The Chadronian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 38,000,000 to 33,900,000 years BP. It is usually considered to fall within the Oligocene epoch. The Chadronian is preceded by the Duchesnean and followed by the Orellan NALMA stages. The Chadronian can be further divided into the substages of: