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Figure 3.12. The geomagnetic-reversal timescale for the last 80 Ma as proposed in
1968. The magnetic-anomaly profiles with their model profiles and model reversal
sequences are shown for the South Atlantic, North Pacific and South Pacific. The
South Atlantic timescale was made by assuming that the spreading rate there has
been constant for the last 80 Ma. In comparison, spreading in the Pacific has clearly
been both faster and more irregular (note the different distance scales for the Pacific
data). Dashed lines connect specific magnetic anomalies numbered as in Fig. 3.14.
(After Heirtzler et al. (1968).)
3.2.2 Calculation of marine geomagnetic anomalies
The marine magnetic-anomaly patterns (e.g., Figs. 3.10 and 3.12) can give imme-
diate values for the relative motion between two plates if specific anomalies can be
identified and if the reversal timescale is known. The patterns can also be used to
estimate the relative motion between the plate and the Earth's magnetic pole. This
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