“Over 230 types of vertebrate animals are found in the La Brea pits, including saber-toothed cats, mastodons, bears, wolves, camels, birds, insects, and even a few human bones and artifacts. These fossil remains are surrounded by naturally formed asphalt that seeped into the pits from underground oil reservoirs.

 

Modern college textbooks still maintain that the famous Rancho La Brea tar pits in southern California are evidence of sticky, tar-like material (bitumen) trapping and engulfing animals slowly over time. An alternative explanation contends that the collection of fossils is the result of catastrophic water transported by episodic flooding events during the Ice Age.

 

The pits themselves likely formed as methane gas and oil escaped from natural seeps through subterranean openings and collected in small, narrow openings resembling “blow-holes” where most of the bones are found. The major pits average around 15 feet in diameter, tapering downward from about 25 feet in rough conical shapes to just a few inches in width. The bones were commonly found as entangled masses packed tightly together, dismembered, and interlocking with the majority that were damaged in some fashion. Reconstructions of the various mammals on display are often composites of jumbled bones from different animals of the same species” (The La Brea Tar Pits Mystery).