Geologic units in Columbia county, New York

Walloomsac Formation (Middle Ordovician) at surface, covers 25 % of this area

Slate, phyllite, schist, metagraywacke.

Elizaville Formation (Cambrian - Ordovician) at surface, covers 13 % of this area

Shale, argillite, quartzite.

Nassau Formation (Cambrian?) at surface, covers 9 % of this area

South of 43 degrees; slate, shale, thin quartzite, includes Stuyvesant Conglomerate, Diamond Rock Quartzite, Curtis Mountain Quartzite, and Bomoseen Graywacke Members.

Germantown Formation (Cambrian) at surface, covers 8 % of this area

South of Troy; shale, conglomerate, limestone.

Mount Merino and Indian River Formations (Ordovician) at surface, covers 7 % of this area

Shale, slate, cherts.

Stuyvesant Falls Formation (Ordovician) at surface, covers 7 % of this area

South of Troy; shale, siltstone.

Austin Glen Formation (Middle Ordovician) at surface, covers 6 % of this area

Graywacke, shale

Austerlitz Phyllite (Cambrian?) at surface, covers 5 % of this area

Austerlitz Phyllite - minor quartzite

Copake and Halcyon Lake Formations, Rochdale Limestone (Lower Ordovician) at surface, covers 5 % of this area

Columbia County: Copake Formation-limestone, dolostone; Halcyon Lake Formation-chert, calc-dolostone.

Glacial and Alluvial Deposits (Quaternary) at surface, covers 5 % of this area

Underlying bedrock geology unknown.

Stockbridge Formation (Cambrian - Lower Ordovician) at surface, covers 2 % of this area

Calcitic and dolomitic marble.

Everett Schist (Cambrian?) at surface, covers 2 % of this area

Minor meta-graywacke lenses. Includes Greylock Schist in Massachusetts.

Briarcliff Dolostone and Pine Plains Formation (Cambrian) at surface, covers 1 % of this area

Columbia County: Pine Plains-dolostone, oolite, shale.

Walloomsac Formation (Middle Ordovician) at surface, covers 1 % of this area

Phyllite, schist, metagraywacke.

Normanskill Shale (Middle Ordovician) at surface, covers 0.9 % of this area

Minor mudstone, sandstone.

Balmville Limestone (Middle Ordovician) at surface, covers 0.8 % of this area

Vermont: Whipple Limestone.

Taconic Melange (Middle Ordovician) at surface, covers 0.8 % 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.

Rensselaer Graywacke (Cambrian?) at surface, covers 0.8 % of this area

Minor shale.

Cambrian thru Middle Ordovician carbonate rock (Cambrian - Middle Ordovician) at surface, covers 0.5 % 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.

Helderberg Group (Lower Devonian) at surface, covers 0.3 % of this area

West of Albany: Alsen, Becraft, New Scotland, Kalkberg, Coeymans, and Manlius Limestones; Rondout Dolostone. South of Albany: Port Ewen, Alsen thru Manlius Limestones; Rondout Dolostone.

Briarcliff Dolostone and Pine Plains Formation (Cambrian) at surface, covers 0.3 % of this area

Briarcliff - locally cherty; Pines Plains - dolostone, shale, oolite.

Copake and Rochdale Formations (Lower Ordovician) at surface, covers 0.2 % of this area

Copake Formation-limestone, dolostone, siltstone; Rochdale Formation-limestone, dolostone; Halcyon Lake Dolostone-locally cherty.

Greenstones and tuffs and/or basalt (Cambrian?) at surface, covers 0.2 % of this area

Greenstones and tuffs and/or basalt

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

Schoharie Formation-shale, limestone; Carlisle Center Siltstone; Esopus Shale.

Balmville Limestone (Middle Ordovician) at surface, covers < 0.1 % of this area

Balmville Limestone

Stissing Formation (Cambrian) at surface, covers < 0.1 % of this area

Dolostone, shale.

Cheshire Quartzite and Dalton Formation (Cambrian) at surface, covers < 0.1 % of this area

Cheshire Quartzite and Dalton Formation

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

Stockbridge Marble.