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Lucy Edwards tells time by microfossils

AAAS Fellow Lucy Edwards uses a mortar and pestle to grind rock containing dinoflagellate cysts as she prepares the microfossils for microscope slides. (Photo: Carrie Madren)

The fossilized dinoflagellate cysts that are found in rock deep beneath the Earth's surface only measure about the size of a tiny pencil dot, but they tell paleontologist Lucy Edwards a lot about our groundwater.

Edwards, an AAAS fellow who works for the U.S. Geological Survey (USGS) in Reston, Va., has studied the microfossil algae cysts—the empty shells left over from one life cycle stage of the dinoflagellate—since working on her Ph.D. thesis in the mid-1970s.

"Most paleontologists study the organism for a reason. The reason for me had always been biostatigraphy—using fossils to tell the age of the rock, and using the age of the rock to make predictions about the history of the rock to help find oil, water, or salt," Edwards says.

Working as a paleontologist for USGS means constantly uncovering secrets under the Earth's surface. "You can never get bored here and you can never run out of material," she says.

That's why she's been at her job for more than three decades. "I tell people I'm the most stable person they'll ever meet," she says. "I came here straight out of graduate school, and I've had the same job for 36 years, same house for 35 years, and same husband for 20 years."

Much of Edwards' work is related to groundwater: finding out what the ages of underground rock layers can tell us about water availability for a region or community.

Geology under the coastal plain isn't tidy like a layer cake, Edwards explains. Missing layers of time could indicate a past river channel, and Edwards is helping to map those. If those channels were capped by a sediment layer that holds water in, wells tapped into those paleo-channels will produce freshwater.

In her research, Edwards helped discover the Chesapeake Bay impact crater—which hit southeastern Virginia 35 million years ago. It was in the late 1980s that she helped figure out that the jumble of rock ages was actually evidence of a meteor or comet hit.  "It wreaks havoc with the groundwater," Edwards says.

Before the crater was discovered, a colleague of Edwards would send her spot core samples to identify the ages of the layers. Once in a while, she'd get a core with five different ages mixed together. "Oh, how I chewed him out. I'd say, 'quit sending me samples like this,'" she says.

But in late '80s another co-worker drilled into 200 feet of rubble on Virginia's Eastern Shore, and the core slides revealed the same five ages she'd seen before. Researchers realized that these mixed ages were arranged in an underground circle. Seismic results from oil companies backed up the crater idea.

Edwards was among the first scientists to publish pictures of microfossils that have been affected by the high temperatures, shock waves, earthquakes, and tsunamis created by the impact. She's found specimens with processes—protruding parts—that are blown off, hollow, melted, or folded like a fortune cookie. "They are wild, a complete array of very strangely preserved things that few people in the world have ever seen," says Edwards, who finds weekend fun by kayaking near her vacation home on the Shenandoah River.

Recently, a STEM high school student group visited USGS in Reston and piled into her lab for an impact crater simulation of sorts as they learned about a paleontologist's work. They tossed a mandarin orange (meteor) onto a pile of whipped cream (rock) with layers of sprinkles (dinoflagellates). "You get this really big splatter of a crater—then we get out the rocks and discuss what an impact crater looks like," says Edwards, who also frequents career days and presents the fun of geology to summer camps. "Kids are natural scientists."

Paleontology first sparked her own interest as a kid when someone gave her a dinosaur model. While taking geology courses in college, she realized microfossils were a good fit because she's mathematically oriented and wanted hundreds of specimens at her fingertips. With microfossils, 10,000 slides easily fit in an office.

Today, her office has boxes containing millions of specimens. Her lab contains boxful upon boxful of long rock cores with the diameter of a tennis ball—drilled from around the mid-Atlantic by a diamond-tipped drill.

It's there where she and her assistant turn chunks of rock into specimens for microscope slides. Microfossils are separated from the rock through mortar and pestle pulverizing, using hydrochloric and hydrofluoric acid washes to eat away at the rock and a centrifuge to concentrate the dinoflagellate cysts. The end result is a tiny liquid-filled vial. She swirls one of the vials to reveal a flurry of black specks that came from about 40 grams of rock (or, roughly, half a stick of butter, she says).

Edwards has not only named one genus and five species, but also has a genus of dinoflagellate named after her—Edwardsiella.

While working in the north Atlantic in the 1980s, she found eight mystery specimens—something that no one had ever seen, but it wasn't enough to create a new genus. Then in the early 1990s, a Mediterranean researcher found many more and named it for Edwards. Edwardsiella has just one species that has six spines including one broken spine. "I named it sexispinosa," she says. "But you can imagine with these high school kids, I tell them, 'if you're really lucky, someone will name a sexy fossil after you.'"