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 geochr ...

is the North American

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 convent ...

according to the

North American Land Mammal Ages The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when ref ...

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 La Brea Tar Pits is an active paleontological research site in urban Los Angeles. Hancock Park was formed around a group of tar pits where natural asphalt (also called asphaltum, bitumen, or pitch; ''brea'' in Spanish) has seeped up from the gr ...

) 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 A ...

'' 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 in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene Epoch within the ongoing Quaternary Period. Th ...

and

Late Pleistocene The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch withi ...

epochs. The Rancholabrean is preceded by the

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), spanning from 1.9 million – 250,000 years BP.

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 concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

(approximate) By another terminology, it can be split into two sub-intervals, ''Ra1'' from 250,000 to 115,000 years ago, and ''Ra2'' from 115,000 to 12,000 years ago. On other continents, the Rancholabrean shares this time period with the Oldenburgian of

European Land Mammal Ages The European Land Mammal Mega Zones (abbreviation: ELMMZ, more commonly known as European land mammal ages or ELMA) are zones in rock layers that have a specific assemblage of fossils (biozones) based on occurrences of fossil assemblages of Europ ...

, and the latter Lujanian of the South American Land Mammal Ages.

References

{{Quaternary Footer Pleistocene life Middle Pleistocene Late Pleistocene Pleistocene animals of North America Pleistocene California Geology of Los Angeles County, California