Date of Completion
intraplate magmatism; hotspot; paleostress analysis; normal faulting; edge-driven convection
Dr. Jean M. Crespi
Dr. Timothy B. Byrne
Dr. Julie C. Fosdick
Field of Study
Doctor of Philosophy
The passive eastern North American margin has undergone episodes of intraplate magmatism, normal faulting, and uplift, yet driving mechanisms are not well understood. The Early Cretaceous magmatism of the New England-Quebec (NEQ) igneous province is a well-known example of postrift magmatism along the margin. Sheet intrusions and small plutons of the New England NEQ are concentrated in western Vermont and eastern New York and geographically associated with mesoscale normal faults. Traditionally, the NEQ has been attributed to the Great Meteor hotspot or reactivation of structurally weakened lithosphere. Recent work on Cretaceous uplift across New England, however, has pointed toward edge-driven convection as a driving mechanism for the uplift, and geophysical observations indicate the process of edge-driven convection is occurring beneath New England today. The research presented in this dissertation evaluates edge-driven convection as a potential driving mechanism capable of explaining the observations of postrift magmatism and normal faulting in western Vermont and eastern New York. Geochronological and geochemical data for the NEQ of western Vermont and eastern New York were obtained to understand the timing and characteristics of the Early Cretaceous magmatism. To investigate the potential crustal expression of edge-driven convection, the Early Cretaceous stress field was characterized using paleostress inversion of mesoscale fault-slip data. 40Ar/39Ar and U–Pb LA-ICP-MS geochronology for the sheet intrusions and Cuttingsville complex indicates magmatism was episodic and spanned at least 35 m.y. over a distance of ~100 km. Trace element and rare earth element signatures of the alkaline magmatism indicate a common source for the magmatism through time. Paleostress inversion of mesoscale fault-slip data, analysis of sheet intrusion geometry, and field observations indicate N–S and NW–SE extension occurred in association with magmatism as perturbations to the regional NE–SW extensional stress field. Timing is constrained by crosscutting relationships and the compatibility of the stress fields associated with normal faulting and sheet intrusion geometry. The geochronological and geochemical results are inconsistent with a hotspot origin and best explained by edge-driven convection while the normal faulting and extensional events are interpreted as the crustal expression of edge-driven convection.
Cooper Boemmels, Jennifer, "Postrift Development of the Eastern North American Margin: Early Cretaceous Intraplate Magmatism and Normal Faulting of Western Vermont and Eastern New York" (2020). Doctoral Dissertations. 2609.
Available for download on Sunday, August 06, 2023