and relative left-lateral movement in northern New Guinea (for example: 

 Hamilton, 1979; Johnson, 1979). 



I agree with Bracey (1975) that an earlier (Oligocene-Miocene) 

 Caroline Plate boundary was probably composed of a single subduction 

 zone extending from Vogelkop eastward to a possible present-day expres- 

 sion of the northward directed subduction at New Britain, a pre- Eocene 

 arc (Johnson, 1979). Subduction polarity probably reversed on the west 

 after collision and initiated a period of obduction, beginning in late 

 Oligocene. The New Britain arc is now the sole survivor of the earlier 

 north directed subduction. 



Inner-arc spreading subsequently split New Britain, creating the 

 Bismarck Sea and moving the Manus arc relatively northward over the 

 Caroline Basin. 



This tectonic synthesis of the Caroline Basin and its margins has 

 incorporated relevant elements of all earlier interpretations. It 

 suffers from the chronic scientific ailment - lack of data, and will 

 certainly not be the definitive study of the area, which awaits that 

 additional data. 



Regional Evolution 



The following section attempts a simplified graphical reconstruc- 

 tion (Figs. 16 - 19) of the evolution of the Caroline Basin and it's 

 margins from 52 m.y. B.P. to the present. Only those crustal plates 

 directly involved in that evolution are considered, and no attempt is 

 made to integrate this evolution with the complex tectonic history of 

 the surrounding areas, 



65 



