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
editThe 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
editCenozoic land mammal ages
edit- Saintaugustinean: Lower boundary 0.004 Ma. Upper boundary Present.[5]
- Santarosean: Lower boundary 0.014 Ma. Upper boundary 0.004 Ma.[5]
- Rancholabrean: Lower boundary 0.21 Ma. Upper boundary 0.014 Ma.[5]
- Irvingtonian: Lower boundary 1.4 Ma. Upper boundary 0.21 Ma.[5]
- Blancan: Lower boundary 4.7 Ma. Upper boundary 1.4 Ma.[5]
- Hemphillian: Lower boundary 9.4 Ma. Upper boundary 4.7 Ma.[5]
- Clarendonian: Lower boundary 12.5 Ma. Upper boundary 9.4 Ma.[5]
- Barstovian: Lower boundary 16.3 Ma. Upper boundary 12.5 Ma.[5]
- Hemingfordian: Lower boundary 18.5 Ma. Upper boundary 16.3 Ma.[5]
- Arikareean: Lower boundary 29.5 Ma. Upper boundary 18.5 Ma.[5]
- Whitneyan: Lower boundary 31.8 Ma. Upper boundary 29.5 Ma.[5]
- Orellan: Lower boundary 33.9 Ma. Upper boundary 31.8 Ma.[5]
- Chadronian: Lower boundary 37 Ma. Upper boundary 33.9 Ma.[5]
- Duchesnean: Lower boundary 39.7 Ma. Upper boundary 37 Ma.[5]
- Uintan: Lower boundary 46.2 Ma. Upper boundary 39.7 Ma.[5]
- Bridgerian: Lower boundary 50.5 Ma. Upper boundary 46.2 Ma.[5]
- Wasatchian: Lower boundary 54.9 Ma. Upper boundary 50.5 Ma.[5]
- Clarkforkian: Lower boundary 56.2 Ma. Upper boundary 54.9 Ma.[5]
- Tiffanian: Lower boundary 60.9 Ma. Upper boundary 56.2 Ma.[5]
- Torrejonian: Lower boundary 63.8 Ma. Upper boundary 60.9 Ma.[5]
- Puercan: Lower boundary 66 Ma. Upper boundary 63.8 Ma.[5]
Cretaceous land vertebrate ages
edit- Lancian: Lower boundary 67 Ma. Upper boundary 66 Ma.[7]
- Edmontonian: Lower boundary 73 Ma. Upper boundary 67 Ma.[7]
- Kirtlandian: Lower boundary 75 Ma. Upper boundary 73 Ma.[7]
- Judithian: Lower boundary 79 Ma. Upper boundary 75 Ma.[7]
- Wahweapian: Lower boundary 82 Ma. Upper boundary 79 Ma.[8]
- Aquilian: Lower boundary 84 Ma. Upper boundary 82 Ma.[7]
Other continental ages
editSee also
editReferences
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 978-0520053922.
- ^ 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.
- ^ a b c d e f g h i j k l m n o p q r s t u v w 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 9780231503785.
- ^ a b c d e f 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.
- ^ 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.