Brian Taylor, F. Martinez, R. N. Hey and Andrew Goodliffe (SOEST, University of Hawaii, 2525 Correa Road, Honolulu, HI, 96822; andrew@mano.soest.hawaii.edu)
A marine geophysical and HAWAII MR1 survey of the west Woodlark Basin gives new insights into active processes of rift and spreading center propagation into a continent. Spreading is <3 Ma. Rifting is active between the current spreading center tip at 151.6šE and the pole of opening ~4š west. The rifting to spreading transition involves both nucleation of discrete spreading cells and organized ridge propagation. Two ridge propagation events into the margin at 153šE formed continental slivers surrounded by oceanic crust. Spreading is about to propagate into this margin again. Rifting of the conjugate margins continues for ~1 m.y. after spreading has initiated between them. Extension does not immediately localize to the ridge axis, as shown by present overlap between spreading and seismogenic margin faulting, and by inwardly curved seafloor fabric and magnetic anomalies that require non-rigid reconstructions. The initial spreading system lacks transform faults and has both overlapping and orthagonally offset segments. It evolves by ridge propagation, transform development, ridge jumping and reorientation (the latter only 0.1 Ma, after conjugate steps in the margins slid past one another along the Moresby transform).