Geologic units in Erie county, New York

Machias Formation (Upper Devonian) at surface, covers 35 % of this area

Shale, siltstone; Rushford Sandstone; Caneadea, Canisteo, and Hume Shales; Canaseraga Sandstone; South Wales and Dunkirk Shales.

Angola and Rhinestreet Shales (Upper Devonian) at surface, covers 19 % of this area

Angola and Rhinestreet Shales.

Camillus, Syracuse, and Vernon Formations (Upper Silurian) at surface, covers 16 % of this area

Shale, dolostone, salt, and gypsum.

Onondaga and Bois Blanc Limestones (Middle Devonian) at surface, covers 9 % of this area

In New York: Onondaga Limestone-Seneca, Morehouse (cherty), and Clarence Limestone Members, Edgecliff cherty Limestone Member, local coral bioherms; Bois Blanc Limestone-sandy, thin, discontinous. In Ontario: Dundee Limestone; Lucas Formation-dolostone, limestone (Anderdon); Amherstburg Formation-limestone, dolostone, sandstone (Sylvania); Bois Blanc Formation-dolostone, limestone, sandstone (Springvale).

Skaneateles Formation (Middle Devonian) at surface, covers 5 % of this area

Levanna Shale, Stafford Limestone Members.

Wiscoy Formation (Upper Devonian) at surface, covers 4 % of this area

Sandstone, shale; Hanover and Pipe Creek Shales.

Ludlowville Formation (Middle Devonian) at surface, covers 3 % of this area

Deep Run Shale, Tichenor Limestone, Wanakah and Ledyard Shales, Centerfield Limestone Members.

Marcellus Formation (Middle Devonian) at surface, covers 2 % of this area

Oatka Creek Shale Member.

Cashaqua and Middlesex Shales (Upper Devonian) at surface, covers 2 % of this area

Cashaqua and Middlesex Shales.

Moscow Formation (Middle Devonian) at surface, covers 2 % of this area

Windom and Kashong Shales, Menteth Limestone Members.

Akron Dolostone (Upper Silurian) at surface, covers 1 % of this area

Bertie Formation - dolostone, shale.

Genesee Group (Upper Devonian) at surface, covers 0.6 % of this area

West River Shale; Genundewa Limestone; Penn Yan and Geneseo Shales; North Evans Limestone.

Gowanda, South Wales, and Dunkirk Shales (Upper Devonian) at surface, covers < 0.1 % of this area

Gowanda, South Wales, and Dunkirk Shales.

Oswayo and Venango Formations (Upper Devonian) at surface, covers < 0.1 % of this area

Shale, siltstone, sandstone; replaced eastwardly by Cattaraugus Formation-shale, sandstone, conglomerate.