フロリダのＳｉｎｋ　Ｈｏｌｅ　

先日お伝えしたフロリダのＳｉｎｋ　Ｈｏｌｅ　（石灰岩台地に見られる陥没穴）での発掘について。　　発掘はボランティアなでも使って行っています。　潜水病を防ぐためのセーフストップなどおもに発掘の様子についていろいろと詳しく書かれています。まだ調査が始まったばかりなので見つかった遺物などについては詳しくわかっていません。この遺跡は２０年以上も前から知られてはいましたが、今まで誰も水底面のサイトマップを作ったことがなく、これから本格的にプロジェクトを進めていきます。遺物は１２０００年ほど前と思われ、そのほかに植物、髪の毛、ロープなど様々な種類が発見されています。

Archaeologists plumb depths of ancient spring
Team from University of Miami, Florida Aquarium begin to map bottom of little-examined North Port site
By LIZ BABIARZ
liz.babiarz@heraldtribune.com
NORTH PORT — Watching Casey Coy and Rick Gomez prepare to dive into Little Salt Spring is like observing a pilot getting ready for takeoff.

Step by step, the two divers painstakingly review their equipment, instruments and procedures before taking the plunge into the prehistoric underwater site.

They say such meticulousness is imperative: When you’re 242 feet underwater, there’s no time for mistakes or miscommunication.

“Is it dangerous? It could be, if we didn’t go through the checks,” said Gomez, diving safety officer for the University of Miami.

Coy, who works for the Florida Aquarium, and Gomez are the first divers to explore the bottom of Little Salt Spring, a sinkhole in North Port that contains wooden stakes, stone tools and other artifacts used by Florida’s earliest inhabitants, the Paleoindians.

While researchers from the University of Miami, led by John Gifford, have conducted several explorations of shallow parts of the spring over the past 20 years, no one has ever mapped out the bottom.

It’s taken Coy and Gomez many years to learn how to use the equipment and the technology needed to conquer this deep and dark dive.

Wearing four cylinders of blended gases that allow them to stay underwater longer and carrying high-intensity flashlights to guide their way, Coy and Gomez completed nine trips to the floor of the hourglass-shaped spring last week.

They hope the data they collect there will help answer basic questions about the spring: Where is the water coming from? What caused the spring to develop thousands of years ago? Why does the water act like formaldehyde, preserving organic artifacts from decomposition?

The sliver of the sinkhole that has been studied so far has yielded ancient stones and tools as well as the bones of prehistoric animals such as mastodons and mammoths. But most importantly, archeologists have recovered organic matter — plant remains, hair, brain tissue and rope — that would have deteriorated on land.

Some of the artifacts are 12,000 years old, when archeologists believe the spring was an oasis that attracted seasonal hunters and gatherers. Over time, the water table of the spring rose, protecting the remains of prehistoric man in the underwater sediment.

Because of this, Little Salt Spring is considered one of the most significant archeological sites in North America.

As the University of Miami and Florida Aquarium team looks for clues for clues about the past, they’re also trying to see if man’s activities today are affecting the spring and the treasures it holds.

“We are becoming worried all the recent development in the city may affect the quality of water in the spring,” said Gifford, the project director and a University Miami professor.

Coy and Gomez, during their dives last week, installed monitoring equipment to detect any changes in the water quality over time. The concern is chemicals or gases could be seeping into the spring, speeding up the deterioration of the artifacts.

If water degradation is found in Little Salt Spring, it could illuminate problems in other ground-water sources.

“If we’re getting a deterioration of water quality, it will be a wake-up call for water quality in general,” said Steven Koski, resident archeologist at Little Salt Spring.

But it could be several years before that information is known. The research team is just now trying to identify the spring’s source.

During their dives, Coy and Gomez found three vents where warm water could be flowing into the spring. Some of the vents were covered with a white, film-like material, which they suspect is a type of sulfur bacteria. They are now studying the samples of the white material and the water to see if it will lend clues to the spring’s source.

Diving to the bottom of a 242-foot sinkhole is no easy task, Coy and Gomez say.

While it takes them two or three minutes to get down to the base, Coy and Gomez spend 60 to 90 minutes returning to the surface. They need to come up slowly to prevent decompression sickness, caused when gases, built up in the blood from breathing them under pressure, form bubbles that can lead to unconsciousness and even death.

To prevent too much gas from entering their blood, Coy and Gomez stay on the bottom for only 25 to 30 minutes, which isn’t a lot of time to navigate the black abyss.

“It’s very disorienting,” Coy said. “It’s pitch black with no sunlight.”

Along with the exploration of the bottom, underwater archeologists — Koski of Little Salt Spring and University of Miami Dive Coordinator Mike Terrell — are continuing their investigation of the basin of the spring, a project that’s been ongoing since 1992.

About 40 feet down on the ledge, scientists have found six wooden stakes that are 9,000 years old.

“We’re trying to determine what their function may be, how long ago they were talled, what activities they represent and how long they were in use,” Koski said.

Most of the divers and other research team members from the Florida Aquarium and the University of Miami are volunteers. They will be back in June to continue their work on these projects, which could take many years to complete.

For the past 20 years, the University of Miami, which acquired the 112-acre site from General Development Corp. in 1982, has conducted underwater excavations of the Little Salt Spring sinkhole, but only 5 percent has been studied.

“It is one of the most important sites in the United States, and we’re trying to understand it. But we haven’t gotten very far because there isn’t funding available,” Gifford said. “Archeological research is a low priority with the federal government.”

Even as they are just getting started uncovering what is in the spring, development pressures threaten land around the site.

Government and nonprofit groups have been working together to preserve land adjacent to Little Salt Spring that contains the remains of an ancient village and burial ground.

That project took a major step forward this month when the North Port Commission committed $25,000 toward the preservation. Sarasota County is also working to acquire six properties near the spring that are privately owned.

The goal is to have an environmental park with boardwalks and pavilions around the spring and this 5-acre parcel, north of Price Boulevard.

“The park will be left in its natural setting,” Koski said. “It will have informational signs and educational kiosks showing the educational and cultural components of the spring.”

引用元：http://www.newscoast.com/apps/pbcs.dll/article?AID=/20060119/NEWS/601190374