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The Geologic Time Scale


NOTE: Ages and names used here are based on U.S. Geological Survey Fact Sheet 2007-3015, "Divisions of Geologic Time -- Major Chronostratigraphic and Geochronologic Units", March 2007, ages have been rounded, see publication for precise timeframe.
Eon Erathem or Era System,Subsystem or Period,Subperiod Series or Epoch
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Cenozoic
65.5 million years ago to Present

"Age of Recent Life"

An era of geologic time from the beginning of the Tertiary period to the present. Its name is from Greek and means "new life."

The Cenozoic, Mesozoic, and Paleozoic Eras are part of the Phanerozoic Eon


Quaternary
1.8 million years ago to the Present

The second period of the Cenozoic era. It contains two epochs: the Pleistocene and the Holocene. It is named after the Latin word "quatern" (four at a time).

The several geologic eras were originally named Primary, Secondary, Tertiary, and Quaternary. The first two names are no longer used. Tertiary and Quaternary have been retained but used as period designations.


Holocene
11,477 years ago (+/- 85 years) to the Present

An epoch of the Quaternary period. It is named after the Greek words "holos" (entire) and "ceno" (new).


Pleistocene
1.8 million to approximately 11,477 (+/- 85 years) years ago

"The Great Ice Age"

An epoch of the Quaternary period. It is named after the Greek words "pleistos" (most) and "ceno" (new).


Tertiary
65.5 to 1.8 million years ago

The first period of the Cenozoic era (after the Mesozoic era and before the Quaternary period).


Pliocene
5.3 to 1.8 million years ago

Final epoch of the Tertiary period. It is named after the Greek words "pleion" (more) and "ceno" (new).

Miocene
23.0 to 5.3 million years ago

A epoch of the upper Tertiary period. It is named after the Greek words "meion" (less) and "ceno" (new).


Oligocene
33.9 to 23.0 million years ago

An epoch of the early Tertiary period. It is named after the Greek words "oligos" (little, few) and "ceno" (new).


Eocene
55.8 to 33.9 million years ago

An epoch of the lower Tertiary period. Its name is from the Greek words "eos" (dawn) and "ceno" (new).


Paleocene
65.5 to 58.8 million years ago

Earliest epoch of the Tertiary period. It is named after the Greek words "palaois" (old) and "ceno" (new).



Eon Erathem or Era System,Subsystem or Period,Subperiod Series or Epoch
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Mesozoic
251.0 to 65.5 million years ago

"Age of Medieval Life"

An era of geologic time between the Paleozoic and the Cenozoic. The word Mesozoic is from Greek and means "middle life."

The Cenozoic, Mesozoic, and Paleozoic Eras are part of the Phanerozoic Eon


Cretaceous
145.5 to 65.5 million years ago

"The Age of Dinosaurs"

The final period of the Mesozoic era. The name is derived from the Latin word for chalk ("creta") and was first applied to extensive deposits of this age that form white cliffs along the English Channel between Great Britain and France.


Late or Upper
Early or Lower
Jurassic
199.6 to 145.5 million years ago

The middle period of the Mesozoic era. It is named after the Jura Mountains between France and Switzerland, where rocks of this age were first studied.


Late or Upper
Middle
Early or Lower
Triassic
251.0 to 199.6 million years ago

The earliest period of the Mesozoic era. The name Triassic refers to the threefold division of rocks of this age in Germany.

The Break-up of the continent Pangea ... MORE


Late or Upper
Middle
Early or Lower

Eon Erathem or Era System,Subsystem or Period,Subperiod Series or Epoch
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Paleozoic
542.0 to 251.0 million years ago

"Age of Ancient Life"

An era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic. The word Paleozoic is from Greek and means "old life."


Development of the Eastern Piedmont ... Taconic Orogeny ... MORE

The Cenozoic, Mesozoic, and Paleozoic Eras are part of the Phanerozoic Eon


Permian
299.0 to 251.0 million years ago

The final period of the Paleozoic era. It is named after the province of Perm, Russia, where rocks of this age were first studied.

NOTE: all series/epochs of the Silurian and the Permian have been named. Although the usage of these names is preferred, "lower/early", "middle", and "upper/late" are still acceptable as informal units (lowercase) for these two systems/periods.


Lopingian
Guadalupian
Cisuralian
Carboniferous
359.2 to 299.0 million years ago

A period of time in the Paleozoic era that includes the Pennsylvanian and Mississippian periods.
Pennsylvanian
318.1 to 299.0 million years ago

"The Coal Age"

A period of the Paleozoic era. It is named after the state of Pennsylvania where rocks of this age are widespread.


Late or Upper
Middle
Early or Lower
Mississippian
359.2 to 318.1 million years ago

A period of the Paleozoic era. It is named after the Mississippi River valley, which contains good exposures of rocks of this age.

Late or Upper
Middle
Early or Lower
Devonian
416.0 to 359.2 million years ago

A period of the Paleozoic era. It is named after Devonshire, England, where rocks of this age were first studied.

Late or Upper
Middle
Early or Lower
Silurian
443.7 to 416.0 million years ago

A period of the Paleozoic. It is named after a Celtic tribe called the Silures.

NOTE: all series/epochs of the Silurian and the Permian have been named. Although the usage of these names is preferred, "lower/early", "middle", and "upper/late" are still acceptable as informal units (lowercase) for these two systems/periods.


Pridoli
Ludlow
Wenlock
Llandovery
Ordovician
488.3 to 443.7 million years ago

The second earliest period of the Paleozoic era. It is named after a Celtic tribe called the Ordovices.

Late or Upper
Middle
Early or Lower
Cambrian
542.0 to 488.3 million years ago

The earliest period of the Paleozoic era. It is named after Cambria, the Roman name for Wales, where rocks of this age were first studied.

Late or Upper
Middle
Early or Lower

Precambrian ***
approximately 4 billion years ago to 542.0 million years ago

*** The name "Precambrian" means "before Cambrian". According to the Divisions of Geologic Time -- Major Chronostratigraphic and Geochronologic Units (USGS Fact Sheet 2007-3015, March 2007), for many years the term "Precambrian" was used for the division of time older than the Phanerozoic Eon (which includes the Cenozoic, Mesozoic, and Paleozoic Eras, see above). Today however the term is considered to be informal and without specific stratigraphic rank. The "Precambrian" covers the Proterozoic, Archean, and Hadean Eons.


Resources:
Table compiled and/or modified by: Lyn Topinka, USGS/CVO, 1997, 2000, 2001, 2006, 2008, with names and ages modified in 2008 to match U.S. Geological Survey Fact Sheet 2007-3015, "Divisions of Geologic Time -- Major Chronostratigraphic and Geochronologic Units", March 2007.
  1. U.S. Geological Survey Fact Sheet 2007-3015: U.S. Geological Survey Geologic Names Committee, 2007, Divisions of geologic timeóMajor chronostratigraphic and geochronologic units: U.S. Geological Survey Fact Sheet 2007-3015, 2 p.
  2. Geological Society of America (GSA) 1999 Geologic Timescale, GSA Website, 2006
  3. U.S. Geological Survey, Paleontology Website: http://geology.er.usgs.gov/paleo/, 1997 and January 2001
  4. Newman, Geologic Time Online Edition: USGS General Interest Publication, version 1.2
  5. Newhall and Dzurisin, 1988, Historical Unrest at Large Calderas in the World: USGS Bulletin 1855
  6. Schlee, Our Changing Earth: USGS General Interest Publication, Online Version, January 2001
  7. Swanson, et.al., 1989, Cenozoic vulcanism in the Cascade Range and Columbia Plateau, Southern Washington and Northermost Oregon, AGU Field Trip Guidebook T106
  8. University of California Museum of Paleontology Website, 2008.
  9. U.S. Army Corps of Engineers, Portland District, and the U.S. Department of the Interior, U.S. Geological Survey, The Geologic History of the Columbia River Gorge: Information Broshure
  10. The Geologic Story of the Ocoee River: USGS General Interest Publication, July 1996
  11. U.S. National Park Service Website - Geology Fieldnotes; Rocky Mountain National Park, Colorado, April 2000


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11/17/08, Lyn Topinka