There’s something buried in Sea Pines that archaeologists say is more than 4,000 years old — and it has long stumped them.

Known as an Indian shell ring and located in the Sea Pines Forest Preserve, the lumpy mounds forming a circle, leftover from ancient Native Americans depositing shellfish shells, have withstood the test of time, but not a lot is known about these rings.

Were they where people lived? Were they used for ceremonies?

Only a few things are certain about the Sea Pines Indian Shell Ring, according to Matt Sanger, assistant professor of anthropology and director of the public archaeology program at Binghamton University in New York. The ring was not used for defense; it was not used for burials; and it was not used for holding water, he said.

“No one really knows what these rings were used for,” Sanger said. “That’s the million-dollar question.”

That question is what he and his group of graduate students are trying to figure out. Their work began Tuesday in the Sea Pines Forest Preserve with digging up sand that was placed over their old dig site.

This is the second year the group has come to excavate and study the site — one of about 50 such rings in the southeastern U.S., Sanger said. The ring is small compared to others, at about 120 feet in diameter and 3 feet high. It cannot be traced to a specific tribe, but it likely was used by those native to the area, such as the Cherokee or Creek tribes, Sanger said.

Until Aug. 4, about 10 people will be working at the site from 9 a.m. to 2 p.m. six days a week, digging up the earth and carefully screening it to find “features,” or remnants of past activity.

Last year, the team found plenty of artifacts. Perhaps the most significant find was a broken pot with remnants of food still inside, apparent by shells and bones, Sanger said, adding it was as if someone had dropped it on the ground and never picked it up.

“This ring is really unique in its level of preservation,” he said.

Caleb and Kieran Kelly, Bluffton High School students, are volunteering a second year at the site. A few notable artifacts from the last dig, they said, were a hand-sized arrow point, and a carved bone, possibly used as a hair pin.

Sanger said it’s unknown when the Sea Pines Indian Shell Ring was discovered, but before his team came down last year, no archaeologists had been to the site since the 1960s or 1970s. Methods, tools and equipment have changed, which means researchers today can potentially learn more, he said.

The Green's Shell Enclosure Heritage Preserve on Squire Pope Road is another shell ring on the island. Dylan Davis, a Binghamton graduate student helping with the shell ring excavation in Sea Pines, said by using LiDAR, a remote sensing method that allows someone to examine the earth’s surface, he has found about 40 potential shell rings along the coastal edges of Beaufort County.

After unearthing last year’s Sea Pines site inside the edge of the shell ring, the team will dig in the “plaza,” or center of the circle. The goal is to have a “light footprint” Sanger said, explaining that every move is deliberate and carefully done so that the site is not damaged.

Visitors and volunteers are welcome to stop by the site beginning Monday, said Katie Seeber, field director and a doctoral student of Sanger. Teaching staff from the Coastal Discovery Museum will be out next week to answer questions about the site.

In a few weeks, there will be a “public day” in which there will be limited excavation and visitors can come to the site to learn about the ring and take part in some fun, Sanger said. Last year, there was a spear-throwing contest, and Caleb Kelly taught visitors how to carve arrow heads.

The team encourages visitors to stop by. But “there’s no hidden treasure,” Sanger said, noting visitors should not take it upon themselves to excavate the site now or in the future.