STACKING MARINE MAGNETIC ANOMALIES: A CRITIQUE

It is shown that the procedure of summing (stacking) together a number of surface magnetic anomaly records does not significantly improve the ultimate resolution of short events in the geomagnetic polarity sequence. The limit of resolution (shown elsewhere to be about 3 km for surface data) is determined by the presence of signals not originating in the crust. Single profiles will not usually attain this optimal resolution, however, because of geological irregularities in the magnetic layer. Therefore, stacking offers improvement at longer wavelengths, but not all unwanted effects are properly suppressed: for example, (a) bathymetric features can cause coherent signals in closely spaced surveys and stacking will amplify them; (b) the stacking of phase-shifted anomalies causes smoothing rather than sharpening of transitions.