Tertiary is the former name of a geological era extending from -65 to -2.6 million of years1.
The same geological period included the Paleogene system and ages of Miocene and Pliocene. It is part of the Cenozoic era , which also includes periods of the Pleistocene and Holocene (formerly grouped Quaternary).
This term is used for the first time by Giovanni Arduino in 1730 which classifies geological time in Primary, Secondary and Tertiary. A fourth period, the Quaternary will be added later. In 1828, Charles Lyell uses the term to use in his own much more detailed classification. It divides the Tertiary based on the percentage of shellfish resembling modern species found in geological strata. These divisions , locally appropriate land studied by Lyell, prove unworkable when they are extended to the rest of the world. Shellfish classification is abandoned and the Tertiary name.
