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.

The Central Maine Terrane (CMT) includes the rocks that extend northeasterly from Connecticut to Maine and from the Monroe Fault on the west to the Campbell Hill-Nonesuch River Fault Zone on the east. A four-phase sequence of Acadian regional deformation is recognized for the CMT cover sequence. D 1 , the earliest phase, is characterized by F 1 nappes that have east or west vergence; the sense of vergence switches at the Central New Hampshire anticlinorium (CNHA). D 1 is also characterized by early, rarely observed, low-angle and “blind” T 1 thrust faults. The CNHA (or “dorsal zone”) is analogous to a “pop up” structure and is the likely root zone for both east- and west-verging Acadian D 1 thrust-nappes. D 2 is characterized by abundant F 2 tight to isoclinal, inclined to recumbent folds with northeast-trending axes and east-southeast vergence. Most of these folds face downward, a reflection of D 2 refolding the inverted limbs of D 1 structures, and these structures are identifiable chiefly in eastern New Hampshire. F 2 folds define a regional map-scale fold, the Lebanon antiformal syncline. During D 3 broad, open, upright to inclined F 3 folds with west- or northwest-trending axes were developed across the entire belt. F 3 map-scale syntaxial folds are well defined by the outcrop pattern of the metasedimentary rocks. D 4 , the last phase of deformation, is characterized by F 4 , tight to isoclinal, inclined folds with north-northeast-trending axes and east vergence and is restricted to the western part of the CMT. F 4 folds refolded the earlier structures and significantly modify the map pattern, tightening some of the earlier major structures in the CMT, for example the Kearsarge-Central Maine synclinorium. D 2 and D 4 are similarly oriented but spatially and temporally distinct. Deformation phases D 1 through D 4 are geographically restricted. This uneven distribution of structures is critical to correlations of deformation sequences across the orogen. Any local sequence of deformation in the CMT of central New Hampshire will commonly have only three of the four regional phases preserved in outcrop.