Geologic time scale

Short description: System that relates geologic strata to time

The geologic time scale, proportionally represented as a log-spiral with some major events in Earth's history. A megaannus (Ma) represents one million (106) years.

The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and 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 lithologies, paleomagnetic properties, and fossils. 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[1] is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC)Template:Ref icc that are used to define divisions of geological time. The chronostratigraphic divisions are in turn used to define geochronologic units.[2]

## Contents

* 1 Principles
* 2 Divisions of geologic time
* 2.1 Terminology
* 3 Naming of geologic time
* 4 History of the geologic time scale
* 4.1 Early history
* 4.2 Establishment of primary principles
* 4.3 Formulation of a modern geologic time scale
* 4.4 The advent of geochronometry
* 4.5 Modern international geological time scale
* 5 Major proposed revisions to the ICC
* 5.1 Proposed Anthropocene Series/Epoch
* 5.2 Proposals for revisions to pre-Cryogenian timeline
* 5.2.1 Shields et al. 2021
* 5.2.2 Van Kranendonk et al. 2012 (GTS2012)
* 6 Table of geologic time
* 7 Extraterrestrial geologic time scales
* 7.1 Lunar (selenological) time scale
* 7.2 Martian geologic time scale
* 8 See also
* 9 Notes
* 10 References
* 11 Further reading
* 12 External links

## Principles

See also: Earth:Age of Earth, History of Earth, and Geological history of Earth

The geologic time scale is a way of representing deep time based on events that have occurred through Earth's history, a time span of about 4.54 ± 0.05 billion years.[3] 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 Ages, GSSAs) are used to divide geologic time. Proposals have been made to better reconcile these divisions with the rock record.[4][5]

Historically, regional geologic time scales were used[5] 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 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.[6][7]

* 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.[8][9][10][7] 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.[8][10][7] However, it is now known that not all sedimentary layers are deposited purely horizontally,[7][11] 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.[8] 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.[8][9][10][7]
* 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.[10][7]
* The relationships of 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.[7] 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.[12][7] This allows for a correlation of strata even when the horizon between them is not continuous.

## Divisions of geologic time

See also: Earth:Stratigraphy, Chronostratigraphy, Biostratigraphy, Magnetostratigraphy, Lithostratigraphy, and Geochronology

The geologic time scale is divided into chronostratigraphic units and their corresponding geochronologic units.

* An eon is the largest geochronologic time unit and is equivalent to a chronostratigraphic eonothem.[13] There are four formally defined eons: the Hadean, Archean, Proterozoic and Phanerozoic.[2]
* An era is the second largest geochronologic time unit and is equivalent to a chronostratigraphic erathem.[14][13] There are ten defined eras: the Eoarchean, Paleoarchean, Mesoarchean, Neoarchean, Paleoproterozoic, Mesoproterozoic, Neoproterozoic, Paleozoic, Mesozoic and Cenozoic, with none from the Hadean eon.[2]
* A period is equivalent to a chronostratigraphic system.[14][13] There are 22 defined periods, with the current being the Quaternary period.[2] As an exception, two subperiods are used for the Carboniferous Period.[14]
* An epoch is the second smallest geochronologic unit. It is equivalent to a chronostratigraphic series.[14][13] 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.[2] The use of subepochs as formal units in international chronostratigraphy was ratified in 2022.[15]
* An age is the smallest hierarchical geochronologic unit. It is equivalent to a chronostratigraphic stage.[14][13] There are 96 formal and five informal ages.[2] The current age is the Meghalayan.
* A chron is a non-hierarchical formal geochronology unit of unspecified rank and is equivalent to a chronostratigraphic chronozone.[14] These correlate with magnetostratigraphic, lithostratigraphic, or biostratigraphic units as they are based on previously defined stratigraphic units or geologic features.

Formal, hierarchical units of the geologic time scale (largest to smallest)  Chronostratigraphic unit (strata)  | Geochronologic unit (time)  | Time span[note 1]

|
|

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 Early and Late are used as the geochronologic equivalents of the chronostratigraphic Lower and 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 are the Silurian System and they were deposited 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 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 systems (chronostratigraphic units) has not been changed; rather, the absolute age has merely been refined.

### Terminology

Chronostratigraphy is the element of stratigraphy that deals with the relation between rock bodies and the relative measurement of geological time.[14] It is the process where distinct strata between defined stratigraphic horizons are assigned to represent a relative interval of geologic time.

A 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.[14]

A geochronologic unit is a subdivision of geologic time. It is a numeric representation of an intangible property (time).[16] These units are arranged in a hierarchy: eon, era, period, epoch, subepoch, age, and subage.[14] 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., stratigraphic position, paleomagnetism, stable isotope ratios). Geochronometry is the field of geochronology that numerically quantifies geologic time.[16]

A 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.[17] (Recently this has been used to define the base of a system)[18]

A Global Standard Stratigraphic Age (GSSA)[19] is a numeric-only, chronologic reference point used to define the base of geochronologic units prior to the Cryogenian. These points are arbitrarily defined.[14] 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 Chronostratigraphic Chart are represented by the unit Ma (megaannum, for 'million years'). For example, 201.3 ± 0.6 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 units commonly used by geologists are Ga (gigaannum, billion years), and ka (kiloannum, thousand years), with the latter often represented in calibrated units (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. The name of stages should also be derived from a geographic feature in the locality of its stratotype or type locality.[14]

Informally, the time before the Cambrian is often referred to as the Precambrian or pre-Cambrian (Supereon).[4][note 2]

Time span and etymology of geologic eonothem/eon names  Name  | Time span  | Duration (million years)  | Etymology of name

|
|
|

Phanerozoic | 541 to 0 million years ago | 541  | From Greek φανερός (phanerós) 'visible' or 'abundant' and ζωή (zoē) 'life'.
Proterozoic | 2,500 to 541 million years ago | 1959  | From Greek πρότερος (próteros) 'former' or 'earlier' and ζωή (zoē) 'life'.
Archean | 4,000 to 2,500 million years ago | 1500  | From Greek ἀρχή (archē) 'beginning, origin'.
Hadean | 4,600 to 4,000 million years ago | 600  | From Hades, Ancient Greek: ᾍδης, romanized: Háidēs, the god of the underworld (hell, the inferno) in Greek mythology.
Time span and etymology of geologic erathem/era names  Name  | Time span  | Duration (million years)  | Etymology of name

|
|
|

Cenozoic | 66 to 0 million years ago | 66  | From Greek καινός (kainós) 'new' and ζωή (zōḗ) 'life'.
Mesozoic | 251.9 to 66 million years ago | 185.902  | From Greek μέσο (méso) 'middle' and ζωή (zōḗ) 'life'.
Paleozoic | 541 to 251.9 million years ago | 289.098  | From Greek παλιός (palaiós) 'old' and ζωή (zōḗ) 'life'.
Neoproterozoic | 1,000 to 541 million years ago | 459  | From Greek νέος (néos) 'new' or 'young', πρότερος (próteros) 'former' or 'earlier', and ζωή (zōḗ) 'life'.
Mesoproterozoic | 1,600 to 1,000 million years ago | 600  | From Greek μέσο (méso) 'middle', πρότερος (próteros) 'former' or 'earlier', and ζωή (zōḗ) 'life'.
Paleoproterozoic | 2,500 to 1,600 million years ago | 900  | From Greek παλιός (palaiós) 'old', πρότερος (próteros) 'former' or 'earlier', and ζωή (zōḗ) 'life'.
Neoarchean | 2,800 to 2,500 million years ago | 300  | From Greek νέος (néos) 'new' or 'young' and ἀρχαῖος (arkhaîos) 'ancient'.
Mesoarchean | 3,200 to 2,800 million years ago | 400  | From Greek μέσο (méso) 'middle' and ἀρχαῖος (arkhaîos) 'ancient'.
Paleoarchean | 3,600 to 3,200 million years ago | 400  | From Greek παλιός (palaiós) 'old' and ἀρχαῖος (arkhaîos) 'ancient'.
Eoarchean | 4,000 to 3,600 million years ago | 400  | From Greek ἠώς (ēōs) 'dawn' and ἀρχαῖος (arkhaîos) 'ancient'.
Time span and etymology of geologic system/period names  Name  | Time span  | Duration (million years)  | Etymology of name

|
|
|

Quaternary | 2.6 to 0 million years ago | 2.58  | First introduced by Jules Desnoyers in 1829 for sediments in France's Seine Basin that appeared to be younger than Tertiary[note 3] rocks.[22]
Neogene | 23 to 2.6 million years ago | 20.45  | Derived from Greek νέος (néos) 'new' and γενεά (geneá) 'genesis' or 'birth'.
Paleogene | 66 to 23 million years ago | 42.97  | Derived from Greek παλιός (palaiós) 'old' and γενεά (geneá) 'genesis' or 'birth'.
Cretaceous | ~145 to 66 million years ago | ~79  | Derived from Terrain Crétacé used in 1822 by Jean d'Omalius d'Halloy in reference to extensive beds of chalk within the Paris Basin.[23] Ultimately derived from Latin crēta 'chalk'.
Jurassic | 201.3 to 145 million years ago | ~56.3  | Named after the Jura Mountains. Originally used by Alexander von Humboldt as 'Jura Kalkstein' (Jura limestone) in 1799.[24] Alexandre Brongniart was the first to publish the term Jurassic in 1829.[25][26]
Triassic | 251.9 to 201.3 million years ago | 50.602  | From the Trias of Friedrich August von Alberti in reference to a trio of formations widespread in southern Germany.
Permian | 298.9 to 251.9 million years ago | 46.998  | Named after the historical region of Perm, Russian Empire.[27]
Carboniferous | 358.9 to 298.9 million years ago | 60  | Means 'coal-bearing', from the Latin carbō (coal) and ferō (to bear, carry).[28]
Devonian | 419.2 to 358.9 million years ago | 60.3  | Named after Devon, England.[29]
Silurian | 443.8 to 419.2 million years ago | 24.6  | Named after the Celtic tribe, the Silures.[30]
Ordovician | 485.4 to 443.8 million years ago | 41.6  | Named after the Celtic tribe, Ordovices.[31][32]
Cambrian | 541 to 485.4 million years ago | 55.6  | Named for Cambria, a Latinised form of the Welsh name for Wales, Cymru.Cite error: Invalid `<ref>` tag; refs with no name must have content
Ediacaran | 635 to 541 million years ago | ~94  | Named for the Ediacara Hills. Ediacara is possibly a corruption of Kuyani 'Yata Takarra' 'hard or stony ground'.[33][34]
Cryogenian | 720 to 635 million years ago | ~85  | From Greek κρύος (krýos) 'cold' and γένεσις (génesis) 'birth'.[5]
Tonian | 1,000 to 720 million years ago | ~280  | From Greek τόνος (tónos) 'stretch'.[5]
Stenian | 1,200 to 1,000 million years ago | 200  | From Greek στενός (stenós) 'narrow'.[5]
Ectasian | 1,400 to 1,200 million years ago | 200  | From Greek ἔκτᾰσῐς (éktasis) 'extension'.[5]
Calymmian | 1,600 to 1,400 million years ago | 200  | From Greek κάλυμμᾰ (kálumma) 'cover'.[5]
Statherian | 1,800 to 1,600 million years ago | 200  | From Greek σταθερός (statherós) 'stable'.[5]
Orosirian | 2,050 to 1,800 million years ago | 250  | From Greek ὀροσειρά (oroseirá) 'mountain range'.[5]
Rhyacian | 2,300 to 2,050 million years ago | 250  | From Greek ῥύαξ (rhýax) 'stream of lava'.[5]
Siderian | 2,500 to 2,300 million years ago | 200  | From Greek σίδηρος (sídēros) 'iron'.[5]
Time span and etymology of geologic series/epoch names  Name  | Time span  | Duration (million years)  | Etymology of name

|
|
|

Holocene | 0.012 to 0 million years ago | 0.0117  | From Greek ὅλος (hólos) 'whole' and καινός (kainós) 'new'
Pleistocene | 2.58 to 0.012 million years ago | 2.5683  | Coined in the early 1830s from Greek πλεῖστος (pleîstos) 'most' and καινός (kainós) 'new'
Pliocene  | 5.33 to 2.58 million years ago | 2.753  | Coined in the early 1830s from Greek πλείων (pleíōn) 'more' and καινός (kainós) 'new'
Miocene  | 23.03 to 5.33 million years ago | 17.697  | Coined in the early 1830s from Greek μείων (meíōn) 'less' and καινός (kainós) 'new'
Oligocene | 33.9 to 23.03 million years ago | 10.87  | Coined in the 1850s from Greek ὀλίγος (olígos) 'few' and καινός (kainós) 'new'
Eocene | 56 to 33.9 million years ago | 22.1  | 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 | 66 to 56 million years ago | 10  | 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 | 100.5 to 66 million years ago | 34.5  | See Cretaceous
Lower Cretaceous | 145 to 100.5 million years ago | 44.5
Upper Jurassic
| 163.5 to 145 million years ago | 18.5  | See Jurassic
Middle Jurassic | 174.1 to 163.5 million years ago | 10.6
Lower Jurassic
| 201.3 to 174.1 million years ago | 27.2
Upper Triassic  | 237 to 201.3 million years ago | 35.7  | See Triassic
Middle Triassic
| 247.2 to 237 million years ago | 10.2
Lower Triassic  | 251.9 to 247.2 million years ago | 4.702
Lopingian | 259.1 to 251.9 million years ago | 7.198  | Named for Loping, China, an anglicization of Mandarin 乐平 (lèpíng) 'peaceful music'
Guadalupian | 272.95 to 259.1 million years ago | 13.85  | 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 | 298.9 to 272.95 million years ago | 25.95  | From Latin cis- (before) + Russian Урал (Ural), referring to the western slopes of the Ural Mountains
Upper Pennsylvanian  | 307 to 298.9 million years ago | 8.1  | Named for the US state of Pennsylvania, from William Penn + Latin silvanus (forest) + -ia by analogy to Transylvania
Middle Pennsylvanian  | 315.2 to 307 million years ago | 8.2
Lower Pennsylvanian  | 323.2 to 315.2 million years ago | 8
Upper Mississippian  | 330.9 to 323.2 million years ago | 7.7  | Named for the Mississippi River, from Ojibwe ᒥᐦᓯᓰᐱ (misi-ziibi) 'great river'
Middle Mississippian  | 346.7 to 330.9 million years ago | 15.8
Lower Mississippian  | 358.9 to 346.7 million years ago | 12.2
Upper Devonian  | 382.7 to 358.9 million years ago | 23.8  | See Devonian
Middle Devonian | 393.3 to 382.7 million years ago | 10.6
Lower Devonian  | 419.2 to 393.3 million years ago | 25.9
Pridoli | 423 to 419.2 million years ago | 3.8  | Named for the Homolka a Přídolí nature reserve near Prague, Czechia
Ludlow | 427.4 to 423 million years ago | 4.4  | Named after Ludlow, England
Wenlock | 433.4 to 427.4 million years ago | 6  | Named for the Wenlock Edge in Shropshire, England
Llandovery | 443.8 to 433.4 million years ago | 10.4  | Named after Llandovery, Wales
Upper Ordovician  | 458.4 to 443.8 million years ago | 14.6  | See Ordovician
Middle Ordovician | 470 to 458.4 million years ago | 11.6
Lower Ordovician  | 485.4 to 470 million years ago | 15.4
Furongian | 497 to 485.4 million years ago | 11.6  | From Mandarin 芙蓉 (fúróng) 'lotus', referring to the state symbol of Hunan
Miaolingian | 509 to 497 million years ago | 12  | Named for the Miao Ling (zh) mountains of Guizhou, Mandarin for 'sprouting peaks'
Cambrian Series 2 (informal)  | 521 to 509 million years ago | 12  | See Cambrian
Terreneuvian | 541 to 521 million years ago | 20  | Named for Terre-Neuve, a French calque of Newfoundland

## History of the geologic time scale

See also: Earth:History of geology and History of paleontology

### Early history

The most modern geological time scale was not formulated until 1911[35] 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.[36] The broader concept of the relation between rocks and time can be traced back to (at least) the philosophers of Ancient Greece from 1200 BC to 600 AD. Xenophanes of Colophon (c. 570–487 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 transgressed over the land and at other times had regressed.[37] 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 Chinese naturalist Shen Kuo[38] (1031–1095) and Islamic scientist-philosophers, notably the Brothers of Purity, who wrote on the processes of stratification over the passage of time in their treatises.[37] Their work likely inspired that of the 11th-century 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.[37] Avicenna also recognized fossils as "petrifications of the bodies of plants and animals",[39] with the 13th-century Dominican bishop Albertus Magnus (c. 1200–1280), who drew from Aristotle's natural philosophy, extending this into a theory of a petrifying fluid.[40] These works appeared to have little influence on scholars in Medieval Europe who looked to the Bible to explain the origins of fossils and sea-level changes, often attributing these to the 'Deluge', including Ristoro d'Arezzo in 1282.[37] 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':[41][37]

> 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.

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 were not readily accepted and dissent from 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.[37] 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."[40] Later, in the 19th century, academics further developed theories on stratification. William Smith, often referred to as the "Father of Geology"[42] 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".[42] After studying rock layers and the fossils they contained, 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.[43] 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."[43]

### 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.[37] In De solido intra solidum naturaliter contento dissertationis prodromus Steno states:[8][44]

>   * 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.

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). While Steno's principles were simple and attracted much attention, applying them proved challenging.[37] 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 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".[45][37] Anton Moro (1687–1784) also used primary and secondary divisions for rock units but his mechanism was volcanic.[46][37] 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 (1713–1795) to include tertiary and quaternary divisions.[37] 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.[47][9][48] Hutton's theory would later become known as uniformitarianism, popularised by John Playfair[49] (1748–1819) and later Charles Lyell (1797–1875) in his Principles of Geology.[10][50][51] 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, Georges Cuvier, 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.jpgOne 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.[3] These estimations varied from 15,000 million years to 0.075 million years depending on method and author, but the estimations of 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.[3] Early attempts at determining ages of uranium minerals and rocks by Ernest Rutherford, Bertram Boltwood, Robert Strutt, and Arthur Holmes, would culminate in what are considered the first international geological time scales by Holmes in 1911 and 1913.[35][52][53] The discovery of isotopes in 1913[54] 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.[3][53][55][56]

### Modern international geological time scale

The establishment of the IUGS in 1961[57] and acceptance of the Commission on Stratigraphy (applied in 1965)[58] 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".[1]

Following on from Holmes, several A Geological Time Scale books were published in 1982,[59] 1989,[60] 2004,[61] 2008,[62] 2012,[63] 2016,[64] and 2020.[65] 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.[2] Subsequent Geologic Time Scale books (2016[64] and 2020[65]) 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.

Template:Timeline geological timescale

## Major proposed revisions to the ICC

### Proposed Anthropocene Series/Epoch

First suggested in 2000,[66] 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.[67] The definition of the Anthropocene as a geologic time period rather than a geologic event remains controversial and difficult.[68][69][70][71]

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.[72] The formal proposal was completed and submitted to the Subcommission on Quaternary Stratigraphy in late 2023 for a section in Crawford Lake, Ontario, with heightened Plutonium levels corresponding to 1952 CE.[73] 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"[74]

### 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.[4] This work assessed the geologic history of the currently defined eons and eras of the Precambrian,[note 2] and the proposals in the "Geological Time Scale" books 2004,[75] 2012,[5] and 2020.[76] Their recommend revisions[4] 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)[note 4]
* 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:[note 5] <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 January 2025[update]), 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.[2] It included a proposal to substantially revise the pre-Cryogenian time scale to reflect important events such as the 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.[5] As of April 2022[update] 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 Era/Erathem (4567–4404 Ma) – the name alluding both to the mythological Chaos and the chaotic phase of planet formation.[63][77][78]
* 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, zircons.[63][77]
* 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.[63][77]
* Isuan Period/System (3810–3490 Ma) – named after the Isua Greenstone Belt.[63]
* Mesoarchean Era/Erathem (3490–2780 Ma)
* Vaalbaran Period/System (3490–3020 Ma) – based on the names of the Kaapvaal (Southern Africa) and Pilbara (Western Australia) cratons, to reflect the growth of stable continental nuclei or proto-cratonic kernels.[63]
* 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.[63]
* Neoarchean Era/Erathem (2780–2420 Ma)
* Methanian Period/System (2780–2630 Ma) – named for the inferred predominance of methanotrophic prokaryotes[63]
* Siderian Period/System (2630–2420 Ma) – named for the voluminous banded iron formations formed within its duration.[63]
* Proterozoic Eon/Eonothem (2420–538.8 Ma)[note 4]
* Paleoproterozoic Era/Erathem (2420–1780 Ma)
* Oxygenian Period/System (2420–2250 Ma) – named for displaying the first evidence for a global oxidising atmosphere.[63]
* Jatulian or Eukaryian Period/System (2250–2060 Ma) – names are respectively for the Lomagundi–Jatuli δ13C isotopic excursion event spanning its duration, and for the (proposed)[79][80] first fossil appearance of eukaryotes.[63]
* Columbian Period/System (2060–1780 Ma) – named after the supercontinent Columbia.[63]
* Mesoproterozoic Era/Erathem (1780–850 Ma)
* Rodinian Period/System (1780–850 Ma) – named after the supercontinent Rodinia, stable environment.[63]

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 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:500 start:-4500 ScaleMinor = unit:year increment:100 start:-4500 PlotData =

align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5)
bar:Eonothem/Eon
from: -2420 till: -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 January 2025[update]), 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

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[note 2] 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).[4][81] The use of subseries/subepochs has been ratified by the ICS.[15]

While some regional terms are still in use,[5] 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.[1][82]

Eonothem/
Eon  | Erathem/
Era  | System/
Period  | Series/
Epoch  | Stage/
Age  | Major events  | Start, million years ago
[note 6]

|
|
|
|
|
|

Phanerozoic | Cenozoic
[note 3] | Quaternary | Holocene | Meghalayan | 4.2 ka cool period, dry climate leads to decline of agriculture-related civilisations in Egypt, Mesopotamia and India.[83] Medieval Warm Period (about 900 - 1350 CE) and Little Ice Age (about 1400 to 1900 CE).[84] Rapidly warming climate as CO2 added to atmosphere from burning fossil fuels.[85] | 0.0042 *
Northgrippian | 8.2 ka cool period,[84] followed by warming climate with melting ice raising sea levels.[86] Doggerland and Sundaland flooded.[87][88] | 0.0082 *
Greenlandian | Younger Dryas and Last Glacial Period end. Rise of agriculture.[86] Extinction of Pleistocene megafauna.[89] | 0.0117 *
Pleistocene | Upper/Late ('Tarantian') | Eemian Interglacial Stage followed by the Last Glacial Period.[84] After Last Glacial Maximum (about 25 – 15 ka) climate begins to warm. Younger Dryas final cold period of ice age. Toba supervolcano eruption. Homo sapiens spread across the globe. Homo floresiensis live on island of Flores. Homo neanderthalensis go extinct.[89] | 0.129
Chibanian | Brunhes–Matuyama geomagnetic reversal event.[90] Homo heidelbergensis evolves in Africa and spreads to Europe. Homo neanderthalensis appear in western Eurasia. Homo sapiens evolve in Africa. Homo erectus and Homo heidelbergensis die out.[89] | 0.774± 0.005*
Calabrian | Mid Pleistocene transition: glacial/interglacial frequency slows to every 100,000 years. Glacial periods now long enough for continental ice-sheets beyond polar regions.[85][90] Chimpanzees and bonobos diverge. Homo erectus spreads through Eurasia. Homo habilis goes extinct.[89] | 1.8 *
Gelasian  | Start of Pleistocene Ice Age: 40,000 year cycles of glacials/interglacials with ice cap growth and retreat, and sea level falls and rises.[85] Rise of Pleistocene megafauna. Homo habilis and Homo erectus evolve in Africa.[89] | 2.58 *
Neogene | Pliocene  | Piacenzian  | Isthmus of Panama land bridge forms between North and South America blocking equatorial ocean currents between Atlantic and Pacific oceans. Gulf Stream develops as Atlantic waters divert northward.[91][85] Global temperatures warm melting polar ice caps and sea levels rise flooding continental margins. Temperatures drop at 2.7 Ma and the Pleistocene Ice Age begins.[85] First modern big cats and modern horses. Tortoises and finches arrive in the Galapagos.[89] Earliest humans appear.[86] | 3.6 ± 0.005*
Zanclean  | Straits of Gibraltar form as Atlantic waters flood the Mediterranean Sea basin (Zanclean flood).[91] Global climate continues to cool.[85] Asian elephants appear.[89] Hominins Ardipithecus, Australopithecus and Paranthropus evolve.[86] | 5.333 ± 0.005*
Miocene  | Messinian | Connection between Mediterranean Sea and Atlantic is blocked, resulting in Messinian salinity crisis with evaporites accumulating across Mediterranean as its waters dry up. Collision of Banda Arc with Australia and Timor begins.[91] Global climate cools and permanent ice cap forms in Arctic. Sea levels drop as ice sheets grow.[85] Spread of C4 grasses result in extinction of many herbivoress.[86] Sea snakes evolve. Gorilla-human-chimpanzee lineages split, then chimpanzees and humans diverge.[89] Earliest hominid Sahelanthropus.[86] | 7.246 ± 0.005*
Tortonian | 11.63 ± 0.005*
Serravallian | Australia begins to collide with Southeast Asia, blocking equatorial circulation between western Pacific and Indian Oceans.[91][85] Antarctic ice cap shrinks as global temperatures warm (Middle Miocene climatic optimum).[85] Last creodonts (early predatory mammals) become extinct. Megalodon (giant shark) evolves.[89] | 13.82 ± 0.05*
Langhian | 15.97 ± 0.05*
Burdigalian | The Tian Shan and Altai mountains, Central Asia, form (Himalayan orogeny). Columbia River Basalt large igneous province (LIP) eruptions above rising Yellowstone hotspot, North America.[91][86] Climate continues to cool.[85] Compositae (herbaceous plants) appear and rapidly diversify, triggering evolutionary radiations in rodents, snakes (first vipers appear) and songbirds.[86][89] First gibbons and orangutans. First modern dolphins.[89] | 20.44 ± 0.05
Aquitanian  | 23.03 *
Paleogene | Oligocene | Chattian | North America and Eurasia plate boundary established along Mid-Atlantic Ridge.[91] Central American volcanic arc begins to collide with South America. East African LIP eruptions begin as Afar mantle plume rises.[91] Late Cenozoic Ice Age begins. Rapid growth of the Antarctic ice cap produces major drop in global sea levels.[86] Grasslands and prairies thrive as climate dries. Paraceratherium largest ever land mammal flourishes. First felids (cats), mustelids (e.g. weasels, otters, badgers), and pinnipeds (seals, sea lions and walruses). Whales split into toothed and filter feeders. Multituberculates (rat-like early mammals) go extinct.[89] | 28.1 ± 0.1*
Rupelian | 33.9 ± 0.1*
Eocene | Priabonian | Subduction in the Mediterranean leads to Tell-Rif-Betic, Dinarides, Hellenides and Taurides (Alpine) orogenies. Eurekan orogeny, Greenland.[91] Zagros orogeny as Arabia and Eurasia collide.[92] Laramide orogeny ends.[86] Gulf of Aden forms between Africa and Asia.[93] Cooling climate with brief warm period. End Eocene Australia and South America move away from Antarctica opening Drake and Tasmanian passages. Antarctic Circumpolar current forms. Rapid drop in global temperatures. Ice sheets on Antarctica.[86] Canids (wolves and foxes), Catarrhine primates (old world monkeys and apes), and raptors evolve. Basilosaurus is first fully aquatic whale.[89] | 37.8 ± 0.1*
Bartonian | 41.2 ± 0.2
Lutetian | 47.8 ± 0.2*
Ypresian | Greenland separates from Eurasia and Eurasian Basin opens in Arctic. Greater India collides with southern Eurasia, beginning Himalayan orogeny. North Atlantic LIP eruptions continue.[91] Major reorganisation of plate motions across Pacific region initiates Izu-Bonin-Mariana and Tonga-Kermadec subduction zones.[94] Greenhouse temperatures continue from Paleocene-Eocene Thermal Maximum (PETM) as climate affected by North Atlantic LIP eruptions, but global cooling begins from about 50 Ma with changing paleogeography and oceanography conditions.[85] Angiosperms (flowering plants) evolve larger fruits. First songbirds, parrots and woodpeckers. Primates divide into strepsirrhines (lemurs and lorises) and haplorhines (tarsiers and anthropoids). Artiodactyls (even-toed ungulates) appear and split into Cetruminantia (ruminants, whales and dolphins), Suina (pigs), and Tylopoda (camels and relatives). First Carnivora (meat-eating mammals). Mice, rats, bats and tapirs appear. Eohippus earliest member of horse family. Marsupials reach Australia.[89] | 56 ± 0.2*
Paleocene | Thanetian | Alpine orogeny develops as Neotethys closes and Africa begins collision with Eurasia.[91] Pyrenean and Laramide orogenies continue.[91][86] India drifts rapidly northwards. North Atlantic LIP eruptions start as Proto-Icelandic mantle plume rises.[91] Subduction zones form along margins of Caribbean plate.[95] Bering Straits land bridge present during low sea level periods.[91] Chicxulub impact causes "impact winter", then climate warms with final eruption of the Deccan Traps before cool, dry conditions re-established. Rapid rise in global temperatures at onset of PETM due to North Atlantic LIP eruptions.[91][85] End-Cretaceous mass extinction about 75% of plant and animal species go extinct, including ammonoids, rudist molluscs, non-avian dinosaurs, plesiosaurs, mosasaurs and pterosaurs. Mammals evolve quickly filling vacant ecological niches, modern groups of birds diversify and angiosperms become dominant form of plant life. First earthwormss and land turtles. Phorusrhacidae (terror birds) and creodonts (early predatory mammals) evolve. Perissodactyls (odd-toed ungulates) appear and diversify. First primates, proboscideans (elephants), Xenartha (sloths, anteaters and armadillos) and rodents.[89] | 59.2 ± 0.2*
Selandian | 61.6 ± 0.2*
Danian | 66 ± 0.3*
Mesozoic | Cretaceous | Upper/Late | Maastrichtian | Pangaea continues to fragment. Africa and South America separate as seafloor spreading established in South Atlantic. India and Australia move away from Antarctica, and India separates from Madagascar. Central Atlantic propagates north. |Pyrenean orogeny begins as Iberia rotates relative to Eurasia. Africa moves northwards.[91] Sevier and Laramide orogenies, western North America.[91][86] LIP eruptions include: Ontong Java-Nui; Kerguelen; High Arctic and Deccan Traps.[91][85] Highest sea levels in the Phanerozoic, shallow seas extend across large areas of the continents.[91] Greenhouse climate global average temperature peaks c. 28°C in the Cenomanian-Turonian. Tropical plants and dinosaurs on Antarctica and above Arctic Circle. Oceanic anoxic events (OAEs) result in widespread deposition of organic-rich black shales.[85] Calcareous foraminifera and coccolithophores flourish forming massive chalk deposits. Teleost (bony fish) radiate.[86] Predators grow large: plesiosaurs and mosasaurs in the sea;[86] carcharodontosaurs and tyrannosaurs on land.[89] Modern lobsters, crabs, shrimps and crocodiles appear. First bees, termites, ants, fleas, mantids and snakes. Angiosperms (flowering plants) proliferate and develop symbiotic relationships with insects. First grasses. Woody angiosperms evolve including rose, magnolia and sycamore families. First marsupials and monotremes.[86][89] End of the Cretaceous is marked by the Chicxulub impact event and the Cretaceous-Paleogene mass extinction.[85] | 72.1 ± 0.6*
Campanian | 83.6 ± 0.7*
Santonian | 86.3 ± 0.7*
Coniacian | 89.8 ± 1*
Turonian | 93.9 ± 0.8*
Cenomanian | 100.5 ± 0.9*
Lower/Early | Albian | ~113 ± 1*
Aptian | ~125 ± 1
Barremian | ~129.4 ± 1.5*
Hauterivian | ~132.9 ± 2*
Valanginian | ~139.8 ± 3*
Berriasian | ~145 ± 4
Jurassic | Upper/Late  | Tithonian  | Seafloor spreading in the Central Atlantic between North America and Africa-South America begins break up of Pangaea. Rifting continues in northern Atlantic and Caribbean. Gondwana splits into East and West Gondwana as Somali and Mozambique basins open. Pacific plate forms in central Panthalassa. Cimmerian and Indosinian orogenies continue. Start of Andean tectonic cycle, South America.[91] Nevadan orogeny, North America.[86] Mongol-Okhotsk Ocean closes forming Verkhoyansk-Kolyma mountain belt, Siberia. Neotethys narrows. Greenhouse climate with warmer and cooler periods. Arid conditions across equatorial and subtropical regions; coal and bauxite deposits in wetter temperate belts. Emplacement of Karoo-Ferrar LIP leads to global warming and the widespread Toarcian oceanic anoxic event.[85] Rise in global sea levels. Change from aragonite to calcite seas.[86] First large reefs. Phytoplankton and dinoflagellates diversify. First coccolithophores. Ammonoids and bellomnoids proliferate.[86] Major radiation of sharks. Vieraella earliest true frog. First modern turtles.[89] Cycads dominant forest flora.[86] Also ferns, conifers and ginkgos.[85] Dinosaurs rise to dominance, mammals remain small.[86] First Ornithischia (e.g. stegasaurs and ceratopsians). Sauropods evolve into giants, including brachiosaurs, titanosaurs, and diplodocids. First ceratosaurs, megalosaurs, allosaurs, and coelurosaurs therapods. Coelurosaurs, many with feathers, include early tyrannosaurs and maniraptorans (ancestors of birds). First pterodactyloids.[89] | 152.1 ± 4
Kimmeridgian  | 157.3 ± 4*
Oxfordian  | 163.5 ± 4
Middle | Callovian  | 166.1 ± 4
Bathonian  | 168.3 ± 3.5*
Bajocian  | 170.3 ± 3*
Aalenian  | 174.1 ± 2*
Lower/Early | Toarcian  | 182.7 ± 1.5*
Pliensbachian  | 190.8 ± 1.5*
Sinemurian  | 199.3 ± 1*
Hettangian  | 201.3 ± 0.6*
Triassic | Upper/Late | Rhaetian  | Pangaea forms an arc extending from almost pole to pole. Siberian Traps eruptions wane, but hot house climate continues.[91] Cimmerian terranes collide with Eurasia: Indosinian orogeny in east; Cimmerian orogeny in west.[91][96] Sonoma (western Laurussia), and Hunter-Bowen (Australia) orogenies continue.[91][97] Late Triassic, emplacement of the Central Atlantic magmatic province (CAMP) followed by seafloor spreading marks start of Pangaea break up.[98] Archosaurs divide into pseudosuchia (crocodiles), and ornithodirans (dinosaurs and pterosaurs). Mammaliaformes evolve from cynodonts.[89] Evidence of endothermy (warm-bloodedness) in dinosaurs and mammals.[99] First teleosts (modern ray-finned fish). Ichthyosaurs, and sauropterygians plesiosaurs, nothosaurs, placodonts) appear.[99] First scleractinian (hard coral) reefs. First wasps and stick insects.[89] Late Triassic eruptions of Wrangellia LIP raises temperatures, intensifies Pangaea monsoons and increases rainfall (Carnian pluvial episode).[85] Bennettitales, modern ferns and conifers appear. First Lepidoptera (moths and butterflies). Modern groups of phytoplankton appear.[99] Manicouagan bolide impact reduces global temperatures, before CAMP eruptions increases them and triggers Triassic-Jurassic mass extinction.[100][85] Major loss of reef ecosystems, reduction in marine genera, conodonts die out. Major changes in terrestrial flora. Loss of vertebrate genera, including non-mammalian therapsids. Crocodylomorphs only pseudosuchians to survive.[89][85] | ~208.5 ± 1.5
Norian  | ~227 ± 2
Carnian  | ~237 ± 2*
Middle | Ladinian  | ~242 *
Anisian  | 247.2 ± 1.5
Lower/Early | Olenekian  | 251.2 ± 0.7
Induan  | 251.902 ± 0.4*
Paleozoic | Permian | Lopingian | Changhsingian | Pangaea at its maximum extent. Ural and Alleghanian orogenies continue.[91] Hunter-Bowen orogeny, eastern Australia;[97] Sonoma orogeny, western Laurussia. Kazakhstania and Tarim collide with Siberia. Orogenic collapse of Variscan orogeny and early extension along the lines of the future Atlantic, Indian and Southern Oceans. Opening of Neo-Tethys Ocean as Cimmerian terranes rift from northeast Gondwana.[91] Late Paleozoic Ice Age wanes and humid, icehouse climate give way to arid, greenhouse conditions.[101] Global average temperatures rise from c. 12° to over 30° at Permo-Triassic boundary.[85] Desert dune sands and evaporites dominate interior of Pangea.[91][101] Coal swamps at high latitudes and humid coastal regions.[91][85] Mosses, Coleoptera (beetles) and Diptera (two-winged flies) appear. Diapsids split into archosaurs (crocodiles and dinosaurs) and lepidosaurs (lizards and snakes). First marine reptiles. Therapsids and cynodonts evolve from synapsids.[89] Guadalupian-Lopingian boundary mass extinction linked to eruption of Emeishan LIP, South China.[86] At the Permo-Triassic boundary, eruption of the Siberian Traps LIP releases vast amounts of CO2 leading to extreme global warming, and the end-Permian mass extinction. Anoxic waters from the deep ocean move up to the shallows,[85] eliminating trilobites, rugose and tabulate corals, and placoderms. Brachiopods, ammonoids, sharks, bony fish, and crinoids see major reductions.[101] On land, forests disappear. Palaeodictyopterida and many insect groups go extinct, as do all non-therapsid synapsids and most therapsid genre.[101][86][89] | 254.14 ± 0.7*
Wuchiapingian | 259.1 ± 0.7*
Guadalupian | Capitanian | 265.1 ± 0.7*
Wordian | 268.8 ± 0.7*
Roadian | 272.95 ± 0.7*
Cisuralian | Kungurian | 283.5 ± 0.7
Artinskian | 290.1 ± 0.7*
Sakmarian | 295 ± 0.8*
Asselian | 298.9 ± 0.8*
Carboniferous
[note 7] | Pennsylvanian
[note 8] | Gzhelian  | Continuation of the Variscan orogeny (Ouachita and Alleghanian orogenies) with growth of the Central Pangean Mountains.[91] Ural orogeny continues with continental collision between Kazakhstania and Laurussia.[102] Humid, coal swamps form in foreland basins of the Central Pangean Mountains and around North and South China cratons.[103] As the Late Paleozoic icehouse (LPIA) continues, waxing and waning of ice sheets causes rapid changes in global sea level, flooding these regions and depositing cyclothem sequences.[104] Atmospheric oxygen levels rise to over 25% before decreasing again.[105] Appearance of aragonite reef builders, including algae and sponges.[86] Freshwater Eurypterids (sea scorpions). On land, Neoptera appear, and Miomoptera show earliest evidence for complete metamorphosis. First true terrestrial amphibians. Amniotes appear and split into two groups: sauropsids (reptiles) and synapsids (mammals).[89] Lepidodendron and Sigillaria lycopod trees dominate coal swamps, with smaller sphenopsids (horsetails) and seed ferns between. Gymnosperms, including conifers and cycads grow on drier ground.[86] LPIA peaks at Carboniferous-Permian boundary. A drop in CO2 levels and increase in arid conditions[106] leads to change in woodland vegetation (Carboniferous rainforest collapse).[107] | 303.7
Kasimovian  | 307 ± 1
Moscovian  | 315.2 ± 1.1
Bashkirian  | 323.2 *
Mississippian
[note 8] | Serpukhovian  | 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.[91] The terranes collide with southeastern Laurussia during the Variscan orogeny. Antler orogeny continues, and opening of the Slide Mountain Ocean along western margin of Laurussia.[108] Closure of Ural Ocean between Kazakhstania and Laurussia during the Ural orogeny. Development of Altai accretionary complexes along north and eastern margin of the Paleo-Tethys.[109] Main phase of LPIA begins. Drop in global sea levels, extensive glaciation across Gondwana.[106] Increasing atmospheric oxygen levels.[105] Change from calcite to aragonite seas.[86] Evolutionary radiations after the Late Devonian extinctions include brachiopods, bivalves, echinoderms, ammonoids, gastropods, sharks and ray-finned bony fish. Placoderms and graptolites die out. Proetida only group of trilobites.[86][89] First freshwater mollusks and sharks.[86] Arthropleura (millipede) largest ever terrestrial arthropod. First flying insects Paleodictyopora. Fish-like (Pederpes) and semi-aquatic tetrapods (Eucritta) appear on land.[89] Seedless vascular plants and seed ferns diversify.[86] | 330.9 ± 1.6
Viséan  | 346.7 ± 2.1*
Tournaisian  | 358.9 ± 2.5*
Devonian | Upper/Late  | Famennian | Paleo-Tethys continues to open as the Armorican Terrane Assemblage (ATA) drifts north and Annamia-South China moves away from Gondwana.[91][110] Rheic Ocean closes as ATA collides with Laurussia beginning the Variscan orogeny. Other orogenies: Antler, Ellesmerian, and Acadian (Laurussia); Achalian (Argentina); Tabberabberan/Lachlan (Australia); Ross (Antarctica); Kazakh (Kazakhstania).[91] Period of high sea-levels, greenhouse conditions but decreasing atmospheric CO2 levels and slowly cooling climate with glaciations towards end.[111] Vascular plants increase in size, develop large root systems and spread to upland areas. First forests, seed plants, and modern soil orders appear (alfisols and ultisols).[111] Growth of massive reef systems. Major radiation of jawed fish with appearance of ray-finned, lobe-finned, and cartilaginous fish. Appearance of tetrapods (evolved from lobe-finned fish). Early amphibians move on to land. First ammonoids.[86] Emplacement of the Viley and Pripyat–Dniepr–Donets large igneous provinces coincide with global marine anoxic events and the Kellwasser (c. 372 Ma) and Hangenberg (c. 359 Ma) mass extinctions.[111] Kellwasser extinction: c. 20% of families and c. 50% of genera of marine invertebrates lost. Tabulate coral and stromatoporoid reef ecosystems wiped out. Loss of placoderms and many groups of jawless fish. Hangenberg extinction: loss of c. 16% of marine families and c. 21% of marine genera, including ammonoids, ostracods and sharks.[111][112] | 372.2 ± 2.6*
Frasnian | 382.7 ± 2.6*
Middle | Givetian | 387.7 ± 2.7*
Eifelian | 393.3 ± 2.7*
Lower/Early | Emsian | 407.6 ± 2.8*
Pragian | 410.8 ± 2.8*
Lochkovian | 419.2 ± 2.8*
Silurian | Pridoli | Laurentia and Avalonia-Baltica collide as Iapetus Ocean closes, Caledonian-Scandian orogeny, and formation of Laurussia. Other orogenies: Salinic (Appalachians); Famatinian (South America) tapers off; Lachlan (Australia).[91][113] Series of microcontinents and North China separate opening Paleo-Tethys and closing Paleoasian Ocean.[113] Rheic Ocean widens between Gondwana and Laurussia. Siberia drifts north of equator.[91] Temperatures increase as Hirnantian glaciation ends. Sea levels rise. Deposition of black shales, North Africa and Arabia, major hydrocarbon source rocks.[91] Fluctuating climate with glacial advances results in changing ocean conditions causes extinction events, followed by ecological recoveries.[114] Widespread evaporite deposition and hothouse climate by late Silurian.[86][85] 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 (acanthodians). Appearance of ostracoderms. Appearance of vascular plants. First land animals including myriapods. First freshwater fish.[86] | 423 ± 2.7*
Ludlow | Ludfordian | 425.6 ± 2.6*
Gorstian | 427.4 ± 2.5*
Wenlock | Homerian | 430.5 ± 2.4*
Sheinwoodian | 433.4 ± 2.3*
Llandovery | Telychian | 438.5 ± 1.9*
Aeronian | 440.8 ± 1.8*
Rhuddanian | 443.8 ± 1.5*
Ordovician | Upper/Late | Hirnantian | 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 (South America); Benambran (Australia); Taconic (Laurentia). Baltica and Siberia drift north.[91] Early greenhouse climate, cooling to icehouse conditions during Hirnantian Ice Age. Increase in atmospheric O2.[115] 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.[116] Modern marine ecosystems established.[115] Earliest jawless fish. Tabulate corals and stromatoporoids dominant reef builders. Nautiloids main predators.[86] Appearance of eurypterids and asteroids. Spread of early land plants.[115] 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.[86] Drastic reduction in trilobite, brachiopod, graptolite, echinoderm, conodont, coral, and chitinozoan genera.[116] | 445.2 ± 1.5*
Katian | 453 *
Sandbian | 458.4 *
Middle | Darriwilian | 467.3 ± 1.6*
Dapingian | 470 *
Lower/Early | Floian
(formerly Arenig)  | 477.7 *
Tremadocian | 485.4 ± 1.7*
Cambrian | Furongian | Stage 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 (N.Africa/southern Europe); Kuunga (central Gondwana); Famatinian orogeny (South America); Delamerian (Australia).[91] Greenhouse climate. High atmospheric CO2 levels. Atmospheric oxygen levels rose with increase in photosynthesising organisms.[117] Early aragonite seas replaced by mixed aragonite-calcite seas with many animals developing CaCO3 skeletons.[118] Rapid diversification of animals (Cambrian Explosion), most modern animal phyla appear, e.g. arthropods; molluscs; annelids; echinoderms; bryozoa; priapulids; brachiopods; hemichordates; and, chordates. Radiations of small shelly fossils.[119] Giant anomalocarids (arthropods) dominant predators. Increase in bioturbation and grazing led to decline in stromatolites.[86] Varying oxygen levels in oceans led to series of extinction events followed by radiations, including: earliest Cambrian loss of the Ediacaran acritarchs; end-Botomian extinction, linked to the Kalkarindji large igneous province eruptions (c. 514 Ma) with loss of archaeocyathids (early Cambrian reef builders) and hyoliths; and, end-Cambrian reduction in trilobite diversity.[117][120][86] Many fossil lagerstätten, including Burgess Shale and Chengjiang Formation, formed by rapid burial in anoxic conditions.[117] | ~489.5
Jiangshanian | ~494 *
Paibian | ~497 ± 2[citation needed]*
Miaolingian | Guzhangian | ~500.5 *
Drumian | ~504.5 *
Wuliuan | ~509
Series 2 | Stage 4 | ~514
Stage 3 | ~521
Terreneuvian | Stage 2 | ~529
Fortunian | 541 ± 1.0*
Proterozoic | Neoproterozoic | Ediacaran | Good fossils of primitive animals. Ediacaran biota flourish worldwide in seas, possibly appearing after an explosion, possibly caused by a large-scale oxidation event.[121] First vendozoans (unknown affinity among animals), cnidarians and bilaterians. Enigmatic vendozoans include many soft-jellied creatures shaped like bags, disks, or quilts (like Dickinsonia). Simple trace fossils of possible worm-like 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 and Gondwana. Petermann Orogeny forms on Australian continent. Beardmore Orogeny in Antarctica, 633–620 Ma. Ozone layer forms. An increase in oceanic mineral levels.  | ~635 +5/-30[citation needed]*
Cryogenian | Possible "Snowball Earth" period. Fossils still rare. Late Ruker / Nimrod Orogeny in Antarctica tapers off. First uncontroversial animal fossils. First hypothetical terrestrial fungi[122] and streptophyta.[123] | ~720
Tonian | Final assembly of Rodinia supercontinent occurs in early Tonian, with breakup beginning c. 800 Ma. Sveconorwegian orogeny ends. Grenville Orogeny tapers off in North America. Lake Ruker / Nimrod Orogeny in Antarctica, 1,000 ± 150 Ma. Edmundian Orogeny (c. 920–850 Ma), Gascoyne Complex, Western Australia. Deposition of Adelaide Superbasin and Centralian Superbasin begins on 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), dinoflagellates, cryptophyta, haptophyta, and euglenids (the events may have begun in the Mesoproterozoic)[124] while the first retarians (e.g. forams) also appear: eukaryotes diversify rapidly, including algal, eukaryovoric and biomineralised forms. Trace fossils of simple multi-celled eukaryotes. Neoproterozoic oxygenation event (NOE), 850–540 Ma.[125] | 1000 [note 9]
Mesoproterozoic | Stenian | Narrow highly 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. Stromatolites decline as algae proliferate. First known sexually reproducing organisms.  | 1200 [note 9]
Ectasian | Platform covers continue to expand. Algal colonies in the seas. Grenville Orogeny in North America. Columbia breaks up.  | 1400 [note 9]
Calymmian | Platform covers expand. Barramundi Orogeny, McArthur Basin, Northern Australia, and Isan Orogeny, c. 1,600 Ma, Mount Isa Block, Queensland. First archaeplastidans (the first eukaryotes with plastids from cyanobacteria; e.g. red and green algae) and opisthokonts (giving rise to the first fungi and holozoans). Acritarchs (remains of marine algae possibly) start appearing in the fossil record.  | 1600 [note 9]
Paleoproterozoic | Statherian | Columbia (Nuna) supercontinent continues to grow along its margins by subduction-related magmatism and terrane accretion. Extension and rift zones begin to develop from c. 1.6 Ga. Eukaryotic red algae appear.[126] Vredefort impact event (2.19 Ga).[127] | 1800 [note 9]
Orosirian | 2.0–1.8 Ga Columbia supercontinent assembles during collisional events including Trans-Hudson orogeny (North America), Limpopo Belt (South Africa), Capricorn orogeny (Australia) and Trans-North China orogeny.[128] Drop in atmospheric oxygen as increased volcanism releases carbon dioxide.[5] Grypania represents a possible early eukaryote.[126] Sudbury Impact (1.85 Ga).[127] | 2050 [note 9]
Rhyacian | Massive rise in atmospheric oxygen leads to expansion of life and increased burial of organic matter (Lomagundi carbon isotope excursion) (2.3 to 2.1 Ga).[126] First red beds deposited. Eruptions of Bushveld Magmatic Province (from 2.25 Ga).[5] Orogenies in South America and West Africa mark beginning of Columbia supercontinent.[128] Yarrabubba impact structure (c. 2.23 Ga).[127] | 2300 [note 9]
Siderian | 2.5 – 2.42 Ga massive banded iron formations (BIFs) precipitated across most continents.[5] Increasing atmospheric oxygen leads to Great Oxidation Event (c. 2.4––2.3 Ga) and Huronian glaciations as global temperatures drop.[126][5] | 2500 [note 9]
Archean | Neoarchean | Widespread mantle melting and crustal growth followed by formation of supercratons Superia (North America, northwest Europe, South Africa and northwest Australia) and Sclavia (Canada, Zimbabwe, southern India, southwestern Australia, Brazil and North China).[5][129] Major diversification of cyanobacteria with multicellularity, increasing cell size and specialisation.[126] Proliferation of oxygen-producing life leads to stepwise increase in atmospheric oxygen and deposition of banded iron formation.[126][5] | 2800 [note 9]
Mesoarchean | Possible onset of plate tectonics c. 3 Ga.[91] Cratons with low relief and extensive shallow marine environments. Weathering increased supply of nutrients to seas. Localised free oxygen associated with carbonate platform stromatolites. Evidence for oxygen-producing photosynthesisers (and possible eukaryotes) c. 3.2 Ga, and terrestrial life c. 3 Ga.[126] Oldest evidence of glaciation c. 2.9 Ga.[5] | 3200 [note 9]
Paleoarchean | Growth of cratons by terrane accretion.[5] Oldest evidence for macroscopic life preserved as stromatolites (c. 3.4 Ga). Evidence for anaerobic prokaryotes in variety of environments including hydrothermal systems and within subsurface sediments. Microbial mats and biofilms become common in shallow water environments.[126] | 3600 [note 9]
Eoarchean | Increasing formation of continental crust.[5] 3.8 – 3.65 Ga chemical traces of life in earliest known sedimentary rocks (Isua Greenstone Belt). Anaerobic prokaryotes including chemotrophs and photosynthesisers appear from c. 3.7 Ga. Early BIFs due to anoxygenic photosynthesis.[126] | 4000 [note 9]
Hadean | Earth consolidates from solar nebula over 10-30 million years. Collision with Theia (proto-planet) forms Moon from debris. Core differentiates. Magma ocean cools, releasing CO2 and water to give CO2-rich atmosphere. Icy asteroids also contribute water.[5] Mantle convection begins with rapid, shallow plate tectonics or stagnant lid tectonics. Decline in meteorite impacts with last ocean-vaporising impact c. 4.3 Ga. Probable emergence of life after this.[126] Evidence for oldest crust from detrital zircon c. 4.37 Ga.[91][5] Acasta gneiss complex contains oldest recorded rocks c. 4.03 Ga.[5] | 4600 ± 0.7[citation needed][note 9]

## Extraterrestrial geologic time scales

Main articles: Astronomy:Lunar geologic timescale, Martian geologic timescale, and Geology of Venus

Some other planets and satellites in the Solar System have sufficiently rigid structures to have preserved records of their own histories, for example, Venus, Mars and the Earth's Moon. Dominantly fluid planets, such as the giant planets, 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.[note 10]

### Lunar (selenological) time scale

The geologic history of Earth's Moon has been divided into a time scale based on geomorphological markers, namely impact cratering, 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), with the Imbrian divided into two series/epochs (Early and Late) were defined in the latest Lunar geologic time scale.[130] 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> ImageSize = width:800 height:75 PlotArea = left:65 right:15 bottom:20 top:5 AlignBars = justify

Colors =

id:prenectarian   value:rgb(0.823,0.302,0.380)
id:nectarian value:rgb(0.898,0.329,0.071)
id:imbrian   value:rgb(0,0.481,0.811)
id:earlyimbrian      value:rgb(0,0.404,0.741)
id:lateimbrian    value:rgb(0,0.557,0.882)
id:eratosthenian   value:rgb(0.238,0.839,0.728)
id:copernican     value:rgb(0.5,0.5,0.5)

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bar:Period

from: -1100   till:    0   text:Copernican  color:copernican
from:-3200   till: -1100   text:Eratosthenian  color:eratosthenian
from:-3850   till: -3200  text:Imbrian      color:imbrian
from: -3920  till: -3850  text:N shift:(2,-5)       color:nectarian
from: start  till: -3920  text:Pre-Nectarian       color:prenectarian

bar:Epoch

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from:  -3800 till: -3200   text:Late  color:lateimbrian
from: -3850  till: -3800   text:Early shift:(-20,-5)  color:earlyimbrian
from: start  till: -3850   color:white

</timeline>

Millions of years before present

### 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).[131][132] Template: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).[133] <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

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id:theiicol value:rgb(1,0.2,0.5)
id:phyllocol  value:rgb(0.7,0.4,1)

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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

* 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

## Notes

1. ↑ 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.
2. ↑ 2.0 2.1 2.2 Precambrian or pre-Cambrian is an informal geological term for time before the Cambrian period
3. ↑ 3.0 3.1 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.[20][21]
4. ↑ 4.0 4.1 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.
5. ↑ 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.
6. ↑ The dates and uncertainties quoted are according to the International Commission on Stratigraphy International Chronostratigraphic chart (v2024/12). An * indicates boundaries where a Global Boundary Stratotype Section and Point has been internationally agreed.
7. ↑ The Mississippian and Pennsylvanian are official sub-systems/sub-periods.
8. ↑ 8.0 8.1 This is divided into Lower/Early, Middle, and Upper/Late series/epochs
9. ↑ 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 9.12 Defined by absolute age (Global Standard Stratigraphic Age).
10. ↑ Not enough is known about extra-solar planets for worthwhile speculation.

## References

1. ↑ 1.0 1.1 1.2 "Statues & Guidelines". International Commission on Stratigraphy. https://stratigraphy.org/statutes.
2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Cite error: Invalid `<ref>` tag; no text was provided for refs named `ICS`
3. ↑ 3.0 3.1 3.2 3.3 Dalrymple, G. Brent (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved". Special Publications, Geological Society of London 190 (1): 205–221. doi:10.1144/GSL.SP.2001.190.01.14. Bibcode: 2001GSLSP.190..205D.
4. ↑ 4.0 4.1 4.2 4.3 4.4 Shields, Graham A.; Strachan, Robin A.; Porter, Susannah M.; Halverson, Galen P.; Macdonald, Francis A.; Plumb, Kenneth A.; de Alvarenga, Carlos J.; Banerjee, Dhiraj M. et al. (2022). "A template for an improved rock-based subdivision of the pre-Cryogenian timescale". Journal of the Geological Society 179 (1): jgs2020–222. doi:10.1144/jgs2020-222. Bibcode: 2022JGSoc.179..222S.
5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 5.18 5.19 5.20 5.21 5.22 5.23 5.24 5.25 Van Kranendonk, Martin J. (2012). "A Chronostratigraphic Division of the Precambrian". The Geologic Time Scale. pp. 299–392. doi:10.1016/b978-0-444-59425-9.00016-0. ISBN 978-0-444-59425-9. https://books.google.com/books?id=usoqlA8AVDUC&pg=PA299.
6. ↑ "International Commission on Stratigraphy - Stratigraphic Guide - Chapter 9. Chronostratigraphic Units". https://stratigraphy.org/guide/chron.
7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Boggs, Sam (2011). Principles of sedimentology and stratigraphy (5th ed.). Boston, Munich: Prentice Hall. ISBN 978-0-321-74576-7.
8. ↑ 8.0 8.1 8.2 8.3 8.4 Steno, Nicolaus (1669) (in la). Nicolai Stenonis de solido intra solidvm natvraliter contento dissertationis prodromvs ad serenissimvm Ferdinandvm II .... W. Junk. https://books.google.com/books?id=xz28AAAAIAAJ.
9. ↑ 9.0 9.1 9.2 Hutton, James (1795). Theory of the Earth. 1. Edinburgh. https://www.gutenberg.org/ebooks/12861.
10. ↑ 10.0 10.1 10.2 10.3 10.4 Lyell, Sir Charles (1832) (in en). Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation. 1. London: John Murray. https://books.google.com/books?id=mmIOAAAAQAAJ.
11. ↑ Mehta, A; Barker, G C (April 1994). "The dynamics of sand". Reports on Progress in Physics 57 (4): 383–416. doi:10.1088/0034-4885/57/4/002. Bibcode: 1994RPPh...57..383M.
12. ↑ Smith, William (1816). Strata identified by organized fossils: Containing prints on colored paper of the most characteristic specimens in each stratum. doi:10.5962/bhl.title.106808. OCLC 654668607. [page needed]
13. ↑ 13.0 13.1 13.2 13.3 13.4 Michael Allaby (2020). A dictionary of geology and earth sciences (Fifth ed.). Oxford. ISBN 978-0-19-187490-1. OCLC 1137380460. [page needed]
14. ↑ 14.00 14.01 14.02 14.03 14.04 14.05 14.06 14.07 14.08 14.09 14.10 "Chapter 9. Chronostratigraphic Units". International Commission on Stratigraphy. https://stratigraphy.org/guide/chron.
15. ↑ 15.0 15.1 Aubry, Marie-Pierre; Piller, Werner E.; Gibbard, Philip L.; Harper, David A. T.; Finney, Stanley C. (March 2022). "Ratification of subseries/subepochs as formal rank/units in international chronostratigraphy". Episodes 45 (1): 97–99. doi:10.18814/epiiugs/2021/021016.
16. ↑ 16.0 16.1 "Chapter 3. Definitions and Procedures". International Commission on Stratigraphy. https://stratigraphy.org/guide/defs.
17. ↑ "Global Boundary Stratotype Section and Points". International Commission on Stratigraphy. https://stratigraphy.org/gssps/.
18. ↑ Knoll, Andrew H.; Walter, Malcolm R.; Narbonne, Guy M.; Christie-Blick, Nicholas (March 2006). "The Ediacaran Period: a new addition to the geologic time scale". Lethaia 39 (1): 13–30. doi:10.1080/00241160500409223. Bibcode: 2006Letha..39...13K.
19. ↑ Remane, Jürgen; Bassett, Michael G; Cowie, John W; Gohrbandt, Klaus H; Lane, H Richard; Michelsen, Olaf; Naiwen, Wang (September 1996). "Revised guidelines for the establishment of global chronostratigraphic standards by the International Commission on Stratigraphy (ICS)". Episodes 19 (3): 77–81. doi:10.18814/epiiugs/1996/v19i3/007.
20. ↑ Head, Martin J.; Gibbard, Philip; Salvador, Amos (June 2008). "The Quaternary: its character and definition". Episodes 31 (2): 234–238. doi:10.18814/epiiugs/2008/v31i2/009. Bibcode: 2008Episo..31..234H.
21. ↑ Gibbard, Philip L.; Head, Martin J.; Walker, Michael J. C. (February 2010). "Formal ratification of the Quaternary System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma". Journal of Quaternary Science 25 (2): 96–102. doi:10.1002/jqs.1338. Bibcode: 2010JQS....25...96G.
22. ↑ Desnoyers, J. (1829). "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" (in fr). Annales des Sciences Naturelles 16: 171–214, 402–491. https://www.biodiversitylibrary.org/item/29350#page/177/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.)
23. ↑ d'Halloy, d'O., J.-J. (1822). "Observations sur un essai de carte géologique de la France, des Pays-Bas, et des contrées voisines". Annales des Mines 7: 353–376. 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".)
24. ↑ Humboldt, Alexander von (1799) (in de). Ueber die unterirdischen Gasarten und die Mittel ihren Nachtheil zu vermindern: ein Beytrag zur Physik der praktischen Bergbaukunde. Vieweg. https://books.google.com/books?id=oZ5PAAAAcAAJ.
25. ↑ Brongniart, Alexandre (1770-1847) Auteur du texte (1829) (in fr). Tableau des terrains qui composent l'écorce du globe ou Essai sur la structure de la partie connue de la terre . Par Alexandre Brongniart,.... https://gallica.bnf.fr/ark:/12148/bpt6k255061.
26. ↑ Ogg, J.G.; Hinnov, L.A.; Huang, C. (2012). "Jurassic". The Geologic Time Scale. pp. 731–791. doi:10.1016/b978-0-444-59425-9.00026-3. ISBN 978-0-444-59425-9.
27. ↑ Murchison; Murchison, Sir Roderick Impey; Verneuil; Keyserling, Graf Alexander (1842) (in en). On the Geological Structure of the Central and Southern Regions of Russia in Europe, and of the Ural Mountains. Print. by R. and J.E. Taylor. https://books.google.com/books?id=MDoAAAAAQAAJ.
28. ↑ Phillips, John (1835) (in en). 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 .... J. Murray. https://books.google.com/books?id=-7-ZqIkYBOMC&pg=PA1.
29. ↑ Sedgwick, Adam; Murchison, Roderick Impey (January 1840). "XLIII.—On the Physical Structure of Devonshire, and on the Subdivisions and Geological Relations of its older stratified Deposits, &c.". Transactions of the Geological Society of London 5 (3): 633–703. doi:10.1144/transgslb.5.3.633.
30. ↑ Murchison, Roderick Impey (July 1835). "VII. On the silurian system of rocks". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 7 (37): 46–52. doi:10.1080/14786443508648654.
31. ↑ Lapworth, Charles (January 1879). "I.—On the Tripartite Classification of the Lower Palæozoic Rocks". Geological Magazine 6 (1): 1–15. doi:10.1017/S0016756800156560. Bibcode: 1879GeoM....6....1L.
32. ↑ Bassett, Michael G. (June 1979). "100 Years of Ordovician Geology". Episodes 2 (2): 18–21. doi:10.18814/epiiugs/1979/v2i2/003.
33. ↑ Butcher, Andy (26 May 2004). "Re: Ediacaran". LISTSERV 16.0 - AUSTRALIAN-LINGUISTICS-L Archives. http://listserv.linguistlist.org/cgi-bin/wa?A2=ind0405&L=australian-linguistics-l&D=1&P=264.
34. ↑ "Place Details: Ediacara Fossil Site – Nilpena, Parachilna, SA, Australia". Australian Heritage Database. Commonwealth of Australia. http://www.environment.gov.au/cgi-bin/ahdb/search.pl?mode=place_detail;place_id=105880.
35. ↑ 35.0 35.1 Holmes, Arthur (9 June 1911). "The association of lead with uranium in rock-minerals, and its application to the measurement of geological time". Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character 85 (578): 248–256. doi:10.1098/rspa.1911.0036. Bibcode: 1911RSPSA..85..248H.
36. ↑ "James Hutton | Father of Modern Geology, Scottish Naturalist". https://www.britannica.com/biography/James-Hutton.
37. ↑ 37.00 37.01 37.02 37.03 37.04 37.05 37.06 37.07 37.08 37.09 37.10 Fischer, Alfred G.; Garrison, Robert E. (January 2009). "The role of the Mediterranean region in the development of sedimentary geology: a historical overview". Sedimentology 56 (1): 3–41. doi:10.1111/j.1365-3091.2008.01009.x.
38. ↑ Sivin, Nathan (1995). Science in ancient China: researches and reflections. Variorum. ISBN 0-86078-492-4. OCLC 956775994. [page needed]
39. ↑ Adams, Frank Dawson (1938). The Birth and Development of the Geological Sciences. William & Wilkins Company. OCLC 1484995150. [page needed]
40. ↑ 40.0 40.1 Johnson, Chris; Bentley, Callan; Panchuk, Karla; Affolter, Matt; Layou, Karen; Jaye, Shelley; Kohrs, Russ; Inkenbrandt, Paul et al.. "Geologic Time and Relative Dating" (in en). Maricopa Open Digital Press. https://open.maricopa.edu/fallglg102/part/sedimentary-rocks-and-environments/.
41. ↑ McCurdy, Edward (1938). The notebooks of Leonardo da Vinci. New York: Reynal & Hitchcock. OCLC 2233803. Lua error: Internal error: The interpreter has terminated with signal "24".
42. ↑ 42.0 42.1 "William Smith (1769-1839)" (in en). 2008-05-08. https://earthobservatory.nasa.gov/features/WilliamSmith.
43. ↑ 43.0 43.1 Smith, William (1816). Strata identified by organized fossils: Containing prints on colored paper of the most characteristic specimens in each stratum. doi:10.5962/bhl.title.106808. Lua error: Internal error: The interpreter has terminated with signal "24".
44. ↑ Kardel, Troels; Maquet, Paul (2018). "2.27 the Prodromus to a Dissertation on a Solid Naturally Contained within a Solid". Nicolaus Steno. pp. 763–825. doi:10.1007/978-3-662-55047-2_38. ISBN 978-3-662-55046-5.
45. ↑ Burnet, Thomas (1681) (in la). Telluris Theoria Sacra: orbis nostri originen et mutationes generales, quasi am subiit aut olim subiturus est, complectens. Libri duo priores de Diluvio & Paradiso. London: G. Kettiby.
46. ↑ Moro, Anton Lazzaro (1740) (in it). De'crostacei e degli altri marini corpi che si truovano su'monti. Appresso Stefano Monti. https://books.google.com/books?id=03RBAAAAYAAJ.
47. ↑ Hutton, James (1788). "X. Theory of the Earth; or an Investigation of the Laws observable in the Composition, Dissolution, and Restoration of Land upon the Globe". Transactions of the Royal Society of Edinburgh 1 (2): 209–304. doi:10.1017/S0080456800029227.
48. ↑ Hutton, James (1795). Theory of the Earth. 2. Edinburgh. https://www.gutenberg.org/ebooks/14179.
49. ↑ Playfair, John (1802). Illustrations of the Huttonian theory of the earth. Digitised by London Natural History Museum Library. Edinburgh: Neill & Co. http://archive.org/details/NHM104643.
50. ↑ Lyell, Sir Charles (1832) (in en). Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation. 2. London: John Murray. https://books.google.com/books?id=TlwPAAAAYAAJ.
51. ↑ Lyell, Sir Charles (1834) (in en). Principles of Geology: Being an Inquiry how for the Former Changes of the Earth's Surface are Referrable to Causes Now in Operation. 3. London: John Murray. https://books.google.com/books?id=UrIJAAAAIAAJ.
52. ↑ Holmes, Arthur (1913). The age of the earth. Gerstein - University of Toronto. London, Harper. http://archive.org/details/ageofearth00holmuoft.
53. ↑ 53.0 53.1 Lewis, Cherry L. E. (January 2001). "Arthur Holmes' vision of a geological timescale". Geological Society, London, Special Publications 190 (1): 121–138. doi:10.1144/GSL.SP.2001.190.01.10. Bibcode: 2001GSLSP.190..121L.
54. ↑ Soddy, Frederick (4 December 1913). "Intra-atomic Charge". Nature 92 (2301): 399–400. doi:10.1038/092399c0. Bibcode: 1913Natur..92..399S.
55. ↑ Holmes, A. (January 1959). "A revised geological time-scale". Transactions of the Edinburgh Geological Society 17 (3): 183–216. doi:10.1144/transed.17.3.183.
56. ↑ "A Revised Geological Time-Scale". Nature 187 (4731): 27–28. July 1960. doi:10.1038/187027d0. Bibcode: 1960Natur.187T..27..
57. ↑ Harrison, James M. (March 1978). "The Roots of IUGS". Episodes 1 (1): 20–23. doi:10.18814/epiiugs/1978/v1i1/005.
58. ↑ International Union of Geological Sciences. Commission on Stratigraphy (1986). Guidelines and statutes of the International Commission on Stratigraphy (ICS). J. W. Cowie. Frankfurt a.M.: Herausgegeben von der Senckenbergischen Naturforschenden Gesellschaft. ISBN 3-924500-19-3. OCLC 14352783. Lua error: Internal error: The interpreter has terminated with signal "24".
59. ↑ W. B. Harland (1982). A geologic time scale. Cambridge [England]: Cambridge University Press. ISBN 0-521-24728-4. OCLC 8387993. Lua error: Internal error: The interpreter has terminated with signal "24".
60. ↑ W. B. Harland (1990). A geologic time scale 1989. Cambridge: Cambridge University Press. ISBN 0-521-38361-7. OCLC 20930970. Lua error: Internal error: The interpreter has terminated with signal "24".
61. ↑ F. M. Gradstein; James G. Ogg; A. Gilbert Smith (2004). A geologic time scale 2004. Cambridge, UK: Cambridge University Press. ISBN 0-511-08201-0. OCLC 60770922. Lua error: Internal error: The interpreter has terminated with signal "24".
62. ↑ Gradstein, Felix M.; Ogg, James G.; van Kranendonk, Martin (23 July 2008). "On the Geologic Time Scale 2008". Newsletters on Stratigraphy 43 (1): 5–13. doi:10.1127/0078-0421/2008/0043-0005. Bibcode: 2008NewSt..43....5G.
63. ↑ 63.00 63.01 63.02 63.03 63.04 63.05 63.06 63.07 63.08 63.09 63.10 63.11 63.12 F. M. Gradstein (2012). The geologic time scale 2012. Volume 2 (1st ed.). Amsterdam: Elsevier. ISBN 978-0-444-59448-8. OCLC 808340848. Lua error: Internal error: The interpreter has terminated with signal "24".
64. ↑ 64.0 64.1 Ogg, James G. (2016). A concise geologic time scale 2016. Gabi Ogg, F. M. Gradstein. Amsterdam, Netherlands: Elsevier. ISBN 978-0-444-59468-6. OCLC 949988705. Lua error: Internal error: The interpreter has terminated with signal "24".
65. ↑ 65.0 65.1 F. M. Gradstein; James G. Ogg; Mark D. Schmitz; Gabi Ogg (2020). Geologic time scale 2020. Amsterdam, Netherlands. ISBN 978-0-12-824361-9. OCLC 1224105111. Lua error: Internal error: The interpreter has terminated with signal "24".
66. ↑ Crutzen, Paul J.; Stoermer, Eugene F. (2021). "The 'Anthropocene' (2000)". Paul J. Crutzen and the Anthropocene: A New Epoch in Earth's History. The Anthropocene: Politik—Economics—Society—Science. 1. pp. 19–21. doi:10.1007/978-3-030-82202-6_2. ISBN 978-3-030-82201-9.
67. ↑ "Working Group on the 'Anthropocene' | Subcommission on Quaternary Stratigraphy" (in en-US). https://quaternary.stratigraphy.org/working-groups/anthropocene/.
68. ↑ Gibbard, Philip L.; Bauer, Andrew M.; Edgeworth, Matthew; Ruddiman, William F.; Gill, Jacquelyn L.; Merritts, Dorothy J.; Finney, Stanley C.; Edwards, Lucy E. et al. (December 2022). "A practical solution: the Anthropocene is a geological event, not a formal epoch". Episodes 45 (4): 349–357. doi:10.18814/epiiugs/2021/021029. Bibcode: 2021Episo..45..349G.
69. ↑ Head, Martin J.; Steffen, Will; Fagerlind, David; Waters, Colin N.; Poirier, Clement; Syvitski, Jaia; Zalasiewicz, Jan A.; Barnosky, Anthony D. et al. (December 2022). "The Great Acceleration is real and provides a quantitative basis for the proposed Anthropocene Series/Epoch". Episodes 45 (4): 359–376. doi:10.18814/epiiugs/2021/021031.
70. ↑ Zalasiewicz, Jan; Waters, Colin N.; Ellis, Erle C.; Head, Martin J.; Vidas, Davor; Steffen, Will; Thomas, Julia Adeney; Horn, Eva et al. (2021). "The Anthropocene: Comparing Its Meaning in Geology (Chronostratigraphy) with Conceptual Approaches Arising in Other Disciplines". Earth's Future 9 (3). doi:10.1029/2020EF001896. Bibcode: 2021EaFut...901896Z.
71. ↑ Bauer, Andrew M.; Edgeworth, Matthew; Edwards, Lucy E.; Ellis, Erle C.; Gibbard, Philip; Merritts, Dorothy J. (16 September 2021). "Anthropocene: event or epoch?". Nature 597 (7876): 332. doi:10.1038/d41586-021-02448-z. PMID 34522014. Bibcode: 2021Natur.597..332B.
72. ↑ Subramanian, Meera (21 May 2019). "Anthropocene now: influential panel votes to recognize Earth's new epoch". Nature. doi:10.1038/d41586-019-01641-5. PMID 32433629.
73. ↑ "Working Group on the 'Anthropocene'". International Commission on Stratigraphy. https://quaternary.stratigraphy.org/working-groups/anthropocene.
74. ↑ "Joint statement by the IUGS and ICS on the vote by the ICS Subcommission on Quaternary Stratigraphy". https://stratigraphy.org/news/152.
75. ↑ Bleeker, W. (2005). "Toward a 'natural' Precambrian time scale". A Geologic Time Scale 2004. pp. 141–146. doi:10.1017/cbo9780511536045.011. ISBN 978-0-521-78673-7.
76. ↑ Strachan, R.; Murphy, J.B.; Darling, J.; Storey, C.; Shields, G. (2020). "Precambrian (4.56–1 Ga)". Geologic Time Scale 2020. pp. 481–493. doi:10.1016/b978-0-12-824360-2.00016-4. ISBN 978-0-12-824360-2.
77. ↑ 77.0 77.1 77.2 Goldblatt, C.; Zahnle, K. J.; Sleep, N. H.; Nisbet, E. G. (2010). "The Eons of Chaos and Hades". Solid Earth 1 (1): 1–3. doi:10.5194/se-1-1-2010. Bibcode: 2010SolE....1....1G.
78. ↑ Chambers, John E. (July 2004). "Planetary accretion in the inner Solar System". Earth and Planetary Science Letters 223 (3–4): 241–252. doi:10.1016/j.epsl.2004.04.031. Bibcode: 2004E&PSL.223..241C. http://www.astro.washington.edu/courses/astro321/Chambers_EPSL_04.pdf.
79. ↑ El Albani, Abderrazak et al. (2014). "The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity". PLOS ONE 9 (6). doi:10.1371/journal.pone.0099438. PMID 24963687. Bibcode: 2014PLoSO...999438E.
80. ↑ Albani, Abderrazak El; Bengtson, Stefan; Canfield, Donald E.; Bekker, Andrey; Macchiarelli, Roberto; Mazurier, Arnaud; Hammarlund, Emma U.; Boulvais, Philippe et al. (July 2010). "Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago". Nature 466 (7302): 100–104. doi:10.1038/nature09166. PMID 20596019. Bibcode: 2010Natur.466..100A.
81. ↑ "Geological time scale". Digital Atlas of Ancient Life. Paleontological Research Institution. https://www.digitalatlasofancientlife.org/learn/geological-time/geological-time-scale/.
82. ↑ "International Commission on Stratigraphy". International Geological Time Scale. https://stratigraphy.org/.
83. ↑ Ran, Min; Chen, Liang (June 2019). "The 4.2 ka BP climatic event and its cultural responses". Quaternary International 521: 158–167. doi:10.1016/j.quaint.2019.05.030.
84. ↑ 84.0 84.1 84.2 Pratap, Shailendra; Markonis, Yannis (31 May 2022). "The response of the hydrological cycle to temperature changes in recent and distant climatic history". Progress in Earth and Planetary Science 9 (1). doi:10.1186/s40645-022-00489-0.
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87. ↑ Cotterill, Carol J.; Phillips, Emrys; James, Leo; Forsberg, Carl Fredrik; Tjelta, Tor Inge; Carter, Gareth; Dove, Dayton (September 2017). "The evolution of the Dogger Bank, North Sea: A complex history of terrestrial, glacial and marine environmental change". Quaternary Science Reviews 171: 136–153. doi:10.1016/j.quascirev.2017.07.006.
88. ↑ Solihuddin, Tubagus (31 August 2014). "A Drowning Sunda Shelf Model during Last Glacial Maximum (LGM) and Holocene: A Review". Indonesian Journal on Geoscience 1 (2): 99–107. doi:10.17014/ijog.1.2.99-107.
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92. ↑ Koshnaw, Renas I.; Schlunegger, Fritz; Stockli, Daniel F. (3 November 2021). "Detrital zircon provenance record of the Zagros mountain building from the Neotethys obduction to the Arabia–Eurasia collision, NW Zagros fold–thrust belt, Kurdistan region of Iraq". Solid Earth 12 (11): 2479–2501. doi:10.5194/se-12-2479-2021.
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100. ↑ Ogg, J.G.; Chen, Z.-Q.; Orchard, M.J.; Jiang, H.S. (2020). "The Triassic Period". Geologic Time Scale 2020. pp. 903–953. doi:10.1016/B978-0-12-824360-2.00025-5. ISBN 978-0-12-824360-2.
101. ↑ 101.0 101.1 101.2 101.3 Henderson, C.M.; Davydov And, V.I.; Wardlaw, B.R.; Gradstein, F.M.; Hammer, O. (2012). "The Permian Period". The Geologic Time Scale. pp. 653–679. doi:10.1016/B978-0-444-59425-9.00024-X. ISBN 978-0-444-59425-9.
102. ↑ Puchkov, Victor N. (January 2009). "The evolution of the Uralian orogen". Geological Society, London, Special Publications 327 (1): 161–195. doi:10.1144/SP327.9. Bibcode: 2009GSLSP.327..161P.
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## Further reading

* Aubry, Marie-Pierre; Van Couvering, John A.; Christie-Blick, Nicholas; Landing, Ed; Pratt, Brian R.; Owen, Donald E.; Ferrusquia-Villafranca, Ismael (2009). "Terminology of geological time: Establishment of a community standard". Stratigraphy 6 (2): 100–105. doi:10.7916/D8DR35JQ.
* Gradstein, Felix M.; Ogg, James G. (June 2004). "Geologic Time Scale 2004 – why, how, and where next!". Lethaia 37 (2): 175–181. doi:10.1080/00241160410006483. Bibcode: 2004Letha..37..175G.
* A Geologic Time Scale 2004. 2005. doi:10.1017/CBO9780511536045. ISBN 978-0-521-78673-7.
* Gradstein, Felix M.; Ogg, James G.; Smith, Alan G.; Bleeker, Wouter; Laurens, Lucas, J. (June 2004). "A new Geologic Time Scale, with special reference to Precambrian and Neogene". Episodes 27 (2): 83–100. doi:10.18814/epiiugs/2004/v27i2/002. Template:CORE output.
* Ialenti, Vincent (28 September 2014). "Embracing 'Deep Time' Thinking.". NPR (NPR Cosmos & Culture). https://www.npr.org/sections/13.7/2014/09/28/351692717/embracing-deep-time-thinking.
* Ialenti, Vincent (21 September 2014). "Pondering 'Deep Time' Could Inspire New Ways To View Climate Change.". NPR (NPR Cosmos & Culture). https://www.npr.org/sections/13.7/2014/09/21/350344129/pondering-deep-time-could-inspire-new-ways-to-view-climate-change.
* Knoll, Andrew H.; Walter, Malcolm R.; Narbonne, Guy M.; Christie-Blick, Nicholas (30 July 2004). "A New Period for the Geologic Time Scale". Science 305 (5684): 621–622. doi:10.1126/science.1098803. PMID 15286353.
* Levin, Harold L. (2010). "Time and Geology". The Earth Through Time. Hoboken, New Jersey: John Wiley & Sons. ISBN 978-0-470-38774-0. https://books.google.com/books?id=D0yl7Cqsu78C&pg=PA29.
* Montenari, Michael, ed (2016). Stratigraphy & Timescales. Academic Press. ISBN 978-0-12-811550-3. https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/1/suppl/C.
* Montenari, Michael (2017). Advances in Sequence Stratigraphy (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-12-813077-3. https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/2/suppl/C.
* Montenari, Michael, ed (2018). Cyclostratigraphy and Astrochronology (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-12-815098-6. https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/3/suppl/C.
* Montenari, Michael, ed (2019). Case Studies in Isotope Stratigraphy (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-12-817552-1. https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/4/suppl/C.
* Montenari, Michael, ed (2020). Carbon Isotope Stratigraphy (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-12-820991-2. https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/5/suppl/C.
* Montenari, Michael, ed (2021). Calcareous Nannofossil Biostratigraphy (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-12-824624-5. https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/6/suppl/C.
* Montenari, Michael, ed (2022). Integrated Quaternary Stratigraphy (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-323-98913-8. https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/7/suppl/C.
* Montenari, Michael, ed (2023). Stratigraphy of Geo- and Biodynamic Processes (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-323-99242-8. https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/8/suppl/C.
* Nichols, Gary (2013). Sedimentology and Stratigraphy. John Wiley & Sons. ISBN 978-1-118-68777-2.
* Williams, Aiden (2019). Sedimentology and Stratigraphy. Callisto Reference. ISBN 978-1-64116-075-9.

## External links

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* The current version of the International Chronostratigraphic Chart can be found at stratigraphy.org/chart
* Interactive version of the International Chronostratigraphic Chart is found at stratigraphy.org/timescale
* A list of current Global Boundary Stratotype and Section Points is found at stratigraphy.org/gssps
* NASA: Geologic Time (archived 18 April 2005)
* GSA: Geologic Time Scale (archived 20 January 2019)
* British Geological Survey: Geological Timechart
* GeoWhen Database (archived 23 June 2004)
* National Museum of Natural History – Geologic Time (archived 11 November 2005)
* SeeGrid: Geological Time Systems. . Information model for the geologic time scale.
* Exploring Time from Planck Time to the lifespan of the universe
* Lane, Alfred C, and Marble, John Putman 1937. Report of the Committee on the measurement of geologic time
* Lessons for Children on Geologic Time (archived 14 July 2011)
* Deep Time – A History of the Earth : Interactive Infographic
* Geology Buzz: Geologic Time Scale. .

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*[c.]: circa