleo/geotime/index.htm National Museum of Natural History – Geologic Time] (archived 11 November 2005)
* [https://www.seegrid.csiro.au/twiki/bin/view/CGIModel/GeologicTime SeeGrid: Geological Time Systems]. {{Webarchive|url=https://web.archive.org/web/20080723195950/https://www.seegrid.csiro.au/twiki/bin/view/CGIModel/GeologicTime |date=23 July 2008 }}. Information model for the geologic time scale.
* [http://exploringtime.org/?page=segments Exploring Time] from Planck Time to the lifespan of the universe
* [https://web.archive.org/web/20120425232455/http://www.episodes.co.in/www/backissues/272/Time%20Scale.pdf Episodes], Gradstein, Felix M. et al. (2004) ''A new Geologic Time Scale, with special reference to Precambrian and Neogene'', Episodes, Vol. 27, no. 2 June 2004 (pdf)
* Lane, Alfred C, and Marble, John Putman 1937. [https://books.google.com/books?id=ckIrAAAAYAAJ Report of the Committee on the measurement of geologic time]
* [https://web.archive.org/web/20110714173934/http://www.newsciencelessons.com/geology_lesson_plans.html Lessons for Children on Geologic Time] (archived 14 July 2011)
* [http://deeptime.info Deep Time – A History of the Earth : Interactive Infographic]
*[https://geology.buzz/threads/geologic-time-scale.36/ Geology Buzz: Geologic Time Scale]. {{Webarchive|url=https://web.archive.org/web/20210812084221/https://geology.buzz/threads/geologic-time-scale.36/ |date=12 August 2021 }}.

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