Table of geologic time

Eon Era Period1 Series/
Major Events End, Million
Years Ago2
Phanerozoic Cenozoic Neogene3 Holocene End of recent glaciation and rise of modern civilization Ongoing
Pleistocene Flourishing and then extinction of many large mammals (Pleistocene megafauna); Evolution of fully modern humans 0.011430 ± 0.00013
Pliocene Intensification of present ice age. Cool and dry climate; Australopithecines appear, many of the existing genera of mammals, and recent molluscs appear 1.806 ± 0.005 *
Miocene Moderate climate; Mountain building in northern hemisphere; Modern mammal and bird families became recognizable. Horses and mastodonts diverse. Grasses become ubiquitous. First hominoids appear. 5.332 ± 0.005 *
Paleogene3 Oligocene Warm climate; Rapid evolution and diversification of fauna, especially mammals. Major evolution and dispersal of modern types of angiosperms 23.03 ± 0.05 *
Eocene Archaic mammals (e.g. Creodonts, Condylarths, Uintatheres, etc) flourish and continue to develop during the epoch. Appearance of several "modern" mammal families. Primitive whales diversify. First grasses. Reglaciation of Antarctica; start of current ice age. 33.9 ± 0.1 *
Paleocene Climate tropical. Modern plants; Mammals diversify into a number of primitive lineages following the extinction of the dinosaurs. First large mammals (up to bear or small hippo size) 55.8 ± 0.2 *
Mesozoic Cretaceous Upper/Late Flowering plants appear, along with new types of insects. More modern teleost fish begin to appear. Ammonites, belemnites, rudists, echinoids and sponges all common. Many new types of dinosaurs (e.g. Tyrannosaurs, Titanosaurs, duck bills, and horned dinosaurs) evolve on land, as do modern crocodilians; and mosasaurs and modern sharks appear in the sea. Primitive birds gradually replace pterosaurs. Monotremes, marsupials and placental mammals appear. Break up of Gondwana. 65.5 ± 0.3 *
Lower/Early 99.6 ± 0.9 *
Jurassic Upper/Late Gymnosperms (especially conifers, Bennettitales and cycads) and ferns common. Many types of dinosaurs, such as sauropods, carnosaurs, and stegosaurs. Mammals common but small. First birds and lizards. Ichthyosaurs and plesiosaurs diverse. Bivalves, Ammonites and belemnites abundant. Echinoids very common, also crinoids, starfish, sponges, and terebratulid and rhynchonellid brachiopods. Breakup of Pangea into Gondwana and Laurasia. 145.5 ± 4.0
Middle 161.2 ± 4.0
Lower/Early 175.6 ± 2.0 *
Triassic Upper/Late Archosaurs dominant and diverse on land, include many large forms; cynodonts become smaller and more mammal-like. First dinosaurs, mammals, pterosaurs, and crocodilia. Dicrodium flora common on land. Many large aquatic temnospondyl amphibians. Ichthyosaurs and nothosaurs common in the seas. Ceratite ammonoids extremely common. Modern corals and teleost fish appear. 199.6 ± 0.6
Middle 228.0 ± 2.0
Lower/Early 245.0 ± 1.5
Paleozoic Permian Lopingian Landmass unites in the supercontinent of Pangea. Synapsid reptiles become common (Pelycosaurs and Therapsids), parareptiles and temnospondyl amphibians also remain common. Carboniferous flora replaced by gymnosperms in the middle of the period. Beetles and flies evolve. Marine life flourishes in the warm shallow reefs. Productid and spriferid brachiopods, bivalves, foraminifera, and ammonoids all abundant. End of Permo-carboniferous ice age. At the end of the period the Permian extinction event- 95% of life on Earth becomes extinct 251.0 ± 0.4 *
Guadalupian 260.4 ± 0.7 *
Cisuralian 270.6 ± 0.7 *
Upper/Late Winged insects appear and are abundant, some growing to large size. Amphibians common and diverse. First reptiles, coal forests (Lepidodendron, Sigillaria, Calamites, Cordaites, etc), very high atmospheric oxygen content. In the seas, Goniatites, brachiopods, bryozoa, bivalves, corals, etc all common. 299.0 ± 0.8 *
Middle 306.5 ± 1.0
Lower/Early 311.7 ± 1.1
Upper/Late Large primitive trees, first land vertebrates, brackish water and amphibious eurypterids; rhizodonts dominant fresh-water predators. In the seas primitive sharks common and very diverse, echinoderms (especially crinoids and blastoids) abundant, Corals, bryozoa, and and brachiopods (Productida, Spriferida, etc) very common; Goniatites common, trilobites and nautiloids in decline. Glaciation in East Gondwana. 318.1 ± 1.3 *
Middle 326.4 ± 1.6
Lower/Early 345.3 ± 2.1
Devonian Upper/Late First clubmosses and horsetails appear, progymnosperms (first seed bearing plants) appear, first trees (Archaeopteris). In the sea strophomenid and atrypid brachiopods, rugose and tabulate corals, and crinoids are abundant. Goniatite ammonoids are common, and coleoids appear. Trilobites reduced in numbers. Ostracoderms decline; Jawed fish (Placoderms, lobe-finned and ray-finned fish, and early sharks) important life in the sea. First amphibians (but still aquatic). "Old Red Continent" (Euramerica) 359.2 ± 2.5 *
Middle 385.3 ± 2.6 *
Lower/Early 397.5 ± 2.7 *
Silurian Pridoli First vascular land plants, millipedes and arthropleurids, first jawed fish, as well as many types of armoured jawless forms. sea-scorpions reach large size. tabulate and rugose corals, brachiopods (Pentamerida, Rhynchonellida, etc), and crinoids all abundant; trilobites and molluscs diverse. Graptolites not as varied. 416.0 ± 2.8 *
Ludlow 418.7 ± 2.7 *
Wenlock 422.9 ± 2.5 *
Llandovery 428.2 ± 2.3 *
Ordovician Upper/Late Invertebrates very diverse and include many new types. Early corals, Brachiopods (Orthida, Strophomenida, etc), bivalves, nautiloids, trilobites, ostracods, bryozoa, many types of echinoderms (cystoids, crinoids, starfish, etc), branched graptolites, and other taxa all common. Conodonts were primitive planktonic vertebrates that appear at the start of the Ordovician. Ice age at the end of the period. First very primitive land plants. 443.7 ± 1.5 *
Middle 460.9 ± 1.6 *
Lower/Early 471.8 ± 1.6
Cambrian Furongian Major diversification of life in the Cambrian Explosion; more than half of modern animal phyla appear, along with a number of extinct and problematic forms. Archeocyatha abundant in the early Cambrian. Trilobites, Priapulida, sponges, inarticulate brachiopods, and many other forms all common. First vertebrates appear. anomalocarids are top predators. Edicarian animals rare, then die out. 488.3 ± 1.7 *
Middle 501.0 ± 2.0 *
Lower/Early 513.0 ± 2.0
Proterozoic5 Neo-
Ediacaran First multi-celled animals. Edicarian fauna (vendobionta flourish worldwide. Simple trace fossils from worm-like animals. First sponges. 542.0 ± 1.0 *
Cryogenian Possible snowball Earth period, Rodinia begins to break up 630 +5/-30 *
Tonian First acritarch radiation 850 6
Stenian Formation of Rodinia 1000 6
Ectasian 1200 6
Calymmian 1400 6
Statherian First complex single-celled life 1600 6
Orosirian Transition to oxygen atmosphere 1800 6
Rhyacian 2050 6
Siderian 2300 6
Archaean5 Neoarchean Stabilization of most modern cratons, possible mantle overturn event 2500 6
Mesoarchean First stromatolites 2800 6
Paleoarchean First known oxygen producing bacteria 3200 6
Eoarchean Simple single-celled life 3600 6
Hadean5,7 4100 MYA - Oldest known rock;
4400 MYA - Oldest known mineral;
4570 MYA - Formation of Earth
  1. Paleontologists often refer to faunal stages rather than geologic Periods. The stage nomenclature is quite complex. See Harland for an excellent time ordered list of faunal stages.
  2. 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 they would be most useful. The dates and errors quoted above are according to the International Commission on Stratigraphy 2004 time scale. Dates labeled with a * indicate boundaries where a Global Boundary Stratotype Section and Point has been internationally agreed upon.
  3. Historically, the Cenozoic has been divided up into the Quaternary and Tertiary sub-eras, as well as the Neogene and Paleogene periods. However, the International Commission on Stratigraphy has recently decided to stop endorsing the terms Quaternary and Tertiary as part of the formal nomenclature.
  4. In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods.
  5. The Proterozoic, Archean and Hadean are often collectively referred to as Precambrian Time, and sometimes also as the Cryptozoic.
  6. Defined by absolute age (Global Standard Stratigraphic Age).
  7. Though commonly used, the Hadean is not a formal eon and no lower bound for the Eoarchean has been agreed upon. The Hadean has also sometimes been called the Priscoan.

Original Source: Wikipedia. All text is available under the terms of the GNU Free Documentation License.

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This page contains a single entry by Andrea Bottaro published on July 10, 2005 3:31 PM.

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