Geology of the County

In Fleming County, water is obtained from consolidated sedimentary rocks ranging in age from Ordovician to Mississippian and from unconsolidated sediments of Quaternary age. The oldest rocks found on the surface in Fleming County were deposited in shallow seas 490 million years ago during the Ordovician. Above the Ordovician rocks, the Devonian New Albany Shale, 400 million years old, was formed when the deep sea floor became covered with an organic black muck. The muck is now hard black shale (an oil shale) and is one of the most distinctive of all geologic formations in Kentucky. The Mississippian sandstones and siltstones are the result of a great influx of mud, silts, and sands brought in by rivers and streams from uplands many miles to the northeast and deposited as a great delta. 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
Borden Formation (MDbb)

Fractured shales
New Albany Shale (MDnb)

Clay shales
Crab Orchard Formation and Brassfield Dolomite (Scb)

Interbedded limestones and shales
Drakes Formation (Od), (Odb) / Bull Fork Formation (Ob)
Grant Lake Limestone/Fairview Formation/Calloway Creek Limestone (Oaf)
Garrard Siltstone (Okc)
Kope Formation (Okc)
Clays Ferry Formation (Okc)

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

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