CONVERGENT MARGIN EXTENSION ASSOCIATED WITH ARC-CONTINENT COLLISION -THE FINSCH DEEP, PAPUA-NEW-GUINEA

The Finsch Deep is an asymmetric rhomboidal basin, with a maximum dept h of 5400 m, situated to the north of the Solomon Sea Triple Junction, Papua New Guinea. Anomalous slip vector azimuths, regional plate velo cities, earthquake hypocenters, End bathymetric depth relative to surr ounding terranes all indicate that the Finsch Deep is not a passive fe ature developed behind the subduction front. Our interpretation of all available data, including seismological studies, detailed bathymetry, side-scan character, and seismic sections, suggests that the Finsch D eep has developed due to N-S extension in the transition zone from con tinental collision west of the Solomon Sea Triple Junction to oceanic subduction to the east. The key mechanisms thought to drive ''converge nt margin extension'' within the New Guinea Collision are slab purl an d oblique subduction. Researchers studying other convergent margins ha ve recognized underplating and tectonic erosion as driving mechanisms for extension; though we have no evidence to either support or discoun t their presence within the New Guinea Collision.