March/April 2016"Dem Bones, Dem Bones"by Joey Frazier
Recreational divers immerse themselves in natural history to find fossils and adventure on the bottom of South Carolina's blackwater rivers. But how did the fossils get there in the first place?
South Carolina's Lowcountry boasts popular tourist destinations with scenic views and a variety of recreational opportunities at nearly every turn. It also offers up its own share of mystery. From moss draped live oaks to murky blackwater rivers, the Lowcountry conjures tales of heroic deeds and more than a few legends of famous - maybe even infamous - figures who contributed to the curious reputation of that region. More perplexing still, local mysteries don't always begin or end in folklore. For centuries, scientists have studied, theorized and otherwise tried to explain the sometimes secretive nature of the coastal plain, only to find themselves with more questions than answers as they uncover the fossilized past only a few feet below the pluff mud or at the bottom of a blackwater river.
"It's like holding a piece of history in your hands," says Catherine Sawyer, a recreational diver who regularly descends the relatively shallow depths of the Cooper and other coastal plain rivers in search of prehistoric fossils.
Sawyer has always liked the water, but she first became interested in diving as a means to collect fossils or artifacts.
"Growing up, we would go to Edisto for summer vacations," she says. "On one of those trips, when I was in the sixth grade, I saw some boys with a spear point they found snorkeling. I've been hooked ever since."
Of course recreational diving is not a sport you can learn on your own at the old swimming hole. To become a certified diver, Sawyer took classes at a local dive shop, a basic class and another more advanced session especially for blackwater river diving.
"You need the advanced class because visibility is very limited in the Cooper River," says Sawyer. She further explains that divers should never go into the water alone. Besides being up to eighty feet beneath the surface and breathing air from a regulator and tank, divers must consider other hazards such as swift currents, alligators, motor boats, and possibly even sharks, depending on your proximity to the ocean.
After dive training, Sawyer says she went on chartered dive trips to search for fossils and attended local dive shop-sponsored social events to meet other divers. At one such event, she met Jimmy Armstrong.
"I was diving pretty regularly in the Cooper River with my dive partner," recalls Armstrong, "but I wanted to dive some of the smaller rivers, too. Nobody wanted to do that, and I know better than to go diving alone."
"I just wanted to dive," adds Sawyer, "it didn't matter where."
Sawyer and Armstrong started diving in other Lowcountry rivers with limited success, but after doing some research, and with a little trial and error, they made some good discoveries.
"Once we started finding stuff, other divers wanted to come go with us," she said.
The duo dive regularly in the warm seasons, and they often find fossil remains such as shark teeth, mastodon teeth, whale bones, horse teeth, glyptodont scales and much more. The variety tells the story of fauna we might not expect to be indigenous to South Carolina. While it is exciting to make the discoveries and bring a piece of little known history to the surface, the real question is this: why are these bones and teeth still around after as much as 40 million years? The answer to that question links South Carolina's natural resources with an early mining industry that briefly flourished in the Lowcountry.
DNR geologist Dr. Will Doar explains how these fossils were created: "It comes from a coastal saltwater environment where you have a massive nutrient load coming from deep ocean water," says Doar. "This is a really rich bio-environment that sinks out of reach of the creatures that might use it as food source and into an oxygen poor environment."
Ocean currents eventually deposited this material on the floor of a shallow sea that once covered South Carolina's coastal plain, creating a nutrient dense material on the sea bed.
"If you drop the oxygen level low enough," says Doar, "you form various phosphorous-rich materials. What happens is things like iron, phosphorous and manganese can't be held in solution of the ocean water any longer and they precipitate out. It's like high school chemistry, you mix the right things together and solids fall out of liquids. If the oxygen level gets as low as zero, phosphorous oxide precipitates out, and apparently that has happened quite a few times on our continental slope."
As these minerals can no longer remain in a liquid form, they crystalize on the hard surfaces they come in contact with on the ocean floor, such as teeth and bones, or rocks and gravels according to Doar. Over time - in this case as much as 40 million years - the bones and teeth become fossilized by these minerals, preserving the bones and teeth of ancient sea and land creatures that ended up on the bottom of the shallow sea.
"It builds up over time like a varnish," Doar says, "but only tenths of a millimeter at a time. Think of varnishing a table. That is what this stuff is doing in very thin layers - maybe seasonally, maybe every ten years - whenever the oxygen level gets to zero."
As the ancient sea level repeatedly rose and fell, what we now know as our coastal plain was exposed and the fossils were exposed and reburied numerous times in sediments from the ocean by winding Lowcountry river banks. In the 1700s, when planters began farming large plantations along the river banks, they started finding deposits of smelly black rocks and gravel mixed with something unexpected - hardened animal remains. Amateur scientists and naturalists collected the unusual fossils, and early geologists even began speculating about the age of the material.
Alchemists also became interested in the unusual geology of South Carolina. Along with other scientists, they began doing assasys of the local rocks and gravels to discern the mineral components for a variety of reasons. Some hoped to find precious metals, others with theological backgrounds hoped to use the fossils as evidence of the great flood from Genesis, and some hoped to find ways to replenish soils exhausted by monoculture and over-planting.
One such agronomist, a tobacco planter named Edmund Ruffin, came to South Carolina from Virginia during the 1840s to study the "marls" found below the surface of the Lowcountry for their potential use as fertilizers. Marl is term used to describe a sort of shell hash containing calcium carbonate, and Ruffin thought the answer to revitalizing soils lay in South Carolina's vast marl beds. Ruffin wrote an agricultural survey of the state, but he failed to see the value of the phosphate rocks described in his work. Other scientists eventually did, however, and for a time, phosphate mining would become a major economic driver for the Palmetto State.
For his work in agronomy, Edmund Ruffin is known today as the "father of soil science" (in the United States, at least), but he's even more infamous, perhaps, for his role as one of the "fire eaters," a group of southern leaders who advocted strongly for the secession of the southern states. Legend says Ruffin may have fired one of the first shots during the attack on Fort Sumter, thereby starting the Civil War.
Planters would dig the phosphate-rich gravel from shallow pits on their land and spread it on the fields to enhance crop production, explains Doar. Very soon, industrial-minded geologists found ways to extract the phosphate minerals from the rocks to make fertilizer.
"Scientists found a commercial method using sulfuric acid to liberate the phosphorous from the rock, producing phosphoric acid," says Doar. "This was called 'washing' the phosphate rock. Another process then left the phosphorous as a white solid which could be refined into phosphate fertilizers."
Among those scientist and early phosphate mine owners was Francis Holmes. Holmes had done geological research at the College of Charleston and had worked under South Carolina State Geologist Michael Tuomey. Both were contemporaries of Edmund Ruffin.
As the Civil War ended, it appeared that phosphate mining would be the industry to bring economic prosperity back to the Palmetto State, as agriculture on the great plantations failed to be revitalized. Unfortunately, the boom in phosphate mining was short-lived, and as the industry trailed off and disappeared in the early 20th century, the strip mining not only left scars on the land, but a road map of sorts that recreational divers would one day use to find likely fossil bearing dive sites.
Catherine Sawyer enjoys researching possible dive sites by reading early history texts, scientific papers such as geological survey records, and even historic diaries.
"Jimmy likes to research old maps, and he has the boat and dive expertise," Sawyer says, "but I usually do a lot of reading to help research for our dive sites." Both are members of the South Carolina Gem and Mineral Society and they also participate in other clubs within the local diving community.
"If you stay in touch with other divers, you can get good tips on places to dive," Armstrong says.
Of course both are quick to recommend to folks interested in their hobby that they seek out professional diver training for the obvious safety reasons. But even once you are trained on proper diving techniques, you can't just go out and start collecting; hobby divers who want to recover fossils or artifacts must have a hobby divers' license from the South Carolina Institute of Archaeology and Anthropology. The cost is $5 for a six month license or $18 for a two-year license, and you must submit quarterly reports, whether you made a dive or not. The average cost to get started in this hobby, including dive lessons and basic gear is approximately $2,500, according to Sawyer. Like most hobbies, you can spend as much as your budget allows, and of course, you still need a boat.
"It's murky in those rivers, the currents can be tricky and visibility is never better than a foot or so in front of your mask," Sawyer said. "But I keep coming back because you just never know what you might find down there."