Middle Mesozoic plutonism and deformation in the western Sierra Nevada foothills, California

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.

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