The Wasatchian North American Stage on the geologic timescale is the North American faunal stage

Faunal stage

In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...

 according to the North American Land Mammal Ages

North American Land Mammal Ages

The North American Mammal Ages establishes a geologic timescale for prehistoric North American fauna beginning 66.5 Ma during the Paleocene and continuing through to the Late Pleistocene...

 chronology (NALMA), typically set from 55,400,000 to 50,300,000 years BP

Before Present

Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

 lasting . It is usually considered to be within the Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

, more specifically the Early Eocene. The Wasatchian is preceded by the Clarkforkian

Clarkforkian

The Clarkforkian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 56,800,000 to 55,400,000 years BP lasting . It is usually considered to be within the Paleocene, more specifically the...

 and followed by the Bridgerian NALMA stages.

The Wasatchian is considered to contain the following substages:

• Lostcabinian: (shares upper boundary) and lower boundary source of the base of the Wasatchian (approximate).
• Lysitean: Lower boundary source. Base of Wasatchian (approximate) and upper boundary source of the base of the Bridgerian (approximate).
• Graybullian: Lower boundary source: base of Wasatchian (approximate) and upper boundary source of the base of the Bridgerian (approximate).
• Sandcouleean (shares lower boundary) and upper boundary source of the base of the Bridgerian (approximate).