USGS Home
Contact USGS
Search USGS

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

Geologic units in Berkshire county, Massachusetts

Stockbridge Formation (Lower Cambrian) at surface, covers 11 % of this area

Stockbridge Formation - Massive to finely laminated steel-gray calcitic dolomite marble containing a prominent zone of white quartz nodules near top.

Lithology: marble

Nassau Formation (Lower Cambrian and Proterozoic Z) at surface, covers < 0.1 % of this area

Nassau Formation - Rensselaer Graywacke Member - Greenish-gray, plagioclase-rich, blue quartz pebble metagraywacke and minor gneiss-cobble conglomerate.

Lithology: metasedimentary rock; conglomerate

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

Stockbridge Formation - Blue and gray mottled limestone and calcite marble and beds of beige dolostone.

Lithology: limestone; marble; dolostone (dolomite)

Hoosac Formation (Lower Cambrian and Proterozoic Z) at surface, covers 0.7 % of this area

Hoosac Formation - Green to gray-green chlorite-sericite-quartz phyllite; interbeds of chloritoid- or albite-rich schist and minor quartzite, locally rich in garnet and kyanite.

Lithology: phyllite; schist; quartzite

Unit b [of Stockbridge Marble] (Upper and Middle? Cambrian) at surface, covers < 0.1 % of this area

Unit b [of Stockbridge Marble] - White, pink, cream, and light-gray, generally well bedded dolomitic marble interlayered with phyllite and schist and with siltstone, sandstone, or quartzite, commonly dolomitic.

Lithology: marble; phyllite; schist; siltstone; sandstone; quartzite

Gray, well-layered biotite-plagioclase-quartz gneiss (Proterozoic Y) at surface, covers 8 % of this area

Gray, well-layered biotite-plagioclase-quartz gneiss - Containing beds of amphibolite, aluminous schist, quartzite, and calc-silicate gneiss.

Lithology: granitic gneiss; amphibolite; schist; quartzite; gneiss

Hoosac Formation (Lower Cambrian and Proterozoic Z) at surface, covers 0.6 % of this area

Hoosac Formation - Greenish chlorite-albite-magnetite-sericite-quartz schist and granofels.

Lithology: mica schist; granofels

Stamford Granite Gneiss (Proterozoic Y) at surface, covers 0.3 % of this area

Stamford Granite Gneiss - White to gray biotite-oligoclase-microcline Rapakivi granite gneiss containing blue quartz. Intrudes Yb, Ybu.

Lithology: granitic gneiss

Stockbridge Formation (Lower Cambrian) at surface, covers 6 % of this area

Stockbridge Formation - Beige, tan, and dark-gray weathering quartzose dolomite marble containing interbeds of black, green and maroon phyllite and punky weathering blue quartz pebble quartzite.

Lithology: marble; phyllite; quartzite

Nassau Formation (Lower Cambrian and Proterozoic Z) at surface, covers < 0.1 % of this area

Nassau Formation- Greenish-gray albitic phyllite.

Lithology: phyllite

Dalton Formation (Lower Cambrian and Proterozoic Z) at surface, covers 0.6 % of this area

Dalton Formation - White to yellowish-gray weathering, flaggy quartzite interbedded in feldspathic quartzite.

Lithology: quartzite

Well-layered hornblende-biotite gneiss (Proterozoic Y) at surface, covers 0.4 % of this area

Well-layered hornblende-biotite gneiss .

Lithology: mafic gneiss

Canaan Mountain Formation (Lower Ordovician and Proterozoic Z) at surface, covers 0.3 % of this area

Canaan Mountain Formation - Rusty-weathering, coarse garnet schist and feldspathic schist.

Lithology: schist

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

Walloomsac Formation - Orange-brown weathering, graphite-albite-biotite calcitic marble and schistose marble and interbedded black phyllite.

Lithology: marble; phyllite

Everett Schist (Cambrian?) at surface, covers < 0.1 % of this area

Everett Schist - minor meta-graywacke lenses. Includes Greylock Schist in Massachusetts.

Lithology: schist; metasedimentary rock

Black and white, well-layered hornblende-biotite-plagioclase gneiss and amphibolite (Proterozoic Y) at surface, covers 0.4 % of this area

Black and white, well-layered hornblende-biotite-plagioclase gneiss and amphibolite - Contains irregular pods of diopside or cummingtonite-talc rock or amphibole calc-silicate, epidote-layered quartz-plagioclase gneiss near Hinsdale.

Lithology: mafic gneiss; amphibolite; gneiss; metamorphic rock; calc-silicate rock

Rowe Schist (Lower Ordovician and Cambrian) at surface, covers 0.6 % of this area

Rowe Schist - Gray to black, fine-grained , slightly rusty, moderately carbonaceous schist; minor fine- to medium-grained dark-gray to white quartzite. Minor lenses of rock identical to OCAr.

Lithology: schist; quartzite

Greylock Schist (Lower Cambrian and Proterozoic Z) at surface, covers 0.5 % of this area

Greylock Schist - Light-green to gray, white albite-spotted phyllite and interbedded blue-quartz metagraywacke, salmon-pink dolostone, and blue-quartz conglomerate. Minor interbeds of black and white albite-spotted phyllite resembles Hoosac (CAZhga).

Lithology: phyllite; metasedimentary rock; dolostone (dolomite); conglomerate; quartzite

Dalton Formation (Lower Cambrian and Proterozoic Z) at surface, covers 0.7 % of this area

Dalton Formation - Black to dark-gray carbonaceous quartz schist.

Lithology: schist

Moretown Formation (Middle Ordovician or older) at surface, covers 2 % of this area

Moretown Formation - Light-greenish-gray to buff, fine-grained, pinstriped granofels and schist.

Lithology: granofels; schist

Nassau Formation (Lower Cambrian and Proterozoic Z) at surface, covers 3 % of this area

Nassau Formation - Lustrous, soft green, yellowish-green and purple laminated chloritoid-chlorite phyllite (Mettawee Member).

Lithology: phyllite

Unit c [of Stockbridge Marble] (Upper Cambrian) at surface, covers < 0.1 % of this area

Unit c [of Stockbridge Marble] - Gray, generally massive dolomite marble, commonly contains quartz grains, locally beds of sandstone; may be calcitic near top.

Lithology: marble; sandstone

Units e and d [of Stockbridge Marble] (Lower Ordovician) at surface, covers < 0.1 % of this area

Units e and d [of Stockbridge Marble] - White to gray massive calcite marble, commonly mottled with dolomite and locally interlayered with dolomite marble and calcareous siltstone and sandstone.

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

Biotite-hornblende mafic dikes (Proterozoic Z) at surface, covers < 0.1 % of this area

Biotite-hornblende mafic dikes - Locally with relict subophitic texture. Intrudes Yw and Ygg.

Lithology: diorite

Everett Formation (Lower Cambrian and Proterozoic Z) at surface, covers 2 % of this area

Everett Formation - Light-green and greenish-gray chlorite-muscovite-albite or chloritoid-rich phyllite. Predominantly dark-gray chloritoid-rich schist in Lenox Mountain.

Lithology: phyllite; schist

Hoosac Formation (Lower Cambrian and Proterozoic Z) at surface, covers < 0.1 % of this area

Hoosac Formation - Light-gray to tan, albite-muscovite-calcite spangled schist.

Lithology: schist

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

Walloomsac Formation - Tan to dark-blue-gray laminated quartzite and calcareous quartzite previously mapped as Bellowspipe Quartzite.

Lithology: quartzite

Cheshire Quartzite (Lower Cambrian) at surface, covers 2 % of this area

Cheshire Quartzite - White, massive vitreous quartzite.

Lithology: quartzite

Greylock Schist (Lower Cambrian and Proterozoic Z) at surface, covers 1 % of this area

Greylock Schist - Soft, lustrous green phyllite with minor beds of green quartzite and well laminated gray dolomitic phyllite; resembles Hoosac (CAZhg) and Nassau (CAZnp).

Lithology: phyllite; quartzite

White to gray and black-spotted muscovite-biotite granite and granodiorite (Ordovician) at surface, covers 0.2 % of this area

White to gray and black-spotted muscovite-biotite granite and granodiorite - Intruded near or along thrust faults. Intrudes CAZh and Proterozoic Y gneisses.

Lithology: granite; granodiorite

Nassau Formation (Lower Cambrian and Proterozoic Z) at surface, covers 0.2 % of this area

Nassau Formation - Dark-gray to black chloritoid-rich phyllite.

Lithology: phyllite

Washington Gneiss (Proterozoic Y) at surface, covers 8 % of this area

Washington Gneiss - Rusty-weathering, muscovite-biotite-sillimanite and/or kyanite-garnet schist; blue-quartz ribbed conglomerate, interlayered garnet-plagioclase-quartz metadacite.

Lithology: mica schist; conglomerate; felsic metavolcanic rock

Everett Schist (Cambrian?) at surface, covers < 0.1 % of this area

Everett Schist - Grayish to greenish (some rusty-weathering), fine- to medium-grained, foliated but poorly layered schist or phyllite, composed of quartz, albite or oligoclase, muscovite, garnet, staurolite or chloritoid, and generally chlorite. Local layers are dark-gray to silvery schist or phyllite.

Lithology: schist; phyllite

Serpentinized peridotite stocks (Ordovician to Proterozoic Z) at surface, covers < 0.1 % of this area

Serpentinized peridotite stocks - Intrudes Yw and Ygg.

Lithology: serpentinite; peridotite

Granitoid Gneiss (Proterozoic Y) at surface, covers 2 % of this area

Granitoid gneiss - Biotite ferrohastingsite granodioritic and granitic gneiss with large schlieren of biotite, locally contains garnet and muscovite.

Lithology: granitic gneiss

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

Stockbridge Formation - Tan-beige weathering quartzose calcite and dolomite marble; minor cross-laminated quartzite.

Lithology: marble; quartzite

Washington Gneiss (Proterozoic Y) at surface, covers 3 % of this area

Washington Gneiss - Well-layered, rusty-tan weathering muscovite-biotite plagioclase-microcline-quartz granofels containing layers of rusty sulfidic calc-silicate rocks.

Lithology: granofels; calc-silicate rock

Washington Gneiss (Proterozoic Y) at surface, covers 0.2 % of this area

Washington Gneiss - Coarse- to medium-grained hornblende-garnet amphibolite, hornblende-plagioclase gneiss and phlogopite-hornblende-plagioclase amphibolite (metabasalt).

Lithology: amphibolite; mafic gneiss; meta-basalt

Hoosac Formation (Lower Cambrian and Proterozoic Z) at surface, covers 3 % of this area

Hoosac Formation - Undifferentiated Hoosac Formation.

Lithology: schist; phyllite; gneiss; amphibolite; quartzite; granofels; calc-silicate rock

Stockbridge Formation (Lower Cambrian) at surface, covers 3 % of this area

Stockbridge Formation - White to light-powdery-blue-gray dolostone with disseminated grains of quartz and prominent sprays of tremolite in higher-grade areas.

Lithology: dolostone (dolomite)

Serpentinite and/or talc rock (Precambrian to Phanerozoic) at surface, covers < 0.1 % of this area

Serpentinite and/or talc rock - Interpreted as tectonic slivers.

Lithology: serpentinite

Dalton Formation (Lower Cambrian and Proterozoic Z) at surface, covers 0.9 % of this area

Dalton Formation - Orangish-gray, gray, and light-greenish-gray muscovite-quartz schist and interlayered feldspathic quartzite and quartz conglomerate; minor beds of rusty albitic schist.

Lithology: mica schist; quartzite; conglomerate; schist

Tyringham Gneiss (Proterozoic Y) at surface, covers 8 % of this area

Tyringham Gneiss - Light pinkish-gray ferrohastingsite-biotite, quartz-rodded granodioritic to quartz monzonitic gneiss, coarsely porphyritic, locally having fine-grained aplitic border. Intrudes all Berkshire Proterozoic Y units.

Lithology: granitic gneiss

Walloomsac Formation (Middle Ordovician) at surface, covers 8 % of this area

Walloomsac Formation - Dark-gray, graphitic quartz phyllite and schist containing minor lenses of limestone.

Lithology: phyllite; schist; limestone

Stockbridge Formation (Lower Ordovician) at surface, covers 9 % of this area

Stockbridge Formation - White to blue-gray and white layered calcite marble.

Lithology: marble

Diorite at Goff Ledges (Ordovician) at surface, covers < 0.1 % of this area

Diorite at Goff Ledges - Diorite at Goff Ledges (Ogd) and similar diorite (Od) in the Windsor quadrangle. Very coarse-grained to pegmatitic, slightly foliated hornblende-plagioclase diorite, minor hornblende pyroxenite. Ogd intrudes CAZh and CAZhk. Od intrudes the Rowe Schist of the Rowe-Hawley zone.

Lithology: diorite; pyroxenite

Everett Formation (Lower Cambrian and Proterozoic Z) at surface, covers < 0.1 % of this area

Everett Formation - Olive-gray to green, blue-quartz pebble metagraywacke and quartzite.

Lithology: metasedimentary rock; quartzite

Hoosac Formation (Lower Cambrian and Proterozoic Z) at surface, covers < 0.1 % of this area

Hoosac Formation - Gray conglomerate containing pebbles of albite and blue quartz, and boulders of gneiss.

Lithology: conglomerate

Stockbridge Formation (Cambrian - Lower Ordovician) at surface, covers < 0.1 % of this area

Stockbridge Formation - calcitic and dolomitic marble.

Lithology: marble

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

Walloomsac Formation - slate, phyllite, schist, metagraywacke.

Lithology: slate; phyllite; schist; metasedimentary rock

New Haven Arkose (Upper Triassic) at surface, covers < 0.1 % of this area

New Haven Arkose - Red, pink, and gray coarse-grained, locally conglomeratic arkose interbedded with brick-red shaley siltstone and fine-grained arkosic sandstone; boundary between Lower Jurassic (Jn) and Upper Triassic (TRn) parts is arbitrarily drawn through clastic rocks of similar lithology below gray mudstone containing Lower Jurassic palynofloral zone; TRn is continuous with and lithically similar to TRs near Northampton. Assigned to Newark Supergroup (Robinson and Luttrell, 1985).

Lithology: arkose; siltstone; mudstone

Dalton Formation (Lower Cambrian and Proterozoic Z) at surface, covers 0.7 % of this area

Dalton Formation - Tan to orangish-tan quartz and gneiss cobble and pebble conglomerate, rusty feldspathic schist, and lustrous greenish-gray muscovite quartz schist.

Lithology: conglomerate; schist; mica schist

Hoosac Formation (Lower Cambrian and Proterozoic Z) at surface, covers 0.2 % of this area

Hoosac Formation - Rusty-brown to dark-gray, albite-spotted muscovite-biotite schist or gneiss, with interlayered black garnet-biotite-albite-quartz schist near base; interfingers with Dalton Formation.

Lithology: mica schist; gneiss; schist

Moretown Formation (Middle Ordovician or older) at surface, covers 0.2 % of this area

Moretown Formation - Green to dark-green greenstone or amphibolite.

Lithology: greenstone; amphibolite

Pinkish-gray, fine-grained, well-laminated felsic biotite-microcline-plagioclase-quartz gneiss (Proterozoic Y) at surface, covers 1 % of this area

Pinkish-gray, fine-grained, well-laminated felsic biotite-microcline-plagioclase-quartz gneiss - Probably metamorphosed rhyolite.

Lithology: felsic gneiss

Lee Gneiss (Proterozoic Y) at surface, covers 1 % of this area

Lee Gneiss - Hornblende-spotted plagioclase-hornblende-quartz gneiss and granofels and well-layered biotite-hornblende-plagioclase-quartz gneiss containing knots of diopside or epidote.

Lithology: mafic gneiss; granofels

White, magnetite-bearing alaskite and trondhjemite (Ordovician) at surface, covers < 0.1 % of this area

White, magnetite-bearing alaskite and trondhjemite - Associated with blastomylonite along thrust slices. Intrudes Proterozoic Y gneisses.

Lithology: alkali-granite (alaskite); trondhjemite

Austerlitz Phyllite (Cambrian?) at surface, covers 0.2 % of this area

Austerlitz Phyllite - minor quartzite

Lithology: phyllite; quartzite

Nassau Formation (Lower Cambrian and Proterozoic Z) at surface, covers < 0.1 % of this area

Nassau Formation - Dark-green to greenish brown, massive to well foliated stilpnomelane-chlorite-oligoclase-epidote metabasalt and basaltic tuff.

Lithology: meta-basalt; tuff

Tectonic breccia (Ordovician) at surface, covers 0.1 % of this area

Tectonic breccia - Consisting of completely mixed phyllites of Walloomsac Formation Taconic allochthon.

Lithology: tectonic breccia; phyllite

Nassau Formation (Lower Cambrian and Proterozoic Z) at surface, covers 2 % of this area

Nassau Formation - Gray to dark-greenish-gray, siliceous phyllite with abundant beds of quartzite, olive-gray metasiltstone and subgraywacke (includes Bomoseen Graywacke Member and Zion Hill quartzite Member).

Lithology: phyllite; quartzite; meta-argillite; graywacke

Rowe Schist (Lower Ordovician and Cambrian) at surface, covers 2 % of this area

Rowe Schist - Light-green to light-bluish-gray schist having thin granular quartz lenses and lamellae. Kyanite and staurolite typical at higher grades.

Lithology: schist

Calc-silicate granofels and gneiss (Proterozoic Y) at surface, covers 0.9 % of this area

Calc-silicate granofels and gneiss - Including calcitic or dolomitic chondrodite-diopside marble, coarse hornblende-plagioclase-diopside and diopside rock, locally containing beds of lustrous muscovite-kyanite sillimanite-garnet schist.

Lithology: granofels; gneiss; marble; metamorphic rock; schist

Hatch Hill Formation (Upper Cambrian) at surface, covers 0.3 % of this area

Hatch Hill Formation - Bluish-gray weathering black sulfidic slate and chert.

Lithology: slate; chert

Washington Gneiss (Proterozoic Y) at surface, covers 0.1 % of this area

Washington Gneiss - Rusty-weathering diopside and sulfidic -rich calcite marble and calc-silicate rock.

Lithology: marble; calc-silicate rock

Rowe Schist (Lower Ordovician and Cambrian) at surface, covers < 0.1 % of this area

Rowe Schist - Fine- to medium-grained, well-layered and foliated amphibolite; epidote-rich layers locally abundant. Includes its typical Chester Amphibolite Member at Chester, Massachusetts.

Lithology: amphibolite

Cambrian thru Middle Ordovician carbonate rock (Cambrian - Middle Ordovician) at surface, covers < 0.1 % of this area

Cambrian thru Middle Ordovician (Barneveld) carbonate rock - occuring as slivers caught along thrusts of later allochthones, or carbonate blocks in Taconic Melange.

Lithology: carbonate; melange

Dalton Formation (Lower Cambrian and Proterozoic Z) at surface, covers 3 % of this area

Dalton Formation - Tan weathering, muscovite-microcline quartzite and feldspathic quartzite rich in black tourmaline, locally includes thin beds of other rock types listed below.

Lithology: quartzite

Hoosac Formation (Lower Cambrian and Proterozoic Z) at surface, covers 1 % of this area

Hoosac Formation - Lustrous greenish-gray schist characterized by 1-1.5 cm garnets; resembles Gassetts Schist of Vermont.

Lithology: schist

Walloomsac Schist (Middle Ordovician) at surface, covers < 0.1 % of this area

Walloomsac Schist - Black to dark-or silvery-gray, rarely layered schist or phyllite, composed of quartz, albite, and commonly garnet and staurolite or sillimanite (locally strongly retrograded to chlorite and muscovite). Locally feldspathic or calcareous near the base.

Lithology: schist; phyllite

Tectonic breccia (Ordovician) at surface, covers < 0.1 % of this area

Tectonic breccia - Zones of mixed inclusions of Stockbridge Formation, Walloomsac Formation, and phyllites of the Taconic allochthon.

Lithology: tectonic breccia