Relationship Between Magmatism and Extension Along the Eastern North American Margin (ENAM) From Onshore-Offshore Active Source ENAM Community Seismic Experiment Refraction Data
Abstract
Extensional tectonic forces alone are often not sufficient to explain how continental lithosphere ruptures to form oceanic lithosphere, suggesting the importance of other factors such as inherited structural weaknesses and magmatic addition. Understanding the distribution of magmatism during rift initiation and evolution as preserved in mature continental margins can help explore the connection between extension and magmatism throughout the continental breakup cycle. We use onshore-offshore active source seismic data collected in 2014-2015 as part of the NSF GeoPRISMS ENAM Community Seismic Experiment (CSE) along the mid-Atlantic coast in eastern North Carolina to determine crustal velocity structure of extended continental crust and the continent-ocean transition. Two margin-dip profiles were acquired using eleven onshore explosive-source shots, five on the northern profile and six on the southern profile, and recorded using 720 Reftek-125 seismometers deployed at 250 m intervals. Additionally, offshore airgun shots were recorded using 80 seismometers deployed onshore during offshore data acquisition. This experimental setup yields crustal refraction arrivals along each profile, Moho reflection arrivals at offsets greater than 100 km, Moho refraction arrivals at offsets greater than 180 km, and intracrustal reflection arrivals. Preliminary 2-D velocity models of each onshore profile reveal a crustal thickness between 35-40 km and a high velocity (>7.0 km/s) layer at the base of the crust. This feature may represent magmatic underplating that has only been previously observed offshore along the margin, and could be related to syn-rift magmatism along the ENAM or to the Central Atlantic Magmatic Province (CAMP). Incorporation of the onshore-offshore data allows us to determine the distribution and thickness of intrusive magmatic features within the ENAM, providing insight into the relationships between magmatism and extension during rift initiation and evolution.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.T51G3000L
- Keywords:
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- 8107 Continental neotectonics;
- TECTONOPHYSICSDE: 8110 Continental tectonics: general;
- TECTONOPHYSICSDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS