USGS Home
Contact USGS
Search USGS

Mineral Resources > Online Spatial Data > Geology > by state > New York Geology

Geologic units in Essex county, New York

Hybrid rock: mangeritic to charnockitic gneiss (Middle Proterozoic) at surface, covers 1 % of this area

Hybrid rock: mangeritic to charnockitic gneiss - with xenocrysts of calcic andesine and, locally, xenoliths of anorthosite; with increasing percentage of anorthosite component, passes gradationally into anorthositic rocks.

Lithology: gneiss; anorthosite

Pyroxene and/or hornblende granitic gneiss (Middle Proterozoic) at surface, covers 2 % of this area

Pyroxene and/or hornblende granitic gneiss - biotitic in part; sodic plagioclase ranges from generally subordinate to locally dominant; plagioclase-rich facies locally contain disseminated magnetite and magnetite ore bodies; grades westward into Yhbg, and southward into Ylg.

Lithology: granitic gneiss

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

Amphibolite - commonly biotitic; garnetiferous, pyroxenic, in and adjacent to Adirondack Highlands.

Lithology: amphibolite

Trenton and Black River Groups, undivided (Middle Ordovician) at surface, covers 0.3 % of this area

Trenton and Black River Groups, undivided - Glens Falls and Orwell Limestones. In Canada: Lindsay, Verulam, Bodcaygeon, Gull River Limestones; Shadow Lake Dolostone.

Lithology: limestone

Metanorthosite and anorthositic gneiss (Middle Proterozoic) at surface, covers 45 % of this area

Metanorthosite and anorthositic gneiss - mafic mineral percentage contoured in northwestern Marcy massif (St. Regis Quadrangle); contour value shown on high side of countoue line. See also Yach, Yack, Yamu.

Lithology: metavolcanic rock; paragneiss

Trachyte porphyry (Jurassic - Lower Cretaceous) at surface, covers < 0.1 % of this area

Trachyte porphyry - laccolith (?) at Cannon's Point near Willsboro, Essex County.

Lithology: trachyte

Beekmantown Group (in part) (Lower Ordovician) at surface, covers 2 % of this area

Beekmantown Group (in part) - In St. Lawrence Valley: Ogdensburg Dolostone (Beauharnois Dolostone in Canada); In Champlain Valley: Providence Island Dolostone; Fort Cassin Formation-limestone, dolostone; Fort Ann Formation (Spellman of Clinton and Essex Counties)-limestone, dolostone; Cutting Formation-dolostone (locally cherty), limestone, siltstone. In Vermont: includes Bridport, Bascom, Cutting, and Shelburne carbonates.

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

Biotite and/or hornblende granite gneiss (Middle Proterozoic) at surface, covers 0.3 % of this area

Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.

Lithology: paragneiss; metasedimentary rock; amphibolite; migmatite

Gabbroic or noritic metanorthosite (Middle Proterozoic) at surface, covers < 0.1 % of this area

Gabbroic or noritic metanorthosite - dark mineral content in excess of 10 percent (part of unit Ya).

Lithology: metavolcanic rock

Leucogranitic (alaskitic) gneiss (Middle Proterozoic) at surface, covers 2 % of this area

Leucogranitic (alaskitic) gneiss - sodic plagioclase ranges from generally subordinate to locally dominant; locally with biotite, hornblende, pyroxene, garnet, sillimanite, disseminated magnetite; commonly contains metasedimentary layers, amphibolite, migmatite; plagioclase-rich variety is host to magnetite ore bodies in eastern Adirondacks.

Lithology: granitic gneiss; metasedimentary rock; amphibolite; migmatite

Quartzite, quartz-biotite schist and graphitic schist (Middle Proterozoic) at surface, covers 0.3 % of this area

Quartzite, quartz-biotite schist and graphitic schist - in part feldspathic, micaceous, garnetiferous, sillimanitic.

Lithology: quartzite; schist

Glacial and Alluvial Deposits (Quaternary) at surface, covers 7 % of this area

Glacial and Alluvial Deposits - underlying bedrock geology unknown.

Lithology: alluvium; glacial drift

Lamprophyre, trachyte, and rhyolite dikes (Jurassic - Lower Cretaceous) at surface, covers < 0.1 % of this area

Lamprophyre, trachyte, and rhyolite dikes - not shown in Proterozoic terrane.

Lithology: lamprophyre; trachyte; rhyolite

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

Metagabbro - metagabbro, olivine metagabbro, derived amphibolite.

Lithology: mafic metavolcanic rock; amphibolite

Charnockite, granitic and quartz syenite gneiss (Middle Proterozoic) at surface, covers 11 % of this area

Charnockite, granitic and quartz syenite gneiss - variably leucocratic, containing varying amounts of hornblende, pyroxenes, biotite; may contain interlayered amphibolite, metasedimentary gneiss, migmatite. Overprint signifies inequigranular texture or phacoidal structure.

Lithology: granulite; felsic gneiss; granitic gneiss; amphibolite; migmatite

Interlayered gabbroic or noritic metanorthosite (Middle Proterozoic) at surface, covers 0.4 % of this area

Interlayered gabbroic or noritic metanorthosite - mangerite or charnockite, and the Yach lithology.

Lithology: metavolcanic rock; granulite; anorthosite

Charnockite, mangerite, pyroxene-quartz syenite gneiss (Middle Proterozoic) at surface, covers 6 % of this area

Charnockite, mangerite, pyroxene-quartz syenite gneiss - overprint signifies inequigranular texture.

Lithology: granulite; monzonite; gneiss

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss (Middle Proterozoic) at surface, covers 3 % of this area

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss.

Lithology: metasedimentary rock; gneiss

Beekmantown Group (in part) (Cambrian) at surface, covers < 0.1 % of this area

Beekmantown Group (in part) - In Champlain Valley: Whitehall Formation-dolostone, limestone (with Cryptozoon reefs); Ticonderoga Formation-dolostone (locally cherty), sandstone. In Vermont: Clarendon Springs Dolostone; Danby Formation-sandstone, quartzite, dolostone.

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

Canajoharie Shale (Middle Ordovician) at surface, covers < 0.1 % of this area

Canajoharie Shale - includes Hortonville and Ira Shales in Vermont.

Lithology: black shale

Biotite-quartz-plagioclase paragneiss, amphibolite, and related migmatite (Middle Proterozoic) at surface, covers 1 % of this area

Biotite-quartz-plagioclase paragneiss, amphibolite, and related migmatite - locally sillimanitic; commonly garnetiferous in and adjacent to Adirondack Highlands.

Lithology: paragneiss; amphibolite; migmatite

Stony Point Shale (Middle Ordovician) at surface, covers < 0.1 % of this area

Stony Point Shale

Lithology: shale

Undivided metasedimentary rock and related migmatite (Middle Proterozoic) at surface, covers 3 % of this area

Undivided metasedimentary rock and related migmatite.

Lithology: metasedimentary rock; migmatite

Mangerite, pyroxene-(hornblende) syenite gneiss (Middle Proterozoic) at surface, covers 0.7 % of this area

Mangerite, pyroxene syenite gneiss - pyroxene-(hornblende) syenitic gneiss; mesoperthite common. Overprint signifies inequigranular texture.

Lithology: monzonite; paragneiss

Potsdam Sandstone (Cambrian) at surface, covers 0.7 % of this area

Potsdam Sandstone (Covey Hill in Quebec)

Lithology: sandstone

Dolomitic and calcitic marbles interlayered with significant amounts of calcsilicate rock (Middle Proterozoic) at surface, covers 0.7 % of this area

Dolomitic and calcitic marbles interlayered with significant amounts of calcsilicate rock - metasedimentary amphibolite, pyroxene granulite, and various gneisses; includes interlayered diopsidic and tremolitic marble and quartzite, and talc-tremolite rock (mined in Balmat-Edwards belt, northwest Adirondacks).

Lithology: marble; calc-silicate rock; amphibolite; granulite; gneiss; quartzite; schist

Valcour, Crown Point, and Day Point Limestones (Middle Ordovician) at surface, covers 0.5 % of this area

Valcour, Crown Point, and Day Point Limestones - locally reefy, Ste. Therese Siltstone at base; Middlebury Limestone in Vermont; St. Martin and Rockcliffe Limestones in St. Lawrence Valley. Includes some Otbr and Obk adjacent to Champlain Thrust in Vermont.

Lithology: limestone; siltstone

Calcitic and dolomitic marble (Middle Proterozoic) at surface, covers 3 % of this area

Calcitic and dolomitic marble - predominantly; variably siliceous; in part with calcsilicate rock and amphibolite.

Lithology: marble; calc-silicate rock; amphibolite

Hybrid rock: anorthositic and metasedimentary rock (Middle Proterozoic) at surface, covers 2 % of this area

Hybrid rock: anorthositic and metasedimentary rock - ranges from anorthositic rock with local blocks, shreds or layers of undifferentiated metasediment, to mappable roof pendants and/or xenoliths of metasediment in anorthositic rock.

Lithology: anorthosite; metasedimentary rock

Ferrohedenbergite-fayalite granite and granite gneiss (Middle Proterozoic) at surface, covers < 0.1 % of this area

Ferrohedenbergite-fayalite granite and granite gneiss.

Lithology: granite; granitic gneiss