STUCK IN THE MUCK; NEW DISCOVERIES AT LA BREA COME STEADILY, BUT SLOWLY.

Byline: Story By Carol Bidwell Staff Writer

Forget the skyscrapers for a moment. Ignore the traffic, the tourists, the row of modern museums on Wilshire Boulevard.

Drift back into history 30,000 or 40,000 years in that spot.

A vast grassy plain stretches out before you, and thousands of varieties of animals roam free - from giant-tusked mammoths to giant sloths, from saber-toothed tigers to tiny birds, from early bison to antelope and camels.

Out of the ground seeped brown sticky goop. Animals, perhaps thinking it was good to drink or maybe just trying to get from one side to the other, got their feet stuck in the stuff. They probably bellowed and howled for help, but there was nobody to rescue them. They slowly starved to death, trapped in the ooze.

Other animals came along and, seeing the trapped prey as dinner, got stuck, too.

Multiply that thousands of times and it explains what paleontologists say is the most concentrated and well-preserved cache of fossils anywhere in North America.

When scientists anywhere in the world have a bone or a skull they can't identify, they bring it to the George C. Page Museum at the site of the La Brea Tar Pits, where they almost always find a match.

About the only thing that's missing are the bones of dinosaurs, which became extinct about 65 million years ago, long before the sticky trap formed, say scientists.

Since 1908, more than 1 million fossils have been dug out of the ooze - which, in fact, is not tar but asphalt deposits - of more than 100 excavations in 23-acre Hancock Park. But the richest source of animal, bird and insect remains has been Pit 91, where every summer for the past 30 years, crews of mostly volunteers have used hammers, chisels and shovels to unearth the bones trapped in the sticky goo.

And it's digging with a purpose, not just to unearth the past but to try to predict the future, said John M. Harris, 55, of Pasadena, chief curator and head of the Natural History Museum of Los Angeles County's paleontology section.

``What we find tells us what life was like in Los Angeles at the end of the ice age, some 28,000 years ago,'' he said. ``We know that when it began to warm up, that's when many of the larger animals - anything larger than a coyote - began to die off ... We're facing the same kind of thing today with global warming.

``If we can figure out what happened to them and why, maybe we can head off the same thing happening to us.''

``Figuring out why they went extinct is very important for our own future,'' agreed Christopher Shaw, 47, of Simi Valley, who started 30 years ago in the pit as a ``digger'' and today is collections manager for the Page Museum. ``The cycle of life and death and growth just repeats itself. So it makes sense that you should have a window into the future.''

Hancock Park's window into the future is opening - very slowly. While some excavations were done as early as 1908, workers dig Pit 91 for only two months each summer; that's all the $12,000 annual budget from the donation-supported Natural History Museum Foundation will support.

``We could probably get all the excavation done in three or four years if we could work year-round,'' Harris said. ``But working two months at a time, we've probably got 15 or 20 years more work to do.''

After that, there's a new excavation site - designated only as GPS12 - a few hundred yards west of Pit 91, behind the County Museum of Art, that may prove nearly as valuable as anything yet found. The site was discovered a few months ago, while crews were spiffing up the park as part of a $10 million redevelopment effort.

Initial inspection of the new site has turned up bones of saber-toothed tigers, dire wolves, bison, giant sloths and early horses, but it's possible the remains of older, large animals - possibly even elephants and mammoths, like those found several years ago in Pit 9, just a few yards from Pit 91 - might lie farther down in the ooze.

But paleontologists are patient people. They say they won't dig any more at the new site until they empty Pit 91, which means that the people who found the new site may not live long enough to see what lies deep beneath the surface.

But there are wonders enough in Pit 91 to keep them digging. After all, it's the thrill of discovery that keeps the excavation going.

Kelly Darraugh, 29, of Reseda, a mortgage underwriter for a Pasadena firm who's gone on archeological digs in her spare time since she was 12, recalls the thrill last summer of unearthing the partial skull of a North American lion, estimated to be about 30,000 years old.

``That gave me goosebumps,'' said the volunteer. ``It kind of connects you, on a certain level, with that time. That's my lion now. I get to work with it. I get to clean it. I feel very protective of it. And I'd love to find the rest of it.''

But working in the gooey asphalt pit - as smelly and messy as the job is - is a privilege that must be earned. Volunteers first must work for 96 hours in the museum's lab, cleaning fossils, piecing together broken bones and separating microfossils with a tiny paintbrush under a strong magnifying glass. Besides weeding out the fun-seekers from the serious workers, the stint in the lab also teaches volunteers how to carefully handle the precious fossils.

``By the time I got into the pit, I was so excited,'' Darraugh said. ``If you don't really enjoy it, I guess you'd call it work. But it's really a reward. When you pull a bone out of the ground, you're the first human being to touch it and hold it.''

While the big finds are exciting, Shaw said, it's the unimpressive discoveries that actually tell paleontologists about life thousands of years ago. The large animals wandered from place to place to find food, but tiny animals like squirrels and rats generally lived all their lives near where they were born. So studying those remains - along with shells, insects and even bits of pollen and wood - give scientists a pretty clear picture of Los Angeles long ago.

From the fossils they've found, scientists say this area once was covered with water. After the sea receded, the climate was still much cooler than it is today and a lot more humid, probably the product of the receding glaciers. And redwood fossils discovered in Pit 91 indicate that the big trees, now generally seen only in the mountain forests of Northern California, grew along what is now Wilshire Boulevard.

Museum lab supervisor Shelley Cox, 50, of Van Nuys and her staff of volunteers discover much more about what's dug out of the pit when they wield their paintbrushes, pipe cleaners, Q-Tips, toothbrushes and solvent-saturated rags.

``It's tedious, meticulous, repetitious work,'' Cox said. ``But there's a thrill there because when you clean the asphalt off a bone, you're the first person who's seen it that way. There's still that, `Wow, look at that!' excitement that you feel with discovery.''

One of their finds, for example, is that mastodons - who were grass-eaters - grew successive sets of teeth. Worn-down teeth in the back of both sides of the jaw would fall out, replaced by two new teeth that would grow in the front of the jaw.

``We don't know for sure how many sets of teeth they had, but we do know that at some point, new teeth stopped coming in,'' Cox said. ``When all their teeth fell out, they couldn't eat - and they died.''

Some of the most interesting finds have been among the microscopic sludge that settled out of the asphalt after a bone was left to soak in solvent. In one batch, viewed through a powerful magnifying glass, Cox found pieces of bone, fossilized insects and snails, and a single squirrel's tooth.

``This kind of material allows you to put the big stuff in context. This lets you see the background of the area. You didn't just have big animals running around. You had fish and little animals and insects, everything from grass and pollen up to tree trunks. It's a vast storehouse of information.''

Cox, who began work at the digs when she was a high-school girl, says piecing things together in the lab is like assembling a giant jigsaw puzzle.

``And along the way,'' she said, ``we learn so much about the creatures that lived so long ago - and, in a way, about ourselves.''

Park visitors can watch excavation work in Pit 91 from a glassed-in perch behind the Museum of Art; the viewing station is open from 10 a.m. to 4 p.m. Wednesday through Sunday through Sept. 12. Visitors to the Page Museum, 5801 Wilshire Blvd., can watch volunteers clean and piece together fossils in the glassed-in lab; the museum is open from 9:30 a.m. to 5 p.m. weekdays and 10 a.m. to 5 p.m. weekends. Admission is $6 for adults, $3.50 for students and seniors, and $2 for children ages 5-12. For information, call [phone] or check out the museum's Web site at www.tarpits.org.

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7 Photos

PHOTO (1--Cover--Color) OOZE that's NEWS

La Brea Tar Pits reveal life in prehistoric L.A.

(On the cover: Kelly Darraugh of Reseda, a volunteer excavator, works on an area of Pit 91.)

(2--Color) Chief paleontologist John Harris climbs out of Pit 91, where fossils of animals have been excavated from the Hancock Park site every summer for the past 30 years.

(3--Color) Working from wooden scaffolding just above the surface, volunteers Sharen Dyer, left, Michael Cressner and Lauren Michaelson search a 3-square-foot area of Pit 91.

(4--Color) A rib bone, probably from a saber-toothed tiger, is removed and headed for the lab for cleaning. Though the site is known as the tar pits, the sticky goo that trapped the animals thousands of years ago is actually asphalt.

(5--Color) Saber-toothed tiger rib bones, broken in the early 1900s in the process of being cleaned, wait to be pieced together in the lab.

(6--Color) Lab supervisor Shelley Cox and the staff at the Page Museum assist paleontologists trying to identify fossils found in other parts of North America.

(7) Supervisor Shelley Cox separates tiny fossils in the Page Museum lab as visitors watch.

Photos by Tom Mendoza/Staff Photographer