Collision of Yap-Palau arcs with 

 Caroline Ridge and Basin at 24 Tii.y. B.F, 

 halts subduction and rifting at ridge. 

 Shift of Pacific-Philippine margin to 

 Caroline-Pacific margin. 



Pliocene opening of 

 Mariana Trough 



Caroline- 



acific plate 

 margin 



Final pulse of 

 basin and inner-arc 

 \ spreading 14.5- 

 \12.5 m.y. B.P. 



Neogene opening 

 ^ of Ayu Trough 



Neogene opening of Bis- 

 marck Sea and Northwest move- 

 ment of Manus Arc 



Upper Miocene 

 subduction boun- 

 dary shifts to 

 interior New 

 Guinea later. 



(Approximate scale 1:16,000,000) 



Figure 19. Evolution of the Caroline region: 24-0 m.y. B.P. 



70 



