Recently reprocessed aeromagnetic data reveal the slow-spreading Kolbeinsey Ridge underwent a regional axial reorganization at anomaly 3A time that signaled a major change in the segmentation behavior of the spreading center. Prior to anomaly 3A, the axis was a sinuous but essentially continuous feature. The anomaly 3A event separated the axis into four segments, created wide nontransform offsets, and established axial strikes more nearly orthogonal to the spreading direction. In the succeeding ∼5.5 m.y., the axis continued to evolve by ridge propagation, asymmetric spreading, and lateral ridge migration caused by either ultrafast propagation or synchronous ridge jumps. These data suggest that the brief perturbation of axial structure at anomaly 3A time may have altered the long-term segmentation behavior of the ridge. The mechanism for the ridge's segmentation and the ridge's post-segmentation behavior indicate styles of axial reorganization that may be significant on slow-spreading centers globally.

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