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Mineral Resources > Online Spatial Data > Geology > by state > Pennsylvania Geology

Geologic units in Schuylkill county, Pennsylvania

Shawangunk Formation (Silurian) at surface, covers 3 % of this area

Shawangunk Formation - Light- to dark-gray, fine- to very coarse grained sandstone and conglomerate containing thin shale interbeds. Includes four members, in descending order: Tammany--conglomerate and sandstone; Lizard Creek--sandstone and red or green shale; Minsi--sandstone and conglomerate; Weiders--conglomerate. Tammany and Lizard Creek Members together are approximately equivalent to Clinton Group to the west; Minsi and Weiders Members together are equivalent to Tuscarora Formation to the west.

Lithology: sandstone; conglomerate; shale

Decker Formation through Poxono Island Formation, undivided (Silurian) at surface, covers 0.2 % of this area

Decker Formation through Poxono Island Formation, undivided -In descending order: Decker Formation--gray calcareous sandstone having lenses of calcareous conglomerate, siltstone, and shale, and lenses of limestone and dolomite (in Stroudsburg area, includes calcareous shale, limestone, and dolomite of Rondout Formation at top); Bossardville Limestone--gray argillaceous limestone and dolomitic limestone; Poxono Island Formation--thin-bedded dolomite, limestone, and shale; red shale in lower part. This undivided succession is equivalent to Keyser, Tonoloway, and Wills Creek (part) Formations of central Pennsylvania.

Lithology: dolostone (dolomite); limestone; siltstone; shale; sandstone; conglomerate

Beaverdam Run Member of Catskill Formation (Devonian) at surface, covers 2 % of this area

Beaverdam Run Member of Catskill Formation - Alternating olive-gray siltstone and sandstone; marine fossils.

Lithology: siltstone; sandstone

Trimmers Rock Formation (Devonian) at surface, covers 4 % of this area

Trimmers Rock Formation - Olive-gray siltstone and shale, characterized by graded bedding; marine fossils; some very fine grained sandstone in northeast; black shale of Harrell Formation at base in Susquehanna Valley.

Lithology: siltstone; shale; sandstone; black shale

Towamensing Member of Catskill Formation (Devonian) at surface, covers 0.4 % of this area

Towamensing Member of Catskill Formation - Dominantly gray sandstone and some siltstone and shale; freshwater fossils.

Lithology: sandstone; siltstone; shale

Llewellyn Formation (Pennsylvanian) at surface, covers 17 % of this area

Llewellyn Formation - Gray, fine- to coarse-grained sandstone, siltstone, shale, conglomerate, and numerous anthracite coals in repetitive sequences.

Lithology: sandstone; siltstone; shale; conglomerate; coal

Spechty Kopf Formation (Mississippian and Devonian) at surface, covers 1 % of this area

Spechty Kopf Formation - Light- to olive-gray, fine- to medium- grained, crossbedded sandstone, siltstone, and local polymictic diamictite, pebbly mudstone, and laminite; arranged in crude fining-upward cycles in some places; locally has grayish-red shale near top and conglomerate at base and in middle.

Lithology: sandstone; siltstone; mudstone; shale; conglomerate

Pocono Formation (Mississippian) at surface, covers 3 % of this area

Pocono Formation - Light-gray to buff or light-olive-gray, medium-grained, crossbedded sandstone and minor siltstone; commonly conglomeratic at base and in middle; medial conglomerate, where present, is used to divide into Mount Carbon and Beckville Members; equivalent to Burgoon Sandstone of Allegheny Plateau.

Lithology: sandstone; siltstone; conglomerate

Sherman Creek Member of Catskill Formation (Devonian) at surface, covers 4 % of this area

Sherman Creek Member of Catskill Formation - Alternating grayish-red mudstone and siltstone in poorly defined fining-upward cycles, and minor intervals of gray sandstone; laterally equivalent to Berry Run, Sawmill Run, Packerton, and Long Run Members of eastern Pennsylvania.

Lithology: mudstone; siltstone; sandstone

Marcellus Formation (Devonian) at surface, covers 0.2 % of this area

Marcellus Formation - Black shale; sparse marine fauna and siderite concretions. Contains local limestone ("Purcell") member. Tioga bentonite included at base in eastern Pennsylvania.

Lithology: black shale; limestone; bentonite

Mahantango Formation (Devonian) at surface, covers 0.4 % of this area

Mahantango Formation - Gray, brown, and olive shale and siltstone; marine fossils. Includes the following members, in descending order: Tully-argillaceous limestone; Sherman Ridge, Montebello (sandstone), Fisher Ridge, Dalmatia, and Turkey Ridge. In south-central Pennsylvania, includes Clearville, Frame, Chaneysville, and Gander Run Members. Characterized by coarsening-upward cycles.

Lithology: shale; siltstone; limestone; sandstone

Bloomsburg Formation (Silurian) at surface, covers 6 % of this area

Bloomsburg Formation - Grayish-red siltstone, shale, and sandstone arranged in fining-upward cycles.

Lithology: siltstone; shale; sandstone

Pottsville Formation (Pennsylvanian) at surface, covers 14 % of this area

Pottsville Formation - 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.

Lithology: sandstone; conglomerate; shale; siltstone; claystone; limestone; coal

Onondaga Formation through Poxono Island Formation, undivided (Devonian and Silurian) at surface, covers 1.0 % of this area

Onondaga Formation through Poxono Island Formation, undivided - In descending order: Onondaga Formation--gray calcareous, sandy shale; Ridgeley Formation--brown sandstone; Rondout Formation--gray interbedded limestone, dolomite, and shale; Decker Formation--gray calcareous sandstone, and Andreas Red Beds at top; Bossardville Limestone--gray, mud-cracked shaly limestone; Poxono Island Formation--olive-gray, calcareous and dolomitic shale, siltstone, and sandstone.

Lithology: shale; sandstone; limestone; dolostone (dolomite); clastic; siltstone

Packerton Member of Catskill Formation (Devonian) at surface, covers 0.2 % of this area

Packerton Member of Catskill Formation - Greenish-gray to gray sandstone and some siltstone; some laterally persistent conglomerate beds in lower part.

Lithology: sandstone; siltstone; conglomerate

Long Run Member of Catskill Formation (Devonian) at surface, covers 4 % of this area

Long Run Member of Catskill Formation - Gray and grayish-red sandstone and grayish-red siltstone and mudstone in fining-upward cycles.

Lithology: sandstone; siltstone; mudstone

Walcksville and Towamensing Members of Catskill Formation, undivided (Devonian) at surface, covers 1 % of this area

Walcksville and Towamensing Members of Catskill Formation, undivided - Includes, in descending order, the Walcksville Member (Dcw) of the Catskill Formation, and the Towamensing Member (Dct).

Lithology: sandstone; siltstone; mudstone; shale

Duncannon Member of Catskill Formation (Devonian) at surface, covers 3 % of this area

Duncannon Member of Catskill Formation - Grayish-red sandstone, siltstone, and mudstone in fining-upward cycles; conglomerate occurs at base of some cycles.

Lithology: sandstone; siltstone; mudstone; conglomerate

Berry Run and Sawmill Run Members of Catskill Formation, undivided (Devonian) at surface, covers 0.4 % of this area

Berry Run and Sawmill Run Members of Catskill Formation, undivided - Greenish-gray to gray sandstone and minor red siltstone and mudstone.

Lithology: sandstone; siltstone; mudstone

Walcksville Member of Catskill Formation (Devonian) at surface, covers 0.5 % of this area

Walcksville Member of Catskill Formation - Greenish-gray sandstone and red siltstone and mudstone in fining-upward cycles.

Lithology: sandstone; siltstone; mudstone

Onondaga and Old Port Formations, undivided (Devonian) at surface, covers 0.2 % of this area

Onondaga and Old Port Formations, undivided - Includes, in descending order, the Onondaga Formation (Don), Ridgeley Member of Old Port Formation (Dor), and Shriver, Mandata, Corriganville, and New Creek Members of Old Port Formation, undivided (Dosn).

Lithology: shale; sandstone; limestone; chert; shale; siltstone; bentonite

Mauch Chunk Formation (Mississippian) at surface, covers 25 % of this area

Mauch Chunk Formation - Grayish-red shale, siltstone, sandstone, and some conglomerate; some local nonred zones. Includes Loyalhanna Member (crossbedded, sandy limestone) at base in south-central and southwestern Pennsylvania; also includes Greenbrier Limestone Member, and Wymps Gap and Deer Valley Limestones, which are tongues of the Greenbrier. Along Allegheny Front from Blair County to Sullivan County, Loyalhanna Member is greenish-gray, calcareous, crossbedded sandstone.

Lithology: shale; siltstone; sandstone; conglomerate; limestone

Clarks Ferry Member of Catskill Formation (Devonian) at surface, covers 0.7 % of this area

Clarks Ferry Member of Catskill Formation - Gray to yellowish-gray sandstone, siltstone, and conglomerate.

Lithology: sandstone; siltstone; conglomerate

Hamilton Group (Devonian) at surface, covers 6 % of this area

Hamilton Group - Includes, in descending order, the Mahantango (Dmh) and Marcellus (Dmr) Formations.

Lithology: black shale; shale; siltstone; limestone; sandstone; bentonite

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

Irish Valley Member of Catskill Formation - Nonmarine, grayish-red siltstone and mudstone, and gray and grayish-red sandstone interbedded with minor, thin, light-olive-gray marine siltstone; arranged in fining-upward cycles. Lower part of member has conglomeratic sandstones.

Lithology: siltstone; mudstone; sandstone; conglomerate

Martinsburg Formation (Ordovician) at surface, covers < 0.1 % of this area

Martinsburg Formation - Gray to dark-gray, buff-weathering shale.

Lithology: shale

Buddys Run Member of Catskill Formation (Devonian) at surface, covers < 0.1 % of this area

Buddys Run Member of Catskill Formation - Grayish-red and brownish-gray siltstone, mudstone, and sandstone; some gray and dusky-yellow sandstone and siltstone; laterally equivalent to Duncannon, Clarks Ferry, and Sherman Creek Members.

Lithology: siltstone; sandstone; mudstone