Hornfels
Late Cretaceous, about 100 to 66 million years old. 4 crags on this site have their map point on it.
What the map says
Dense, black hornfels and metasandstone in window of Williams Range thrust near Keystone; Pierre Shale metamorphosed by nearby Eocene Montezuma stock. Bedding is preserved at most locations
1:100,000 sheet: Kellogg and others, 2008, USGS Geologic Investigations Series 3000 (4 crags). A contact line at that scale is about 100 m wide on the ground.
Served by Macrostrat (CC BY 4.0). The wording is the map's own, quoted as a fact about the mapped unit, not about any one wall.