Mammoth remains in Earth's womb

The largest known deposit of fossils from the last ice age has been found in what might seem to be the unlikeliest of places — under an old May Co parking lot in the tony Miracle Mile shopping district of Los Angeles.

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

Prized possession

Among their finds is the almost intact skeleton of a Columbian mammoth — named Zed by researchers — a prize discovery because until now, only bits and pieces of mammoths have been found in the tar pits.

However, researchers are more excited about finding smaller fossils of tree trunks, turtles, snails, clams, millipedes, fish, gophers and even mats of oak leaves.

The first excavators at La Brea had thrown out similar items in their haste to find prized animal bones and crucial information about the period was lost.

New technique

Because of its need for haste, the team is pioneering a new technique for extracting the fossils. Most palaeontologists spend days sifting through the soil at the site of a dig.

In this case, huge chunks of soil from the site have been removed intact and now sit in large wooden crates on the back lot of the Page.

The 23 crates range in size from 5x5x5 feet to 19x12x10 feet and are responsible for the excavation's informal name, Project 23.

The site of the old parking garage, used by the now defunct May Co, is adjacent to the Page.

The Page's sister museum, the Los Angeles County Museum of Art (Lacma), owned the building and had razed it to construct a garage that would restore parkland above the structure.

The entire Rancho La Brea area is a palaeontological treasure chest. Petroleum from the underground oil fields oozed to the surface, forming bogs that trapped and killed unsuspecting animals and preserved their skeletons. It is now a protected site.

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 on Los Angeles's Westside, who had overseen work on other sites at or near the tar pits.

“I knew we would find fossils but I never expected to find so many deposits,'' Turner said.

There were 16 separate deposits on the site, an amount that, by her estimate, would have taken 20 years to excavate.

But with the officials of Lacma 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 similar to that used to move large living trees.

Identifying the edges of each deposit, her team dug trenches around them and underneath, isolating the deposits on dirt pedestals.

After wrapping heavy plastic around the deposits, workers built wooden crates and lifted them out with a heavy crane. The biggest one weighed 123,000 pounds.

Hard work pays

In 3-1/2 months, working seven days a week, she and her colleagues removed the entire collection and delivered it to the Page two years ago.

For some of the deposits, she noted, they had to wear oxygen tanks with full gas masks because of high levels of hydrogen sulphide escaping from the soil.

The 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.

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

Curators collected 34 mammoths in the initial excavations of the La Brea Tar Pits from 1906 to 1914.

The team does not know the ages of the deposits yet. All specimens from the area date from 10,000 to 40,000 years ago and there is no reason to suspect these will be any different.

Individual fossil deposits in the area generally cover a time span of about 2,000 years, Harris said, and deposits that are just a few feet apart can be separated in time by thousands of years.

“Hopefully, the 16 [new] deposits will have 16 different ages,'' Shaw said.