TECTONIC SYNTHESIS 



Caroline Basin 



Figure 12 is a summary areal display of the magnetic model studies 

 of Figures 8 and 9. Fracture zones (F.Z.) are required by the relative 

 offsets of the anomaly patterns as shown in the above figures. They are 

 drawn normal to the anomaly strike as would be required if they are the 

 result of transform faulting between spreading-ridge segments (Menard 

 and Atwater, 1968). Note that their crossings of the seismic reflection 

 profiles (Figures 4 and 7) are usually marked by features that could 

 conceivably be interpreted as fractures or fracture zones, but the ambi- 

 guity of this evidence, as well as the exact strike of the fracture 

 zones is emphasized. It is further emphasized that the sparsity of data 

 may also mask other small-scale complexities not depicted here. 



While it is apparent from Figure 12 that the two sub-basins have 

 had a similar mode of occurence (sea-floor spreading) , their evolution 

 was by no means identical. Spreading appears to have commenced in both 

 basins at some time prior to anomaly 13 time (>36 m.y. B.P.) along ENE 

 oriented spreading axes (with the notable exception of the area between 

 F.Z. 4 and F.Z. 8, where the spreading direction is more nearly E-W) , 

 and progressed at a relatively constant over-all spreading half-rate of 

 6.0 - 6.5 cm/yr (with another notable exception in the eastern part of 

 the West Caroline Basin noted above) until sometime after anomaly 11 

 time ("'31 m.y. B.P.). At this time spreading apparently ceased (or 

 slowed) at the western side of both basins but continued at the eastern 

 sides, ending after anomaly 9 ('^27 m.y. B.P.) time in the eastern part 



37 



