Seismic Investigation of the Papuan Ultramafic Belt

Abstract

Seismic survey data from a profile along the north-east Papuan peninsula coast indicate velocities which can be correlated with those of oceanic layers 1, 2 and 3, but with a crustal thickness of between 20 and 25 km. Distinct differences in the crustal layering are determined between the region where the Papuan Ultramafic Belt crops out along the coast and the region of the Trobriand Platform. The crustal thickness is more than twice the total thickness of gabbro and basalt components of the ophiolite suite exposed inland. Later seismic arrivals suggest the presence of a low-velocity zone below the Moho and a return to upper mantle velocities at depths of about 50 km.