Of the three diverse (shallow and intermediate depth) epicenters 

 scattered along the eastern margin of the Caroline Basin, one mech- 

 anism determination has been made by Weissel and Anderson (1978) . 

 Although somewhat ambiguous, the solution did indicate maximum hori- 

 zontal stress along a NE-SW axis. 



Magnetic Anomalies 



The magnetic anomaly data are fundamental to any interpretation of 

 the age and tectonic history of the Caroline Basin. It is fortunate 

 that the results of the DSDP (Winterer and others, 1971) allow a Mid 

 to Upper Tertiary time "window" to be applied to the model anomaly 

 profiles to which the observed data must be compared in order to estab- 

 lish the age sequence in the basin. 



Figure 8 compares observed total intensity anomaly profiles in the 

 West Caroline Basin to anomalies computed from a sea-floor spreading 

 reversal model (LaBrecque and others, 1977). In the eastern part of 

 the basin, anomalies are identified from 13 (36 m.y.) in the south to 

 the extinct spreading axis at~27 m.y. B.P. expressed by the West 

 Caroline Trough as predicted by Mammerickx (1978). North of the 

 trough, only anomaly 9 is found, which, assuming symmetric and con- 

 tinuous spreading from this axis, would confirm the hypothesis of 

 Bracey and Andrews (1974) that the troughs along the southern flank of 

 the Caroline Ridge represent the remnants of an extinct subduction 

 zone. 



At the western side of the basin a symmetric anomaly correlation 

 (Fig. 8, profiles 1, UHl, UH2, 2, 3) about the seismically defined 



24 



