Jurassic structural evolution of the King Creek area, southern Ritter Range, Sierra Nevada, CA

The Sierra Nevada Batholith (SNB), of California, is a long-lived continental arc and orogen that experienced three magmatic and tectonic flare-ups in the Triassic, Jurassic, and Cretaceous. Although large portions of the central SNB have been overprinted by the Cretaceous flare-up, the King Creek area in the southern Ritter Range preserves a record of the complex history of the Jurassic arc. The ~168 Ma King Creek pluton intrudes a package of ~180-163 Ma interbedded metavolcanics and marine sediments, which prior to and during pluton emplacement were rotated to steep SW dips (avg D/DD = 69/220), displaced downward to emplacement depths (ca 2-3 kb) and internally cleaved (shortening strains of 30-60%) in a fold and thrust belt (potentially related to the Eastern Sierra Thrust system). A sub-vertical (avg = 89/212) magmatic foliation in the King Creek pluton, subparallel to host rock cleavage further supports regional NW-SE shortening prior to and during emplacement.

Bi-modal, E-W striking (avg = 87/188), ~155 Ma dikes, related to the Independence Dike Swarm, intrude the King Creek granodiorite and Jurassic host rock. The dikes, which record ~13% local N-S extension perpendicular to the dike walls, have margins with magmatic mullion and flame structures, preserve magmatic isoclinal and sheath folds and locally show submagmatic to solid-state boudinage. Syn- to post-dike-emplacement shears are also recorded throughout the King Creek pluton and dikes. We speculate the variable orientation of shears found in the King Creek pluton may be a result of a conjugate set of N-S and E-W striking (89/260 and 90/178) shears: dike features and shears together are compatible with sinistral transpression. The King Creek pluton and intruded volcanic package, are unconformably overlain by 103-100 Ma, less tilted and strained volcanic package related to the Minarets Caldera complex. Both Jurassic and Cretaceous volcanic packages are intruded by ~100 to 98 Ma plutons at depths of ca 3 kbars.

This multi-stage structural history of Jurassic SW-NE compression (~160-170 Ma), N-S extension (~155 Ma), sinistral transpression (~155-149 Ma), and repeated episodes of crustal thickening and exhumation between ~180-98 Ma, recorded in the King Creek area exemplifies the dynamic tectono-magmatic processes occurring in continental arc settings.