Twin Lakes granodiorite
Granite. Paleocene, about 66 to 56 million years old. 3 crags on this site have their map point on it.
What the map says
Gray to tan, medium- to coarse-grained, equigranular to strongly porphyritic biotite granodiorite and monzogranite. Most rocks contain distinctive, euhedral to subhedral pinkish-gray orthoclase phenocrysts as long as 10 cm; some show prominent Carlsbad twinning. Core zone is more leucocratic and less porphyritic (Fridrich and others, 1998). The Twin Lakes Granodiorite batholith is cut by numerous quartz monzonite porphyry dikes (Cappa and Bartos, 2007). Sphene fission-track ages and one K-Ar biotite age from the Twin Lakes Granodiorite range from 40 to 46 Ma (Obradovich and others, 1969; Shannon, 1988). These ages may have been reset by emplacement of 33-Ma Grizzly Peak caldera immediately to the west; a 40Ar/39Ar date considered more representative of emplacement age, from eastern part of batholith, is 64.6±1.4 Ma (Fridrich and others, 1998; age corrected for revised standards of Kuiper and others, 2008)
1:100,000 sheet: Kellogg and others, 2017, U.S. Geological Survey Scientific Investigations Map 3382 (3 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.