Andrea Bottaro posted Entry 1323 on July 10, 2005 03:31 PM.
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|Major Events||End, Million
|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|
|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|
|Statherian||First complex single-celled life||1600 6|
|Orosirian||Transition to oxygen atmosphere||1800 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
- 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.
- 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.
- 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.
- In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods.
- The Proterozoic, Archean and Hadean are often collectively referred to as Precambrian Time, and sometimes also as the Cryptozoic.
- Defined by absolute age (Global Standard Stratigraphic Age).
- 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.
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