Tectonic controls on facies transitions in an oblique collision: The western Solomon Sea, Papua New Guinea

Abstract

The western Solomon Sea is the site of a closing ocean basin and an incipient arc-continent collision between the Bismarck arc and the Australian continental margin in Papua New Guinea. Migrated seismic reflection profiles and HAWAII MR1 sidescan sonar data indicate that sedimentation within the Solomon Sea basin is controlled by topographic gradients generated by flexure of the Solomon Sea plate. Turbidites delivered to the basin by the submarine Markham Canyon extend farther eastward down the axis of the deeper New Britain Trench (north side of the Solomon Sea) than they do in the shallower Trobriand Trough (south side of the Solomon Sea). The stratigraphic record of the foredeep, in the zone of arc continent collision, is controlled by the steep topography of the Australian continental margin. A long (1.5–3 m.y.) period of deep marine turbidite deposition is followed by a short (50–100 k.y.) period of shallow-marine deposition and a long (0.5–1 m.y.) period of fluvial deposition. Comparisons between the foredeep record of Taiwan and the Papua New Guinea collision indicate that the steep topography of the Australian continental margin exerts significant control over the evolution of the foredeep, and the Taiwan foredeep is more controlled by the dynamic link between the flexural properties of the lithosphere and the orogenic load.