Paleogene geochronology

The Eocene ( ) is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era.

The Oligocene is a geologic epoch of the Paleogene Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The name Oligocene was coined in 1854 by the German paleontologist Heinrich Ernst Beyrich from his studies of marine beds in Belgium and Germany. The name comes from Ancient Greek ὀλίγος (olígos), , and καινός (kainós), , and refers to the sparsity of extant forms of molluscs. The Olig

The Paleocene ( ), or Palaeocene, is a geological epoch that lasted from about 66 to 56 Ma (million years ago). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name comes from Ancient Greek παλαιός (palaiós), meaning "old", and καινός (kainós), meaning "new", translating to "the old part of the Eocene".