Collision propagation in Papua New Guinea and the Solomon Sea

Abstract

The mountain system in Papua New Guinea (PNG) is growing by accretion of Australian margin strata to the front of the Papuan fold‐and‐thrust belt in the south and by accretion of exotic terranes along its NE margin. Presently, the Finisterre Terrane is being accreted along the NE margin of PNG, and the collision point is migrating eastward within the Solomon Sea. East of the collision point the New Britain Trench marks the tectonic front between the Solomon Sea and South Bismarck Sea plates, whereas to the west the tectonic front lies in the southern part of the Papuan fold‐and‐thrust belt. Present‐day sedimentary environments within the western Solomon Sea are inferred from interpretation of seismic reflection data. Similar facies are observed accreted to the front of the Finisterre Terrane in the Markham valley. The frontal Leron Formation is largely fluvial and shallow marine, and the Erap Complex contains elements of turbidites and pelagic deposits. There appears to be a smaller volume of coarse, proximal marine strata accreted to the front of the Finisterre Terrane than is expected from interpretation of reflection profiles in the western Solomon Sea. This difference may be attributed to a combination of submarine erosion in the Markham canyon, partial incorporation of these deposits into the Erap Complex, and a difference in depositional rates and products carried to the Solomon Sea in the past relative to what is observed today. Based on plate motions, alternative collision geometries, and the youngest dates available for the Erap Complex, we determine a rate of progression of the collision point of about 212 km/m.y. during the past 1 m.y.