The Eramosa Member is a Silurian stratigraphic unit of the Lockport Formation exposed along the Niagara Escarpment in Ontario and western New York State. In the late nineteenth century it was an important source of building stone in Hamilton, Ancaster and Waterdown, and in the late twentieth century quarries in a similar unit, also called the Eramosa, near Wiarton in the Bruce Peninsula, became an important source of dimension stone at a time when most of the other resources of similar stone were depleted. Work in these quarries led to the discovery of exceptionally well preserved fossils. On the east Mountain at Hamilton, a well-developed cave system was discovered in the Eramosa and has now been designated as the Eramosa Karst Conservation Area.