Geologic units in Sussex county, New Jersey

Ramseyburg Member (Upper and Middle Ordovician) at surface, covers 21 % of this area

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

Bloomsburg Red Beds (Upper Silurian) at surface, covers 10 % of this area

(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).

Allentown Dolomite (Lower Ordovician and Upper Cambrian) at surface, covers 10 % of this area

(Wherry, 1909) - Very thin to very thick bedded dolomite containing minor orthoquartzite and shale. Upper part is medium-light- to medium-dark-gray, fine- to medium-grained, locally coarse-grained, medium- to very thick bedded dolomite. Floating quartz sand grains and two sequences of medium-light- to very light gray, thin-bedded quartzite and discontinuous, dark-gray chert lenses occur directly below upper contact. Rhythmically bedded lower dolomite beds alternate between light and dark gray weathering, medium and very light gray, fine and medium grained, and thin and medium bedded, which are interbedded with shaly dolomite. Ripple marks, crossbeds, edgewise conglomerate, mud cracks, oolites, and algal stromatolites occur throughout unit, but more typically in lower part. Shaly dolomite increases downward toward lower conformable contact with the Leithsville Formation. Oldest beds contain trilobite fauna of early Late Cambrian age; younger beds contain latest Cambrian fauna (Howell, 1945; Howell and others, 1950). Thickness about 580 m (1,900 ft).

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

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.

Bushkill Member (Middle Ordovician) at surface, covers 4 % of this area

(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.

Shawangunk Formation (Middle and Lower Silurian) at surface, covers 4 % of this area

(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).

Beekmantown Group, Lower Part (Lower Ordovician) at surface, covers 4 % of this area

(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.

Microcline Gneiss (Middle Proterozoic) at surface, covers 3 % of this area

Light-gray- to pinkish-white-weathering, tan to pinkish-white, fine- to medium-grained, well-layered gneiss composed principally of quartz, microcline, and lesser amounts of oligoclase. Common accessory minerals include biotite, garnet, magnetite, and, locally, sillimanite.

Pyroxene Granite (Middle Proterozoic) at surface, covers 3 % of this area

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.

High Point Member (Upper Ordovician) at surface, covers 3 % of this area

(Drake, 1991) - Medium-dark-gray, thin-bedded shale, siltstone and fine-grained sandstone, containing turbidite sequences Tbcde to Tcde of Bouma (1962). Interbedded with less abundant, light-yellowish-gray-weathering, medium-gray to medium-dark-gray, medium-grained, medium- to thick-bedded and massive, quartz- and calcareous-cemented quartz sandstone containing rip-ups of medium- to dark-gray shale and siltstone that commonly consist of Bouma (1962) turbidite sequences Tab to Ta. Restricted to northeast section of Martinsburg outcrop belt. Thermally metamorphosed near intrusive bodies. Grades along strike to the southwest into Ramseyburg Member by decrease in average grain size, absence of shale rip-ups, and lack of siliceous cement. Lower contact gradational and placed at base of lowermost thick-bedded graywacke or amalgamated graywacke containing shale rip-ups. Unit assigned to Orthograptus ruedemanni zone to Climacograptus spiniferus zone of Riva (1969, 1974) using graptolites collected by Parris and Cruikshank (1992). Thickness ranges from 0 to 1,370 m (0-4,500 ft).

Pyroxene Gneiss (Middle Proterozoic) at surface, covers 3 % of this area

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.

Hornblende Granite (Middle Proterozoic) at surface, covers 3 % of this area

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).

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

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.

Franklin Marble (Middle Proterozoic) at surface, covers 2 % of this area

White- to light-gray-weathering, white, grayish-white, or, less commonly pinkish-orange, coarse- to locally fine-crystalline calcite marble with accessory amounts of graphite, phlogopite, chondrodite, clinopyroxene, and serpentine. Contains pods and layers of clinopyroxene-garnet skarn, hornblende skarn, and clinopyroxene-rich rock. Thin layers of metaquartzite occur locally. Intruded by the Mount Eve Granite in the Pochuck Mountain area. Franklin Marble is host to the Franklin and Sterling Hill zinc ore bodies; exploited for talc and asbestiform minerals near Easton, Pennsylvania. Subdivided into an upper marble, "Wildcat marble," and a lower marble, "Franklin marble," by New Jersey Zinc Co. geologists (Hague and others, 1956).

Martinsburg Formation, undivided (Upper and Middle Ordovician) at surface, covers 2 % of this area

(Bayley and others, 1914) - Interbedded light-olive-gray, greenish-gray-, or dark-yellowish-brown- weathering, medium-dark- to dark-gray, laminated to medium-bedded graywacke and siltstone and olive-gray- to dark-yellowish-brown-weathering, medium-dark- to dark-gray slate. Turbidite cycles are common. Mapped only east of Lafayette and west of Lake Grinnell where thickness is at least 305 m (1000 ft).

Buttermilk Falls Limestone and Onondaga Limestones, undivided (Middle Devonian) at surface, covers 2 % of this area

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

Leithsville Formation (Middle and Lower Cambrian) at surface, covers 2 % of this area

(Wherry, 1909) - Thin- to thick-bedded dolomite containing subordinate siliciclastic rocks. Upper part is medium- to medium-dark-gray, fine- to medium-grained, pitted, friable, mottled and massive dolomite. Middle part is medium-gray, stylolitic, fine-grained, thin- to medium-bedded dolomite that is interbedded with shaly dolomite and, less commonly, vari-colored quartz sandstone, siltstone, and shale. Lower part is medium-gray, medium-grained, medium-bedded dolomite containing quartz-sand grains in stringers and lenses near the contact with the Hardyston Quartzite. Archaeocyathids of Early Cambrian age suggest an intraformational disconformity separating rocks of Middle and Early Cambrian age (Palmer and Rozanov, 1976). Thickness approximately 305 m (1,000 ft).

Hornblende Syenite (Middle Proterozoic) at surface, covers 2 % of this area

Tan- to buff-weathering, pinkish-gray or greenish-gray, medium- to coarse-grained, gneissoid syenite and lesser amounts of quartz syenite containing microcline microperthite, oligoclase, quartz, and hornblende. Some phases are monzonite or monzodiorite.

Pyroxene Syenite (Middle Proterozoic) at surface, covers 1 % of this area

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.

Syenite Gneiss (Middle Proterozoic) at surface, covers 1 % of this area

Light-pinkish-white- to buff-white-weathering, greenish-gray, medium-grained, moderately foliated rock consisting of two distinct phases: hornblende syenite gneiss containing microcline microperthite, oligoclase, hornblende, and opaque minerals; and pyroxene syenite gneiss containing microcline microperthite, oligoclase, clinopyroxene, accessory amounts of titanite, and opaque minerals. Despite the co-mingling of these two phases, they appear to belong respectively to the Byram and Lake Hopatcong Intrusive Suites. In Hamburg Mountain area.

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

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.

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

(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).

Poxono Island Formation (Upper Silurian) at surface, covers 1 % of this area

(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.

Beekmantown Group, Upper Part (Lower Ordovician) at surface, covers 1 % of this area

(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).

Biotite-quartz-oligoclase gneiss (Middle Proterozoic) at surface, covers 1 % of this area

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.

Clinopyroxene-Quartz-Feldspar Gneiss (Middle Proterozoic) at surface, covers 1.0 % of this area

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.

Marcellus Shale (Middle Devonian) at surface, covers 0.9 % of this area

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

Hornblende-Quartz-Feldspar Gneiss (Middle Proterozoic) at surface, covers 0.8 % of this area

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.

Jacksonburg Limestone (Middle Ordovician) at surface, covers 0.7 % of this area

(Kmmel, 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).

Schoharie Formation (Lower Devonian) at surface, covers 0.6 % of this area

(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).

Biotite-Quartz-Feldspar Gneiss (Middle Proterozoic) at surface, covers 0.5 % of this area

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.

Oriskany Group, undivided (Lower Devonian) at surface, covers 0.5 % of this area

(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).

Potassic Feldspar Gneiss (Middle Proterozoic) at surface, covers 0.4 % of this area

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.

Bossardville Limestone (Upper Silurian) at surface, covers 0.4 % of this area

(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.

Minisink Limestone and New Scotland Formation, undivided (Lower Devonian) at surface, covers 0.3 % of this area

Minisink Limestone (Epstein and others, 1967) - Light-medium-gray-weathering, medium-gray, fine-grained, medium-bedded, partly massive, argillaceous fossiliferous limestone. Some nodules and lenses of purer limestone occur locally. Lower contact gradational. Thickness uniformly 7 m (23 ft). New Scotland Formation (Clarke and Schuchert, 1899) - Upper part is dark-gray, very fine grained, laminated to thin-bedded siliceous shale containing pods of medium-dark-gray, very fine grained limestone; scattered thin beds and lenses of medium-gray, fine-grained argillaceous fossiliferous limestone; and small dark-gray chert nodules. Lower part is medium-dark-gray, thin-bedded, siliceous, fossiliferous calcareous shale. Contains thin beds and lenses of medium-gray, fine-grained, highly fossiliferous, argillaceous limestone containing nodules, lenses and, locally, irregular beds of dark-gray chert. Lower contact abrupt and placed at top of calcareous quartz sandstone. Total thickness is approximately 23 m (75 ft).

Coeymans Formation, Kalkberg Limestone, Coeymans Limestone, Manlius Limestone, undivided (Lower Devonian) at surface, covers 0.3 % of this area

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).

Port Ewen Shale (Lower Devonian) at surface, covers 0.3 % of this area

(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).

Rondout and Decker Formations, undivided (Lower Devonian and Upper Silurian) at surface, covers 0.3 % of this area

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.

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

(Wolff and Brooks, 1898) - Medium- to light-gray, fine- to coarse-grained, medium- to thick-bedded quartzite, arkosic sandstone and dolomitic sandstone. Basal pebble to cobble conglomerate typically contains clasts of local basement affinities. Contains fragments of the trilobite Olenellus thompsoni of Early Cambrian age. Thickness approximately 0.5 to 62 m (1.6-200 ft).

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

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.

Mount Eve Granite (Middle Proterozoic) at surface, covers 0.2 % of this area

(Drake and others, 1991a) - Light-pinkish-gray or grayish-tan-weathering, light-gray to pinkish-gray, medium- to coarse-grained granite containing microcline microperthite, quartz, oligoclase, and biotite. Common accessory minerals include hornblende, biotite, magnetite, and allanite. Most of the rock is a syenogranite. Upper intercept U-Pb age of 1,020ñ4 Ma (Drake and others, 1991a). Occurs in Pochuck Mountain area along New York boundary.

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

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.

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

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.

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

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.

Nepheline syenite (Early Silurian? and Late Ordovician) at surface, covers < 0.1 % of this area

Medium- to dark-gray, medium- to coarse-grained, alkalic to alkalic-calcic nepheline syenite. Composed principally of nepheline, orthoclase, biotite, and clinopyroxene, and accessory minerals are magnetite, apatite, titanite, zircon, and pyrite. Restricted to two small bodies northwest of Beemerville. Intrudes the Martinsburg Formation, but appears to be unconformably overlain by the Shawangunk Formation. K-Ar and Rb-Sr ages of 435ñ20 Ma from biotite (Zartman and others, 1967) and a fission track date from titanite of 422ñ14 Ma (Eby and others, 1992) suggest emplacement in Late Ordovician to Early Silurian.

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

(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).

Ouachitite breccia (Early Silurian? and Late Ordovician) at surface, covers < 0.1 % of this area

Medium-dark-gray, fine-grained ouachitite (olivine-free biotite lamprophyre) containing pebble- to cobble-size xenoliths of Middle Proterozoic rock, dolomite of the Kittatinny Supergroup(?), the Martinsburg Formation, and autoliths of potassic syenite, lamprophyre, and carbonatite. Found in numerous diatremes in the Beemerville area; largest of at Rutan Hill.

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

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

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

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.

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

Seneca, Morehouse (cherty), and Nedrow Limestone Members, Edgecliff cherty Limestone Member, local bioherms, Buttermilk Falls Limestone Member; Schoharie Formation-shale, limestone; Carlisle Center Siltstone; Esopus Shale.

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

Black shale; sparse marine fauna and siderite concretions. Contains local limestone (""Purcell"") member. Tioga bentonite included at base in eastern Pennsylvania.

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

Alsen, Becraft, New Scotland, Kalkberg, Coeymans, and Manlius Limestones.

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

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.