Geologic Time Scale

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ANTH 1-Physical Anthropology

Handout: Geochronology

Eon	Era	Period	Epoch
Phanerozoic	Cenozoic	Quaternary	Recent/Holocene Pleistocene
	Cenozoic	Tertiary	Pliocene Miocene Oligocene Eocene Paleocene
	Mesozoic	Cretaceous Jurassic Triassic
	Paleozoic	Permian Carboniferous Devonian Silurian Ordovician Cambrian
Precambrian	Proterozoic	Vendian
	Archaean
	Hadean

For a wide variety of reasons, mostly theoretical in nature, the dates provided below should be viewed as approximations. In reality, the divisions of time on the Geological Time Scale varies from researcher to researcher or from publication to publication. Thus, you may see other date ranges given in different texts or in other disciplines. This poses no major problems for this class so long as this concept is understood.

Precambrian Eon (4,500 to 543 mya)

Hadean (4500 to 3800 mya)-approximate time of origin of Earth
Archaean (3800 to 2500 mya)
Proterozoic (2500 to 543 mya)-Oxygen begins to accumulate in atmosphere-oldest fossils known (prokaryotes)-oldest Eukaryotic fossils-oldest animal fossils

Vendian Period (650 to 543 mya)-diverse invertebrate animals-first vertebrates-diverse alga

Phanerozoic Eon (543 mya to today)

Paleozoic Era (543 to 248 mya)

Cambrian Period (543 to 490 mya)-origin of first modern animal phyla

Ordovician Period (490 to 443 mya)-origin of plants-marine alga abundant
Silurian Period (443 to 417 mya)-diversity of jawless fishes-first jawed fishes-colonization of land by vascular plants and arthropods
Devonian Period (417 to 354 mya)-diversification of bony fishes-first amphibians-insects
Carboniferous Period(354 to 290 mya)-Extensive forests of vascular plants-first seed plants-origin of reptiles-amphibians dominant

*Mississippian (354 to 323 mya)
*Pennsylvanian (323 to 290 mya)

Permian Period (290 to 248 mya)-extinction of many marine and terrestrial organisms-radiation of reptiles-origin of mammal-like reptiles-most modern insects

Mesozoic Era (248 to 65 mya)

Triassic Period (248 to 206 mya)—cone-bearing plants (gymnosperms) dominate landscape-first dinosaurs-mammals and birds
Jurassic Period (206 to 144 mya)-gymnosperms continue as dominant plants-dinosaurs dominant
Cretaceous Period (144 to 65 mya)-flowering plants (angiosperms) appear-many groups of organisms, including most dinosaur lineages, become extinct

Cenozoic Era (65 mya to today)

Tertiary Period (65 to 1.8 mya)

Paleocene Epoch (65 to 54.8 mya)-major radiation of mammals, birds, pollinating insects
Eocene Epoch 54.8 to 33.7 mya)-angiosperm dominance increases-origins of most modern mammalian orders
Oligocene Epoch (33.7 to 23.8 mya)-origins of many primate groups, including The apes
Miocene Epoch (23.8 to 5.3 mya)-continued radiation of mammals and angiosperms
Pliocene Epoch (5.3 to 1.8 mya)-apelike ancestors of humans appear

Quaternary Period (1.8 mya to today)

Pleistocene Epoch (1.8 mya to 10,000 years ago)-ice ages-humans appear
Holocene/Recent Epoch (10,000 years ago to today)-historic time

Questions? Comments? Corrections?? email me!

V 3.2

Last Updated Summer 2006

April Garwin

2001-2006