Sonyea Formation

Sonyea Group Stratigraphic range: Frasnian
Type	Group
Unit of	Frasnian
Sub-units	See text
Underlies	West Falls Group
Overlies	Genesee Group and Harrell Shale
Lithology
Primary	Shale
Other	Siltstone
Location
Region	Appalachian Basin of eastern North America
Country	United States
Stratigraphic cross-section of the Sonyea Formation in New York State

The Sonyea Group is a geologic group in the northern part of the Appalachian Basin. It preserves fossils dating back to the Devonian period.

In the western part, it is divided into the Cashaqua Shale at the top, and the Middlesex Shale at the bottom. In the east, various shale formations are included between the Cashaqua and Middlesex members, including Rye Point Shale, Rock Stream Formation ("Enfield Formation") Siltstone, Pulteney shale, Sawmill Creek Shale, Johns Creek Shale and Montour Shale.

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