CAVES AND KARST OF THE ATLANTIC COASTAL RIDGE – MIAMI-DADE COUNTY, FLORIDA

South Florida, unlike elsewhere in the continental United States, has experienced a near continuous deposition of limestone during the past 65 million years. The most recent of these limestones are associated with periods of higher sea-level during the Pleistocene and late Pliocene. The youngest of these limestones, the Miami Limestone, developed a relatively high, but low-relief topographic feature in southeast Florida called the Atlantic Coastal Ridge approximately 125,000 years ago. Collectively these Plio-Pleistocene limestones compose the critically important Biscayne aquifer.

While groundwater scientists consider the Biscayne a karst aquifer, little information exists concerning caves in south Florida. In the late 1980s and early 1990s, Alan Cressler identified and produced rough sketches of 13 Biscayne caves. Recently, we began an effort to survey these caves in cooperation with, and with permits from, the Miami-Dade County Parks and Recreation Department and Everglades National Park. To date, we have surveyed nine caves.

The longest surveyed cave, Fat Sleeper Cave, presently measures nearly 313 feet – an incredible length considering that the average passages in the cave are armoured with so called “razor rock” and measure less than one foot tall. Fat Sleeper Cave, like many of the surveyed caves in south Florida, is located along a transverse glade that nearly bisects the Atlantic Coastal Ridge. These glade-related caves are vertically restricted to a specific zone in the Miami Limestone that is dominated by cm-scale-diameter, touching-vug porosity formed when the rock was deposited and enhanced into “razor rock” by the recent formation of the cave.