EXTENSION, MAGMATISM, SEGMENTATION AND SUTURES ON THE EASTERN NORTH AMERICAN MARGIN: PREVIOUS WORK AND OPPORTUNITIES FOR EARTHSCOPE AND GEOPRISMS (Invited Presentation)

Studies of rifts and rifted margins document remarkable variability in the volume and distribution of magmatism, the apparent association between rifting structures and pre-existing lithospheric structural and compositional heterogeneity, and the structure of the rift at a variety of scales. This variability is observed between different rifts as well as within individual extensional systems, where changes are apparent between conjugate margins, along-strike and with depth. The eastern North American rifted margin exemplifies these global variations. Here, we will present previous work on this margin, and highlight several long-standing questions raised by these previous studies that can be uniquely addressed by GeoPRISMS and Earthscope investigations on this margin.

Existing onshore and offshore geophysical and geological data indicate that the eastern margin of North America encompasses the full spectrum of rift-related magmatism, from voluminous magmatism off the east coast of the US to magma-poor rifting off Newfoundland and northern Nova Scotia. These variations in magmatism are accompanied by large changes in the style of rifting and the resulting rifted margin. The eastern North American margin also contains significant pre-existing structural and compositional heterogeneity imparted by a series of continental amalgamation and rifting events since Paleozoic, which also may have influenced the evolving rift. Potential fields data also hint at smaller scale along-strike variations that might be related to segmentation of the margin.

However, existing data leave many fundamental aspects of rifting here (and elsewhere) unanswered. 1) What was the role of magmatism in rifting, and what is the resulting distribution of deformation, magmatism and associated depletion throughout the crust and mantle lithosphere beneath rifts; 2) How does segmentation evolve from rift basins onshore to the successfully rifted margin to the mid-ocean ridge; and 3) How are sutures and other structural and compositional heterogeneity manifest through the lithosphere and how do they influence rifting? Substantial progress on many of these questions can be made through Earthscope investigations of the East Coast of the US.