Tertiary is the former term for the geologic period from 65 million to
2.58 million years ago, a timespan that occurs between the superseded
Secondary period and the Quaternary. The
Tertiary is no longer
recognized as a formal unit by the International Commission on
Stratigraphy, but the word is still widely used. The
traditional span of the
Tertiary has been divided between the
Neogene periods and extends to the first stage of the
Pleistocene Epoch, the
The period began with the demise of the non-avian dinosaurs in the
Paleogene extinction event, at the start of the Cenozoic
Era, and extended to the beginning of the
Quaternary glaciation at the
end of the
Historical use of the term
Tertiary was first used by Giovanni Arduino during the
mid-18th century. He classified geologic time into primitive (or
primary), secondary, and tertiary periods based on observations of
geology in northern Italy. Later a fourth period, the Quaternary,
In the early development of the study of geology, the periods were
thought by scriptural geologists to correspond to the Biblical
narrative, the rocks of the
Tertiary being thought to be associated
with the Great Flood.
Charles Lyell incorporated a
Tertiary Period into his own,
far more detailed system of classification. He subdivided the Tertiary
Period into four epochs according to the percentage of fossil mollusks
resembling modern species found in those strata. He used Greek names:
Eocene, Miocene, Older
Pliocene and Newer Pliocene.
Although these divisions seemed adequate for the region to which the
designations were originally applied (parts of the
Alps and plains of
Italy), when the same system was later extended to other parts of
Europe and to America, it proved to be inapplicable. Therefore, the
use of mollusks was abandoned from the definition and the epochs were
renamed and redefined.
^ K. M. Cohen; S. Finney; P. L. Gibbard (January 2013). "International
Chronostratigraphic Chart" (PDF). International Commission on
^ Ogg, James G.; Gradstein, F. M; Gradstein, Felix M. (2004). "1:
Chronostratigraphy: linking time and rock". A geologic time scale
2004. Cambridge, UK: Cambridge University Press. p. 45.
^ Gradstein, Felix M.; James G.Ogg; Martin van Kranendonk. "On the
Geologic Time Scale 2008" (PDF). International Commission on
Stratigraphy. p. 5. Retrieved 18 December 2013.
^ Vandenberghe, N.; F.J. Hilgen; R.P. Speijer (2012). "28: The
Paleogene Period". In Felix M. Gradstein; James G.; Ogg, Mark; D.
Schmitz; Gabi M. Ogg. The geologic time scale 2012 (1st ed.).
Amsterdam: Elsevier. p. 856. ISBN 978-0-44-459425-9.
^ Carl O. Dunbar, Historical Geology, 2nd ed. (1964), John Wiley &
Sons, New York, p. 352
^ Rudwick, M.J.S (1992): Scenes from Deep Time: Early Pictorial
Representations of the Prehistoric World, University of Chicago Press,
280 pages. Except from Google Books
Look up Tertiary or tertiary in Wiktionary, the free dictionary.
"Tertiary". Encyclopædia Britannica (11th ed.). 1911.