. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography McGregor et al.: Magnetics Mid-Atlantic Ridge 235 PROFILE 14. 0 10 20 30 40 50 60 70 DISTANCE (KM) Fig. 6. Profile lA over TAG hydrothermal field (see Figure 2 for location). (a) Measured bathymetry. (b) Computer-simulated bathymetry, (c) Measured magnetic anomaly. (d) Computer- generated magnetic anomaly. A 500-m magnetized layer is assumed (b) with numbered unshaded blocks representing reversed material. Shaded blocks are normally magnetized, with
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography McGregor et al.: Magnetics Mid-Atlantic Ridge 235 PROFILE 14. 0 10 20 30 40 50 60 70 DISTANCE (KM) Fig. 6. Profile lA over TAG hydrothermal field (see Figure 2 for location). (a) Measured bathymetry. (b) Computer-simulated bathymetry, (c) Measured magnetic anomaly. (d) Computer- generated magnetic anomaly. A 500-m magnetized layer is assumed (b) with numbered unshaded blocks representing reversed material. Shaded blocks are normally magnetized, with 1 repre- senting the axial anomaly. Width of blocks is based on a spreading rate and the Talwani et al. [1971] magnetic chronology. Underlined values arc intensities of remanent magnetization in amperes per meter. Bathyraetric peak between 35 and 40 km is the region where hydrothermal manganese is present. with the median ridge, but occasionally a slight increase occurs, such as in profiles 2, 4, and 10. The median ridge and the axis line indicate that the present-day active zone of spreading is not centered in the Brunhes normal epoch but is much closer to the western boundary. Although asym- metric spreading appears to be occurring in the area of the Atlantic at 26°N, the degree of asymmetry implied by the position of this axis is not s'jpi^orted by the spreading r^ff - This la'ge asymmetry supports the suggesticr. that injection of new material occurs over an area in the rift zone that is several kilometers wide. From the magnetization it can be seen that the west wall of the rift is slightly older than the east wall. A spreading rate of cm/yr for the west side and cm/yr for the east side fits the data from 0 to The spreading rates were determined by measuring the width of the Matuyama epoch on each side of the ridge. Matching of anomaly wavelengths in the forward n-.;thod supports these asymmetric spreading rates. Averaging to 10 , Lattimore
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