|Geology of the County|
In Robertson 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 Robertson County, rocks of the Lexington Limestone, 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 and rivers.
Geologic Formations in the County
Interbedded clay shales, siltstones, and sandstones
Interbedded limestones 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.