Abstract Southeastward beyond the southern termination of the Sierran Foothills metamorphic belt, metamorphic pendants of Paleozoic ophiolitic basement are intruded by Middle Jurassic to Early Cretaceous, mafic-to-intermediate plutonic rocks. These rocks constitute a record of the various plutonic environments that were active along the western North American margin during the middle Mesozoic: a Middle Jurassic ensimatic arc, a Late Jurassic, Nevadan-age, transpressional-transtensional regime, and an emergent, Early Cretaceous continental-margin arc. In detail, these plutonic suites reveal the roles that both pre-and synmagmatic structures—such as Paleozoic transform faults, Nevadan-age regional sutures, and localized Cretaceous crustal tears—played in focusing magmatism. Taken together, outcrops of the Kings River ophiolite, the Owens Mountain dike swarm, and the Stokes Mountain ring dike complexes reveal a sequence of tectonic and magmatic processes through which accreted oceanic lithosphere was transformed into continental crust .

Abstract Petrologic, structural, geochronologic, and geochemical data from rocks exposed in the western foothills of the Sierra Nevada batholith just south of the western Foothills metamorphic belt (the Stokes Mountain region) provide new insight regarding several poorly understood aspects of the development of the compound Sierra Nevada arc. Exposures of three different metasedimentary packages together document transitions in the depositional environments present along the outboard edge of this arc segment throughout the Mesozoic Era, culminating in the emergence of the Cretaceous continental margin arc. Exposures of mafic cumulates and associated differentiates of the Early Cretaceous batholith permit investigation into the earliest stages of differentiation of depleted-mantle–derived arc magmas. Together with the surrounding Kings-Kaweah ophiolite belt, these Mesozoic plutonic and metasedimentary rocks are proposed to form an analog for the crystalline basement underlying much of the eastern half of the Great Valley forearc basin.