Tuscarora Formation

The Silurian Tuscarora Formation (St) is a mapped bedrock unit in Pennsylvania, Maryland, Virginia and West Virginia. It is also sometimes referred to as the Tuscarora Sandstone or the Tuscarora Quartzite.

Description

The Tuscarora is a thin- to thick-bedded fine-grained to coarse-grained orthoquartzite. It is a white to medium-gray or gray-green subgraywacke, sandstone, siltstone and shale, cross-stratified and conglomeratic conglomerate in parts, containing a few shale interbeds.Berg, T.M., Edmunds, W.E., Geyer, A.R. and others, compilers, (1980). Geologic Map of Pennsylvania: Pennsylvania Geologic Survey, Map 1, scale 1:250,000.] cite web |url=http://www.dcnr.state.pa.us/topogeo/openfile/midsusque.pdf |title= Preliminary Bedrock Geologic Map of the Middle Portion of the Susquehanna River Valley, Cumberland, Dauphin, And Perry Counties, Pennsylvania |year=2007|accessdate=2008-01-26 |author= Jackson, Margaret S.; Hanley, Peter M.; and Sak, Peter B. |publisher=Pennsylvania Geological Survey|format=pdf |work=Open File Report OFBM-07-05.0] cite web |url=http://www.mgs.md.gov/esic/geo/lgdalleg.html |title=Geologic Maps of Maryland: |accessdate=2008-01-26 |format= |work=] There is one named member of this formation: Castanea (Stc), occurring at the top, leaving the Lower and Middle Tuscarora Formation (Stlm) at the bottom.cite paper|url=http://www.dcnr.state.pa.us/topogeo/openfile/mcalevysfort.pdf|format=pdf|author= Doden, Arnold G. and Gold, David P.|year=2008|title=Bedrock Geologic Map of The Mc Alevys Fort Quadrangle, Huntingdon, Centre, and Mifflin Counties, Pennsylvania|publisher=Pennsylvania Geological Survey]

The Tuscarora is a lateral equivalent of the Minsi and Weiders members of the Shawangunk Formation in eastern Pennsylvania, New Jersey, and New York, and of the Massanutten Formation sandstone in Virginia. The Tuscarora and its lateral equivalents are the primary ridge-formers of the Ridge-and-Valley Appalachians in the eastern United Statescite web |url=http://daac.gsfc.nasa.gov/geomorphology/GEO_2/GEO_PLATE_T-12.shtml |title=Geomorphology : Chapter 2 Plate T-12 : Folded Appalachians | date = 2007-01-19 |accessdate=2008-03-16 |publisher= NASA, Goddard Earth Sciences (GES), Data and Information Services Center (DISC) |first=Steve | last = Kempler|work=|quote=The major ridge makers are the Tuscarora (T), Pocono (Po), and Pottsville (Pt) Formations.] It is typically 935 feet thick in Pennsylvania, and in Maryland varies from 60 feet to 400 feet thick from east to west.

=Depositional Environment=

The Tuscarora has always been intrepreted as molasse resulting from the Taconic orogeny. It is thought to represent a vast sand shoal along the margin of the Iapetus Ocean.

Fossils

Very few fossils exist in the Tuscarora, and most of them are trace fossils. Ripple marks are seldom found.

Age

Relative age dating of the Tuscarora places it in the Lower Silurian period, being deposited between 440 to 417 (±10) million years ago. It rests conformably atop the Juniata Formation and conformably below the Clinton Group in Pennsylvania. [Berg, T.M., et al., (1983). Stratagraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.]

Economic uses

The Tuscarora may have been used as a ganister for making furnace liners in 19th century iron smelting blast furnaces of central Pennsylvania.

References

ee also

*Big Mountain (Pennsylvania)
*Bald Eagle Mountain
*Brush Mountain
*Germany Valley
*Geology of Pennsylvania
*Massanutten Mountain
*Mount Nittany
*North Fork Mountain
*Tussey Mountain
*River Knobs (West Virginia)

*Seneca Rocks