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Geologic units in Hunterdon county, New Jersey

Potassic Feldspar Gneiss (Middle Proterozoic) at surface, covers 0.2 % of this area

Potassic Feldspar Gneiss - Light-gray- to pinkish-buff-weathering, pinkish-white to light-pinkish-gray, fine- to medium-grained, moderately foliated gneiss and lesser amounts of granofels composed of quartz, microcline, microcline microperthite and local accessory amounts of biotite, garnet, sillimanite, and opaque minerals.

Lithology: paragneiss; granofels

Quartz-Oligoclase Gneiss (Middle Proterozoic) at surface, covers 5 % 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

Microperthite Alaskite (Middle Proterozoic) at surface, covers 2 % 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

Biotite-quartz-oligoclase gneiss (Middle Proterozoic) at surface, covers 0.2 % of this area

Biotite-quartz-oligoclase gneiss - White- to light-gray-weathering, light- to medium-gray or greenish-gray, fine- to coarse-grained, massive to moderately well layered, foliated gneiss composed of oligoclase or andesine, quartz, biotite, and, locally, garnet. Commonly interlayered with amphibolite.

Lithology: gneiss; amphibolite

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

Chestnut Hill Formation (Late Proterozoic) at surface, covers < 0.1 % of this area

Chestnut Hill Formation (Drake, 1984) - Interbedded arkose, ferruginous quartzite, quartzite conglomerate, metarhyolite, and metasaprolite. Confined to a few small areas north and east of Phillipsburg, on the western side of Bowling Green Mountain, northwest of High Bridge, and a few areas too small to show at this map scale.

Lithology: arkose; quartzite; conglomerate; meta-rhyolite

Orange Mountain Basalt (Lower Jurassic) at surface, covers 0.2 % of this area

Orange Mountain Basalt - Basalt, fine-grained to aphanitic, dark-greenish-gray, composed mostly of calcic plagioclase and augite; crystals smaller than 1 mm (0.04 in). Unit consists of three major tholeiitic lava-flow sequences, each about 80 m (262 ft) thick. Lowest flow is generally massive with widely spaced curvilinear joints; middle flow is massive or has columnar joints; lower part of uppermost flow has pillow structures and upper part has pahoehoe flow structures. Thickness in map area is about 160 m (525 ft).

Lithology: basalt

Pyroxene Alaskite (Middle Proterozoic) at surface, covers 0.6 % of this area

Pyroxene Alaskite - Light-gray- or tan-weathering, greenish-buff to light-pinkish-gray, medium- to coarse-grained, massive, moderately foliated granite composed of mesoperthite to microantiperthite, oligoclase, and quartz. Common accessory minerals are clinopyroxene, titanite and magnetite. Locally includes small bodies of amphibolite not shown on map.

Lithology: granite; amphibolite

Hardyston Quartzite (Lower Cambrian) at surface, covers 0.3 % 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

Microantiperthite Alaskite (Middle Proterozoic) at surface, covers 0.3 % of this area

Microantiperthite Alaskite - White-weathering, locally rusty, light-greenish-gray medium- to coarse-grained, gneissic granite and alaskite containing microantiperthite, quartz, oligoclase, and sparse amounts of hornblende, clinopyroxene, biotite, and magnetite.

Lithology: granite

Beekmantown Group, Upper Part (Lower Ordovician) at surface, covers 0.2 % 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

Passaic Formation Limestone-clast Conglomerate facies (Lower Jurassic and Upper Triassic) at surface, covers 0.8 % 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

Pyroxene Syenite (Middle Proterozoic) at surface, covers 0.3 % of this area

Pyroxene Syenite - Gray- to buff- or tan-weathering, greenish-gray, medium- to coarse-grained, massive, indistinctly foliated syenite composed of mesoperthite to microantiperthite, oligoclase and clinopyroxene. Contains sparse amounts of quartz, titanite, magnetite, and trace amounts of pyrite.

Lithology: syenite

Hypersthene-Quartz-Oligoclase Gneiss (Middle Proterozoic) at surface, covers 0.9 % 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

Stockton Formation Cobble Conglomerate and Sandstone facies (Upper Triassic) at surface, covers 0.8 % 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

Lockatong Formation red bed (Upper Triassic) at surface, covers 2 % of this area

Lockatong Formation red bed - 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

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

Epidote Gneiss - Light-gray- to pinkish-white-weathering, light-grayish-pink to pinkish-white, medium-grained, moderately layered and foliated gneiss containing quartz, microcline, and epidote. Some phases contain scapolite. May be interlayered with and related to potassium-feldspar gneiss (Yk), and (or) clinopyroxene-quartz-feldspar gneiss (Ymp). Two elongate bodies mapped east of Franklin.

Lithology: paragneiss

Biotite-Quartz-Feldspar Gneiss (Middle Proterozoic) at surface, covers 1 % of this area

Biotite-Quartz-Feldspar Gneiss - Gray-weathering, locally rusty, gray to tan or greenish-gray, fine- to medium-coarse-grained, moderately layered and foliated gneiss that is variable in texture and composition. Composed of oligoclase, microcline microperthite, quartz, and biotite. Locally contains garnet, graphite, sillimanite, and opaque minerals.

Lithology: paragneiss

Diabase (Jurassic) at surface, covers 3 % 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

Preakness Basalt (Lower Jurassic) at surface, covers < 0.1 % of this area

Preakness Basalt - Basalt, coarse-crystalline, very dark greenish gray to black. Texture is subophitic; plagioclase and augite crystals are nearly equal in size; no fine-grained groundmass. Plagioclase (An55-60) is subhedral, mostly 0.2 to 0.3 mm (0.008-0.012 in) long, with a few crystals up to 2 mm (0.08 in) long. Clinopyroxene and orthopyroxene grains are equant, mostly anhedral, 0.3 mm (0.012 in) average diameter. Iron-titanium oxides are mostly interstitial, 0.2 to 0.5 mm (0.008-0.02 in) in diameter. Thickness of unit is unknown in Sand Brook syncline.

Lithology: basalt

Diorite (Middle Proterozoic) at surface, covers 0.8 % of this area

Diorite - Gray- to tan-weathering, greenish-gray to brownish-gray, medium- to coarse-grained, greasy-lustered, massive diorite containing andesine or oligoclase, clinopyroxene, hornblende, hypersthene, and sparse amounts of biotite and magnetite. Amphibolite layers common.

Lithology: diorite; amphibolite

Stockton Formation Cobble Conglomerate and Sandstone facies (Upper Triassic) at surface, covers 1.0 % of this area

Stockton Formation Cobble Conglomerate and Sandstone facies - Unit is coarser near Newark basin border fault, where poorly exposed, reddish-brown to pinkish-white, medium- to coarse-grained, feldspathic pebbly sandstone and conglomerate (Trss) and pebble to cobble quartzite conglomerate (Trscq).

Lithology: sandstone; conglomerate

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

Hornblende-Quartz-Feldspar Gneiss - Pinkish-gray- to buff-weathering, light- pinkish-white to pinkish-gray, fine- to medium-grained, massive to moderately well layered gneiss containing microcline, quartz, oligoclase, hornblende, and magnetite. Locally contains garnet and biotite.

Lithology: paragneiss

Hornblende Granite (Middle Proterozoic) at surface, covers 6 % of this area

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

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

Granophyre (Early Jurassic) at surface, covers 0.1 % of this area

Granophyre - Fine-grained to aphanitic dikes; medium- to coarsegrained, subophitic discordant stock-like intrusions of dark-greenish-gray to black diabase; and plugs of dark gray, concordant to discordant sheetlike, medium- to coarse-grained, quartz-rich to albite-rich granophyre (map unit Jg). The chilled margins of diabase masses are aphanitic to very fine grained. Diabase is dense, hard, and sparsely fractured. It is composed mostly of plagioclase (An50-70), clinopyroxene (mostly augite) and magnetite +/- ilmenite. Accessory minerals include apatite, quartz, alkali feldspar, hornblende, titantite, and zirocon. Olivine is rare. Within about 200 m (655 ft) above and 150 m (490 ft) below the large diabase sheets, red mudstones are typically metamorphosed into indurated, bluish-gray hornfels commonly with clots or crystals of tourmaline or cordierite, whereas argillitic siltstone is metamorphosed into brittle, black, very fine grained hornfels, Sheetlike intrusions are as much as 360 to 400 m (1,180-1,310 ft) thick. Dikes range in thickness from 3 to 15 m (10-50 ft) and several kilometers (miles) long. Thickness of the stocklike bodies is unknown.

Lithology: granitoid

Stockton Formation (Upper Triassic) at surface, covers 5 % 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

Migmatite (Middle Proterozoic) at surface, covers 0.8 % of this area

Migmatite - Mixed rock consisting of amphibolite containing veins, lenses, layers, and irregular clots of albite-oligoclase granite or microperthite alaskite.

Lithology: migmatite

Pyroxene Granite (Middle Proterozoic) at surface, covers 2 % of this area

Pyroxene Granite - Gray- to buff- or white-weathering, greenish-gray, medium- to coarse-grained, massive, gneissoid to indistinctly foliated granite containing mesoperthite to microantiperthite, quartz, oligoclase, and clinopyroxene. Common accessory minerals include titanite, magnetite, apatite, and trace amounts of pyrite. Some phases are monzonite, quartz monzodiorite, or granodiorite. Locally includes small bodies of amphibolite not shown on map.

Lithology: granite; monzonite; quartz monzodiorite; granodiorite; amphibolite

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)

Trenton Gravel (Quaternary) at surface, covers < 0.1 % 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

Beekmantown Group, Lower Part (Lower Ordovician) at surface, covers 0.7 % 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

Lockatong Formation - Sandstone and Conglomerate facies (Upper Triassic) at surface, covers 0.9 % of this area

Sandstone and Conglomerate Sandstone facies - Unit Trla interfingers laterally and gradationally with quartz sandstone and conglomerate (Trls) and quartzite conglomerate (Trlcq) near Triassic border fault in southwestern area of map.

Lithology: sandstone; conglomerate

Passaic Formation gray bed (Lower Jurassic and Upper Triassic) at surface, covers 3 % 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

Passaic Formation (Lower Jurassic and Upper Triassic) at surface, covers 34 % of this area

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

Lithology: siltstone; sandstone; shale

Lockatong Formation (Upper Triassic) at surface, covers 11 % 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

Amphibolite (Middle Proterozoic) at surface, covers 2 % 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

Jutland Klippe Sequence, undifferentiated (Middle Ordovician to Upper Cambrian?) at surface, covers < 0.1 % of this area

Jutland Klippe Sequence, undifferentiated - Rocks of the Jutland klippe sequence occur in six isolated fragments of the Jutland klippe east of Jutland and two fragments of the Peapack klippe along the Peapack-Ralston fault in the New Jersey Highlands hinterland. The sequence is largely varicolored shale and sandstone, but contains lesser amounts of limestone, dolomite and pebble conglomerate. Lash and Drake (1984) correlate this sequence with the accretionary prism deposits of the Greenwich slice of the Hamburg klippe in eastern Pennsylvania. Rocks of the Jutland klippe sequence were folded and thrust over rocks of the Kittatinny Valley sequence during the Taconic orogeny and then were deformed during the Alleghanian orogeny and again during Mesozoic rifting of eastern North America.

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

Pyroxene Gneiss (Middle Proterozoic) at surface, covers 0.6 % of this area

Pyroxene Gneiss - White- to tan-weathering, greenish-gray, fine- to medium-grained, well-layered gneiss containing oligoclase, clinopyroxene, variable amounts of quartz, and trace amounts of opaque minerals and titanite. Some phases contain scapolite and calcite. Commonly interlayered with pyroxene amphibolite or marble.

Lithology: paragneiss; amphibolite; marble

Passaic Formation Quatzite-clast Conglomerate facies (Lower Jurassic and Upper Triassic) at surface, covers 4 % 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

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

Biotite Granite - Pink- to buff-weathering, light-pinkish-gray, medium-grained, massive, moderately foliated granite composed of microcline microperthite, quartz, oligoclase, and biotite.

Lithology: granite

Lockatong Formation - Conglomerate facies (Upper Triassic) at surface, covers 1 % of this area

Lockatong Formation Sandstone and Conglomerate Sandstone facies - Unit Trla interfingers laterally and gradationally with quartz sandstone and conglomerate (Trls) and quartzite conglomerate (Trlcq) near Triassic border fault in southwestern area of map.

Lithology: conglomerate; sandstone

Jutland Klippe Sequence Unit A (lower Middle Ordovician to Upper Cambrian) at surface, covers 1 % of this area

Jutland Klippe Sequence Unit A of Perissoratis and others (1979) - Interbedded red, green, and tan shale, sandstone, and dark-gray, aphanitic to fine-grained limestone, which contains floating quartz-sand grains. Grades downward through interbedded sequence of red, green and brown shale to medium-gray to brown, fine- to coarse-grained sandstone and quartz-pebble conglomerate. Lower beds are dark-gray shale and siltstone containing minor dark-gray, aphanitic to fine-grained, medium-bedded limestone. Lower contact is a fault. Contains graptolites in the span of Anisograptus to Isograptus caduceus of Berry (1968) (Perissoratis and others, 1979) and conodonts of the Cordylodus proavus to Paroistodus proteus faunas of the North Atlantic Realm. Thickness is unknown.

Lithology: shale; sandstone; limestone; conglomerate; siltstone

Feltville Formation (Lower Jurassic) at surface, covers 0.3 % of this area

Feltville Formation - Mostly fine-grained, feldspathic sandstone, coarse siltstone, and silty mudstone, brownish-red to light-grayish-red. Fine-grained sandstone is moderately well sorted, cross laminated, and contains 15 percent or more feldspar; interbedded with mudstone, indistinctly laminated, bioturbated, and calcareous in places. A thin bed (0-2 m (0-7 ft) thick) of black, microlaminated carbonaceous limestone and gray calcareous mudstone occurs near the base and contains fish and plant fossils, and thermally mature hydrocarbons. Thickness of unit in the Sand Brook syncline is about 155 m (509 ft).

Lithology: siltstone; sandstone; fine-grained mixed clastic; mudstone; limestone

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

Clinopyroxene-Quartz-Feldspar Gneiss - Pinkish-gray- or pinkish-buff-weathering, white to pale-pinkish-white or light-gray, fine- to medium-grained, massive to moderately well-layered gneiss composed of microcline, quartz, oligoclase, clinopyroxene, and trace amounts of epidote, biotite, titanite, and opaque minerals. Commonly interlayered with amphibolite or pyroxene amphibolite.

Lithology: paragneiss; amphibolite

Leithsville Formation (Middle and Lower Cambrian) at surface, covers 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

Allentown Dolomite (Lower Ordovician and Upper Cambrian) (Wherry, 1909) (Lower Ordovician and Upper Cambrian) at surface, covers 2 % 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

Wantage Sequence (Middle Ordovician) at surface, covers < 0.1 % of this area

Wantage Sequence (Monteverde and Herman, 1989) - Restricted, discontinuous sequence of interbedded limestone, dolomite, conglomerate, siltstone, and shale. Upper part is medium-yellowish-brown- to olive-gray-weathering, medium- to dark-gray, very fine to fine-grained, laminated to massive limestone and dolomite that grade down into underlying clastic rocks of lower part. Upper part locally absent. Lower part ranges from grayish-red, medium-gray, pale-brown, and greenish-gray to pale-green mudstone and siltstone containing disseminated subangular to subrounded chert-gravel, quartz-sand lenses, and chert-pebble conglomerate. Lower contact unconformable. Thickness ranges from 0 to 46 m (0-150 ft).

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

Jutland Klippe Sequence Unit B (Middle Ordovician) at surface, covers 0.4 % of this area

Jutland Klippe Sequence Unit B of Perissoratis and others (1979) - Heterogeneous sequence of interbedded red, green, tan and gray shale; interlaminated dolomite and shale; interbedded fine-grained graywacke siltstone and beds or lenses of sandstone; light-gray to pale-pinkish-gray quartzite; and interbedded fine-grained, thin-bedded limestone and red and green shale. Limestone locally resembles an intraformational conglomerate because it is disrupted, boudinaged, and surrounded by shale beds. Lower contact gradational and within interbedded sequence of thin- to medium-bedded sandstone, siltstone, and limestone. Perissoratis and others (1979) placed this contact at boundary between graptolite faunas Isograptus caduceus and Paraglossograptus etheridgei of Berry (1968). The youngest graptolites occur within Climacograptus bicornis zone of Berry (1968). Some shale beds contain conodonts (Ethington and others, 1958; Karklins and Repetski, 1989) and brachiopod fragments. Carbonate and pelitic rocks locally contain conodonts of Prioniodus triangularis to Pygodus anserinus faunas of North Atlantic Realm. Thickness varies due to structural complexity, but may be about 460 to 550 m (1,500-1,800 ft).

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

Passaic Formation Conglomerate and Sandstone facies (Lower Jurassic and Upper Triassic) at surface, covers 2 % 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

Albite-Oligoclase Granite (Middle Proterozoic) at surface, covers 0.2 % 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