kap = 0.055. However, in order to produce model anomaly amplitudes 

 equal to the observed anomalies, a kap of 0.04 was required (Figs. 8 

 and 9). Assuming the values of Jn and k are correct, and representative 

 of the magnetic conditions in the basin, and assuming an increase in 

 the magnetized layer thickness used in the model computations is ruled 

 out (which may be unrealistic), then the earth's field value must be 

 increased to 0.54 Oe to reproduce the required kap of 0.04. This 70% 

 increase in F is further indication that the ambient field and the field 

 that produced the anomalies are quite different. 



Marshall (1978) also made paleolatitude determinations from the 

 basalt samples at DSDP Site 63. He found that the remnance direction 

 (Ir), after demagnetization, ranged from -43° to +3 , with a mean of 

 -8.0° + 7.8° (s.d.). Using the assumption that the earth's field was 

 largely dipolar, the corresponding paleolatitude is -4°. 



As pointed out by Marshall, there are serious limitations on the 

 accuracy of this latitude determination in addition to the wide angular 

 dispersal of Ir indicated by the 7.8° standard deviation. First, since 

 there was no azimuthal orientation of the DSDP cores, there is an ambi- 

 guity as to whether the latitude lies in the northern or southern hemi- 

 sphere. Secondly, Cenozoic secular variation may cause dispersion of the 

 Ir with a standard deviation of.+ 10 . This last effect can be mini- 

 mized by averaging the measurements. 



The only positive way of determining whether the Ir was acquired 

 in the southern hemisphere is to show that it is clearly associated 

 with normally polarized crust. A linear projection of Site 63 along the 



35 



