|The 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 Los Angeles 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 the 100+ pits, one (Pit 91) continues to be regularly excavated for two months each summer.|
La Brea is Spanish for "the tar". 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.
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 were 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.