p-wave velocity of 6.98 km/sec) oceanic crust, as opposed to the 4 

 km thickness of layer 3 crust in the adjacent basins. 



Figure 14 contrasts bathymetric (plotted from Fig. 2) and gravity 

 profiles over the Eauripik Rise and the eastern part of the West 

 Caroline Trough, which through magnetic anomaly identification has 

 been shown to be an extinct spreading center since about 27 m.y. B.P. 

 The Eauripik Rise Bouguer gravity profile shows a broad negative over 

 the rise typical of aseismic oceanic rises isostatlcally compensated 

 by underlying mass deficiencies. See for example: Goslin and Sibuet 

 (1975) ; Bowin (1973) . This compensation is in complete agreement with 

 the seismic results of Den and others (1971) . The West Caroline 

 Trough Bouguer anomaly exhibits no such low. 



When compared to the thermal contraction model curve for oceanic 

 crust, which predicts crustal age as a function of depth (for example: 

 Parker and Oldenburg, 1973), the depths of the crust adjacent to the 

 West Caroline Trough (4.24 km) plot at about 25 m.y. B.P., in good 

 agreement with the magnetic age. On the other hand, the crustal depth 

 at the Eauripik Rise ( 2 km) yields an age of less than 1.0 m.y. B.P., 

 in complete disagreement with the DSDP Site 62 minimum age determina- 

 tion of 26 m.y. B.P. (Winterer and others, 1971). 



Mammerickx (1978) discounted the results of Den and others (1971) 

 and following Winterer and others (1971) , proposed that the rise is 

 an inactive (since 26 m.y. B.P.) spreading center. The facts cited 

 above, and the additional fact that the recognized east-west trending 

 magnetic anomalies extend from the East Caroline Basin onto the flanks 



46 



