Geology of the County

In Nicholas County, water is obtained from consolidated sedimentary rocks of Ordovician age and unconsolidated sediments of Quaternary age. The oldest formation found on the surface in Nicholas County, the Lexington Limestone, was deposited in shallow seas 490 million years ago during the Ordovician. 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
Unconsolidated deposits
Alluvium (Qa)

Lexington Limestone (Ol)

Interbedded clay shales, siltstones, and sandstones
Garrard Siltstone (Okc)

Interbedded limestones and shales
Grant Lake Limestone/Fairview Formation/Calloway Creek Limestone (Oaf)
Clays Ferry Formation (Okc)

Interbedded shales and limestones

For more information, see the definitions of geologic terms and rock descriptions, a geologic map of Nicholas County, a summary of the geology of Kentucky, and a discussion of fossils and prehistoric life in Kentucky.

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