A. M. Goodliffe; B Taylor; F. Martinez (SOEST, University of Hawai'i, 2525 Correa Rd., Honolulu, HI 96822; ph. 808-956-5238; e-mail: andrew@soest.hawaii.edu)
We carried out an analysis of seafloor age and a reconstruction of the spreading history of the Woodlark Basin from a compilation of geophysical data. Overall, the basin evolution comprises westward propagation into the Papuan Peninsula with spreading rates increasing eastwards from 36 to 67 mm/yr.In the early stages of seafloor spreading, contemporaneous extension of the continental margins requires a locally non-rigid plate reconstruction. Commonly, overlapping spreading segments nucleate within stretched continental lithosphere. Sometimes the OSCs evolve by dueling propagation, isolating continental slivers. In other cases, failure of a spreading segment leaves isolated basins floored by oceanic lithosphere. Alternatively, both segments may continue to spread until a transform fault cuts through the intervening continental lithosphere and oceanic lithosphere is eventually juxtaposed.The mature spreading centers included west and east directed propagators until an 80 ka synchronous reorientation of the entire spreading system. The outer-pseudofault of an eastward directed propagator, active since anomaly 2 time, records continuous propagation, whereas the inner pseudofault shows episodic failure of the opposing spreading center, producing a series of rotated microplates. The 80 ka synchronous reorientation resulted in rifting of pre-existing formerly off-axis oceanic lithosphere, again calling for locally non-rigid plate reconstruction.