Tertiary

*Tertiary*
Tertiary
Chronology
−70 — – −65 — – −60 — – −55 — – −50 — – −45 — – −40 — – −35 — – −30 — – −25 — – −20 — – −15 — – −10 — – −5 — – 0 —	P ; h ; a ; n ; e ; r ; o ; z ; o ; i ; c Mesozoic C; e; n; o; z; o; i; c Quaternary Paleogene Neogene
	An approximate timescale of the Cenozoic. ; Axis scale: millions of years ago.;
Etymology
Name formality	Informal
Usage information
Celestial body	Earth
Regional usage	Regional(?)
Time scale(s) used	ICS Time Scale (formerly)
Formerly used by	ICS
Definition
Chronological unit	Period
Stratigraphic unit	System
Time span formality	Informal
Lower boundary definition	K-Pg extinction event
Lower boundary GSSP	None
Lower GSSP ratified	N/A
Upper boundary definition	Beginning of the Quaternary glaciation
Upper boundary GSSP	None
Upper GSSP ratified	N/A

Tertiary (/ˈtɜːr.ʃə.ri, ˈtɜːr.ʃiˌɛr.i/ TUR-shə-ree, TUR-shee-err-ee)^[1] is an obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic Era, and extended to the beginning of the Quaternary glaciation at the end of the Pliocene Epoch. The time span covered by the Tertiary has no exact equivalent in the current geologic time system, but it is essentially the merged Paleogene and Neogene periods, which are informally called the Early Tertiary and the Late Tertiary, respectively.

^ "tertiary [ tur-shee-er-ee, tur-shuh-ree ]". Dictionary.com Unabridged. Retrieved 5 January 2022.