Geologic units in Schuylkill county, Pennsylvania

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

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.

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

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

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

Gray conglomerate, fine- to coarse-grained sandstone, and siltstone and shale containing minable anthracite coals. Includes three members, in descending order: Sharp Mountain--conglomerate and conglomeratic sandstone; Schuylkill--sandstone and conglomeratic sandstone; Tumbling Run--conglomeratic sandstone and sandstone.

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

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

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

Grayish-red and greenish-gray shale, siltstone, and very fine to coarse-grained sandstone; some calcareous mudstone in central Pennsylvania; thins to west and is replaced by Mifflintown beds; thickens eastward, replacing overlying Wills Creek and Tonoloway Formations and underlying Mifflintown Formation.

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

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.

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

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.

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

Gray and grayish-red sandstone and grayish-red siltstone and mudstone in fining-upward cycles.

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

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.

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

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.

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

Alternating olive-gray siltstone and sandstone; marine fossils.

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

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

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

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.

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

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.

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

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

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

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.

Duncannon Member of Catskill Formation (Devonian) at surface, covers 0.8 % of this area

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

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

Gray to yellowish-gray sandstone, siltstone, and conglomerate.

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

Greenish-gray sandstone and red siltstone and mudstone in fining-upward cycles.

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

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.

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

Greenish-gray to gray sandstone and minor red siltstone and mudstone.

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

Dominantly gray sandstone and some siltstone and shale; freshwater fossils.

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

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).

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

Greenish-gray to gray sandstone and some siltstone; some laterally persistent conglomerate beds in lower part.

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

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.

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

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

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

Gray to yellowish-gray sandstone and conglomerate.

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

Gray to dark-gray shale and slate.

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

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.