|Geology of the County|
In Hardin County, water is obtained from consolidated sedimentary rocks of Devonian and Mississippian age and from unconsolidated sediments of Quaternary age. Geologists call the oldest rocks found at the surface in Hardin County the New Albany Shale. This formation is from the Devonian Period, and was deposited in warm seas 400 million years ago. The New Albany Shale 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 away and deposited as a great delta. The most common rock types in Hardin County are Mississippian limestones, which were deposited 350 million years ago in the bottom of a warm, shallow sea. 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, sandstones, and shales
For more information, see the definitions of geologic terms and rock descriptions, a geologic map of Hardin County, a summary of the geology of Kentucky, and a discussion of fossils and prehistoric life in Kentucky.