Пређи на садржај

Kredno–paleogeni događaj izumiranja — разлика између измена

С Википедије, слободне енциклопедије
Новија измена →
Садржај обрисан Садржај додат
ВизуелноВикитекст
.
(нема разлике)

Верзија на датум 14. октобар 2019. у 00:21

meteoroid entering the atmosphere with fireball
An artist's rendering of an asteroid a few kilometers across colliding with the Earth. Such an impact can release the equivalent energy of several million nuclear weapons detonating simultaneously.
rock hillside with rock striations
Badlands near Drumheller, Alberta, where erosion has exposed the K–Pg boundary
rock in museum with layering
A Wyoming rock with an intermediate claystone layer that contains 1000 times more iridium than the upper and lower layers. Picture taken at the San Diego Natural History Museum
Cretaceous Paleogene clay layer with finger pointing to boundary
Complex Cretaceous–Paleogene clay layer (gray) in the Geulhemmergroeve tunnels near Geulhem, The Netherlands. (Finger is below the actual Cretaceous–Paleogene boundary)

Kredno–paleogeni (K–Pg) događaj izumiranja,[а] takođe poznat kao Kredno–tercijarno (K–T) izumiranje,[б] was a sudden mass extinction of some three-quarters of the plant and animal species on Earth,[2][3][4] approximately 66 million years ago.[3] With the exception of some ectothermic species such as the leatherback sea turtle and crocodiles, no tetrapods weighing more than 25 kg (55 lb) survived.[5] It marked the end of the Cretaceous period and with it, the entire Mesozoic Era, opening the Cenozoic Era that continues today.

In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the metal iridium, which is rare in the Earth's crust, but abundant in asteroids.[6]

As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter Alvarez, it is now generally thought that the K–Pg extinction was caused by the impact of a massive comet or asteroid 10 to 15 km (6 to 9 mi) wide,[7][8] 66 million years ago,[3] which devastated the global environment, mainly through a lingering impact winter which halted photosynthesis in plants and plankton.[9][10] The impact hypothesis, also known as the Alvarez hypothesis, was bolstered by the discovery of the 180 km-wide (112 mi) Chicxulub crater in the Gulf of Mexico's Yucatán Peninsula in the early 1990s,[11] which provided conclusive evidence that the K–Pg boundary clay represented debris from an asteroid impact.[12] The fact that the extinctions occurred simultaneously provides strong evidence that they were caused by the asteroid.[12] A 2016 drilling project into the Chicxulub peak ring confirmed that the peak ring comprised granite ejected within minutes from deep in the earth, but contained hardly any gypsum, the usual sulfate-containing sea floor rock in the region: the gypsum would have vaporized and dispersed as an aerosol into the atmosphere, causing longer-term effects on the climate and food chain.

Other causal or contributing factors to the extinction may have been the Deccan Traps and other volcanic eruptions,[13][14] climate change, and sea level change.

A wide range of species perished in the K–Pg extinction, the best-known being the non-avian dinosaurs. It also destroyed a plethora of other terrestrial organisms, including some mammals, pterosaurs, birds,[15][16] lizards,[17] insects,[18][19] and plants.[20] In the oceans, the K–Pg extinction killed off plesiosaurs and the giant marine lizards (Mosasauridae) and devastated fish,[21] sharks, mollusks (especially ammonites, which became extinct), and many species of plankton. It is estimated that 75% or more of all species on Earth vanished.[22] Yet the extinction also provided evolutionary opportunities: in its wake, many groups underwent remarkable adaptive radiation—sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches. Mammals in particular diversified in the Paleogene,[23] evolving new forms such as horses, whales, bats, and primates. Birds,[24] fish,[25] and perhaps lizards[17] also radiated.

Napomene

  1. ^ The abbreviation is derived from the juxtaposition of K, the common abbreviation for the Cretaceous, which in turn originates from the correspondent German term Kreide, and Pg, which is the abbreviation for the Paleogene.
  2. ^ The former designation includes the term 'Tertiary' (abbreviated as T), which is now discouraged as a formal geochronological unit by the International Commission on Stratigraphy.[1]

Reference

  1. ^ Ogg, James G.; Gradstein, F. M; Gradstein, Felix M. (2004). A geologic time scale 2004. Cambridge, UK: Cambridge University Press. ISBN 978-0-521-78142-8. 
  2. ^ „International Chronostratigraphic Chart”. International Commission on Stratigraphy. 2015. Архивирано из оригинала 30. 5. 2014. г. Приступљено 29. 4. 2015. 
  3. ^ а б в Renne, Paul R.; Deino, Alan L.; Hilgen, Frederik J.; Kuiper, Klaudia F.; Mark, Darren F.; Mitchell, William S.; Morgan, Leah E.; Mundil, Roland; Smit, Jan (7. 2. 2013). „Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary” (PDF). Science. 339 (6120): 684—687. Bibcode:2013Sci...339..684R. PMID 23393261. doi:10.1126/science.1230492. 
  4. ^ Fortey, Richard (1999). Life: A Natural History of the First Four Billion Years of Life on Earth. Vintage. стр. 238—260. ISBN 978-0-375-70261-7. 
  5. ^ Muench, David; Muench, Marc; Gilders, Michelle A. (2000). Primal Forces. Portland: Graphic Arts Center Publishing. стр. 20. ISBN 978-1-55868-522-2. 
  6. ^ Schulte, Peter (5. 3. 2010). „The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary” (PDF). Science. 327 (5970): 1214—1218. Bibcode:2010Sci...327.1214S. JSTOR 40544375. PMID 20203042. doi:10.1126/science.1177265. 
  7. ^ Sleep, Norman H.; Lowe, Donald R. (9. 4. 2014). „Scientists reconstruct ancient impact that dwarfs dinosaur-extinction blast”. American Geophysical Union. Приступљено 30. 12. 2016. 
  8. ^ Amos, Jonathan (15. 5. 2017). „Dinosaur asteroid hit 'worst possible place'”. BBC News Online. Приступљено 16. 3. 2018. 
  9. ^ Alvarez, L W; Alvarez, W; Asaro, F; Michel, H V (1980). „Extraterrestrial cause for the Cretaceous–Tertiary extinction” (PDF). Science. 208 (4448): 1095—1108. Bibcode:1980Sci...208.1095A. PMID 17783054. doi:10.1126/science.208.4448.1095. 
  10. ^ Vellekoop, J.; Sluijs, A.; Smit, J.; et al. (мај 2014). „Rapid short-term cooling following the Chicxulub impact at the Cretaceous-Paleogene boundary”. Proc. Natl. Acad. Sci. U.S.A. 111 (21): 7537—41. Bibcode:2014PNAS..111.7537V. PMC 4040585 Слободан приступ. PMID 24821785. doi:10.1073/pnas.1319253111. 
  11. ^ Hildebrand, A. R.; Penfield, G. T.; et al. (1991). „Chicxulub crater: a possible Cretaceous/Tertiary boundary impact crater on the Yucatán peninsula, Mexico”. Geology. 19 (9): 867—871. Bibcode:1991Geo....19..867H. doi:10.1130/0091-7613(1991)019<0867:ccapct>2.3.co;2. 
  12. ^ а б Schulte, P.; et al. (5. 3. 2010). „The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary” (PDF). Science. 327 (5970): 1214—1218. Bibcode:2010Sci...327.1214S. PMID 20203042. doi:10.1126/science.1177265. 
  13. ^ Keller G (2012). „The Cretaceous–Tertiary Mass Extinction, Chicxulub Impact, and Deccan Volcanism. Earth and Life”. Ур.: Talent JA. Earth and Life: Global Biodiversity, Extinction Intervals and Biogeographic Perturbations Through Time. Springer. стр. 759—793. ISBN 978-90-481-3427-4. 
  14. ^ Bianca Bosker, "The Nastiest Feud in Science:A Princeton geologist has endured decades of ridicule for arguing that the fifth extinction was caused not by an asteroid but by a series of colossal volcanic eruptions. But she's reopened that debate." The Atlantic Monthly September 2018. https://www.theatlantic.com/magazine/archive/2018/09/dinosaur-extinction-debate/565769/
  15. ^ Longrich, Nicholas R.; Tokaryk, Tim; Field, Daniel J. (2011). „Mass extinction of birds at the Cretaceous–Paleogene (K–Pg) boundary”. Proceedings of the National Academy of Sciences. 108 (37): 15253—15257. Bibcode:2011PNAS..10815253L. PMC 3174646 Слободан приступ. PMID 21914849. doi:10.1073/pnas.1110395108. 
  16. ^ „Primitive birds shared dinosaurs' fate”. Science Daily. 20. 9. 2011. Приступљено 20. 9. 2011. 
  17. ^ а б Longrich, N. R.; Bhullar, B.-A. S.; Gauthier, J. A. (децембар 2012). „Mass extinction of lizards and snakes at the Cretaceous-Paleogene boundary”. Proc. Natl. Acad. Sci. U.S.A. 109 (52): 21396—401. Bibcode:2012PNAS..10921396L. PMC 3535637 Слободан приступ. PMID 23236177. doi:10.1073/pnas.1211526110. 
  18. ^ Labandeira CC; Johnson KR; et al. (2002). „Preliminary assessment of insect herbivory across the Cretaceous-Tertiary boundary: major extinction and minimum rebound”. Ур.: Hartman JH; Johnson KR; Nichols DJ. The Hell Creek formation and the Cretaceous-Tertiary boundary in the northern Great Plains: An integrated continental record of the end of the Cretaceous. Geological Society of America. стр. 297—327. ISBN 978-0-8137-2361-7. 
  19. ^ Rehan, Sandra M.; Leys, Remko; Schwarz, Michael P. (2013). „First evidence for a massive extinction event affecting bees close to the K-T boundary”. PLOS ONE. 8 (10): e76683. Bibcode:2013PLoSO...876683R. ISSN 1932-6203. PMC 3806776 Слободан приступ. PMID 24194843. doi:10.1371/journal.pone.0076683. 
  20. ^ Nichols, D. J.; Johnson, K. R. (2008). Plants and the K–T Boundary. Cambridge, UK: Cambridge University Press. 
  21. ^ Friedman M (2009). „Ecomorphological selectivity among marine teleost fishes during the end-Cretaceous extinction”. Proceedings of the National Academy of Sciences. Washington, DC. 106 (13): 5218—5223. Bibcode:2009PNAS..106.5218F. PMC 2664034 Слободан приступ. PMID 19276106. doi:10.1073/pnas.0808468106. 
  22. ^ Jablonski, D.; Chaloner, W. G. (1994). „Extinctions in the fossil record (and discussion)”. Philosophical Transactions of the Royal Society of London B. 344 (1307): 11—17. doi:10.1098/rstb.1994.0045. 
  23. ^ Alroy J (1999). „The fossil record of North American Mammals: evidence for a Palaeocene evolutionary radiation”. Systematic Biology. 48 (1): 107—118. PMID 12078635. doi:10.1080/106351599260472. 
  24. ^ Feduccia A (1995). „Explosive evolution in Tertiary birds and mammals”. Science. 267 (5198): 637—638. Bibcode:1995Sci...267..637F. PMID 17745839. doi:10.1126/science.267.5198.637. 
  25. ^ Friedman M (2010). „Explosive morphological diversification of spiny-finned teleost fishes in the aftermath of the end-Cretaceous extinction”. Proceedings of the Royal Society B. 277 (1688): 1675—1683. PMC 2871855 Слободан приступ. PMID 20133356. doi:10.1098/rspb.2009.2177. 

Literatura

Spoljašnje veze

Kredno–paleogeni događaj izumiranja на Викимедијиној остави.
Преузето из „https://sr.wikipedia.org/w/index.php?title=Kredno–paleogeni_događaj_izumiranja&oldid=22237992”