Living Laboratory

For more than two decades, Georgia Southern University researchers Gale Bishop, Fred Rich and Kelly Vance have traveled by boat to discover the long-ago history of one of coastal Georgia’s barrier islands. Along with a team of geologists, archaeologists and biologists from around the country, researchers have unearthed disappearing plant species, studied the coastal sediments and groundwater, addressed the topic of coastal erosion and saved loggerhead sea turtles on St. Catherines Island.

Inhabited by the Guale Indians in the 1500s and the site of the Mission Santa Catalina de Guale, the 10-mile-long island has a rich history that once included ownership by Button Gwinnett, one of the signers of the Declaration of Independence. St. Catherines is now a protective haven for endangered species and groups of researchers, said Bishop, professor emeritus of geology at Georgia Southern and director/founder of the island’s Sea Turtle program, which has safely relocated and conserved sea turtle nests for the past 20 years.

“Research has been an important part of the island’s history for a very long time. One of Georgia Southern’s early researchers was Dr. Jim Oliver, who studied ticks and mites on the island. But Bud Rollins and David Hurst Thomas have both been doing research here since the early ’70s,” he said.

Bishop has teamed up with Thomas, curator of anthropology at the American Museum of Natural History, and Rollins, professor emeritus of geology at the University of Pittsburgh, to co-author Geoarchaeology of St. Catherine’s Island. Geoarchaeology is the result of papers presented by 20 researchers at the Fourth Caldwell Conference detailing their studies over the years.

“Geoarchaeology explores the geological history of St. Catherines Island and its interactions with early human habitation as North America was colonized by Native Americans, Europeans and African Americans – it preserves evidence of the habitats that these waves of diverse peoples lived in,” said Bishop.

Rich and Vance also co-authored several chapters in Geoarchaeology, and have actively conducted research on the island for many years.

Rich has discovered dozens of ancient plant species on the island, some that have vanished, because of climate and sea level changes. “The plant fossils tell in fact that the island’s climate has changed,” he said. “Spruce and hemlock are some of the species that don’t grow here, or even in the region anymore. Coastal Georgia once had a much cooler climate in the past, more like that of Wisconsin,” he said.

Rich’s sediment samples gave him the opportunity to reconstruct the ancient plant community of the island. For example, peat deposits found on the beach side of the island were originally located in the marsh, which speaks to a change in sea level and erosion. “The sea level has been rising steadily for the past 14,000 years, and this contributes to the movement of the shore. What was once marsh is now the Atlantic Ocean,” he said.

Sea level changes also play a significant role in Vance’s research. For the past six years, he has worked with Bishop using Ground Penetrating Radar (GPR) to determine the shallow subsurface structure of St. Catherines. This work discovered sag structures that are typically produced by collapse of caverns deep in the ground. The location of the sags correspond to the site of former fresh water marshes and artesian springs on the island. “There used to be huge fresh water springs and marshes in the interior section of the island in colonial times,” said Vance. “The caverns that collapsed are probably in the limestone of the Floridan Aquifer – 400 feet below the bottom of the sags. Cavern formation concentrates along fractures and faults; the same fractures provided conduits for water from the Floridan Aquifer to reach the surface as artesian springs,” said Vance. Industrialization along the coast has dramatically lowered the artesian pressure surface and springs no longer flow on the island. Vance is concerned about the threat to the Floridan Aquifer as sea level rises.

“With the rise in sea level, there is a danger that the salt water may move laterally through the shallow aquifers and into the conduits associated with the sag structures to enter the Floridan Aquifer. We could have salt water mixing in with fresh water. All of our coastal areas are supplied by water from the Floridan Aquifer, and the continued intrusion of salt water would eventually lead to loss of our greatest fresh water resource,” said Vance. With the large human population on the coast, other islands that would be affected include Ossabaw, Wassaw, Blackbeard, Sapelo, Sea Island and St. Simons as well as mainland communities.

In order to determine the possibility of salt water entering the Floridan Aquifer through the shallow aquifer, Vance, colleagues and several undergraduate students have entered the next phase of their research using vibracoring. During this process, sediment samples are collected after drilling approximately 20-30 feet underground. Vance revealed that after studying the core samples, they will have a better understanding of the shallow water table aquifer to determine the potential for communication with the deep Floridan Aquifer. Vance is currently working with hydrogeologist Jim Reichard, environmental geologist and alumnus Brian Meyer and undergraduate geology major Brock Nelson to install shallow groundwater wells on the island.

As for further geoarchaeological research on the island, Bishop expects the studies and evaluations to strengthen and continue. “We host a great number of research programs on the island and we are even now collaborating on a new book called Research, Conservation and Education, the motto of the St. Catherines Island Foundation,” he said.

 
 
St. Catherines Island is administered through a non-profit 501(C)3 Foundation for Research, Conservation and Education in Coastal Georgia. Geoarchaeology of St. Catherines Island, Georgia was supported and published by the American Museum of Natural History, New York, NY as Anthropological Paper #94, available for purchase by print copies or by open access download of pdf copies from the Digital Library of the AMNH.