TECTONIC CONTROLS ON FACIES TRANSITIONS IN AN OBLIQUE COLLISION - THEWESTERN SOLOMON SEA, PAPUA-NEW-GUINEA

The western Solomon Sea is the site of a closing ocean basin and an in cipient arc-continent collision between the Bismarck arc and the Austr alian continental margin in Papua New Guinea. Migrated seismic reflect ion profiles and HAWAII MR1 sidescan sonar data indicate that sediment ation within the Solomon Sea basin is controlled by topographic gradie nts generated by flexure of the Solomon Sea plate. Turbidites delivere d to the basin by the submarine Markham Canyon extend farther eastward down the axis of the deeper New Britain Trench (north side of the Sol omon Sea) than they do in the shallower Trobriand Trough (south side o f the Solomon Sea). The stratigraphic record of the foredeep, in the z one of arc continent collision, is controlled by the steep topography of the Australian continental margin. A long (1.5-3 m.y.) period of de ep marine turbidite deposition is followed by a short (50-100 k.y.) pe riod of shallow-marine deposition and a long (0.5-1 m.y.) period of fl uvial deposition. Comparisons between the foredeep record of Taiwan an d 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 lithospher e and the orogenic load.