| Geology of the County | ||
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In Trigg County, water is obtained from consolidated sedimentary rocks of Mississippian age and from unconsolidated sediments of Cretaceous through Quaternary ages. Geologists call the oldest rocks found at the surface in Trigg County the Fort Payne Formation. The most common rock types in Trigg County are Mississippian limestones, which were deposited 350 million years ago in the bottom of a warm, shallow sea. During the latter part of the Cretaceous Period, 130 million years ago, the Gulf of Mexico inundated much of the southern United States and covered all of the Jackson Purchase and some of the Mississippian Plateaus with sands, clays, and gravels. These geological deposits are a marked contrast to the underlying, older hard rocks, because most of the Cretaceous and younger sediments remain unconsolidated and soft. Over the last million years, Quaternary sediments have been deposited along the larger streams and rivers. Geologic Formations in the County Unconsolidated deposits Limestones Sandstones Interbedded limestones, sandstones, and 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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