|Geology of the County
In Spencer County, water is obtained from consolidated sedimentary rocks of Ordovician age and unconsolidated sediments of Quaternary age. The oldest rocks found on the surface in Spencer County, the Clays Ferry Formation, were deposited in shallow seas 490 million years ago during the Ordovician Period. In the Late Ordovician the seas became relatively shallow, as indicated by the amounts of mud (shale) in the sediments. When the waters were clear and warm, a profusion of animal life developed, particularly brachiopods and bryozoa. Over the last million years unconsolidated Quaternary sediments have been deposited along the larger streams.
Geologic Formations in the County
Interbedded limestones and shales
Interbedded shales and limestones
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.