Geology of the County

In Bourbon 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 Bourbon County are the Lexington Limestone, deposited in shallow seas 490 million years ago during the Middle 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, the unconsolidated Quaternary sediments have been deposited along the larger streams and rivers.

Geologic Formations in the County

Unconsolidated deposits
Alluvium (Qa)

UPPER PART OF Lexington Limestone (Ol) (Strodes Creek, Millersburg, Tanglewood Limestone, Devils Hollow, Stamping Ground, Sulphur Well, Brannon Members)
LOWER PART OF Lexington Limestone (Ol) (Grier, Logana, Curdsville Members)

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

Interbedded limestones and shales
ASHLOCK FORMATION, Calloway Creek Limestone (Oaf)
Clays Ferry Formation (Okc) and KOPE FORMATION (Ok)

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.

Previous--Next--Back to "Groundwater Resources in Kentucky"