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Major cache of fossils unearthed in L.A.

A nearly intact mammoth, dubbed Zed, is among the remarkable discoveries near the La Brea Tar Pits. It's the largest known deposit of Pleistocene ice age fossils.

February 18, 2009|Thomas H. Maugh II

Workers excavating an underground garage on the site of an old May Co. parking structure in Los Angeles' Hancock Park got more than just a couple hundred new parking spaces. They found the largest known cache of fossils from the last ice age, an assemblage that has flabbergasted paleontologists.

Researchers from the George C. Page Museum at the La Brea tar pits have barely begun extracting the fossils from the sandy, tarry matrix of soil, but they expect the find to double the size of the museum's collection from the period, already the largest in the world.

Among their finds, to be formally announced today, is the nearly intact skeleton of a Columbian mammoth -- named Zed by researchers -- a prize discovery because only bits and pieces of mammoths had previously been found in the tar pits.

But researchers are perhaps even more excited about finding smaller fossils of tree trunks, turtles, snails, clams, millipedes, fish, gophers and even mats of oak leaves. In the early 1900s, the first excavators at La Brea threw out similar items in their haste to find prized animal bones, and crucial information about the period was lost.

"This gives us the opportunity to get a detailed picture of what life was like 10,000 to 40,000 years ago" in the Los Angeles Basin, said John Harris, chief curator at the Page. The find will make the museum "the major library of life in the Pleistocene ice age," he said.

Because of its need for haste, the team also is pioneering a new technique for extracting the fossils. Most paleontologists spend days to weeks carefully sifting through the soil at the site of a dig. In this case, however, huge chunks of soil from the site have been removed intact and now sit in large wooden crates on the museum's back lot. The 23 crates -- ranging in size from that of a desk to that of a small delivery truck -- are responsible for the excavation's informal name, Project 23.

The site of the old two-story parking garage, which was used by the now-defunct May Co. department store, is now owned by the Page's neighboring museum, the Los Angeles County Museum of Art. LACMA had razed the building to construct an underground parking garage that would restore parkland above the structure.

The entire Rancho La Brea area at Hancock Park is a paleontological treasure chest. Petroleum from the once-massive underground oil fields oozed to the surface over the millennia, forming bogs that trapped and killed unsuspecting animals and then preserved their skeletons. It is now a protected site, although dispensation was granted to build the new garage.

Because of the historic nature of the area, the work had to be overseen by a salvage archaeologist. In this case, the work fell to Robin Turner, founder of ArchaeoPaleo Resource Management Inc. of Culver City, which previously had overseen work on other sites at or near the tar pits. Her group hit pay dirt when the excavation got about 10 feet below the surface.

"I knew we would find fossils . . . but I never expected to find so many deposits," Turner said. "There was an absolutely remarkable quantity and quality."

There were 16 separate deposits on the site -- an amount that, by her estimate, would have taken 20 years to excavate conventionally. But with LACMA officials prodding her "to get those things out of our way" so they could build their garage, she had to find another way.

Her solution was a process similar to that used to move large living trees. Carefully identifying the edges of each deposit, her team dug trenches around and underneath them, isolating the deposits on dirt pedestals. After wrapping heavy plastic around the deposits, workers built wooden crates similar to tree boxes and lifted them out individually with a heavy crane. The biggest one weighed 123,000 pounds.

"We designed a crate so that we could take out the entire deposit without disturbing it so that, at a later date, you could do a proper excavation as you would if it were still in the ground," she said.

In 3 1/2 months, working seven days a week, she and her colleagues removed the entire collection two years ago and delivered them to the museum. For some of the deposits, she said, they had to wear oxygen tanks with full gas masks because of unusually high levels of hydrogen sulfide escaping from the soil.

The only exceptions to the crating process were the mammoth named Zed and a horse skull. Because they were separate from the other assemblages, they were partially excavated and encased in plastic casts for cleaning in the museum -- the conventional technique for recovering fossils.

Curators are excited about Zed because he appears to be about 80% complete, missing only one rear leg, a vertebra and the top of his skull, which was shaved off by excavation equipment.

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