Propagating rifts in the North Fiji Basin (southwest Pacific)

The accretion system in the North Fiji marginal basin currently consists of four major, differently oriented axes. Multibeam bathymetry, recently acquired over the central north-south axis between 18[degrees] and 21[degrees]S, reveals a peculiar tectonic framework. Fanned patterns of the sea-floor topography at the northern and southern tips of this segment are the general shape of a rugby ball. These data, and the interpretation of magnetic anomalies, indicate that this central sector of the ridge has lengthened northward at the expense of the axis aligned N15[degrees]E. Both spreading and propagation rates are about 70--80 mm/yr. A southward propagation is also envisaged on the basis of the similar morphotectonic framework observed at the southern tip of the north-south ridge.