Shale containing zones of conspicuous graywacke.
Predominantly greenish gray, gray, purple, and maroon shale, siltstone, and graywacke; includes some wildflysch having Martinsburg matrix.
Light, medium grained; predominantly quartz and feldspar of igneous origin.
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.
Cobble and pebble quartz conglomerate interbedded with red sandstone.
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.
Gray and pale red, fine- to coarse-grained quartzose sandstone, siltstone, and mudstone.
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.
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.
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.
Dark, medium grained; includes some rocks of probable sedimentary origin.
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.
Very finely crystalline, light-gray limestone interbedded with gray dolomite; coarsely crystalline limestone lenses present.
Light- to dark-gray, very finely to medium-crystalline dolomite containing interbeds of light-gray limestone; interbedded nodular, dark-gray chert at base.
Dark-gray shaly limestone (cement rock) having slaty cleavage; basal medium- to thick-bedded limestone (cement limestone) increases in thickness eastward.
Gray dolomite, in part oolitic, interbedded with medium-gray limestone and dark-gray oolitic chert.
Dark-gray, slaty to phyllitic shale, calcareous at base. Probably only lower part of Martinsburg Formation is present; overlain by Hamburg sequence rocks.
Includes, in descending order, the Ontelaunee (Oo), Epler (Oe), Rickenbach (Ori), and Stonehenge (Os) Formations.
In descending order: Hershey--dark-gray to black, thin-bedded, argillaceous limestone; Myerstown--medium- to dark-gray, platy, medium-crystalline limestone; carbonaceous at base.
Gray to dark-gray shale and slate.
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.
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.
Light-gray to buff, coarse-grained, arkosic sandstone; includes reddish-brown to grayish-purple sandstone, siltstone, and mudstone.
Shale containing conspicuous graywacke; includes autochthonous sandstone and shale of Shochary Ridge.
Pink to white and gray, finely laminated limestone and interbedded finely crystalline dolomite; numerous stromatolitic limestone beds.
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.
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.
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.
Gray, finely crystalline limestone containing dark-gray silty laminations; numerous edgewise conglomerate beds.
Light-gray, massive, high-calcium limestone; mottled at base.
Medium-gray, finely crystalline dolomite; silty to sandy, containing numerous siliceous to argillaceous laminae.
Grayish-red and greenish-gray shale, siltstone, and very fine to coarse-grained sandstone; some calcareous mudstone in central Pennsylvania; thins to west and is replaced by Mifflintown beds; thickens eastward, replacing overlying Wills Creek and Tonoloway Formations and underlying Mifflintown Formation.
Medium grained, light pink to greenish gray; largely quartz, feldspar, and mica; commonly gneissic, containing alteration minerals; interfingers with gabbroic gneiss.
Dark-gray, knotty, argillaceous dolomite; impure light-gray marble at base locally.
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
Includes, in descending order, the Millbach Formation (CAm), and the Schaefferstown Formation--gray limestone containing siliceous and argillaceous laminae; thin bedded.
Arkosic sandstone; fossiliferous, gray to black shale and limestone; ripple-cross-laminated siltstone; and boulder conglomerate.
Light-gray, locally mottled, massive, pure, coarsely crystalline dolomite; siliceous in middle part.
Includes, in descending order, the Juniata (Oj) and Bald Eagle (Obe) Formations.
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.
Light-gray, hard, massive, Scolithus-bearing quartzite and quartz schist; thin, interbedded dark slate at top; conglomerate (Hellam Member) at base.
Medium grained, medium to dark gray; locally gneissic, predominantly feldspar and quartz, plus dark accessories and various alteration minerals.
Medium-light-gray to medium-gray, finely crystalline, thick-bedded limestone, containing dark siliceous laminae, edgewise conglomerate beds, and fossil-fragment lenses; dolomite beds increase in number eastward.
Dark-gray, fine-grained intrusives; locally, mineralogy is altered and unit has greenish color.
White, coarsely crystalline; disseminated graphite flakes.
Thick-bedded, medium- to coarsely crystalline dolomite, in part oolitic, containing laminated limestone and sandstone interbeds.