Geologic time scale

From Wikipedia, the free encyclopedia

It has been suggested that Period (geology) be merged into this article or section. (Discuss)

Diagram of geological time scale.

The geological time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of Earth. The table of geologic periods presented here agrees with the dates and nomenclature proposed by the International Commission on Stratigraphy, and uses the standard color codes of the United States Geological Survey.

Evidence from radiometric dating indicates that the Earth is about 4.570 billion years old. The geological or deep time of Earth's past has been organized into various units according to events which took place in each period. Different spans of time on the time scale are usually delimited by major geological or paleontological events, such as mass extinctions. For example, the boundary between the Cretaceous period and the Paleogene period is defined by the extinction event, known as the Cretaceous–Tertiary extinction event, that marked the demise of the dinosaurs and of many marine species. Older periods which predate the reliable fossil record are defined by absolute age.

1 Graphical timelines
2 Terminology
3 History of the time scale
4 Table of geologic time
5 References and footnotes
6 See also
7 External links

[edit] Graphical timelines

The second and third timelines are each subsections of their preceding timeline as indicated by asterisks.

Millions of Years

The Holocene (the latest epoch) is too small to be shown clearly on this timeline.

[edit] Terminology

The largest defined unit of time is the supereon composed of Eons. Eons are divided into Eras, which are in turn divided into Periods, Epochs and Stages. At the same time paleontologists define a system of faunal stages, of varying lengths, based on changes in the observed fossil assemblages. In many cases, such faunal stages have been adopted in building the geological nomenclature, though in general there are far more recognized faunal stages than defined geological time units.

Geologists tend to talk in terms of Upper/Late, Lower/Early and Middle parts of periods and other units , such as "Upper Jurassic", and "Middle Cambrian". Upper, Middle, and Lower are terms applied to the rocks themselves, as in "Upper Jurassic sandstone," while Late, Middle, and Early are applied to time, as in "Early Jurassic deposition" or "fossils of Early Jurassic age." The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic." Because geologic units occurring at the same time but from different parts of the world can often look different and contain different fossils, there are many examples where the same period was historically given different names in different locales. For example, in North America the Lower Cambrian is referred to as the Waucoban series that is then subdivided into zones based on trilobites. The same timespan is split into Tommotian, Atdabanian and Botomian stages in East Asia and Siberia. A key aspect of the work of the International Commission on Stratigraphy is to reconcile this conflicting terminology and define universal horizons that can be used around the world.

[edit] History of the time scale

Main article: history of geology

Main article: history of paleontology

This article needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2007)

Earth history mapped to 24 hours

The principles underlying geologic (geological) time scales were laid down by Nicholas Steno in the late 17th century. Steno argued that rock layers (or strata) are laid down in succession, and that each represents a "slice" of time. He also formulated the principle of superposition, which states that any given stratum is probably older than those above it and younger than those below it. While Steno's principles were simple, applying them to real rocks proved complex. Over the course of the 18th century geologists realized that:

Sequences of strata were often eroded, distorted, tilted, or even inverted after deposition;
Strata laid down at the same time in different areas could have entirely different appearances;
The strata of any given area represented only part of the Earth's long history.

A comparative geological timescale

The first serious attempts to formulate a geological time scale that could be applied anywhere on Earth took place in the late 18th century. The most influential of those early attempts (championed by Abraham Werner, among others) divided the rocks of the Earth's crust into four types: Primary, Secondary, Tertiary, and Quaternary. Each type of rock, according to the theory, formed during a specific period in Earth history. It was thus possible to speak of a "Tertiary Period" as well as of "Tertiary Rocks." Indeed, "Tertiary" (now Paleocene-Pliocene) and "Quaternary" (now Pleistocene-Holocene) remained in use as names of geological periods well into the 20th century.

In opposition to the then-popular Neptunist theories expounded by Werner (that all rocks had precipitated out of a single enormous flood), a major shift in thinking came with the reading by James Hutton of his Theory of the Earth; or, an Investigation of the Laws Observable in the Composition, Dissolution, and Restoration of Land Upon the Globe before the Royal Society of Edinburgh in March and April 1785, events which "as things appear from the perspective of the twentieth century, James Hutton in those reading became the founder of modern geology"^[1] What Hutton proposed was that the interior of the Earth was hot, and that this heat was the engine which drove the creation of new rock: land was eroded by air and water and deposited as layers in the sea; heat then consolidated the sediment into stone, and uplifted it into new lands. This theory was dubbed "Plutonist" in contrast to the flood-oriented theory.

The identification of strata by the fossils they contained, pioneered by William Smith, Georges Cuvier, Jean d'Omalius d'Halloy and Alexandre Brogniart in the early 19th century, enabled geologists to divide Earth history more precisely. It also enabled them to correlate strata across national (or even continental) boundaries. If two strata (however distant in space or different in composition) contained the same fossils, chances were good that they had been laid down at the same time. Detailed studies between 1820 and 1850 of the strata and fossils of Europe produced the sequence of geological periods still used today.

The process was dominated by British geologists, and the names of the periods reflect that dominance. The "Cambrian," (the Roman name for Wales) and the "Ordovician," and "Silurian", named after ancient Welsh tribes, were periods defined using stratigraphic sequences from Wales.^[2] The "Devonian" was named for the English county of Devon, and the name "Carboniferous" was simply an adaptation of "the Coal Measures," the old British geologists' term for the same set of strata. The "Permian" was named after Perm, Russia, because it was defined using strata in that region by a Scottish geologist Roderick Murchison. However, some periods were defined by geologists from other countries. The "Triassic" was named in 1834 by a German geologist Friedrich Von Alberti from the three distinct layers (Latin trias meaning triad) —red beds, capped by chalk, followed by black shales— that are found throughout Germany and Northwest Europe, called the 'Trias'. The "Jurassic" was named by a French geologist Alexandre Brogniart for the extensive marine limestone exposures of the Jura Mountains. The "Cretaceous" (from Latin creta meaning 'chalk') as a separate period was first defined by a Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris basin^[3] and named for the extensive beds of chalk (calcium carbonate deposited by the shells of marine invertebrates).

British geologists were also responsible for the grouping of periods into Eras and the subdivision of the Tertiary and Quaternary periods into epochs.

When William Smith and Sir Charles Lyell first recognized that rock strata represented successive time periods, time scales could be estimated only very imprecisely since various kinds of rates of change used in estimation were highly variable. While creationists had been proposing dates of around six or seven thousand years for the age of the Earth based on the Bible, early geologists were suggesting millions of years for geologic periods with some even suggesting a virtually infinite age for the Earth. Geologists and paleontologists constructed the geologic table based on the relative positions of different strata and fossils, and estimated the time scales based on studying rates of various kinds of weathering, erosion, sedimentation, and lithification. Until the discovery of radioactivity in 1896 and the development of its geological applications through radiometric dating during the first half of the 20th century (pioneered by such geologists as Arthur Holmes) which allowed for more precise absolute dating of rocks, the ages of various rock strata and the age of the Earth were the subject of considerable debate.

In 1977, the Global Commission on Stratigraphy (now the International Commission on Stratigraphy) started an effort to define global references (Global Boundary Stratotype Sections and Points) for geologic periods and faunal stages. The commission's most recent work is described in the 2004 geologic time scale of Gradstein et al.^[4]. A UML model for how the timescale is structured, relating it to the GSSP, is also available^[5].

[edit] Table of geologic time

The following table summarizes the major events and characteristics of the periods of time making up the geologic time scale. As above, this time scale is based on the International Commission on Stratigraphy. (See lunar geologic timescale for a discussion of the geologic subdivisions of Earth's moon.) The height of each table entry does not correspond to the duration of each subdivision of time.

v • d • e

Geologic time scale

Supereon	Eon	Era	Period^[6]	Series / Epoch	Faunal stage^[7] / Geologic age	Major events	Start, million years ago^[7]
	Phanerozoic	Cenozoic^[8]	Neogene^[8]	Holocene	Quaternary	The last glacial period ends and rise of human civilization. Quaternary Ice Age recedes, and the current interglacial begins. Younger Dryas cold spell occurs, Sahara Desert forms from savannah, and agriculture begins, allowing humans to build cities. Paleolithic/Neolithic (Stone Age) cultures begin around 10,000 BC, giving way to Copper Age (3500 BC) and Bronze Age (2500 BC). Cultures continue to grow in complexity and technical advancement through the Iron Age (1200 BC), giving rise to many pre-historic cultures throughout the world, eventually leading into Classical Antiquity, such as Ancient Rome and even to the Middle Ages and present day. Also refer to the List of archaeological periods for clarification on early cultures and ages. Mount Tambora erupts in 1815, causing the Year Without a Summer (1816) in Europe and North America from a volcanic winter. atmospheric CO₂ levels start creeping from 100 ppmv at the end of the last glaciation to the current level of 385 parts per million volume (ppmv), causing global warming and climate change, possibly from anthropogenic sources, such as the Industrial Revolution^[9]	0.011430 ± 0.00013^[8]^[10]
				Pleistocene	Late/Tyrrhenian Stage	Flourishing and then extinction of many large mammals (Pleistocene megafauna). Evolution of anatomically modern humans. Quaternary Ice Age continues with glaciations and interstadials (and the accompanying fluctuations from 100 to 300 ppmv in atmospheric Carbon Dioxide levels^[9]), further intensification of Icehouse Earth conditions, roughly 1.6 MYA^[11]. Last glacial maximum (30,000 years ago), last glacial period (18,000-15,000 years ago). Dawn of human stone-age cultures, with increasing technical complexity than previous ice age cultures, such as engravings and clay statues (Venus of Lespugue), particularly in the Mediterranean and Europe. Lake Toba supervolcano erupts 75,000 years before present, causing a volcanic winter and pushes humanity to the brink of extinction.	0.126 ± 0.005^*
					Middle		0.500?
					Early		1.806 ± 0.005^*
					Gelasian		2.588 ± 0.005^*
				Pliocene	Piacenzian/Blancan	Intensification of present Icehouse conditions, Present (Quaternary) ice age begins roughly 2.58 MYA; cool and dry climate. Australopithecines, many of the existing genera of mammals, and recent mollusks appear. Homo habilis appears.	3.600 ± 0.005^*
				Pliocene	Zanclean		5.332 ± 0.005^*
				Miocene	Messinian	Moderate Icehouse climate, puncuated by ice ages; Orogeny in northern hemisphere. Modern mammal and bird families became recognizable. Horses and mastodons diverse. Grasses become ubiquitous. First apes appear (for reference see the article: "Sahelanthropus tchadensis"). Kaikoura Orogeny forms Southern Alps in New Zealand, continues today. Orogeny of the Alps in Europe slows, but continues to this day. Carpathean orogeny forms Carpathian Mountains in Central and Eastern Europe. Hellenic orogeny in Greece and Aegean Sea slows, but continues to this day. Middle Miocene Disruption occurs. Widespread forests slowly draw in massive amounts of atmospheric Carbon Dioxide, gradually lowering the level atmospheric CO₂ from 650 ppmv down to around 100 ppmv^[9].	7.246 ± 0.05^*
					Tortonian		11.608 ± 0.05^*
					Burdigalian		13.65 ± 0.05^*
					Serravallian		15.97 ± 0.05^*
					Langhian		20.43 ± 0.05^*
					Aquitanian		23.03 ± 0.05^*
			Paleogene^[8]	Oligocene	Chattian	Warm but cooling climate, moving towards Icehouse; Rapid evolution and diversification of fauna, especially mammals. Major evolution and dispersal of modern types of flowering plants	28.4 ± 0.1^*
				Oligocene	Rupelian		33.9 ± 0.1^*
				Eocene	Priabonian	Moderate, cooling climate. 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 and formation of its ice cap; Azolla event triggers ice age, and the Icehouse Earth climate that would follow it to this day, from the settlement and decay of seafloor algae drawing in massive amounts of atmospheric Carbon Dioxide^[9], lowering it from 3800 ppmv down to 650 ppmv. End of Laramide and Sevier Orogenies of the Rocky Mountains in North America. Orogeny of the Alps in Europe begins. Hellenic Orogeny begins in Greece and Aegean Sea.	37.2 ± 0.1^*
					Bartonian		40.4 ± 0.2^*
					Lutetian		48.6 ± 0.2^*
					Ypresian		55.8 ± 0.2^*
				Paleocene	Thanetian	Climate tropical. Modern plants appear; Mammals diversify into a number of primitive lineages following the extinction of the dinosaurs. First large mammals (up to bear or small hippo size). Alpine orogeny in Europe and Asia begins. Indian Subcontinent collides with Asia 55 MYA^[11], Himalayan Orogeny starts between 52 and 48 MYA.	58.7 ± 0.2^*
					Selandian		61.7 ± 0.3^*
					Danian		65.5 ± 0.3^*
		Mesozoic	Cretaceous	Upper/Late	Maastrichtian	Flowering plants proliferate, along with new types of insects. More modern teleost fish begin to appear. Ammonites, belemnites, rudist bivalves, echinoids and sponges all common. Many new types of dinosaurs (e.g. Tyrannosaurs, Titanosaurs, duck bills, and horned dinosaurs) evolve on land, as do Eusuchia (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. Beginning of Laramide and Sevier Orogenies of the Rocky Mountains. Atmospheric Carbon Dioxide close to present-day levels.	70.6 ± 0.6^*
					Campanian		83.5 ± 0.7^*
					Santonian		85.8 ± 0.7^*
					Coniacian		89.3 ± 1.0^*
					Turonian		93.5 ± 0.8^*
					Cenomanian		99.6 ± 0.9^*
				Lower/Early	Albian		112.0 ± 1.0^*
					Aptian		125.0 ± 1.0^*
					Barremian		130.0 ± 1.5^*
					Hauterivian		136.4 ± 2.0^*
					Valanginian		140.2 ± 3.0^*
					Berriasian		145.5 ± 4.0^*
			Jurassic	Upper/Late	Tithonian	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. Sea urchins very common, along with crinoids, starfish, sponges, and terebratulid and rhynchonellid brachiopods. Breakup of Pangaea into Gondwana and Laurasia. Nevadan orogeny in North America. Rantigata and Cimmerian Orogenies taper off. Atmospheric Carbon Dioxide levels 4-5 times the present day levels (1200-1500 ppmv, compared to today's 385 ppmv^[9]).	150.8 ± 4.0^*
					Kimmeridgian		155.7 ± 4.0^*
					Oxfordian		161.2 ± 4.0^*
				Middle	Callovian		164.7 ± 4.0
					Bathonian		167.7 ± 3.5^*
					Bajocian		171.6 ± 3.0^*
					Aalenian		175.6 ± 2.0^*
				Lower/Early	Toarcian		183.0 ± 1.5^*
					Pliensbachian		189.6 ± 1.5^*
					Sinemurian		196.5 ± 1.0^*
					Hettangian		199.6 ± 0.6^*
			Triassic	Upper/Late	Rhaetian	Archosaurs dominant on land as dinosaurs, in the oceans as Ichthyosaurs and nothosaurs, and in the air as pterosaurs. cynodonts become smaller and more mammal-like, while first mammals and crocodilia appear. Dicrodium flora common on land. Many large aquatic temnospondyl amphibians. Ceratitic ammonoids extremely common. Modern corals and teleost fish appear, as do many modern insect clades. Andean Orogeny in South America. Cimmerian Orogeny in Asia. Rangitata Orogeny begins in New Zealand. Hunter-Bowen Orogeny in Northern Australia, Queensland and New South Wales ends, (c. 260-225 MYA)	203.6 ± 1.5^*
					Norian		216.5 ± 2.0^*
					Carnian		228.0 ± 2.0^*
				Middle	Ladinian		237.0 ± 2.0^*
				Middle	Anisian		245.0 ± 1.5^*
				Lower/Early ("Scythian")	Olenekian		249.7 ± 1.5^*
				Lower/Early ("Scythian")	Induan		251.0 ± 0.7^*
		Paleozoic	Permian	Lopingian	Changhsingian	Landmasses unite into supercontinent Pangaea, creating the Appalachians. End of Permo-Carboniferous glaciation. Synapsid reptiles (pelycosaurs and therapsids) become plentiful, while parareptiles and temnospondyl amphibians remain common. In the mid-Permian, coal-age flora are replaced by cone-bearing gymnosperms (the first true seed plants) and by the first true mosses. Beetles and flies evolve. Marine life flourishes in warm shallow reefs; productid and spiriferid brachiopods, bivalves, forams, and ammonoids all abundant. Permian-Triassic extinction event occurs 251 mya: 95% of life on Earth becomes extinct, including all trilobites, graptolites, and blastoids. Ouachita and Innuitian Orogenies in North America. Uralian Orogeny in Europe/Asia tapers off. Altaid orogeny in Asia. Hunter-Bowen Orogeny on Australian Continent begins, (c. 260-225 MYA). Forms the MacDonnell Ranges.	253.8 ± 0.7^*
				Lopingian	Wuchiapingian		260.4 ± 0.7^*
				Guadalupian	Capitanian		265.8 ± 0.7^*
					Wordian/Kazanian		268.4 ± 0.7^*
					Roadian/Ufimian		270.6 ± 0.7^*
				Cisuralian	Kungurian		275.6 ± 0.7^*
					Artinskian		284.4 ± 0.7^*
					Sakmarian		294.6 ± 0.8^*
					Asselian		299.0 ± 0.8^*
			Carbon- iferous^[12]/ Pennsyl- vanian	Upper/Late	Gzhelian	Winged insects radiate suddenly; some (esp. Protodonata and Palaeodictyoptera) are quite large. Amphibians common and diverse. First reptiles and coal forests (scale trees, ferns, club trees, giant horsetails, Cordaites, etc.). Highest-ever atmospheric oxygen levels. Goniatites, brachiopods, bryozoa, bivalves, and corals plentiful in the seas and oceans. Testate forams proliferate. Uralian Orogeny in Europe and Asia.	303.9 ± 0.9^*
				Upper/Late	Kasimovian		306.5 ± 1.0^*
				Middle	Moscovian		311.7 ± 1.1^*
Lower/Early	Bashkirian			318.1 ± 1.3^*
Carbon- iferous^[12]/ Missis- sippian	Upper/Late		Serpukhovian	Large primitive trees, first land vertebrates, and amphibious sea-scorpions live amid coal-forming coastal swamps. Lobe-finned rhizodonts are dominant big fresh-water predators. In the oceans, early sharks are common and quite diverse; echinoderms (especially crinoids and blastoids) abundant. Corals, bryozoa, goniatites and brachiopods (Productida, Spiriferida, etc.) very common. But trilobites and nautiloids decline. Glaciation in East Gondwana. Tuhua Orogeny in New Zealand tapers off.	326.4 ± 1.6^*
	Middle		Viséan		345.3 ± 2.1^*
	Lower/Early		Tournaisian		359.2 ± 2.5^*
Devonian	Upper/Late		Famennian	First clubmosses, horsetails and ferns appear, as do the first seed-bearing plants (progymnosperms), first trees (the progymnosperm Archaeopteris), and first (wingless) insects. Strophomenid and atrypid brachiopods, rugose and tabulate corals, and crinoids are all abundant in the oceans. Goniatite ammonoids are plentiful, while squid-like coleoids arise. Trilobites and armoured agnaths decline, while jawed fishes (placoderms, lobe-finned and ray-finned fish, and early sharks) rule the seas. First amphibians still aquatic. "Old Red Continent" of Euramerica. Beginning of Acadian Orogeny for Anti-Atlas Mountains of North Africa, and Appalachian Mountains of North America, also the Antler, Variscan, and Tuhua Orogeny in New Zealand.	374.5 ± 2.6^*
	Upper/Late		Frasnian		385.3 ± 2.6^*
	Middle		Givetian		391.8 ± 2.7^*
	Middle		Eifelian		397.5 ± 2.7^*
	Lower/Early		Emsian		407.0 ± 2.8^*
			Pragian		407.0 ± 2.8^*
			Lochkovian		416.0 ± 2.8^*
Silurian	Pridoli		no faunal stages defined	First Vascular plants (the rhyniophytes and their relatives), first millipedes and arthropleurids on land. First jawed fishes, as well as many armoured jawless fish, populate the seas. Sea-scorpions reach large size. Tabulate and rugose corals, brachiopods (Pentamerida, Rhynchonellida, etc.), and crinoids all abundant. Trilobites and mollusks diverse; graptolites not as varied. Beginning of Caledonian Orogeny for hills in England, Ireland, Wales, Scotland, and the Scandinavian Mountains. Also continued into Devonian period as the Acadian Orogeny, above. Taconic Orogeny tapers off. Lachlan Orogeny on Australian Continent tapers off.	418.7 ± 2.7^*
	Ludlow/Cayugan		Ludfordian		421.3 ± 2.6^*
	Ludlow/Cayugan		Gorstian		422.9 ± 2.5^*
	Wenlock		Homerian/Lockportian		426.2 ± 2.4^*
	Wenlock		Sheinwoodian/Tonawandan		428.2 ± 2.3^*
	Llandovery/Alexandrian		Telychian/Ontarian		436.0 ± 1.9^*
			Aeronian		439.0 ± 1.8^*
			Rhuddanian		443.7 ± 1.5^*
Ordovician	Upper/Late		Hirnantian	Invertebrates diversify into many new types (e.g., long straight-shelled cephalopods). Early corals, articulate brachiopods (Orthida, Strophomenida, etc.), bivalves, nautiloids, trilobites, ostracods, bryozoa, many types of echinoderms (crinoids, cystoids, starfish, etc.), branched graptolites, and other taxa all common. Conodonts (early planktonic vertebrates) appear. First green plants and fungi on land. Ice age at end of period.	445.6 ± 1.5^*
	Upper/Late		other faunal stages		460.9 ± 1.6^*
	Middle		Darriwilian		468.1 ± 1.6^*
	Middle		other faunal stages		471.8 ± 1.6^*
	Lower/Early		Arenig		471.8 ± 1.7^*
	Lower/Early		Tremadocian		488.3 ± 1.7^*
Cambrian	Furongian		other faunal stages	Major diversification of life in the Cambrian Explosion. Many fossils; most modern animal phyla appear. First chordates appear, along with a number of extinct, problematic phyla. Reef-building Archaeocyatha abundant; then vanish. Trilobites, priapulid worms, sponges, inarticulate brachiopods (unhinged lampshells), and many other animals numerous. Anomalocarids are giant predators, while many Ediacaran fauna die out. Prokaryotes, protists (e.g., forams), fungi and algae continue to present day. Gondwana emerges. Petermann Orogeny on the Australian Continent tapers off (550-535 MYA). Ross Orogeny in Antarctica. Adelaide Geosyncline (Delamerian Orogeny), majority of orogenic activity from 514-500 MYA. Lachlan Orogeny on Australian Continent, c. 540-440 MYA. Atmospheric Carbon Dioxide content roughly 20-35 times present-day (Holocene) levels (6000 ppmv compared to today's 385 ppmv)^[9]</ref>	496.0 ± 2.0^*
	Furongian		Paibian/Ibexian/ Ayusokkanian/Sakian/Aksayan		501.0 ± 2.0^*
	Middle		other faunal stages		513.0 ± 2.0
	Lower/Early		other faunal stages		542.0 ± 1.0^*
Precam- brian^[13]	Proter- ozoic^[14]	Neo- proterozoic^[14]	Ediacaran	Good fossils of the first multi-celled animals. Ediacaran biota flourish worldwide in seas. Simple trace fossils of possible worm-like Trichophycus, etc. First sponges and trilobitomorphs. Enigmatic forms include many soft-jellied creatures shaped like bags, disks, or quilts (like Dickinsonia). Taconic Orogeny in North America. Aravalli Range orogeny in Indian Subcontinent. Beginning of Petermann Orogeny on Australian Continent. Beardmore Orogeny in Antarctica, 633-620 MYA.			630 +5/-30^*
			Cryogenian	Possible "Snowball Earth" period. Fossils still rare. Rodinia landmass begins to break up. Late Ruker / Nimrod Orogeny in Antarctica tapers off.			850^[15]
			Tonian	Rodinia supercontinent persists. Trace fossils of simple multi-celled eukaryotes. First radiation of dinoflagellate-like acritarchs. Grenville Orogeny tapers off in North America. Pan-African Orogeny in Africa. Lake Ruker / Nimrod Orogeny in Antarctica, 1000 ± 150 MYA. Edmundian Orogeny (c. 920 - 850 MYA), Gascoyne Complex, Western Australia. Adelaide Geosyncline laid down on Australian Continent, beginning of Adelaide Geosyncline (Delamerian Orogeny) in that continent.			1000^[15]
		Meso- proterozoic^[14]	Stenian	Narrow highly metamorphic belts due to orogeny as Rodinia formed. Late Ruker / Nimrod Orogeny in Antarctica possibly begins. Musgrave Orogeny (c. 1080 MYA), Musgrave Block, Central Australia.			1200^[15]
			Ectasian	Platform covers continue to expand. Green algae colonies in the seas. Grenville Orogeny in North America.			1400^[15]
			Calymmian	Platform covers expand. Barramundi Orogeny, MacArthur Basin, Northern Australia, and Isan Orogeny, c. 1600 MYA, Mount Isa Block, Queensland			1600^[15]
		Paleo- proterozoic^[14]	Statherian	First complex single-celled life: protists with nuclei. Columbia is the primordial supercontinent. Kimban Orogeny in Australian Continent ends. Yapungku Orogeny on North Yilgarn craton, in Western Australia. Mangaroon Orogeny, 1680-1620 MYA, on the Gascoyne Complex in Western Australia. Kararan Orogeny (1650- MYA), Gawler Craton, South Australia.			1800^[15]
			Orosirian	The atmosphere became oxygenic. Vredefort and Sudbury Basin asteroid impacts. Much orogeny. Penokean and Trans-Hudsonian Orogenies in North America. Early Ruker Orogeny in Antarctica, 2000 - 1700 MYA. Glenburgh Orogeny, Glenburgh Terrane, Australian Continent c. 2005 - 1920 MYA. Kimban Orogeny, Gawler craton in Australian Continent begins.			2050^[15]
			Rhyacian	Bushveld Formation formed. Huronian glaciation.			2300^[15]
			Siderian	Oxygen Catastrophe: banded iron formations formed. Sleaford Orogeny on Australian Continent, Gawler Craton 2440-2420 MYA.			2500^[15]
	Archean^[14]	Neoarchean^[14]	Stabilization of most modern cratons; possible mantle overturn event. Insell Orogeny, 2650 ± 150 MYA. Abitibi greenstone belt in present-day Ontario and Quebec begins to form, stablizes by 2600 MYA.				2800^[15]
		Mesoarchean^[14]	First stromatolites (probably colonial cyanobacteria). Oldest macrofossils. Humboldt Orogeny in Antarctica. Blake River Megacaldera Complex begins to form in present-day Ontario and Quebec, ends by roughly 2696 MYA.				3200^[15]
		Paleoarchean^[14]	First known oxygen-producing bacteria. Oldest definitive microfossils. Oldest cratons on earth (such as the Canadian Shield and the Pilbara Craton) may have formed during this period^[16]. Rayner Orogeny in Antarctica.				3600^[15]
		Eoarchean^[14]	Simple single-celled life (probably bacteria and perhaps archaea). Oldest probable microfossils.				3800
	Hadean ^[14]^[17]	Lower Imbrian^[14]^[18]	This era overlaps the end of the Late Heavy Bombardment of the inner solar system.				c.3850
		Nectarian^[14]^[18]	This era gets its name from the lunar geologic timescale when the Nectaris Basin and other major lunar basins were formed by large impact events.				c.3920
		Basin Groups^[14]^[18]	Oldest known rock (4030 Ma)^[19]. The first Lifeforms and self-replicating RNA molecules may have evolved on earth around 4000 Ma during this era. Naiper Orogeny in Antarctica, 4000 ± 200 MYA.				c.4150
		Cryptic^[14]^[18]	Oldest known mineral (Zircon, 4406±8 Ma^[20]). Formation of Earth (4567.17 to 4570 Ma)				c.4570

^ John McPhee, Basin and Range, New York:Farrar, Straus and Giroux, 1981, pp.95-100.
^ John McPhee, Basin and Range, pp.113-114.
^ (1974) Great Soviet Encyclopedia, 3rd ed. (in Russian), Moscow: Sovetskaya Enciklopediya, vol. 16, p. 50.
^ Felix M. Gradstein, James G. Ogg, Alan G. Smith (Editors); A Geologic Time Scale 2004, Cambridge University Press, 2005, (ISBN 0-521-78673-8)
^ Cox & Richard, A formal model for the geologic time scale and global stratotype section and point, compatible with geospatial information transfer standards, Geosphere, volume 1, pp 119-137, Geological Society of America, 2005
^ Paleontologists often refer to faunal stages rather than geologic (geological) periods. The stage nomenclature is quite complex. See The Paleobiology Database. Retrieved on 2006-03-19. for an excellent time ordered list of faunal stages.
^ ^a ^b 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: see List of Global Boundary Stratotype Sections and Points for a complete list.
^ ^a ^b ^c ^d 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.
^ ^a ^b ^c ^d ^e ^f For more information on this, see the following articles: Earth's atmosphere, Carbon Dioxide, Carbon dioxide in the Earth's atmosphere, Image:Phanerozoic_Carbon_Dioxide.png, Image:65 Myr Climate Change.png, Image:Five Myr Climate Change.png, and Template:DF temperature
^ The start time for the Holocene epoch is here given as 11,430 years ago ± 130 years (that is, between 9610 BC-9560 BC and 9350 BC-9300 BC). For further discussion of the dating of this epoch, see Holocene.
^ ^a ^b MYA = Million Years Ago
^ ^a ^b In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods.
^ The Precambrian is also known as Cryptozoic.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ The Proterozoic, Archean and Hadean are often collectively referred to as the Precambrian Time or sometimes, also the Cryptozoic.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l Defined by absolute age (Global Standard Stratigraphic Age).
^ The age of the oldest measurable craton, or continental crust, is dated to 3600-3800 Ma
^ Though commonly used, the Hadean is not a formal eon and no lower bound for the Archean and Eoarchean have been agreed upon. The Hadean has also sometimes been called the Priscoan or the Azoic. Sometimes, the Hadean can be found to be subdivided according to the lunar geologic time scale. These eras include the Cryptic and Basin Groups (which are subdivisions of the pre-Nectarian era), Nectarian, and Lower Imbrian eras.
^ ^a ^b ^c ^d These era names were taken from the Lunar geologic timescale. Their use for Earth geology is unofficial.
^ Oldest rock on earth is the Acasta Gneiss, and it dates to 4.03 Ga, located in the Northwest Territories of Canada.
^ http://www.geology.wisc.edu/%7Evalley/zircons/Wilde2001Nature.pdf

[edit] References and footnotes

[edit] See also

[edit] External links

NASA: Geologic Time
GSA: Geologic Time Scale
British Geological Survey: Geological Timechart
GeoWhen Database
International Commission on Stratigraphy Time Scale
CHRONOS
National Museum of Natural History - Geologic Time
SeeGrid: Geological Time Systems Information model for the geologic time scale
Exploring Time from Planck Time to the lifespan of the universe

v • d • e Time

Major concepts	Time · Eternity · Arguments for eternity · Immortality Deep time · History · Past · Present · Future · Futurology	Time Portal

Measurement and Standards	Chronometry · UTC · UT · TAI · Second · Minute · Hour · Sidereal time · Solar time · Time zone Clock · Horology · History of timekeeping devices · Astrarium · Marine chronometer · Sundial · Water clock Calendar · Day · Week · Month · Year · Tropical year · Julian · Gregorian · Islamic Intercalation · Leap second · Leap year

Chronology	Astronomical chronology · Geologic Time · Geological history · Geochronology · Archaeological dating Calendar era · Regnal year · Chronicle · Timeline · Periodization

Religion and Mythology	Time and fate deities · Wheel of time · Kāla · Kalachakra · Prophecy · Dreamtime

Philosophy	Causality · Eternalism · Eternal return · Event · The Unreality of Time · A-series and B-series · B-Theory of time Endurantism · Four dimensionalism · Perdurantism · Presentism · Temporal finitism · Temporal parts

Physical Sciences	Time in physics · Spacetime · Absolute time and space · T-symmetry Arrow of time · Chronon · Fourth dimension · Planck epoch · Planck time · Time domain Theory of relativity · Time dilation · Gravitational time dilation · Coordinate time · Proper time

Psychology	Consciousness and spacetime · Mental chronometry · Reaction time · Sense of time · Specious present

Sociology and Anthropology	Futures studies · Long Now Foundation · Time discipline · Time use research

Economics	Newtonian time in economics · Time value of money

Related topics	Space · Duration · Time capsule · Time travel · Time signature · System time · Carpe diem · Tempus fugit

v • d • e Time measurement and standards

Major subjects	Time · Chronometry · Orders of magnitude · Units of time · Metrology	Time Portal

International standards	UTC · UT · TAI · ISO 31-1 · Second · DUT1 · Leap second · IERS Terrestrial Time · Geocentric Coordinate Time · Barycentric Coordinate Time Civil time · Minute · Hour · 12-hour clock · 24-hour clock · ISO 8601 International Date Line · Solar time · Time zone · Daylight saving time · Time offset · Annum

Obsolete standards	Ephemeris time · Barycentric Dynamical Time · Greenwich Mean Time · Prime Meridian

Time in physics	Spacetime · Chronon · Cosmological decade · Planck epoch · Planck time · T-symmetry Theory of relativity · Time dilation · Gravitational time dilation · Coordinate time · Proper time Time domain · Continuous time · Discrete time · Absolute time and space

Horology	Clock · Astrarium · Atomic clock · Hourglass · Marine chronometer · Radio clock · Sundial · Watch · Water clock History of timekeeping devices · Equation of time · Complication

Calendar	Day · Week · Month · Year · Decade · Century · Millennium Astronomical · Julian · Gregorian · Islamic · Lunisolar · Solar · Lunar · Epact · Intercalation · Leap year Tropical year · Equinox · Solstice · Days of the week · Calculating the day of the week · Dominical letter

Archaeology & geology	International Commission on Stratigraphy · Geologic Time · Archaeological dating

Astronomical chronology	Nuclear time scale · Precession · Sidereal time · Galactic year

Unusual units	Fortnight · Jiffy · Lustrum · Saeculum · Shake · Tide

Related topics	Chronology · Duration · System time · Mental chronometry · Time value of money · Timekeeper

v • d • e Chronology

Major subjects	Time · Astronomy · Geology · Paleontology · Archaeology · History	Time Portal

Eras and Epochs	Calendar Eras: Ab urbe condita · Anno Domini / Common Era · Anno Mundi · Spanish era · Before Present · Hijri Egyptian · Sothic cycle · Hindu units of measurement · Hindu Yugas Regnal year: Canon of Kings · King lists · Limmu · Seleucid era · Era name: Chinese · Japanese · Korean

Calendars	Pre-Julian Roman · Original Julian · Proleptic Julian · Revised Julian Gregorian · Proleptic Gregorian · Old Style and New Style Lunisolar · Solar · Lunar · Islamic · Chinese sexagenary cycle Astronomical year numbering · ISO week date

Astronomic time and techniques	Astronomical chronology · Cosmic Calendar · Ephemeris · Galactic year · Metonic cycle · Milankovitch cycles

Geologic time and techniques	Deep time · Geological history · Eon · Eras · Periods · Faunal stage Chronostratigraphy · Geochronology · Isotope geochemistry · Law of superposition · Optical dating · Samarium-neodymium dating

Archaeological techniques	Dating methodology Absolute dating · Incremental dating · Archaeomagnetic dating · Dendrochronology · Glottochronology · Ice core · Lichenometry · Paleomagnetism · Radiocarbon dating · Radiometric dating · Tephrochronology · Thermoluminescence dating · Uranium-lead dating Relative dating · Seriation · Stratification

Genetic techniques	Amino acid dating · Molecular clock

Related topics	Chronicle · New Chronology · Periodization · Synchronoptic view · Timeline · Year zero · Circa · Floruit

Hidden categories: Articles to be merged since August 2007 | Articles needing additional references from April 2007

See also ebooksgratis.com: no banners, no cookies, totally FREE.

Geologic time scale

From Wikipedia, the free encyclopedia

Contents

[edit] Graphical timelines

[edit] Terminology

[edit] History of the time scale

[edit] Table of geologic time

[edit] References and footnotes

[edit] See also

[edit] External links

Views

Navigation

Interaction

Search

Languages