stratigraphic intervals (System) †Tertiary (66.0 - 2.58 Ma) (Subsystem) †Paleogene (66.0 - 23.03 Ma) see System Paleogene System (66.0 - 23.03 Ma) (Series) †Oligocene (33.9 - 23.03 Ma) (Subseries) †Upper 1 (Stage) †Chattian (27.82 - 23.03 Ma)