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The Tertiary and the Quaternary are here to stay

¹ Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712; amos.salvador{at}mail.utexas.edu

Amos Salvador received his Ph.D. from Stanford University in 1950. After 30 years in the oil industry, the last 25 years with Exxon affiliates, he joined in 1980 the Department of Geological Sciences of the University of Texas at Austin, where he taught courses on stratigraphy, petroleum geology, and energy resources. He retired in 1993 and has since been engaged in research on several aspects of stratigraphic classification, terminology, and procedure and on energy consumption and supply. He is the editor of the second edition of the International Stratigraphic Guide and is coauthor of its abridged version.

In 1989 and 2000, the International Commission on Stratigraphy (ICS) published geologic time scales in which the term "Tertiary" had been eliminated. In the time scales published by the ICS in 2004, the term "Quaternary" was also eliminated, the Cenozoic shown as composed of two systems, the Paleogene and the Neogene, the Neogene extending to the present. Was there any logical basis for these changes?

A review of the geologic literature since 1980 (19 journals of extensive distribution and a considerable number of geologic maps, time scales, and stratigraphy textbooks as well as the GeoRef) clearly indicates that the Tertiary and the Quaternary have long been (and are now) in widespread use by geologists the world over, and that their use has not declined at all during the last 25 yr. They are very useful terms in geologic work, essential for clear communication among geologists. Paleogene and Neogene have received increasing use during the last 10 yr because they are also useful terms.

Quaternary is probably the stratigraphic term most frequently used in the geologic literature. Tertiary is used as the pre-Quaternary part of the Cenozoic by most geologists; some, however, prefer to use Paleogene and Neogene instead of Tertiary. But it should not be a question of either Tertiary or Paleogene and Neogene; all three are needed, as are Cenozoic, Paleocene, Eocene, Oligocene, Miocene, and Pliocene, to express various degrees of precision in stratigraphic assignation and dating. All should be recognized as units of a standard geologic time scale. Geologists should retain a choice of what they think better fits their needs. The preferred time scale, therefore, should have the Cenozoic Erathem comprising the Tertiary and Quaternary systems, and the Tertiary including the Paleogene and Neogene subsystems.

Past attempts to eliminate the Tertiary and Quaternary have been ignored. Recent attempts will not succeed either. The Tertiary and the Quaternary are here to stay, certainly as long as geologists continue to use them, as they have, and continue to oppose the ill-advised efforts to discard them from the geologic time scale.