Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply

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Science  16 Oct 2015:
Vol. 350, Issue 6258, pp. 310-313
DOI: 10.1126/science.aad0715
  • Fig. 1 Abyssal hill fabric formed at the intermediate-spreading Chile Ridge.

    Bathymetry of a segment of the intermediate-spreading Chile Ridge (29) located at 39°12'S, 91°30'W (white star), looking south. Beneath is a schematic cross section showing the major tectono-magmatic processes that shape the seafloor as melt supplied from below is emplaced as new oceanic crust.

  • Fig. 2 Seafloor topography from static compensation mechanisms.

    (A) Bathymetric relief created in response to oscillations in crustal thickness on a given wavelength, assuming three different effective elastic thicknesses (Te) for the lithosphere. Relief amplitude is given in percentage of the isostatic end-member (black axis) and in meters, assuming a crustal thickness fluctuation of 600 m and a density of 3000 kg m−3 for the oceanic crust (green axis). Red arrows indicate the seafloor wavelengths corresponding to Milankovitch periods for a spreading half-rate U = 3 cm/year. (B) Crustal thickness fluctuation (Δh = ΔhUC + ΔhLC) resulting from emplacement of a melt flux oscillating by ΔΦ0, within a zone of width w, on a period τ. Green axes (dimensional) illustrate the case where U = 3 cm/year and w = 1 km. Black axes are normalized.

  • Fig. 3 A tectono-magmatic interaction model for the spacing of abyssal hills.

    (A) Abyssal hill spacing data obtained from various studies of MOR bathymetry: diamonds (3), plus signs (21), stars (30), crosses (31), squares (32), and circles (33); US, SS, IS, and FS: ultraslow-, slow-, intermediate- and fast-spreading ridges, respectively. Green, red, and orange curves show model predictions corresponding to estimates of M versus spreading rate shown as inset and calibrated on measurements [circles, (25), with error bars indicating the full range of uncertainty in the determination of M from bathymetric profiles]. Blue lines illustrate spacing controlled by Milankovitch periods. (B) Schematic cross section showing the basic cycle of fault growth interacting with dike injection at the ridge axis (12).

  • Fig. 4 Sensitivity of MOR bathymetry to fluctuating dike injection rates.

    (A) Bathymetry obtained from numerical models of sequential faulting interacting with intermittent magma emplacement on an imposed period τ, amounting to a time-averaged M = 0.85 over 1.1 million years. (B) Whitened power spectral density (PSD) of modeled profile a2 (first 20 km to the right of the ridge axis). Blue dashed line shows measured fault spacing; red lines show Milankovitch wavelengths. (C) Spacing of modeled faults versus imposed period of magmatic fluctuations. Red and blue lines show the predictions of scaling laws and a linear relation between spacing (S) and τ, respectively.

Supplementary Materials

  • Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply

    J.-A. Olive, M. D. Behn, G. Ito, W. R. Buck, J. Escartín, S. Howell

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Figs. S1 to S3
    • References

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