Students and faculty search for specimens during an excavation at the Carmel Church site in Ruther Glen, Va. The fossil bed has yielded more than 20,000 bones of more than 50 species of marine animals. (Bonnie Jo Mount/WASHINGTON POST)

Hidden behind an old rock quarry south of Fredericksburg is a nondescript sandpit that opens a window on the world of 14 million years ago, a spot where dolphins frolicked and sharks hunted. Today, teams of student and volunteer diggers are pulling out a jackpot of fossils sandwiched between layers of bluish-gray rock.

“We don’t know how they got here,” said Alton Dooley, a paleontologist at the Virginia Museum of Natural History, as he chipped away at the clay surrounding a newly uncovered bone. Dooley and other scientists say this is one of the biggest fossil sites east of the Mississippi — staggering in both number and diversity of species. “The most striking thing is the sheer number of bones and teeth that are packed in such a small area. In 20 years, we’ve only excavated about 4,000 square feet, and we’ve pulled out tens of thousands of specimens.”

Dressed in muddy camo pants, sweatshirt and ballcap, Dooley ponders the riddle of what is called the Carmel Church quarry site. How did all these animals end their lives in this one small patch of once-submerged ground? Was there a cataclysmic event, such as a landslide or a toxic red tide that killed them all? Maybe it was an ancient whale graveyard, or a calving ground? Or is the treasure trove the result of some slow geologic process?

Since he started coming here in 1990, Dooley’s crews have uncovered just a small portion of the exposed sandy slope. He leads digs here several times a year, sometimes with volunteers from local colleges or the natural history museum. Last week, it was four college students — plus Dooley’s wife and 15-year-old son — who joined him to spend six days of their spring break in the dirt and mud.

‘Pretty crazy’

The technology for examining fossils may have advanced, but the process of digging them out remains slow and painstaking. Bundled in stocking caps and fleece jackets against a pre-storm chill, the students knelt on foam pads, working away at the foot of a 15-foot wall of sediment. They were doing paleontology the old-fashioned way — some more enthusiastically than others.

“I have friends on cruises and at Mardi Gras this week,” said Jordan Hutton, a 19-year-old sophomore at Roanoke College. He poked the hard, compact soil with a small dental pick. “I’m pretty jealous.”

He acknowledged, though, that at least he’d come away from spring break with something besides a hangover.

“I’ve always liked science, but not enough to study it intensely,” said Hutton, whose major is art history. “Here I’m learning about the patience and time that it takes to do it. The way they put together a skeleton is like the way I put together a painting.”

In just a few days of digging, Hutton had found two fish vertebrae, part of a whale and some carbonized wood. Hutton said he would take the wood back to his biology class, where he hopes to examine it under an electron microscope to figure out what kind of tree it was.

Nearby, Laura Kellam was excavating with a chisel, a garden spade, a dental pick and a paintbrush. “To look at the different layers of the sediment,” said Kellam, an environmental science major at Roanoke College, “and to think that 14 million years ago this was underwater here in Virginia is a pretty crazy concept.”

Tapping with her pick, she heard the hollow sound that signaled she’d found a bone rather than a rock. She pointed to the selection of fossils already crowded around her knees, the product of that day’s digging.

“There’s a whale, a fish [skull] plate, and then some dolphin vertebrae over here,” she said.

Location of fossil dig site (THE WASHINGTON POST)

Prolific days are not unusual at Carmel Church. Dooley enumerated the marine creatures he has identified since 1990: 17 species of whales and dolphins; 15 to 20 kinds of sharks; seals; sea turtles; 20 to 30 fish, including sunfish, tuna, drum and sturgeon; and crocodile. Some of the fossils are pressed together, overlapping, as if they had settled to the bottom on top of one another. Some have bite marks, evidence that the carcasses had been eaten by sharks or other scavengers.

The teams have also found land animals that Dooley believes were washed out to sea, including a camel, a tapir, a piglike mammal called a peccary and some extinct animals, including the dromomerycid, a deerlike creature with three horns, and a dog-size horse ancestor called Calippus.

Jawbones of a whale

The biggest find at Carmel Church was the nearly complete 30-foot whale skeleton that Dooley discovered in 1990. It took years of digging and preparation before he described — and named — Eobalaenoptera harrisoni, a previously unknown extinct baleen whale, in a scientific paper in 2004.

An impressive cast of the whale skeleton hangs in the atrium of the Caroline County Visitor Center in Ruther Glen, a few miles from the site.

Nicholas Pyenson, a curator at the Smithsonian’s Museum of Natural History, has studied similar “bone beds” on the West Coast, including Sharktooth Hill near Bakersfield, Calif., a formation that stretches for more than 30 miles and has the fossilized remains of tens of thousands of shells and marine animals.

“They’re formed when the bones are concentrated in one spot,” Pyenson said. “But many different things could be the cause. Maybe they all did die together. Maybe it is an environmental thing, like an ocean current or river channel. The riddle is how the concentration occurred.”

Bone beds along Maryland’s Calvert Cliffs extending from Chesapeake Beach to Drum Point have been providing fossil hunters with marine animals since the 1700s. But the concentration of prehistoric remnants isn’t as great as at Carmel Church.

The site is privately owned, but Martin Marrietta Materials allows Dooley and his team to work there.

“It’s an extraordinary site,” said Brian Beatty, a paleontologist at the New York College of Osteopathic Medicine, who has worked with Dooley in identifying some of the fossils. “Carmel Church has some really very good preservation of terrestrial animals as well as the whales. On the East Coast, Carmel Church is one of those rare places to find them.”

Beatty is a bone specialist. In 2009, he and Dooley determined that jawbones on a whale from Carmel Church were broken, indicating it may have been injured while feeding along the bottom. The injury was so great that infection set in and the animal probably died a painful death, according to their paper.

The two are now kicking around some ideas as to the geological puzzle of the site and why so many bones have landed here.

“We have some partial explanations,” Dooley said with a smile. “But I’ve gotten used to being wrong.”

Niiler is a freelance writer in Chevy Chase.