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Fossil hunters scour Anza Borrego State Park

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California's largest state park in eastern San Diego County can be intimidating. Summertime temperatures in the Anza Borrego State Park top 120 degrees and earthquakes from several active fault systems regularly shake the desert floor. Nevertheless, the park is a huge draw for professional and amateur paleontologists. They come to explore one of the richest continuous fossil records in North America. KPBS Environmental Reporter Erik Anderson has details.

This area is called the Borrego Badlands for a reason. The sun beaten terrain is sandwiched by two active earthquake faults. Paleontologist George Jefferson says one of those faults is actually pushing what used to be a relatively flat valley, up.

Jefferson: And what we see exposed here are tan and kind of pale brick reddish layers of sediment.

There is vegetation, but plants are few and far between. Winter rains have carved gullies and small canyons into the soft earth. Jefferson looks at an aerial map of the region.

Jefferson: We've just driven up the wash right here ..and we're parked right at this intersection right here.

Jefferson is traveling with a small group of amateur fossil hunters. They're in the badlands to recover an animal's leg bone discovered by retired civil engineer Phil Carskaddan. He says was walking up a twisting gully hoping to turn up the typical fossil found in the region, a bone fragment or two.

Carskaddan: Just prospecting around here. I come out here once a week and I was speechless, The left nine inches was exposed."

What he saw, was a horse's leg bone sticking out of the sandy bank.

Carskaddan: With a few exceptions, almost every bone is there.

Using memory aided by a Global Positioning System, Carskaddan leads the group on a short hike to the find. Jefferson says horse probably lived more than 800-thousand years ago. He hopes to secure the fossil before it gets damaged.

Jefferson: This particular specimen was found several months ago. And the reason we're here today is we're afraid that it would erode away with the winter rains.

The group covers the exposed bone with aluminum-foil. The artifact is then encased in a spray foam that hardens around the bone. The bone and its jacket are cut away from the bank and returned to the lab. There, it's cleaned up, glued together, dated and categorized.

Jefferson says about 40 people have taken enough of an interest in the region to invest some 160 hours of class, lab and field work. They learn how to find, clean, and categorize fossils so that the historical record is accurate. That, he says, helps him figure out the story of the region 10-thousand, a million or even five million years ago.

Sandra Keely helps supervise the laboratory work. She's already helped clean-up a number of fossils found in the park.

Keely: Here are a few items. This is a camel Llama jaw that took about, off and on, a year of not daily work but once a week three or four hours.

Keely says she sees herself as having a rather unique role at the lab, a role with an eye on the past AND the future.

Keely: We are actually helping future research in the earth's history, is basically what we're up to, so it's a small part but its an important part that we're doing.

Paleontologist George Jefferson says thousands of fossils have been pulled from the earth in the 600-thousand acre park. Specimens range from the Wooley Mammoth on display in the park's visitor center, to saber tooth cats, camels, and even fish. Jefferson say 550 distinct species have been recovered in the park and many of them no longer populate the earth.

Jefferson: Within the park there's something like four or five miles of sediment thickness and it goes back five million years, six million years. At six million years ago we have marine record in here. When the gulf, the ancient gulf of California actually came all the way to Palm Springs.

Jefferson says the park is one of a handful of locations in the United States that has a continuous fossil record that stretches back so far. The oldest terrestrial vertebrates found here lived more than nine million years ago.

Jefferson says fossils help researchers stitch together pictures of the past. He says that's particularly valuable when it comes to understanding the impact of climate change. Jefferson says fossil records are key to understanding the impact of climate change because they can show scientists what the area looked like during warm, wet periods and during the recent ice ages. Erik Anderson KPBS News.

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