Hitting Pay Dirt in Fossils

Awhile ago, say, oh, about 200 million years B.F. (Before Freeways), North County wasn’t quite the same piece of suburban paradise it is today.

There were no red tile roofs, drive-through restaurants or four-lane connectors between mountains and sea.

It was part of a place called Pangaea, a supercontinent. That meant North County residents--if there were any--could theoretically walk to Nairobi or London. The route was lost about 100 million years ago when Pangaea broke up. Among other events, the Pacific plate--the slab of earth North County sits on--was being subducted under the North American plate.

That was all long before people fretted about real estate values, though.

The earliest fossil fragments found in San Diego County were discovered in the Penasquitos Valley and date from about 140 million years ago. The earliest complete fossils found in North County are about 76 million years old--which puts them in the Cretaceous Epoch.

Paleontologists have a good idea of what North County was like in prehistory because of the stories fossils tell and the events the landscape suggests. In fact, North County is considered one of the country’s best locations for fossils from the Eocene period--about 50 million years ago.

Some of the hottest finds in North County have been in the Carlsbad and Oceanside areas.

Two dinosaurs were unearthed near Palomar Airport. The nodosaur fossil is the only one found west of New Mexico. It also is one of the most complete nodosaur skeletons in the world.

Oceanside is known for its deposits of whale fossils dating from 5 to 7 million years ago.

The San Dieguito Valley has yielded several shell sites from the Pleistocene Epoch and Fairbanks Ranch has yielded a fossil of a giant ground sloth from about 40,000 years ago.

In an artifact dating from the time when humans were first making themselves at home in North County, a small stone sculpture of a bear was found near the Agua Hedionda Lagoon in 1985. Earlier this year, the 7,500-year-old sculpture was named the official prehistoric artifact of California. The Chipped Stone Bear, which measures 2 1/2 inches, is the only state symbol to honor native inhabitants.

For many years, North County was not thought to be terribly rich in fossil remains. But, during the 1980s, the scourge of development proved to be a boon to fossil hunters. Cities like Carlsbad passed ordinances designed to preserve the fossil record. The state passed the California Environmental Quality Act, which carried fossil preservation provisions.

When the land is disturbed, the developer must contract with a paleontologist to evaluate what is being unearthed.

Paleo Services is an Escondido-based firm that monitors development sites. It is headed by Tom Demere, who is also head of the paleontology department at the San Diego Natural History Museum. When Demere and his partners make a find, the fossils are given to the museum.

“There can be as few as one fossil or as many as hundreds or even thousands of fossils in a small area,” said Matt Colbert, a museum paleontologist. “Our collections have increased a hundred fold (since the development boom). Almost all the really good stuff came from development sites.”

When fossils are found, a great deal of contextual analysis must be done. For example, how old are the rocks in which the fossil is embedded? Are there any other fossils surrounding the find? If so, what does it mean?

“Every time you make a find you pose 10 more questions than you answer,” Colbert said. You have to be careful not to carry your evidence too far.”

Take the hadrosaur and nodosaur fossils found near Carlsbad’s Palomar Airport. Those skeletons are encrusted with ancient clam shells. Although the area is now dry land, it was under water when the creatures died. It is believed that the remains were washed by a stream into the sea and the mollusks used them as an artificial reef.

Not all finds are of huge skeletons--or are made by scientists.

What may be one of the most important finds to ever occur in North County was made by a 12-year-old boy. The site, called Jeff’s Discovery, is from the Eocene period and is off the Highway 78 extension.

One full skeleton of a protoreodont, a running mammal, was found. More importantly, hundreds of teeth and other remains that tell researchers about how ancient creatures lived also were discovered.

Jeff’s Discovery a decade ago further enhanced North County’s reputation as one of the richest Eocene sites in the country. According to Demere, North County is comparable to the Eocene fossil fields of Utah and Wyoming.

“Many of the Eocene finds from North County are the best specimens found,” Demere said.

Evidence of North County’s prehistoric past is not hard to find.

“Just by driving on Highway 78, you can go from an ancient river plain to an area that 140 million years ago was 8 miles under the earth,” Demere said.

The modern sea cliff shore is the best and easiest place to find fossils because the layers of the earth are clearly visible and because constant erosion reveals new finds.

According to Colbert, oyster beds can be seen on Cardiff State Beach and in Solana Beach and Swami’s.

Since the mesas in North County were once seashore, they also are good fossil-hunting grounds. For example, the red rock on top of most North County mesas--easily visible from freeways--is a marine layer laid down when the sea covered the land during the Pleistocene Epoch, about 2 million years ago.

The Anza-Borrego desert is another popular place for spotting fossils.

Both sea life and mammals have been found in abundance, reflecting Anza-Borrego’s history as both a seabed and a savannah. (It is, by the way, illegal to take fossils from the Anza-Borrego Desert State Park.)

In general, Colbert said, fossil hunters should look for areas of sedimentary rock--rock formed by layers of sediment piling atop one another until the sediment turns to stone or clay. Fossils are found in such formations.

The paleontologists at the Natural History Museum would not reveal exact locations of past fossil finds, fearing that unrestricted fossil hunting could damage scientific evidence.

“It’s good to encourage people to explore their world,” Colbert said, “but it is nice when they have an idea of the significance of the finds.” Both Demere and Colbert encourage fossil hunters to bring their finds to the attention of the museum. That’s how Jeff’s Discovery was identified.

But Demere believes fossil hunters should not remove fossils from their context. More than one fossil field has been damaged by collectors digging pieces out of the ground.

Instead, Demere encourages fossil hunters to view the fossils, take pictures, but leave the fossils where they are for future generations.

In addition to being able to continue the analysis of earliest times, those future paleontologists will undoubtedly have new things to puzzle over--such as surfboard shops and Car Country Carlsbad.