The bedrock in the center (Bluegrass Region) of the State is composed of limestones and shales from the Ordovician Period (510 to 440 million years ago), and are colored pink on the geologic map above. Much of the Ordovician strata lies buried beneath the surface. The oldest rocks at the surface in Kentucky are limestones from the Late Ordovician Period (approximately 450 million years ago), which are exposed along the Palisades of the Kentucky River (for example, near Camp Nelson, in Jessamine County, pictured above).
Ordovician limestones are quarried from Covington to Danville for use in construction. Some of the limestones also produce natural spring water that is bottled and sold for drinking water. The city of Lexington was founded at McConnell Springs (pictured above), which flows from Ordovician limestones. Many of Kentucky's early settlements were founded near springs.
Other related topics of interest:
Ordovician fossils are abundant in many areas.
Geologic history and environments of the Ordovician in Kentucky (not ready),
Ordovician stratigraphy (not ready)