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The Site

What is the official name of the site?
The Little Salt Spring Archeological and Ecological Preserve.

How large is the Little Salt Spring site?
The entire site covers approximately 111 acres in southern Sarasota County, Fla. The spring itself is about 240 feet (70 meters) in diameter — a little smaller than the length of 2 1/2 American football fields.

Scientifically speaking, what is this categorized as?
A sinkhole with anoxic spring water emanating from it; it is a very low-flow spring of the fourth magnitude.

How deep is the spring?
About 250 feet (76 meters) deep around the circumference of the bottom, but sloping up to a central depth of about 200 feet (60 meters).

How far down is the throat or dropoff?
Who discovered it?
The throat (or 'dropoff') averages 45 feet (14 meters). Early SCUBA explorer Bill Royal of Nokomis, Florida, is credited with having discovered the site in the late 1950’s.

What is the diameter of the spring at the deepest levels?
It is about 240 feet (73 meters) .

What is the shape of the spring?
It is shaped like an hourglass with the top and bottom about the same diameter, and a narrower constriction from 45 feet (14 meters) down to about 100 feet (30 meters).

What is on the bottom of the sinkhole?
Soft organic matter, like a muddy desert where there are no living organisms .

What percentage of the spring has been explored scientifically?
Only five percent, so the archaeological, paleontological, and paleoenvironnmental information it contains is vast.

Spring History

Evidence indicates that the sinkhole itself formed at the end of the last Ice Age, more than 15,000 years ago when the climate in Florida was very dry. At 14,000 calendar years ago the water level in the sinkhole was about 90 feet (27 meters) below its present level; this was a dry period in Florida's prehistory, before the Everglades or Lake Okeechobee existed.

How old is the matter at the bottom of the spring?
In 1990, scientists from UM’s Rosenstiel School took 35 feet (11 meters) long core samples of the bottom sediments and discovered that below the soft organic material lies the rocky limestone rubble from the collapsed roof that had that had fallen some 15,000-20,000 years ago.

Are there any buildings on the site?
Thankfully, there are no permanent buildings on the site, so the majority of the spring shed has been preserved. There is a small compound comprised of four trailers that are used by scientists.

Has the entire property been surveyed for other possible archeological sites?
Yes, in 2006 archeologists performed a Phase I Survey of the entire 111-acre tract and found no evidence of other substantial archeological sites, although there are scattered prehistoric remains.

Anoxic Water

What is anoxic water?
Water that has been underground for so long it loses all its dissolved oxygen.

Where does the water for Little Salt Spring come from?
Ultimately from sea water that is incorporated into the deep bedrock of Florida, thousands of' below the surface. It is heated, chemically modified, its dissolved oxygen is depleted then finally, it rises to the Earth’s surface through water vents. The cycle takes thousands of years.

Why is having an anoxic environment important?
Generally, an anoxic environment does not allow microbes and bacteria to live, so decomposition of organic material is greatly reduced. Wooden and other organic tools, as well as animals' soft tissues and bones, are preserved nearly intact in this environment.

What do you see in the spring?
As you swim down the ambient light level decreases dramatically, especially once you pass the throat of the sinkhole. At the bottom there is nearly zero light, so expensive artificial lighting is required to illuminate the way for diving scientists.


What is a sinkhole?
A circular depression in a karst region (such as Florida). It is commonly funnel shaped, and may or may not contain a flowing spring.

Why is there a ledge in this sinkhole?
At 90 feet (27 meters) there is a stratum of clay that is softer than the limestone and other carbonate rock units above and below it, so the clay stratum eroded more rapidly to create a ledge where several important archeological finds were made in the 1970’s.

Is this site similar to nearby Warm Mineral Springs?
Only insofar as they're both sinkholes. Surveys have determined that the water’s chemical compositions and the springs’ shapes vary dramatically between the two.

Recent History

How did the University of Miami receive the property?
It was donated to the University of Miami in 1982 by the now-defunct General Development Corporation (GDC) at the request of Rosenstiel School Professor Caesare Emiliani, who understood the potential importance of the site to our understanding of the earliest settlement of the Western Hemisphere.

What had the property been used for previously?
Research headed by Carl J. Clausen, a Florida pioneer in underwater archaeology, was funded by GDC from 1972 - 1979. Clausen recovered numerous prehistoric artifacts, such as a boomerang dating to about 9,500 calendar years Before Present; he also recovered late Ice Age fossils, including an extinct tortoise, and bones from a mastodon and a giant ground sloth. These were reported in SCIENCE in February 1979.

What happened once the site was handed over to the University?
Between 1983 and 2004 the property was held by the university as part of its real estate portfolio. Due to a lack of equipment and funding, no significant research was conducted at the site until 2004.

What brought back the interest in the site?
A change in leadership, both at the university and at the Rosenstiel School, brought this project to life again. The arrival of UM President Donna Shalala signaled a strong change in the direction of the university. It allowed Dean Otis Brown, Associate Dean Jay Blaire and Researcher John Gifford from the Rosenstiel School to make a strong case for the preservation and exploration of this unique and highly significant site.