Intrusive rocks, undivided
Cenozoic, about 66 to 2.6 million years old. 1 crag on this site has its map point on it.
What the map says
Dikes, sills, and small plugs; typically very fine grained or altered; composition roughly estimated from proportions of sparse to abundant phenocryst minerals. Numerous bodies with abundant phenocrysts in northwest part of map area include andesite, latite, quartz latite, dacite, or rhyolite porphyries in the form of steep-walled dikes and plugs; probably of late Oligocene age, based on age of major intrusions in this part of map area. Latite-andesite and dacite intrusions are typical near Longs Peak and to the south, where these rocks form flat-lying sheets as well as steeply dipping dikes and plugs; age may range from Eocene to latest Cretaceous, based on age of nearby major intrusions to the south (Gable, 1980). Dike at Red Deer Lake (southwest of St. Vrain Mountain) has been dated as 52.6+/-5.6 Ma (Pearson, 1980, p. 20), or early Eocene. GRI Source Map ID 141 (I-1973). Lithology: intrusive igneous (plutonic).
1:100,000 sheet: National Park Service Geologic Resources Evaluation program, 2006, National Park Service (1 crag). 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.