Cambrian Period ( /ˈkæmbriən/ or /ˈkeɪmbriən/) was the first
geological period of the
Paleozoic Era, of the
Phanerozoic Eon. The
Cambrian lasted 55.6 million years from the end of the preceding
Ediacaran Period 541 million years ago (mya) to the beginning of the
Ordovician Period 485.4 mya. Its subdivisions, and its base, are
somewhat in flux. The period was established (as “Cambrian
series”) by Adam Sedgwick, who named it after Cambria, the
Latinised form of Cymru, the Welsh name for Wales, where Britain's
Cambrian rocks are best exposed. The
Cambrian is unique in
its unusually high proportion of lagerstätte sedimentary deposits,
sites of exceptional preservation where "soft" parts of organisms are
preserved as well as their more resistant shells. As a result, our
understanding of the
Cambrian biology surpasses that of some later
Cambrian marked a profound change in life on Earth; prior to the
Cambrian, the majority of living organisms on the whole were small,
unicellular and simple; the
Charnia being exceptional.
Complex, multicellular organisms gradually became more common in the
millions of years immediately preceding the Cambrian, but it was not
until this period that mineralized—hence readily
fossilized—organisms became common. The rapid diversification of
lifeforms in the Cambrian, known as the
Cambrian explosion, produced
the first representatives of all modern animal phyla. Phylogenetic
analysis has supported the view that during the
metazoa (animals) evolved monophyletically from a single common
ancestor: flagellated colonial protists similar to modern
Although diverse life forms prospered in the oceans, the land is
thought to have been comparatively barren—with nothing more complex
than a microbial soil crust and a few molluscs that emerged to
browse on the microbial biofilm known to have been present. Most
of the continents were probably dry and rocky due to a lack of
vegetation. Shallow seas flanked the margins of several continents
created during the breakup of the supercontinent Pannotia. The seas
were relatively warm, and polar ice was absent for much of the period.
1.2 Dating the Cambrian
5 Oceanic life
8 See also
10 Further reading
11 External links
Further information: Stratigraphy of the Cambrian
Despite the long recognition of its distinction from younger
Ordovician Period rocks and older
Precambrian Supereon rocks, it was
not until 1994 that this time period was internationally ratified. The
base of the
Cambrian lies atop a complex assemblage of trace fossils
known as the
Treptichnus pedum assemblage. The use of Treptichnus
pedum, a reference ichnofossil to mark the lower boundary of the
Cambrian, is difficult as the occurrence of very similar trace fossils
belonging to the Treptichnids group are found well below the T. pedum
in Namibia, Spain and Newfoundland, and possibly, in the western USA.
The stratigraphic range of T. pedum overlaps the range of the
Ediacaran fossils in Namibia, and probably in Spain.
Cambrian Period followed the
Ediacaran Period and was followed by
Ordovician Period. The
Cambrian is divided into four epochs
(series) and ten ages (stages). Currently only two series and five
stages are named and have a GSSP.
Because the international stratigraphic subdivision is not yet
complete, many local subdivisions are still widely used. In some of
these subdivisions the
Cambrian is divided into three epochs with
locally differing names – the Early
Cambrian (Caerfai or
Waucoban, 541 ± 1.0 to 509 ± 1.7 mya), Middle
Cambrian (St Davids or Albertan, 509 ± 1.0 to 497
± 1.7 mya) and
Furongian (497 ± 1.0 to 485.4
± 1.7 mya; also known as Late Cambrian, Merioneth or Croixan).
Rocks of these epochs are referred to as belonging to the Lower,
Middle, or Upper Cambrian.
Trilobite zones allow biostratigraphic correlation in the Cambrian.
Each of the local epochs is divided into several stages. The Cambrian
is divided into several regional faunal stages of which the
Russian-Kazakhian system is most used in international parlance:
Dolgellian (Trempealeauan, Fengshanian)
Ffestiniogian (Franconian, Changshanian)
Cambrian Series 3
Cambrian Series 2
*In Russian scientific thought the lower boundary of the
suggested to be defined at the base of the Tommotian Stage which is
characterized by diversification and global distribution of organisms
with mineral skeletons and the appearance of the first Archaeocyath
Dating the Cambrian
Archeocyathids from the
Poleta formation in the
Death Valley area
International Commission on Stratigraphy list the
as beginning at 541 million years ago and ending at
485.4 million years ago.
The lower boundary of the
Cambrian was originally held to represent
the first appearance of complex life, represented by trilobites. The
recognition of small shelly fossils before the first trilobites, and
Ediacara biota substantially earlier, led to calls for a more
precisely defined base to the
After decades of careful consideration, a continuous sedimentary
sequence at Fortune Head,
Newfoundland was settled upon as a formal
base of the
Cambrian period, which was to be correlated worldwide by
the earliest appearance of Treptichnus pedum. Discovery of this
fossil a few metres below the
GSSP led to the refinement of this
statement, and it is the T. pedum ichnofossil assemblage that is now
formally used to correlate the base of the Cambrian.
This formal designation allowed radiometric dates to be obtained from
samples across the globe that corresponded to the base of the
Cambrian. Early dates of 570 million years ago quickly gained
favour, though the methods used to obtain this number are now
considered to be unsuitable and inaccurate. A more precise date using
modern radiometric dating yield a date of
541 ± 0.3 million years ago. The ash horizon in
Oman from which this date was recovered corresponds to a marked fall
in the abundance of carbon-13 that correlates to equivalent excursions
elsewhere in the world, and to the disappearance of distinctive
Ediacaran fossils (Namacalathus, Cloudina). Nevertheless, there are
arguments that the dated horizon in Oman does not correspond to the
Cambrian boundary, but represents a facies change from
marine to evaporite-dominated strata — which would mean that dates
from other, more suitable sections, ranging from 544 or 542 Ma, are
Plate reconstructions suggest a global supercontinent, Pannotia, was
in the process of breaking up early in the period, with
Laurentia (North America), Baltica, and Siberia having separated from
the main supercontinent of
Gondwana to form isolated land masses.
Most continental land was clustered in the Southern Hemisphere at this
time, but was drifting north. Large, high-velocity rotational
Gondwana appears to have occurred in the Early
With a lack of sea ice – the great glaciers of the Marinoan
Snowball Earth were long melted – the sea level was high,
which led to large areas of the continents being flooded in warm,
shallow seas ideal for sea life. The sea levels fluctuated somewhat,
suggesting there were 'ice ages', associated with pulses of expansion
and contraction of a south polar ice cap.
Baltoscandia a Lower
Cambrian transgression transformed large
swathes of the
Sub-Cambrian peneplain into a epicontinental sea.
The Earth was generally cold during the early Cambrian, probably due
to the ancient continent of
Gondwana covering the
South Pole and
cutting off polar ocean currents. However, average temperatures were 7
degrees Celsius higher than today. There were likely polar ice caps
and a series of glaciations, as the planet was still recovering from
an earlier Snowball Earth. It became warmer towards the end of the
period; the glaciers receded and eventually disappeared, and sea
levels rose dramatically. This trend would continue into the
Although there were a variety of macroscopic marine
plants[which?] no land plant (embryophyte) fossils
are known from the Cambrian. However, biofilms and microbial mats were
well developed on
Cambrian tidal flats and beaches 500 mya., and
microbes forming microbial Earth ecosystems, comparable with modern
soil crust of desert regions, contributing to soil formation.
view • discuss • edit
Earliest Earth (−4540)
Earliest sexual reproduction
Axis scale: million years
Orange labels: ice ages.
Human timeline and Nature timeline
Most animal life during the
Cambrian was aquatic. Trilobites were once
assumed to be the dominant life form at that time, but this has
proven to be incorrect. Arthropods were by far the most dominant
animals in the ocean, but trilobites were only a minor part of the
total arthropod diversity. What made them so apparently abundant was
their heavy armor reinforced by calcium carbonate (CaCO3), which
fossilized far more easily than the fragile chitinous exoskeletons of
other arthropods, leaving numerous preserved remains.
The period marked a steep change in the diversity and composition of
Earth's biosphere. The
Ediacaran biota suffered a mass extinction at
the start of the
Cambrian Period, which corresponded to an increase in
the abundance and complexity of burrowing behaviour. This behaviour
had a profound and irreversible effect on the substrate which
transformed the seabed ecosystems. Before the Cambrian, the sea floor
was covered by microbial mats. By the end of the Cambrian, burrowing
animals had destroyed the mats in many areas through bioturbation, and
gradually turned the seabeds into what they are today.[clarification
needed] As a consequence, many of those organisms that were dependent
on the mats became extinct, while the other species adapted to the
changed environment that now offered new ecological niches. Around
the same time there was a seemingly rapid appearance of
representatives of all the mineralized phyla except the Bryozoa, which
appeared in the Lower Ordovician. However, many of those phyla
were represented only by stem-group forms; and since mineralized phyla
generally have a benthic origin, they may not be a good proxy for
(more abundant) non-mineralized phyla.
A reconstruction of
Margaretia dorus from the Burgess Shale, which
were once believed to be green algae, but are now understood to
While the early
Cambrian showed such diversification that it has been
Cambrian Explosion, this changed later in the period, when
there occurred a sharp drop in biodiversity. About 515 million years
ago, the number of species going extinct exceeded the number of new
species appearing. Five million years later, the number of genera had
dropped from an earlier peak of about 600 to just 450. Also, the
speciation rate in many groups was reduced to between a fifth and a
third of previous levels. 500 million years ago, oxygen levels fell
dramatically in the oceans, leading to hypoxia, while the level of
poisonous hydrogen sulfide simultaneously increased, causing another
extinction. The later half of
Cambrian was surprisingly barren and
show evidence of several rapid extinction events; the stromatolites
which had been replaced by reef building sponges known as
Archaeocyatha, returned once more as the archaeocyathids became
extinct. This declining trend did not change until the Great
Ordovician Biodiversification Event.
Cambrian organisms ventured onto land, producing the trace
Protichnites and Climactichnites. Fossil evidence suggests
that euthycarcinoids, an extinct group of arthropods, produced at
least some of the Protichnites. Fossils of the track-maker of
Climactichnites have not been found; however, fossil trackways and
resting traces suggest a large, slug-like mollusc.
In contrast to later periods, the
Cambrian fauna was somewhat
restricted; free-floating organisms were rare, with the majority
living on or close to the sea floor; and mineralizing animals were
rarer than in future periods, in part due to the unfavourable ocean
Many modes of preservation are unique to the Cambrian, and some
preserve soft body parts, resulting in an abundance of Lagerstätten.
The United States
Federal Geographic Data Committee
Federal Geographic Data Committee uses a "barred
capital C" ⟨Ꞓ⟩ character to represent the
Unicode character is U+A792 Ꞓ LATIN CAPITAL LETTER C WITH
Stromatolites of the Pika Formation (Middle Cambrian) near Helen Lake,
Banff National Park, Canada
Trilobites were very common during this time
Anomalocaris was an early marine predator, among the various
arthropods of the time.
Pikaia was an early chordate from the Middle Cambrian
Opabinia was a creature with an unusual body plan; it was probably
related to arthropods
Protichnites were the trackways of arthropods that walked Cambrian
Hallucigenia is maybe an early ancestor of the Velvet worms.
Reconstructions of H. sparsa, H. hongmeia, and H. fortis
Size comparison of different
Part of a series on
Small shelly fauna
Cambrian substrate revolution
Stem and crown groups
Ordovician extinction event – circa 488 mya
Dresbachian extinction event—circa 502 mya
End Botomian extinction event—circa 517 mya
List of fossil sites
List of fossil sites (with link directory)
Type locality (geology), the locality where a particular rock type,
stratigraphic unit, fossil or mineral species is first identified
Modes of preservation in the Cambrian
Bitter Springs type
Burgess Shale type
Trilobite Bed type
Small shelly fossils
Phanerozoic Carbon Dioxide.png
^ Image:All palaeotemps.png
^ Haq, B. U.; Schutter, SR (2008). "A Chronology of Paleozoic
Sea-Level Changes". Science. 322 (5898): 64–8.
^ a b Chisholm, Hugh, ed. (1911). "
Encyclopædia Britannica (11th ed.). Cambridge University Press.
^ "Stratigraphic Chart 2012" (PDF). International Stratigraphic
Commission. Archived from the original (PDF) on 20 April 2013.
Retrieved 9 November 2012.
^ Sedgwick and R. I. Murchison (1835) "On the
Silurian and Cambrian
systems, exhibiting the order in which the older sedimentary strata
succeed each other in England and Wales," Notices and Abstracts of
Communications to the British Association for the Advancement of
Science at the Dublin meeting, August 1835, pp. 59-61, in: Report of
the Fifth Meeting of the British Association for the Advancement of
Science; held in Dublin in 1835 (1836). From p. 60: "Professor
Sedgwick then described in descending order the groups of slate rocks,
as they are seen in
Wales and Cumberland. To the highest he gave the
name of Upper
Cambrian group. ... To the next inferior group he gave
the name of Middle Cambrian. ... The Lower
Cambrian group occupies the
S.W. coast of Cærnarvonshire,"
^ Sedgwick, A. (1852). "On the classification and nomenclature of the
Paleozoic rocks of England and Wales". Q. J. Geol. Soc. Lond. 8:
^ "Chambers 21st Century Dictionary".
Chambers Dictionary (Revised
ed.). New Dehli: Allied Publishers. 2008. p. 203.
^ Orr, P. J.; Benton, M. J.; Briggs, D. E. G. (2003). "Post-Cambrian
closure of the deep-water slope-basin taphonomic window". Geology. 31
(9): 769–772. Bibcode:2003Geo....31..769O. doi:10.1130/G19193.1.
^ Butterfield, N. J. (2007). "Macroevolution and macroecology through
deep time". Palaeontology. 50 (1): 41–55.
^ Schieber, 2007, pp. 53–71.
^ Seilacher, A.; Hagadorn, J.W. (2010). "Early Molluscan evolution:
evidence from the trace fossil record". Palaois. 25 (9): 565–575.
^ A. Knoll, M. Walter, G. Narbonne, and N. Christie-Blick (2004) "The
Ediacaran Period: A New Addition to the Geologic Time Scale."
Submitted on Behalf of the Terminal
Proterozoic Subcommission of the
International Commission on Stratigraphy.
^ M.A. Fedonkin, B.S. Sokolov, M.A. Semikhatov, N.M.Chumakov (2007).
"Vendian versus Ediacaran: priorities, contents, prospectives.
Archived 4 October 2011 at the Wayback Machine." In: edited by M. A.
Semikhatov "The Rise and Fall of the Vendian (Ediacaran) Biota. Origin
of the Modern Biosphere. Transactions of the International Conference
on the IGCP Project 493, August 20–31, 2007, Moscow." Moscow: GEOS.
^ A. Ragozina, D. Dorjnamjaa, A. Krayushkin, E. Serezhnikova (2008).
Treptichnus pedum and the Vendian-
Cambrian boundary". 33 Intern.
Geol. Congr. 6–14 August 2008, Oslo, Norway. Abstracts. Section HPF
07 Rise and fall of the
Ediacaran (Vendian) biota. P. 183.
^ A.Yu. Rozanov; V.V. Khomentovsky; Yu.Ya. Shabanov; G.A. Karlova;
A.I. Varlamov; V.A. Luchinina; T.V. Pegel’; Yu.E. Demidenko; P.Yu.
Parkhaev; I.V. Korovnikov; N.A. Skorlotova (2008). "To the problem of
stage subdivision of the Lower Cambrian". Stratigraphy and Geological
Correlation. 16 (1): 1–19. Bibcode:2008SGC....16....1R.
^ B. S. Sokolov; M. A. Fedonkin (1984). "The Vendian as the Terminal
System of the Precambrian" (PDF). Episodes. 7 (1): 12–20. Archived
from the original (PDF) on 25 March 2009.
^ V. V. Khomentovskii; G. A. Karlova (2005). "The Tommotian Stage Base
Cambrian Lower Boundary in Siberia". Stratigraphy and
Geological Correlation. 13 (1): 21–34.
^ a b c d e Geyer, Gerd; Landing, Ed (2016). "The
Phanerozoic and Ediacaran–
Cambrian boundaries: A
historical approach to a dilemma". Geological Society, London, Special
Publications. 448: SP448.10. doi:10.1144/SP448.10.
^ Landing, Ed; Geyer, Gerd; Brasier, Martin D.; Bowring, Samuel A.
Cambrian Evolutionary Radiation: Context, correlation, and
chronostratigraphy—Overcoming deficiencies of the first appearance
datum (FAD) concept". Earth-Science Reviews. 123: 133.
^ Gradstein, F.M.; Ogg, J.G.; Smith, A.G.; et al. (2004). A Geologic
Time Scale 2004. Cambridge University Press.
^ Powell, C.M.; Dalziel, I.W.D.; Li, Z.X.; McElhinny, M.W. (1995).
"Did Pannotia, the latest
Neoproterozoic southern supercontinent,
really exist". Eos, Transactions, American Geophysical Union. 76:
^ Scotese, C.R. (1998). "A tale of two supercontinents: the assembly
of Rodinia, its break-up, and the formation of
Pannotia during the
Pan-African event". Journal of African Earth Sciences. 27 (1A): 171.
^ a b Mckerrow, W. S.; Scotese, C. R.; Brasier, M. D. (1992). "Early
Cambrian continental reconstructions". Journal of the Geological
Society. 149 (4): 599–606. doi:10.1144/gsjgs.149.4.0599.
^ Mitchell, R. N.; Evans, D. A. D.; Kilian, T. M. (2010). "Rapid Early
Cambrian rotation of Gondwana". Geology. 38 (8): 755.
^ Smith, A.G. (2008). "
Neoproterozoic time scales and stratigraphy".
Geol. Soc. (
^ Brett, C. E.; Allison, P. A.; Desantis, M. K.; Liddell, W. D.;
Kramer, A. (2009). "Sequence stratigraphy, cyclic facies, and
lagerstätten in the
Middle Cambrian Wheeler and Marjum Formations,
Great Basin, Utah". Palaeogeography, Palaeoclimatology, Palaeoecology.
277: 9–33. doi:10.1016/j.palaeo.2009.02.010.
^ Nielsen, Arne Thorshøj; Schovsbo, Niels Hemmingsen (2011). "The
Cambrian of Scandinavia: Depositional environment, sequence
stratigraphy and palaeogeography". Earth-Science Reviews. 107 (3–4):
^ Schieber et al., 2007, pp. 53–71.
^ Retallack, G.J. (2008). "
Cambrian palaeosols and landscapes of South
Australia". Alcheringa. 55 (8): 1083–1106.
^ "Greening of the Earth pushed way back in time".
Cambrian HSU NHM".
^ "3 Evolving Respiratory Systems as a Cause of the
- Out of Thin Air: Dinosaurs, Birds, and Earth's Ancient Atmosphere -
The National Academies Press". doi:10.17226/11630.
^ Perkins, Sid (23 September 2013). "As the worms churn".
^ Taylor, P.D.; Berning, B.; Wilson, M.A. (2013). "Reinterpretation of
Cambrian 'bryozoan' Pywackia as an octocoral". Journal of
Paleontology. 87 (6): 984–990. doi:10.1666/13-029.
^ Budd, G. E.; Jensen, S. (2000). "A critical reappraisal of the
fossil record of the bilaterian phyla". Biological Reviews of the
Cambridge Philosophical Society. 75 (2): 253–95.
doi:10.1111/j.1469-185X.1999.tb00046.x. PMID 10881389.
^ Nanglu, Karma; Caron, Jean-Bernard; Conway Morris, Simon; Cameron,
Christopher B. (2016). "
Cambrian suspension-feeding tubicolous
hemichordates". BMC Biology. 14. doi:10.1186/s12915-016-0271-4.
^ The Ordovician: Life's second big bang
^ Marshall, Michael. "
Oxygen crash led to
^ Collette & Hagadorn, 2010.
^ Collette, Gass & Hagadorn, 2012
^ Yochelson & Fedonkin, 1993.
^ Getty & Hagadorn, 2008.
^ a b Munnecke, A.; Calner, M.; Harper, D. A. T.; Servais, T. (2010).
Silurian sea-water chemistry, sea level, and climate:
A synopsis". Palaeogeography, Palaeoclimatology, Palaeoecology. 296
(3–4): 389–413. doi:10.1016/j.palaeo.2010.08.001.
^ Federal Geographic Data Committee, ed. (August 2006). FGDC Digital
Cartographic Standard for Geologic Map Symbolization FGDC-STD-013-2006
(PDF). U.S. Geological Survey for the Federal Geographic Data
Committee. p. A–32–1. Retrieved 23 August 2010.
^ Priest, Lorna A.; Iancu, Laurentiu; Everson, Michael (October 2010).
"Proposal to Encode C WITH BAR" (PDF). Retrieved 6 April 2011.
Unicode Character 'LATIN CAPITAL LETTER C WITH BAR' (U+A792).
fileformat.info. Accessed 15 Jun 2015
Wikisource has original works on the topic: Paleozoic#Cambrian
Amthor, J. E.; Grotzinger, John P.; Schröder, Stefan; Bowring, Samuel
A.; Ramezani, Jahandar; Martin, Mark W.; Matter, Albert (2003).
Namacalathus at the Precambrian-Cambrian
boundary in Oman". Geology. 31 (5): 431–434.
Collette, J. H.; Gass, K. C.; Hagadorn, J. W. (2012). "Protichnites
eremita unshelled? Experimental model-based neoichnology and new
evidence for a euthycarcinoid affinity for this ichnospecies". Journal
of Paleontology. 86 (3): 442–454. doi:10.1666/11-056.1.
Collette, J. H.; Hagadorn, J. W. (2010). "Three-dimensionally
preserved arthropods from
Cambrian Lagerstatten of Quebec and
Wisconsin". Journal of Paleontology. 84 (4): 646–667.
Getty, P. R.; Hagadorn, J. W. (2008). "Reinterpretation of
Climactichnites Logan 1860 to include subsurface burrows, and erection
of Musculopodus for resting traces of the trailmaker". Journal of
Paleontology. 82 (6): 1161–1172. doi:10.1666/08-004.1.
Gould, S. J.; Wonderful Life: the
Burgess Shale and the Nature of Life
(New York: Norton, 1989)
Ogg, J.; June 2004, Overview of Global Boundary Stratotype Sections
and Points (GSSPs)
Accessed 30 April 2006.
Owen, R. (1852). "Description of the impressions and footprints of the
Protichnites from the Potsdam sandstone of Canada". Geological Society
of London Quarterly Journal. 8: 214–225.
Peng, S.; Babcock, L.E.; Cooper, R.A. (2012). "The
The Geologic Time Scale (PDF).
Schieber, J.; Bose, P. K.; Eriksson, P. G.; Banerjee, S.; Sarkar, S.;
Altermann, W.; Catuneau, O. (2007). Atlas of Microbial Mat Features
Preserved within the Clastic Rock Record. Elsevier.
Yochelson, E. L.; Fedonkin, M. A. (1993). "Paleobiology of
Climactichnites, and Enigmatic Late
Cambrian Fossil" (Free full text).
Smithsonian Contributions to Paleobiology. 74 (74): 1–74.
Wikimedia Commons has media related to Cambrian.
Cambrian period on In Our Time at the BBC.
Biostratigraphy – includes information on
Dr. Sam Gon's trilobite pages (contains numerous
Report on the web on Amthor and others from Geology vol. 31
Life on the Mats
Geologic history of Earth
Quaternary (present–2.588 Mya)
Holocene (present–11.784 kya)
Pleistocene (11.784 kya–2.588 Mya)
Neogene (2.588–23.03 Mya)
Pliocene (2.588–5.333 Mya)
Miocene (5.333–23.03 Mya)
Paleogene (23.03–66.0 Mya)
Oligocene (23.03–33.9 Mya)
Eocene (33.9–56.0 Mya)
Paleocene (56.0–66.0 Mya)
Cretaceous (66.0–145.0 Mya)
Late (66.0–100.5 Mya)
Early (100.5–145.0 Mya)
Jurassic (145.0–201.3 Mya)
Late (145.0–163.5 Mya)
Middle (163.5–174.1 Mya)
Early (174.1–201.3 Mya)
Triassic (201.3–251.902 Mya)
Late (201.3–237 Mya)
Middle (237–247.2 Mya)
Early (247.2–251.902 Mya)
Permian (251.902–298.9 Mya)
Lopingian (251.902–259.8 Mya)
Guadalupian (259.8–272.3 Mya)
Cisuralian (272.3–298.9 Mya)
Carboniferous (298.9–358.9 Mya)
Pennsylvanian (298.9–323.2 Mya)
Mississippian (323.2–358.9 Mya)
Devonian (358.9–419.2 Mya)
Late (358.9–382.7 Mya)
Middle (382.7–393.3 Mya)
Early (393.3–419.2 Mya)
Silurian (419.2–443.8 Mya)
Pridoli (419.2–423.0 Mya)
Ludlow (423.0–427.4 Mya)
Wenlock (427.4–433.4 Mya)
Llandovery (433.4–443.8 Mya)
Ordovician (443.8–485.4 Mya)
Late (443.8–458.4 Mya)
Middle (458.4–470.0 Mya)
Early (470.0–485.4 Mya)
Cambrian (485.4–541.0 Mya)
Furongian (485.4–497 Mya)
Series 3 (497–509 Mya)
Series 2 (509–521 Mya)
Terreneuvian (521–541.0 Mya)
(541.0 Mya–2.5 Gya)
Neoproterozoic era (541.0 Mya–1 Gya)
Ediacaran (541.0-~635 Mya)
Cryogenian (~635-~720 Mya)
Tonian (~720 Mya-1 Gya)
Mesoproterozoic era (1–1.6 Gya)
Stenian (1-1.2 Gya)
Ectasian (1.2-1.4 Gya)
Calymmian (1.4-1.6 Gya)
Paleoproterozoic era (1.6–2.5 Gya)
Statherian (1.6-1.8 Gya)
Orosirian (1.8-2.05 Gya)
Rhyacian (2.05-2.3 Gya)
Siderian (2.3-2.5 Gya)
Archean eon² (2.5–4 Gya)
Neoarchean (2.5–2.8 Gya)
Mesoarchean (2.8–3.2 Gya)
Paleoarchean (3.2–3.6 Gya)
Eoarchean (3.6–4 Gya)
Hadean eon² (4–4.6 Gya)
kya = thousands years ago. Mya = millions years ago.
Gya = billions
years ago.¹ =
Phanerozoic eon. ² =
Source: (2017/02). International Commission on Stratigraphy. Retrieved
13 July 2015. Divisions of Geologic Time—Major Chronostratigraphic
and Geochronologic Units USGS Retrieved 10 March 2013.