Guadalupe igneous complex
Guadalupe igneous complex
Late Jurassic, ~149-153 Ma
Compositionally layered pluton intruding the southeast part of the western metamorphic belt. Gabbro at base grading upward (eastward) into meladiorite and granite, with an upper body of granophyre and rhyolite. Strongly foliated along the western margin where the pluton is bounded by the Bear Mountains fault, otherwise unfoliated. This unit has zircon U-Pb ages of ~149-153 Ma (Saleeby and others, 1989a; Ernst and others, 2009; Schweickert, 2015; Ratschbacher and others, 2018). The ~152 Ma age comes from the upper rhyolite part of the unit, which may be part of the wall rock (Ratschbacher and others, 2018). This pluton intrudes the roughly coeval Mariposa Formation (unit CMMS), so must have formed during or slightly after the regional deformation that formed the slaty cleavage predominant in the Cosumnes terrane.