# Pocono Formation Canonical page: https://lithomap.app/resources/geologic-formations/united-states/pocono-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: Central Appalachian Plateau and Valley and Ridge Age: Early Mississippian Age detail: Mostly Early Mississippian; lower beds locally approach the Devonian boundary Depositional setting: Rivers, deltas, coastal plains, and shallow marine margins Rock types: Sandstone, Siltstone, Shale, Conglomerate States in recognized usage: Maryland, Pennsylvania, Virginia, West Virginia ## Summary The Pocono Formation is a resistant Appalachian sandstone succession that records rivers, deltas, and shallow coastal settings near the beginning of Mississippian time. ## Distribution Pocono rocks form prominent ridges and escarpments across parts of Pennsylvania, Maryland, Virginia, and West Virginia. Regional subdivisions may be mapped as formations within a Pocono Group where they can be traced. Massive sandstone is conspicuous, but thinner shale, siltstone, and local conglomerate are important parts of the succession. Terminology changes substantially from one state and outcrop belt to another. ## Geological history Quartz sand and mud accumulated in channels, deltas, coastal plains, and shallow water as sediment entered the Appalachian basin from the east. Cross-bedding, channel forms, and upward changes in grain size record shifting environments. Appalachian compression later folded and fractured the beds. Resistant sandstone now supports ridges while weaker shale erodes into slopes and gaps. ## Fossil record Plant fragments, spores, trace fossils, and locally marine invertebrates occur, especially in finer lower beds. Many thick sandstone intervals yield few or no body fossils. The mixed terrestrial and marine record varies by member. A fossil-poor ridge-top quartz sandstone is compatible with the formation but not diagnostic by itself. ## Minerals and geological resources Quartz is dominant, with feldspar, mica, clay minerals, and local kaolinite or carbonate cement. Iron oxides stain weathered surfaces, and quartz pebbles occur in conglomeratic beds. Sandstone has supplied local building stone and aggregate, while fractures can transmit groundwater. Resource or aquifer behavior varies with cementation and structure. ## Field context - Massive ledges can be undercut along shale beds and may release large blocks. - Confirm whether the local map uses Pocono as a formation or group. - Ridge exposures commonly cross protected or private land; mapped rock does not grant access. ## Connected field guides - Sandstone (rock; Named rock type and mineral context) — https://lithomap.app/resources/rock-identification/sandstone - Conglomerate (rock; Named rock type) — https://lithomap.app/resources/rock-identification/conglomerate - Shale (rock; Named rock type) — https://lithomap.app/resources/rock-identification/shale - Siltstone (rock; Named rock type) — https://lithomap.app/resources/rock-identification/siltstone - Feldspar (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/feldspar - Kaolinite (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/kaolinite 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 - Central Appalachian bedrock geology — U.S. Geological Survey: https://pubs.usgs.gov/pp/0288/report.pdf - Pocono stratigraphic treatment — U.S. Geological Survey: https://ngmdb.usgs.gov/docs/pamphlets/98325_c-D.pdf ## Formation photograph - Image: https://lithomap.app/_delivery/formations/pocono-formation.webp - Description: Blocky Pocono Formation rocks split by weathering at Ricketts Glen State Park, Pennsylvania - Creator: Ruhrfisch - License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ - Source record: https://commons.wikimedia.org/wiki/File:Ricketts_Glen_State_Park_Pocono_Formation.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.