No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

Pre-Middle Jurassic stratigraphic assemblages in the northern Sierra Nevada are contained in tightly folded but macroscopically shallowly dipping nappes. Four shallowly east-dipping f] faults juxtapose, in descending structural order, the Northern Sierra terrane, the Feather River peridotite/Devils Gate ophiolite, the Red Ant Schist, the Calaveras Complex, and the Fiddle Creek Complex. The fi Slate Creek thrust dips shallowly west; it places the Slate Creek Complex over the Red Ant Schist, Calaveras Complex, and Fiddle Creek Complex, and thus cuts two fj faults. As many as three Early Jurassic magmatic arcs may be represented by the stratigraphic assemblages in the fj-f2 nappe pile. A continental-margin arc is represented by Late Triassic-Middle Jurassic volcanogenic rocks in the upper part of the Northern Sierra terrane stratigraphy and by coeval plutons in the eastern part of the Sierra Nevada batholith; the associated subduction complex is represented by blueschist-facies metamorphism in the RedAnt Schist and melange structure in oceanic rocks of the Calaveras Complex. An intraoceanic arc is represented by the Fiddle Creek Complex, which contains ophiolitic basement overlain and intruded by Early Jurassic volcanic and plutonic rocks; the volcanic strata are intercalated with cherty deposits, olistostromes, and volcaniclastic rocks devoid of continental detritus. A more westerly Early Jurassic intraoceanic arc is represented by the Slate Creek Complex, which has ophiolitic structure. These units were juxtaposed along the fi and f2 faults before Callovian-Kimmeridgian (Middle to Late Jurassic) deposition of volcanic and epiclastic strata and coeval intrusion of mafic-intermediate plutons; this postamalgamation arc was extensional in its western part, as indicated by sheeted dikes in the Smartville Complex. The Callovian-Kimmeridgian rocks and their basement of iy-li nappes are cut by two sets of oppositely dipping fj faults, a shallowly west-dipping set (Taylorsville and related thrust faults) and a steeply east-dipping set (Foothills fault system); f3 faults are the only major Late Jurassic (Nevadan) or younger faults in the northern Sierra Nevada. This structural chronology rules out models for Late Jurassic (Nevadan) collisions, but allows collision(s) of the Fiddle Creek and Slate Creek arcs in the Early or Middle Jurassic.