In the pitch-black depths of an isolated North Port spring sits a silt-covered ledge that is revealing secrets about a prehistoric nomadic people, secrets held in murky silence for 100 centuries.
Now, with diving gear and artifact-collecting bags, archaeologists with the University of Miami and The Florida Aquarium are sweeping away the muck and uncovering that distant past.
This stuff could be as old as 13,000 years old, when wandering tribes traversed Florida. Their travels included stopovers at what is now known as Little Salt Spring, 90 minutes south of Tampa.
Artifacts are delicately uncovered from a ledge 90 feet below the surface, archaeologists say, offering up glimpses of what life was like for who is believed to have been Florida's first residents.
John Gifford, an underwater archaeologist with UM's Rosenstiel School of Marine and Atmospheric Science along with aquarium divers are working together to gather the artifacts.
"In the last ice age, between about 10,000 and 13,000 years ago, the water level was 90 feet lower then than it is today," Gifford said. "It's generally thought that along that early beach area, those early humans left their tools or whatever artifacts they found at that site."
The site has been under excavation by scientists sporadically over the past three years, and only about 6 percent of the submerged ledge has been scoured.
"Little Salt Spring," Gifford said, "is where we have at least a fighting chance at finding some traces of human activity say 9,000 or 10,000 years ago."
The work is painstaking and somewhat dangerous but worth the effort, archaeologists say. Little Salt Spring, they say, is one of the most important archaeological sites in the state, and perhaps the nation, for its wealth of information about the dawn of civilization here in Florida.
The sinkhole's water chemistry and temperature have helped to create a one-of-a-kind, prehistoric submerged site where late Paleo-Indian and Archaic artifacts are unusually well preserved.
"Our research has only begun to scratch the surface of what this site may reveal to us," Gifford says in a statement released this week. "The anoxic (absence of oxygen) environment at the bottom of the spring does not allow microbes and bacteria to live, so decomposition of organic material deposited there thousands of years ago is greatly reduced. Wooden and other organic tools, as well as animals' soft tissues and bones, are preserved nearly intact in this unique environment."
In 2005, Gifford and his graduate students discovered two exceptional Archaic artifacts - a greenstone pendant and a carved stone that appears to be part of a spear thrower - estimated to be approximately 7,000 years old.
The site was donated to UM in 1982. Archaeologists had suspected since the 1950s that it was a treasure trove of artifacts.
Little Salt Spring dips more than 200 feet into the ground and was frequented by nomadic, prehistoric people, scientists say. They hunted animals such mastodons and giant ground sloths, which are extinct. The first major find, more than three decades ago, was a giant tortoise shell about 12,000 years old that appeared to have been pierced by a spear.
The diving is dangerous. Besides the occasional alligator that slips through the water, researchers drop nearly 100 feet, where sunlight fades to black and the age-old silt on the ledge gets stirred by the slightest movement, cutting visibility to nearly zero. Divers must complete a 100-hour course in scientific diving to make the plunges.
Thursday marked the ninth of 10 days of diving during this excursion. Pulled to the surface was what appeared to be a spear tip and carved piece of wood. Finding stone artifacts isn't likely, as around Florida then, as now, there aren't a lot of hard rocks. So, most of the artifacts are fossilized remains of living things and wooden tools.
"There just wasn't very much good stone in Florida to make tools," Gifford said, "so these early people - the Paleo-Indians - would use a lot of wood."