# Lock Haven Formation Canonical page: https://lithomap.app/resources/geologic-formations/united-states/lock-haven-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: North-central Appalachian Basin Age: Late Devonian Age detail: Late Devonian, between deeper-water Brallier rocks and the Catskill transition Depositional setting: Marine shelf receiving sediment from the rising Acadian highlands Rock types: Shale, Siltstone, Sandstone, Minor conglomerate States in recognized usage: Pennsylvania ## Summary The Lock Haven Formation is a fossil-bearing marine transition of shale, siltstone, and sandstone that records a Late Devonian shoreline advancing westward across Pennsylvania. ## Distribution The formation is mapped principally in north-central Pennsylvania, where folded ridges and valleys expose it between the Brallier and Catskill formations. It replaces part of the older, now-abandoned Chemung terminology in current Pennsylvania usage. Sandstone proportion and fossil content change laterally and upward. Weathering creates ledges above shale slopes, but isolated sandstone cannot be assigned confidently without its stratigraphic neighbors. ## Geological history Mud, silt, and sand entered the Appalachian foreland basin from eastern highlands. Storms and river-fed plumes carried sand across the marine shelf, creating lenticular, cross-bedded sandstone within quieter-water shale. Upward coarsening and increasing terrestrial influence mark the long transition toward Catskill river and delta deposits. Later Appalachian deformation folded and fractured the section into today’s ridges and valleys. ## Fossil record Brachiopods, bivalves, gastropods, cephalopods, crinoid debris, and trace fossils occur in marine beds. Assemblages vary with water depth, oxygen, and distance from sediment sources. Fossil-rich layers can sit close to nearly barren sandstone or shale. The formation’s broad marine character does not predict fossils at every outcrop. ## Minerals and geological resources Quartz, clay minerals, feldspar, mica, and calcite are common, with pyrite and iron-rich concretions locally present. Weathering converts iron-bearing minerals to red, yellow, or brown oxides. Sandstone and shale have chiefly local aggregate or groundwater significance. Pyritic rock and steep spoil or roadcut exposures warrant caution. ## Field context - Thin sandstone ledges can detach above weathered shale slopes. - Many exposures are along roads or on private land and are not safe or open collecting sites. - Use modern Pennsylvania maps because Chemung terminology persists in older literature. ## Connected field guides - Sandstone (rock; Named rock type and mineral context) — https://lithomap.app/resources/rock-identification/sandstone - Shale (rock; Named rock type and mineral context) — https://lithomap.app/resources/rock-identification/shale - Conglomerate (rock; Named rock type) — https://lithomap.app/resources/rock-identification/conglomerate - Siltstone (rock; Named rock type) — https://lithomap.app/resources/rock-identification/siltstone - Calcite (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/calcite - 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 Lock Haven references — U.S. Geological Survey: https://ngmdb.usgs.gov/Geolex/UnitRefs/LockHavenRefs_2515.html - Stratigraphic nomenclature changes — U.S. Geological Survey: https://pubs.usgs.gov/bul/1457a/report.pdf ## Formation photograph - Image: https://lithomap.app/_delivery/formations/lock-haven-formation.webp - Description: Dense brachiopod casts in Lock Haven Formation rock at Leberfinger Quarry, Pennsylvania - Creator: James Stuby - License: Public domain — https://creativecommons.org/publicdomain/mark/1.0/ - Source record: https://commons.wikimedia.org/wiki/File:Brachiopods_Leberfinger_quarry.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.