Structure of the Flemish Cap margin, Newfoundland:Insights into mantle and crustal processes during continental breakup

• Published in: Geological Society, London, Special Publications
• Main Authors: Hopper, J. R., Funck, T., Tucholke, B. E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2007
• Subjects: Newfoundland
• Online Access: https://curis.ku.dk/portal/da/publications/structure-of-the-flemish-cap-margin-newfoundland(777c8620-8042-486c-b61d-81d1af215852).html; https://doi.org/10.1144/SP282.3; http://www.scopus.com/inward/record.url?scp=34548261870&partnerID=8YFLogxK

Seismic reflection and refraction data from the Flemish Cap margin off Newfoundland reveal the large-scale structure of a magma-starved rifted margin. There is little evidence for significant extensional deformation of the Flemish Cap, consistent with the hypothesis that it behaved as a microplate throughout the Mesozoic. The seismic data highlight important asymmetries at a variety of scales that developed during the final stages of continental breakup and the onset of oceanic sea-floor spreading. In strong contrast to the conjugate Galicia Bank margin, Flemish Cap shows: (1) an abrupt necking profile in cointinental crust, thinning from 30 km thick to 3 km thick over a distance of 80 km, and a narrow, less than 20 km-wide, zone of extremely thin continental crust; (2) no clear evidence for horizontal detachment structures beneath continental crust similar to the 'S' reflection; and (3) evidence for at least a 60 km-wide zone of anomalously thin oceanic crust that began accreting to the margin shortly after continental crustal separation. The oceanic crust averages only 3-4 km thick and in places is as thin as 1.3 km thick, although seismic layer 3 is missing where this occurs. The data suggest that there are large spatial and temporal variations in the available melt supply following continental breakup as oceanic sea-floor spreading becomes established. In addition, wide-angle data show that anomalously slow mande P-wave velocities appew approximately where continental crust has thinned to 6-8 km thick, indicating that low-degree serpentinization begins where the entire crust has become embrittled.