Magnetic anomaly patterns on Mid-Atlantic Ridge crest at 26°N

Magnetic anomalies over ocean crust with ages between 0 and 3.5 m.y. B.P. have been identified on the Mid-Atlantic Ridge crest at 26°N. These anomalies indicate a spreading rate of 1.1 cm/yr on the west flank of the ridge and 1.3 cm/yr on the east flank. Computer modeling of the anomalies has shown that simple blocks of uniform thickness, whose width and direction of magnetization are obtained from the reversal time scale and whose intensities are chosen for best visual fit of the anomaly, are not capable of explaining the details of the observed magnetic anomalies. Shorter-wavelength variation in the intensity of magnetization parallel to the ridge crest can, however, explain the observed anomalies. A possible degradation of the intensity of magnetization within the axial anomaly is associated with large faulted blocks in the wall of the rift, which is the site of the Trans-Atlantic Geotraverse (TAG) hydrothermal field. Magnetic anomaly data suggest that extensive rotation of blocks within the rift valley is not likely.