Compressional and shear-wave velocity structure of the continent-ocean transition zone at the eastern Grand Banks, Newfoundland

Authors

  • Drew R. Eddy,

    Corresponding author
    1. University of Texas Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA
    • Corresponding author: D. R. Eddy, University of Texas Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78754, USA. (drew.eddy@utexas.edu)

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  • Harm J. A. Van Avendonk,

    1. University of Texas Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA
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  • Donna J. Shillington

    1. Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA
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Abstract

[1] The seismic structure of the continent-ocean transition (COT) at magma-poor rifted margins can explain geological processes leading to continental breakup. At the Newfoundland-Iberia rift, compressional seismic velocity (Vp) is interpreted with multichannel seismic reflections and drilling results to document continental crustal stretching and thinning, exhumation of the mantle, and incipient seafloor-spreading. However, Vp cannot uniquely constrain COT geology. We present an updated 2-D model for Vp and a new shear-wave velocity model (Vs) for SCREECH Line 2 on the Newfoundland margin using multichannel seismic reflections and coincident ocean-bottom seismometer refraction data. In shallow COT basement we find Vp / Vs ratios average 1.77, which is normally too high for upper continental crust and too low for serpentinized mantle. This observation can be explained by stretching of a mafic middle and/or lower continental crust into the COT. We further support the presence of hydrated mantle peridotites at depth during rifting.

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