| Geology of the County | ||
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In Bullitt County water, is obtained from consolidated sedimentary rocks of Ordovician, Silurian, Devonian, and Mississippian ages, and unconsolidated sediments of Quaternary age. The oldest rocks found on the surface in Bullitt County are the Calloway Creek limestones, 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. Lying on top of the Ordovician rocks are the Silurian rocks, which were also deposited in warm seas, 430 million years ago. In Kentucky the Silurian seas were commonly warm and clear, although the presence of some shale beds suggest that muddy conditions prevailed at times. Locally, numerous corals and brachiopods can be found in the Silurian limestones and dolomites. The New Albany Shale, also called the black shale, was formed 400 million years ago during the Devonian, when the deep sea floor became covered with an organic black muck. The muck is now hard black shale (an oil shale) which 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 Mississippian limestone found in Bullitt County was deposited 350 million years age 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 Limestones Interbedded clay shales, siltstones, and sandstones Fractured shales 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"
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