Cambrian Period 542–488.3 million years ago PreЄ Є O S D C P T J K Pg N
Mean atmospheric O2 content over period duration	ca. 12.5 Vol %[1] (63 % of modern level)
Mean atmospheric CO2 content over period duration	ca. 4500 ppm[2] (16 times pre-industrial level)
Mean surface temperature over period duration	ca. 21 °C[3] (7 °C above modern level)
Sea level (above present day)	Rising steadily from 30m to 90m[4]

The Cambrian is the first geological period of the Paleozoic Era, lasting from 542 ± 0.3 to 488.3 ± 1.7 million years ago (mya) (ICS, 2004^[5]); it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's Cambrian rocks are best exposed.^[6] The Cambrian is unique in its unusually high proportion of lagerstätten. These are sites of exceptional preservation, where 'soft' parts of organisms are preserved as well as their more resistant shells. This means that our understanding of the Cambrian biology surpasses that of some later periods.^[7]

The Cambrian Period marked a profound change in life on Earth; prior to the Cambrian, living organisms on the whole were small, unicellular and simple. Complex, multicellular organisms gradually became more common in the millions of years immediately preceding the Cambrian, but it was not until this period that mineralised – hence readily fossilised – organisms became common.^[8] The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, produced the first representatives of many modern phyla, representing the evolutionary stems of modern groups of species, such as the arthropods. While diverse life forms prospered in the oceans, the land was comparatively barren – with nothing more complex than a microbial soil crust. Most of the continents probably resembled deserts.^{[citation needed]} Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia.The seas were relatively warm, and polar ice was absent for much of the period.

The United States Federal Geographic Data Committee uses a "barred capital C" character similar to the capital letter Ukrainian Ye ‹Є› to represent the Cambrian Period.^[9] The proper^[10] glyph is in the Unicode standard at code point A792.^[11]

Stratigraphy[link]

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 base of the Cambrian is defined on a complex assemblage of trace fossils known as the Treptichnus pedum assemblage.^[12] Nevertheless, the usage of Treptichnus pedum, a reference ichnofossil for the lower boundary of the Cambrian, for the stratigraphic detection of this boundary is always risky because of occurrence of very similar trace fossils belonging to the Treptichnids group well below the T. pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA. The stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain.^[13][14]

[edit] Subdivisions

The Cambrian period follows the Ediacaran and is followed by the Ordovician period. The Cambrian is divided into four epochs or series and ten ages or stages. Currently only two series and four stages are named and have a GSSP.

Because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used. In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian (Caerfai or Waucoban, 542 ± 0.3 to 513 ± 1.7 mya), Middle Cambrian (St Davids or Albertian, 513 ± 0.3 to 499 ± 1.7 mya) and Furongian (499 ± 0.3 to 488.3 ± 1.7 mya; also known as Late Cambrian, Merioneth or Croixan). Rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian.

Trilobite zones allow biostratigraphic correlation in the Cambrian.

Each of the local epochs is divided into several stages. The Cambrian is divided into several regional faunal stages of which the Russian-Kazakhian system is most used in international parlance:

*In Russian tradition the lower boundary of the Cambrian is suggested to be defined at the base of the Tommotian Stage which is characterized by diversification and global distribution of organisms with mineral skeletons and the appearance of the first Archaeocyath bioherms.^[15][16][17]

Cambrian dating[link]

Archeocyathids from the Poleta formation in the Death Valley area

The time range for the Cambrian has classically been thought to have been from about 542 mya to about 488 mya. The lower boundary of the Cambrian was traditionally set at the earliest appearance of 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.

The end of the period was eventually set at a fairly definite faunal change now identified as an extinction event. Fossil discoveries and radiometric dating in the last quarter of the 20th century have called these dates into question. Date inconsistencies as large as 20 million years are common between authors. 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 Lower Cambrian around 511 mya. This leaves 21 mya for the other two series/epochs 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.^[18] The rationale for this precise dating is interesting in itself as an example of paleological deductive reasoning. Exactly at the Cambrian boundary there is a marked fall in the abundance of carbon-13, a "reverse spike" that paleontologists call an excursion. 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. One of the places that this well-established carbon-13 excursion occurs is in Oman. 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. Fortunately, in the Oman sequence, so too does a volcanic ash horizon from which zircons provide a very precise age of 542 ± 0.3 mya (calculated on the decay rate of uranium to lead). This new and precise date tallies with the less precise dates for the carbon-13 anomaly, derived from sequences in Siberia and Namibia.

Paleogeography[link]

Plate reconstructions suggest that a global supercontinent, Pannotia, was in the process of breaking up early in the period,^[19][20] with Laurentia (North America), Baltica, and Siberia having separated from the main supercontinent of Gondwana to form isolated landmasses.^[21] Most continental land was clustered in the southern hemisphere at this time, but was gradually drifting north.^[21] Large, high-velocity rotational movement of Gondwana appears to have occurred in the Early Cambrian.^[22]

With a lack of sea ice – the great glaciers of the Marinoan Snowball Earth were long melted^[23] – the sea level was high, which led to large areas of the continents being flooded in warm, shallow seas ideal for thriving life. The sea levels fluctuated somewhat, suggesting that there were 'ice ages', associated with pulses of expansion and contraction of a south polar ice cap.^[24]

Climate[link]

The Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwana covering the South Pole and cutting off polar ocean currents. There were likely polar ice caps and a series of glaciations, as the planet was still recovering from an earlier Snowball Earth. It became warmer towards the end of the period; the glaciers receded and eventually disappeared, and sea levels rose dramatically. This trend would continue into the Ordovician period.

Fauna[link]

All animal life during the Cambrian was aquatic. The period marked a steep change in the diversity and composition of Earth's biosphere. The incumbent Ediacaran biota suffered a mass extinction at the base of the period, which corresponds to an increase in the abundance and complexity of burrowing behaviour. This behaviour had a profound and irreversible effect on the substrate which transformed the seabed ecosystems. Before Cambrian, the sea floor was covered by microbial mats. By the end of the period, burrowing animals had destroyed the mats through bioturbation, and gradually turned the seabeds into what they are today. As a consequence, many of those organisms who were dependent on the mats went extinct, while the other species adapted to the changed environment who now offered new ecological niches.^[25] Around the same time there was a seemingly rapid appearance of representatives of all the mineralized phyla.^[26] However, many of these phyla were represented only by stem-group forms; and since mineralized phyla generally have a benthic origin, they may not be a good proxy for (more abundant) non-mineralized phyla.^[27]

There are also suggestions that some Cambrian organisms ventured onto land, producing the trace fossils Protichnites and Climactichnites.

In contrast to later periods, the Cambrian fauna was somewhat restricted; free-floating organisms were rare, with the majority living on or close to the sea floor;^[28] and mineralizing animals were rarer than in future periods, in part due to the unfavourable ocean chemistry.^[28] (Most Cambrian carbonates were formed by microbial or non-biological processes.)^[28]

Many modes of preservation are unique to the Cambrian, resulting in an abundance of lagerstätte.

Flora[link]

Although there were a variety of macroscopic marine plants, it is generally accepted that there were no land plants at this time, although it is likely that a microbial "scum" comprising fungi, algae, and possibly lichens covered the land.^[29]

See also[link]

Part of a series on
The Cambrian explosion
Fossil localities Burgess shale Chengjiang Sirius Passet Doushantuo
Key organisms Ediacara biota Kimberella Vernanimalcula Burgess-type Marrella Anomalocaridids Halwaxiids Opabinia Odontogriphus Small shelly fauna Helcionellids
Evolutionary concepts Trends Cambrian substrate revolution Themes Cladistics Convergent evolution Stem and crown groups
v t e • taskforce

• End Botomian extinction event—circa 517 mya
• Dresbachian extinction event—circa 502 mya
• Cambro-Ordovician extinction event – circa 488 mya
• List of fossil sites (with link directory)
• Type locality (geology), the locality where a particular rock type, stratigraphic unit, fossil or mineral species is first identified

v t e Modes of preservation in the Cambrian Exceptional Phosphate Orsten type · Doushantuo type Silica Bitter Springs type Carbonaceous film Burgess Shale type Pyrite Beecher's Trilobite Bed type Casts and moulds Ediacaran type Legged trilobite fossil Conventional Shelly Small shelly fossils · Conventional fossils Organic Acritarchs · Organic-walled microfossils Traces Microbialites · Trace fossils

References[link]

Further reading[link]

• Amthor, J. E.; Grotzinger, John P.; Schröder, Stefan; Bowring, Samuel A.; Ramezani, Jahandar; Martin, Mark W.; Matter, Albert (2003). "Extinction of Cloudina and Namacalathus at the Precambrian-Cambrian boundary in Oman". Geology 31 (5): 431–434. Bibcode 2003Geo....31..431A. DOI:10.1130/0091-7613(2003)031<0431:EOCANA>2.0.CO;2. 
• Ogg, Jim; June, 2004, Overview of Global Boundary Stratotype Sections and Points (GSSPs) http://www.stratigraphy.org/gssp.htm Accessed April 30, 2006.
• Gould, Stephen Jay; Wonderful Life: the Burgess Shale and the Nature of Life (New York: Norton, 1989)

External links[link]

Wikimedia Commons has media related to: Cambrian

• Cambrian period on In Our Time at the BBC. (listen now)
• Biostratigraphy – includes information on Cambrian trilobite biostratigraphy
• Dr. Sam Gon's trilobite pages (contains numerous Cambrian trilobites)
• Examples of Cambrian Fossils
• Paleomap Project
• Report on the web on Amthor and others from Geology vol. 31
• Weird Life on the Mats

Ryan Gosling
Gosling at the 2011 Cannes Film Festival
Born	Ryan Thomas Gosling (1980-11-12) November 12, 1980 (age 31) London, Ontario, Canada
Occupation	Actor, musician, restaurant owner
Years active	1993–present

Ryan Thomas Gosling (born November 12, 1980) is a Canadian actor and musician. He began his career as a child star on the Disney Channel's Mickey Mouse Club (1993–95) and went on to appear in other family entertainment programs including Are You Afraid of the Dark? (1995), Goosebumps (1996), Breaker High (1997–98) and Young Hercules (1998–99). His first serious role was as a Jewish neo-Nazi in The Believer (2001), and he then built a reputation for playing misfits in independent films such as Murder by Numbers (2002), The Slaughter Rule (2002), The United States of Leland (2003) and Stay (2005).

Gosling came to the attention of a wider audience in 2004 with a leading role in the romantic drama The Notebook, for which he won four Teen Choice Awards and an MTV Movie Award. His performance as a drug-addicted teacher in Half Nelson (2006) was nominated for an Academy Award and his performance as a socially inept loner in Lars and the Real Girl (2007) was nominated for a Golden Globe Award. In 2007, he starred in the courtroom thriller Fracture.

After a three-year acting hiatus, Gosling starred in both Blue Valentine and All Good Things in 2010. The former performance as a frazzled husband earned him a second Golden Globe nomination. 2011 proved to be a landmark year for the actor as he appeared in three mainstream films – the romantic comedy Crazy, Stupid, Love, the thriller Drive and the political drama The Ides of March – and received two Golden Globe nominations. He is due to appear in five upcoming films: the period crime feature Gangster Squad, the generational drama The Place Beyond the Pines, the revenge drama Only God Forgives, an as-yet-untitled Terrence Malick film, and a remake of the sci-fi film Logan's Run.

Gosling's band, Dead Man's Bones, released their self-titled debut album and toured North America in 2009. He is a co-owner of Tagine, a Moroccan restaurant in Beverly Hills, California. He is a supporter of PETA, Invisible Children and the Enough Project and has travelled to Chad, Uganda and eastern Congo to raise awareness about conflicts in the region.

Early life[link]

Ryan Thomas Gosling was born in London, Ontario.^[1] He is the son of Thomas Gosling, a traveling salesman for a paper mill,^[2] and Donna, a secretary who qualified as a high school teacher in 2011.^[3] Because of his father's work, they "moved around a lot"^[2] and Gosling lived in both Cornwall, Ontario,^[4] and Burlington, Ontario.^[5] His parents were Mormons,^[6] and Gosling has said that the religion influenced every aspect of their lives.^[7] His parents divorced when he was a child and he and his older sister Mandi lived with their mother,^[8] an experience Gosling has credited with programming him "to think like a girl".^[9]

Gosling was educated at Gladstone Public School,^[10] Cornwall Collegiate and Vocational School and Lester B. Pearson High School.^[11] He "hated" being a child,^[7][12] was bullied in elementary school^[13] and had no friends until he was "14 or 15".^[14][15] In Grade 1, having been heavily influenced by the film First Blood, he took steak knives to school and threw them at other children during recess. This incident led to a suspension.^[12] He was unable to read^[16] and was diagnosed with ADHD, prescribed Ritalin, and placed in a class for special needs students.^[17] Consequently, his mother quit her job and homeschooled him for a year.^[17] Gosling has said that homeschooling gave him "a sense of autonomy that I've never really lost".^[7]

Gosling performed from an early age. He and his sister sang together at weddings; he performed with Elvis Perry, his uncle's Elvis Presley tribute act,^[18] and was involved with a local ballet company.^[19] Performing boosted his self-confidence as it was the only thing he received praise for.^[15] He developed an idiosyncratic accent because, as a child, he thought having a Canadian accent didn't sound "tough". He began to model his accent on that of Marlon Brando.^[20] He dropped out of high school at the age of seventeen to focus on his acting career.^[21]

Acting career[link]

Child star (1993–1999)[link]

In 1993, at the age of twelve, Gosling attended an open audition in Montreal for a revival of Disney Channel's Mickey Mouse Club.^[22] He was given a two-year contract as a mouseketeer and moved to Orlando, Florida.^[21] He appeared on-screen infrequently because other children were considered more talented.^[23] Nonetheless, he has described the job as the greatest two years of his life.^[21] Fellow cast members included Justin Timberlake, Britney Spears and Christina Aguilera and Gosling has credited the experience with instilling in them "this great sense of focus."^[24] He became particularly close friends with Timberlake and they lived together for six months during the second year of the show. Timberlake's mother became Gosling's legal guardian after his mother returned to Canada for work reasons.^[25] Gosling has said that, while they are no longer in touch, they are still supportive of each other.^[24]

Following the show's cancellation in 1995, Gosling returned to Canada and continued to appear in family entertainment television series including Are You Afraid of the Dark? (1995),^[26] Goosebumps (1996)^[27] and Breaker High (1997–98).^[28] At the age of eighteen, he moved to New Zealand to film the Fox Kids adventure series Young Hercules (1998–99).^[29] While he initially enjoyed working on the series, he began to long for an opportunity to play a variety of characters and decided not to accept any more television work.^[21]

Move to independent film (2000–2003)[link]

At the age of nineteen, Gosling decided to move into "serious film". He was dropped by his agent and initially found it difficult to secure work because of the "stigma" attached to children's television.^[30] After a supporting role in the football drama Remember the Titans, Gosling secured a lead role as a young Jewish neo-Nazi in 2001's The Believer. Director Henry Bean has said he cast Gosling because his Mormon upbringing helped him understand the isolation of Judaism.^[31] Kevin Thomas of the Los Angeles Times praised an "electrifying and terrifyingly convincing" performance^[32] while Todd McCarthy of Variety felt his "dynamite performance" could "scarcely have been better".^[33] The film won the Grand Jury Prize at the Sundance Film Festival^[34] and Gosling has described it as "the film that kind of gift-wrapped for me the career that I have now."^[18] Because of the controversial nature of the film, it was difficult to secure financial backing for a full theatrical release^[35] and the film was instead broadcast on Showtime.^[35] The film was a commercial failure, grossing just $416,925 worldwide from a production budget of $1.5 million.^[36]

In 2002's Murder by Numbers,^[37] Gosling and Michael Pitt portrayed a pair of high school seniors who believe they can commit the perfect murder. Sandra Bullock starred as a detective tasked with investigating the crime. Lisa Schwarzbaum of Entertainment Weekly described him as "a phenomenal talent even in junk like this"^[38] while Todd McCarthy of Variety felt that the "strong and "charismatic" young actors were "let down by the screenplay".^[39] The film was a minor commercial success, grossing $56 million worldwide from a production budget of $50 million.^[40] His second screen appearance of 2002 was in The Slaughter Rule which explores the relationship between a high school football player and his troubled coach in rural Montana. Gosling has said that the opportunity to work with David Morse made him "a better actor".^[41] Stephen Holden of The New York Times described Gosling as "major star material" with a "rawness and an intensity that recall the young Matt Dillon"^[42] while Manohla Dargis of the Los Angeles Times was won over by his "raw talent".^[43] The film was released in just three US theaters and grossed $13,411.^[44]

In 2003, Gosling starred in The United States of Leland as a teenager imprisoned for the murder of a disabled boy. He was drawn to the role because it was unusual to find a character that was "emotionally disconnected for the whole film."^[45] Roger Ebert of the Chicago Sun-Times felt that the "gifted actor does everything that can be done with Leland, but the character comes from a writer's conceits, not from life."^[46] A.O. Scott of The New York Times noted that he "struggles to rescue Leland from the clutches of cliché"^[47] while David Rooney of Variety felt that his "one-note, blankly disturbed act has none of the magnetic edge of his breakthrough work in The Believer".^[48] The film grossed $343,847 in the United States and was not released overseas.^[49]

[edit] The Notebook and Half Nelson (2004–2009)

Gosling came to the attention of a mainstream audience in 2004 after starring opposite fellow Canadian Rachel McAdams in the romantic drama The Notebook.^[50] Gosling sought to imbue his character with "quiet strength" and was inspired by the performance of Sam Shepard in Days of Heaven.^[51] Filming took place in Charleston, South Carolina in late 2002 and early 2003.^[52] Although Gosling and McAdams became romantically involved in 2005, they had a combative relationship on set.^[53] "We inspired the worst in each other," Gosling has said. "It was a strange experience, making a love story and not getting along with your co-star in any way."^[54] At one point, Gosling asked director Nick Cassavetes to "bring somebody else in for my off-camera shot" because he felt McAdams was uncooperative.^[53] The New York Times praised the "spontaneous and combustible" performances of the two leads and noted that, "against your better judgment, you root for the pair to beat the odds against them."^[55] Desson Thomson of The Washington Post praised Gosling's "beguiling unaffectedness" and noted that "it's hard not to like these two or begrudge them a great love together".^[56] The film grossed over $115 million worldwide and, with adjustments for inflation, it remains the most commercially successful film of Gosling's career as of 2012.^[57] Gosling won four Teen Choice Awards^[58] and an MTV Movie Award.^[59] Entertainment Weekly has said that the movie contains the All-Time Best Movie Kiss^[60] while the Los Angeles Times has included a scene from the film in a list of the 50 Classic Movie Kisses.^[61] The Notebook has appeared on many Most Romantic Movies lists.^{[62][63][64][65]}

Gosling at the 2007 Toronto International Film Festival

In 2005, Gosling appeared as a disturbed young art student in Stay, a psychological thriller co-starring Naomi Watts and Ewan McGregor. In an uncomplimentary review of the film, Manohla Dargis of The New York Times said that Gosling "like his fans, deserves better."^[66] Todd McCarthy of Variety felt that the "capable" McGregor and Gosling "deliver nothing new from what they've shown before".^[67] The film grossed $8 million worldwide.^[68] Gosling was unfazed by the negative reaction: "I had a kid come up to me on the street, 10 years old, and he says, ‘Are you that guy from Stay? What the f--- was that movie about?’ I think that's great. I'm just as proud if someone says, ‘Hey, you made me sick in that movie,’ as if they say I made them cry.”^[69]

Gosling next starred in 2006's Half Nelson as a drug-addicted junior high school teacher who forms a bond with a young student. To prepare for the role, Gosling moved to New York for one month before shooting began. He lived in a small apartment in Brooklyn and spent time shadowing an eighth grade teacher.^[70] Kenneth Turan of the Los Angeles Times described "a mesmerizing performance ... that shows the kind of deep understanding of character few actors manage."^[71] Ruthe Stein of the San Francisco Chronicle drew comparisons with Marlon Brando and declared that "nobody who cares about great acting will want to miss his performance".^[72] Roger Ebert felt the performance "proves he's one of the finest actors working in contemporary movies."^[73] He was nominated for an Academy Award.^[16] The film grossed $4 million at the worldwide box office.^[74]

Gosling played an introvert who falls in love with a sex doll in the gently comedic 2007 film Lars and the Real Girl. He drew inspiration from James Stewart's performance in Harvey.^[75] Roger Ebert felt "a film about a life-sized love doll" had been turned into "a life-affirming statement of hope" because of "a performance by Ryan Gosling that says things that cannot be said".^[76] Ann Hornaday of The Washington Post described his performance as "a small miracle ... because he changes and grows so imperceptibly before our eyes."^[77] However, Manohla Dargis of The New York Times felt "the performance is a rare miscalculation in a mostly brilliant career."^[78] He was nominated for a Golden Globe Award for Best Actor - Motion Picture Musical or Comedy.^[79] The film was a box office failure, failing to recoup its $12 million production budget.^[80]

Gosling starred opposite Anthony Hopkins in the 2007 courtroom thriller Fracture. He originally turned down the role, but changed his mind when Hopkins signed on.^[81] He spent time shadowing lawyers and observing courtroom proceedings in preparation for the role.^[82] Claudia Puig of USA Today declared that "watching a veteran like Hopkins verbally joust with one of the best young actors in Hollywood is worth the price of admission".^[83] Manohla Dargis of The New York Times felt it was a treat to watch "the spectacle of that crafty scene stealer Anthony Hopkins mixing it up with that equally cunning screen nibbler Ryan Gosling ... Each actor is playing a pulp type rather than a fully formed individual, but both fill in the blanks with an alchemical mix of professional and personal charisma."^[84] The film grossed over $91 million worldwide.^[85]

Gosling was due to begin filming The Lovely Bones in 2007. However, he left the production two days before filming began because of "creative differences" and was replaced by Mark Wahlberg.^[86] Gosling had been cast as the father of the murdered teenage girl and initially felt he was too young for the role. The director Peter Jackson and the producer Fran Walsh persuaded him that he could be aged with hair and make-up changes.^[87] Before shooting began, Gosling gained 60 pounds in weight and grew a beard in order to appear older.^[87] Walsh then "began to feel he was not right. It was our blindness, the desire to make it work no matter what."^[87] Gosling later said, ""We didn't talk very much during the preproduction process, which was the problem ... I just showed up on set, and I had gotten it wrong. Then I was fat and unemployed."^[87] He has said the experience was "an important realisation for me: not to let your ego get involved. It's OK to be too young for a role."^[88]