The San Timoteo Formation, also called the San Timoteo Beds, is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

History

Part of the wider San Timoteo Badlands, San Timoteo Formation was initially excavated in

San Timoteo Canyon San Timoteo Canyon is a river valley canyon southeast of Redlands, in the far northwestern foothills of the San Jacinto Mountains in the Inland Empire region of Southern California. Geography The canyon runs from its southern inflow mouth in ...

under by a team sponsored by

Childs Frick Childs Frick (March 12, 1883 - May 8, 1965) was an American vertebrate paleontologist. He was a trustee of the American Museum of Natural History and a major benefactor of its Department of Paleontology, which in 1916 began a long partnership wi ...

from 1916 to 1921.

Geology

The San Timoteo Formation represents Pliocene and Early Pleistocene sediments, mostly

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

. The Formation overlies the

late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

and

early Pliocene Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican d ...

Mt. Eden Formation (Jack Rabbit Trail & Eden Hot Springs localities, corresponding to the

Hemphillian The Hemphillian North American Stage on the geologic timescale is a North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 10,300,000 to 4,900,000 years BP. It is usually considered t ...

and Blancan faunal stages).

Fossils

Fossils of

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 1.8 million – 250,000 years Before Present, BP.

prehistoric mammals were found in the San Timoteo Formation (El Casco, Mammoth and Shutt Ranch localities). These include: * ''

Canis edwardii ''Canis edwardii'', also known as Edward's wolf, is an extinct species of wolf in the genus ''Canis'' which was endemic to North America three million years ago from the Late Blancan stage of the Pliocene epoch and was extinct by the end of the I ...

'' (Edward's wolf) * ''

Microtus ''Microtus'' is a genus of voles found in North America, Europe and northern Asia. The genus name refers to the small ears of these animals. They are stout rodents with short ears, legs and tails. They eat green vegetation such as grasses and se ...

sp.'' (vole) * '' Ondatra idahoensis'' (muskrat) * ''Mictomys kansasensis'' (bog lemming) * '' Erethizon cascoensis'' (porcupine) * “Plesippus” fracescana (three-toed horse) * '' Equus bautistensis'' (horse) * '' Tapirus merriami'' (tapir) * '' Odocoileus cascaensis'' (deer) * ''

Megalonyx ''Megalonyx'' (Greek, "great-claw") is an extinct genus of ground sloths of the family Megalonychidae, native to North America. It evolved during the Pliocene Epoch and became extinct at the end of the Late Pleistocene, living from ~5 million ...

sp.'' (ground sloth) * ''

Mammuthus A mammoth is any species of the extinct elephantid genus ''Mammuthus.'' They lived from the late Miocene epoch (from around 6.2 million years ago) into the Holocene until about 4,000 years ago, with mammoth species at various times inhabi ...

'' sp. (mammoth) * Possibly a giant bear (may be either ''Arctodus'' or ''Agriotherium'') Fossils have also been recovered from the El Casco Substation locality, which was dated to 1.4Mya. Recovered specimens include '' Smilodon gracilis'', ''

Homotherium ''Homotherium'' is an extinct genus of Homotherini, scimitar-toothed cat belonging to the extinct subfamily Machairodontinae that inhabited North America, Eurasia, and Africa, as well as possibly South America during the Pliocene and Pleistocene ...

'', two ground sloths, two types of camels, a llama, horse, and deer. Plant fossils include birch, pine, sycamore and oak trees.

References

* Geologic formations of California {{California-geologic-formation-stub

History

Geology

Fossils

See also

References