|Geology of the County
In Crittenden County, water is obtained from consolidated sedimentary
rocks of Mississippian through Pennsylvanian age and from unconsolidated
sediments of Cretaceous and Quaternary age. Geologists call the oldest
rocks found at the surface in Crittenden County the Fort Payne Formation.
The most common rock types in Crittenden County are the Mississippian
limestones, which were deposited 350 million years ago in the bottom
of a warm, shallow sea. At the end of the Mississippian Period, 320
million years ago, the seas receded and sediments of the Pennsylvanian
Period were deposited. The warm climate of the Pennsylvanian allowed
extensive forests and great coastal swamps to form at the edges of water
bodies. Marine waters advanced and receded many times, which produced
many layers of sandstone, shale, and coal. Vegetation of all sorts fell
into the water and was buried under blankets of sediments, which over
long geologic time were compressed into coal. The nonvegetative sediments
such as sand, clay, and silt were compressed into sandstone and shale.
During the latter part of the Cretaceous, 130 million years ago, the
Gulf of Mexico inundated much of the southern United States and covered
all the Jackson Purchase and some of the Mississippian Plateaus with
sands, clays, and gravels. These
Geologic Formations in the County
Interbedded limestones, sandstones, and shales
For more information, see the definitions of geologic terms and rock descriptions, a geologic map of Crittenden County, a summary of the geology of Kentucky, and a discussion of fossils and prehistoric life in Kentucky.