Triassic and Jurassic rocks in the Black Rock Desert of northwest Nevada comprise part of the Mesozoic volcanic arc successions found throughout the westernmost U.S. Cordillera. Detailed structural studies in the Pine Forest Range, located in the western Black Rock Desert, provide new insight into the Jurassic structural history of this part of the Mesozoic arc system. Regional Jurassic deformation and metamorphism in the Pine Forest Range affected a thick (~10.5 km) section of lower(?) Paleozoic through Triassic strata that were tilted after deformation and are now exposed in approximately cross-sectional view. At high stratigraphic levels, deformation produced a slaty cleavage and relatively open folds, both of which are concentrated in rheologically incompetent rock types, and was accompanied by metamorphism at low grade. At deeper stratigraphic levels, the regional foliation intensifies and becomes more pervasive, folds tighten, and metamorphic grade increases through greenschist into amphibolite grade. At the deepest stratigraphic levels, the rocks are amphibolite grade L--S tectonites with a pronounced mylonitic fabric. The ~2 km-thick-zone of mylonites is interpreted as a ductile shear zone that formed when the stratigraphic section was still upright, whereas the less deformed, younger rocks are interpreted to occupy the upper plate of the shear zone and to record a strain gradient away from the shear zone. A variety of structural and regional relations indicate that the shear zone is a ductile thrust fault along which younger rocks moved to the northwest (in present-day coordinates) with respect to older rocks. The timing of regional Jurassic deformation and metamorphism is constrained by relations in and around two plutons dated by the U-Pb zircon method. The 201¿1 Ma Big Creek pluton was intruded as a sill-like body along the upper levels of the shear zone and is associated with a variety of features indicating syntectonic intrusion, including internal textural features in plutonic rocks and metamorphic changes in wall rocks with proximity to the pluton. The 185¿1 Ma Theodore pluton which intrudes across part of the shear zone has a thermal aureole which statically overprints the shear zone fabric. Deformation was thus ongoing at 201 Ma and over by 185 Ma. The Early Jurassic age of regional shortening deformation in the Pine Forest Range contrasts with the Middle to Late Jurassic (~170-150 Ma) age of regional shortening documented in many other parts of the Mesozoic arc system, including the Klamath Mountains, Sierra Nevada, and Mojave Desert regions of California. It also contrasts with the record of Early Jurassic extensional tectonism documented in the Sierra Nevada, Mojave Desert, and western Arizona segments of the Mesozoic arc system. These conflicting relations indicate a complex tectonic evolution for the Jurassic U.S. Cordillera plate margin and lend support to the idea that disparate parts of this plate margin were juxtaposed along younger strike-slip faults. ¿ American Geophysical Union 1996