Cambrian period 542 - 488. 3 million years ago ↓ PЄ Є O S D C P T J K PG N
Mean atmospheric O2 content over period duration	ca. The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Silurian is a geologic period and system that extends from the end of the Ordovician period about 443 The Devonian is a geologic period and system of the Paleozoic era spanning from to  million years ago. The Carboniferous is a geologic period and system that extends from the end of the Devonian period about 359 The Permian is a geologic period and system that extends from 299 The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of The Paleogene (alternatively Palaeogene) is a geologic period and system that began 65 The Neogene is a geologic period and system starting 2303 ± 0 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 12. 5 Vol %[1] (63 % of modern level)
Mean atmospheric CO2 content over period duration	ca. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single 4500 ppm[2] (16 times pre-industrial level)
Mean surface temperature over period duration	ca. "Parts-per" notation is used especially in Science and Engineering, to denote Ratios (relative proportions in measured quantities particularly 21°C [3] (7°C above modern level)
Key events in the Cambrian view • discuss • edit -545 — – -540 — – -535 — – -530 — – -525 — – -520 — – -515 — – -510 — – -505 — – -500 — – -495 — – -490 — –       Ediacaran   Nemakit- Daldynian Tommotian Atdabanian Botomian Toyonian Middle Cambrian Furongian Ordovician     ← Orsten Fauna ← Burgess Shale ← Sirius Passet Fauna[4] ← Chengjiang Fauna ← First Trilobites ← First Arthropod trace fossils C a m b r i a n ← and Echinoderms  Neoproterozoic (last era of the Precambrian)  Palæozoic (first era of the Phanerozoic) An approximate timescale of key Cambrian events. The Ediacaran Period (ˌiːdiˈækərən named after the Ediacara Hills of South Australia) is the last geological period of the Neoproterozoic The Tommotian Age, named after the Mollusc Tommotia, which began approx The Middle Cambrian (also known as Albertan, Acadian, St David's, or Saint David's) is the second of three geological epochs of the The Middle Cambrian (also known as Albertan, Acadian, St David's, or Saint David's) is the second of three geological epochs of the The Furongian (which represented approximately the old notions of Late Cambrian, Merioneth, Croixian, or Potsdamian) is the third and final The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Upper Cambrian Orsten fauna includes fossilized organisms preserved in Orsten Lagerstätten notably at Kinnekulle and in the island of Öland See also Burgess shale type fauna The Burgess Shale is famous for the exceptional preservation of the fossils found within it in which the soft parts are preserved Sirius Passet is a Cambrian Lagerstätte in Greenland. The Sirius Passet Lagerstätte was named after the Sirius sledge patrol that operates in North Greenland In the Maotianshan shales is a lower Cambrian Konservat Lagerstätte named for Maotianshan Hill ( in Chengjiang County Yunnan Province Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita. Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Trace fossils, also called ichnofossils (ˈɪknoʊfɒsɨl ιχνος or ikhnos meaning "trace" or "track" are geological records of biological Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) The Neoproterozoic Era is the unit of geologic time from 1000 to 542 +/- 0 The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current The Paleozoic or Palaeozoic Era (from the Greek palaio (παλαιο "old" and zoe (ζωη "life" meaning "ancient life" The Phanerozoic (occasionally Phanaerozoic) Eon is the current eon in the Geologic timescale, and the one during which abundant animal life has existed The Cambrian explosion took place during the lower Cambrian, but its duration is poorly defined. The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex Animals around, as evidenced by the Axis scale: millions of years ago.

The Cambrian is a geologic period and system that began about 542± 0. 3 Ma (million years ago) at the end of the Proterozoic eon and ended about 488. In Astronomy, Geology, and Paleontology, mya or " mya " is an abbreviation for "million years ago". The Proterozoic (ˌproʊtərəˈzoʊɪk is a geological eon representing a period before the first abundant complex life on Earth. 3± 1. 7 Ma with the beginning of the Ordovician period (ICS, 2004)^[5]. The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The International Commission on Stratigraphy (ICS, sometimes referred to by the unofficial " International Stratigraphic Commission " is a daughter or major Subcommittee It was the first period of the Paleozoic era of the Phanerozoic eon. The Paleozoic or Palaeozoic Era (from the Greek palaio (παλαιο "old" and zoe (ζωη "life" meaning "ancient life" The Phanerozoic (occasionally Phanaerozoic) Eon is the current eon in the Geologic timescale, and the one during which abundant animal life has existed The Cambrian takes its name from Cambria, the classical name for Wales, the area where rocks from this time period were first studied. Cambria is the classical name for Wales, being the Latinised form of the Welsh name Cymru (Wales

The Cambrian is the earliest period in whose rocks are found numerous large, distinctly fossilizable multicellular organisms. This sudden appearance of hard body fossils is referred to as the Cambrian explosion. The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex Animals around, as evidenced by the Despite the long recognition of its distinction from younger Ordovician rocks and older Precambrian rocks it was not until 1994 that this time period was internationally ratified. The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current The base of the Cambrian is defined on a complex assemblage of trace fossils known as the Trichophycus pedum assemblage. Trace fossils, also called ichnofossils (ˈɪknoʊfɒsɨl ιχνος or ikhnos meaning "trace" or "track" are geological records of biological Trichophycus pedum (or Treptichnus pedum; formerly Phycodes pedum) is regarded as the earliest widespread complex Trace fossil This assemblage is distinct from anything in the Precambrian as it has ecologically tiered vertical burrows which are absent from the Precambrian.

Cambrian subdivisions

The Cambrian period follows the Ediacaran and is followed by the Ordovician period. The Ediacaran Period (ˌiːdiˈækərən named after the Ediacara Hills of South Australia) is the last geological period of the Neoproterozoic The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Cambrian is divided into three epochs — the Early Cambrian (Caerfai or Waucoban), Middle Cambrian (St Davids or Albertian) and Furongian (also known as Late Cambrian, Merioneth or Croixan). The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other The Early Cambrian (also known as the Caerfai, Waucoban, or Georgian) is the first of three geological epochs of the Cambrian The Middle Cambrian (also known as Albertan, Acadian, St David's, or Saint David's) is the second of three geological epochs of the The Furongian (which represented approximately the old notions of Late Cambrian, Merioneth, Croixian, or Potsdamian) is the third and final Rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian.

Each of the epochs are divided into several stages. Only one, the Paibian, has been recognized by the International Commission on Stratigraphy, and others are still unnamed. In the Geologic timescale, the Paibian is the age of the Furongian epoch of the Cambrian period of the Paleozoic The International Commission on Stratigraphy (ICS, sometimes referred to by the unofficial " International Stratigraphic Commission " is a daughter or major Subcommittee However, the Cambrian is divided into several regional faunal stages of which the Russian-Kazakhian system is most used in international parlance:

Cambrian dating

The time range for the Cambrian has classically been thought to have been from about 500 mya to about 570 mya. The Furongian (which represented approximately the old notions of Late Cambrian, Merioneth, Croixian, or Potsdamian) is the third and final The Ibexian is recognized as the youngest Cambrian and oldest Ordovician series in North America The Ayusokkanian is a Russian and Kazakhian faunal stage that occurred during the Early Cambrian period The Sakian is a Russian and Kazakhian faunal stage of the Late Cambrian period that occurred between 494 The Aksayan is a Russian and Kazakhian faunal stage of the Cambrian that occurred between 493 To 491 The Middle Cambrian (also known as Albertan, Acadian, St David's, or Saint David's) is the second of three geological epochs of the The Mayan stage is the final Russian and Kazakhian Faunal stage of the Middle Cambrian Epoch. The Early Cambrian (also known as the Caerfai, Waucoban, or Georgian) is the first of three geological epochs of the Cambrian The Tommotian Age, named after the Mollusc Tommotia, which began approx The lower boundary of the Cambrian was traditionally set at the earliest appearance of early arthropods known as trilobites and also unusual forms known as archeocyathids (literally 'ancient cup') that are thought to be the earliest sponges and also the first non-microbial reef builders. Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita. The Archaeocyatha or archaeocyathids ("ancient cups" were Sessile In nautical terminology a reef is a rock, sandbar, or other feature lying beneath the surface of the water (six fathoms or less at low water

The end of the period was eventually set at a fairly definite faunal change now identified as an extinction event. An extinction event (also known as mass extinction; extinction-level event, ELE is a sharp decrease in the number of Species in a relatively short period Fossil discoveries and radiometric dating in the last quarter of the 20th century have called these dates into question. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Radiometric dating (often called radioactive dating) is a technique used to date materials usually based on a comparison between the observed abundance of a naturally occurring Date inconsistencies as large as 20 Ma are common between authors. Annum is one form of the Latin noun meaning Year, not a form normally used for derivatives in modern languages the accusative singular Framing dates of ca. () 545 to 490 mya were proposed by the International Subcommission on Global Stratigraphy as recently as 2002.

A radiometric date from New Brunswick puts the end of the first stage of the Cambrian around 511 mya. New Brunswick ( French: Nouveau-Brunswick /nuvobʁɔnzwik/ is one of Canada 's three Maritime provinces and is the only constitutionally This leaves 21 Ma for the other two stages of the Cambrian.

A more precise date of 542 ± 0. 3 mya for the extinction event at the beginning of the Cambrian has recently been submitted. ^[6] The rationale for this precise dating is interesting in itself as an example of paleological deductive reasoning. Palaeontology redirects here For the Scientific journal, see Palaeontology (journal. Deductive reasoning is Reasoning which uses deductive Arguments to move from given statements ( Premises to Conclusions which must be true if the Exactly at the Cambrian boundary there is a marked fall in the abundance of carbon-13, a "reverse spike" that paleontologists call an excursion. Carbon-13 ( 13C) is a natural stable Isotope of Carbon and one of the Environmental isotopes. Palaeontology redirects here For the Scientific journal, see Palaeontology (journal. It is so widespread that it is the best indicator of the position of the Precambrian-Cambrian boundary in stratigraphic sequences of roughly this age. Stratigraphy, a branch of Geology, studies rock layers and layering ( stratification) One of the places that this well-established carbon-13 excursion occurs is in Oman. Oman, officially the Sultanate of Oman ( Arabic: سلطنة عُمان) is an Arab Country in Southwest Asia on the southeast Amthor (2003) describes evidence from Oman that indicates the carbon-isotope excursion relates to a mass extinction: the disappearance of distinctive fossils from the Precambrian coincides exactly with the carbon-13 anomaly. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current Fortunately, in the Oman sequence, so too does a volcanic ash horizon from which zircons provide a very precise age of 542 ± 0. Volcanic ash consists of small Tephra, which are bits of pulverized rock and glass created by volcanic eruptions less than in diameter Zircon is a Mineral belonging to the group of nesosilicates. Its chemical name is Zirconium silicate and its corresponding chemical formula is 3 Ma (calculated on the decay rate of uranium to lead). Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly This new and precise date tallies with the less precise dates for the carbon-13 anomaly, derived from sequences in Siberia and Namibia. Siberia (Сиби́рь Sibir) is the name given to the vast region constituting almost all of Northern Asia and for the most part currently serving Namibia, officially the Republic of Namibia, is a country in Southern Africa on the Atlantic coast It is presented here as likely to become accepted as the definitive age for the start of the Phanerozoic eon, and thus the start of the Paleozoic era and the Cambrian period.

Cambrian paleogeography

The continental distribution in the early Cambrian epoch, 514 million years ago.

Cambrian continents are thought to have resulted from the breakup of a Neoproterozoic supercontinent called Pannotia. A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions The Neoproterozoic Era is the unit of geologic time from 1000 to 542 +/- 0 In Geology, a supercontinent is a Landmass comprising more than one Continental core or Craton. Pannotia, first described by Ian W D Dalziel in 1997 is a hypothetical Supercontinent that existed from the Pan-African orogeny about 600 million years ago to the The waters of the Cambrian period appear to have been widespread and shallow. Gondwana remained the largest supercontinent after the breakup of Pannotia. Pannotia, first described by Ian W D Dalziel in 1997 is a hypothetical Supercontinent that existed from the Pan-African orogeny about 600 million years ago to the It is thought that Cambrian climates were significantly warmer than those of preceding times that experienced extensive ice ages discussed as the Varanger glaciation. Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of An ice age is a period of long-term reduction in the Temperature of the Earth 's surface and atmosphere resulting in an expansion of continental Ice sheets The Cryogenian (from Greek cryos "cold" and genesis "birth" is a Geologic period that lasted from. Also there was no glaciation at the poles. Continental drift rates in the Cambrian may have been anomalously high. Continental drift is the movement of the Earth 's Continents relative to each other Laurentia, Baltica and Siberia remained independent continents since the break-up of the supercontinent of Pannotia. Laurentia (also known as the North American craton) like all Craton land was created as continents moved about the surface of the Earth Baltica redirects here For the Russian beer, see Baltika Breweries Baltica is a name applied by geologists to a late- Proterozoic, Siberia is the Craton located in the heart of the region of Siberia. Gondwana started to drift towards the South Pole. The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the southernmost point on the surface of the Earth. Panthalassa covered most of the southern hemisphere, and minor oceans included the Proto-Tethys Ocean, Iapetus Ocean, and Khanty Ocean, all of which expanded by this time. Panthalassa ( Greek, meaning 'all seas' also known as the Panthalassic Ocean, was the vast global Ocean that surrounded the Supercontinent The Proto-Tethys Ocean was an ancient Ocean that existed from the latest Ediacaran to the Carboniferous (550-330 Ma) The Iapetus Ocean was an Ocean that existed in the Southern Hemisphere between Laurentia ( Scotland and North America) and Baltica Khanty Ocean was an ancient small ocean that existed near the end of the Precambrian time to the Silurian.

Cambrian fauna

Fossil trilobite Redlichia chinensis from the Cambrian of China

Of those modern animal phyla that fossilize easily, all save the bryozoans have claimed representatives in the Cambrian. Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita. Bryozoans are tiny colonial Animals that generally build stony Skeletons of Calcium carbonate, superficially similar to Coral (although some Many extinct phyla and odd animals that have unclear relationships to other animals also appear in the Cambrian. In Biology and Ecology, extinction is the cessation of existence of a Species or group of taxa. The apparent "sudden" appearance of very diverse faunas over a period of no more than a few tens of millions of years is referred to as the "Cambrian Explosion". The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex Animals around, as evidenced by the Also, the first possible tracks on land, such as Protichnites and Climactichnites, dating to about 530 mya and found in Ontario, Canada, and northern United States, appeared at this time. Protichnites is a genus of Trace fossil consisting of the imprints made by the walking activity of Arthropods It is likely that more than one type of arthropod Climactichnites is an enigmatic late Cambrian fossil formed on sandy tidal flats around. Ontario (ɒnˈtɛrioʊ is a province located in the central part of Canada, the largest by population and second largest after Quebec Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page The conodonts, small predatory primitive chordates known from their fossilised teeth, also appeared during the Furongian epoch of the Cambrian period. Conodonts are extinct chordates resembling eels classified in the class Conodonta. The conodonts thrived throughout the Paleozoic and the early Mesozoic until they completely disappeared during the Late Triassic period when the first mammals were evolving.

The best studied sites where the soft parts of organisms have fossilized are in the Burgess shale of British Columbia. See also Burgess shale type fauna The Burgess Shale is famous for the exceptional preservation of the fossils found within it in which the soft parts are preserved British Columbia (ˌbrɪtɨʃ kəˈlʌmbiə ( BC) ( (la Colombie-Britannique C They represent strata from the Middle Cambrian and provide us with a wealth of information on early animal diversity. Similar faunas have subsequently been found in a number of other places — most importantly in very early Cambrian shales in the People's Republic of China's Yunnan Province (see Maotianshan shales). Shale (also called mudstone) is a fine-grained Sedimentary rock whose original constituents were Clay minerals or Muds It is characterized by Talk People's Republic of China) PEOPLE'S REPUBLIC OF CHINA ARTICLE GUIDELINES In the Maotianshan shales is a lower Cambrian Konservat Lagerstätte named for Maotianshan Hill ( in Chengjiang County Yunnan Province Fairly extensive Precambrian Ediacaran faunas have been identified in the past 50 years, but their relationships to Cambrian forms are quite obscure. The Ediacara (ˌiːdɪˈækərə formerly Vendian) biota are ancient lifeforms of the Ediacaran Period which represent the earliest known complex

Cambrian flora

Generally it is accepted that there were no land plants at this time although molecular dating suggests that land plant ancestors diverged from the algae much earlier, in the Neoproterozoic about 700 ma, and that fungi diverged from the animals about 1 billion years ago. The embryophytes are the most familiar group of Plants They include Trees Flowers Ferns Mosses and various other green The Neoproterozoic Era is the unit of geologic time from 1000 to 542 +/- 0 Annum is one form of the Latin noun meaning Year, not a form normally used for derivatives in modern languages the accusative singular A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ The land at this time was barren, mostly desert and badlands. A desert is a Landscape or region that receives very little precipitation. Badlands are a type of Arid Terrain where softer sedimentary rocks and Clay -rich Soils have been extensively eroded by Wind

See also

• List of fossil sites (with link directory)
• Cambrian-Ordovician extinction events

References

• Gould, Stephen Jay; Wonderful Life: the Burgess Shale and the Nature of Life (New York: Norton, 1989)
• Amthor, J. Stephen Jay Gould (September 10 1941 &ndash May 20 2002 was a prominent American paleontologist, evolutionary biologist, and historian of science See also Burgess shale type fauna The Burgess Shale is famous for the exceptional preservation of the fossils found within it in which the soft parts are preserved E. ; and others (2003). "Extinction of Cloudina and Namacalathus at the Precambrian-Cambrian boundary in Oman". The Cloudinids, early Metazoan family containing the Genus Cloudina, lived in the late Ediacaran period and Namacalathus is a problematic Metazoan Fossil occurring in the latest Proterozoic Nama Group of central and southern Namibia. Geology 31: pp 431–434. doi:10.1130/0091-7613(2003)031<0431:EOCANA>2.0.CO;2. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. doi:10.1130/0091-7613(2003)031<0431:EOCANA>2.0.CO;2 10.1130/0091-7613(2003)031<0431:EOCANA>2.0.CO;2 . A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
• Ogg, Jim; June, 2004, Overview of Global Boundary Stratotype Sections and Points (GSSP's) http://www.stratigraphy.org/gssp.htm Accessed April 30, 2006.

External links

• Weird Life on the Mats
• Dr. Sam Gon's trilobite pages (contains numerous Cambrian trilobites)
  • Biostratigraphy - includes information on Cambrian trilobite biostratigraphy
• Report on the web on Amthor and others from Geology vol. 31
• Paleomap Project
• Examples of Cambrian Fossils