Shark Teeth Haven beneath South Alabama's Sepulga River: "among most fossil-rich places in
By Ben Raines | braines@al.com AL.com
series /series Aka Story Package gallery-preview /gallery-preview Aka Secondary Package Evergreen, AL
Ten feet underwater, the gurgle from a rushing waterfall filling your ears as you fight to keep from getting washed downstream by the heavy current, the shark teeth are a startling sight.
Glistening on the pebble-strewn bottom, in shades ranging from deep blue to black, the teeth are everywhere you look. The largest are nearly two inches long, and the smallest so tiny you can barely pick them up.
This particular spot, perhaps 20 feet long, sits below a small Sepulga River waterfall near Evergreen, Alabama. It ranks among the most fossil-rich places in the United States.
"It's pretty insanely good. You probably can collect something on the order of 500 shark teeth an hour," said Martin Becker, a paleontologist from William Paterson University in New Jersey, bobbing at the river's edge in scuba gear. "That rates up there, after 30 years of shark tooth collecting, with some of the best spots I've ever been."
The teeth date to the Eocene era, about 40 million years ago, a time when much of Alabama was buried beneath an ancient ocean. The shark teeth, along with teeth from other types of fish, were trapped in marine sediments as they fell from the mouths of the animals, or when the creatures died and sank to the seafloor. Entombed for millennia in those ancient seafloor sediments, the teeth end up on the bottom of the modern river as the rushing current eats away at the rock-like layer of marine clay where they were deposited 40 million years ago.
Among locals, the Sepulga is fairly well known as a place to find shark teeth. In the summertime, people wade the shallows, picking up handfuls of gravel and searching for teeth in the mix of sand and small rocks. You can find a fair number of teeth that way, perhaps several dozen a day.
But to really hit the jackpot, you must find one of the places where the teeth are actively being washed out of the ancient sediments. This particular waterfall is such a place, but you would never know it paddling past in a canoe. You would float right over the incredible scene arrayed on the river bottom, never imagining there could be so many teeth down below.
Until you've seen it with your own eyes, it is hard to believe how many teeth litter the bottom. Study the gravel collected below the falls for a moment, and you see three or four teeth. As you pick those up, you notice six or seven more. After picking those up, run your hand through the gravel and you find five or six more. Look to your right, and you see a big one behind a rock. Reaching for it, you see a half dozen more teeth.
But be on guard, more modern artifacts are present as well. Among the unexpected items found below the fall was a fully loaded automatic pistol, which probably fell out of someone's canoe after they turned over in the rough current.
The other amazing thing about a spot like the waterfall is the condition the teeth are in. The teeth found elsewhere in the river are in very good shape, mostly whole teeth and easy to recognize by species. But the teeth at the waterfall verge on being almost perfect, as sharp as they were when they were in the shark's mouth. That's because the waterfall teeth haven't tumbled down the river for months or years, perpetually being sanded and smoothed by their interaction with gravel and sand. Instead, the teeth below the fall are still so sharp you can feel the serrations along their edges. They are sharp enough to slice a tomato with.
Wearing scuba gear and an extra 15 pounds of lead to help holdfast in the current, Becker, fellow paleontologist Harry Maisch with Brooklyn College, and I spent a few hours underwater just before Halloween. The river was a chilly 59 degrees, necessitating wetsuits.
"We're on the order of 90 miles inland, and we are scuba diving under a modern waterfall and finding 45-million-year-old shark teeth that are sitting happily on the bottom in the river gravel. How cool is that," Becker said. "This place would have kind of been a shallow shoreline patch reef, back in the middle Eocene... It wouldn't really be much different than what you would expect if you went out of Gulf Shores today, what you would see. We're just a substantial distance away from the nearest marine environment."
While Becker is underwater, Maisch sifts through a bucket of sediment he hauled up, looking for rarer prizes than the shark teeth. He is hunting for signs of the other creatures that lived in this ancient ocean.
"I'm looking for signs of the fish that were here. A lot of them, or their families, are still around today," Maisch said. He shows off a collection of teeth and body parts that clearly did not come out of a shark's mouth. Some are rounded points, others flat plates.
"I've found mackerel teeth, a box fish, barracuda, a bonefish, tarpon, sting ray teeth. I also found a horn coral," Maisch said. Holding up what looks like a tiny jigsaw blade, he said, "This little spiked thing is the pectoral fin out of a catfish."
Becker said the spot was unique and rare. To find such a concentration of teeth below the waterfall most likely means the current is eroding an ancient lag deposit, or a spot where physical forces, like waves or river currents, pushed the fossils together in a thick layer. He pointed to sandbars in a river, where gravel collects, or spots on modern beaches where shells pile up, as examples of lag deposits.
As for why there are so many shark teeth compared to teeth from other fish species, Becker pointed to the way shark mouths work, with a sort of conveyor belt of new teeth rolling up from the gums, ready to take the place of teeth lost during feeding.
"You ever see those black tip shark migrations along Florida and Alabama? You look at the aerial footage of that, those sharks are within 100 yards of the beach. The functional tooth position in a shark is lost every seven to ten days. And there are on the order of 30 tooth files per shark, so I'm thinking when they are hanging around like that, they are losing teeth like crazy," Becker said. "Each shark is losing 30 teeth a week, for its entire life. I think if you went snorkeling out there after that aggregation, you'd probably get a bunch of teeth. Of course you'd probably want to make sure the migration is passed before you swam out in the middle of all those sharks."
Becker said geologic forces have worked to push all the teeth seen on the Sepulga into dense pockets. The waterfall just happens to have cut through one of those pockets.
"You have the contact between the two geologic formations, and you have river erosion across a waterfall system. This area below the waterfall is just serving as the catch basin," Becker said. "This is why this particular spot along this waterfall happens to be as good as it is. It's a combination of ancient and modern processes that are doing us a favor. A big one. The river is doing all the work for us, and giving up all these treasures from the past."
To read more about Alabama fossils, click on this story about Alabama's role in Darwin's theory of evolution.
Follow Ben Raines as he explores Alabama's natural wonders on Facebook, or Twitter at Ben H. Raines.