The Rancholabrean North American Land Mammal Age on the
geologic timescale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geoch ...
is the North American
faunal stage according to the
North American Land Mammal Ages chronology (NALMA), typically set from less than 240,000 years to 11,000 years
BP, a period of .
[Sanders, A.E., R.E. Weems, and L.B. Albright III (2009) Formalization of the mid-Pleistocene "Ten Mile Hill beds" in South Carolina with evidence for placement of the Irvingtonian–Rancholabrean boundary, ''Museum of Northern Arizona Bulletin'' 64:369-375] Named after the famed
Rancho La Brea fossil site (more commonly known as the
La Brea tar pits) in Los Angeles, California,
[Savage, D.E. (1951) Late Cenozoic vertebrates of the San Francisco Bay region, ''University of California Publications, Bulletin of the Department of Geological Sciences'' 28:215-314] the Rancholabrean is characterized by the presence of the genus ''
Bison
Bison are large bovines in the genus ''Bison'' (Greek: "wild ox" (bison)) within the tribe Bovini. Two extant and numerous extinct species are recognised.
Of the two surviving species, the American bison, ''B. bison'', found only in North ...
'' in a Pleistocene context, often in association with other extinct Pleistocene forms such as ''
Mammuthus''.
The age is usually considered to overlap the late
Middle Pleistocene
The Chibanian, widely known by its previous designation of Middle Pleistocene, is an Age (geology), age in the international geologic timescale or a Stage (stratigraphy), stage in chronostratigraphy, being a division of the Pleistocene Epoch withi ...
and
Late Pleistocene epochs. The Rancholabrean is preceded by the
Irvingtonian NALMA stage, and it is succeeded by the
Santarosean age.
The Rancholabrean can be further divided into the substages of the
Sheridanian: Upper boundary source of the base of the
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which