Abstract

GLORIA sidescan imagery of the central Lau Basin reveals a complex neotectonic framework in which the central Lau spreading center is actively propagating southward at the expense of the eastern Lau spreading center. The latter is located about 75 km closer to the active Tofua arc, and the transfer of spreading motion across this distance is achieved via a "relay" spreading-ridge segment. New magnetic and bathymetric interpretations suggest that the majority of the central and southern basin was formed by the eastern Lau spreading center between 5 Ma and the present day. The processes of arcward ridge migration, ridge propagation, and basinward arc migration may reflect the complex interplay of the subduction zone and regional tectonics in driving back-arc spreading, and may be a common feature of this tectonic environment.

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