NORTHERN LAU BASIN - BACKARC EXTENSION AT THE LEADING-EDGE OF THE INDO-AUSTRALIAN PLATE

GLORIA imagery of the Lau Basin north of 17-degrees-S shows several mo rphotectonic terrains: a basement ridge and sedimented inter-ridge are a in the SE; a nascent triple junction in the NE; a deeply sedimented basinal terrain in the central area; a linear neovolcanic zone strikin g NNE-SSW in the NW; and the northern flank of a leaky transform, the Peggy Ridge. Extension is now being accommodated at two main areas of spreading, but as no site of persistent long-term backarc crustal accr etion is evident in this 250-km-wide portion of the basin, we conclude that past extension was largely by formation of pull-apart basins and local magmatism.