Mount Givens pluton
Mount Givens pluton
Late Cretaceous, ~88-98 Ma
Occurs along axial part of central Sierra Nevada. Chiefly granodiorite and granite with lesser tonalite, granite, and minor alaskite. Small bodies of aplite granite occur in center of northern and southern parts of pluton. Bulbous northern part of pluton exhibits both equigranular facies and K-feldspar megacryst facies with K-feldspar up to 3 cm long. One of largest single plutons in Sierra Nevada batholith. Pluton located between younger John Muir Intrusive Suite (unit Gjm) to east and older Shaver intrusive suite (unit Gsl) to west. Unit included in John Muir Intrusive Suite by Bateman (1992). Delineated separately herein because it consists of a single, large, distinct pluton. Zircon U-Pb ages from this unit range from ~88-98 Ma (Stern and others, 1981; Frazer and others, 2014). Kistler and others (1966) report biotite K-Ar ages of ~82-88 Ma, hornblende K-Ar ages of ~87 and ~88 Ma, and a whole rock Rb-Sr age of ~82 Ma. Naeser and Dodge (1969) report sphene fission track ages of ~77-90 Ma and apatite fission track ages of ~74-84 Ma.