Mineral Resources On-Line Spatial Data
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Geologic units in Northumberland county, Pennsylvania
- Hamilton Group (Devonian) at surface, covers 22 % of this area
Hamilton Group - Includes, in descending order, the Mahantango (Dmh) and Marcellus (Dmr) Formations.
- Mauch Chunk Formation (Mississippian) at surface, covers 6 % 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.
- Clinton Group (Silurian) at surface, covers 1 % of this area
Clinton Group - Predominantly Rose Hill Formation--light-olive-gray to brownish-gray, fossiliferous shale; locally, limestone occurs near top; includes dark-reddish-gray, very fine to coarse-grained, ferruginous sandstone; east of Harrisburg, equivalent to Lizard Creek Member of Shawangunk Formation. Above Rose Hill is Keefer Formation--light- to dark-gray, fossiliferous sandstone, hematitic, oolitic sandstone, and shale; not recognized east of Harrisburg.
- Irish Valley Member of Catskill Formation (Devonian) at surface, covers 13 % 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.
- Buddys Run Member of Catskill Formation (Devonian) at surface, covers 4 % 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.
- Wills Creek Formation (Silurian) at surface, covers 5 % of this area
Wills Creek Formation - Variegated gray, grayish-red, yellowish-gray and greenish-gray, interbedded calcareous shale, siltstone, shaly limestone, and dolomite; passes into Bloomsburg Formation in the southeast; not present east of Harrisburg.
- 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.
- Onondaga and Old Port Formations, undivided (Devonian) at surface, covers 3 % 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).
- Tuscarora Formation (Silurian) at surface, covers 0.9 % of this area
Tuscarora Formation - Light- to medium-gray quartzite and quartzitic sandstone and minor interbedded shale and siltstone, locally conglomeratic in lower part; includes (to the northwest) interbedded red and non-red sandstone (Castanea Member) at top; east of Harrisburg, equivalent to Minsi and Weiders Members of Shawangunk Formation.
- Pottsville Formation (Pennsylvanian) at surface, covers 3 % 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.
- Trimmers Rock Formation (Devonian) at surface, covers 16 % 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.
- Bloomsburg and Mifflintown Formations, undivided (Silurian) at surface, covers 3 % of this area
Bloomsburg and Mifflintown Formations, undivided - Includes, in descending order, the Bloomsburg Formation (Sb) and the Mifflintown Formation--interbedded dark-gray shale and medium-gray fossiliferous limestone; equivalent to "McKenzie" and "Rochester" of earlier workers; not present east of Harrisburg.
- Keyser and Tonoloway Formations, undivided (Devonian and Silurian) at surface, covers 5 % of this area
Keyser and Tonoloway Formations, undivided - In descending order: Keyser Formation--medium-gray, crystalline to nodular, fossiliferous limestone; upper part laminated and mud-cracked; not present east of Harrisburg; passes into lower Coeymans, Rondout, and Decker Formations in the east. Tonoloway Formation--medium-gray, laminated, mud-cracked limestone containing some medium-dark- or olive-gray shale interbeds; lower part passes into Wills Creek Formation east and south; passes into Bossardville and Poxono Island beds in the east.
- Spechty Kopf Formation (Mississippian and Devonian) at surface, covers 1.0 % 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.
- Llewellyn Formation (Pennsylvanian) at surface, covers 9 % of this area
Llewellyn Formation - Gray, fine- to coarse-grained sandstone, siltstone, shale, conglomerate, and numerous anthracite coals in repetitive sequences.
- 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.
- Sherman Creek Member of Catskill Formation (Devonian) at surface, covers 3 % 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.