Geologic units in Steuben county, New York

Machias Formation (Upper Devonian) at surface, covers 31 % of this area

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

Wiscoy Formation (Upper Devonian) at surface, covers 19 % of this area

Sandstone, shale; Hanover and Pipe Creek Shales.

West Hill and Gardeau Formations (Upper Devonian) at surface, covers 11 % of this area

Shale, siltstone; Roricks Glen Shale; upper Beers Hill Shale; Grimes Siltstone.

Nunda Formation, West Hill Formation (Upper Devonian) at surface, covers 10 % of this area

Nunda: sandstone, shale; West Hill: shale, siltstone; Corning Shale.

Conneaut Group, undivided (Upper Devonian) at surface, covers 8 % of this area

In west: Ellicott and Dexterville Formations-shale, siltstone. In east: Germania Formation-shale, sandstone; Whitesville Formation-shale, sandstone; Hinsdale Sandstone; Wellsville Formation-shale, sandstone; Cuba Sandstone.

Gardeau Formation (Upper Devonian) at surface, covers 7 % of this area

Shale, siltstone; Roricks Glen Shale.

Beers Hill, Dunn Hill, Millport, and Moreland Shales; Grimes Siltstone (Upper Devonian) at surface, covers 5 % of this area

Beers Hill, Dunn Hill, Millport, and Moreland Shales; Grimes Siltstone.

Nunda Formation (Upper Devonian) at surface, covers 3 % of this area

Sandstone, shale.

Nunda Formation (Upper Devonian) at surface, covers 2 % of this area

Sandstone, shale.

Machias Formation (Upper Devonian) at surface, covers 1 % of this area

Shale, siltstone; Rushford Sandstone; Caneadea, Canisteo, and Hume Shales; Canaseraga Sandstone; South Wales and Dunkirk Shales; In Pennsylvania: Towanda Formation-shale, sandstone.

Wiscoy Formation (Upper Devonian) at surface, covers 1 % of this area

Sandstone, shale; Hanover and Pipe Creek Shales.

West Hill and Gardeau Formations (Upper Devonian) at surface, covers 0.9 % of this area

Shale, siltstone; Roricks Glen Shale; upper Beers Hill Shale; Grimes Siltstone.

Sonyea Group (Upper Devonian) at surface, covers 0.8 % of this area

In west: Cashaqua and Middlesex Shales. In east: Rye Point Shale; Rock Stream ("Enfield") Siltstone; Pulteney, Sawmill Creek, Johns Creek, and Montour Shales.

Conneaut Group, undivided (Upper Devonian) at surface, covers < 0.1 % of this area

Germania Formation-shale, sandstone; Whitesville Formation-shale, sandstone; Hinsdale Sandstone; Wellsville Formation-shale, sandstone; Cuba Sandstone.

Genesee Group (Upper Devonian) at surface, covers < 0.1 % of this area

West River Shale; Genundewa Limestone; Penn Yan and Geneseo Shales; all except Geneseo replaced eastwardly by Ithaca Formation-shale, siltstone and Sherburne Siltstone.