Abstract
The configuration of accreting plate boundaries tends to reflect the geometry of the original continental break-up, yet there are also many indications that the detailed pattern of spreading-ridge and transform-fault segments may be an inherent part of the spreading process itself1,2. The Mid-Atlantic Ridge, for example, is segmented, with a typical spacing of ∼40 km between transform faults3,4. Here, we use the short-wavelength (25–110 km) part of the Seasat altimetry data set to derive a map of the 'geoid rough-ness' in the South Atlantic between 1° N and 39° S. This map reflects changes in the local amplitude (envelope) of the geoid signal primarily associated with topography. Zones of high roughness correlate with major fracture zones, aseismic ridges and the Mid-Atlantic Ridge. The most remarkable feature is that the roughness is not uniform along the ridge but displays quasi-periodic variations with a wavelength of ∼400 km, a segmentation an order of magnitude larger than described so far, which has persisted for at least 60 Myr. This segmentation may reflect either fabric generated at the ridge by normal plate tectonic processes1,5, or small-scale convective instabilities rising from ∼80-km-deep region of the upper mantle3,6,7
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Gibert, D., Courtillot, V. Geoid roughness and long-wavelength segmentation of the South Atlantic spreading ridge. Nature 333, 255–258 (1988). https://doi.org/10.1038/333255a0
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DOI: https://doi.org/10.1038/333255a0
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