Uintan

The Uintan North American Stage is the North American faunal stage, typically set from 46,200,000 to 42,000,000 years before present lasting 4.2 million years.^[3] The Uintan Stage is a key part of the North American Land Mammal Age. In the Uinta Basin, a thriving subtropical ecosystem was formed at around 46.0 million years ago. It falls within the Eocene epoch, preceded by the Bridgerian and followed by the Duchesnean NALMA stages.^[4] The Uinta Formation is a key piece of this geologic stage. Mammalian sabretooths evolved and became dominant predators in the now-Western United States. These included Apataelurus, Diegoaelurus, and Machaeroides.^[5][6]

Uintan
46.2 – 42.0 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Chronology
−70 — – −65 — – −60 — – −55 — – −50 — – −45 — – −40 — – −35 — – −30 — – −25 — – −20 — MZ Cenozoic K Paleogene N LK Paleocene Eocene Oligocene MC Maastricht. Danian Selandian Thanetian Ypresian Lutetian Bartonian Priabonian Rupelian Chattian Aquitanian ← PETM ← First Antarctic permanent ice-sheets[1] ← K-Pg mass extinction Subdivision of the Paleogene according to the ICS, as of 2023.[2] Vertical axis scale: Millions of years ago
Formerly part of	Tertiary Period/System
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Upper boundary definition candidates	Calcareous nannofossil near LAD of the Haptophyte Reticulofenestra reticulata
Upper boundary GSSP candidate section(s)	Contessa highway section, Gubbio, Central Apennines, Italy

Substages

Uinta Formation, Uintah County, Utah, United States

The Uintan is considered to be contained within the Lutetian sharing the upper boundary and contains the following substages:

• Late/Upper Uintan: Lower boundary source of the base of the Uintan (approximate).
• Early/Lower Uintan: Upper boundary source of the base of the Duchesnean (approximate)