The nature of the ocean-continent transition on the Newfoundland rifted margin: Results from detailed tomographic imaging of the crust
Abstract
The crustal structure of rifted margins holds important clues to the mode of extension and break-up before ocean-spreading commenced. The transition from thinned continental crust to normal oceanic crust (OCT) occurs over 50-150 km on most nonvolcanic rifted margins, and recent seismic studies on the Iberian and Newfoundland margins have shown that the nature of the OCT can vary over short (~100 km) distances along the strike of the margin, and large differences have also been noted between conjugate margin pairs. Some OCTs show seismic velocities near the Moho of 7.1 to 7.4 km/s that have been attributed to magmatic underplating and subcrustal serpentinization, but these intermediate velocities appear absent on others. The fitting of the Grand Banks and Iberian margins (Shillington et al., this meeting) illustrates that this complexity can be explained by asymmetric rifting once the crustal structure has been determined with sufficient detail. However, it can be difficult to distinguish between the seismic velocity structure of thinned continental crust and newly formed oceanic crust even with great quality seismic refraction and reflection data. We illustrate the slight variation in P-wave velocity across the OCT in the middle of three seismic refraction/reflection transects that were collected offshore Newfoundland during the SCREECH experiment in the summer of 2000. Given the importance of small scale variations of <0.2 km/s in crust with P velocity of ~6.2 km/s it becomes increasingly more important to provide good error bounds with the tomographic inversions that produce these results.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.T52C1216V
- Keywords:
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- 8105 Continental margins and sedimentary basins;
- 8159 Rheology: crust and lithosphere;
- 8180 Tomography