Lexington Limestone

The Lexington Limestone is a prominent geologic formation that constitutes a large part of the late Ordovician bedrock of the inner Bluegrass region in Kentucky. Named after the city of Lexington, the geologic formation has heavily influenced both the surface topography and economy of the region.

It overlies the approximately Middle to Late Ordovician High Bridge Group, which is only exposed in some valleys of the Kentucky River, and underlies the Clays Ferry Formation. Since the time of its deposition spans several million years which were accompanied by constant sea level and topographical changes, the lithology of the Lexington Limestone varies significantly with geographic location and stratigraphic position within the rock column. Due to this, it is divided into 11 sub-units which sometimes complexly grade into and intertongue with each other. The formation is largely composed of limestone, however shale is also usually present in varying amounts, and in some sub-units is dominant.