Florida Caverns State Park / Marianna, Florida

by Robert O. Vernon

As visitors explore the well-lighted trails and passageways, they notice the icicle-like formations that hang from the ceilings and the heavier ones that project from the floor. They study the columns that seem to help support the rock above and the small passages that extend in many directions. They notice sea shells imbedded in walls and ceilings.

How do we know that these limestones were formed in the sea? The next time you go through the caves at Florida Caverns look closely at the walls and you will be able to find the shells of Scollops and other clams. These animals lived only in shallow seas. The most common shell that you will notice will be many small coiled flat shells about the size of barley seed and flat thin disks about the size of dimes and quarters. The animals that formed these shells are known as Foraminifera and have the fancy names of Operculinoides and Lepidocyclina. They are one celled animals (our most primitive) and are related to some of the parasites that cause disease. These particular animals are extinct and are known only from these rocks. From their association with other shells they are known to have lived in shallow salt-water seas, and by means of them the geologist is able to recognize this particular limestone, even when it has been taken from a well drilled many feet below the ground surface, for these small shells are recognizable even when the limestone has been broken into fine fragments.

The limestone in which the caves of Florida Caverns were carved is known from geologic studies made throughout the state to have been raised from the sea by land movements after being formed and to have been extensively eroded, following which it was again submerged under the sea and other limestones deposited over the eroded surface. These limestones were subsequently raised out of the sea to be eroded. Over this second eroded surface a delta deposit of sand, clay and gravel was formed by streams that emptied into the Gulf of Mexico.

The limestone that you will see in the caves is known as the Ocala limestone, named from deposits near Ocala, Florida. In the region about the Florida Caverns, limestones named the Suwannee limestone and the Marianna limestone overlie the Ocala limestone. These limestones were named for deposits recognized along the Suwannee river and at Marianna, Florida. The sand, clay and gravel overlying all of these limestones are not named but are believed to be the same age as deposits of the geologic period popularly known as the “ice age.”

The “duck” results from irregular resistance of the limestone to solution by ground water. These nodular masses were more resistant and the less-resistant, usually softer limestone has been removed from about them, leaving the form resembling a duck. Several stalagmites are in the background. These are younger than the “duck.”

Since emerging from the sea for the last time, this part of Florida about the state park area has been undergoing changes constantly. The rocks have been continuously attacked by elements of the weather, and disintegrated where exposed. Running streams carry away much of these products of weathering, but the work of water under the ground is the major factor in the creation of these caves and the deposits in them. This underground water, running through the pores in the limestone, has been and is now wearing away portions of the land. These water channels are isolated along fractures, bedding planes and other structural weaknesses, or along poorly consolidated rock. The water dissolves the limestone and carries it out into surface streams and on to the sea, and as this material is carried away the rock, through which the water flowed to the surface, is being worn away an equal amount. The amount of this material being carried away is illustrated at Silver Springs, one of our larger springs, where each day about 450 tons of rock is carried away dissolved in water. When it is realized that this is only one of thousands of springs in Florida, you can readily see what a large amount of rock is being dissolved from beneath the ground and just how cavernous the rock must be.

All forms of wildlife are protected in Florida’s State Parks. Hunting, trapping, or shooting are not permitted. These State Parks belong to you. Help protect them.

For further information on specific parks and historic memorials write: Director, Florida Board of Parks and Historic Memorials, Tallahassee, Florida.