Early Cretaceous stress field variations and relationship to intraplate magmatism in the New England portion of the eastern North American margin

Abstract Shallow mantle processes such as edge-driven convection are thought to play an important role in shaping the passive margin setting. Previous geophysical investigations of northern New England suggest this process is likely operating beneath this portion of the eastern North American margin today. In western Vermont and eastern New York, USA, Early Cretaceous magmatism dated at ca. 140–130 Ma in the Burlington lobe and at ca. 110–100 Ma in the Taconic lobe of the New England–Quebec igneous province may represent the upper crustal expression of edge-driven convection operating beneath the eastern North American margin in the geologic past. This investigation addresses the potential relationship between these two episodes of magmatism and upper crustal deformation in northern New England through paleostress analysis of Early Cretaceous sheet intrusions and mesoscale normal faults, and geochemical analysis of sheet intrusions. The two episodes of magmatism are geochemically similar, display typical characteristics of intraplate alkaline magmatism, and are likely the product of a common source. Paleostress analysis and crosscutting relationships indicate that Burlington lobe magmatism was associated with a subhorizontal N–S extensional stress field, and Taconic lobe magmatism was associated with a subhorizontal NW–SE extensional stress field. Both stress fields represent short-term perturbations to the regional Early Cretaceous subhorizontal NE–SW extensional stress field. Each perturbation coincided with and likely continued following magmatism. The magmatism, geographic and temporal scale of the stress field changes, and return to regional subhorizontal NE–SW extension following these events are consistent with the periodic nature of edge-driven convection and associated small-scale delamination events. This field-based documentation of intraplate magmatism and its association with short-term changes in the stress field improves our understanding of the upper crustal expression of edge-driven convection at passive margins.