North American land mammal age
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
[edit]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.[7]
Ages
[edit]Some land mammal ages have recognized biochronological subdivisions.[8]
The lower boundary of each age or subdivision is the upper boundary of the next lower age or subdivision.
| Age | Subdivision | Upper boundary | Polarity chron(s) |
|---|---|---|---|
| Cenozoic land mammal ages | |||
| Saintaugustinean | Present[5] | C1n | |
| Santarosean | 0.0004 Ma (1540 CE)[5] | C1n | |
| Rancholabrean | 0.014 Ma.[5] | C1n | |
| Irvingtonian | 0.21 Ma.[5] | C1r.2r – C1n | |
| Blancan | 1.4 Ma.[5] | C3n – C1r.2r | |
| Hemphillian | 4.7 Ma.[5] | C4An – C3n | |
| Clarendonian | 9.4 Ma.[5] | C5Ar – C4An | |
| Barstovian | 12.5 Ma.[5] | C5Cn – C5Ar | |
| Hemingfordian | 16.3 Ma.[5] | C5Er – C5Cn | |
| Arikareean | 18.5 Ma.[5] | C11n – C5Er | |
| Whitneyan | Wh2 | 30.0 Ma.[8] | C12r – C11n |
| Wh1 | 31.4 Ma.[8] | C12r | |
| Orellan | Or4 | 32.0 Ma.[8] | C12r |
| Or3 | 32.5 Ma.[8] | C13n – C12r | |
| Or2 | 33.1 Ma.[8] | C13n | |
| Or1 | 33.4 Ma.[8] | C13r – C13n | |
| Chadronian | Ch4 | 33.7 Ma.[8] | C15n – C13r |
| Ch3 | 34.7 Ma.[8] | C16n – C15n | |
| Ch2 | 35.7 Ma.[8] | C16r – C16n | |
| Ch1 | 36.5 Ma.[8] | C17n – C16r | |
| Duchesnean | 37.0 Ma.[9] | C19n – C17n | |
| Uintan | Ui3 | 41.4 Ma.[9] | C20n – C19n |
| Ui2 | 42.8 Ma.[8] | C20r – C20n | |
| Ui1 | 45.7 Ma.[8] | C21n – C20r | |
| Bridgerian | Br3 | 46.3 Ma.[8] | C21r – C21n |
| Br2 | 47.0 Ma.[8] | C22n – C21r | |
| Br1b | 49.2 Ma.[8] | C22r – C22n | |
| Br1a | 50.0 Ma.[8] | C23r – C22r | |
| Wasatchian | Wa7 | 50.1 Ma.[8] | C24n.1r – C23r |
| Wa6 | 52.4 Ma.[8] | C24n.3n – C24n.1r | |
| Wa5 | 53.0 Ma.[8] | C24r – C24n.3n | |
| Wa4 | 53.4 Ma.[8] | C24r | |
| Wa3 | 54.1 Ma.[8] | C24r | |
| Wa2 | 54.4 Ma.[8] | C24r | |
| Wa1 | 54.7 Ma.[8] | C24r | |
| Wa0 | 54.9 Ma.[8] | C24r | |
| Clarkforkian | 56.0 Ma.[10] | C25n – C24r | |
| Tiffanian | 57.5 Ma.[10] | C26r – C25n | |
| Torrejonian | 62.3 Ma.[11] | C28r – C27n | |
| Puercan | 65.1 Ma.[12] | C29r – C28r | |
| Cretaceous land vertebrate ages | |||
| Lancian | 66 Ma.[7] | ||
| "Edmontonian" | 67 Ma.[7] | ||
| Kirtlandian | 73 Ma.[7] | ||
| Judithian | 75 Ma.[7] | ||
| Wahweapian | 79 Ma.[13] | ||
| Aquilian (Lower boundary 84 Ma) | 82 Ma.[7] | ||
Other continental ages
[edit]See also
[edit]References
[edit]- ↑ 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" (PDF). Boletín de la Sociedad Geológica Mexicana. 70: 201–222.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ Wood, H. E.; Chaney, R. W.; Clark, J.; Colbert, E. H.; Jepsen, G.L.; Reeside, J. B.; Stock, C. (1941). "Nomenclature and correlation of the North American continental Tertiary". Geological Society of America Bulletin. 52 (1): 1–48. Bibcode:1941GSAB...52....1W. doi:10.1130/gsab-52-1.
- ↑ Woodburne, Michael O., ed. (1987). "A prospectus of the North American Mammal Ages". Cenozoic mammals of North America: geochronology and biostratigraphy. Berkeley: University of California Press. pp. 285–290. ISBN 978-0-520-05392-2.
- ↑ Lillegraven, J. A.; McKenna, M. C. (1986). "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 (2840): 1–68.
- 1 2 3 4 5 6 7 8 9 10 11 12 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. (2014). "Prelude to the Anthropocene: Two new North American land mammal ages (NALMAs)". The Anthropocene Review. 1 (3): 225–242. doi:10.1177/2053019614547433. S2CID 128697655.
- ↑ Woodburne, Michael O., ed. (2012). "Mammalian Biochronology of the Latest Cretaceous". Late Cretaceous and Cenozoic mammals of North America biostratigraphy and geochronology. New York: Columbia University Press. pp. 21–43. ISBN 978-0-231-50378-5.
- 1 2 3 4 5 6 Fowler, DW (2017). "Revised geochronology, correlation, and dinosaur stratigraphic ranges of the Santonian-Maastrichtian (Late Cretaceous) formations of the Western Interior of North America". PLOS ONE. 12 (11) e0188426. doi:10.1371/journal.pone.0188426. PMC 5699823. PMID 29166406.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Hodnett, John-Paul M.; Welsh, Edward T.; Santucci, Vincent L.; Tweet, Justin S. (2022). "A Middle Eocene brontothere (Mammalia; Perissodactyla; Brontotheriidae) from Yellowstone National Park, Wyoming". FOSSIL RECORD 8. New Mexico Museum of Natural History and Science. p. 211.
- 1 2 Kelly, T.S.; Murphey, P.C.; Walsh, S.L. (2012). "New records of small mammals from the middle Eocene Duchesne River Formation, Utah, and their implications for the Uintan–Duchesnean North American Land Mammal Age transition." Paludicola 8: 208–251.
- 1 2 Anemone, Robert L.; Jones, Matthew F.; Van Regenmorter, John; Beard, K. Christopher (2024-05-03). "A latest Paleocene mammal fauna from the Great Divide Basin in southern Wyoming and a revised biozonation of the Clarkforkian land mammal age". Journal of Vertebrate Paleontology. 44 (3). doi:10.1080/02724634.2024.2424139. ISSN 0272-4634.
- ↑ Speijer, R.P.; Pälike, H.; Hollis, C.J.; Hooker, J.J.; Ogg, J.G. (2020), "The Paleogene Period", Geologic Time Scale 2020, Elsevier, pp. 1087–1140, doi:10.1016/B978-0-12-824360-2.00028-0, ISBN 978-0-12-824360-2, retrieved 2026-08-30
{{citation}}: CS1 maint: work parameter with ISBN (link) - ↑ Sprain, C. J.; Renne, P. R.; Wilson, G. P.; Clemens, W. A. (2015-03-01). "High-resolution chronostratigraphy of the terrestrial Cretaceous-Paleogene transition and recovery interval in the Hell Creek region, Montana". Geological Society of America Bulletin. 127 (3–4): 393–409. doi:10.1130/B31076.1. ISSN 0016-7606.
- ↑ Ramezani, J.; Beveridge, T.L.; Rogers, R.; Eberth, D.; Roberts, E. (2022). "Calibrating the zenith of dinosaur diversity in the Campanian of the Western Interior Basin by CA-ID-TIMS U–Pb geochronology". Sci Rep. 12 (1): 16026. doi:10.1038/s41598-022-19896-w. PMC 9512893. PMID 36163377.