September 8, 2013

La Brea Tar Pits full of scientific wonder

Posted in Between Us column, Travel at 3:04 am by dinaheng

The bubble slowly rises from the dark slime, growing larger and larger, giving a graphic reminder that the Earth we live on is alive and kicking.

Here at the La Brea Tar Pits in Los Angeles, visitors can still see what the land looked like 30,000 years ago, complete with native plants and fossils from the Ice Age in the Page Museum on its grounds.Dinah Eng

Researchers have figured out that hardy bacteria, embedded in the natural asphalt, are chewing away at the petroleum and burping up methane.  Underneath all that gunk, they’ve unearthed the bones of mammoths, saber-tooth cats, and more, making the area the richest late-Pleistocene site in North America.

The natural asphalt acts as a preservative, so the tar has preserved fossils ranging in age from 11,000 to 40,000 years old, explains Ashley Fragomeni, gallery interpreter at the Page Museum.

“Back in 1913, the Hancock family had an asphalt mining base here, used for paving,” Fragomeni says. “As workers were digging, they found lots of bones that were determined to be Ice Age fossils. Researchers from the Natural History Museum of Los Angeles County came in and dug 96 pits. The oil field, which is 1,500 feet below us, accounts for the preservation of what we’ve found.”

The Hancock family donated the land to the County of Los Angeles, and today, paleontologists from the Page Museum continue to excavate the site, discovering new things every day.

If you walk through the museum, you’ll not only see an extensive collection of Ice Age land animal fossils, you can watch researchers in the Fishbowl Laboratory, cleaning the bones found in the tar pits.

“From selective carbon dating, we know that not all the deposits formed at the same time,” explains Shelley Cox, laboratory manager at the  museum. “We’ve found large bones, like a saber-tooth cat hip bone, and small things, like freshwater snails, beetle leg segments and a mouse toe in the sediment.”

The big specimen in the lab, affectionately dubbed Zed, is a 35,000-year-old Columbian mammoth, whose  skull sits in a plastic jacket in the lab, oil still leaking from the bone into the soil around it.

“There were lots of freshwater snail shells around him, so one possibility is that he may have washed here in a river,” Cox notes. “We know he was in his late 40s, early 50s, when he died — from the teeth — in elephant years. He was a robust individual who would have had 12 to 15 years to go if he hadn’t stepped in a tar pit.”

Excavation site at La Brea Tar Pits.  Photo by Dinah Eng

Excavation site at La Brea Tar Pits. Photo by Dinah Eng

Behind the scenes, researchers and volunteers are digging away in sheltered excavation pits on the grounds, explains Aisling B. Farrell, collections manager for Rancho La Brea, who notes that “the typical LaBrea asphalt deposit is jumbled with bones. We use dental picks to dig them out.”

While you can’t watch them work, you can visit the viewing station at Pit 91, where you can see one of the sites that was excavated, with goo still bubbling up to the surface.

Don’t worry about stepping into the muck, though. The museum’s grounds are immaculately landscaped.  If you walk around the Lake Pit, though, you might just see a life-sized mammoth family and American mastodon.

For more information on the Page Museum at the La Brea Tar Pits, check out http://www.tarpits.org/.

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