Transitional crust in the Newfoundland-Iberia rift and associated magnetic anomalies

International audienc

Continental breakup and the onset of ultra-slow seafloor spreading off Flemish Cap on the Newfoundland Rifted Margin

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

Data report: Marine geophysical data on the Newfoundland nonvolcanic margin around SCREECH transect 2

Marine geophysical data collected from the eastern Grand Banks across the Newfoundland Basin during the summer of 2000 comprise a grid of seismic, magnetic, gravity, and multibeam bathymetric data around Sites 1276 and 1277. Multichannel seismic reflection profiles image the sedimentary and crustal structure of the Newfoundland nonvolcanic rifted margin. This report presents prestack time-migrated seismic reflection profiles together with the coincident magnetic and gravity data collected during the site survey