North American land mammal age explained

The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when referring to the rock strata of that age) and were established using geographic place names where fossil materials were obtained.[1]

System

The North American land-mammal-age system was formalized in 1941 as a series of provincial land-mammal ages.[2] The system was the standard for correlations in the terrestrial Cenozoic record of North America and was the source for similar time scales dealing with other continents. The system was revised into a formal chronostratigraphic system. This approach is nominally justified by international stratigraphic codes; it holds that first appearances of individual species in particular sections are the only valid basis for naming and defining the land-mammal ages.

The basic unit of measure is the first/last boundary statement. This shows that the first appearance event of one taxon is known to predate the last appearance event of another. If two taxa are found in the same fossil quarry or at the same stratigraphic horizon, then their age-range zones overlap.[3]

The utility of the system led to its expansion into the Cretaceous (formalized 1986)[4] and the Holocene (formalized 2014).[5] These additions have been used in research related to the Cretaceous–Paleogene extinction event and the ensuing recovery,[6] and to the Anthropocene debate,[5] respectively. However, the ages that stretch into the Cretaceous are sometimes referred to as "North American land vertebrate ages" to reflect the fact that mammals, while still abundant, were not the dominant form of terrestrial life during the Mesozoic.

Ages

Cenozoic land mammal ages

Lower boundary 0.004 Ma. Upper boundary Present.[5]

Lower boundary 0.012 Ma. Upper boundary 0.004 Ma.[5]

Lower boundary 0.3 Ma. Upper boundary 0.012 Ma.[7]

Lower boundary 1.8 Ma. Upper boundary 0.3 Ma.[8] [9]

Lower boundary 4.9 Ma. Upper boundary 1.8 Ma.[10]

Lower boundary 10.3 Ma. Upper boundary 4.9 Ma.[11]

Lower boundary 13.6 Ma. Upper boundary 10.3 Ma.[12]

Lower boundary 15.97 Ma. Upper boundary 13.6 Ma.[13]

Lower boundary 20.43 Ma. Upper boundary 15.97 Ma.[14]

Lower boundary 30.8 Ma. Upper boundary 20.43 Ma.

Lower boundary 24.8 Ma. Upper boundary 20.43 Ma.[15]

Lower boundary 26.3 Ma. Upper boundary 24.8 Ma.[16]

Lower boundary 30.8 Ma. Upper boundary 26.3 Ma.[17]

Lower boundary 33.3 Ma. Upper boundary 30.8 Ma.[18]

Lower boundary 33.9 Ma. Upper boundary 33.3 Ma.[19]

Lower boundary 37.2 Ma. Upper boundary 33.9 Ma.[20]

Lower boundary 40.4 Ma. Upper boundary 37.2 Ma.[21]

Lower boundary 46.2 Ma. Upper boundary 40.4 Ma.[22]

Lower boundary 50.3 Ma. Upper boundary 46.2 Ma.[23]

Lower boundary 55.8 Ma. Upper boundary 50.3 Ma.[24]

Lower boundary 56.8 Ma. Upper boundary 55.8 Ma.[25]

Lower boundary 61.7 Ma. Upper boundary 56.8 Ma.[26]

Lower boundary 63.3 Ma. Upper boundary 61.7 Ma.[27]

Lower boundary 66.043 Ma. Upper boundary 63.3 Ma.[28]

Cretaceous land vertebrate ages

Lower boundary 67 Ma. Upper boundary 66 Ma.[29]

Lower boundary 73 Ma. Upper boundary 67 Ma.[29]

Lower boundary 75 Ma. Upper boundary 73 Ma.[29]

Lower boundary 79 Ma. Upper boundary 75 Ma.[29]

Lower boundary 82 Ma. Upper boundary 79 Ma.[30]

Lower boundary 84 Ma. Upper boundary 82 Ma.[29]

Other continental ages

See also

Notes and References

  1. Roberto Díaz Sibaja, Eduardo Jiménez Hidalgo, Ma. Luisa García Zepeda. Una nueva localidad fosilífera en Oaxaca (México) y el registro más austral de Bison latifrons: Implicaciones paleobiogeográficas, paleoecológicas y paleoambientales. Boletín de la Sociedad Geológica Mexicana. 70. 201–222.
  2. Wood. H. E.. Chaney. R. W.. Clark. J.. Colbert. E. H.. Jepsen. G.L.. Reeside. J. B.. Stock. C.. Nomenclature and correlation of the North American continental Tertiary. Geological Society of America Bulletin. 1941. 52. 1. 1–48. 10.1130/gsab-52-1. 1941GSAB...52....1W.
  3. Book: Woodburne. Michael O.. A prospectus of the North American Mammal Ages. Cenozoic mammals of North America : geochronology and biostratigraphy. 1987. University of California Press. Berkeley. 978-0520053922. 285 - 290.
  4. Lillegraven. J. A.. McKenna. M. C.. Fossil mammals from the" Mesaverde" Formation (late Cretaceous, Judithian) of the Bighorn and Wind River basins, Wyoming: with definitions of late Cretaceous North American land-mammal" ages". American Museum Novitates. 1986. 2840. 1–68.
  5. Barnosky. A. D.. Holmes. M.. Kircholtes. R.. Lindsey. E.. Maguire. K. C.. Poust. A. W.. Stegner. M. A.. Sunseri. J.. Swartz. B.. Swift. J.. Villavicencio. N. A.. Prelude to the Anthropocene: Two new North American land mammal ages (NALMAs). The Anthropocene Review. 1. 3. 2014. 225–242. 10.1177/2053019614547433. 128697655.
  6. Book: Woodburne. Michael O.. Mammalian Biochronology of the Latest Cretaceous. Late Cretaceous and Cenozoic mammals of North America biostratigraphy and geochronology. 2012. Columbia University Press. New York. 9780231503785. 21 - 43.
  7. Web site: Rancholabrean age/stage. fossilworks.org.
  8. Alroy. J.. New methods for quantifying macroevolutionary patterns and processes. Paleobiology. 26. 4. 2000. 707–733. 10.1666/0094-8373(2000)026<0707:NMFQMP>2.0.CO;2. 26470169 .
  9. Web site: Irvingtonian age/stage. fossilworks.org.
  10. Web site: Blancan age/stage. fossilworks.org.
  11. Web site: Hemphillian age/stage. fossilworks.org.
  12. Web site: Clarendonian age/stage. fossilworks.org.
  13. Web site: Barstovian age/stage. fossilworks.org.
  14. Web site: Hemingfordian age/stage. fossilworks.org.
  15. Web site: Harrisonian age/stage. fossilworks.org.
  16. Web site: Monroecreekian age/stage. fossilworks.org.
  17. Web site: Geringian age/stage. fossilworks.org.
  18. Web site: Whitneyan age/stage. fossilworks.org.
  19. Web site: Orellan age/stage. fossilworks.org.
  20. Web site: Chadronian age/stage. fossilworks.org.
  21. Web site: Duchesnean age/stage. fossilworks.org.
  22. Web site: Uintan age/stage. fossilworks.org.
  23. Web site: Bridgerian age/stage. fossilworks.org.
  24. Web site: Wasatchian age/stage. fossilworks.org.
  25. Web site: Clarkforkian age/stage. fossilworks.org.
  26. Web site: Tiffanian age/stage. fossilworks.org.
  27. Web site: Torrejonian age/stage. fossilworks.org.
  28. Web site: Puercan age/stage. fossilworks.org.
  29. Fowler. DW. Revised geochronology, correlation, and dinosaur stratigraphic ranges of the Santonian-Maastrichtian (Late Cretaceous) formations of the Western Interior of North America. 2017. PLOS ONE. 12. 11. e0188426. 10.1371/journal.pone.0188426. 29166406 . 5699823 . free .
  30. Ramezani. J.. Beveridge. T.L.. Rogers. R.. Eberth. D.. Roberts. E.. Calibrating the zenith of dinosaur diversity in the Campanian of the Western Interior Basin by CA-ID-TIMS U–Pb geochronology. 2022. Sci Rep. 12. 1 . 16026. 10.1038/s41598-022-19896-w. 36163377 . 9512893.

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