Terciær

Terciár is a term used in geology and related disciplines to denote the Tertiary period of the geologic timescale. The word derives from Latin tertius, meaning “third,” reflecting its historical position between the Secondary (Mesozoic) and Quaternary divisions. In contemporary formal usage, the label Tertiary is largely deprecated in favor of a twofold and threefold subdivision: Paleogene, Neogene, and, above them, Quaternary.

Geochronologically, the Tertiary spans roughly from 66 million years ago (the end of the Cretaceous) to about 2.58 million years ago. It is commonly subdivided into the Paleogene (66–23.03 Ma) and Neogene (23.03–2.58 Ma). The Quaternary, which follows, covers the most recent 2.58 million years up to the present. This organization reflects advances in stratigraphy and radiometric dating and provides a more precise framework for correlating events across regions.

During the Terciár, the Earth experienced significant evolutionary radiations, particularly among mammals and birds, and the expansion of modern plant groups. Global climate gradually cooled from the warm early Cenozoic to cooler, more variable conditions, culminating in the Quaternary glaciations. Tectonic processes continued to reshape continents, influencing regional climates and biogeography.

In Romanian scientific and educational texts, terciár is commonly used to refer to this historic interval, though many contemporary sources prefer Paleogene and Neogene for formal precision. The term remains encountered in older literature and in broader discussions of the Cenozoic. See also: Geological time scale, Cenozoic, Paleogene, Neogene, Quaternary.