Andrew Goodliffe, B. Taylor, F. Martinez and R. N. Hey (SOEST, University of Hawaii, 2525 Correa Road, Honolulu, HI, 96822; andrew@mano.soest.hawaii.edu)
Digital seismic data collected in conjunction with an HMR1-magnetics-gravity survey of the western Woodlark Basin reveal contrasting structural styles along and across the basin margins. The rifting region at the apex of the V-shaped basin shows structural asymmetry. Between 151o-152.5šE, a seismically-active fault appears to dip north beneath a down flexed pre-rift sedimentary basin and basement sequence, unconformably onlapped by near horizontal syn-rift sediments, and cut by high-angle normal faults, clearly visble in the HMR1 bathymetry. The footwall comprises high-relief rotated fault blocks of metamorphic basement (including core complexes?) overlain by only minor ponded sediments. The surficial rifted crust along the edges of the conjugate margins further east is cut by curvilinear, high angle normal faults that dip basinward. Gravity anomalies reveal a smooth transition in crustal thickness from rifted to oceanic crust, with slightly steeper gradients on the southern margin, consistent with asymmetric rifting. The northern margin comprises south-tilted fault blocks, with an active right-lateral, northeast trending, transform fault along its northern border with the Solomon Sea Basin. The 50 km-offset Moresby Transform Fault formed by cutting through rifted crust to join overlapping spreading segments of initial oceanic crust. It is not contiguous with transfer faults in the rifted margins.