Geology of the County

In Crittenden County, water is obtained from consolidated sedimentary rocks of Mississippian through Pennsylvanian age and from unconsolidated sediments of Cretaceous and Quaternary age. Geologists call the oldest rocks found at the surface in Crittenden County the Fort Payne Formation. The most common rock types in Crittenden County are the Mississippian limestones, which were deposited 350 million years ago in the bottom of a warm, shallow sea. At the end of the Mississippian Period, 320 million years ago, the seas receded and sediments of the Pennsylvanian Period were deposited. The warm climate of the Pennsylvanian allowed extensive forests and great coastal swamps to form at the edges of water bodies. Marine waters advanced and receded many times, which produced many layers of sandstone, shale, and coal. Vegetation of all sorts fell into the water and was buried under blankets of sediments, which over long geologic time were compressed into coal. The nonvegetative sediments such as sand, clay, and silt were compressed into sandstone and shale. During the latter part of the Cretaceous, 130 million years ago, the Gulf of Mexico inundated much of the southern United States and covered all 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
Alluvium and glacial outwash sediments (Qa)
Tuscaloosa Formation (Kt)
Chert rubble

Lamprophyre dikes and sills (Pl)

Ste. Genevieve Limestone (Levias Limestone, Rosiclare Sandstone, Fredonia Limestone Members) (Mgl)
St. Louis Limestone (Mgl)
Fort Payne Formation (Mbf)

Tradewater (Pt) and Caseyville (Pca) Formations

Interbedded limestones, sandstones, and shales
Kinkaid Limestone, Degonia Sandstone, Clore Limestone (Mcu)
Palestine Sandstone (Mcu)
Menard Limestone, Waltersburg Sandstone, Vienna Limestone (Mcu)
Tar Springs Sandstone (Mcu)
Glen Dean Limestone (Mcl)
Hardinsburg Sandstone (Mcl)
Golconda Formation (Haney Limestone, Big Clifty Sandstone, Beech Creek Limestone Members) (Mcl)
Cypress Sandstone (Mcl)
Paint Creek Shale (Mcl)
Bethel Sandstone (Mcl)
Renault Limestone (Mcl)

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

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