# Tuscarora Formation Canonical page: https://lithomap.app/resources/geologic-formations/united-states/tuscarora-formation Last reviewed: September 17, 2026 Page purpose: Comprehensive United States geologic formation reference for human readers, search systems, and language models. Major region: Appalachians Regional setting: Appalachian Valley and Ridge Age: Latest Ordovician to Early Silurian Age detail: Late Ordovician into Early Silurian, varying with regional definition Depositional setting: High-energy shorelines and shallow marine sand during basin uplift and erosion Rock types: Quartz sandstone, Quartzite, Conglomeratic sandstone, Shale States in recognized usage: Maryland, Pennsylvania, Virginia, West Virginia ## Summary The Tuscarora Formation is a hard, quartz-rich ridge former of the central Appalachians, deposited around the Ordovician–Silurian transition as sand spread across a changing shallow sea. ## Distribution Tuscarora sandstone and quartzite form long, narrow ridges in Pennsylvania, Maryland, Virginia, and West Virginia. The unit follows tightly folded Appalachian structures and may be repeated by faults. Naming varies between Formation, Sandstone, and Quartzite, and not every white ridge-forming sandstone is Tuscarora. Contacts and regional equivalents should be taken from the appropriate state map. ## Geological history Quartz-rich sand and local pebbles were reworked in energetic coastal and shallow-marine settings as erosion supplied sediment to the Appalachian basin. Cross-bedding and burrows record moving sand and periods of seafloor colonization. Deep burial and Appalachian deformation compacted and cemented the sandstone, locally producing very hard quartzite. Folding then tilted beds steeply and erosion isolated them as resistant ridges. ## Fossil record Body fossils are generally sparse, but trace fossils such as vertical burrows can be conspicuous. Rare shelly or shaly beds preserve better biological evidence and help constrain age. A track-like marking should not be identified from shape alone; cross-sections and bedding context are needed to separate burrows from sedimentary structures or fractures. ## Minerals and geological resources Quartz is overwhelmingly dominant in many beds. Minor feldspar, mica, clay minerals, and iron oxides occur, and silica cement produces quartzite where recrystallization is strongest. Hard stone has been used locally for aggregate and construction. Fractures control most groundwater movement because the intact quartz-rich rock has little pore space. ## Field context - Talus below quartzite cliffs is unstable and may hide holes between blocks. - Steeply dipping beds can shed slabs along joints and bedding planes. - Formation rank and age limits differ across state boundaries. ## Connected field guides - Quartz (mineral; Named rock type and mineral context) — https://lithomap.app/resources/mineral-identification/quartz - Quartzite (rock; Named rock type and mineral context) — https://lithomap.app/resources/rock-identification/quartzite - Sandstone (rock; Named rock type) — https://lithomap.app/resources/rock-identification/sandstone - Shale (rock; Named rock type) — https://lithomap.app/resources/rock-identification/shale - Feldspar (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/feldspar Mapped location and formation context support an identification but cannot establish one. Compare several physical properties and use laboratory analysis when the material remains ambiguous. ## Connected state geology guides - Pennsylvania geology — https://lithomap.app/resources/geology/united-states/pennsylvania ## Authoritative sources - Geolex Tuscarora unit record — U.S. Geological Survey: https://ngmdb.usgs.gov/Geolex/Units/Tuscarora_4187.html - Geolex Tuscarora references — U.S. Geological Survey: https://ngmdb.usgs.gov/Geolex/UnitRefs/TuscaroraRefs_4187.html ## Formation photograph - Image: https://lithomap.app/_delivery/formations/tuscarora-formation.webp - Description: Resistant Tuscarora Formation sandstone outcrop in Pennsylvania - Creator: James Stuby - License: Public domain — https://creativecommons.org/publicdomain/mark/1.0/ - Source record: https://commons.wikimedia.org/wiki/File:Tuscarora_Formation_outcrop_1.jpg Formation-level information does not prove that a fossil or mineral occurs at a specific coordinate. It also does not establish ownership, access, collecting permission, present conditions, or specimen identity.