Among the finds is a near-intact mammoth skeleton and bones of saber-toothed cats, dire wolves, bison, horses, ground sloths and other mammals.
Researchers discovered 16 fossil deposits under an old parking lot next to the tar pits in 2006 and began sifting through them last summer.
Officials with the Page Museum at the tar pits plan to formally announce their findings on Wednesday. The discoveries could double the museum's Ice Age collection.
Such a rich find usually takes years to excavate. But with a deadline looming to build an underground parking garage for the next-door art museum, researchers boxed up the deposits and lifted them out of the ground using a massive crane for later study.
"It's like a paleontological Christmas," research team member Andie Thomer wrote in a blog post in July.
The research dubbed "Project 23" — because it took 23 boxes to house the deposits — uncovered fossilized mammals along with smaller critters including turtles, snails and insects. Separately, scientists found a well-preserved Columbian mammoth complete with 10-foot-long tusks that they nicknamed Zed.
An examination reveals Zed, which is 80 percent complete, had arthritic joints and several broken and re-healed ribs — an indication that he suffered a major injury during his life.
"It's looking more and more as if Zed lived a pretty rough life," Thomer blogged in December.
Some scientists not connected with the discovery said this is the first significant fossil find since the original excavations at the tar pits more than a century ago.
"Usually these things are either lost in the mixing or not recovered in the processing of the oily sand and soil they occur in," paleontologist Jere H. Lipps of the University of California, Berkeley wrote in an e-mail to The Associated Press.
William Akersten, curator of fossil vertebrates at the Idaho Museum of Natural History, said the mammoth skeleton is impressive because previous mammoth remains at the tar pits have been "isolated bits and pieces."
"It could greatly refine our knowledge of what went on there," said Akersten, a former supervising curator of La Brea Tar Pits, who had no role in the recent discovery.
The La Brea Tar Pits ranks among the world's famous fossil sites. Between 10,000 and 40,000 years ago, mammoths, mastodons, saber-tooth cats and other Ice Age beasts became trapped by sticky asphalt that oozing upward through cracks and fissures in the ground. The newly recovered fossils were also in asphalt.
Since 1906, more than a million bones have been unearthed from the sticky ponds wedged between museums, offices and condos in the city's bustling Wilshire-Fairfax district.
Page Museum: http://www.tarpits.org