Geologic units in Bradford county, Pennsylvania

Lock Haven Formation (Devonian) at surface, covers 58 % of this area

Interbedded olive-gray mudstone, siltstone, sandstone, and thin conglomerate; marine fossils throughout; "Chemung" of earlier workers. Laterally equivalent to Scherr and Foreknobs Formations.

Catskill Formation (Devonian) at surface, covers 29 % of this area

Grayish-red sandstone, siltstone, shale, and mudstone; units of gray sandstone occur in upper part; lithologies in upper part arranged in fining-upward cycles. In the Altoona area, the Catskill Formation is mapped as the Duncannon, Sherman Creek, and Irish Valley Members, which are described under "Central and Eastern Pennsylvania" provinces.

Huntley Mountain Formation (Mississippian and Devonian) at surface, covers 7 % of this area

Greenish-gray and light-olive-gray, flaggy, fine-grained sandstone, siltstone, and a few red shale interbeds; includes lower "Pocono" plus "Oswayo" of earlier workers. Forms transition between Catskill Formation and Burgoon Sandstone.

Burgoon Sandstone (Mississippian) at surface, covers 3 % of this area

Buff, medium-grained, crossbedded sandstone; includes shale and coal; in places, contains conglomerate at base; contains plant fossils; equivalent to Pocono Formation of Ridge and Valley province.

Pottsville Formation (Pennsylvanian) at surface, covers 2 % of this area

Predominantly gray sandstone and conglomerate; also contains thin beds of shale, claystone, limestone, and coal; includes Olean and Sharon conglomerates of northwestern Pennsylvania; thin marine limestones present in Beaver, Lawrence, and Mercer Counties; minable coals and commercially valuable high-alumina clays present locally.

Catskill Formation (Devonian) at surface, covers 1 % of this area

Succession of grayish-red sandstone, siltstone, shale, and mudstone, generally in fining-upward cycles; some gray sandstone and conglomerate.

Allegheny and Pottsville Formations, undivided (Pennsylvanian) at surface, covers 0.4 % of this area

Sandstone, shale, and some coal; includes lower Pottsville conglomerate and overlying strata equivalent to Allegheny Formation in north-central outliers; formational boundary not determined due to lack of correlation with Brookville-Clarion coal.

Gardeau Formation (Upper Devonian) at surface, covers < 0.1 % of this area

Shale, siltstone; Roricks Glen Shale.

Nunda Formation, West Hill Formation (Upper Devonian) at surface, covers < 0.1 % of this area

Nunda: sandstone, shale; West Hill: shale, siltstone; Corning Shale.

Upper Walton Formation (Upper Devonian) at surface, covers < 0.1 % of this area

Shale, sandstone, conglomerate.

Beers Hill, Dunn Hill, Millport, and Moreland Shales; Grimes Siltstone (Upper Devonian) at surface, covers < 0.1 % of this area

Beers Hill, Dunn Hill, Millport, and Moreland Shales; Grimes Siltstone.

Wiscoy Formation (Upper Devonian) at surface, covers < 0.1 % of this area

Sandstone, shale; Hanover and Pipe Creek Shales.