Arcto-Tertiary Geoflora

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The Arcto-Tertiary Geoflora[a] is a hypothesized floral assemblage that once covered the Northern Hemisphere, from roughly the late Mesozoic to mid Cenozoic Eras.

Origins[edit]

First proposed by the paleobotanists J.S. Gardner and C. Ettinghausen in 1879, the concept was intended to answer questions about the disjunct distribution of identical or closely related plant species: for instance, magnolia and tulip trees are native to both the Southeast United States and southern China and Indochina.,[2][3]

As envisioned, the ATG had a wide distribution when the global climate was much warmer than it is currently, a situation strengthened by the closer position of some of the continents in late Mesozoic to early Cenozoic times.,[4][5] With the onset of global cooling and the Ice Ages, the ranges of these tropical to subtropical species were left in isolated pockets of warmer climates.[6]

The southern, more tropical equivalent of the ATG was the Neotropical Tertiary Geoflora.[a][6]

Footnotes[edit]

  1. ^ a b This designation has as a part of it a term, 'Tertiary', that is now discouraged as a formal geochronological unit by the International Commission on Stratigraphy.[1]
  1. ^ Ogg, James G.; Gradstein, F. M; Gradstein, Felix M. (2004). A geologic time scale 2004. Cambridge, UK: Cambridge University Press. ISBN 0-521-78142-6. 
  2. ^ Delcourt, Hazel, Forests in Peril, (Blacksburg: The McDonald and Woodward Publishing Company, 2002), 31-2.
  3. ^ Dougal Dixon et al., The Atlas of Life on Earth, (New York: Barnes & Noble Books, 2001), 334-5.
  4. ^ Delcourt, 31.
  5. ^ Dixon et al., 334.
  6. ^ a b Delcourt, 32.

External links[edit]