|Geology of the County|
In Johnson County, water is obtained from consolidated sedimentary rocks of the Pennsylvanian Breathitt Formation, and from unconsolidated Quaternary sediments. The sediments of the Pennsylvanian were deposited 320 million years ago. The warm climate of the Pennsylvanian grew extensive forests and great coastal swamps 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 non-vegetative sediments such as sand, clay and silt were compressed into sandstone and shale. Over the last one million years unconsolidated Quaternary sediments have been deposited along the larger streams and rivers.
Geologic Formations in the County
Coals, sandstones, and shales
For more information, see the definitions of geologic terms and rock descriptions, a geologic map of the county, a summary of the geology of Kentucky, and a discussion of fossils and prehistoric life in Kentucky.