Fossil field in Hancock Park (formerly Rancho La Brea), Los Angeles , Calif.
, U.S. It is the site of "pitch springs" oozing crude oil, discovered by Gaspar de Portolá's expedition in 1769. The tar pits contain the fossilized bones of Pleistocene mammals that became entrapped there; they include mammoths , mastodons , and sabre-toothed cats. The George C. Page Museum contains more than one million prehistoric specimens exhumed from the pits.