USGS Home
Contact USGS
Search USGS

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

Geologic units in Pennsylvania (state in United States)

[Additional scientific data in this geographic area]

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.

Lithology: shale; sandstone; limestone

Burgoon Sandstone (Mississippian) at surface, covers 2 % of this area

Burgoon Sandstone - 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.

Lithology: sandstone; conglomerate; shale; coal

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

Slide Mountain Formation - sandstone, shale, conglomerate.

Lithology: sandstone; shale; conglomerate

Mauch Chunk Formation (Mississippian) at surface, covers 3 % 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

Packerton Member of Catskill Formation (Devonian) at surface, covers < 0.1 % 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

Hamilton Group (Devonian) at surface, covers 2 % of this area

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

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

Bellefonte Formation (Ordovician) at surface, covers 0.2 % of this area

Bellefonte Formation - Medium-gray, brownish-weathering, medium-bedded dolomite and minor sandstone; very fine grained Tea Creek Member above, and crystalline Coffee Run Member below.

Lithology: dolostone (dolomite); sandstone

Gettysburg Shale (Triassic) at surface, covers < 0.1 % of this area

Gettysburg Shale - Red shale and soft red sandstone and siltstone; estimated thickness less than 5,000 feet.

Lithology: shale; sandstone; siltstone

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

Wiscoy Formation - sandstone, shale; Hanover and Pipe Creek Shales.

Lithology: sandstone; black shale; shale

Glenshaw Formation (Pennsylvanian) at surface, covers 7 % of this area

Glenshaw Formation - Cyclic sequences of shale, sandstone, red beds, and thin limestone and coal; includes four marine limestone or shale horizons; red beds are involved in landslides; base is at top of Upper Freeport coal.

Lithology: shale; sandstone; limestone; clastic; coal

Lower (Middle?) Cambrian rocks, undivided (Cambrian) at surface, covers < 0.1 % of this area

Lower (Middle?) Cambrian rocks, undivided - Lower Cambrian of Berks County includes tectonic slices of many of the following rock units: Zooks Corner (CAzc), Ledger (CAl), Kinzers (CAk), Vintage (CAv), Antietam (CAa, CAah), and Harpers (CAh, CAah) Formations.

Lithology: dolostone (dolomite); limestone; shale; quartzite; phyllite; schist; marble

Irish Valley Member of Catskill Formation (Devonian) at surface, covers 0.7 % 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

Shenango Formation through Oswayo Formation, undivided (Mississippian and Devonian) at surface, covers 1 % of this area

Shenango Formation through Oswayo Formation, undivided - Greenish-gray, olive, and buff sandstone and siltstone, and gray shale in varying proportions; includes "Pocono" ("Knapp") and Oswayo of earlier workers; difficult lithologic distinction between Oswayo and "Knapp"- "Pocono" south and east of type area at Olean, N. Y.; contains marine fossils; includes lateral equivalents of Shenango Formation, Cuyahoga Group, Corry Sandstone, Bedford Shale, and Cussewago Sandstone, plus Oswayo Formation.

Lithology: sandstone; siltstone; shale

Shawangunk Formation (Silurian) at surface, covers 0.2 % 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

Pottsville Formation (Pennsylvanian) at surface, covers 8 % 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

Spechty Kopf Formation (Mississippian and Devonian) at surface, covers 0.3 % 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

Ledger Formation (Cambrian) at surface, covers 0.2 % of this area

Ledger Formation - Light-gray, locally mottled, massive, pure, coarsely crystalline dolomite; siliceous in middle part.

Lithology: dolostone (dolomite)

Bald Eagle Formation (Ordovician) at surface, covers 0.4 % of this area

Bald Eagle Formation - Gray to olive-gray and grayish-red, fine- to coarse-grained, crossbedded sandstone, siltstone, and shale; some conglomerate (Lost Run Member); not present east of Susquehanna River, except at Spitzenberg Hill area (Berks County).

Lithology: sandstone; siltstone; shale; conglomerate

Long Run Member of Catskill Formation (Devonian) at surface, covers 0.3 % 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

Diabase (Jurassic) at surface, covers 0.6 % of this area

Diabase - Medium- to coarse-grained, quartz-normative tholeiite; composed of labradorite and various pyroxenes; occurs as dikes, sheets, and a few small flows. Includes the dark-gray York Haven Diabase (high titanium oxide) and the slightly younger Rossville Diabase (low titanium oxide). In chilled margins, the Rossville is distinguished from the York Haven by its lighter gray color and distinctive, sparse, centimeter-sized calcic-plagioclase phenocrysts.

Lithology: diabase

Buttermilk Falls Limestone and Onondaga Limestones, undivided (Middle Devonian) at surface, covers < 0.1 % of this area

Buttermilk Falls Limestone and Onondaga Limestones, undivided - Buttermilk Falls Limestone in southwestern part of outcrop belt grades into Onondaga Limestone along strike to northeast. The transition occurs north of Millville. Buttermilk Falls Limestone (Middle Devonian) (Willard, 1938) - Light- to medium-light-gray-weathering, medium- to dark-gray, thin- to medium-bedded, fossiliferous, flaggy, clayey to silty limestone and nodular black chert. Lower contact grades downward through several meters (feet) of silty limestone to interbedded limestone and calcareous siltstone of the Schoharie Formation. Thickness is approximately 82 m (270 ft). Onondaga Limestone (Middle Devonian) (Vanuxem 1840) - Light-medium-gray- weathering, medium gray, fine-grained, thin- to thick-bedded fossiliferous limestone. Black chert more abundant in upper half of unit. Lower contact grades into interbedded limestone and calcareous siltstone of the Schoharie Formation. Thickness approximately 60 m (200ft).

Lithology: limestone; chert

Martinsburg Formation (Ordovician) at surface, covers 1 % of this area

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

Lithology: shale

Onondaga and Old Port Formations, undivided (Devonian) at surface, covers 0.5 % 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

Keyser Formation through Mifflintown Formation, undivided (Devonian and Silurian) at surface, covers 0.1 % of this area

Keyser Formation through Mifflintown Formation, undivided - In descending order: Keyser Formation--limestone; Tonoloway Formation--limestone and interbedded shale; Wills Creek Formation--interbedded shale, siltstone, limestone, and dolomite; Bloomsburg Formation--grayish-red and greenish-gray shale, siltstone, sandstone, and mudstone; Mifflintown Formation--interbedded shale and limestone.

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

Llewellyn Formation (Pennsylvanian) at surface, covers 0.8 % 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

Juniata and Bald Eagle Formations, undivided (Ordovician) at surface, covers 0.1 % of this area

Juniata and Bald Eagle Formations, undivided - Includes, in descending order, the Juniata (Oj) and Bald Eagle (Obe) Formations.

Lithology: sandstone; siltstone; shale; conglomerate

Foreknobs Formation (Devonian) at surface, covers 0.5 % of this area

Foreknobs Formation - Interbedded sandstone, siltstone, and shale; gray to olive gray, red near top; substantial brownish-gray sandstone; some marine fossils; a few conglomerate beds at base and top.

Lithology: sandstone; siltstone; shale; conglomerate

St. Paul Group (Ordovician) at surface, covers 0.2 % of this area

St. Paul Group - Very finely crystalline, "birdseye" limestone at top and base, granular fossiliferous limestone, black chert, and dolomite in middle.

Lithology: limestone; chert; dolostone (dolomite)

Stonehenge/Larke Formation (Ordovician) at surface, covers < 0.1 % of this area

Stonehenge/Larke Formation - Medium-gray, medium-bedded to laminated, fossiliferous, oolitic limestone containing edgewise conglomerate; to the west, Stonehenge is laterally equivalent to medium- to dark-gray, coarsely crystalline dolomite (Larke).

Lithology: limestone; dolostone (dolomite); conglomerate

Millbach Formation (Cambrian) at surface, covers < 0.1 % of this area

Millbach Formation - Pink to white and gray, finely laminated limestone and interbedded finely crystalline dolomite; numerous stromatolitic limestone beds.

Lithology: limestone; dolostone (dolomite)

Felsic to mafic gneiss (Precambrian) at surface, covers 0.4 % of this area

Felsic to mafic gneiss - Light, medium grained; predominantly quartz and feldspar of igneous origin.

Lithology: felsic gneiss; mafic gneiss; orthogneiss

Decker Formation through Poxono Island Formation, undivided (Silurian) at surface, covers < 0.1 % 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

Antietam and Harpers Formations, undivided (Cambrian) at surface, covers 0.3 % of this area

Antietam and Harpers Formations, undivided - Includes, in descending order, the Antietam (CAa) and Harpers (CAh) Formations. Antietam Formation - gray, buff-weathering quartzite. Harpers Formation - Dark-greenish-gray phyllite and schist containing thin quartzite layers; includes Montalto Member (CAhm) - gray quartztite

Lithology: quartzite; schist; phyllite

Vintage Formation (Cambrian) at surface, covers 0.1 % of this area

Vintage Formation - Dark-gray, knotty, argillaceous dolomite; impure light-gray marble at base locally.

Lithology: dolostone (dolomite); marble

Keyser Formation through Clinton Group, undivided (Devonian and Silurian) at surface, covers < 0.1 % of this area

Keyser Formation through Clinton Group, undivided - Same as Keyser-through-Mifflintown (DSkm) interval, plus Clinton Group at base. Clinton includes the following, in descending order: Keefer Formation--fossiliferous sandstone and hematitic, oolitic sandstone and shale; Rose Hill Formation--fossiliferous shale.

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

Catskill Formation (Devonian) at surface, covers 10 % of this area

Catskill Formation - Grayish-red sandstone, siltstone, shale, and mudstone; locally conglomeratic; contains gray sandstone in upper part; lithologies arranged in fining-upward cycles; equivalent to the Hampshire Formation south of Pennsylvania.

Lithology: sandstone; siltstone; shale; mudstone; conglomerate

Mafic gneiss (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Mafic gneiss - Dark, medium grained; includes rocks of probable sedimentary origin; may be equivalent to pCAmgp in places.

Lithology: mafic gneiss; paragneiss

Shenango Formation through Riceville Formation, undivided (Mississippian and Devonian) at surface, covers 0.2 % of this area

Shenango Formation through Riceville Formation, undivided - Sandstone, siltstone, and shale in varying proportions; distinguished from Shenango-through-Oswayo (MDso) interval on basis of more common gray shale in Riceville as compared with olive-colored shale and sandstone of Oswayo; contains marine fossils.

Lithology: sandstone; siltstone; shale

Wissahickon Formation (Probably lower Paleozoic) at surface, covers 0.3 % of this area

Wissahickon Formation - Includes oligoclase-mica schist, some hornblende gneiss, some augen gneiss, and some quartz-rich and feldspar-rich members due to various degrees of granitization.

Lithology: mica schist; mafic gneiss; augen gneiss; granitoid

Duncannon Member of Catskill Formation (Devonian) at surface, covers 0.9 % 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

Lock Haven Formation (Devonian) at surface, covers 3 % of this area

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

Lithology: mudstone; siltstone; sandstone; conglomerate

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

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

Lithology: siltstone; sandstone

Esopus Formation (Lower Devonian) at surface, covers < 0.1 % of this area

Esopus Formation (Vanuxem, 1842) - Medium-gray weathering, medium- to dark-gray, laminated to medium-bedded, partly massive, shaly to finely arenaceous siltstone, containing minor calcareous siltstone near top, locally limonite stained. Contains Taonurus. Rocks are cleaved in southwest and extreme northeast part of outcrop belt but not in central region. Lower contact sharp and unconformable where underlying Oriskany Group is coarse quartz sandstone. Elsewhere, lower contact conformable; fine sandstone to siltstone grades downward several meters into silty limestone. Thickness approximately 91 m (300 ft).

Lithology: siltstone

Felsic and intermediate gneiss (Precambrian) at surface, covers 0.1 % of this area

Felsic and intermediate gneiss - Medium grained, light pink to greenish gray; largely quartz, feldspar, and mica; commonly gneissic, containing alteration minerals; interfingers with gabbroic gneiss.

Lithology: felsic gneiss; gneiss

Pocono Group, including the Purslane Sandstone and Rockwell Formation (Mississippian) at surface, covers < 0.1 % of this area

Pocono Group - Gray, white, tan, and brown, thin- to thick-bedded, cross-bedded sandstone, locally conglomeratic; interbedded gray and reddish-brown shale, mudstone, and siltstone; fragmentary plant fossils. Undifferentiated in Garrett and western Allegeny Counties. Includes Purslane Sandstone - White, thick-bedded, coarse-grained sandstone and conglomerate with thin coal beds and red shales. Eastern Allegany and Washington Counties. And also inlcudes Rockwell Formation - Coarse-grained arkosic sandstone, fine-grained conglomerate, and buff shale; dark shale with thin coal beds near base. Eastern Allegany and Washington Counties.

Lithology: sandstone; shale; mudstone; siltstone; conglomerate; coal

Juniata Formation (Ordovician) at surface, covers 0.7 % of this area

Juniata Formation - Grayish-red, very fine to medium-grained, crossbedded sandstone, and grayish-red siltstone and shale; merges with underlying Bald Eagle Formation to the south; not present east of Susquehanna River, except at Spitzenberg Hill area (Berks County).

Lithology: sandstone; shale; siltstone

Conemaugh Group (Pennsylvanian) at surface, covers < 0.1 % of this area

Conemaugh Group - Includes, in descending order, the Casselman Formation (PAcc) and the Glenshaw Formation (PAcg), which are described separately below. Casselman: Cyclic sequences of shale, siltstone, sandstone, red beds, thin, impure limestone, and thin, nonpersistent coal; red beds are associated with landslides; base is at top of Ames limestone. Glenshaw: Cyclic sequences of shale, sandstone, red beds, and thin limestone and coal; includes four marine limestone or shale horizons; red beds are involved in landslides; base is at top of Upper Freeport coal.

Lithology: shale; siltstone; sandstone; clastic; limestone; coal

Allegheny Formation (Pennsylvanian) at surface, covers 7 % of this area

Allegheny Formation - Cyclic sequences of sandstone, shale, limestone, clay, and coal; includes valuable clay deposits and Vanport Limestone; commercially valuable Freeport, Kittanning, and Brookville-Clarion coals present; base is at bottom of Brookville-Clarion coal.

Lithology: sandstone; shale; limestone; clay or mud; coal

Rockdale Run Formation (Ordovician) at surface, covers 0.2 % of this area

Rockdale Run Formation - Mostly limestone; some dolomite interbeds; some chert near middle and top; stromatolitic limestone in middle; pinkish marbleoid limestone and chert at base.

Lithology: limestone; dolostone (dolomite); chert

Keyser and Tonoloway Formations, undivided (Devonian and Silurian) at surface, covers 0.7 % 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.

Lithology: limestone; shale

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

Limestone of Martinsburg Formation - Dark-gray, thin-bedded, platy argillaceous limestone containing some beds of shale.

Lithology: limestone; shale

Marburg Schist (Late Precambrian (?)) at surface, covers < 0.1 % of this area

Marburg Schist - Bluish-gray to silvery-green, fine-grained, muscovite-chlorite-albite-quartz schist; intensely cleaved and closely folded; contains interbedded quartzites.

Lithology: mica schist; quartzite

Hardyston Quartzite (Lower Cambrian) at surface, covers < 0.1 % of this area

Hardyston Quartzite (Lower Cambrian) (Wolff and Brooks, 1898) - Light- to medium-gray and bluish-gray conglomeratic sandstone. Varies from pebble conglomerate, to fine-grained, well-cemented quartzite, to arkosic or dolomitic sandstone. Conglomerate contains subangular to subrounded white quartz pebbles up to 2.5 cm (1 in.). Lower contact unconformable. About 0 to 9 m (1-30 ft) thick.

Lithology: quartzite; conglomerate; sandstone

Banded mafic gneiss (Precambrian) at surface, covers < 0.1 % of this area

Banded mafic gneiss - Dark, fine to medium grained; includes rocks of probable sedimentary origin; may be equivalent to "PZmgh."

Lithology: mafic gneiss; paragneiss

Reedsville Formation (Ordovician) at surface, covers 0.6 % of this area

Reedsville Formation - Olive-gray to dark-gray shale, siltstone, and fine-grained, thin-bedded sandstone having graded bedding; upper sandstone is very fossiliferous; includes Antes Formation (black calcareous shale) at base along Nittany Arch.

Lithology: shale; siltstone; sandstone; black shale

Metabasalt (Precambrian) at surface, covers < 0.1 % of this area

Metabasalt - Dark-gray, fine-grained intrusives; locally, mineralogy is altered and unit has greenish color.

Lithology: meta-basalt

Trimmers Rock Formation (Devonian) at surface, covers 1 % 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

Monongahela Group (Pennsylvanian) at surface, covers 2 % of this area

Monongahela Group - Cyclic sequences of limestone, shale, sandstone, and coal; commercial coals present; base is at bottom of Pittsburgh coal.

Lithology: limestone; shale; sandstone; coal

Tuscarora Formation (Silurian) at surface, covers 1 % 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.

Lithology: quartzite; sandstone; shale; siltstone; conglomerate

Washington Formation (Permian) at surface, covers 0.7 % of this area

Washington Formation - Cyclic sequences of sandstone, shale, limestone, and coal; includes some red shale; base is at bottom of Washington coal.

Lithology: sandstone; shale; limestone; coal

Mafic gneiss (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Mafic gneiss - Dark, medium grained; includes rocks of probable sedimentary origin; may be equivalent to pCAmgh in places.

Lithology: mafic gneiss; paragneiss

Sands of Presque Isle (Quaternary) at surface, covers < 0.1 % of this area

Sands of Presque Isle - Fine-grained, unconsolidated sand deposited by lake currents.

Lithology: sand

Hammer Creek conglomerate (Triassic) at surface, covers 0.2 % of this area

Hammer Creek conglomerate - Cobble and pebble quartz conglomerate interbedded with red sandstone.

Lithology: conglomerate; sandstone

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

Onondaga Formation - Medium-gray calcareous shale; marine fossils; medium-gray argillaceous limestone of Selinsgrove Member at top; called "Needmore Formation" west of 78° longitude; Tioga bentonite at top.

Lithology: shale; limestone; bentonite

Dunkard Group (Permian/Pennsylvanian) at surface, covers < 0.1 % of this area

Dunkard Group - non-marine cyclic sequences of sandstone, siltstone, red and gray shale, limestone, and coal. Contains the Greene, Washington and Waynesburg Formations. Extends from the top of the exposed bed rock section to the top of the Waynesburg coal. Includes the Washington coals and limestones. Palynological evidence favors a Pennsylvanian age, at least for the lower portion.

Lithology: sandstone; siltstone; shale; limestone; coal

Shenango Formation through Cuyahoga Group, undivided (Mississippian) at surface, covers 0.5 % of this area

Shenango Formation through Cuyahoga Group, undivided - includes the Shenango Formation (Ms) and Cuyahoga Group (Mc), which are described separately below. Shenango: Light-gray sandstone and some beds of medium-gray shale and siltstone; upper third of formation is more shaly; contains a few marine fossils. Cuyahoga: Medium-gray siltstone and dark-gray shale containing interbedded light-gray, flaggy sandstone. Includes, in descending order: Meadville Shale, Sharpsville Sandstone, and Orangeville Shale; marine fossils common.

Lithology: sandstone; siltstone; shale

Granitic gneiss and granite (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Granitic gneiss and granite - Includes Springfield Granodiorite (granitized Wissahickon) in Philadelphia area.

Lithology: granitic gneiss; granite; granodiorite

Gettysburg conglomerate (Triassic) at surface, covers < 0.1 % of this area

Gettysburg conglomerate - Gray quartz conglomerate, sandstone, and red siltstone and mudstone.

Lithology: conglomerate; sandstone; siltstone; mudstone

Ultramafic rocks (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Ultramafic rocks - Includes serpentine, steatite, and other products of alteration of peridotites and pyroxenites.

Lithology: serpentinite; pyroxenite; peridotite

Allegheny and Pottsville Formations, undivided (Pennsylvanian) at surface, covers 0.1 % of this area

Allegheny and Pottsville Formations, undivided - 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.

Lithology: sandstone; shale; conglomerate; coal

Tomstown Formation (Cambrian) at surface, covers 0.1 % of this area

Tomstown Formation - Massive dolomite containing thin shaly interbeds.

Lithology: dolostone (dolomite); shale

Casselman Formation (Pennsylvanian) at surface, covers 3 % of this area

Casselman Formation - Cyclic sequences of shale, siltstone, sandstone, red beds, thin, impure limestone, and thin, nonpersistent coal; red beds are associated with landslides; base is at top of Ames limestone.

Lithology: shale; siltstone; sandstone; clastic; limestone; coal

Wills Creek Formation (Silurian) at surface, covers 0.7 % 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.

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

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

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

Lithology: sandstone; siltstone; conglomerate

Jonestown Volcanic Suite (Ordovician) at surface, covers < 0.1 % of this area

Jonestown Volcanic Suite - Andesite extrusives and dark-greenish-gray metadiabase. Metadiabase weathers medium gray to brown, forming rounded cobbles and boulders.

Lithology: andesite; mafic metavolcanic rock

Cuyahoga Group (Mississippian) at surface, covers 1 % of this area

Cuyahoga Group - Medium-gray siltstone and dark-gray shale containing interbedded light-gray, flaggy sandstone. Includes, in descending order: Meadville Shale, Sharpsville Sandstone, and Orangeville Shale; marine fossils common.

Lithology: siltstone; shale; sandstone

Towamensing Member of Catskill Formation (Devonian) at surface, covers 0.1 % of this area

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

Lithology: sandstone; siltstone; shale

Bellefonte and Axemann Formations, undivided (Ordovician) at surface, covers 0.1 % of this area

Bellefonte and Axemann Formations, undivided - Includes, in descending order, the Bellefonte (Obf) and Axemann (Oa) Formations.

Lithology: dolostone (dolomite); limestone; sandstone

Shenango Formation (Mississippian) at surface, covers 0.9 % of this area

Shenango Formation - Light-gray sandstone and some beds of medium-gray shale and siltstone; upper third of formation is more shaly; contains a few marine fossils.

Lithology: sandstone; shale; siltstone

Limestone of Hamburg sequence (Ordovician) at surface, covers < 0.1 % of this area

Limestone of Hamburg sequence - Conspicuous limestone.

Lithology: limestone

Waynesburg Formation (Permian and Pennsylvanian) at surface, covers 0.8 % of this area

Waynesburg Formation - Cyclic sequences of sandstone, shale, limestone, and coal; commercial coals present; base is at bottom of Waynesburg coal.

Lithology: sandstone; shale; limestone; coal

Bloomsburg and Mifflintown Formations, undivided (Silurian) at surface, covers 0.7 % 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.

Lithology: shale; siltstone; sandstone; limestone; mudstone

Elbrook Formation (Cambrian) at surface, covers 0.2 % of this area

Elbrook Formation - Microcrystalline limestone and, in places, marble; includes subordinate dolomite containing abundant phyllitic layers; occurs in Chester and Montgomery Counties; relation to Elbrook of Cumberland Valley sequence is uncertain.

Lithology: limestone; dolostone (dolomite); phyllite; marble

Montalto Member of Harpers Formation (Cambrian) at surface, covers 0.2 % of this area

Montalto Member of Harpers Formation - Gray quartzite.

Lithology: quartzite

Mafic gneiss (Precambrian) at surface, covers < 0.1 % of this area

Mafic gneiss - Dark, medium grained; includes rocks of probable sedimentary origin; may be equivalent to "PZmgh" in places.

Lithology: mafic gneiss; paragneiss

Huntley Mountain Formation (Mississippian and Devonian) at surface, covers 3 % of this area

Huntley Mountain Formation - 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.

Lithology: sandstone; siltstone; shale

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

Poplar Gap Member of Catskill Formation - Gray and light-olive-gray sandstone, conglomerate, and siltstone containing intermittent red beds; laterally equivalent to Clarks Ferry, Sawmill Run, and Berry Run Members.

Lithology: sandstone; conglomerate; siltstone

Berea Sandstone through Venango Formation, undivided (Devonian) at surface, covers 0.8 % of this area

Berea Sandstone through Venango Formation, undivided - Greenish-yellow and gray sandstone, siltstone, and shale succession, becoming more shaly and more gray downward; bottom of interval is bottom of Panama Conglomerate; Venango not mapped separately because upper key bed (Woodcock Sandstone) is missing. Includes, in descending order: Berea Sandstone, Bedford Shale, Cussewago Sandstone, Riceville Shale, and Venango Formation equivalent; contains marine fossils.

Lithology: shale; siltstone; sandstone; conglomerate

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

Pinesburg Station Formation - Light-colored, thick-bedded, finely laminated dolomite; some limestone.

Lithology: dolostone (dolomite); limestone

Wissahickon Schist (Paleozoic) at surface, covers < 0.1 % of this area

Wissahickon Schist - Dense micaceous schist, gneiss and migmatite.

Lithology: mica schist; gneiss; migmatite

Hershey and Myerstown Formations, undivided (Ordovician) at surface, covers < 0.1 % of this area

Hershey and Myerstown Formations, undivided - In descending order: Hershey--dark-gray to black, thin-bedded, argillaceous limestone; Myerstown--medium- to dark-gray, platy, medium-crystalline limestone; carbonaceous at base.

Lithology: limestone

Passaic Formation Limestone-clast Conglomerate facies (Lower Jurassic and Upper Triassic) at surface, covers < 0.1 % of this area

Passaic Formation Limestone-clast Conglomerate facies - Limestone conglomerate unit (JTrpcl) is medium-bedded to massive, pebble to boulder conglomerate. Clasts are subangular dolomitic limestone in matrix of brownish- to purplish-red sandstone to mudstone; matrix weathers light-gray to white near faults. Maximum thickness unknown.

Lithology: conglomerate; limestone; sandstone; mudstone

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

Hampshire Formation - Interbedded red shale, red mudstone, and red to brown cross-bedded siltstone and sandstone; some thin green shale; greenish-gray sandstone and shale toward top; fragmentary plant fossils; thickness 1,400 to 2,000 feet in west, increases to 3,800 feet in east.

Lithology: shale; sandstone; mudstone; siltstone

Conneaut Group, undivided (Upper Devonian) at surface, covers < 0.1 % of this area

Conneaut Group, undivided - In west: Ellicott and Dexterville Formations-shale, siltstone. In east: Germania Formation-shale, sandstone; Whitesville Formation-shale, sandstone; Hinsdale Sandstone; Wellsville Formation-shale, sandstone; Cuba Sandstone.

Lithology: shale; sandstone; siltstone

Undifferentiated Hamilton Group (Middle Devonian) at surface, covers < 0.1 % of this area

Undifferentiated Hamilton Group - shale, siltstone. In eastern Orange County: Skunnemunk Formation-sandstone, conglomerate; Bellvale Formation-shale, sandstone; Cornwall Shale.

Lithology: shale; siltstone; sandstone; conglomerate

Wills Creek Formation through Mifflintown Formation, undivided (Silurian) at surface, covers < 0.1 % of this area

Wills Creek Formation through Mifflintown Formation, undivided - Includes, in descending order, the Wills Creek Formation (Swc) and Bloomsburg and Mifflintown Formations, undivided (Sbm).

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

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

Scherr Formation - Chiefly siltstone; some fine-grained sandstone, shale, and mudstone; light olive gray; marine fossils.

Lithology: siltstone; sandstone; shale; mudstone

Allegheny Formation and Pottsville Formation (Pennsylvanian) at surface, covers < 0.1 % of this area

Allegheny Formation - Interbedded sandstone, siltstone, claystone, shale, and coal beds; Upper Freeport coal at top; where present, Brookville coal defines base; thickness 275 feet in northeast, increases to 325 feet in south and west. And Pottsville Formation - Interbedded sandstone, siltstone, claystone, shale, and coal beds; conglomeratic orthoquartzite and protoquartzite at base; thickness 60 feet in northeast, increases to 440 feet in southwest

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

Pocono Formation (Mississippian) at surface, covers 0.8 % 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

Oswayo and Venango Formations (Upper Devonian) at surface, covers < 0.1 % of this area

Oswayo and Venango Formations - shale, siltstone, sandstone; replaced eastwardly by Cattaraugus Formation-shale, sandstone, conglomerate.

Lithology: shale; siltstone; sandstone; conglomerate

Beekmantown Group (Ordovician) at surface, covers < 0.1 % of this area

Beekmantown Group - Includes, in descending order, the Pinesburg Station (Ops), Rockdale Run (Orr), and Stonehenge (Os) Formations.

Lithology: limestone; dolostone (dolomite); chert

Chickies Formation (Cambrian) at surface, covers 0.2 % of this area

Chickies Formation - Light-gray, hard, massive, Scolithus-bearing quartzite and quartz schist; thin, interbedded dark slate at top; conglomerate (Hellam Member) at base.

Lithology: quartzite; schist; slate; conglomerate

Shadygrove Formation (Cambrian) at surface, covers < 0.1 % of this area

Shadygrove Formation - Pure, light-colored limestone, stromatolitic in part; abundant pinkish limestone and cream-colored chert.

Lithology: limestone; chert

Peach Bottom Slate and Cardiff Conglomerate, undivided (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Peach Bottom Slate and Cardiff Conglomerate, undivided - Bluish-black slate (Peach Bottom); quartz conglomerate having a matrix of sericite and chlorite (Cardiff).

Lithology: slate; conglomerate

Monongahela Group (Pennsylvanian) at surface, covers < 0.1 % of this area

Monongahela Group - non-marine cyclic sequences of sandstone, siltstone, red and gray shale, limestone, and coal. Contains the Uniontown and Pittsburgh Formations. Extends from the top of the Waynesburg coal to the base of the Pittsburgh coal. Includes the Waynesburg, Uniontown, Sewickley, Redstone and Pittsburgh coals. Thickness is 170 feet in Mineral and Grant Counties.

Lithology: sandstone; siltstone; shale; limestone; coal

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

Long Run and Walcksville Members of Catskill Formation, undivided - Includes, in descending order, the Long Run (Dclr) and Walcksville (Dcw) Members of the Catskill Formation, which are described separately below.

Lithology: sandstone; siltstone; mudstone

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

Stonehenge Formation - Stromatolitic, fine-grained limestone; includes coarser grained and conglomeratic, siliceous, laminated Stoufferstown Formation at base in most of Cumberland Valley.

Lithology: limestone

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

Annville Formation - Light-gray, massive, high-calcium limestone; mottled at base.

Lithology: limestone

New Oxford Formation (Triassic) at surface, covers 0.4 % of this area

New Oxford Formation - Light-gray to buff, commonly arkosic sandstone interbedded with red shale, mudstone, and fine-grained sandstone

Lithology: arkose; shale; mudstone; sandstone

Quartz-Oligoclase Gneiss (Middle Proterozoic) at surface, covers < 0.1 % of this area

Quartz-Oligoclase Gneiss - White-weathering, light-greenish-gray, medium- to coarse-grained, moderately layered to indistinctly foliated gneiss and lesser amounts of granofels composed of quartz, oligoclase or andesine, and, locally, biotite, hornblende and (or) clinopyroxene. Contains thin amphibolite layers.

Lithology: gneiss; granofels; amphibolite

Hammer Creek Formation (Triassic) at surface, covers 0.3 % of this area

Hammer Creek Formation - Gray and pale red, fine- to coarse-grained quartzose sandstone, siltstone, and mudstone.

Lithology: sandstone; siltstone; mudstone

Lockatong Formation (Triassic) at surface, covers 0.3 % of this area

Lockatong Formation - Dark-gray to black, thick-bedded argillite containing a few zones of thin-bedded black shale; locally has thin layers of impure limestone and calcareous shale.

Lithology: argillite; shale; limestone; black shale

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

Chadakoin Formation - Light-gray or brownish siltstone and some sandstone, interbedded with medium-gray shale; included in Conneaut Group and "Chemung" of earlier workers; marine fossils common; includes "pink rock" of drillers.

Lithology: siltstone; shale; sandstone

Sherman Creek Member of Catskill Formation (Devonian) at surface, covers 0.6 % 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

Pensauken and Bridgeton Formations, undifferentiated (Tertiary) at surface, covers 0.2 % of this area

Pensauken and Bridgeton Formations, undifferentiated - Dark-reddish-brown, cross-stratified, feldspathic quartz sand and some thin beds of fine gravel and rare layers of clay or silt.

Lithology: sand; gravel; clay or mud; silt

Snitz Creek and Buffalo Springs Formations, undivided (Cambrian) at surface, covers < 0.1 % of this area

Snitz Creek and Buffalo Springs Formations, undivided - Includes, in descending order, the Snitz Creek (CAsc) and Buffalo Springs (CAbs) Formations. Snitz Creek Formation - thick-bedded. medium- to coarsely crystalline dolomite; in part oolitic, containing laminated limestone and sandstone interbeds. Buffalo Springs Formation - light-gray to pinkish-gray, finely to coarsely crystalline limestone and interbedded dolomite; numerous siliceous and clayey laminae; stromatolitic limestone beds near top; some thin sandy beds.

Lithology: limestone; dolostone (dolomite); sandstone

Buddys Run Member of Catskill Formation (Devonian) at surface, covers 0.2 % 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

Brunswick Formation (Triassic) at surface, covers 1 % of this area

Brunswick Formation - Reddish-brown mudstone, siltstone, and shale, containing a few green and brown shale interbeds; red and dark-gray, interbedded argillites near base. Youngest beds in Brunswick may be Jurassic in age.

Lithology: mudstone; siltstone; shale; argillite

Brallier and Harrell Formations, undivided (Devonian) at surface, covers 0.6 % of this area

Brallier and Harrell Formations, undivided - In descending order: Brallier--medium-gray, planar-bedded siltstone interbedded with light-olive shale; sparse marine fauna; Harrell--black shale (Burket Member) and dark-gray shale.

Lithology: siltstone; shale; black shale

Beekmantown Group, Lower Part (Lower Ordovician) at surface, covers < 0.1 % of this area

Beekmantown Group, Lower Part (Clarke and Schuchert, 1899) - Very thin to thick-bedded, interbedded dolomite and minor limestone. Upper beds are light-olive-gray to dark-gray, fine- to medium-grained, thin- to thick-bedded dolomite. Middle part is olivegray-, light-brown-, or dark-yellowish-orange- weathering, dark-gray, aphanitic to fine-grained, laminated to medium-bedded dolomite and light-gray to light-bluish-gray-weathering, medium-dark- to dark-gray, fine-grained, thin- to medium-bedded limestone, that is characterized by mottling with reticulate dolomite and light-olive-gray to grayish-orange, dolomitic shale laminae surrounding limestone lenses. Limestone grades laterally and down section into medium- gray, fine-grained dolomite. Lower beds consist of medium-light- to dark-gray, aphanitic to coarse-grained, laminated to medium-bedded, locally slightly fetid dolomite having thin black chert beds, quartz-sand laminae, and oolites. Lenses of light-gray, very coarse to coarse-grained dolomite and floating quartz sand grains and quartz-sand stringers at base of sequence. Lower contact placed at top of distinctive medium-gray quartzite. Contains conodonts of Cordylodus proavus to Rossodus manitouensis zones of North American Midcontinent province as used by Sweet and Bergstrom (1986). Unit Obl forms Stonehenge Formation of Drake and Lyttle (1985) and Drake and others (1985), upper and middle beds are included in Epler Formation, and lower beds are in Rickenbach Dolomite of Markewicz and Dalton (1977). Unit is about 183 m (600 ft) thick.

Lithology: dolostone (dolomite); limestone; chert

Sams Creek Metabasalt (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Sams Creek Metabasalt - Altered basaltic flows, some amygdaloidal; green, schistose, containing hornblende, epidote, chlorite, and quartz.

Lithology: meta-basalt

Bryn Mawr Formation (Tertiary) at surface, covers < 0.1 % of this area

Bryn Mawr Formation - High-level terrace deposits; reddish-brown gravelly sand and some silt. Age uncertain.

Lithology: gravel; sand; silt

Port Ewen Shale (Lower Devonian) at surface, covers < 0.1 % of this area

Port Ewen Shale (Clarke, 1903) - Upper part is medium-gray- weathering, dark-to- medium-dark-gray, thin- to medium-bedded, fossiliferous, calcareous siltstone and shale. Lower part is medium-dark-gray, irregularly bedded nonfossiliferous, calcareous silty shale. Lower contact abrupt and placed at top of uppermost medium-gray, argillaceous limestone in Minisink Limestone. Thickness approximately 46 m (150 ft).

Lithology: shale; siltstone

Berea Sandstone and Bedford Shale, Undivided (Devonian) at surface, covers < 0.1 % of this area

Berea Sandstone and Bedford Shale, Undivided - Sandstone and shale; upper portion sandstone; brown, weathers light brown to reddish brown; thin to thick bedded, planar to lenticular bedding; minor shale interbeds; 5 to 75 feet thick, locally 100 to 125 feet thickness in Lorain, Cuyahoga, and Medina Counties; lower portion shale; gray to brown, locally reddish brown; thin to medium bedded, planar to lenticular bedding; interbedded siltstone and sandstone, ripple marks in siltstone beds; 80 to 180 feet thick, locally thin to absent where Berea Sandstone is thick.

Lithology: sandstone; shale; siltstone

Microperthite Alaskite (Middle Proterozoic) at surface, covers < 0.1 % of this area

Microperthite Alaskite - Pink- to buff-weathering, light-pinkish-gray or pinkish-white, medium- to coarse-grained, gneissoid to indistinctly foliated granite composed principally of microcline microperthite, quartz and oligoclase. Includes small bodies of amphibolite not shown on map.

Lithology: granite; amphibolite

Cardiff Metaconglomerate (Late Precambrian (?)) at surface, covers < 0.1 % of this area

Cardiff Metaconglomerate - Silvery-gray, well foliated, micaceous quartz-pebble metaconglomerate and quartzite; apparent maximum thickness 700 feet.

Lithology: meta-conglomerate; quartzite

Metadiabase (Precambrian) at surface, covers < 0.1 % of this area

Metadiabase - Dark-gray, fine-grained intrusives; locally, mineralogy is altered and unit has greenish color.

Lithology: mafic metavolcanic rock

Kinzers Formation (Cambrian) at surface, covers < 0.1 % of this area

Kinzers Formation - Base--dark-brown shale; middle--gray and white spotted limestone and, locally, marble having irregular partings; top--sandy limestone which weathers to a fine-grained, friable, porous, sandy mass.

Lithology: limestone; marble; shale; sand

Quaternary Alluvium (Quaternary) at surface, covers < 0.1 % of this area

Quaternary Alluvium - alluvial deposits of sand, gravel, silt, and clay.

Lithology: alluvium

Waynesboro Formation (Cambrian) at surface, covers < 0.1 % of this area

Waynesboro Formation - Greenish-gray and grayish-purple shale interbedded with greenish-gray sandstone and conglomerate; occurs in Henrietta fault block only.

Lithology: shale; sandstone; conglomerate

Rockwell Formation (Mississippian and Devonian) at surface, covers 0.2 % of this area

Rockwell Formation - Buff, fine- to medium-grained, crossbedded, argillaceous sandstone and dark-gray shale; includes some carbonaceous shale, sporadic conglomerate beds, and diamictite; included in lower "Pocono" of earlier workers.

Lithology: sandstone; shale; conglomerate

Conestoga Formation (Ordovician and Cambrian) at surface, covers 0.4 % of this area

Conestoga Formation - Light-gray, thin-bedded, impure, contorted limestone having shale partings; conglomeratic at base; in Chester Valley, includes micaceous limestone in upper part, phyllite in middle, and alternating dolomite and limestone in lower part.

Lithology: limestone; phyllite; conglomerate; dolostone (dolomite); shale

Berry Run and Sawmill Run Members of Catskill Formation, undivided (Devonian) at surface, covers < 0.1 % 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

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

Upper Walton Formation - shale, sandstone, conglomerate.

Lithology: shale; sandstone; conglomerate

Stockton Formation (Triassic) at surface, covers 0.5 % of this area

Stockton Formation - Light-gray to buff, coarse-grained, arkosic sandstone; includes reddish-brown to grayish-purple sandstone, siltstone, and mudstone.

Lithology: arkose; siltstone; sandstone; mudstone

Walcksville Member of Catskill Formation (Devonian) at surface, covers 0.1 % of this area

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

Lithology: sandstone; siltstone; mudstone

Chilhowee Group; Antietam Formation (Cambrian) at surface, covers < 0.1 % of this area

Antietam Formation - White to dark gray and brown, thick-bedded, fine- to coarse-grained quartzite with thin argillaceous partings; first occurrence of Lower Cambrian fossils; cleavage generally obscures bedding; increasingly metamorphosed and phyllitic toward east; estimated thickness 300 to 800 feet.

Lithology: quartzite; phyllite

Nittany and Stonehenge/Larke Formations, undivided (Ordovician) at surface, covers 0.1 % of this area

Nittany and Stonehenge/Larke Formations, undivided - Includes, in descending order, the Nittany (On) and Stonehenge/Larke (Osl) Formations.

Lithology: dolostone (dolomite); limestone; chert; conglomerate

Octoraro Formation (Probably lower Paleozoic) at surface, covers 0.9 % of this area

Octoraro Formation - Includes albite-chlorite schist, phyllite, some hornblende gneiss, and granitized members.

Lithology: schist; phyllite; gneiss; granitoid

Felsic and intermediate gneiss (Precambrian) at surface, covers 0.2 % of this area

Felsic and intermediate gneiss - Light, medium grained; includes rocks of probable sedimentary origin.

Lithology: felsic gneiss; mafic gneiss; paragneiss

Bushkill Member (Middle Ordovician) at surface, covers < 0.1 % of this area

Bushkill Member (Drake and Epstein, 1967) - Interbedded medium- to dark gray, thinly laminated to thick-bedded shale and slate and less abundant medium-gray to brownish-gray, laminated to thin-bedded siltstone. To the southwest, fine-grained, thin dolomite lenses occur near base. Complete turbidite sequences (Bouma, 1962) occur locally, but basal cutout sequences (Tbcde, Tcde or Tde) dominate. Conformable lower contact is placed at top of highest shaly limestone; elsewhere, lower contact is commonly strain slipped. Correlates with graptolite Climacograptus bicornis to Corynoides americanus zones of Riva (1969, 1974) (Parris and Cruikshank, 1992). Thickness ranges from 1,250 m (4,100 ft) in Delaware River Valley to 457 m (1,500 ft) at New York State line.

Lithology: slate; shale; siltstone; dolostone (dolomite)

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

Machias Formation - shale, siltstone; Rushford Sandstone; Caneadea, Canisteo, and Hume Shales; Canaseraga Sandstone; South Wales and Dunkirk Shales.

Lithology: shale; siltstone; sandstone

Felsic gneiss (Precambrian) at surface, covers 0.2 % of this area

Felsic gneiss - Light, medium grained; includes rocks of probable sedimentary origin.

Lithology: felsic gneiss; paragneiss

"Glenarm Wissahickon" formation (Probably lower Paleozoic) at surface, covers 0.4 % of this area

"Glenarm Wissahickon" formation - Lithologically similar to oligoclase-mica schist of the Wissahickon Formation (PZw), but also includes lenticular amphibolite bodies having ocean-floor basalt chemistry.

Lithology: mica schist; mafic gneiss; amphibolite;

Patapsco(?) Formation (Cretaceous) at surface, covers < 0.1 % of this area

Patapsco(?) Formation - Intensely colored, variegated, ferruginous clay and, in places, beds of sand; occurs in isolated patches.

Lithology: clay or mud; sand

Hornblende gneiss (Precambrian) at surface, covers < 0.1 % of this area

Hornblende gneiss - Dark, medium grained; includes some rocks of probable sedimentary origin.

Lithology: mafic gneiss; paragneiss

Diabase Sills and Dikes (Triassic) at surface, covers < 0.1 % of this area

Diabase Dikes and Sills - Sills: Greenish-gray to black, medium-grained; dikes: Greenish-gray to black, medium- to dine-grained; local contact metamorphic aureoles.

Lithology: diabase

Epler Formation (Ordovician) at surface, covers 0.3 % of this area

Epler Formation - Very finely crystalline, light-gray limestone interbedded with gray dolomite; coarsely crystalline limestone lenses present.

Lithology: limestone; dolostone (dolomite)

Allegheny Formation (Pennsylvanian) at surface, covers < 0.1 % of this area

Allegheny Formation - cyclic sequences of sandstone, siltstone, shale, limestone, and coal. Includes the Freeport, Kittanning and Clarion coals, also, the Princess coals of Kentucky . Extends from the top of the Upper Freeport coal to the top of the Homewood Sandstone.

Lithology: sandstone; siltstone; shale; limestone; coal

Marcellus Formation (Devonian) at surface, covers 0.1 % 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

Coeymans Formation, Kalkberg Limestone, Coeymans Limestone, Manlius Limestone, undivided (Lower Devonian) at surface, covers < 0.1 % of this area

Coeymans Formation, Kalkberg Limestone, Coeymans Limestone, Manlius Limestone, undivided - At New York border consists of fine-grained, chert-bearing, argillaceous limestone (Kalkberg Limestone) grading downward through coarse-grained limestone (Coeymans Limestone) into fine-grained limestone (Manlius Limestone). Toward southwest these units grade into fine- to coarse-grained limestone with a marked increase in quartz sand that comprises the Coeymans Formation (Epstein and others, 1967). Total thickness 27 m (90 ft). Coeymans Formation (Epstein and others, 1967) - Medium-light-gray, fine- to coarse-grained calcareous sandstone and medium-gray, fine- to coarse-grained, medium- to thick-bedded, locally irregularly-bedded, argillaceous to arenaceous limestone containing lenses of quartz sand and nodules of black chert. Grades downward into medium-gray, fine-grained, argillaceous and arenaceous limestone containing local beds of fine- to coarse-grained pebbly calcareous sandstone. Local bioherms consisting of light-gray to light-pinkish-gray, coarse-grained to very coarse biogenic limestone are unbedded and have sharp boundaries. Lower contact of unit abrupt. Formation thickness varies from 11 m (35 ft) in northeast to 24 m (80 ft) in southwest. Kalkberg Limestone (Chadwick, 1908) - Medium-gray-weathering, medium-dark-gray, fine-grained, very thin to massively bedded fossiliferous limestone. Grades downward into fine- to medium-grained, thin-bedded, fossiliferous argillaceous limestone containing nodules and lenses of dark-gray chert. Grades to the southwest into calcareous and arenaceous rocks of the upper part of the Coeymans Formation near Wallpack Center. Lower contact placed at base of lowest black chert. Approximately 12 m (40 ft) thick. Coeymans Limestone (Clarke and Schuchert, 1899) - Medium-gray weathering, medium-dark-gray, fine-to-coarse-grained, medium- to massively bedded fossiliferous limestone and local argillaceous limestone lenses. Unit is approximately 9 m (30 ft) thick. Between Duttonville and Millville, grades into biohermal and nonbiohermal facies of medium- to coarse-grained limestone of Coeymans Formation of Epstein and others (1967). Manlius Limestone (Vanuxem, 1840) - Medium-gray weathering, medium-dark- to dark-gray, very fine to fine-grained, unevenly bedded fossiliferous limestone. Some local medium-grained limestone, yellowish-gray shale partings and biostromes. Near Hainesville, unit grades into lower part of Coeymans Formation. Lower contact abrupt and placed at top of uppermost very fine grained argillaceous limestone. Thickness approximately 11 m (35 ft).

Lithology: limestone; sandstone; chert

Schoharie Formation (Lower Devonian) at surface, covers < 0.1 % of this area

Schoharie Formation (Vanuxem, 1840) - Yellowish-gray- to locally pale-olive-weathering, medium- to dark-gray, medium- to thick-bedded, calcaeous siltstone and lesser amounts of silty limestone. Locally contains thin ribs or pods of black chert in limestone. Limestone content decreases in lower part of unit. Contains the trace fossil Taonurus, a grazing trail. Lower contact gradational and placed at top of highest massive siltstone below lowest limestone. Thickness approximately 53 m (175 ft).

Lithology: siltstone; limestone; chert

Limestone fanglomerate (Triassic) at surface, covers < 0.1 % of this area

Limestone fanglomerate - Yellowish-gray to medium-gray, angular limestone and dolomite pebbles, cobbles, and fragments set in a red, very fine grained quartz matrix; a few shale-clast interbeds.

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

Corry Sandstone through Riceville Formation, undivided (Devonian) at surface, covers 0.8 % of this area

Corry Sandstone through Riceville Formation, undivided - Same as Berea-through-Riceville (MDbr) interval, but uppermost sandstone unit is recognized as Corry, not Berea.

Lithology: sandstone; shale; siltstone

New Oxford Formation, basal quartz conglomerate (Triassic) at surface, covers < 0.1 % of this area

New Oxford Formation - basal conglomerate member: From vicinity of Maryland Rte. 73 northward, quartz conglomerate with red sandy matrix

Lithology: conglomerate

Quartz fanglomerate (Triassic) at surface, covers < 0.1 % of this area

Quartz fanglomerate - Well-rounded quartzite pebbles, cobbles, and rare boulders set in a reddish-brown, sandy matrix.

Lithology: conglomerate; quartzite; sand

Lower members of Gatesburg Formation, undivided (Cambrian) at surface, covers 0.1 % of this area

Lower members of Gatesburg Formation, undivided - Includes, in descending order: cyclic repetitions of sandstone and dolomite ("upper sandstone'' member); fossiliferous, laminated to massive limestone and dolomite (Ore Hill Member); cyclic repetitions of sandstone and dolomite (''lower sandstone" member); and thick-bedded crystalline dolomite (Stacy Member).

Lithology: dolostone (dolomite); sandstone; limestone

Trenton Gravel (Quaternary) at surface, covers 0.2 % of this area

Trenton Gravel - Gray or pale-reddish-brown, very gravelly sand interstratified with crossbedded sand and clay-silt beds; includes areas of Holocene alluvium and swamp deposits.

Lithology: sand; clay or mud; silt; gravel; alluvium

Gatesburg Formation (Cambrian) at surface, covers 0.1 % of this area

Gatesburg Formation - Gray dolomite, limestone, and sandstone. Includes the Mines Member (CAgm) and four lower members (CAgl).

Lithology: dolostone (dolomite); limestone; sandstone; chert

Albite-Oligoclase Granite (Middle Proterozoic) at surface, covers < 0.1 % of this area

Albite-Oligoclase Granite - White-weathering, light-greenish-gray, medium- to coarse-grained granite composed of albite or oligoclase, quartz, and sparse amounts of hornblende or clinopyroxene. Petrogenetically related to quartz-oligoclase gneiss (Ylo) but Yla has a more granulitic texture. Includes small bodies of pegmatite not shown on map.

Lithology: granite; pegmatite

Mahantango Formation (Devonian) at surface, covers 0.3 % 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 0.2 % of this area

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

Lithology: siltstone; shale; sandstone

Gettysburg Formation (Triassic) at surface, covers 0.7 % of this area

Gettysburg Formation - Reddish-brown to maroon, silty mudstone and shale containing thin red sandstone interbeds; several thin beds of impure limestone.

Lithology: mudstone; silt; shale; sandstone; limestone

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

Ontelaunee Formation - Light- to dark-gray, very finely to medium-crystalline dolomite containing interbeds of light-gray limestone; interbedded nodular, dark-gray chert at base.

Lithology: dolostone (dolomite); limestone; chert

Zooks Corner Formation (Cambrian) at surface, covers < 0.1 % of this area

Zooks Corner Formation - Medium-gray, finely crystalline dolomite; silty to sandy, containing numerous siliceous to argillaceous laminae.

Lithology: dolostone (dolomite)

Richland Formation (Cambrian) at surface, covers < 0.1 % of this area

Richland Formation - Gray dolomite, in part oolitic, interbedded with medium-gray limestone and dark-gray oolitic chert.

Lithology: dolostone (dolomite); limestone; chert

Ridgeley Member of Old Port Formation (Devonian) at surface, covers < 0.1 % of this area

Ridgeley Member of Old Port Formation - Fine- to very coarse grained, light-gray sandstone ("Oriskany" of earlier workers).

Lithology: sandstone

Ohio Shale (Devonian) at surface, covers < 0.1 % of this area

Ohio Shale - Shale; brownish black to greenish gray, weathers brown; carbonaceous to clayey, laminated to thin bedded, fissile parting; carbonate and/or siderite concretions in lowermost 50 feet; petroliferous odor; 250 to 500+ feet thick. Includes Olentangy Shale south of central Delaware Co.

Lithology: black shale; shale

Marburg Schist (Probably lower Paleozoic) at surface, covers 0.2 % of this area

Marburg Schist - Gray-green phyllite, mica-chlorite schist, and conglomerate.

Lithology: phyllite; mica schist; conglomerate

Hornblende Granite (Middle Proterozoic) at surface, covers < 0.1 % of this area

Hornblende Granite - Pinkish-gray- to medium-buff-weathering, pinkish-white or light-pinkish-gray, medium- to coarse-grained, gneissoid to indistinctly foliated granite and sparse granite gneiss composed principally of microcline microperthite, quartz, oligoclase, and hornblende. Some phases are quartz syenite or quartz monzonite. Includes small bodies of pegmatite and amphibolite not shown on map. U-Pb age approximately 1,090 Ma (Drake and others, 1991b).

Lithology: granite; paragneiss; quartz syenite; quartz monzonite; pegmatite; amphibolite

Catoctin Metabasalt (Late Precambrian) at surface, covers < 0.1 % of this area

Catoctin Metabasalt - Thick-bedded metabasalt with amygdaloidal layers and secondary veins of quartz, calcite, and epidote; interbedded green tuffaceous phyllite and blue amygdaloidal metaandesite.

Lithology: meta-basalt; phyllite

Poxono Island Formation (Upper Silurian) at surface, covers < 0.1 % of this area

Poxono Island Formation (White, 1882) - Greenish-gray, finely crystalline to aphanitic, thin- to medium-bedded, flaggy dolomite containing discontinuous lenses of disseminated, rounded quartz grains. Some local quartz sandstone beds and argillaceous dolomite. Lower contact gradational (Epstein, 1973). Formation poorly exposed; located by drill data. Thickness estimated at 183 m (600 ft) from well data.

Lithology: dolostone (dolomite); sandstone

Franklin Marble (Precambrian) at surface, covers < 0.1 % of this area

Franklin Marble - White, coarsely crystalline; disseminated graphite flakes.

Lithology: marble

Wakefield Marble (Late Precambrian (?)) at surface, covers < 0.1 % of this area

Wakefield Marble - White, fine-grained marble; subordinate white, green, and pink variegated marble; and blue marble.

Lithology: marble

Poplar Gap and Packerton Members of Catskill Formation, undivided (Devonian) at surface, covers 0.6 % of this area

Poplar Gap and Packerton Members of Catskill Formation, undivided - Includes, in descending order, the Poplar Gap (Dcpg) and Packerton (Dcp) Members of the Catskill Formation.

Lithology: sandstone; conglomerate; siltstone

Antietam Formation (Cambrian) at surface, covers < 0.1 % of this area

Antietam Formation - Gray, buff-weathering quartzite and quartz schist.

Lithology: quartzite; schist

Graphitic felsic gneiss (Precambrian) at surface, covers < 0.1 % of this area

Graphitic felsic gneiss - Includes Pickering Gneiss and small areas of marble; dominantly quartz and feldspar with varying amounts of graphite and various metamorphic minerals; medium grained, light to dark gray and greenish gray; sedimentary origin.

Lithology: gneiss; marble; paragneiss

Stockton Formation (Upper Triassic) at surface, covers < 0.1 % of this area

Stockton Formation - Predominantly medium- to coarse-grained, light-gray, light-grayish-brown, or yellowish- to pinkish-gray arkosic sandstone and medium- to fine-grained, violet-gray to reddish-brown arkosic sandstone; with lesser, reddish to purplish-brown, silty mudstone, argillaceous siltstone, and shale. Some coarse-grained sandstone in lower part contains thick beds of conglomerate (Trsc) which have been mapped in the vicinity of Stockton. Sandstone, deposited in high-gradient stream channels, is mostly planar bedded with scoured bases containing pebble lags and mudstone rip-up clasts. Upper part of channel beds are burrowed. Large-scale trough crossbeds occur in some very coarse grained sandstone beds; smaller scale trough and climbing-ripple cross lamination occur in the upper part of channel sequences and in finer grained sandstone beds. Typical floodplain mudstones are irregularly thin bedded and extensively burrowed. Floodplain beds are thicker and more numerous in the central Newark basin, near the Delaware River. Thickness of the unit (including Trsc) near Stockton is about 1,240 m (4,068 ft).

Lithology: arkose; fine-grained mixed clastic; siltstone; shale

Potomac Formation (Upper Cretaceous, lower Cenomanian) at surface, covers < 0.1 % of this area

Potomac Formation - Predominantly clay to clay-silt, thinly laminated to thick-bedded, mottled red, white, and orange-brown, less commonly dark-gray and woody; interbedded with thin beds and lenses of very fine to medium-grained, massive, white to orange-brown, micaceous sand. Lithologies are typical of the shallow subsurface. Down dip, these lithologies interfinger with thin to thick beds of marine clay-silt, commonly glauconitic and locally shelly. Marine beds are most prevalent in the southernmost part of the southern sheet. Unit 3 was cored in its entirety at Freehold where it is approximately 75 m (246 ft) thick. In the core, the basal 6 m (20 ft) consists of red or mottled red and white clay interbedded with gravel and fine- to coarse-grained sand. The clay is pervaded by reddish-brown siderite. Most of the overlying beds consist of interbedded dark-colored clay, locally weathered to pale yellow or white, and fine- to medium-grained, light-colored sand. Layers that contain fine black carbonaceous material to large lignitized wood pieces are common in unit 3 in this core. At Toms River, the unit is about 60 m (197 ft) thick and consists of dark- to pale-gray clay, locally weathering to white or yellowish gray, and light-colored, micaceous sand. In general, the darker colored clay is more common in the upper part of the section. Locally, the sand has very small amounts of glauconite which may indicate some local marine influence during sedimentation. The age of unit 3 was determined from pollen in the nonmarine deposits and foraminifera in the marine sections. Typical forms found in Zone III in New Jersey are Ajatipollis sp. A, Tricolpites nemejci, T. vulgaris, Tricolporoidites bohemicus, Tricolporoidites sp. A, T. sp. B, and Tricolporopollenites sp. B (Doyle and Robbins, 1977). In the marine facies, Petters (1976) reports a planktic foraminiferal suite containing Praeglobotruncana delrioensis and Rotalipora greenhornensis. Both the pollen and foraminiferal assemblages suggest an early Cenomanian age.

Lithology: clay or mud; silt; sand

Buttermilk Falls Limestone through Esopus Formation, undivided (Devonian) at surface, covers < 0.1 % of this area

Buttermilk Falls Limestone through Esopus Formation, undivided - In descending order: Buttermilk Falls Limestone--gray fossiliferous limestone and black chert; Palmerton Sandstone--massive white siliceous sandstone; Schoharie Formation--gray calcareous, argillaceous siltstone; Esopus Formation--gray silty shale and sandy siltstone.

Lithology: limestone; siltstone; sandstone; shale; chert

Ridgeley Formation through Coeymans Formation, undivided (Devonian) at surface, covers < 0.1 % of this area

Ridgeley Formation through Coeymans Formation, undivided - In descending order: Ridgeley Formation--white siliceous sandstone; Shriver Chert--gray siltstone and shale and dark-gray chert; Port Ewen Shale--dark-gray calcareous siltstone and shale; Minisink Limestone--dark-gray clayey limestone; New Scotland Formation--dark-gray fossiliferous shale and clayey limestone; Coeymans Formation--gray, clayey to sandy limestone.

Lithology: sandstone; siltstone; shale; limestone; chert

Graywacke and shale of Martinsburg Formation (Ordovician) at surface, covers 0.3 % of this area

Graywacke and shale of Martinsburg Formation - Abundant impure sandstone (graywacke) interbeds.

Lithology: graywacke

"Chemung" Formation, Parkhead Sandstone, Brallier Formation, and Harrell Shale (Devonian) at surface, covers < 0.1 % of this area

"Chemung" Formation - Predominantly marine beds characterized by gray to olive-green graywacke, siltstone, and shale; thickened ranges from 2,000 to 3,000 feet; Parkhead Sandstone - Gray to olive-green sandy shale, conglomeratic sandstone and graywacke; present in Washington County, identification uncertain in west; thickness averages 400 feet; Brallier Fomation - (Woodmont Shale of earlier reports). Medium to dark gray, laminated shale and siltstone; weathers to light olive-gray; grain size coarsens upward; thickness about 2,000 feet in west, about 1,7000 feet in east; and Harrell Shale - Dark gray laminated shale; absent in east where Brallier lies directly on Mahantango, Tully Limestone lies near base in west, in subsurface of Garrett County; total thickness in west 140 to 300 feet.

Lithology: shale; siltstone; sandstone; graywacke; limestone

Greenbrier Formation (Mississippian) at surface, covers < 0.1 % of this area

Greenbrier Formation - Upper part red calcareous shale and sandstone interbedded with greenish-gray and reddish-gray argillaceous limestone; Loyalhanna Limestone Member: Gray to red, cross-bedded, arenaceous calcarenite; total thickness 200 to 300 feet.

Lithology: limestone; sandstone; shale; calcarenite

Allentown Dolomite (Lower Ordovician and Upper Cambrian) (Wherry, 1909) (Lower Ordovician and Upper Cambrian) at surface, covers < 0.1 % of this area

Allentown Dolomite (Lowest Lower Ordovician and Upper Cambrian) (Wherry, 1909) - Medium- to very light gray, fine- to medium-grained, very thin to very thick bedded dolomite containing minor orthoquartzite and shale. Oolites and algal stromatolites occur throughout unit. Shaly dolomite increases downward towards lower conformable contact with the Leithsville Formation. Unit does not crop out but is known from subsurface borings near Flanders (Volkert and others, 1990). Thickness ranges from 0 to 73 m (0-240 ft) due to erosion.

Lithology: dolostone (dolomite); orthoquartzite; shale

Snitz Creek Formation (Cambrian) at surface, covers < 0.1 % of this area

Snitz Creek Formation - Thick-bedded, medium- to coarsely crystalline dolomite, in part oolitic, containing laminated limestone and sandstone interbeds.

Lithology: dolostone (dolomite); limestone; sandstone

Ramseyburg Member (Upper and Middle Ordovician) at surface, covers < 0.1 % of this area

Ramseyburg Member (Drake and Epstein, 1967) - Interbedded medium- to dark-gray, to brownish-gray, fine- to medium-grained, thin- to thick-bedded graywacke sandstone and siltstone and medium- to dark-gray, laminated to thin-bedded shale and slate. Unit may form complete turbidite sequences, Tabcde (Bouma, 1962), but basal cutout sequences Tcde dominate. Basal scour, sole marks, and soft-sediment distortion of beds are common in graywacke. Thermally metamorphosed near intrusive bodies. Lower contact placed at bottom of lowest thick- to very thick bedded graywacke, but contact locally grades through sequence of dominantly thin-bedded shale and slate and minor thin- to medium-bedded discontinuous and lenticular graywacke beds in the Bushkill member. Parris and Cruikshank (1992) correlate unit with Orthograptus ruedemanni to lowest part of Climacograptus spiniferus zones of Riva (1969, 1974). Thickness ranges from 640 m (2,100 ft) in Delaware River Valley, to 1,524 m (5,000 ft) near Stillwater, to 1067 m (3,500 ft) at New York State line.

Lithology: graywacke; siltstone; shale; slate

Peters Creek Schist (Probably lower Paleozoic) at surface, covers 0.4 % of this area

Peters Creek Schist - Chlorite-sericite schist containing interbedded quartzite.

Lithology: schist; quartzite

Leithsville Formation (Cambrian) at surface, covers 0.1 % of this area

Leithsville Formation - Medium- to dark-gray, crystalline dolomite, light-olive-gray in places, weathering to light gray and yellowish brown; massive bedded; oolitic; pink to gray, mottled chert and dark-gray chert; thin shale and dolomitic shale interbeds; scattered sand grains; upper part is very shaly.

Lithology: dolostone (dolomite); shale; chert; sand

Peach Bottom Slate (Ordovician (?)) at surface, covers < 0.1 % of this area

Peach Bottom Slate - Hard, bluish-black graphitic slate; thin beds of fine-grained black quartzite near base; apparent maximum thickness 1,000 feet.

Lithology: slate; quartzite

Graphitic felsic gneiss (Precambrian) at surface, covers < 0.1 % of this area

Graphitic felsic gneiss - Medium grained, medium to dark gray; locally gneissic, predominantly feldspar and quartz, plus dark accessories and various alteration minerals.

Lithology: felsic gneiss; mafic gneiss

Metagabbro (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Metagabbro - Ranges from fine- to medium-grained, altered gabbro to hornblende gneiss.

Lithology: mafic gneiss; gabbro

Pegmatite (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Pegmatite - Coarse to medium grained, granitic; contacts range from sharp to narrowly gradational; some zoning in places.

Lithology: pegmatite

Hypersthene-Quartz-Oligoclase Gneiss (Middle Proterozoic) at surface, covers < 0.1 % of this area

Hypersthene-Quartz-Oligoclase Gneiss - Gray- to tan-weathering, greenish-gray to greenish-brown, medium-grained, moderately well layered and foliated, greasy-lustered gneiss of charnockitic affinity composed of andesine or oligoclase, quartz, clinopyroxene, hornblende, hypersthene, and sparse amounts of biotite. Commonly interlayered with amphibolite and mafic-rich quartz-plagioclase gneiss.

Lithology: gneiss; amphibolite

Allentown Formation (Cambrian) at surface, covers 0.3 % of this area

Allentown Formation - Medium- to medium-dark-gray, thick-bedded dolomite and impure limestone; dark-gray chert stringers and nodules; laminated; oolitic and stromatolitic; some orange-brown-weathering calcareous siltstone at base.

Lithology: dolostone (dolomite); limestone; chert; siltstone

Stockton Formation Cobble Conglomerate and Sandstone facies (Upper Triassic) at surface, covers < 0.1 % of this area

Stockton Formation Cobble Conglomerate and Sandstone facies - Predominantly medium- to coarse-grained, light-gray, light-grayish-brown, or yellowish- to pinkish-gray arkosic sandstone and medium- to fine-grained, violet-gray to reddish-brown arkosic sandstone; with lesser, reddish to purplish-brown, silty mudstone, argillaceous siltstone, and shale. Some coarse-grained sandstone in lower part contains thick beds of conglomerate (Trsc) which have been mapped in the vicinity of Stockton. Sandstone, deposited in high-gradient stream channels, is mostly planar bedded with scoured bases containing pebble lags and mudstone rip-up clasts. Upper part of channel beds are burrowed. Large-scale trough crossbeds occur in some very coarse grained sandstone beds; smaller scale trough and climbing-ripple cross lamination occur in the upper part of channel sequences and in finer grained sandstone beds. Typical floodplain mudstones are irregularly thin bedded and extensively burrowed. Floodplain beds are thicker and more numerous in the central Newark basin, near the Delaware River. Thickness of the unit (including Trsc) near Stockton is about 1,240 m (4,068 ft).

Lithology: conglomerate

Rondout and Decker Formations, undivided (Lower Devonian and Upper Silurian) at surface, covers < 0.1 % of this area

Rondout and Decker Formations, undivided - Rondout Formation (Clarke and Schuchert, 1899) - Upper part is medium-gray weathering, medium-dark-gray, very fine to fine-grained, medium-bedded, fossiliferous, argillaceous limestone. Middle part is light-medium-gray-weathering, medium-gray, laminated to medium-bedded, argillaceous dolomite. Locally contains deep desiccation polygons. Lower part is medium-gray-weathering, medium- to dark-gray, very fine to medium-grained, medium-bedded fossiliferous limestone. Silurian-Devonian boundary placed in middle of formation (Denkler and Harris, 1988). Lower contact abrupt and placed at top of highest calcareous quartz sandstone. Thickness approximately 12 m (40 ft). Decker Formation (White, 1882) - Light-gray- to yellowish-gray-weathering, light- to medium-gray, calcareous quartz siltstone, sandstone, and fine-pebble conglomerate locally interbedded with fossiliferous medium-gray, medium- to coarse-grained limestone and very fine grained, thin- to medium-bedded dolomite. Lower contact gradational. Thickness varies from 15 m (50 ft) near Duttonville to 25 m (82 ft) at Wallpack Center.

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

Mafic gneiss (Precambrian) at surface, covers < 0.1 % of this area

Mafic gneiss - Dark, medium grained; includes rocks of probable sedimentary origin; may be equivalent to "PZmgp" in places.

Lithology: mafic gneiss; paragneiss

Buffalo Springs Formation (Cambrian) at surface, covers < 0.1 % of this area

Buffalo Springs Formation - Light-gray to pinkish-gray, finely to coarsely crystalline limestone and interbedded dolomite; numerous siliceous and clayey laminae; stromatolitic limestone beds near top; some thin sandy beds.

Lithology: limestone; dolostone (dolomite); sandstone

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

Lower Walton Formation - shale, sandstone, conglomerate.

Lithology: shale; sandstone; conglomerate

Warrior Formation (Cambrian) at surface, covers < 0.1 % of this area

Warrior Formation - Gray, thin- to medium-bedded, fossiliferous, cyclic limestone bearing stromatolites; interbedded with thick-bedded crystalline dolomite and some sandstone.

Lithology: limestone; dolostone (dolomite); sandstone

Gneiss granofels and Migmatite (Middle Proterozoic) at surface, covers < 0.1 % of this area

Gneiss granofels and Migmatite - Gneiss and granofels range in composition from felsic to intermediate to mafic; intermediate compositions predominate. Contains a wide variety of rock types including graphitic schist and marble. Many rocks were injected by a granitoid that has blue quartz and augen of potassic feldspar and are arteritic migmatites. One body of gneiss contains a 1 m by 0.5 m (3 by 2 ft) phacoid of gabbro that is interpreted to be an olistolith. Unit probably represents a sequence of meta-sedimentary and metavolcanic rocks that have been heavily injected and migmatized by felsic magma.

Lithology: gneiss; granofels; schist; marble; migmatite

Hardyston Formation (Cambrian) at surface, covers < 0.1 % of this area

Hardyston Formation - Typically light-gray, fine- to medium-grained quartzite, and feldspathic sandstone; color ranges from nearly white to dark gray; massive bedded; Scolithus present in upper part; quartz-pebble conglomerate occurs at base.

Lithology: quartzite; sandstone; conglomerate

Coburn Formation through Loysburg Formation, undivided (Ordovician) at surface, covers 0.1 % of this area

Coburn Formation through Loysburg Formation, undivided - Includes, in descending order, the Coburn Formation through Nealmont Formation, undivided (Ocn) and Benner Formation through Loysburg Formation, undivided (Obl).

Lithology: limestone; shale; dolostone (dolomite); calcarenite; metavolcanic rock

Leithsville Formation (Middle and Lower Cambrian) at surface, covers < 0.1 % of this area

Leithsville Formation (Middle and Lower Cambrian) (Wherry, 1909) - Light- to dark-gray and lightolive-gray, fine- to medium-grained, thin- to medium-bedded dolomite. Grades downward through medium-gray, grayish-yellow, or pinkish-gray dolomite and dolomitic sandstone, siltstone and shale to medium-gray, medium-grained, medium-bedded dolomite containing quartz sand grains as stringers and lenses near the base. Lower contact gradational. Thickness ranges from 0 to 56 m (0-185 ft) due to erosion.

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

Harpers Formation (Cambrian) at surface, covers < 0.1 % of this area

Harpers Formation - Dark-greenish-gray phyllite and schist containing thin quartzite layers.

Lithology: phyllite; schist; quartzite

New Oxford conglomerate (Triassic) at surface, covers < 0.1 % of this area

New Oxford conglomerate - Quartz or quartzite pebbles, cobbles, and rare boulders set in a red, sandy, ferruginous matrix; some silica cement; some feldspar clasts.

Lithology: conglomerate; quartzite; sand

Onondaga Formation through Poxono Island Formation, undivided (Devonian and Silurian) at surface, covers < 0.1 % 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

Diabase (Jurassic) at surface, covers < 0.1 % of this area

Diabase - Concordant to discordant, predominantly sheet-like intrusions of medium- to fine-grained diabase and dikes of fine-grained diabase; dark-greenish-gray to black; subophitic texture. Dense, hard, sparsely fractured rock composed mostly of plagioclase (An50-70), clinopyroxene (mostly augite), and magnetite-ilmenite. Orthopyroxene (En75-80) is locally abundant in the lower part of the sheets. Accessory minerals include apatite, quartz, alkali feldspar, hornblende, sphene, zircon, and rare olivine. Diabase in the map area was derived primarily from high-titanium, quartz-tholeiite magma. Sedimentary rocks within about 300 m (984 ft) above and 200 m (656 ft) below major diabase sheets are thermally metamorphosed. Red mudstone is typically altered to indurated, bluish-gray hornfels with clots or crystals of tourmaline or cordierite. Gray argillitic siltstone is typically altered to brittle, black, very fine grained hornfels. Sills are 365 to 400 m (1,197-1,312 ft) thick. Dikes range in thickness from 3 to 10 m (10-33 ft) and are many kilometers long.

Lithology: diabase

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

Venango Formation - Light-gray siltstone interbedded with some flaggy, gray sandstone and some bluish-gray shale; Panama Conglomerate and Woodcock Sandstone are, respectively, the lower and upper key beds defining the formation; referred to as "Cattaraugus" by some workers; includes some red shales where it interfingers to the east and south with the Catskill Formation; marine fossils present.

Lithology: siltstone; sandstone; shale; conglomerate

Shawangunk Formation (Middle and Lower Silurian) at surface, covers < 0.1 % of this area

Shawangunk Formation (Mather, 1840; Epstein and Epstein, 1972) - Upper part is medium- to medium-dark-gray, or dark-greenish-gray, medium- to thick-bedded sandstone and pebble conglomerate having well rounded grains, some of which are limonite stained. Conglomerate consists of matrix-supported quartz and subordinate shale pebbles as long as 5 cm (2 in.) in poorly to well-sorted, planar tabular to trough crossbedded sandstone. Local black to dark-greenish-gray, thin-bedded shale near upper contact. Middle part, occurring in southwest and sporadically in northeast, is light- to medium-dark-gray, greenish-gray, interbedded thin- to medium-bedded, planar tabular to trough cross-bedded shale and sandstone. Grains are well rounded and moderately to well sorted. Contains sparse graphite flakes. Lower part is light- to medium-gray to light-olive-gray, thin- to thick-bedded quartz and feldspathic sandstone, quartzite, and quartz-pebble conglomerate, which is matrix-supported, poorly to well sorted, cross to planar bedded. Clasts are primarily quartz and sparse dark-gray argillite and black chert. Sandstone is feldspathic and locally approaches an arkose in compostion. Lower contact unconformable and, at places, is a fault of small displacement. Thickness approximately 427 m (1,400 ft).

Lithology: sandstone; conglomerate; shale

Pocono and Rockwell Formations, undivided (Mississippian and Devonian) at surface, covers < 0.1 % of this area

Pocono and Rockwell Formations, undivided: Buff, medium-grained, crossbedded sandstone and some conglomerate (Pocono), overlying buff to olive-gray, fine- to medium-grained, crossbedded sandstone containing a few beds of shale and conglomerate (Rockwell); shown in southwestern Bedford County only.

Lithology: sandstone; conglomerate; shale

Passaic Formation (Lower Jurassic and Upper Triassic) at surface, covers < 0.1 % of this area

Passaic Formation - Predominantly red beds consisting of argillaceous siltstone; silty mudstone; argillaceous, very fine grained sandstone; and shale; mostly reddish-brown to brownish-purple, and grayish-red. Red beds occur typically in 3- to 7-m (10- to 23-ft-)-thick, cyclic playa-lake-mudflat sequences and fining-upward fluvial sequences. Lamination is commonly indistinct due to burrowing, desiccation, and paleosol formation. Where layering is preserved, most bedforms are wavy parallel lamination and trough and climbing-ripple cross lamination. Calcite- or dolomite-filled vugs and flattened cavities, mostly 0.5 to 0.2 mm (0.02-0.08 in) across, occur mostly in the lower half. Sand-filled burrows, 2 to 5 mm (0.08-0.2 in) in diameter, are prevalent in the upper two-thirds of the unit. Desiccation cracks, intraformational breccias, and curled silt laminae are abundant in the lower half. Lake cycles, mostly 2 to 5 m (7-16 ft) thick, have a basal, greenish-gray, argillaceous siltstone; a medial, dark-gray to black, pyritic, carbonaceous, fossiliferous, and, in places, calcareous lake-bottom fissile mudstone or siltstone; and an upper thick-bedded, gray to reddish and purplish-gray argillaceous siltstone with desiccation cracks, intraformational breccias, burrows, and mineralized vugs. Thickness of the formation between Sourland Mountain and Sand Brook syncline is about 3,500 m (11,483 ft).

Lithology: siltstone; sandstone; shale

Lockatong Formation (Upper Triassic) at surface, covers < 0.1 % of this area

Lockatong Formation - Predominantly cyclic lacustrine sequences of silty, dolomitic or analcime-bearing argillite; laminated mudstone; silty to calcareous, argillaceous very fine grained sandstone and pyritic siltstone; and minor silty limestone, mostly light- to dark-gray, greenishgray, and black. Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) occur in some places, especially in upper half. Two types of cycles are recognized: freshwater-lake (detrital) and alkaline-lake (chemical) cycles. Freshwater-lake cycles average 5.2 m (17 ft) thick. They consist of basal, transgressive, fluvial to lake-margin deposits that are argillaceous, very fine grained sandstone to coarse siltstone with indistinct lamination, planar or cross lamination, or are disrupted by convolute bedding, desiccation cracks, root casts, soil-ped casts, and tubes. Medial lake-bottom deposits are laminated siltstones, silty mudstones, or silty limestones that are dark gray to black with calcite laminae and grains and lenses, or streaks of pyrite; fossils are common, including fish scales and articulated fish, conchostracans, plants, spores, and pollen. Upper regressive lake margin, playa lake, and mudflat deposits are light- to dark-gray silty mudstone to argillitic siltstone or very fine grained sandstone, mostly thick bedded to massive, with desiccation cracks, intraformational breccias, faint wavy laminations, burrows, euhedral pyrite grains, and dolomite or calcite specks. Alkaline-lake cycles are similar to freshwater-lake cycles, but are thinner, averaging 3 m (10 ft), have fewer fossils (mainly conchostracans), and commonly have red beds, extensive desiccation features, and abundant analcime and dolomite specks in the upper parts of cycles. Thickness near Byram is about 1,070 m (3,510 ft). The formation thins to the southeast and northeast; thickness near Princeton is less than 700 m (2,297 ft).

Lithology: argillite; mudstone; sandstone; siltstone; limestone

Passaic Formation gray bed (Lower Jurassic and Upper Triassic) at surface, covers < 0.1 % of this area

Passaic Formation gray bed - Upper Triassic gray lake deposits (Trpg) consist of gray to black silty mudstone, gray and greenish- to purplish-gray argillaceous siltstone, black shale, and medium- to dark-gray, argillaceous, fine-grained sandstone and are abundant in the lower half of the Passaic Formation. Gray lakebeds occur in groups of two to five cycles although they also occur as single cycles in some parts of the formation. Several lakebed sequences consisting of one or two thick groups of drab-colored beds as much as 30 m (98 ft) thick or more can be traced over tens of kilometers. Many gray-bed sequences are locally correlated within fault blocks; some can be correlated across major faults or intrusive rock units. Thickness of the (entire Passaic) formation between Sourland Mountain and Sand Brook syncline is about 3,500 m (11,483 ft).

Lithology: fine-grained mixed clastic; siltstone; black shale; sandstone

Beekmantown Group, Upper Part (Lower Ordovician) at surface, covers < 0.1 % of this area

Beekmantown Group, Upper Part (Clarke and Schuchert, 1899) - Locally preserved upper beds are light- to medium-gray- to yellowish-gray-weathering, medium-light- to medium-gray, aphanitic to medium-grained, thin- to thick-bedded, locally laminated, slightly fetid dolomite. Medium-dark to dark-gray, fine-grained, medium-bedded, sparsely fossiliferous limestone lenses occur locally. Lower beds are medium-dark- to dark-gray, medium- to coarse-grained, mottled surface weathering, medium- to thick-bedded, strongly fetid dolomite that contains pods and lenses of dark-gray to black chert. Cauliflower-textured black chert beds of variable thickness occur locally. Gradational lower contact is placed at top of laminated to thin-bedded dolomite of the lower part (Obl) of the Beekmantown Group. Contains conodonts high in the Rossodus manitouensis zone to low zone D of the North American midcontinent province as used by Sweet and Bergstrom (1986). Upper beds are included in Epler Formation; lower beds are included in Rickenbach Dolomite of Drake and Lyttle (1985) and Drake and others (1985); entire upper part (Obu) is Ontelaunee Formation of Markewicz and Dalton (1977). Thickness ranges from 0 to 244 m (0-800 ft).

Lithology: dolostone (dolomite); limestone

Weverton and Loudoun Formations, undivided (Cambrian) at surface, covers 0.1 % of this area

Weverton and Loudoun Formations, undivided - In descending order: Weverton--gray to purplish-gray quartzite and quartzose conglomerate containing rounded pebbles. Loudoun--sericitic slate and purplish-gray, crumbly, poorly sorted, arkosic sandstone and conglomerate.

Lithology: quartzite; slate; conglomerate; arkose

Burgoon Sandstone through Cuyahoga Group, undifferentiated (Mississippian) at surface, covers < 0.1 % of this area

Burgoon Sandstone through Cuyahoga Group, undifferentiated - Informal unit including elements of Burgoon Sandstone and Shenango Formation plus Cuyahoga Group; correlation uncertain; contains sedimentary structures and trace fossils characteristic of tidal flats; called "Pocono" by earlier workers.

Lithology: sandstone; shale; siltstone; conglomerate

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

Gardeau Formation - shale, siltstone; Roricks Glen Shale.

Lithology: shale; siltstone

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

Honesdale Formation - sandstone, shale.

Lithology: sandstone; shale

Metarhyolite (Precambrian) at surface, covers 0.2 % of this area

Metarhyolite - Light gray, green, and purple; commonly schistose, containing quartz augen and veins.

Lithology: meta-rhyolite

Sams Creek Metabasalt (Late Precambrian (?)) at surface, covers < 0.1 % of this area

Sams Creek Metabasalt - Grayish-green, massive to schistose, amygdaloidal metabasalt.

Lithology: meta-basalt

Mauch Chunk Formation (Mississippian) at surface, covers < 0.1 % of this area

Mauch Chunk Formation - Red and green shale, reddish-purple mudstone, and red, green, brown, and gray thin-bedded and cross-bedded sandstones; thickness 500 feet in west, increases to about 800 feet in east.

Lithology: shale; mudstone; sandstone

Connoquenessing and Sharon Formations (Lower Pennsylvanian) at surface, covers < 0.1 % of this area

Connoquenessing and Sharon Formations - sandstone, shale; Sharon Formation-shale, sandstone, conglomerate; Olean Conglomerate 50-100 ft. (15-30 m).

Lithology: sandstone; shale; conglomerate

Northeast Shale (Devonian) at surface, covers 0.1 % of this area

Northeast Shale - Medium-gray shale and some thin light-gray siltstone interbeds; included in Canadaway Formation of New York; included in "Chemung" of earlier workers; contains sparse fossil marine fauna.

Lithology: shale; siltstone

Amphibolite (Middle Proterozoic) at surface, covers < 0.1 % of this area

Amphibolite - Gray- to grayish-black, medium-grained amphibolite composed of hornblende and andesine. Some phases contain biotite and (or) clinopyroxene. Ubiquitous and associated with almost all other Middle Proterozoic units. Some amphibolite is clearly metavolcanic in origin, some is metasedimentary, and some appears to be metagabbro.

Lithology: amphibolite

Onondaga Limestone (Lower to Middle Devonian) at surface, covers < 0.1 % of this area

Onondaga Limestone - Schoharie Formation-shale, limestone; Carlisle Center Siltstone; Esopus Shale.

Lithology: shale; limestone; siltstone

Amphibolite (Paleozoic) at surface, covers < 0.1 % of this area

Amphibolite - amphibolite

Lithology: amphibolite

Mines Member of Gatesburg Formation (Cambrian) at surface, covers < 0.1 % of this area

Mines Member of Gatesburg Formation - Gray dolomite containing siliceous "oolites" and chert having cryptozoon stromatolites.

Lithology: dolostone (dolomite); chert

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

Axemann Formation - Medium-gray fossiliferous limestone.

Lithology: limestone

Greenstone schist (Precambrian) at surface, covers < 0.1 % of this area

Greenstone schist - Fine to medium grained, light to medium green; includes probable metavolcanic rocks.

Lithology: schist; metavolcanic rock

Shriver, Mandata, Corriganville, and New Creek Members of Old Port Formation, undivided (Devonian) at surface, covers < 0.1 % of this area

Shriver, Mandata, Corriganville, and New Creek Members of Old Port Formation, undivided - Limestone, chert, shale, and siliceous siltstone. In Fulton County, limestone and chert of the Licking Creek Member replaces the Shriver and Mandata.

Lithology: shale; limestone; chert; siltstone

Hershey Formation through Annville Formation, undivided (Ordovician) at surface, covers < 0.1 % of this area

Hershey Formation through Annville Formation, undivided - Includes, in descending order, the Hershey and Myerstown Formations, undivided (Ohm) and Annville Formation (Oan).

Lithology: limestone

Moscow Formation (Middle Devonian) at surface, covers < 0.1 % of this area

Moscow Formation - in west: Cooperstown and Portland Point shale and sandstone Members; In east: "Manorkill" and Portland Point shale and sandstone Members.

Lithology: shale; sandstone

Pleasant Hill Formation (Cambrian) at surface, covers < 0.1 % of this area

Pleasant Hill Formation - Gray, thin-bedded, argillaceous limestone interbedded with shale, siltstone, and sandstone.

Lithology: limestone; shale; siltstone; sandstone

Stockton conglomerate (Triassic) at surface, covers < 0.1 % of this area

Stockton conglomerate - Quartz cobbles set in a poorly sorted, sandy matrix; includes conglomeratic sandstone.

Lithology: conglomerate; sand; sandstone

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

Chambersburg Formation - Dark-gray, cobbly, argillaceous limestone; abundant irregular shale partings; some metabentonite beds present.

Lithology: limestone; shale; metavolcanic rock

Cockeysville Marble (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Cockeysville Marble - White to light bluish gray, finely to coarsely crystalline.

Lithology: marble

Hamburg sequence rocks (Ordovician) at surface, covers 0.8 % of this area

Hamburg sequence rocks - Predominantly greenish gray, gray, purple, and maroon shale, siltstone, and graywacke; includes some wildflysch having Martinsburg matrix.

Lithology: shale; siltstone; graywacke; conglomerate

Passaic Formation Quatzite-clast Conglomerate facies (Lower Jurassic and Upper Triassic) at surface, covers < 0.1 % of this area

Passaic Formation Quartzite-clast Conglomerate facies - Quartzite conglomerate unit (JTrpcq) is reddish-brown pebble conglomerate, pebbly sandstone, and sandstone, in upward-fining sequences 1 to 2 m (3-6 ft) thick. Clasts are subangular to subrounded, quartz and quartzite in sandstone matrix. Sandstone is medium to coarse grained, feldspathic (up to 20 percent feldspar), and locally contains pebble and cobble layers. Conglomerate thickness exceeds 850 m (2,790 ft).

Lithology: conglomerate; sandstone

Walcksville and Towamensing Members of Catskill Formation, undivided (Devonian) at surface, covers < 0.1 % 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

Berea Sandstone through Riceville Formation, undivided (Devonian) at surface, covers 0.2 % of this area

Berea Sandstone through Riceville Formation, undivided - Sandstone, siltstone, and shale; mostly light to dark gray, but some sandstone is greenish yellow, and a few reddish shales occur. Includes, in descending order: Berea Sandstone, Bedford Shale, Cussewago Sandstone, and Riceville Shale; marine fossils common.

Lithology: shale; sandstone; siltstone

Millbach and Schaefferstown Formations, undivided (Cambrian) at surface, covers < 0.1 % of this area

Millbach and Schaefferstown Formations, undivided - Includes, in descending order, the Millbach Formation (CAm), and the Schaefferstown Formation--gray limestone containing siliceous and argillaceous laminae; thin bedded.

Lithology: limestone; dolostone (dolomite); shale

Greene Formation (Permian) at surface, covers 1 % of this area

Greene Formation - Cyclic sequences of sandstone, shale, red beds, thin limestone, and thin, impure coal; base is at top of Upper Washington limestone.

Lithology: sandstone; shale; limestone; coal

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

Rickenbach Formation - Gray, very finely to coarsely crystalline, laminated dolomite; dark-gray chert in irregular beds, stringers, and nodules; bands of quartz sand grains in lower half.

Lithology: dolostone (dolomite); chert

Marcellus Shale (Middle Devonian) at surface, covers < 0.1 % of this area

Marcellus Shale (Vanuxem, 1840) - Medium-gray weathering, dark-gray to grayish-black, thin- to thick-bedded, fossiliferous, fissile and limonite-stained locally arenaceous shale. Lower contact grades downward over 12 m (40 ft) from black shale through limy shale, into silty limestone of the Buttermilk Falls Limestone (documented in drill core data of Fletcher and Woodrow, 1970). Approximately 274 m (900 ft) thick.

Lithology: black shale; shale; siltstone; sandstone

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

Nittany Formation - Medium- to dark-gray, thick-bedded dolomite containing chert and siliceous oolites.

Lithology: dolostone (dolomite); chert

Jacksonburg Limestone (Middle Ordovician) at surface, covers < 0.1 % of this area

Jacksonburg Limestone (Kummel, 1908; Miller, 1937) - Upper part is medium- to dark-gray, laminated to thin-bedded shaly limestone and less abundant medium-gray arenaceous limestone containing quartz-sand lenses. Upper part thin to absent to northeast. Lower part is interbedded medium- to dark-gray, fine- to medium-grained, very thin to medium-bedded fossiliferous limestone and minor medium- to thick-bedded dolomite-cobble conglomerate having a limestone matrix. Unconformable on Beekmantown Group and conformable on the discontinuous sequence at Wantage in the Paulins Kill area. Contains conodonts of North American midcontinent province from Phragmodus undatus to Aphelognathus shatzeri zones of Sweet and Bergstrom (1986). Thickness ranges from 41 to 244m (135-800 ft).

Lithology: limestone; conglomerate

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

Jacksonburg Formation - Dark-gray shaly limestone (cement rock) having slaty cleavage; basal medium- to thick-bedded limestone (cement limestone) increases in thickness eastward.

Lithology: limestone; shale

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

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

Lithology: sandstone; shale; siltstone

Zullinger Formation (Cambrian) at surface, covers 0.2 % of this area

Zullinger Formation - Interbanded and interlaminated limestone and dolomite, thin- to thick-bedded; stromatolitic limestone; several thin, local quartz sandstone beds.

Lithology: limestone; dolostone (dolomite); sandstone

Benner Formation through Loysburg Formation, undivided (Ordovician) at surface, covers 0.1 % of this area

Benner Formation through Loysburg Formation, undivided - In descending order: Benner Formation--light- to dark-gray, thick-bedded limestone (calcilutite); includes chemically pure Valentine Member (Obv) at top, and, below, the less pure Valley View Member, which contains metabentonite beds--all laterally equivalent to impure limestones of Oak Hall Member; Stover Member at base is dark-gray limestone (calcilutite) having dolomite streaks; Benner is called "Linden Hall" by some workers. Snyder Formation--light- to medium-gray limestone, laminated to medium-bedded; has mud cracks, oolites, and dolomitic layers. Hatter Formation--medium-gray, fossiliferous, argillaceous limestone, laminated and dolomitic. Loysburg Formation--light- to medium-gray, medium-bedded limestone (Clover Member) overlying laminated, alternating limestone, dolomitic limestone, and dolomite (Milroy ["tiger-striped"] Member).

Lithology: limestone; dolostone (dolomite); metavolcanic rock

Chilhowee Group; Harpers Formation (Cambrian) at surface, covers < 0.1 % of this area

Harpers Formation - Brown to dark bluish-gray banded shale, to light bluish-gray, finely laminated phyllite; distinctively pale purple in basal part; bedding obscured by cleavage; increasingly metamorphosed toward east from shale to slate and phyllite; estimated thickness 2,000 feet.

Lithology: shale; phyllite; slate

Coburn Formation through Nealmont Formation, undivided (Ordovician) at surface, covers 0.2 % of this area

Coburn Formation through Nealmont Formation, undivided - In descending order: Coburn Formation--medium-gray to very dark gray, very fossiliferous limestone and shaly limestone; Salona Formation--very dark gray to black, nonfossiliferous shaly limestone and calcareous shale containing metabentonite beds; Nealmont Formation--medium-gray fossiliferous limestone (calcarenite--Rodman Member) overlying thin-bedded shaly limestone (calcilutite--Center Hall Member).

Lithology: limestone; shale; metavolcanic rock; calcarenite

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

Cocalico Formation - Gray phyllitic shale, maroon shale, siltstone, and silty, siliceous shale; some interbedded argillaceous and quartzose sandstone; predominantly allochthonous, and probably closely related to Hamburg sequence, but includes some autochthonous elements.

Lithology: shale; siltstone; sandstone

Anorthosite (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Anorthosite - Medium to coarse grained, light to dark bluish gray, predominantly plagioclase; local alteration minerals.

Lithology: anorthosite

Graywacke of Hamburg sequence (Ordovician) at surface, covers < 0.1 % of this area

Graywacke of Hamburg sequence - Predominantly graywacke.

Lithology: graywacke

Girard Shale (Devonian) at surface, covers 0.3 % of this area

Girard Shale - Argillaceous, ashen-gray, flaky shale and siltstone; included in Conneaut Group and "Chemung" of earlier workers; marine fossils rare.

Lithology: shale; siltstone

Pegmatite (Paleozoic) at surface, covers < 0.1 % of this area

Pegmatite - Pegmatite

Lithology: pegmatite

Wissahickon Formation; Metagraywacke (Late Precambrian (?)) at surface, covers < 0.1 % of this area

Wissahickon Formation; Metagraywacke - (Formerly mapped as Peters Creek Formation.) Rhythmically interbedded chlorite-muscovite meta-graywacke and fine-grained chlorite-muscovite schist; graded bedding locally preserved; thickness probably 2,000 to 3,000 feet.

Lithology: metasedimentary rock; schist

Heidlersburg Member of Gettysburg Formation (Triassic) at surface, covers 0.1 % of this area

Heidlersburg Member of Gettysburg Formation - Red, green, and gray shale and argillite, and minor thin beds of gray arkosic sandstone; some quartz conglomerate and limestone conglomerate.

Lithology: shale; argillite; arkose; conglomerate; limestone

Ultramafic Rocks (Early Paleozoic - Late Precambrian (?)) at surface, covers < 0.1 % of this area

Ultramafic Rocks - Chiefly serpentinite with partly to completely altered dunite, peridotite, pyroxenite, and massive to schistose soapstone; talc-carbonate rock and altered gabbro are common in some bodies.

Lithology: serpentinite; dunite; peridotite; pyroxenite; gabbro

Wissahickon Formation (Undivided) (Late Precambrian (?)) at surface, covers < 0.1 % of this area

Wissahickon Formation (Undivided) - Muscovite-chlorite-albite schist, muscovite-chlorite schist, chloritoid schist, and quartzite; intensely folded and cleaved.

Lithology: schist; quartzite

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

New Milford Formation - "New Milford" Formation: sandstone, shale.

Lithology: sandstone; shale

Bloomsburg Red Beds (Upper Silurian) at surface, covers < 0.1 % of this area

Bloomsburg Red Beds (White, 1883) (High Falls Shale of previous usage) - Grayish-red, thin- to thick-bedded, poorly to moderately well sorted, massive siltstone, sandstone, and local quartz-pebble conglomerate containing local planar to trough crossbedded laminations. Conglomerate consists of matrix-supported quartz pebbles in grayish-red, fine-grained sandstone matrix. Locally, near base of unit, is greenish-gray, light-gray, or grayish-orange, massive, planar tabular to trough crossbedded quartz sandstone to siltstone with subrounded grains. Lower part of formation marked by several upward-fining sequences of light-gray sandstone grading through grayish-red, fine-grained sandstone and siltstone to grayish-red, mudcracked siltstone and mudstone. Each sequence is 1 to 3 m (3-10 ft) thick. Lower contact placed at bottom of lowermost red sandstone. Thickness approximately 460 m (1,510 ft).

Lithology: siltstone; sandstone; conglomerate; mudstone

Wakefield Marble (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Wakefield Marble - Light gray, coarsely crystalline; contains graphite flakes in places.

Lithology: marble

Sedimentary strata at Jacksonwald and Aspers (Jurassic) at surface, covers < 0.1 % of this area

Sedimentary strata at Jacksonwald and Aspers - Arkosic sandstone; fossiliferous, gray to black shale and limestone; ripple-cross-laminated siltstone; and boulder conglomerate.

Lithology: arkose; shale; limestone; siltstone; conglomerate

Passaic Formation Conglomerate and Sandstone facies (Lower Jurassic and Upper Triassic) at surface, covers < 0.1 % of this area

Passaic Formation Conglomerate and Sandstone facies - Conglomeratic sandstone (JTrpsc) is brownish-red pebble conglomerate, medium- to coarse-grained, feldspathic sandstone and micaceous siltstone; unit is planar to low-angle trough cross laminated, burrowed, and contains local pebble layers. Unit forms upward-fining sequences 0.5 to 2.5 m (1.6-8 ft) thick. Conglomeratic sandstone thickness exceeds 800 m (2,625 ft).

Lithology: conglomerate; sandstone; siltstone

New Oxford Formation (Triassic) at surface, covers < 0.1 % of this area

New Oxford Formation - Red, maroon, and gray sandstone, siltstone, and shale; basal conglomerate member: From vicinity of Maryland Rte. 73 and southward, limestone conglomerate with red and gray calcareous matrix; northward, quartz conglomerate with red sandy matrix; estimated total thickness 4,500 feet.

Lithology: shale; sandstone; siltstone; conglomerate

Conemaugh Group (Pennsylvanian) at surface, covers < 0.1 % of this area

Conemaugh Group - cyclic sequences of red and gray shale, siltstone, and sandstone, with thin limestones and coals. Mostly non-marine. May be divided into Casselman and Glenshaw Formations. Extends from the base of the Pittsburgh coal to the top of the Upper Freeport coal. Includes the Elk Lick, Bakerstown, and Mahoning coals, and the Ames and Brush Creek Limestones.

Lithology: shale; siltstone; sandstone; limestone; coal

Shale and graywacke of Hamburg sequence (Ordovician) at surface, covers 0.4 % of this area

Shale and graywacke of Hamburg sequence - Shale containing zones of conspicuous graywacke.

Lithology: shale; graywacke

Setters Quartzite (Probably lower Paleozoic) at surface, covers < 0.1 % of this area

Setters Quartzite - Includes white feldspathic quartzite, gray mica gneiss, and mica schist.

Lithology: quartzite; mica gneiss; mica schist

Oriskany Group, undivided (Lower Devonian) at surface, covers < 0.1 % of this area

Oriskany Group, undivided (Willard, 1938) - Thickness ranges from 38 m (125 ft) in southwest to 52 m (170 ft) in northeast. Ridgely Sandstone (Swartz and others, 1913) - White-weathering, medium-gray, medium- to thick-bedded, carbonate-cemented quartz-pebble conglomerate and coarse quartz sandstone, which contain abundant brachiopods. Moderately well sorted, subrounded sand gains. Unit thins northeastward and pinches out at Peters Valley. Lower contact abrupt. Thickness ranges from 0 to 10 m (0-32 ft). Shriver Chert (Swartz and others, 1913) - Medium- to dark-gray-weathering, black to dark-gray, medium-to-thick-bedded siltstone and shale containing interbedded black chert and local chert-bearing limestone. Present only in southwestern part of outcrop area where lower contact is gradational with silty limestone of Glenarie Formation. Thickness ranges from 0 to 9 m (0-30 ft). Glenarie Formation (Chadwick, 1908) - Medium-gray-weathering, medium- to dark-gray, fine-grained, thin- to medium-bedded, fossiliferous, silty limestone, and local chert lenses. Unit thickens to northeast. Lower contact probably gradational. Thickness ranges from 17 to 52 m (55-170 ft).

Lithology: sandstone; limestone; siltstone; conglomerate; black shale; chert

Valentine Member of Benner Formation (Ordovician) at surface, covers < 0.1 % of this area

Valentine Member of Benner Formation - Chemically pure limestone; occurs at top of Benner Formation.

Lithology: limestone

Bossardville Limestone (Upper Silurian) at surface, covers < 0.1 % of this area

Bossardville Limestone (White, 1882) - Light-gray to yellowish- gray-weathering, medium-gray to medium-dark-gray, very fine grained, locally fossiliferous, laminated to thin-bedded limestone and argillaceous limestone. Desiccation polygons occur in southwest. Lower contact is gradational and placed at top of uppermost dolomite. Thickness approximately 30 m (100 ft) in southwest, thinning to 3.1 m (10 ft) at New Jersey-New York State boundary.

Lithology: limestone

Cuyahoga and Knapp Formations (Lower Mississippian) at surface, covers < 0.1 % of this area

Cuyahoga and Knapp Formations - Cuyahoga Formation-shale, sandstone; Corry Sandstone; Knapp Formation-shale, conglomerate 60-100 ft. (20-30 m).

Lithology: shale; sandstone; conglomerate

Manhattan Schist (Lower Cambrian and (or) Late Proterozoic) at surface, covers < 0.1 % of this area

Manhattan Schist (Hall, in press) - Medium-dark gray, medium- to coarse-grained schist and gneiss composed of biotite, muscovite, quartz, and plagioclase, and local accessory minerals sillimanite, kyanite, tourmaline, and garnet. Contains some interlayered amphibolite. Unit is not exposed in the map area, but is present in boring logs.

Lithology: schist; gneiss; amphibolite

Anorthosite (Precambrian) at surface, covers < 0.1 % of this area

Anorthosite - Medium to coarse grained, light to dark bluish gray, predominantly plagioclase; local alteration minerals.

Lithology: anorthosite