A new scenario of the Parece Vela Basin genesis

A new high density geophysical data set in the Parece Vela Basin north of 1 5 degrees N has been obtained through surveys conducted by the Hydrographic Department of Japan. The combined analyses of the swath bathymetry, magnet ic and gravity anomalies from these surveys reveal a new scenario for the g enesis of this basin. The evolutionary process is as follows: rifting and c rust thinning (29-26 Ma), northward propagation of east-west opening (26-23 Ma), east-west opening together with the Shikoku Basin (23-21 Ma), and the northeast-southwest opening (20/19-15 Ma). The western part of the basin i s complicated, displaying some traces of northward propagation of the sprea ding center. The change between early east-west opening and the final stage of northeast-southwest spreading is marked by a distinct north-south bound ary in both structural and magnetic patterns. Deep and rough topography of the extinct Parece Vela Rift is due to magma starvation in the terminal pha se of the spreading.