TECTONIC COMPLEXITIES IN SOUTH FIJI MARGINAL BASIN

Two magnetic lineation patterns occur in the South Fiji marginal basin. North-south lineation, which are parallel to the Lau-Colville ridge, are identified as anomalies 8 through 12 (29-35 m.y. B.P.). The inferred age of the basin increases eastward to the ridge. These identifications are consistent with DSDP drilling results and suggest that at least part of the basin formed in the Oligocene. These results, together with our previous study of magnetic lineations in the Shikoku basin south of Japan, also imply that the mechanism of crustal accretion in marginal basins is similar to that at mid-ocean ridges. Unidentified east-west-trending lineations west of the northsouth pattern suggest a complicated tectonic history for the South Fiji basin. It seems that the evolution of the basin involved more than just one simple two-limb spreading system. © 1975