Geologic units in Orleans county, New York

Queenston Shale (Upper Ordovician) at surface, covers 52 % of this area

Queenston Shale

Lockport Group (Upper Silurian) at surface, covers 22 % of this area

Consists of: Guelph, Oak Orchard, Eramosa, and Goat Island Dolostones; Gasport Limestone-local bioherms.

Medina Group (Lower Silurian) at surface, covers 8 % of this area

Consists of: Thorold Sandstone; Grimsby Formation-sandstone, shale; Power Glen and Cabot Head Shales; Whirlpool Sandstone.

Camillus, Syracuse, and Vernon Formations (Upper Silurian) at surface, covers 8 % of this area

Shale, dolostone, salt, and gypsum.

Decew Dolostone and Rochester Shale (Lower Silurian) at surface, covers 5 % of this area

Decew Dolostone and Rochester Shale

Irondequoit Limestone thru Kodak Sandstone (Lower Silurian) at surface, covers 4 % of this area

Includes: Irondequoit Limestone, Rockway Dolostone, Hickory Corners Limestone, Neahga Shale, and Kodak Sandstone.