Tectonics of the Papua‐Woodlark Region

Abstract

AbstractThe Papua‐Woodlark region exemplifies many plate tectonic processes, from active continental breakup to double plunging subduction zones. We present a synthesis of geological and geophysical data from the region and interpret these data to characterize the present plate boundaries. A subducted slab shown to underlie the Trobriand forearc is associated with the Papuan volcanic arc and the diapiric emplacement of felsic gneissic domes in the Woodlark rift from previously subducted continental materials in the mantle wedge. In contrast, the Suckling‐Dayman metamorphic core complex formed in the footwall of the Mai'iu extensional detachment, augmented by calc‐alkaline and high‐K magmatic intrusion and uplift. Utilizing Global Positioning System relative velocities, transform fault azimuths, ridge axis azimuths, and two fault slip directions, we derive a plate kinematic model for the Australia, Woodlark, Trobriand, and Solomon Sea plates to describe the neotectonics and provide insight to the past tectonics. We present two cases—with and without subduction at the Trobriand Trough—and favor the former based on our characterization of the plate boundaries. Our model estimates current Trobriand subduction rates of 4.5–4.7 mm/yr with obliquity increasing westwards, and full spreading rates, increasing eastwards along the Woodlark Basin spreading center, of 20–40 mm/yr. Based on seafloor morphology, we further estimate the time of the change in the pole of the Woodlark Basin opening at 450 Ka followed by a decrease in spreading rate and complete reorientation of the spreading axis fabric at 200 Ka.