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La Brea Tar Pits

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Three mastadon statues are included in the La Brea Tar Pits.
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Three mastadon statues are included in the La Brea Tar Pits.

Gas bubble slowly emerging from a smaller tar pit at La Brea Tar Pits.
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Gas bubble slowly emerging from a smaller tar pit at La Brea Tar Pits.

The La Brea Tar Pits (or Rancho La Brea Tar Pits) are a famous cluster of tar pits located in the Miracle Mile district of Los Angeles, California; here buried asphalt seeps to the surface from the extensive petroleum deposits below the surface of the Los Angeles Basin. It is best known for the large number of mammal fossils from the last ice age which have been found there, but fossilized insects and plants, even pollen grains, help fill out a picture of the cooler, moister climate of the Los Angeles basin during the glacial age. Such microfossils are retrieved from their matrix of asphalt and sandy clay by washing with a solvent to remove the petroleum, then picking through the remains under a high-powered lens. The George C. Page Museum, part of the Natural History Museum of Los Angeles County, presents these discoveries. Of more than a hundred pits, one (Pit 91) continues to be regularly excavated for two months each summer, under the watchful eyes of tourists.

Brea is Spanish for "tar", "The La Brea Tar Pits" therefore being a tautological term "The The Tar Tar Pits" (an example of pleonasm). The 'tar' pits were used as a source of asphalt (for use as low-grade fuel and for waterproofing and insulation) by early settlers of the Los Angeles area. The bones were taken for the remains of unlucky pronghorns or local cattle that had become mired.

La Brea may be the only excavation site in the world where the predators found outnumber prey. Ten predators have been recovered for each prey animal. The reason for this is unknown but one credited theory is that a large prey animal (say, a mastodon) would die naturally or accidentally become entrapped in a tar pit, attracting numerous predators across long distances, for an easy meal. This so-called predator trap would kill many animals that find themselves stuck with their prey. Another theory, specific to the Dire Wolf, suggests that both prey and predators may have been trapped accidentally during the hunt. Since wolves hunt in packs, each prey animal could take several wolves with it.

Among the prehistoric species associated with the La Brea Tar Pits are mammoths, dire wolves, short-faced bears, ground sloths, and the state fossil of California, the saber-toothed cat, Smilodon californicus. Much of the early work in identifying species was performed in the early 20th century by John C. Merriam of the University of California.

Radiometric dating of preserved wood and bones has given an age of 38,000 years for the oldest known material from the La Brea seeps, and they are still ensnaring organisms today.

Rancho La Brea is the most famous, but there are two other asphalt pits with fossils in southern California: in Carpinteria, Santa Barbara County and McKittrick, in Kern County. There are other fossil-bearing asphalt deposits in Texas, Peru, Trinidad, Iran, Russia and Poland.

For other rich deposits, fossilized where they occurred, see Lagerstätten.

La Brea Animals & Plants

Extinct mammals have their scientific names appended. This is a selection from the [complete catalogue].

La Brea in fiction

La Brea Tar Pits in Los Angeles County's Miracle Mile District. The model animals amuse tourists.
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La Brea Tar Pits in Los Angeles County's Miracle Mile District. The model animals amuse tourists.

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