Geologic time scale#Proposed Precambrian timeline

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

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

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.{{Cite journal |last1=Shields |first1=Graham A. |last2=Strachan |first2=Robin A. |last3=Porter |first3=Susannah M. |last4=Halverson |first4=Galen P. |last5=Macdonald |first5=Francis A. |last6=Plumb |first6=Kenneth A. |last7=de Alvarenga |first7=Carlos J. |last8=Banerjee |first8=Dhiraj M. |last9=Bekker |first9=Andrey |last10=Bleeker |first10=Wouter |last11=Brasier |first11=Alexander |date=2022 |title=A template for an improved rock-based subdivision of the pre-Cryogenian timescale |journal=Journal of the Geological Society |language=en |volume=179 |issue=1 |pages=jgs2020–222 |doi=10.1144/jgs2020-222 |bibcode=2022JGSoc.179..222S |s2cid=236285974 |issn=0016-7649|doi-access=free }}{{Citation |last1=Van Kranendonk |first1=Martin J. |title=A Chronostratigraphic Division of the Precambrian |date=2012 |work=The Geologic Time Scale |pages=299–392 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780444594259000160 |access-date=2022-04-05 |publisher=Elsevier |language=en |doi=10.1016/b978-0-444-59425-9.00016-0 |isbn=978-0-444-59425-9 |last2=Altermann |first2=Wladyslaw |last3=Beard |first3=Brian L. |last4=Hoffman |first4=Paul F. |last5=Johnson |first5=Clark M. |last6=Kasting |first6=James F. |last7=Melezhik |first7=Victor A. |last8=Nutman |first8=Allen P.}}

Historically, regional geologic time scales were used 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.{{Cite web |title=International Commission on Stratigraphy - Stratigraphic Guide - Chapter 9. Chronostratigraphic Units |url=https://stratigraphy.org/guide/chron |access-date=2024-04-16 |website=stratigraphy.org}}{{Cite book |last=Boggs |first=Sam |title=Principles of sedimentology and stratigraphy |date=2011 |publisher=Prentice Hall |isbn=978-0-321-74576-7 |edition=5th |location=Boston, Munich}}

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. 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. However, it is now known that not all sedimentary layers are deposited purely horizontally,{{Cite journal |last1=Mehta |first1=A |last2=Barker |first2=G C |date=1994-04-01 |title=The dynamics of sand |url=https://iopscience.iop.org/article/10.1088/0034-4885/57/4/002 |journal=Reports on Progress in Physics |volume=57 |issue=4 |pages=383–416 |doi=10.1088/0034-4885/57/4/002 |issn=0034-4885}} 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. 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.

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.

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. 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.{{Cite book |last=Smith |first=William |url=http://www.biodiversitylibrary.org/bibliography/106808 |title=Strata identified by organized fossils, containing prints on colored paper of the most characteristic specimens in each stratum |date=1816-06-01 |publisher=W. Arding |location=London |doi=10.5962/bhl.title.106808}} This allows for a correlation of strata even when the horizon between them is not continuous.

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

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

• An {{visible anchor|eon}} is the largest geochronologic time unit and is equivalent to a chronostratigraphic eonothem.{{Cite book |url=https://www.worldcat.org/oclc/1137380460 |title=A dictionary of geology and earth sciences |date=2020 |author=Michael Allaby |isbn=978-0-19-187490-1 |edition=Fifth |location=Oxford |oclc=1137380460}} There are four formally defined eons: the Hadean, Archean, Proterozoic and Phanerozoic.
• An {{visible anchor|era}} is the second largest geochronologic time unit and is equivalent to a chronostratigraphic erathem. There are ten defined eras: the Eoarchean, Paleoarchean, Mesoarchean, Neoarchean, Paleoproterozoic, Mesoproterozoic, Neoproterozoic, Paleozoic, Mesozoic and Cenozoic, with none from the Hadean eon.
• A {{visible anchor|period}} is equivalent to a chronostratigraphic system. There are 22 defined periods, with the current being the Quaternary period. As an exception, two subperiods are used for the Carboniferous Period.
• An {{visible anchor|epoch}} is the second smallest geochronologic unit. It is equivalent to a chronostratigraphic series. 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. The use of subepochs as formal units in international chronostratigraphy was ratified in 2022.{{Cite journal |last1=Aubry |first1=Marie-Pierre |last2=Piller |first2=Werner E. |last3=Gibbard |first3=Philip L. |last4=Harper |first4=David A. T. |last5=Finney |first5=Stanley C. |date=2022-03-01 |title=Ratification of subseries/subepochs as formal rank/units in international chronostratigraphy |journal=Episodes |language=en |volume=45 |issue=1 |pages=97–99 |doi=10.18814/epiiugs/2021/021016 |s2cid=240772165 |issn=0705-3797|doi-access=free }}
• An {{visible anchor|age}} is the smallest hierarchical geochronologic unit. It is equivalent to a chronostratigraphic stage. There are 96 formal and five informal ages. The current age is the Meghalayan.
• A {{visible anchor|chron}} is a non-hierarchical formal geochronology unit of unspecified rank and is equivalent to a chronostratigraphic chronozone. These correlate with magnetostratigraphic, lithostratigraphic, or biostratigraphic units as they are based on previously defined stratigraphic units or geologic features.

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

Rocks representing a given chronostratigraphic unit are that chronostratigraphic unit, and the time they were laid down in is the geochronologic unit, e.g., the rocks that represent the Silurian System {{em|are}} the Silurian System and they were deposited {{em|during}} the Silurian Period. This definition means the numeric age of a geochronologic unit can be changed (and is more often subject to change) when refined by geochronometry while the equivalent chronostratigraphic unit (the revision of which is less frequent) remains unchanged. For example, in early 2022, the boundary between the Ediacaran and Cambrian 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.

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

A {{em|chronostratigraphic unit}}{{Anchor|Chronostratigraphic unit}} is a body of rock, layered or unlayered, that is defined between specified stratigraphic horizons which represent specified intervals of geologic time. They include all rocks representative of a specific interval of geologic time, and only this time span. Eonothem, erathem, system, series, subseries, stage, and substage are the hierarchical chronostratigraphic units.

A {{em|geochronologic unit}}{{Anchor|Geochronologic unit}} is a subdivision of geologic time. It is a numeric representation of an intangible property (time).{{Cite web |title=Chapter 3. Definitions and Procedures |url=https://stratigraphy.org/guide/defs |access-date=2022-04-02 |website=stratigraphy.org |publisher=International Commission on Stratigraphy}} These units are arranged in a hierarchy: eon, era, period, epoch, subepoch, age, and subage.

{{em|Geochronology}} is the scientific branch of geology that aims to determine the age of rocks, fossils, and sediments either through absolute (e.g., radiometric dating) or relative means (e.g., stratigraphic position, paleomagnetism, stable isotope ratios).

{{em|Geochronometry}} is the field of geochronology that numerically quantifies geologic time.

A {{em|Global Boundary Stratotype Section and Point}} (GSSP) is an internationally agreed-upon reference point on a stratigraphic section that defines the lower boundaries of stages on the geologic time scale.{{Cite web |title=Global Boundary Stratotype Section and Points |url=https://stratigraphy.org/gssps/ |access-date=2022-04-02 |website=stratigraphy.org |publisher=International Commission on Stratigraphy}} (Recently this has been used to define the base of a system){{Cite journal |last1=Knoll |first1=Andrew |last2=Walter |first2=Malcolm |last3=Narbonne |first3=Guy |last4=Christie-Blick |first4=Nicholas |date=2006 |title=The Ediacaran Period: a new addition to the geologic time scale |url=http://doi.wiley.com/10.1080/00241160500409223 |journal=Lethaia |language=en |volume=39 |issue=1 |pages=13–30 |doi=10.1080/00241160500409223|bibcode=2006Letha..39...13K }}

A {{em|Global Standard Stratigraphic Age}} (GSSA){{Cite journal |last1=Remane |first1=Jürgen |last2=Bassett |first2=Michael G |last3=Cowie |first3=John W |last4=Gohrbandt |first4=Klaus H |last5=Lane |first5=H Richard |last6=Michelsen |first6=Olaf |last7=Naiwen |first7=Wang |last8=the cooperation of members of ICS |date=1996-09-01 |title=Revised guidelines for the establishment of global chronostratigraphic standards by the International Commission on Stratigraphy (ICS) |journal=Episodes |language=en |volume=19 |issue=3 |pages=77–81 |doi=10.18814/epiiugs/1996/v19i3/007 |issn=0705-3797|doi-access=free }} is a numeric-only, chronologic reference point used to define the base of geochronologic units prior to the Cryogenian. These points are arbitrarily defined. They are used where GSSPs have not yet been established. Research is ongoing to define GSSPs for the base of all units that are currently defined by GSSAs.

The standard international units of the geologic time scale are published by the International Commission on Stratigraphy on the International Chronostratigraphic Chart; however, regional terms are still in use in some areas. The numeric values on the International Chronostratigrahpic Chart are represented by the unit Ma (megaannum, for 'million years'). For example, {{Period start|Jurassic}} {{Period start error|Jurassic}} Ma, the lower boundary of the Jurassic Period, is defined as 201,400,000 years old with an uncertainty of 200,000 years. Other SI prefix 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).

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.

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

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

The most modern geological time scale was not formulated until 1911{{Cite journal |last1=Holmes |first1=Arthur |date=1911-06-09 |title=The association of lead with uranium in rock-minerals, and its application to the measurement of geological time |journal=Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character |volume=85 |issue=578 |pages=248–256 |bibcode=1911RSPSA..85..248H |doi=10.1098/rspa.1911.0036 |issn=0950-1207 |doi-access=free}} 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.{{Cite web |title=James Hutton {{!}} Father of Modern Geology, Scottish Naturalist {{!}} Britannica |url=https://www.britannica.com/biography/James-Hutton |access-date=2024-12-03 |website=www.britannica.com |language=en}} 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.{{Cite journal |last1=Fischer |first1=Alfred G. |last2=Garrison |first2=Robert E. |date=2009 |title=The role of the Mediterranean region in the development of sedimentary geology: a historical overview |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-3091.2008.01009.x |journal=Sedimentology |language=en |volume=56 |issue=1 |pages=3–41 |bibcode=2009Sedim..56....3F |doi=10.1111/j.1365-3091.2008.01009.x |s2cid=128604255}} 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{{Cite book |last=Sivin |first=Nathan |url=http://worldcat.org/oclc/956775994 |title=Science in ancient China: researches and reflections |date=1995 |publisher=Variorum |isbn=0-86078-492-4 |oclc=956775994}} (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. 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. Avicenna also recognized fossils as "petrifications of the bodies of plants and animals",{{Cite book |last=Adams |first=Frank D. |url=http://worldcat.org/oclc/165626104 |title=The Birth and Development of the Geological Sciences |date=1938 |publisher=Williams & Wilkins |isbn=0-486-26372-X |oclc=165626104}} 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.{{Cite journal |last1=Johnson |first1=Chris |last2=Bentley |first2=Callan |last3=Panchuk |first3=Karla |last4=Affolter |first4=Matt |last5=Layou |first5=Karen |last6=Jaye |first6=Shelley |last7=Kohrs |first7=Russ |last8=Inkenbrandt |first8=Paul |last9=Mosher |first9=Cam |last10=Ricketts |first10=Brian |last11=Estrada |first11=Charlene |title=Geologic Time and Relative Dating |url=https://open.maricopa.edu/fallglg102/part/sedimentary-rocks-and-environments/ |journal=Maricopa Open Digital Press |language=en}} 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. 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':{{Cite book |last=McCurdy |first=Edward |url=https://www.worldcat.org/search?q=no:2233803&qt=advanced&dblist=638 |title=The notebooks of Leonardo da Vinci |date=1938 |publisher=Reynal & Hitchcock |location=New York |language=English |oclc=2233803}}

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

File:Sketch of the Succession pf Strata and their relative Altitudes.jpg

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. 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." Later, in the 19th century, academics further developed theories on stratification. William Smith, often referred to as the "Father of Geology" 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”.{{Cite web |date=2008-05-08 |title=William Smith (1769-1839) |url=https://earthobservatory.nasa.gov/features/WilliamSmith |access-date=2024-12-02 |website=earthobservatory.nasa.gov |language=en}} 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.{{Cite book |last1=Smith |first1=William |url=https://www.biodiversitylibrary.org/bibliography/106808 |title=Strata identified by organized fossils : containing prints on colored paper of the most characteristic specimens in each stratum |last2=Smith |first2=William |date=1816 |publisher=Printed by W. Arding ..., and sold by the author ..., J. Sowerby ..., Sherwood, Neely, and Jones, and Longman, Hurst, Rees, Orme, and Brown ..., and by all booksellers |location=London |doi=10.5962/bhl.title.106808}} 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."

Niels Stensen, more commonly known as Nicolas Steno (1638–1686), is credited with establishing four of the guiding principles of stratigraphy. In De solido intra solidum naturaliter contento dissertationis prodromus Steno states:{{Cite book |last=Steno |first=Nicolaus |url=https://books.google.com/books?id=xz28AAAAIAAJ |title=Nicolai Stenonis de solido intra solidvm natvraliter contento dissertationis prodromvs ad serenissimvm Ferdinandvm II ... |date=1669 |publisher=W. Junk |language=la}}{{Citation |last1=Kardel |first1=Troels |date=2018 |url=http://link.springer.com/10.1007/978-3-662-55047-2_38 |work=Nicolaus Steno |pages=763–825 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |language=en |doi=10.1007/978-3-662-55047-2_38 |isbn=978-3-662-55046-5 |access-date=2022-04-20 |last2=Maquet |first2=Paul|title=2.27 the Prodromus to a Dissertation on a Solid Naturally Contained within a Solid }}

• 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. 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

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".{{Cite book |last=Burnet |first=Thomas |title=Telluris Theoria Sacra: orbis nostri originen et mutationes generales, quasi am subiit aut olim subiturus est, complectens. Libri duo priores de Diluvio & Paradiso |publisher=G. Kettiby |year=1681 |location=London |language=la}} Anton Moro (1687–1784) also used primary and secondary divisions for rock units but his mechanism was volcanic.{{Cite book |last=Moro |first=Anton Lazzaro |url=https://books.google.com/books?id=03RBAAAAYAAJ |title=De'crostacei e degli altri marini corpi che si truovano su'monti |date=1740 |publisher=Appresso Stefano Monti |language=it}} 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. 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.{{Cite journal |last=Hutton |first=James |date=1788 |title=X. Theory of the Earth; or an Investigation of the Laws observable in the Composition, Dissolution, and Restoration of Land upon the Globe . |url=https://www.cambridge.org/core/product/identifier/S0080456800029227/type/journal_article |journal=Transactions of the Royal Society of Edinburgh |language=en |volume=1 |issue=2 |pages=209–304 |doi=10.1017/S0080456800029227 |s2cid=251578886 |issn=0080-4568}}{{Cite book |last=Hutton |first=James |url=https://www.gutenberg.org/ebooks/12861 |title=Theory of the Earth |year=1795 |volume=1 |location=Edinburgh}}{{Cite book |last=Hutton |first=James |url=https://www.gutenberg.org/ebooks/14179 |title=Theory of the Earth |year=1795 |volume=2 |location=Edinburgh}} Hutton's theory would later become known as uniformitarianism, popularised by John Playfair{{Cite book |last=Playfair |first=John |url=http://archive.org/details/NHM104643 |title=Illustrations of the Huttonian theory of the earth |date=1802 |publisher=Neill & Co |others=Digitised by London Natural History Museum Library |location=Edinburgh}} (1748–1819) and later Charles Lyell (1797–1875) in his Principles of Geology.{{Cite book |last=Lyell |first=Sir Charles |url=https://books.google.com/books?id=mmIOAAAAQAAJ |title=Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation |date=1832 |publisher=John Murray |volume=1 |location=London |language=en}}{{Cite book |last=Lyell |first=Sir Charles |url=https://books.google.com/books?id=TlwPAAAAYAAJ |title=Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation |date=1832 |publisher=John Murray |volume=2 |location=London |language=en}}{{Cite book |last=Lyell |first=Sir Charles |url=https://books.google.com/books?id=UrIJAAAAIAAJ |title=Principles of Geology: Being an Inquiry how for the Former Changes of the Earth's Surface are Referrable to Causes Now in Operation |date=1834 |publisher=John Murray |volume=3 |location=London |language=en}} 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.

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. 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. 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.{{Cite book |last=Holmes |first=Arthur |url=http://archive.org/details/ageofearth00holmuoft |title=The age of the earth |date=1913 |publisher=London, Harper |others=Gerstein - University of Toronto}}{{Cite journal |last=Lewis |first=Cherry L. E. |date=2001 |title=Arthur Holmes' vision of a geological timescale |url=http://sp.lyellcollection.org/lookup/doi/10.1144/GSL.SP.2001.190.01.10 |journal=Geological Society, London, Special Publications |language=en |volume=190 |issue=1 |pages=121–138 |doi=10.1144/GSL.SP.2001.190.01.10 |bibcode=2001GSLSP.190..121L |s2cid=128686640 |issn=0305-8719}} The discovery of isotopes in 1913{{Cite journal |last=Soddy |first=Frederick |date=1913-12-04 |title=Intra-atomic Charge |url=https://www.nature.com/articles/092399c0 |journal=Nature |language=en |volume=92 |issue=2301 |pages=399–400 |doi=10.1038/092399c0 |bibcode=1913Natur..92..399S |s2cid=3965303 |issn=0028-0836}} 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.{{Cite journal |last=Holmes |first=A. |date=1959-01-01 |title=A revised geological time-scale |url=http://trned.lyellcollection.org/cgi/doi/10.1144/transed.17.3.183 |journal=Transactions of the Edinburgh Geological Society |language=en |volume=17 |issue=3 |pages=183–216 |doi=10.1144/transed.17.3.183 |s2cid=129166282 |issn=0371-6260}}{{Cite journal |date=1960 |title=A Revised Geological Time-Scale |journal=Nature |language=en |volume=187 |issue=4731 |pages=27–28 |doi=10.1038/187027d0 |bibcode=1960Natur.187T..27. |s2cid=4179334 |issn=0028-0836|doi-access=free }}

The establishment of the IUGS in 1961{{Cite journal |last=Harrison |first=James M. |title=The Roots of IUGS |date=1978-03-01 |journal=Episodes |volume=1 |issue=1 |pages=20–23 |doi=10.18814/epiiugs/1978/v1i1/005 |issn=0705-3797|doi-access=free }} and acceptance of the Commission on Stratigraphy (applied in 1965){{Cite book |author=International Union of Geological Sciences. Commission on Stratigraphy |url=https://www.worldcat.org/oclc/14352783 |title=Guidelines and statutes of the International Commission on Stratigraphy (ICS) |date=1986 |publisher=Herausgegeben von der Senckenbergischen Naturforschenden Gesellschaft |others=J. W. Cowie |isbn=3-924500-19-3 |location=Frankfurt a.M. |oclc=14352783}} 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".

Following on from Holmes, several A Geological Time Scale books were published in 1982,{{Cite book |url=https://www.worldcat.org/oclc/8387993 |title=A geologic time scale |date=1982 |publisher=Cambridge University Press |author=W. B. Harland |isbn=0-521-24728-4 |location=Cambridge [England] |oclc=8387993}} 1989,{{Cite book |url=https://www.worldcat.org/oclc/20930970 |title=A geologic time scale 1989 |date=1990 |publisher=Cambridge University Press |author=W. B. Harland |isbn=0-521-38361-7 |location=Cambridge |oclc=20930970}} 2004,{{Cite book |url=https://www.worldcat.org/oclc/60770922 |title=A geologic time scale 2004 |date=2004 |publisher=Cambridge University Press |author1=F. M. Gradstein |author2=James G. Ogg |author3=A. Gilbert Smith |isbn=0-511-08201-0 |location=Cambridge, UK |oclc=60770922}} 2008,{{Cite journal |last1=Gradstein |first1=Felix M. |last2=Ogg |first2=James G. |last3=van Kranendonk |first3=Martin |date=2008-07-23 |title=On the Geologic Time Scale 2008 |url=http://www.schweizerbart.de/papers/nos/detail/43/63825/On_the_Geologic_Time_Scale_2008?af=crossref |journal=Newsletters on Stratigraphy |language=en |volume=43 |issue=1 |pages=5–13 |doi=10.1127/0078-0421/2008/0043-0005 |issn=0078-0421}} 2012,{{Cite book |url=https://www.worldcat.org/oclc/808340848 |title=The geologic time scale 2012. Volume 2 |date=2012 |publisher=Elsevier |author=F. M. Gradstein |isbn=978-0-444-59448-8 |edition=1st |location=Amsterdam |oclc=808340848}} 2016,{{Cite book |last=Ogg |first=James G. |url=https://www.worldcat.org/oclc/949988705 |title=A concise geologic time scale 2016 |date=2016 |publisher=Elsevier |others=Gabi Ogg, F. M. Gradstein |isbn=978-0-444-59468-6 |location=Amsterdam, Netherlands |oclc=949988705}} and 2020.{{Cite book |url=https://www.worldcat.org/oclc/1224105111 |title=Geologic time scale 2020 |date=2020 |author1=F. M. Gradstein |author2=James G. Ogg |author3=Mark D. Schmitz |author4=Gabi Ogg |isbn=978-0-12-824361-9 |location=Amsterdam, Netherlands |oclc=1224105111}} 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. Subsequent Geologic Time Scale books (2016 and 2020) are commercial publications with no oversight from the ICS, and do not entirely conform to the chart produced by the ICS. The ICS produced GTS charts are versioned (year/month) beginning at v2013/01. At least one new version is published each year incorporating any changes ratified by the ICS since the prior version.

{{Timeline geological timescale}}

{{Main|Anthropocene}}

First suggested in 2000,{{Citation |last1=Crutzen |first1=Paul J. |title=The 'Anthropocene' (2000) |date=2021 |url=https://link.springer.com/10.1007/978-3-030-82202-6_2 |work=Paul J. Crutzen and the Anthropocene: A New Epoch in Earth's History |volume=1 |pages=19–21 |editor-last=Benner |editor-first=Susanne |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-82202-6_2 |isbn=978-3-030-82201-9 |access-date=2022-04-15 |last2=Stoermer |first2=Eugene F. |series=The Anthropocene: Politik—Economics—Society—Science |s2cid=245639062 |editor2-last=Lax |editor2-first=Gregor |editor3-last=Crutzen |editor3-first=Paul J. |editor4-last=Pöschl |editor4-first=Ulrich}} 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.{{Cite web |title=Working Group on the 'Anthropocene' {{!}} Subcommission on Quaternary Stratigraphy |url=https://quaternary.stratigraphy.org/working-groups/anthropocene/ |archive-url=https://web.archive.org/web/20220407193255/https://quaternary.stratigraphy.org/working-groups/anthropocene/ |archive-date=2022-04-07 |access-date=2022-04-17 |language=en-US}} {{As of|2022|April}} the Anthropocene has not been ratified by the ICS; however, in May 2019 the Anthropocene Working Group voted in favour of submitting a formal proposal to the ICS for the establishment of the Anthropocene Series/Epoch.{{Cite journal |last=Subramanian |first=Meera |date=2019-05-21 |title=Anthropocene now: influential panel votes to recognise Earth's new epoch |url=http://www.nature.com/articles/d41586-019-01641-5 |journal=Nature |language=en |pages=d41586–019–01641–5 |doi=10.1038/d41586-019-01641-5 |pmid=32433629 |s2cid=182238145 |issn=0028-0836}} Nevertheless, the definition of the Anthropocene as a geologic time period rather than a geologic event remains controversial and difficult.{{Cite journal |last1=Gibbard |first1=Philip L. |last2=Bauer |first2=Andrew M. |last3=Edgeworth |first3=Matthew |last4=Ruddiman |first4=William F. |last5=Gill |first5=Jacquelyn L. |last6=Merritts |first6=Dorothy J. |last7=Finney |first7=Stanley C. |last8=Edwards |first8=Lucy E. |last9=Walker |first9=Michael J. C. |last10=Maslin |first10=Mark |last11=Ellis |first11=Erle C. |date=2021-11-15 |title=A practical solution: the Anthropocene is a geological event, not a formal epoch |journal=Episodes |volume=45 |issue=4 |pages=349–357 |language=en |doi=10.18814/epiiugs/2021/021029 |s2cid=244165877 |issn=0705-3797|doi-access=free }}{{Cite journal |last1=Head |first1=Martin J. |last2=Steffen |first2=Will |last3=Fagerlind |first3=David |last4=Waters |first4=Colin N. |last5=Poirier |first5=Clement |last6=Syvitski |first6=Jaia |last7=Zalasiewicz |first7=Jan A. |last8=Barnosky |first8=Anthony D. |last9=Cearreta |first9=Alejandro |last10=Jeandel |first10=Catherine |last11=Leinfelder |first11=Reinhold |date=2021-11-15 |title=The Great Acceleration is real and provides a quantitative basis for the proposed Anthropocene Series/Epoch |journal=Episodes |volume=45 |issue=4 |pages=359–376 |language=en |doi=10.18814/epiiugs/2021/021031 |s2cid=244145710 |issn=0705-3797|doi-access=free }}{{Cite journal |last1=Zalasiewicz |first1=Jan |last2=Waters |first2=Colin N. |last3=Ellis |first3=Erle C. |last4=Head |first4=Martin J. |last5=Vidas |first5=Davor |last6=Steffen |first6=Will |last7=Thomas |first7=Julia Adeney |last8=Horn |first8=Eva |last9=Summerhayes |first9=Colin P. |last10=Leinfelder |first10=Reinhold |last11=McNeill |first11=J. R. |date=2021 |title=The Anthropocene: Comparing Its Meaning in Geology (Chronostratigraphy) with Conceptual Approaches Arising in Other Disciplines |journal=Earth's Future |language=en |volume=9 |issue=3 |doi=10.1029/2020EF001896 |bibcode=2021EaFut...901896Z |s2cid=233816527 |issn=2328-4277|doi-access=free }}{{Cite journal |last1=Bauer |first1=Andrew M. |last2=Edgeworth |first2=Matthew |last3=Edwards |first3=Lucy E. |last4=Ellis |first4=Erle C. |last5=Gibbard |first5=Philip |last6=Merritts |first6=Dorothy J. |date=2021-09-16 |title=Anthropocene: event or epoch? |url=https://www.nature.com/articles/d41586-021-02448-z |journal=Nature |language=en |volume=597 |issue=7876 |pages=332 |doi=10.1038/d41586-021-02448-z |pmid=34522014 |bibcode=2021Natur.597..332B |s2cid=237515330 |issn=0028-0836}}

An international working group of the ICS on pre-Cryogenian chronostratigraphic subdivision have 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. This work assessed the geologic history of the currently defined eons and eras of the pre-Cambrian,{{Efn|name=Precam|group=note}} and the proposals in the "Geological Time Scale" books 2004,{{Citation |last=Bleeker |first=W. |title=Toward a "natural" Precambrian time scale |date=2005-03-17 |url=https://www.cambridge.org/core/product/identifier/CBO9780511536045A067/type/book_part |work=A Geologic Time Scale 2004 |pages=141–146 |editor-last=Gradstein |editor-first=Felix M. |edition=1 |publisher=Cambridge University Press |doi=10.1017/cbo9780511536045.011 |isbn=978-0-521-78673-7 |access-date=2022-04-09 |editor2-last=Ogg |editor2-first=James G. |editor3-last=Smith |editor3-first=Alan G.}} 2012, and 2020.{{Citation |last1=Strachan |first1=R. |title=Precambrian (4.56–1 Ga) |date=2020 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780128243602000164 |work=Geologic Time Scale 2020 |pages=481–493 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-824360-2.00016-4 |isbn=978-0-12-824360-2 |access-date=2022-04-09 |last2=Murphy |first2=J.B. |last3=Darling |first3=J. |last4=Storey |first4=C. |last5=Shields |first5=G.|s2cid=229513433 }} Their recommend revisions of the pre-Cryogenian geologic time scale were (changes from the current scale [v2023/09] are italicised):

• Three divisions of the Archean instead of four by dropping Eoarchean, and revisions to their geochronometric definition, along with the repositioning of the Siderian into the latest Neoarchean, and a potential Kratian division in the Neoarchean.
• Archean (4000–2450 Ma)
• Paleoarchean (4000–3500 Ma)
• Mesoarchean (3500–3000 Ma)
• Neoarchean (3000–2450 Ma)
• Kratian (no fixed time given, prior to the Siderian) – from Greek κράτος (krátos) 'strength'.
• Siderian (?–2450 Ma) – moved from Proterozoic to end of Archean, no start time given, base of Paleoproterozoic defines the end of the Siderian
• Refinement of geochronometric divisions of the Proterozoic, Paleoproterozoic, repositioning of the Statherian into the Mesoproterozoic, new Skourian period/system in the Paleoproterozoic, new Kleisian or Syndian period/system in the Neoproterozoic.
• Paleoproterozoic (2450–1800 Ma)
• Skourian (2450–2300 Ma) – from Greek σκουριά (skouriá) 'rust'.
• Rhyacian (2300–2050 Ma)
• Orosirian (2050–1800 Ma)
• Mesoproterozoic (1800–1000 Ma)
• Statherian (1800–1600 Ma)
• Calymmian (1600–1400 Ma)
• Ectasian (1400–1200 Ma)
• Stenian (1200–1000 Ma)
• Neoproterozoic (1000–538.8 Ma){{Efn|Geochronometric date for the Ediacaran has been adjusted to reflect ICC v2023/09 as the formal definition for the base of the Cambrian has not changed.|name=EdiacaranDate|group=note}}
• Kleisian or Syndian (1000–800 Ma) – respectively from Greek κλείσιμο (kleísimo) 'closure' and σύνδεση (sýndesi) 'connection'.
• Tonian (800–720 Ma)
• Cryogenian (720–635 Ma)
• Ediacaran (635–538.8 Ma)

Proposed pre-Cambrian timeline (Shield et al. 2021, ICS working group on pre-Cryogenian chronostratigraphy), shown to scale:{{Efn|Kratian time span is not given in the article. It lies within the Neoarchean, and prior to the Siderian. The position shown here is an arbitrary division.|name=kratian|group=note}}

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

ICC pre-Cambrian timeline (v2024/12, current {{As of|2025|01|lc=y}}), shown to scale:

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

The book, Geologic Time Scale 2012, was the last commercial publication of an international chronostratigraphic chart that was closely associated with the ICS. 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.{{cite book |last=Van Kranendonk |first=Martin J. |chapter=A Chronostratigraphic Division of the Precambrian |title=The geologic time scale 2012 |date=2012 |publisher=Elsevier |isbn=978-0-44-459425-9 |editor=Felix M. Gradstein |edition=1st |location=Amsterdam |pages=359–365 |doi=10.1016/B978-0-444-59425-9.00016-0 |editor2=James G. Ogg |editor3=Mark D. Schmitz |editor4=abi M. Ogg}} {{As of|2022|April}} these proposed changes have not been accepted by the ICS. The proposed changes (changes from the current scale [v2023/09]) are italicised:

• Hadean Eon (4567–4030 Ma)
• Chaotian Era/Erathem (4567–4404 Ma) – the name alluding both to the mythological Chaos and the chaotic phase of planet formation.{{cite journal |last1=Goldblatt |first1=C. |last2=Zahnle |first2=K. J. |last3=Sleep |first3=N. H. |last4=Nisbet |first4=E. G. |date=2010 |title=The Eons of Chaos and Hades |journal=Solid Earth |volume=1 |issue=1 |pages=1–3 |bibcode=2010SolE....1....1G |doi=10.5194/se-1-1-2010 |doi-access=free}}{{cite journal |last=Chambers |first=John E. |date=July 2004 |title=Planetary accretion in the inner Solar System |url=http://www.astro.washington.edu/courses/astro321/Chambers_EPSL_04.pdf |archive-url=https://web.archive.org/web/20120419024812/http://www.astro.washington.edu/courses/astro321/Chambers_EPSL_04.pdf |archive-date=2012-04-19 |url-status=live |journal=Earth and Planetary Science Letters |volume=223 |issue=3–4 |pages=241–252 |bibcode=2004E&PSL.223..241C |doi=10.1016/j.epsl.2004.04.031}}
• 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.
• 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.
• Isuan Period/System (3810–3490 Ma) – named after the Isua Greenstone Belt.
• 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.
• 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.
• Neoarchean Era/Erathem (2780–2420 Ma)
• Methanian Period/System (2780–2630 Ma) – named for the inferred predominance of methanotrophic prokaryotes
• Siderian Period/System (2630–2420 Ma) – named for the voluminous banded iron formations formed within its duration.
• Proterozoic Eon/Eonothem (2420–538.8 Ma){{efn|name=EdiacaranDate|group=note}}
• Paleoproterozoic Era/Erathem (2420–1780 Ma)
• Oxygenian Period/System (2420–2250 Ma) – named for displaying the first evidence for a global oxidising atmosphere.
• 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){{cite journal |last1=El Albani |first1=Abderrazak |last2=Bengtson |first2=Stefan |last3=Canfield |first3=Donald E. |last4=Riboulleau |first4=Armelle |last5=Rollion Bard |first5=Claire |last6=Macchiarelli |first6=Roberto |display-authors=etal |year=2014 |title=The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity |journal=PLOS ONE |volume=9 |issue=6 |pages=e99438 |bibcode=2014PLoSO...999438E |doi=10.1371/journal.pone.0099438 |pmc=4070892 |pmid=24963687 |doi-access=free}}{{cite journal |last1=El Albani |first1=Abderrazak |last2=Bengtson |first2=Stefan |last3=Canfield |first3=Donald E. |last4=Bekker |first4=Andrey |last5=Macchiarelli |first5=Roberto |last6=Mazurier |first6=Arnaud |last7=Hammarlund |first7=Emma U. |display-authors=etal |year=2010 |title=Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago |url=http://www.afrikibouge.com/publications/Article%20Albani.pdf |archive-url=https://web.archive.org/web/20240616162702/https://www.afrikibouge.com/publications/Article%20Albani.pdf |url-status=dead |archive-date=16 June 2024 |journal=Nature |volume=466 |issue=7302 |pages=100–104 |bibcode=2010Natur.466..100A |doi=10.1038/nature09166 |pmid=20596019 |s2cid=4331375}} first fossil appearance of eukaryotes.
• Columbian Period/System (2060–1780 Ma) – named after the supercontinent Columbia.
• Mesoproterozoic Era/Erathem (1780–850 Ma)
• Rodinian Period/System (1780–850 Ma) – named after the supercontinent Rodinia, stable environment.

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

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

ICC pre-Cambrian timeline (v2024/12, current {{As of|2025|01|lc=y}}), shown to scale:

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

{{More citations needed section|date=November 2023}}

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

While some regional terms are still in use, 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.{{cite web |title=International Commission on Stratigraphy |url=https://stratigraphy.org/ |accessdate=5 June 2022 |work=International Geological Time Scale}} The International Commission on Stratigraphy also provide an online interactive version of this chart. The interactive version is based on a service delivering a machine-readable Resource Description Framework/Web Ontology Language representation of the time scale, which is available through the Commission for the Management and Application of Geoscience Information GeoSciML project as a service{{cite web |title=Geologic Timescale Elements in the International Chronostratigraphic Chart |url=http://resource.geosciml.org/classifier/ics/ischart/ |access-date=2014-08-03}} and at a SPARQL end-point.{{cite web |last=Cox |first=Simon J. D. |title=SPARQL endpoint for CGI timescale service |url=http://resource.geosciml.org/sparql/isc2014 |url-status=dead |archive-url=https://archive.today/20140806164132/http://resource.geosciml.org/sparql/isc2014 |archive-date=2014-08-06 |access-date=2014-08-03}}{{cite journal |last1=Cox |first1=Simon J. D. |last2=Richard |first2=Stephen M. |year=2014 |title=A geologic timescale ontology and service |journal=Earth Science Informatics |volume=8 |pages=5–19 |doi=10.1007/s12145-014-0170-6 |s2cid=42345393}}

{{sticky header}}

{{Main|Lunar geologic timescale|Martian geologic timescale|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.{{efn|Not enough is known about extra-solar planets for worthwhile speculation.|group=note}}

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.{{Cite book |last=Wilhelms |first=Don E. |title=The geologic history of the Moon |series=Professional Paper |publisher=United States Geological Survey |year=1987 |doi=10.3133/pp1348}} The Moon is unique in the Solar System in that it is the only other body from which humans have rock samples with a known geological context.

{{Timeline Lunar Geological Timescale}}

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).{{Cite journal |last=Tanaka |first=Kenneth L. |date=1986 |title=The stratigraphy of Mars |url=http://doi.wiley.com/10.1029/JB091iB13p0E139 |journal=Journal of Geophysical Research |language=en |volume=91 |issue=B13 |pages=E139 |doi=10.1029/JB091iB13p0E139 |bibcode=1986JGR....91E.139T |issn=0148-0227}}{{Cite journal |last1=Carr |first1=Michael H. |last2=Head |first2=James W. |date=2010-06-01 |title=Geologic history of Mars |url=https://www.sciencedirect.com/science/article/pii/S0012821X09003847 |journal=Earth and Planetary Science Letters |series=Mars Express after 6 Years in Orbit: Mars Geology from Three-Dimensional Mapping by the High Resolution Stereo Camera (HRSC) Experiment |language=en |volume=294 |issue=3 |pages=185–203 |doi=10.1016/j.epsl.2009.06.042 |bibcode=2010E&PSL.294..185C |issn=0012-821X}}

{{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).{{Cite journal |last1=Bibring |first1=Jean-Pierre |last2=Langevin |first2=Yves |last3=Mustard |first3=John F. |last4=Poulet |first4=François |last5=Arvidson |first5=Raymond |last6=Gendrin |first6=Aline |last7=Gondet |first7=Brigitte |last8=Mangold |first8=Nicolas |last9=Pinet |first9=P. |last10=Forget |first10=F. |last11=Berthé |first11=Michel |date=2006-04-21 |title=Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data |url=https://www.science.org/doi/10.1126/science.1122659 |journal=Science |language=en |volume=312 |issue=5772 |pages=400–404 |doi=10.1126/science.1122659 |pmid=16627738 |bibcode=2006Sci...312..400B |s2cid=13968348 |issn=0036-8075}}

ImageSize = width:800 height:50

PlotArea = left:15 right:15 bottom:20 top:5

AlignBars = early

Period = from:-4500 till:0

TimeAxis = orientation:horizontal

ScaleMajor = unit:year increment:500 start:-4500

ScaleMinor = unit:year increment:100 start:-4500

Colors =

id:sidericol value:rgb(1,0.4,0.3)

id:theiicol value:rgb(1,0.2,0.5)

id:phyllocol value:rgb(0.7,0.4,1)

PlotData=

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

text:Siderikan from:-3500 till:0 color:sidericol

text:Theiikian from:-4000 till:-3500 color:theiicol

text:Phyllocian from:start till:-4000 color:phyllocol

{{Portal|Geology}}

{{div col|colwidth=25em}}

• Age of the Earth
• Cosmic calendar
• Deep time
• Evolutionary history of life
• Formation and evolution of the Solar System
• Geological history of Earth
• Geology of Mars
• Geon (geology)
• History of Earth
• History of geology
• History of paleontology
• List of fossil sites
• List of geochronologic names
• Lunar geologic timescale
• Martian geologic timescale
• Natural history
• New Zealand geologic time scale
• Prehistoric life
• Timeline of the Big Bang
• Timeline of evolution
• Timeline of the geologic history of the United States
• Timeline of human evolution
• Timeline of natural history
• Timeline of paleontology

{{div col end}}

{{Notelist|group=note}}

{{reflist|25em}}

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• {{cite news|url=https://www.npr.org/sections/13.7/2014/09/21/350344129/pondering-deep-time-could-inspire-new-ways-to-view-climate-change |last=Ialenti|first=Vincent|title=Pondering 'Deep Time' Could Inspire New Ways To View Climate Change.|newspaper=NPR|date=21 September 2014|publisher=NPR Cosmos & Culture}}
• {{cite journal |date=30 July 2004 |author1-link=Andrew H. Knoll|last1=Knoll|first1=Andrew H.|last2=Walter|first2=Malcolm R.|last3=Narbonne|first3=Guy M.|last4=Christie-Blick|first4=Nicholas |title=A New Period for the Geologic Time Scale |journal=Science |volume=305 |issue=5684 |pages=621–622 |url=http://www.ldeo.columbia.edu/~ncb/Selected_Articles_all_files/17_Science%20305.621.pdf |archive-url=https://web.archive.org/web/20111215034718/http://www.ldeo.columbia.edu/%7Encb/Selected_Articles_all_files/17_Science%20305.621.pdf |archive-date=2011-12-15 |url-status=live |doi=10.1126/science.1098803 |access-date=18 November 2011 |pmid=15286353|s2cid=32763298}}
• {{cite book |date=2010 |last=Levin|first=Harold L. |chapter=Time and Geology |chapter-url=https://books.google.com/books?id=D0yl7Cqsu78C&pg=PA29|title=The Earth Through Time |url=https://books.google.com/books?id=D0yl7Cqsu78C |place=Hoboken, New Jersey |publisher=John Wiley & Sons |isbn=978-0-470-38774-0 |access-date=18 November 2011}}
• {{cite book |last=Montenari |first=Michael |url=https://books.google.com/books?id=xzJQDAAAQBAJ |title=Stratigraphy and Timescales |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |date=2016 |isbn=978-0-12-811549-7}}
• {{cite book |last=Montenari |first=Michael |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/2/suppl/C |title=Advances in Sequence Stratigraphy |date=2017 |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-813077-3}}
• {{cite book |last=Montenari |first=Michael |date=2018 |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/3/suppl/C |title=Cyclostratigraphy and Astrochronology |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-815098-6}}
• {{cite book |last=Montenari |first=Michael |date=2019 |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/4/suppl/C |title=Case Studies in Isotope Stratigraphy |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-817552-1}}
• {{cite book |last=Montenari |first=Michael |date=2020 |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/5/suppl/C |title=Carbon Isotope Stratigraphy |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-820991-2}}
• {{cite book |last=Montenari |first=Michael |date=2021 |url=https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/6/suppl/C |title=Calcareous Nannofossil Biostratigraphy |edition=1st |location=Amsterdam |publisher=Academic Press (Elsevier) |isbn=978-0-12-824624-5}}
• Montenari, Michael (2022). [https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/7/suppl/C Integrated Quaternary Stratigraphy] (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-323-98913-8.
• Montenari, Michael (2023). [https://www.sciencedirect.com/bookseries/stratigraphy-and-timescales/vol/8/suppl/C Stratigraphy of Geo- and Biodynamic Processes] (1st ed.). Amsterdam: Academic Press (Elsevier). ISBN 978-0-323-99242-8.
• Nichols, Gary (2013). [https://books.google.com/books?id=Gcgp5oLFrZMC Sedimentology and Stratigraphy] (2nd ed.). Hoboken: Wiley-Blackwell. {{ISBN|978-1-4051-3592-4}}
• Williams, Aiden (2019). [https://books.google.com/books?id=etVhxQEACAAJ Sedimentology and Stratigraphy] (1st ed.). Forest Hills, NY: Callisto Reference. {{ISBN|978-1-64116-075-9}}

{{Commons category|Geologic time scale}}

{{Wikibooks|Historical Geology|Geological column}}

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

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