The Eastern North American Margin (ENAM) represents the final product of continental rifting to form a passive margin, and records the full history of rift evolution and post-rift processes. The ENAM encompasses large variations in fundamental rift parameters, including the volume of magmatism, the pre-existing lithospheric template, and the duration of rifting. In particular, rifting along the southeastern United States was associated with voluminous magmatism, whereas the northernmost portion of this margin offshore of Nova Scotia and Newfoundland is distinctly magma-poor. ENAM also captures an extensive post-rift evolution of the passive margin sedimentary prism as well as the cooling and further evolution of the mantle lithosphere below. Finally, there are further compelling logistical benefits to studying ENAM, including the leveraging of considerable US infrastructure, including Earthscope (in particular, upcoming USArray deployments), and the USGS Law of the Sea survey activities.
From the Science Plan
Examples oustanding research questions that could be addressed at along the Eastern North American Margin include:
- How was deformation distributed throughout the lithosphere on the Atlantic Margins, and how was it influenced by magmatism and preexisting structural and compositional heterogeneity?
- How does rift structure and magmatism vary within and between segments along the ENAM?
- How do mantle dynamics influence the syn- and post-rift evolution of the margin?
- What processes accompanied the transition from late-stage rifting to mature seafloor spreading? How has the margin been influenced by post-rift tectonics?
- What controls the large-scale form of the passive margin?
- What are the magnitudes, mechanisms, and timescales of elemental fluxes between the Earth, oceans, and atmosphere along a passive margin during and after rifting?
- Is post-rift passive margin morphology self-regulating?
- What are the scales and frequency of submarine landslides, and what preconditions and triggers landslides?
The Joint EarthScope-GeoPRISMS Planning Workshop for the Eastern North American Margin (ENAM) was held at Lehigh University in Bethlehem, PA from October 26-29, 2011. This workshop brought together researchers working from both communities to articulate research priorities in the region. A group of about 100 attendees took part, including 11 graduate students. An important goal of the workshop was to focus the broader community effort on cross-disciplinary learning and approaches to collaborative science dedicated to the science topics embodied in the archetypal passive margin. The workshop provided a national and international forum of scientists from universities, national laboratories, federal and state agencies, and industry.
During the workshop, the community identified a series of corridors or focus areas within which GeoPRISMS research is to be focused:
- Southern Focus Area (Charleston)
- Central Focus Area (Richmond - Philadelphia)
- Northern Focus Area (Nova Scotia)
The Implementation Plan for the Eastern North American Margin has been updated following the outcomes of the workshop, and is available for download.
ENAM Community Seismic Experiment
There is presently discussion about a large-scale geophysical expedition along the Eastern North American Margin. For more information, see the ENAM Community Seismic Experiment page.
The imminent arrival of the EarthScope transportable array (TA) and selection of the Eastern North American Margin (ENAM) as a GeoPRISMS primary site, are defining exciting new research opportunities along this margin. In addition, the USGS is responsible for coordinating the collection of seismic data along the eastern seaboard as part of the US Extended Continental Shelf Project under the UN Convention on the Law of the Sea. Tentatively, USGS surveys in the ENAM area will take place in 2013 using the R/V Langseth seismic vessel, providing potential opportunities for piggy-back experiments.
This convergence of interest in ENAM, and the presence of the R/V Langseth in Atlantic waters, offers a unique opportunity to conduct a community seismic experiment along the ENAM, benefiting a large number of researchers, especially students and early-career investigators. Improved seismic imaging of the margin, both shallow and deep, onshore and off, would address a wide range of GeoPRISMS and related research objectives. It can yield a backbone dataset for studying the deep structure of the margin, its structural and stratigraphic architecture, ongoing geodynamic processes, economic potential, and many other aspects.
Articles and Research
- GeoPRISMS Community Seismic Experiment along the ENAM Luncheon (AGU, Dec 8, 2011)
- EarthScope-GeoPRISMS Science Workshop for the Eastern North America Margin (Bethlehem, PA, October 26-29, 2011)
- ENAM Mini-Workshop (Bastrop, TX, January 5-7, 2011)
- RIE Implementation Workshop (Santa Fe, NM, November 4-6, 2010)