The Little Salt Spring Fossil Site in Southwestern Florida

About 50 years ago, scuba divers discovered Little Salt Springs was not the shallow brackish pond everybody thought it was.  They were surprised to find it was 200 feet deep.  From an aerial view the lake is perfectly round, but underneath the surface it is hourglass-shaped with ledges that were above the water table until ~7,000 years ago.  Below 20 feet the water here has no dissolved oxygen, making it inhospitable to fish and microorganisms that would normally decompose organic material.  The conditions are exceptionally favorable for the preservation of animal bones and human artifacts.  The real estate company that owned the sinkhole and the land around it donated this scientifically significant site to the University of Miami.  That institution employed scientists who administered and studied the sinkhole for over 30 years.   Then, a few years ago, some budget-cutting troglodyte sold the site to Sarasota County, probably so the university can spend more money hiring football coaches, like Mark Richt.

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Little Salt Spring is located on the outskirts of North Port, Florida, not far from Sarasota.

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Illustration of Little Salt Spring.  There is no dissolved oxygen below about 20 feet, and therefore no bacteria, resulting in excellent preservation of ancient fossil remains and organic artifacts.

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Deer antler with 28 notches carved into it marking the 28 days of the lunar month.  It’s a kind of archaic Indian calendar. It was found in the sinkhole along with many other artifacts.

The most famous specimen discovered in Little Salt Spring is a giant tortoise (Hesperotestudo crassicutata) shell with a wooden stake stuck through it.  Archaeologists believe it fell on to a ledge that was above the water table at the time.  A Paleo-Indian killed the tortoise with a wooden stake, turned it on its back, and cooked the unlucky chelonian in its shell.  Despite the likelihood that overhunting by humans caused the extinction of this species, this is the only direct evidence that people exploited them.  Some researchers initially rejected this interpretation because the carbon date for the wooden stake didn’t match the radiocarbon date of the tortoise shell.  But improved radiocarbon dating techniques since then have confirmed the wooden stake and the tortoise shell are the same age.

A series of wooden stakes, now submerged, were planted above the ledge where the cooked tortoise shell was found.  Archaeologists think the stakes may have supported some kind of camouflage that hid the steep ledge.  Prey animals blundered or were chased off the precipice and became trapped on the ledge.  The stakes may have also supported rope ladders, so the Indians could climb down and kill the animal trapped on the ledge.

A National Geographic News article from 2009 mentions the butchered remains of a Jefferson’s ground sloth were found on a submerged ledge at this site.  This would be just the 2nd known case of human exploitation of a ground sloth in North America.  However, I can find nothing in the scientific literature about this specimen.  Although professors from the University of Miami studied this site for decades, they published just an handful of papers about it.  The volume of research they produced surprises and disappoints me.

Most of the human artifacts found at this site are early archaic.  Some of the most interesting include 4 non-returning boomerangs made of oak wood that date to ~9,000 years ago, a carved atlatl handle, a green stone pendant, and a notched deer antler used as a lunar calendar.  There are hundreds of archaic Indian graves where human remains have rested for over 5000 years.  The water table rose shortly after people were buried by the lake’s edge, resulting in excellent preservation–some skulls still have brain matter inside.

Scientists have identified the bones of mastodon, Jefferson’s ground sloth, saber-tooth, rabbit, wood stork, giant tortoise, gopher tortoise, Florida cooter, red-bellied turtle, an extinct species of box turtle, diamondback rattlesnake, and largemouth bass from Little Salt Spring.  Less than 5% of the site has been surveyed for subfossil remains and artifacts.  I’m sure the list would grow, if there was a concerted effort made by scuba-diving paleontologists.

During the late Pleistocene, Little Salt Spring was much farther inland from sea level than it is today.  Dry land extended for many miles into the Gulf of Mexico.  The composition of species suggests that when Indians first discovered this sinkhole it was a wetland oasis surrounded by arid sand hill savannahs dotted with a sparse tree canopy.

References:

Holman, J.; and Carl Clausen

“Fossil Vertebrates Associated with Paleo-Indian Artifacts at Little Salt Spring”

Journal of Vertebrate Paleontology 4 (1) September 1984

Wisner, G.

“Diving into Paleo-Florida”

Mammoth Trumpet 23 (1) 2008

 

 

 

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One Response to “The Little Salt Spring Fossil Site in Southwestern Florida”

  1. Marnie Dunsmore Says:

    Great article. Very interesting.

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