Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite
Sandstone. Zanclean, about 5.3 to 3.6 million years old. 1 crag on this site has its map point on it.
The map groups these named formations into this unit: Hinsdale Formation, Servilleta Formation.
What the map says
Includes basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences Lithology: basalt, minor volcanic, conglomerate.
1:500,000 sheet: Horton and others, 2017, U.S. Geological Survey Data Series 1052 (1 crag). A contact line at that scale is about 500 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.