In the Pits : Annual Dig at La Brea Yields More Bones and Some Rare Species

As the day waned Sunday, the rousing theme from “Raiders of the Lost Ark” filled Pit 91.

Sunday was the last day of the annual summer dig in Pit 91, one of the La Brea tar pits and the only such paleontological dig open to the public. Since July 5, volunteers have been unearthing Ice Age fossils at the bottom of a 28-by-28-foot excavation in Hancock Park, where seeping asphalt deposits have been trapping animals for 40,000 years.

As senior excavator Eric Scott explained, it is a recent tradition to play the sound track of “Raiders”--a movie whose hero is excavator extraordinaire Indiana Jones--”if we’ve had a successful summer.”

This summer, volunteers removed 786 animal and plant specimens from the gooey depths of the pit, which was first excavated in 1915 and was re-opened in 1969. “We did great!” said Scott, 27, pointing out that 62 fewer specimens were found during last summer’s dig, which lasted two weeks longer.

Summer can be tough in the pit, what with soaring temperatures and the occasional beer bottle lobbed into the excavation, said Scott, who is on the staff of the George C. Page Museum of La Brea Discoveries. But this August was unusually cool.

“It was beautiful working weather,” said Scott, whose volunteers unearthed such treasures as the hip and hoof of a dwarf pronghorn, rare in the area, and “a beautiful saber-toothed cat ulna” or foreleg bone. Scott kept careful field notes, including a record of exactly how each bone was positioned in the ground when it was found. Should future scientists need to, they will be able to visualize how the pit looked before the fossils were removed, he explained.

Throughout the summer, Scott supervised a dozen volunteers who spent hours crouched in awkward positions 13 feet down in the hole, chipping away with dental picks and other tools at the fossilized bones of ancient animals and plants.

Their only material benefit was the right to wear a special Pit 91 T-shirt designed by volunteers Harold Christiensen and Michael Charters. Only those who actually dig in the pit are allowed to wear the shirt, which features the skull of a saber-toothed cat. The museum shop wanted to sell the T-shirts, but Scott nixed the idea in order to protect their exclusivity.

Charters, 43, said digging for fossils has been a dream since childhood. “I grew up in Bermuda,” he said. “I remember reading books on the La Brea tar pits when I was a kid.”

A former postal worker who is now a househusband, Charters has dug for five summers. “I’ve never heard, ‘Hurry up,’ and I used to hear it all the time in the Post Office,” he said. The attitude in the pit, a museum staffer explained, is: “The fossils have been here for up to 40,000 years. They can wait another day.”

Volunteer Trudy Lee, 35, said she digs “because I just fell in love with it.” Lee, who is a buyer for a vintage clothing store, even likes the asphalt perfume of the pit. “I used to race motorcycles, so I was used to gas and oil and all that stuff. It smells great to me.” Lee said digging is stimulating, but she also finds the absolute concentration it requires to be relaxing, much as meditation is.

During the nine-week dig the volunteers excavated two 3-foot-by-3-foot-by-6-inch sections of the pit floor. One grid, as the units of excavation are called, was a weathered section that had been exposed to the elements for a number of years. The asphalt and other material around the bones in that grid had become extremely hard, Scott said, and the fossils it contained were soft and easily crumbled, making excavation a frustrating process of chipping off the non-fossil material flake by flake.

The other grid, Scott said, is an excavator’s dream. “The asphalt is gooier and has more fully penetrated the bone. As a result, the bone is better preserved.” Scott is looking forward to future excavations in this area, which is rich with whole bones well-preserved in soft, licorice-colored asphalt. This summer, he said, “was kind of a preview of coming attractions. For the next few years, we are going to be working in that absolutely gorgeous stuff.”

Earlier this year, scientists at the museum found an animal new to La Brea among the fossils in its ossuary, or collection of bones.

“There are a lot of boxes labeled ‘Elephant, miscellaneous’ that contain very little elephant and a lot of miscellaneous and occasionally some very rare things,” Scott said. Sorting through one such box a staff member found the bones of a small, stout-limbed horse that may be of the species Equus conversidens ; the analysis is not yet complete. No further evidence of the new horse showed up in the summer dig, however, nor did the volunteers unearth bones from another relatively recent La Brea find, a saber-toothed cat called Homotherium serum.

In recent years, paleontologists have come to appreciate the importance of microfossils, the remains of tiny plants and animals. “The big stuff is fun, but the little stuff tells us more,” said Scott. Even so, he waxed poetic about a big, beautiful bison tibia pulled from the pit on the final day. “There’s nothing like the thrill of finding something massive,” he confessed.