Geologic units in Saratoga county, New York

Canajoharie Shale (Middle Ordovician) at surface, covers 38 % of this area

Canajoharie Shale

Undivided metasedimentary rock and related migmatite (Middle Proterozoic) at surface, covers 20 % of this area

Undivided metasedimentary rock and related migmatite.

Biotite and/or hornblende granite gneiss (Middle Proterozoic) at surface, covers 8 % of this area

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. In northwest Adirondacks, grades into Yphg.

Theresa (Galway) Formation (Cambrian) at surface, covers 6 % of this area

Dolostone, sandstone, shale.

Mount Merino and Indian River Formations (Ordovician) at surface, covers 4 % of this area

Shale, slate, cherts.

Beekmantown Group (Cambrian) at surface, covers 4 % of this area

Mohawk Valley: Little Falls Dolostone-chert; Hoyt Formation-limestone, dolostone, oolite. Washington county: Whitehall Formation-dolostone, limestone; Ticonderoga Dolostone-chert.

Austin Glen Formation (Middle Ordovician) at surface, covers 3 % of this area

Graywacke, shale

Charnockite, granitic and quartz syenite gneiss (Middle Proterozoic) at surface, covers 3 % of this area

Variably leucocratic, containing varying amounts of hornblende, pyroxenes, biotite; may contain interlayered amphibolite, metasedimentary gneiss, migmatite. Overprint signifies inequigranular texture or phacoidal structure.

Schenectady Formation (Upper Ordovician) at surface, covers 3 % of this area

Graywacke, sandstone, siltstone, shale.

Beekmantown Group (Lower Ordovician) at surface, covers 3 % of this area

Mohawk Valley: Chuctanunda Creek Dolostone; Tribes Hill Formation-limestone, dolostaone; Gailor Dolostone. Washington County: Providence Island Dolostone; Fort Cassin Formation-limestone, dolostone; Fort Ann Formation-limestone, dolostone; Cutting Formation-dolostone, local chert, limestone at top, siltstone at base.

Potsdam Sandstone (Cambrian) at surface, covers 2 % of this area

Potsdam Sandstone

Quartzite, quartz schist and graphitic schist (Middle Proterozoic) at surface, covers 2 % of this area

In part feldspathic, micaceous, garnetiferous, sillimanitic.

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss (Middle Proterozoic) at surface, covers 2 % of this area

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

Glacial and Alluvial Deposits (Quaternary) at surface, covers 1 % of this area

Underlying bedrock geology unknown.

Trenton and Black River Groups, undivided (Middle Ordovician) at surface, covers 0.9 % of this area

Mohawk Valley: Dolgeville, Denley, Sugar River, Kings Falls, Glens Falls, Rockland, Amsterdam, and Lowville Limestones. Washington County: Glens Falls and Orwell Limestones.

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

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.

Taconic Melange (Middle Ordovician) at surface, covers < 0.1 % of this area

Chaotic mixture of Early Cambrian thru Middle Ordovician pebble to block-size angular to rounded clasts in a pelitic matrix of Middle Ordovician (Barneveld) age. Rims and floors earlier submarine gravity slides of Taconian Orogeny.

Interlayered amphibolite and granitic, charnockitic, mangeritic, or syenitic gneiss (Middle Proterozoic) at surface, covers < 0.1 % of this area

Interlayered amphibolite and granitic, charnockitic, mangeritic, or syenitic gneiss.

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

Occuring as slivers caught along thrusts of later allochthones, or carbonate blocks in Taconic Melange. Also mapped as horses along normal faults.

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

Metagabbro, olivine metagabbro, derived amphibolite.

Quartz-feldspar gneiss (Middle Proterozoic) at surface, covers < 0.1 % of this area

With variable amounts of garnet, sillimanite, biotite.

Pillow lava (Ordovician) at surface, covers < 0.1 % of this area

At Stark's Knob near Schuylerville, Saratoga County.

Biotite-quartz-plagioclase gneiss, amphibolite, and related migmatite (Middle Proterozoic) at surface, covers < 0.1 % of this area

Locally sillimanitic; commonly garnetiferous in and adjacent to Adirondack Highlands.

Leucogranitic gneiss (Middle Proterozoic) at surface, covers < 0.1 % of this area

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.

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

Minor mudstone, sandstone.

Biotite-quartz-plagioclase gneiss (Middle Proterozoic) at surface, covers < 0.1 % of this area

Commonly very low in biotite content, with interbedded feldspathic and biotitic quartzite and amphibolite; sillimanite and garnet common, graphite sporadic.