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Geologic timescale

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A timeline of Geologic periods.

(not shown to scale)

Years Ago^3,6	Epoch	Period/Age^4,5		Era	Eon	Major Events
Present day	Holocene	Quaternary		Cenozoic	Phanerozoic
10,000	Pleistocene	Quaternary				Extinction of many large mammals. Evolution of fully modern humans
1.6 million	Pliocene	Tertiary	Neogene
5 million	Miocene		Neogene
23 million	Oligocene		Paleogene
38 million	Eocene
55 million	Paleocene
64.3 million^*		Cretaceous		Mesozoic		Dinosaurs reach peak, become extinct. Primitive placental mammals
146 million		Jurassic				Marsupial mammals, first birds, first flowering plants[?]
208 million		Triassic				First dinosaurs, Egg-laying mammals
251.1 million^*		Permian		Paleozoic		Permian extinction event- 95% of life on Earth becomes extinct
286 million		Carboniferous¹	Pennsylvanian			Abundant insects, first reptiles, coal forests
325 million		Carboniferous¹	Mississippian			Large primitive trees
360 million		Devonian				First amphibians, clubmosses and horsetails appear, progymnosperms[?] (first seed bearing plants) appear
408.5 million^*		Silurian				First land plant fossils
443.5 million^*		Ordovician				Invertebrates dominant
490 million^*		Cambrian				Major diversification of life in the Cambrian explosion
545 million^*		Neoproterozoic²		Proterozoic	Precambrian	First multi-celled animals
900 million		Mesoproterozoic[?]
1,600 million		Paleoproterozoic				First Complex single-celled life
2,500 million		Archaean				Simple single-celled life
3,800 million		Hadean				Formation of Earth

1) In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods

2) Discoveries in the past quarter century have substantially changed the view of geologic and paleontologic events immediately prior to the Cambrian. The nomenclature has not stabilized. The term Neoproterozoic is used here, but other writers might equally well have used one or more of the terms 'Ediacarian', 'Vendian', 'Varangian', 'Precambrian', 'Protocambrian', 'Eocambrian', or might have extended the Cambrian further back in time. All of these terms are usually treated as a subset of the Proterozoic rather than a period between the Paleozoic and the Proterozoic.

3) Dates are slightly uncertain with differences of a few percent between various sources being common. This is largely due to uncertainties in radiometric dating and the problem that deposits suitable for radiometric dating seldom occur exactly at the places in the geologic column where we would most like to have them. Dates with an * are radiometrically determined based on internationally agreed to GSSPs. All dates given are for the end of the epoch in question.

4) Paleontologists often refer to faunal stages rather than geologic Periods. The Stage Nomenclature is quite complex. See http://flatpebble.nceas.ucsb.edu/public/harland for an excellent time ordered list of faunal stages. Also see the article on GSSPs.

5) In common usage the Tertiary-Quaternary and Paleogene-Neogene-Quaternary Periods are treated as equivalents to the Mesozoic and Paleozoic Periods. The term 'Period|Age' (e.g. 'Neogene Period|Age') is sometimes used instead of 'Period'.

6) The time shown in the "Years Ago" column is that of the end of the Epoch in the "Epoch" column.