Warm Mineral Springs (spring)

Warm Mineral Springs
U.S. National Register of Historic Places
Warm Mineral Springs, North Port, Florida
Location:	North Port, Florida
Coordinates:	27°3′32″N 82°15′39″W
Governing body:	Private
NRHP Reference#:	77000408
Added to NRHP:	November 28, 1977

The Warm Mineral Springs (also known as Warm Salt Springs) is a water-filled sinkhole located in North Port, Florida, a mile north of U.S. 41. The primary water supply is a spring vent deep beneath the pool's water surface. The site has functioned as a spa since the 1960s, and is an important geological and archaeological site. It was added to the U.S. National Register of Historic Places on November 28, 1977.

Warm Mineral Springs is the only warm water mineral spring in the State of Florida.

Geology

Warm Mineral Springs is a sinkhole formed in carbonate rock by the collapse of the roof of a cavern 30,000 years ago. The land surrounding the sinkhole is flat, and about 3 metres (10 ft) above mean sea level. The circular opening of the sinkhole at the current water level is 72 metres (236 ft) across. The sinkhole is 70 metres (230 ft) deep, and is shaped roughly like a an hourglass. The opening narrows to 48 metres (157 ft) across a few meters below the surface of the water. About 13 metres (43 ft) below the surface the opening widens for a short space, forming a ledge under an overhang. The opening narrows to 38 metres (125 ft) across at 30 metres (98 ft) below the surface, and then opens up again, reaching 72 metres (236 ft) across at the bottom of the sinkhole. Debris from the collapsed roof and sides of the sink, and other material that has fallen into the sink, forms a large cone at the bottom, rising to 38 metres (125 ft) below the surface of the water.

The environment in Florida during the Pleistocene period was much different than today. Due to the enormous amount of water frozen in ice sheets during the last glacial period, the sea level was at least 100 metres (330 ft) lower than it is today. Florida had about twice the land area of today, its water table was much lower, and its climate was cooler and much drier. There were few running rivers or springs in the part of Florida that is now above sea level. The few water sources in the interior of Florida were rain-fed lakes and water holes perched on relatively impervious deposits of marl and deep sinkholes partially filled by springs, such as Warm Mineral Springs. The water level in the sinkhole 12,000 years ago was about 30 metres (98 ft) lower that it is today. Dripstone (stalactites and stalagmites) has formed on the walls of Warm Mineral Springs down to about 30 metres (98 ft) below the present level of the water, indicating that the water level in the sinkhole was at least low long enough for the dripstone to form.

Although there are many small freshwater springs in the walls of the sinkhole, the primary source is a vent 63 metres (207 ft) below the surface of the water which discharges an estimated 20,000,000 U.S. gallons (76,000,000 L) a day of warm [30 °C (86 °F)] mineralized water. The water has a high content of dissolved chloride (1,600 to 1,700 milligrams per liter [mg/l]) and hydrogen sulfide (9,200 to 9,600 mg/l), and essentially no dissolved oxygen. The source of the water is uncertain. The water enters the sinkhole at the 63 metres (207 ft) level from a conduit that extends with several turns to a point 53 metres (174 ft) from the entrance and 67 metres (220 ft) below the surface of the water. The conduit has an elliptical shape, about 1 metre (3.3 ft) high by 3 metres (9.8 ft) wide, for much of its length. At the far end the conduit opens up into two small caverns. Most of the flow appears to enter through the floor of the last cavern. Between 5,000,000 U.S. gallons (19,000,000 L) and 7,000,000 U.S. gallons (26,000,000 L) a day overflows from the sinkhole.

History

In the late 1950s William Royal and other scuba divers found artifacts and human bones from at least seven individuals in Warm Mineral Springs. A partially burned log found in association with some of the human bones was radiocarbon dated to about 10,000 years ago. If the bones were the same age as the log, then the bones were the oldest known evidence of human occupation in Florida at the time. Bone artifacts recovered in association with the human bones were described as of "Archaic period in the Americas-type". The bones and artifacts were apparently deposited above the water level in the sinkhole at the time.

One skull recovered from under sediment about 40 feet (12 m) under the present water level in the sinkhole contained organic matter. Hospital medical staff who examined the contents of the skull observed that it looked like a brain. One doctor reported that he could distinguish the cerebellum from pieces of the cerebrum. A section through the material also appeared to show grey and white matter. Tests were consistent with the material being brain matter, but no cellular structure could be observed.

The property, which was privately owned, was developed into a spa in the 60s. Unrestricted access resulted in scuba divers removing human bones and artifacts and stalactites and stalagmites as souvenirs and for sale. Almost all artifacts had been removed from the sinkhole before scientific exploration began. The property owners started restricting access to the sinkhole and trying to prevent looting and vandalism in the 1970s.

Wilburn Cockrell, an archaeologist at Florida State University, starting working at Warm Mineral Springs in 1972. This work lead to the private owner's protecting the site due to its archaeological significance. Archaeological exploration of the sinkhole paused in 1975, resuming in 1984. Phase II of the project found evidence of tool making by early man. There is evidence of the Paleo-Indian and Archaic cultures.

Wilburn Cockrell has described Warm Mineral Springs as the "burial ground" for the prehistoric residential community at nearby Little Salt Spring. In a 1988 interview Cockrell stated that the remains of more than 20 Paleoindians have been found in the sinkhole, including some radiocarbon dated to 12,000 years ago. The archaeologists also found bones of several Pleistocene animals, including a giant ground sloth, a saber-toothed cat, a horse, and a camelid. Cockrell found an 11,000 year old human skeleton in a fetal position, apparently placed in a crevice with broken stalactites holding it in place. This may be oldest known intentional burial in North America.

In 1996-1997 a group of diver explorers conducted an underwater survey of the site resulting in the mapping of two warm water vents ~97 degrees F and two cool water vents ~76 degrees F. The group also video taped the site including the source of the deepest warm water vent at the end of a 150 ft. lone cave.

Warm Mineral Springs was purchased on December 20, 2010, by Sarasota County and the city of North Port for $5.5 million.

References

• Cockrell, Wilburn A. (1987). "The Warm Mineral Springs Archaeological Research Project: Current Research and Technological Applications". In CT Mitchell. Diving for science 1986: proceedings of the American Academy of Underwater Sciences 6th Annual Scientific Diving Symposium, October 31-November 3, 1986, Tallahasse, Florida, USA.. American Academy of Underwater Sciences. pp. 63–68. http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/9073/AAUS1986_9.pdf?sequence=1. Retrieved 28 November 2011. 
• Milanich, Jerald T. (1994). Archaeology of Precolumbian Florida. Gainesville, Florida: University Press of Florida. ISBN 0-8130-1273-2. 
• Rupert, Frank R. (1994). "The geology of Warm Mineral springs, Sarasota County, Florida". Tallahassee, Florida: Florida Geological Survey. http://library.fgcu.edu/chnep/116a.pdf. Retrieved 24 November 2011. 

External links

• Sarasota County listings at National Register of Historic Places
• Official Warm Mineral Springs website
• Warm Mineral Springs at Florida Cave, Cavern, and Sinkhole Diving
• Warm Mineral Springs Archaeological Society at Florida Anthropological Society
• http://www.simplysiestakey.com/WarmMinSprings.html
• Recent Exploration of Warm Mineral Springs website