The Nevada Jurassic Magmatic Province is defined as a region of abundant late Middle and Late Jurassic plutonism and associated deformation inboard of the contemporaneous magmatic arc. The stratigraphic, structural, and magmatic history of the Nevada Jurassic Magmatic Province allows assessment of the relative importance of crustal kinematics and thermal perturbation of the lithospheric mantle in Jurassic tectonics of the northern Great Basin. Constraints on the tectonic development of an area far inboard of the plate boundary enhance understanding of the causes of intraplate deformation and magmatism and their relationship to the plate boundary. Simple thermal models, estimates of the magnitude of crustal shortening during the Jurassic, isotopic compositions of Jurassic plutons, and near synchroneity of magmatism and deformation argue that crustal thickening was not the primary cause of plutonism in the Nevada Jurassic Magmatic Province. Rather, a thermal perturbation of the lithospheric mantle, modeled as subduction-induced asthenospheric flow, is considered the primary cause of Jurassic plutonism. Subduction-induced flow in the asthenosphere may lead to thermal erosion of the lithosphere and subsequent crustal heating. Broad, low-relief uplift of the Nevada Jurassic Magmatic Province and minor, outward-directed crustal shortening are consistent with the predicted isostatic and rheologic consequences of lithospheric thinning. Emplacement of magmas, generated by increased crustal temperatures and decompression of mantle rocks, also influenced crustal deformation locally. The Jurassic tectonic development of a large part of the northern Great Basin can be explained by lithospheric thinning in the absence of large-scale crustal shortening. If the tectonic development of the Nevada Jurassic Magmatic Province was ultimately due to subduction-induced asthenospheric flow the implication is that intraplate deformation and magmatism are primarily thermally controlled processes. Crustal deformation is, then, a consequence of magma generation and thermal weakening of the crust. Although transmission of compressive stress to areas inboard of the plate boundary may occur, it appears to be a secondary effect rather than the primary cause of intraplate deformation.

Jurassic tectonism in the northeastern Great Basin produced varied structures, many closely associated with widespread magmatism at ca. 155–165 Ma and with local metamorphism. Many of the plutons are of suitable mineralogy for Al-in-hornblende barometry, providing the potential for depth data. We have studied conditions of metamorphism in the Pilot Range and barometry for six Jurassic plutons across the northeastern Great Basin. All barometry results are in harmony with pressures estimated from stratigraphic data, requiring little or no tectonic thickening. On the basis of structural styles and barometric data, we divide the northeastern Great Basin into three Jurassic tectonic provinces. An eastern extensional province, largely in western Utah, is characterized by Paleozoic strata that were thrust faulted and then intruded by shallow plutons shortly after or during normal and strike-slip faulting. Extension was probably a short-lived event associated with magmatism, but its west trend indicates a total reorientation of stress at this time, perhaps within transtensional strike-slip zones. A central province of modest, and possibly locally extreme, Jurassic shortening in eastern Nevada is characterized by metamorphosed Paleozoic rocks and by thrusts and kilometer-scale southeast-vergent folds. Upper amphibolite facies, but low pressure (3–4 kbar) metamorphism is present near Jurassic plutons in the Pilot Range and Ruby Mountains, probably indicating metamorphism induced by heat from magmas. In contrast, metamorphism in other ranges, which is known only to be pre–Late Cretaceous, indicates thickening of 10–20 km. This thickening may have entirely postdated the Jurassic. A western province in north-central Nevada is characterized by preserved Jurassic volcanic rocks and shallow plutons, indicating that little erosion, and probably surface uplift, occurred during the late Mesozoic. Folds and thrust faults indicate minor Jurassic shortening but many structures are undated. The low-pressure upper-crustal conditions for demonstrably Jurassic events suggest that higher-pressure metamorphism recorded in the central province is younger (Cretaceous) in age. We suggest that Jurassic structures were caused by distributed minor crustal shortening, manifested mainly as small-scale thrust faults. Local thermal highs created by plutonism produced metamorphic zones in relatively shallow crust. Shortening in the east was manifested by zones of strike-slip, within which plutons were emplaced in tensile niches. Lack of a deep foreland basin and lack of evidence for massive erosion argue against high-relief mountain belts caused by significant crustal shortening. Paleozoic rocks metamorphosed at pressures far in excess of stratigraphic burial are restricted to narrow lenses exhumed during Late Cretaceous and Tertiary extension and are bordered by rocks that always have been part of the shallow crust. The abundant shallow-crustal rocks preserved across the region indicate that a conventional hypothesis of large-scale, regional crustal thickening causing many kilometers of surface uplift and consequent erosion is unlikely to have taken place in the Mesozoic.

Little is known for certain about early Wisconsin (isotope stage 4) lakes and glaciers of the Great Basin. A moderate lake-level rise in the Bonneville basin is not well dated, but on the basis of amino-acid and radiocarbon ages, is thought to be early Wisconsin in age. A moderate rise of lakes in the basins of Lake Lahontan is dated as ca. 50 ka by U-series ages on tufa, but may have occurred earlier. In the southern Great Basin, Searles Lake fluctuated at levels below the threshold connecting it with Panamint Valley, and Panamint Valley apparently did not contain a large lake during the early Wisconsin. The glacial record is even less-well dated than the lacustrine record. The extent of glaciers in and around the Great Basin during the early Wisconsin is not known; ice extent was certainly greater than at present, but probably was less than the late Wisconsin maximum in most glaciated valleys. Further work is necessary to refine lacustrine and glacial chronologies, and to investigate the causes of lake vs. glacier expansion. Important clues to these questions will come from detailed studies of lacustrine and glacial sequences in different parts of the Great Basin.