Geologic Time


Eon

Era

Dates (m.y.)

Phanerozoic

Cenozoic

66-0

Mesozoic

251-66

Paleozoic

542-251

Proterozoic

Neoproterozoic

1000-542

Mesoproterozoic

1600-1000

Paleoproterozoic

2500-1600

Archean

Neoarchean

2800-2500

Mesoarchean

3200-2800

Paleoarchean

3600-3200

Eoarchean

4000-3600

(c) 2009 Andrew Alden, licensed to About.com, Inc. (fair use policy). Data from Geologic Time Scale of 2009)

All of geologic time, from the Earth's origin about 4600 million years ago to today, is divided into three eons. The first two eons, Archean and Proterozoic, and their seven eras are together informally referred to as Precambrian time. The informal term "Hadean" refers to time before 4 billion years ago (Ga). See summaries of the Archean Eon and the Proterozoic Eon.

The eras of the Proterozoic and Phanerozoic eons are each further divided into periods, shown in this geologic time scale.

The periods of the three Phanerozoic eras are divided in turn into epochs. (See the Phanerozoic epochs listed together.) Epochs are subdivided into ages. Because there are so many ages, they are presented separately for the Paleozoic Era, the Mesozoic Era and the Cenozoic Era.

The dates shown on this table were specified by the International Commission on Stratigraphy in 2009. Colors are used to indicate the age of rocks on geologic maps. There are two major color standards, the international standard and the U.S. Geological Survey standard. (All of the geologic time scales here are made using the 2009 standard of the Committee on the Geologic Map of the World.)

 

Geologic Time Scale: Precambrian Time

Eon

Era

Period

Dates (m.y.)

Phanerozoic (post-Precambrian time)

542-0

Proterozoic

Neoproterozoic

Ediacaran

635-542

Cryogenian

850-635

Tonian

1000-850

Mesoproterozoic

Stenian

1200-1000

Ectasian

1400-1200

Calymmian

1600-1400

Paleoproterozoic

Statherian

1800-1600

Orosirian

2050-1800

Rhyacian

2300-2050

Siderian

2500-2300

Archean

Neoarchean

 

2800-2500

Mesoarchean

 

3200-2800

Paleoarchean

 

3600-3200

Eoarchean

 

4000-3600

(c) 2009 Andrew Alden, licensed to About.com, Inc. (fair use policy. Data from Geologic Time Scale of 2009.

"Precambrian" is a long-established, informal name for the 4 billion years of Earth history before hard-bodied organisms arose at the beginning of the Cambrian Period, earliest division of the Phanerozoic Eon. Aside from the names of the eons and the Ediacaran Period (also called the Vendian), few of the terms in this geologic time scale are yet in wide use. The time before 4000 million years ago (4 billion or 4 Ga) is informally known as Hadean time.

Whereas later geologic history is minutely documented by fossils showing the evolving succession of living things, Precambrian time is almost entirely divided by absolute numerical ages of rocks. Nonetheless, the end of the Archean marks a distinct change in the Earth, roughly at the time atmospheric oxygen first appeared. (Read more about the Archean Eon and the Proterozoic Eon.) Archean and Proterozoic rocks are exposed in the continents' ancient central regions, but they make up a small fraction of Earth's total surface. The dates shown on this geologic time scale were specified by the International Commission on Stratigraphy in 2009. The colors were specified by the Committe on the Geologic Map of the World in 2009.

Geologic Time Scale: The Paleozoic Era

Period

Epoch

Age

Dates (m.y.)

Permian

Lopingian

Chianghsingian

253.8-251.0

Wuchiapingian

260.4-253.8

Guadalupian

Capitanian

265.8-260.4

Wordian

268.0-265.8

Roadian

270.6-268.0

Cisuralian

Kungurian

275.6-270.6

Artinskian

284.4-275.6

Sakmarian

294.6-284.4

Asselian

299.0-294.6

Pennsylvanian
(Carboniferous)

Late Pennsylvanian

Gzhelian

303.4-299.0

Kasimovian

307.2-303.4

Middle Pennsylvanian

Moscovian

311.7-307.2

Early Pennsylvanian

Bashkirian

318.1-311.7

Mississippian
(Carboniferous)

Late Mississippian

Serpukhovian

328.3-318.1

Middle Mississippian

Visean

345.3-328.3

Early Mississippian

Tourniaisian

359.2-345.3

Devonian

Late Devonian

Famennian

374.5-359.2

Frasnian

385.3-374.5

Middle Devonian

Givetian

391.8-385.3

Eifelian

397.5-391.8

Early Devonian

Emsian

407.0-397.5

Pragian

411.2-407.0

Lochkovian

416.0-411.2

Silurian

Pridoli

 

418.7-416.0

Ludlow

Ludfordian

421.3-418.7

Gorstian

422.9-421.3

Wenlock

Homerian

426.2-422.9

Sheinwoodian

428.2-426.2

Llandovery

Telychian

436.0-428.2

Aeronian

439.0-436.0

Rhuddanian

443.7-439.0

Ordovician

Late Ordovician

Hirnantian

445.6-443.7

Katian

455.8-445.6

Sandbian

460.9-455.8

Middle Ordovician

Darriwillian

468.1-460.9

Dapingian

471.8-468.1

Early Ordovician

Floian

478.6-471.8

Tremadocian

488.3-478.6

Cambrian

Furongian

Stage 10

492-488.3

Stage 9

496-492

Paibian

499-496

Series 3

Guzhangian

503-499

Drumian

506.5-503

Stage 5

510-506.5

Series 2

Stage 4

515-510

Stage 3

521-515

Terreneuvian

Stage 2

528-521

Fortunian

542-528

Period

Epoch

Age

Dates (m.y.)

(c) 2009 Andrew Alden, licensed to About.com, Inc. (fair use policy). Data from Geologic Time Scale of 2009.

Back to the top-level geologic time scale

This geologic time scale represents the working edge of historical geology, showing the latest names and dates of the smallest divisions of geologic time that are universally recognized. The Paleozoic Era is the first part of the Phanerozoic Eon. For anyone but specialists, the rounded-off dates in the Phanerozoic table are sufficient. Each of these dates also has a specified uncertainty, which you can look up at the source. For example, the Silurian and Devonian age boundaries have more than 2 million years uncertainty and the Cambrian units are still being refined, but the rest of the chronology is more securely known.

The dates shown on this geologic time scale were specified by the International Commission on Stratigraphy in 2009, and the colors were specified by the Committee for the Geologic Map of the World in 2009.

 

Geologic Time Scale: The Mesozoic Era

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Period

Epoch

Age

Dates (m.y.)

Cretaceous

Late Cretaceous

Maastrichtian

70.6-65.5

Campanian

83.5-70.6

Santonian

85.8-83.5

Coniacian

88.6-85.8

Turonian

93.6-88.6

Cenomanian

99.6-93.6

Early Cretaceous

Albian

112.0-99.6

Aptian

125.0-112.0

المصدر: شبكة المعلومات الدولية (http://geology.about.com/library/bl/time/blpreCtime.htm)
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