Continental break-up and the onset of ultraslow seafloor spreading off Flemish Cap on the Newfoundland rifted margin

John R. Hopper, Thomas Funck, Brian E. Tucholke, Hans Christian Larsen, W. Steven Holbrook, Keith E. Louden, Donna Shillington, Helen Lau

Research output: Contribution to journalArticlepeer-review

129 Scopus citations


Prestack depth-migrated seismic reflection data collected off Flemish Cap on the Newfoundland margin show a structure of abruptly thinning continental crust that leads into an oceanic accretion system. Within continental crust, there is no clear evidence for detachment surfaces analogous to the S reflection off the conjugate Galicia Bank margin, demonstrating a first-order asymmetry in final rift development. Anomalously thin (3-4 km), magmatically produced oceanic crust abuts very thin continental crust and is highly tectonized. This indicates that initial accretion of the oceanic crust was in a magma-limited setting similar to present-day ultraslow spreading environments. Seaward, oceanic crust thins to <1.3 km and exhibits an unusual, highly reflective layering. We propose that a period of magma starvation led to exhumation of mantle in an oceanic core complex that was subsequently buried by deep-marine sheet flows to form this layering. Subsequent seafloor spreading formed normal, ∼6-km-thick oceanic crust. This interpretation implies large fluctuations in the available melt supply during the early stages of seafloor spreading before a more typical slow-spreading system was established.

Original languageEnglish (US)
Pages (from-to)93-96
Number of pages4
Issue number1
StatePublished - Jan 2004
Externally publishedYes


  • Continental breakup
  • Continental margin
  • Extension tectonics
  • Seafloor spreading

ASJC Scopus subject areas

  • Geology


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