What is "irvingtonian"

The Irvingtonian North American Land Mammal Age on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 1,800,000 to 240,000 years BP, a period of . Named after an assemblage of fossils from the Irvington District of Fremont, California, the Irvingtonian is usually considered to overlap the Lower Pleistocene and Middle Pleistocene epochs. The Irvingtonian is preceded by the Blancan and followed by the Rancholabrean NALMA stages.

The Irvingtonian can be further divided into the substages of:

• Cudahyan: Lower boundary source: base of Irvingtonian (approximate)
• Sappan: Upper boundary source: base of Rancholabrean (approximate)