| Geology of the County | ||
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In Garrard 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 exposed on the surface in Boyle County were deposited in shallow seas 450 million years ago during the Late Ordovician Period. Above the Ordovician rocks are rocks of the Devonian Period, which include the New Albany Shale, also called the black shale. The 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 away 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 Dolomites Interbedded clay shales, siltstones, and sandstones Fractured shales Clay shales Interbedded limestones and shales For more information, see the definitions of geologic terms and rock descriptions, a geologic map of Garrard 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"
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