EXPLORING THE CRUSTAL EXPRESSION OF EDGE-DRIVEN CONVECTION WITHIN THE PASSIVE MARGIN SETTING: AN EARLY CRETACEOUS EXAMPLE FROM THE NORTHERN APPALACHIANS

Recent advances suggest that shallow-mantle processes such as edge-driven convection play an important role in shaping and modifying the passive margin setting. In northern New England, the Northern Appalachian Anomaly has been interpreted as evidence for ongoing edge-driven convection beneath the margin today (Menke et al., 2016; Dong and Menke, 2017; Levin et al., 2018; Menke et al., 2018). In western Vermont and eastern New York, Early Cretaceous magmatism at ~140-130 Ma and ~110-100 Ma is likely an upper-crustal expression of edge-driven convection beneath the eastern North American margin (Cooper Boemmels et al., 2021).

The two episodes of Early Cretaceous magmatism in western Vermont and eastern New York occurred within an extensional setting and both were associated with normal faulting and local changes in extension direction. Crosscutting relationships and stress field compatibility between sheet intrusions and fault-slip data indicate normal faulting coincided with and likely continued following magmatism. Both events corresponded to a short-term change from regional NE-SW extension direction.

Similar to the magmatism, the short-term changes in extension direction observed in northern New England are likely the crustal expression of edge-driven convection. Geodynamic modeling suggests edge-driven convection occurs periodically (Kaislaniemi and van Hunen, 2014). In addition, geodynamic modeling and geophysical observations suggest small-scale delamination is often associated with the process of edge-driven convection (Kaislaniemi and van Hunen, 2014; Dong and Menke, 2017). Modeling has also shown extension and/or contraction can occur within the upper crust depending on the characteristics of the lithosphere and nature of detachment (Göğüs, and Pysklywec, 2008; Pysklywec and Cruden, 2004). In northern New England, the magmatism, geographic and temporal scale of the stress field changes, and return to regional NE-SW extension following these events, are consistent with the periodic nature of edge-driven convection and associated small-scale delamination events.