Merced Peak and Washburn Lake intrusive suite
Merced Peak and Washburn Lake intrusive suite
Late Cretaceous, ~93-100 Ma
Occurs along southeastern margin of Yosemite Valley in the central Sierra Nevada. Chiefly granodiorite, leucogranite, and granite. This unit has yielded zircon U-Pb ages of ~93-100 Ma (Stern and others, 1981; Tobisch and others, 1995; Attia and others, 2022), as well as biotite Ar-Ar ~85 Ma, hornblende Ar-Ar ~87 Ma, and an allanite fission track age of ~87 Ma (Naeser and Dodge, 1969; Tobisch and others, 1995). Major plutons: granodiorite of Jackass Lakes, leucogranites of Timber Knob and Norris Creek, granodiorite of Red Devil Lake, granite of Turner Lake, and granite porphyry of Cony Crags. May be a younger phase of the ~100-112 Ma Buena Vista Crest intrusive suite (unit Gbvc). Correlated with roughly coeval meta-volcanic and meta-shallow intrusive rocks of Sierra Crest terrane (units SHKOV, SHKOG), forming part of the Monarch arc.