North American faunal stage according to the North American Land Mammal Ages chronology
The Rancholabrean 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 less than 240,000 years to 11,000 years
BP, a period of 0.229 million years.[1] Named after the famed
Rancho La Brea fossil site (more commonly known as the
La Brea tar pits) in Los Angeles, California,[2] the Rancholabrean is characterized by the presence of the genus Bison in a Pleistocene context, often in association with other extinct Pleistocene forms such as Mammuthus.[2][3] The age is usually considered to overlap the late
Middle Pleistocene and
Late Pleistocene epochs. The Rancholabrean is preceded by the
Irvingtonian NALMA stage, and it is succeeded by the
Santarosean age.[4]
The Rancholabrean can be further divided into the substages of the
Sheridanian: Upper boundary source of the base of the
Holocene (approximate)[5]
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.[6]
^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
^
abSavage, 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
^Bell, C.J.; et al. (2004). "The Blancan, Irvingtonian, and Rancholabrean mammal ages". In Woodburne, M.O. (ed.). Late Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and Geochronology. New York: Columbia Univ. Press. pp. 232–314.
ISBN0-231-13040-6.