Profile L-D 5 has the most clearly defined axial feature, both 

 morphologically and magnetically. It takes the form of an uplifted or 

 uparched block incised by an axial valley. Note that only on profiles 

 L-D 5 and 11 is there a definite indication of an increase in sediment 

 thickness in either direction from the proposed axis. 



The prominent block-like feature on profile 10 extending from 

 5.0° - 5.35 N is believed to be continuous with (connected by dashed 

 lines on Fig. 7) the feature located on either side of 5°N in profile 

 9. The distance between these two profiles is only 60 km at this 

 location (Fig. 2). This feature has a very deleterious effect on the 

 identification of magnetic anomalies as will be seen. 



The northern end of profile 11 shows evidence of the northern 

 Caroline Basin subduction margin proposed by Bracey and Andrews (1974) . 

 The resemblance of the features between 5 and 6°N to present-day 

 subduction zones is particularly striking. The feature on profile 

 L-D 5 at 6°N is not so analogous, although it does have analogy to 

 features identified by Bracey and Andrews (1974) as the western remnants 

 of the proposed subduction zone (their Fig. 4). An indication that this 

 feature, whatever its origin, forms the northern boundary of the basin, 

 is given by the sharp increase in sediment thickness to the north. 



Heat Flow 



The mean value of the 12 heat flow measurements in the Caroline 

 Basin, exclusive of those less than 0.5 HFU (discarded for reasons 

 discussed in detail by Sclater, 1972), is 2.11 + 0.69 (s.d.) HFU. 

 This is considerably higher than the mean 1.50 HFU value accepted as 



21 



