Tuolumne Intrusive Suite
Tuolumne Intrusive Suite
Cretaceous, ~86-96 Ma
Occurs along crest and to west of crest of central Sierra Nevada. One of the Sierra Crest intrusive suites (e.g. Lackey and others, 2008; Hildebrand and Whalen, 2021). Chiefly granodiorite, tonalite, and granite. Zircon U-Pb ages from this unit range from ~86-96 Ma (Stern and others, 1981; Coleman and Glazner, 1997; Coleman and others, 2004; Burgess and Miller, 2008; Bracciali and others, 2008; Memeti and others, 2010, 2022; Paterson and others, 2016). Biotite K-Ar ages range from ~80-85 Ma (with an outlier of ~69 Ma), along with single K-Ar ages of ~84 Ma (hornblende), ~70 Ma (plagioclase), ~74 Ma (K-feldspar), and ~89 Ma (quartz) (Evernden and Kistler, 1970). Naesser and Dodge (1969) report an apatite fission track age of ~85 Ma. Hildebrand and Whalen (2021) report relatively high Nb/Y, La/Yb, and Sr/Y for this unit. Lackey and others (2008) report low zircon d18O (~5-6.5 o/oo VSMOW) and whole-rock d18O (~5-8 o/oo VSMOW) and 87Sr/86Sri values between ~.706-.708. Major plutons: granodiorites of Kuna Crest and Grayling Lake and tonalites of Glen Aulin and Glacier Point, equigranular Half Dome Granodiorite, porphyritic Half Dome Granodiorite, Cathedral Peak Granodiorite, Johnson Granite Porphyry, Yosemite Creek Granodiorite and Sentinel Granodiorite. Best-known intrusive suite in Sierra Nevada.