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Geologic units in Pennsylvania (state in United States)

[Additional scientific data in this geographic area]

Amphibolite (Paleozoic) at surface, covers < 0.1 % of this area
Amphibolite - amphibolite
Lithology: amphibolite
Pegmatite (Paleozoic) at surface, covers < 0.1 % of this area
Pegmatite - Pegmatite
Lithology: pegmatite
Wissahickon Schist (Paleozoic) at surface, covers < 0.1 % of this area
Wissahickon Schist - Dense micaceous schist, gneiss and migmatite.
Lithology: mica schist; gneiss; migmatite
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
"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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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)
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
New Milford Formation (Upper Devonian) at surface, covers < 0.1 % of this area
New Milford Formation - "New Milford" Formation: sandstone, shale.
Lithology: sandstone; shale
Gardeau Formation (Upper Devonian) at surface, covers < 0.1 % of this area
Gardeau Formation - shale, siltstone; Roricks Glen Shale.
Lithology: shale; siltstone
Slide Mountain Formation (Upper Devonian) at surface, covers < 0.1 % of this area
Slide Mountain Formation - sandstone, shale, conglomerate.
Lithology: sandstone; shale; conglomerate
Upper Walton Formation (Upper Devonian) at surface, covers < 0.1 % of this area
Upper Walton Formation - shale, sandstone, conglomerate.
Lithology: shale; sandstone; conglomerate
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
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
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
Antietam Formation (Cambrian) at surface, covers < 0.1 % of this area
Antietam Formation - Gray, buff-weathering quartzite and quartz schist.
Lithology: quartzite; schist
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
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
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
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
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
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
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
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
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
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
Montalto Member of Harpers Formation (Cambrian) at surface, covers 0.1 % of this area
Montalto Member of Harpers Formation - Gray quartzite.
Lithology: quartzite
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
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)
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
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)
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
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
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
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
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
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
Tomstown Formation (Cambrian) at surface, covers 0.1 % of this area
Tomstown Formation - Massive dolomite containing thin shaly interbeds.
Lithology: dolostone (dolomite); shale
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
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
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
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
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
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
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)
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
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
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
Berea Sandstone through Venango Formation, undivided (Devonian) at surface, covers 0.7 % 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
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
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
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
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
Duncannon Member of Catskill Formation (Devonian) at surface, covers 0.2 % 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
Chadakoin Formation (Devonian) at surface, covers 0.9 % 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
Irish Valley Member of Catskill Formation (Devonian) at surface, covers 0.2 % 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
Catskill Formation (Devonian) at surface, covers 3 % 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
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
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
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
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
Poplar Gap and Packerton Members of Catskill Formation, undivided (Devonian) at surface, covers 0.5 % 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
Corry Sandstone through Riceville Formation, undivided (Devonian) at surface, covers 0.3 % 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
Sherman Creek Member of Catskill Formation (Devonian) at surface, covers 0.2 % 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
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
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
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
Foreknobs Formation (Devonian) at surface, covers 0.4 % 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
Girard Shale (Devonian) at surface, covers < 0.1 % 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
Hamilton Group (Devonian) at surface, covers 1 % of this area
Hamilton Group - Includes, in descending order, the Mahantango (Dmh) and Marcellus (Dmr) Formations.
Lithology: black shale; shale; siltstone; limestone; sandstone; bentonite
Lock Haven Formation (Devonian) at surface, covers 0.5 % 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
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
Mahantango Formation (Devonian) at surface, covers 0.1 % 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
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
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
Onondaga and Old Port Formations, undivided (Devonian) at surface, covers 0.4 % 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
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
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
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
Scherr Formation (Devonian) at surface, covers 0.3 % of this area
Scherr Formation - Chiefly siltstone; some fine-grained sandstone, shale, and mudstone; light olive gray; marine fossils.
Lithology: siltstone; sandstone; shale; mudstone
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)
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)
Keyser and Tonoloway Formations, undivided (Devonian and Silurian) at surface, covers 0.5 % of this area
Keyser and Tonoloway Formations, undivided - In descending order: Keyser Formation--medium-gray, crystalline to nodular, fossiliferous limestone; upper part laminated and mud-cracked; not present east of Harrisburg; passes into lower Coeymans, Rondout, and Decker Formations in the east. Tonoloway Formation--medium-gray, laminated, mud-cracked limestone containing some medium-dark- or olive-gray shale interbeds; lower part passes into Wills Creek Formation east and south; passes into Bossardville and Poxono Island beds in the east.
Lithology: limestone; shale
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
Trimmers Rock Formation (Devonian) at surface, covers 0.4 % of this area
Trimmers Rock Formation - Olive-gray siltstone and shale, characterized by graded bedding; marine fossils; some very fine grained sandstone in northeast; black shale of Harrell Formation at base in Susquehanna Valley.
Lithology: siltstone; shale; sandstone; black shale
Venango Formation (Devonian) at surface, covers 0.3 % 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
Diabase (Jurassic) at surface, covers 0.5 % 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
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
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
Burgoon Sandstone (Mississippian) at surface, covers 1 % 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
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
Cuyahoga Group (Mississippian) at surface, covers 0.3 % 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
Huntley Mountain Formation (Mississippian and Devonian) at surface, covers 2 % 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
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
Rockwell Formation (Mississippian and Devonian) at surface, covers 0.1 % 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
Spechty Kopf Formation (Mississippian and Devonian) at surface, covers 0.2 % 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
Shenango Formation through Oswayo Formation, undivided (Mississippian and Devonian) at surface, covers 0.2 % 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
Shenango Formation through Riceville Formation, undivided (Mississippian and Devonian) at surface, covers < 0.1 % 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
Mauch Chunk Formation (Mississippian) at surface, covers 1 % 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
Pocono Formation (Mississippian) at surface, covers 0.4 % 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
Shenango Formation (Mississippian) at surface, covers 0.5 % 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
Shenango Formation through Cuyahoga Group, undivided (Mississippian) at surface, covers 0.1 % 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
Axemann Formation (Ordovician) at surface, covers < 0.1 % of this area
Axemann Formation - Medium-gray fossiliferous limestone.
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
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
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
Bald Eagle Formation (Ordovician) at surface, covers 0.2 % 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
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
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
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
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
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
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
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
Epler Formation (Ordovician) at surface, covers 0.2 % of this area
Epler Formation - Very finely crystalline, light-gray limestone interbedded with gray dolomite; coarsely crystalline limestone lenses present.
Lithology: limestone; dolostone (dolomite)
Hamburg sequence rocks (Ordovician) at surface, covers 0.5 % 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
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
Graywacke of Hamburg sequence (Ordovician) at surface, covers < 0.1 % of this area
Graywacke of Hamburg sequence - Predominantly graywacke.
Lithology: graywacke
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
Limestone of Hamburg sequence (Ordovician) at surface, covers < 0.1 % of this area
Limestone of Hamburg sequence - Conspicuous limestone.
Lithology: limestone
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
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
Juniata Formation (Ordovician) at surface, covers 0.3 % 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
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
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
Martinsburg Formation (Ordovician) at surface, covers 1 % of this area
Martinsburg Formation - Gray to dark-gray, buff-weathering shale.
Lithology: shale
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
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
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
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
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
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
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
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
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
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
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
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)
Allegheny Formation (Pennsylvanian) at surface, covers 2 % 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
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
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
Casselman Formation (Pennsylvanian) at surface, covers 1 % 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
Glenshaw Formation (Pennsylvanian) at surface, covers 2 % 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
Llewellyn Formation (Pennsylvanian) at surface, covers 0.7 % 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
Monongahela Group (Pennsylvanian) at surface, covers 0.7 % 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
Pottsville Formation (Pennsylvanian) at surface, covers 3 % of this area
Pottsville Formation - Predominantly gray sandstone and conglomerate; also contains thin beds of shale, claystone, limestone, and coal; includes Olean and Sharon conglomerates of northwestern Pennsylvania; thin marine limestones present in Beaver, Lawrence, and Mercer Counties; minable coals and commercially valuable high-alumina clays present locally.
Lithology: sandstone; conglomerate; shale; siltstone; claystone; limestone; coal
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
Felsic and intermediate gneiss (Precambrian) at surface, covers < 0.1 % of this area
Felsic and intermediate gneiss - Light, medium grained; includes rocks of probable sedimentary origin.
Lithology: felsic gneiss; mafic gneiss; paragneiss
Felsic gneiss (Precambrian) at surface, covers < 0.1 % of this area
Felsic gneiss - Light, medium grained; includes rocks of probable sedimentary origin.
Lithology: felsic gneiss; paragneiss
Franklin Marble (Precambrian) at surface, covers < 0.1 % of this area
Franklin Marble - White, coarsely crystalline; disseminated graphite flakes.
Lithology: marble
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
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
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
Felsic to mafic gneiss (Precambrian) at surface, covers 0.3 % of this area
Felsic to mafic gneiss - Light, medium grained; predominantly quartz and feldspar of igneous origin.
Lithology: felsic gneiss; mafic gneiss; orthogneiss
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
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
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
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
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
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
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
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
Greene Formation (Permian) at surface, covers 0.2 % 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
Waynesburg Formation (Permian and Pennsylvanian) at surface, covers 0.3 % 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
Washington Formation (Permian) at surface, covers 0.4 % 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
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
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
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
"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;
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
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
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
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
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
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
Peters Creek Schist (Probably lower Paleozoic) at surface, covers 0.2 % of this area
Peters Creek Schist - Chlorite-sericite schist containing interbedded quartzite.
Lithology: schist; quartzite
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
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
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
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
Wissahickon Formation (Probably lower Paleozoic) at surface, covers 0.1 % 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
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
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
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
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
Bloomsburg and Mifflintown Formations, undivided (Silurian) at surface, covers 0.5 % 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
Clinton Group (Silurian) at surface, covers 0.8 % 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
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
Shawangunk Formation (Silurian) at surface, covers < 0.1 % 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
Tuscarora Formation (Silurian) at surface, covers 0.6 % 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
Wills Creek Formation (Silurian) at surface, covers 0.5 % of this area
Wills Creek Formation - Variegated gray, grayish-red, yellowish-gray and greenish-gray, interbedded calcareous shale, siltstone, shaly limestone, and dolomite; passes into Bloomsburg Formation in the southeast; not present east of Harrisburg.
Lithology: shale; siltstone; limestone; dolostone (dolomite)
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)
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
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
Brunswick Formation (Triassic) at surface, covers 0.3 % 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
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
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
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
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
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
Hammer Creek Formation (Triassic) at surface, covers 0.2 % of this area
Hammer Creek Formation - Gray and pale red, fine- to coarse-grained quartzose sandstone, siltstone, and mudstone.
Lithology: sandstone; siltstone; mudstone
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
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
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
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
Stockton Formation (Triassic) at surface, covers 0.3 % 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
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
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
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
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
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
Quaternary Alluvium (Quaternary) at surface, covers < 0.1 % of this area
Quaternary Alluvium - alluvial deposits of sand, gravel, silt, and clay.
Lithology: alluvium

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