The oldest rocks exposed at the surface in Florida are limestones and dolostones that were deposited in a shallow, warm sea during the Middle Eocene age. These rocks consist of the remains of marine organisms (foraminifera, mollusks, echinoids) that died and settled to the bottom of the sea. These limestones comprise part of the Floridan aquifer system, one of the most productive aquifers in the world and the source for most of Florida’s spring water.
Main Image: Remains of marine organisms (foraminifera, mollusks, echinoids) that died and settled to the bottom of the sea 40 million years ago. © FDEP – Harley Means