TECTONIC EVOLUTION OF THE CORAL SEA BASIN

Studies of marine magnetic anomaly data from the Coral Sea basin reveal magnetic lineations which strike N70oW almost parallel to the N margin of the Queensland Plateau. The lineation pattern is best developed in the E part of the basin, and we can confidently identify a sequence of anomalies 26 (and perhaps 27) through 24 repeated about an extinct spreading center along the long axis of the basin. The extinct spreading center is associated with a short wavelength (lambda approx/less than 40km) free air gravity anomaly low of 10-20mGal and a region of rough acoustic basement. We infer that the Coral Sea basin began opening at about 62Ma BP at a half-spreading rate of 2.4cm/yr and that spreading ceased at about 56Ma BP. Although the Coral Sea ceased opening at the same time as the Tasman Sea, finite rotations determined for anomaly 26 lineations from these two basins are distinctly different. We thus infer that at least one additional plate boundary was active in the Paleocene and that it met the Coral Sea and Tasman Sea plate boundaries at a triple junction near the E end of the Coral Sea basin.-Authors