INTRODUCTION 



The age and gross tectonic relationships of the southwest Pacific 

 area are shown in Figure 1. As can be seen, this area encompasses one 

 of the world's most complex tectonic regimes. 



The Caroline Basin is a 1.3 x 10° km^ oceanic basin lying north of 

 New Guinea and south of the West Caroline Ridge. It is bounded on the 

 east and west by the Mussau Trough and the Palau Trench, respectively. 

 The basin is divided into roughly equidimensional sub-basins, the East 

 and West Caroline Basins (Fig. 2), by the arcuate, northward-trending, 

 Eauripik Rise. These basins have typically oceanic crust as determined 

 by the seismic refraction work of Den and others (1971) . 



The age of the Caroline Basin crust was determined to be Tertiary 

 by Deep Sea Drilling Project (DSDP) core recoveries at sites 62 and 63 

 (Winterer and others, 1971), shown in Figure 2. 



Many hypotheses on formation and history of the basin have been 

 advanced. Winterer and others (1971) offered the possibility that the 

 basin was formed by sea-floor spreading from the Eauripik Rise. Moberly 

 (1972) proposed that the basin crust was formed during the Middle to 

 Late Oligocene time behind a southward advancing island arc, now welded 

 against northern New Guinea. Presumably, the present-day Caroline Ridge 

 would then represent the remnant or third arc described by Karig (1971) 

 at similar island arc systems. 



In a discussion of the results of leg 30 of the DSDP, the Scientif- 

 ic Staff (1973) proposed that the Caroline Basin was formed not by arc 



