A Neogene Chronology of Iceland Plume Activity from V-Shaped Ridges

• Published in: Earth and Planetary Science Letters
• Main Authors: Poore, H. R., White, N. J., Jones, S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2009
• Subjects: 02 - Geodynamics; Geophysics and Tectonics; Greenland; Reykjanes; Greenland-Scotland Ridge; Iceland; North Atlantic Deep Water; North Atlantic
• Online Access: http://eprints.esc.cam.ac.uk/874/; http://eprints.esc.cam.ac.uk/874/1/Poore_White_Jones_ESPL_2009.pdf; https://doi.org/10.1016/j.epsl.2009.02.028

The V-shaped ridges, which straddle the mid-oceanic ridges on either side of Iceland, are recognized as a window into transient convective circulation of the mantle. The geometry of these ridges places important constraints on the nature of asthenospheric flow within the head of the Icelandic plume. Associated changes in the bathymetry of the Greenland–Scotland Ridge may have modulated the overflow of North Atlantic Deep Water. In order to improve the Neogene chronology of these V-shaped ridges, we have re-analyzed a set of legacy seismic reflection profiles which cross the Reykjanes Ridge south of Iceland. After converting these profiles to depth, the sediment–basement interface was carefully picked and corrected for sediment loading. Ages were assigned using magnetic anomalies which were correlated to an astronomically tuned timescale. We then calculated the residual height of oceanic crust along each profile by removing components of long-wavelength subsidence which are caused by lithospheric plate cooling and by dynamic support of the plume. By correlating the pattern of residual height with free-air gravity anomalies, we can discriminate between the effects of normal faulting and crustal thickness variations. The pattern of residual height primarily reflects asthenospheric temperature fluctuations which flow away from the center of the Icelandic plume. If we assume that asthenospheric flow is radial, our results can be used to estimate the mass flux of the Icelandic plume which varies from 1–3 × 1014 kg/yr over the last 17 million years. Earlier, during Paleogene times, there is indirect evidence for higher mass flux. If the plume conduit beneath Iceland has a radius of 150 km, our inferred mass flux corresponds to an upwelling rate of 270 mm/yr. Finally, we have compared the Neogene record of residual height predicted for the Denmark Straits with estimates of the overflow of Northern Component Water, the Neogene precursor of North Atlantic Deep Water. There is a striking correlation between the two records over the last 5 million years which suggests that regional, plume-driven, vertical motion controlled deep-water overflow at the Denmark Straits.