| Lexington Limestone | |
|---|---|
| Stratigraphic range: Late Ordovician,[1][2] | |
| Type | Formation |
| Sub-units | 11 members[3] |
| Underlies | Clays Ferry Formation[3] |
| Overlies | High Bridge Group[3] |
| Thickness | Around 320 feet in core regions, thins to around 200 feet northward and southward[3] |
| Lithology | |
| Primary | Limestone[2][3] |
| Other | Shale[2][3] |
| Location | |
| Region |  Kentucky |
| Country |  United States |
| Type section | |
| Named for | Lexington, Kentucky |
| Named by | M. R. Campbell[4] |
| Year defined | 1898[4] |
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.[5]
It overlies the approximately Middle to Late Ordovician High Bridge Group, which is only exposed in some valleys of the Kentucky River,[6] 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.[3]
- ^ Tucker, R. D. (1992). "U-Pb dating of Plinian-eruption ashfalls by the isotope dilution method: A reliable and precise tool for time-scale calibration and biostratigraphic correlation". Geological Society of America. 24 (7). OSTI 5589081.
- ^ a b c Schrantz, Rick (2001). "The Lexington Limestone". University of Kentucky. Retrieved 23 December 2016.
- ^ a b c d e f g Cressman, E. R. (1973). "Lithostratigraphy and Depositional Environments of the Lexington Limestone (Ordovician) of Central Kentucky" (PDF). U.S. Geological Survey Publications. Retrieved 23 December 2016.
- ^ a b "The Lexington Limestone(Middle Ordovician) of Central Kentucky" (PDF).
- ^ "Bluegrass Region". University of Kentucky. 2016. Retrieved 2 July 2017.
- ^ "The Ordovician of Kentucky". U.S. Geological Survey. 2001. Retrieved 2 July 2017.