The Ancient Marine Origins of the Berm Surfaces at Ritch Grissom Memorial Wetlands - Reprinted from the Viera Wetlands Events & Happenings newsletter

The Ancient Marine Origins of the Berm Surfaces at Ritch Grissom Memorial Wetlands

Throughout most of its history, Florida has been under water. Many of Florida's modern topographic features and surficial sediments were created or deposited during periods when sea levels were high. Waves and currents in these ancient seas eroded the exposed formations of previous epochs, reshaping earlier landforms and redistributing eroded sediments over a wide area. Evidence indicates Florida's earliest geologic formations began during the Eocene Epoch, between 54 and 38 million years ago. In contrast, geologically speaking, the surficial deposits that form east-central Florida, including Brevard County, are very young. Most formed around 10,000 years ago, during the Holocene; before then, this landmass on which we make our home was covered by the ocean. Consequently, much of our surface geology is composed of shallow sediments derived from marine deposits. Over time, as sea levels rose and fell, generations of coral, shellfish, and fish skeletons piled up on the ocean floor where they mixed with quartz sand and clay, and the resulting layers of sediment became cemented together with calcite, aragonite, and other minerals. Since most marine organisms use calcium carbonate to build their shells or part of their mineralized structure, sedimentary rocks of biochemical origin are classified as limestones. Limestone is the most common type of rock in the Florida peninsula, where it is mined for road building and other construction applications. Different types of biochemical limestone are identified depending on grain size and degree of cementation and crystallization, including coquina, fossiliferous limestone, calcarenite, micrite, and chalk. Coquina, readily identifiable by its characteristic texture of whole and fragmented shells, has been used as a building stone in Florida for over 400 years; a notable example can be seen today in the walls of the Castillo de San Marcos in Saint Augustine.  The ancient marine origins of Florida limestone also are evident on the surface of the berms at Ritch Grissom Memorial Wetlands. Over time, the crushed limestone rock used to grade and stabilize the berm surfaces gradually erodes and decomposes, unconsolidating its various components. Rain, wind, and human activity, particularly vehicular disturbance under wet conditions, further degrade the limestone, sloughing off its finer particles and leaving behind its larger constituents. Inevitably, erosion will take its toll, eventually exposing the underlying soft sandy deposits, requiring the berms to be resurfaced with a fresh layer of limestone, and a new reminder of the ancient seas that once covered this place we call home. * The information contained in this article was derived primarily from The Geological History of Florida by Jason B. Barr (2009). A map showing the berm roads and cells is available at the following link: Viera Wetlands Map