(Ridley and others, 1974). That this area may have an unusual thickness 

 of layer 2 crust is indicated by the results of a reversed seismic 

 refraction profile shot nearby (at 8.7°N/143°E) by Gaskell and others 

 (1958) . This profile indicates a layer 2 thickness in excess of 4 km. 

 Ridley and others point out that this basalt flow may mask older oceanic 

 crust and sediments (possibly Jurassic) on the northern Caroline Ridge 

 and in the area to the north. 



Bracey and Andrews (1974) proposed that the Sorol Trough is an 

 extinct inter-arc basin formed behind the northward dipping trench 

 system at the northern Caroline Basin margin; coeval with the Oligocene 

 spreading. 



Weissel and Anderson (1978) felt that the Sorol Trough is an active, 

 obliquely-opening transform feature representing the present northern 

 boundary between the Pacific and Caroline plates, a view shared by 

 Hamilton (1979). 



Vogt and others (1976) attribute the Caroline Rise to westward 

 movement of older ocean crust over a Neogene mantle plume, a view 

 similar to that proposed by Clague and Jarrard (1973). The rise sub- 

 sequently blocked the Yap-Mariana Trench system, and the Sorol trough 

 formed as a result of the "incipient breakup of the Pacific Plate." 



It is difficult for this author to understand why a transform plate 

 boundary should form along the center of one of the most massive features 

 in the southwest Pacific. Why did it not form instead along the southern 

 flank of the ridge where the extinct trench provided a pre-existing zone 



58 



