Stratigraphic range: Early Silurian
Rocks of the Clinton Group on the east face of Schuylkill Gap
|Sub-units||Rochester Shale, Rose Hill Formation, Keefer Formation|
|Underlies||Bloomsburg Formation in Pennsylvania, Lockport Group in New York|
|Overlies||Tuscarora Formation in Pennsylvania, Clinch Formation in Virginia, Tennessee, and Maryland, Medina Group in New York|
|Primary||sandstone, shale, and limestone|
|Other||Ironstone and conglomerate,|
|Region||Appalachian Basin of eastern North America|
|Extent||Pennsylvania, Maryland, New York, West Virginia|
|Named for||Clinton, New York|
|Named by||Lardner Vanuxem (1842)|
The Clinton Group (also referred to as the Clinton Formation or the Clinton Shale) is a mapped unit of sedimentary rock found throughout eastern North America. The interval was first defined by the geologist Lardner Vanuxem, who derived the name from the village of Clinton in Oneida County, New York where several well exposed outcrops of these strata can be found. The Clinton Group and its lateral equivalents extend throughout much of the Appalachian Foreland Basin, a major structural and depositional province extending from New York to Georgia. The term has been employed in Kentucky, Maryland, Michigan, New York, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia, though in many of these areas the same interval is referred to as the Rose Hill, Rockwood, or Red Mountain Formations. Historically the term "Clinton" has also been assigned to several lower Silurian stratigraphic units in Ohio and Kentucky which are now known to be significantly older than the Clinton Group as it was originally defined. Many parts of this succession are richly fossiliferous, making the Clinton Group an important record of marine life during the early Silurian. Several economically valuable rock-types are found within this interval, though it is perhaps best known as a significant source of iron ore 
Stratigraphically, the Clinton Group overlies the coarse siliciclastics of the Medina Group in New York, The Albion Group in the Subsurface of Ohio, the Clinch Sandstone in Virginia and West Virginia, and the Tuscarora Sandstone in Pennsylvania. It is overlain by the shales and carbonates of the Lockport Group in New York, the McKenzie Formation in Pennsylvania, and the Sneedville Limestone in Tennessee. Owing to the great difference in resistivity between the relatively soft, readily weathering Clinton Group and the massive dolostones of the overlying Lockport, the former tends to erode preferentially out from underneath the latter. This has resulted in the formation of numerous cateracts such as Niagara Falls and the High Falls of Rochester, New York which are but local manifestations of a regional geographic feature called the Niagara Escarpment.
The Clinton Group (or Formation) is a widely traceable, lower Silurian lithostratigraphic unit composed primarily of shale and mudstone, though it encompasses a heterogeneous assemblage of sedimentary rock types, including conglomerate, sandstone, limestone, dolostone, and ironstone. In its designated type area in Clinton, Oneida County, New York the unit is approximately 50 meters (180 feet) thick, and composed primarily of blue-grey mudstone, shale, and sandstone with several discrete ferruginous horizons, known colloquially as "Clinton Ironstones". The lateral equivalent of these beds to the south is the Rose Hill Formation of Pennsylvania, and olive-gray to drab, thin-bedded sandstone.
In Maryland, the Rose Hill Formation contained the Cresaptown Iron Sandstone.
Relative age dating of the Clinton Group places it in the Lower Silurian period. It rests conformably atop the Tuscarora Formation and conformably below the Lower and Upper Silurian Lockport Group and Bloomsburg Formation.
- Brett, C.E.; Baarli, B.G.; Chowns, T.; Cotter, E.; Driese, S.; Goodman, W.; Johnson, M.E. (1998). "Early Silurian Condensed Intervals, Ironstones, and Sequence Stratigraphy in the Appalachian Foreland Basin". In Landing, E.; Johnson, M.E. Silurian Cycles: Linkages of Dynamic Stratigraphy with Atmospheric, Oceanic and Tectonic Changes. James Hall Centennial Volume. New York State Museum Bulletin 491. pp. 89–143.
- "Clinton Group, Group". National Geologic Map Database. Retrieved 2012-10-05.
- Vanuxem, L. (1839). "Third Annual Report of the Geological Survey of the Third District". New York State Geological Survey Annual Report 3. pp. 241–285.
- Gillette, T. (1947). "The Clinton of Western and Central New York". New York State Museum Bulletin 341. Albany, New York: The University of the State of New York. pp. 1–191.
- Brett, C.E.; Goodman, W.M.; LoDuca, S.T. (1990). "Sequences, cycles, and basin dynamics in the Silurian of the Appalachian Foreland Basin". Sedimentary Geology 69: 191–244. doi:10.1016/0037-0738(90)90051-T.
- Rexroad, C.B.; Branson, E.R.; Smith, M.O.; Summerson, C.; Boucot, A.J. (1965). "The Silurian Formations of East-Central Kentucky and Adjacent Ohio". Kentucky Geological Survey, Series X 2: 1–34.
- "Iron Ore Mining and Manufacturing in the Town of Kirkland". Lecture at the Clinton Historical Society meeting on April 16, 1998 at the Society's Headquarters on Fountain Street, Clinton, New York. Retrieved 2012-10-05.
- The Niagara Escarpment
- "Geologic Maps of Maryland:". Retrieved 2008-01-26.
- Ryder, Robert T. et al. "Possible Continuous-Type (Unconventional) Gas Accumulation in Lower Silurian "Clinton" Sands, Medina Group, and the Tuscarora Sandstone in the Appalachian Basin: A Progress Report of 1995 project activities". USGS. Retrieved 2008-01-26.
- Jackson, Margaret S.; Hanley, Peter M.; and Sak, Peter B. (2007). "Preliminary Bedrock Geologic Map of the Middle Portion of the Susquehanna River Valley, Cumberland, Dauphin, And Perry Counties, Pennsylvania" (pdf). Open File Report OFBM-07-05.0. Pennsylvania Geological Survey. Retrieved 2008-01-26.