Pliocene 23291 225200087 2008-07-12T12:35:41Z Wilson44691 4349401 [[WP:UNDO|Undid]] revision 225189495 by [[Special:Contributions/88.109.245.124|88.109.245.124]] ([[User talk:88.109.245.124|talk]]) <!--This article is in Commonwealth English--> {{Quaternary}} The '''Pliocene''' [[epoch (geology)|epoch]] (spelled '''Pleiocene''' in some older texts) is the period in the [[geologic timescale]] that extends from 5.332 million to 1.806 million years before present. The Pliocene is the second epoch of the [[Neogene]] period in the [[Cenozoic era]]. The Pliocene follows the [[Miocene]] epoch and is followed by the [[Pleistocene]] epoch. The Pliocene was named by [[Sir Charles Lyell]]. The name comes from the Greek words {{Polytonic|πλεῖον}} (''pleion'', "more") and {{Polytonic|καινός}} (''kainos'', "new") and means roughly "continuation of the recent", referring to the essentially modern marine [[mollusc]] faunas. As with other older geologic periods, the [[Stratum|geological strata]] that define the start and end are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The boundaries defining the onset of the Pliocene are not set at an easily identified worldwide event but rather at regional boundaries between the warmer Miocene and the relatively cooler Pliocene. The upper boundary was intended to be set at the start of the Pleistocene glaciations but is now considered to be set too late. Many geologists find the broader divisions into [[Paleogene]] and Neogene more useful. Astronomer Narciso Benítez of [[Johns Hopkins University]] and his team suggest that a [[supernova]] is a plausible but unproven candidate for the marine extinctions that characterize the Pliocene-Pleistocene boundary, by causing a significant breakdown of the [[ozone layer]]. ==Subdivisions== The Pliocene [[faunal stage]]s from youngest to oldest according to [[International Commission on Stratigraphy|ICS]] classification are: {| | [[Gelasian]] | (2.588–1.806 [[Mya (unit)|mya]]) (millions of years ago) |- | [[Piacenzian]] | (3.600–2.588 mya) |- | [[Zanclean]] | (5.332–3.600 mya) |} The first two stages make up the Late Pliocene, whereas the Zanclean is the only stage of the Early Pliocene. The Piacenzian may informally also be called "Middle Pliocene". For most of [[North America]], a different system ([[NALMA]]) is often used which overlaps epoch boundaries: {| | [[Blancan]] | (4.75–1.806 mya) |- | [[Hemphillian]] | (9–4.75 mya); includes most of the Late Miocene |} Other classification systems are used for [[California]], [[Australia]], [[Japan]] and [[New Zealand]]. ==Climate== Climates became cooler and drier, and seasonal, similar to modern climates. [[Ice sheet]]s grew on [[Antarctica]] during the Pliocene. The continent was ice-bound, entirely covered with perennial glaciers, by the start of the Pliocene.{{Fact|date=September 2007}} The formation of an Arctic ice cap around 3 mya is signaled by an abrupt shift in [[oxygen]] [[isotope]] ratios and [[ice-rafted]] cobbles in the North [[Atlantic]] and North [[Pacific ocean]] beds.<ref name="VanAndel1994">Van Andel (1994), p. 226.</ref> Mid-latitude [[glacier|glaciation]] was probably underway before the end of the epoch. The global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas.<ref>{{cite web |url=http://www.ucmp.berkeley.edu/tertiary/pli.html |title=The Pliocene epoch |accessdate=2008-03-25 |work=University of California Museum of Paleontology |date= }}</ref> ==Paleogeography== Continents continued to [[plate tectonics|drift]] toward their present positions, moving from positions possibly as far as 250 km from their present locations to positions only 70 km from their current locations. [[South America]] became linked to North America through the [[Isthmus of Panama]] during the Pliocene, bringing a nearly complete end to South America's distinctive [[Marsupialia|marsupial]] faunas. The formation of the Isthmus had major consequences on global temperatures, since warm equatorial ocean currents were cut off and an Atlantic cooling cycle began, with cold Arctic and Antarctic waters dropping temperatures in the now-isolated Atlantic Ocean. [[Africa]]'s collision with [[Europe]] formed the [[Mediterranean Sea]], cutting off the remnants of the [[Tethys Ocean]]. Sea level changes exposed the land-bridge between [[Alaska]] and Asia. Pliocene marine rocks are well exposed in the Mediterranean, [[India]], and [[China]]. Elsewhere, they are exposed largely near shores. ==Flora== The change to a cooler, dry, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species world-wide. [[Deciduous]] forests proliferated, [[coniferous]] forests and [[tundra]] covered much of the north, and [[grassland]]s spread on all continents (except Antarctica). Tropical forests were limited to a tight band around the equator, and in addition to dry [[savannahs]], [[deserts]] appeared in Asia and Africa. ==Fauna== Both marine and continental faunas were essentially modern, although continental faunas were a bit more primitive than today. The first recognizable [[hominin]]s, the [[australopithecine]]s, appeared in the Pliocene. The land mass collisions meant great migration and mixing of previously isolated species, such as in the [[Great American Interchange]]. [[Herbivores]] got bigger, as did specialized predators. <gallery> Image:Oliva sayana.jpg|[[Oliva sayana]], from the Pliocene deposits of Florida (United States) Image:CyprusPlioceneGastropod.JPG|Archaeogastropod from the Pliocene of [[Cyprus]]. A serpulid worm is attached. Image:Cladocora.jpg|The coral ''Cladocora'' from the Pliocene of [[Cyprus]]. </gallery> ===Mammals=== In North America, [[rodents]], large [[mastodont]]s and [[gomphothere]]s, and [[opossum]]s continued successfully, while hoofed animals ([[ungulate]]s) declined, with [[camel]], [[deer]] and [[horse]] all seeing populations recede. [[Rhinoceros|Rhinos]], [[tapirs]] and [[chalicothere]]s went extinct. [[Carnivores]] including the [[weasel]] family diversified, and [[dog]]s and fast-running hunting [[bear]]s did well. Ground [[sloth]]s, huge [[glyptodont]]s and [[armadillo]]s came north with the formation of the Isthmus of Panama. In [[Eurasia]] rodents did well, while [[primate]] distribution declined. [[Elephant]]s, [[gomphothere]]s and [[stegodon]]ts were successful in Asia, and [[hyrax]]es migrated north from Africa. [[Horse]] diversity declined, while tapirs and rhinos did fairly well. [[Cow]]s and [[antelope]]s were successful, and some camel species crossed into Asia from North America. [[Hyaenas]] and early [[saber-toothed cat]]s appeared, joining other predators including dogs, bears and weasels. {| border=0 cellspacing=2 cellpadding=0 width=350 align="right" style="font-size:smaller;" |+ style="font-size:larger;"| '''[[Human evolution]] during the Pliocene''' |- | <timeline> ImageSize = width:350 height:230 PlotArea = left:20 right:20 bottom:20 top:0 AlignBars = justify Colors = id:color1 value:rgb(1,1,0.7) # light yellow id:color2 value:rgb(0.7,0.7,1) # light blue id:color3 value:rgb(0.7,1,0.7) # light green id:color4 value:rgb(1,0.9216,0.3843) # 255/235/98 id:events value:rgb(1,0.3,1) # light purple Period = from:1806000 till:5332000 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:1000000 start:2000000 ScaleMinor = unit:year increment:250000 start:2000000 BarData = bar:Events bar:bar0 bar:bar1 bar:bar2 bar:bar3 bar:bar4 bar:bar5 bar:bar6 bar:bar7 bar:bar8 bar:bar9 bar:bar10 bar:bar11 bar:bar12 bar:bar13 bar:bar14 bar:bar15 bar:bar16 bar:bar17 bar:bar18 bar:bar19 PlotData= width:15 mark:(line,red) textcolor:black bar:Events color:events align:right shift:(-5,10) at:5000000 text:"Split between Homo and Pan~using molecular clock, about 7 Ma" width:7 mark:none color:events align:right shift:(-5,-4) bar:bar3 from:5200000 till:end at:5200000 text:Ar. kadabba bar:bar5 from:4200000 till:end at:4200000 text:Ar. ramidus align:left shift:(5,-4) bar:bar7 from:3900000 till:4400000 at:4400000 text:[[Australopithecus anamensis|A. anamensis]] bar:bar9 from:3000000 till:3900000 at:3900000 text:[[Australopithecus afarensis|A. afarensis]] bar:bar11 from:3000000 till:3500000 at:3500000 text:[[Australopithecus bahrelghazali|A. bahrelghazali]] bar:bar13 from:2400000 till:3300000 at:3300000 text:[[Australopithecus africanus|A. africanus]] bar:bar15 from:2000000 till:3000000 at:3000000 text:[[Australopithecus garhi|A. garhi]] bar:bar17 from:start till:2500000 at:2500000 text:[[Homo habilis|H. habilis]] bar:bar19 from:start till:1900000 at:1900000 text:[[Homo erectus|H. erectus]] bar:bar7 from:2500000 till:2700000 at:2700000 text:[[Paranthropus aethiopicus|P. aethiopicus]] bar:bar5 from:start till:2600000 at:2600000 text:[[Paranthropus boisei|P. boisei]] bar:bar3 from:start till:2000000 at:2000000 text:[[Paranthropus robustus|P. robustus]] mark:none bar:bar1 at:start text:[[Paranthropus|Genus Paranthropus]] bar:bar5 from:1806000 till:2735000 width:45 color:color1 bar:bar5 from:1856000 till:2665000 width:35 color:white bar:bar1 at:end align:right shift:(-5,-4) text:[[Ardipithecus|Genus Ardipithecus]] bar:bar4 from:4165000 till:5332000 width:29 color:color4 bar:bar4 from:4235000 till:5282000 width:19 color:white bar:bar17 at:end align:right shift:(-5,-6) text:[[Australopithecus|Genus Australopithecus]] bar:bar11 from:1965000 till:4435000 width:71 color:color2 bar:bar11 from:2035000 till:4365000 width:61 color:white bar:bar19 at:2535000 shift:(10,-10) text:[[Homo (genus)|Genus Homo]] bar:bar18 from:1806000 till:2535000 width:29 color:color3 bar:bar18 from:1856000 till:2465000 width:19 color:white TextData = pos:(59,14) text:"Years" </timeline> |} Africa was dominated by hoofed animals, and primates continued their evolution, with [[australopithecine]]s (some of the first [[Hominidae|hominid]]s) appearing in the late Pliocene. Rodents were successful, and elephant populations increased. Cows and antelopes continued diversification and overtaking [[pig]]s in numbers of species. Early [[giraffe]]s appeared, and camels migrated via Asia from North America. Horses and modern rhinos came onto the scene. Bears, dogs and weasels (originally from North America) joined cats, hyaenas and [[civet]]s as the African predators, forcing hyaenas to adapt as specialized scavengers. South America was invaded by North American species for the first time since the [[Cretaceous]], with North American rodents and primates mixing with southern forms. [[Litoptern]]s and the [[Notoungulata|notoungulate]]s, South American natives, did well. Small weasel-like carnivorous [[mustelid]]s and [[coati]]s migrated from the north. Grazing [[glyptodont]]s, browsing giant ground sloths and smaller armadillos did well. The marsupials remained the dominant Australian mammals, with herbivore forms including [[wombat]]s and [[kangaroo]]s, and the huge [[diprotodont]]s. Carnivorous marsupials continued hunting in the Pliocene, including [[dasyurid]]s, the dog-like [[thylacine]] and cat-like ''[[Thylacoleo]]''. The first rodents arrived, while bats did well, as did ocean-going [[whale]]s. The modern [[platypus]], a [[monotreme]], appeared. ===Birds=== [[Image:Titanis07DB.jpg|thumb|100px|right|''Titanis''.]] The predatory [[phorusrhacids]] were rare in this time; among the last was ''[[Titanis]]'', a large phorusrhacid that rivaled mammals as top predator. Its distinct feature was its claws, which had re-evolved for grasping prey, such as ''[[Hipparion]]''.{{Verify source|date=November 2007}} Other birds probably evolved at this time, some modern, some now extinct. ===Reptiles=== [[Alligator]]s and [[crocodile]]s died out in Europe as the climate cooled. [[Venomous snake]] genera continued to increase as more rodents and birds evolved. {{Expand|section|date=January 2007}} ==Oceans== Oceans continued to be relatively warm during the Pliocene, though they continued cooling. The [[Sea ice|Arctic ice cap]] formed, drying the climate and increasing cool shallow currents in the North Atlantic. Deep cold currents flowed from the Antarctic. The formation of the Isthmus of Panama about 3.5 million years ago cut off the final remnant of what was once essentially a circum-equatorial current that had existed since the Cretaceous and the early [[Cenozoic]]. This may have contributed to further cooling of the oceans worldwide. The Pliocene seas were alive with [[sea cow]]s, [[Pinniped|seal]]s and [[sea lion]]s. ==Supernovae== In 2002, astronomers discovered that roughly 2 million years ago, around the end of the Pliocene epoch, a group of bright [[Stellar classification|O and B stars]] called the [[Scorpius-Centaurus Association|Scorpius-Centaurus]] [[OB association]] passed within 150 light-years of Earth and that one or more [[supernova]]e may have occurred in this group at that time. Such a close explosion could have damaged the Earth's ozone layer and caused the extinction of some ocean life (consider that at its peak, a supernova of this size could have the same [[absolute magnitude]] as an entire galaxy of 200 billion stars).<ref name="Comins2005">Comins &amp; Kaufmann (2005), p. 359.</ref> ==See also== * [[List of fossil sites]] ''(with link directory)'' ==References== {{Reflist}} ==Further reading== <!-- Palaeogeography, Palaeoclimatology, Palaeoecology 213 (2004) 101–113 --> *{{cite book | first=Niel F. | last=Comins | coauthors=William J. Kaufmann III | year=2005 | title=Discovering the Universe | edition=7th edition | publisher=Susan Finnemore Brennan | location=New York, NY | isbn=0716775840}} *{{cite web |url=http://www.stratigraphy.org/gssp.htm |title=Overview of Global Boundary Stratotype Sections and Points (GSSP's) |accessdate=2006-04-30 |last=Ogg |first=Jim |coauthors= |date=June, 2004 |work= |publisher=}} *{{cite book |title=New Views on an Old Planet: a History of Global Change |edition=2nd edition |last=Van Andel |first=Tjeerd H. |authorlink= |coauthors= |year=1994 |publisher=Cambridge University Press |location=Cambridge |isbn=0521442435 |pages= }} ==External links== {{Commonscat|Pliocene}} *[http://www.bbc.co.uk/beasts/changing/pliocene/index.shtml BBC Changing Worlds: Pliocene] *[http://www.palaeos.com/Cenozoic/Pliocene/Pliocene.htm Palaeos Pliocene] *[http://www.pbs.org/wgbh/evolution/change/deeptime/pliocene.html PBS Change: Deep Time: Pliocene] *[http://www.ucmp.berkeley.edu/tertiary/pli.html UCMP Berkeley Pliocene Epoch Page] *[http://www.giss.nasa.gov/research/features/pliocene/ Mid-Pliocene Global Warming: NASA/GISS Climate Modeling] *[http://www.sciencenews.org/articles/20020202/fob5.asp "Supernova dealt deaths on Earth? Stellar blasts may have killed ancient marine life" ''Science News Online''] 2 February 2002 *[http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_129643.htm Possible Pliocene supernova] {{Neogene Footer}} {{Quaternary Footer}} [[Category:Pliocene| ]] [[ast:Pliocenu]] [[br:Pliosen]] [[ca:Pliocè]] [[cs:Pliocén]] [[da:Pliocæn]] [[de:Pliozän]] [[et:Pliotseen]] [[es:Plioceno]] [[eo:Plioceno]] [[fr:Pliocène]] [[ko:플리오세]] [[id:Pliosen]] [[it:Pliocene]] [[he:פליוקן]] [[lb:Pliozän]] [[lt:Pliocenas]] [[hu:Pliocén]] [[nl:Plioceen]] [[ja:鮮新世]] [[no:Pliocen]] [[nn:Pliocen]] [[nds:Pliozän]] [[pl:Pliocen]] [[pt:Plioceno]] [[ro:Pliocen]] [[ru:Плиоцен]] [[sk:Pliocén]] [[sl:Pliocen]] [[sh:Pliocen]] [[fi:Plioseeni]] [[sv:Pliocen]] [[vi:Thế Pliocen]] [[tr:Pliyosen Çağ]] [[uk:Пліоцен]] [[zh:上新世]]