HR: 0800h
AN: V51B-0575    [Abstracts]
TI: A South West Pacific Example of Volcanic Rift Margin Facies in a Backarc Basin Setting From Norfolk Basin Seismic Reflection Profiles.
AU: Taylor, L
EM: lydia@geosci.usyd.edu.au
AF: Sydney University, David Edgeworth Building F05, Eastern Avenue, University of Sydney, Sydney, NSW 2006 Austria
AU: * Muller, D
EM: dietmarmuller@mac.com
AF: Sydney University, David Edgeworth Building F05, Eastern Avenue, University of Sydney, Sydney, NSW 2006 Austria
AB: Large-volume extrusive basaltic constructions are ubiquitous along nearly all passive continental margins formed during the breakup of Pangea, reflecting rifting above anomalously hot mantle. Here we describe for the first time a complete passive volcanic conjugate margin sequence in a back-arc basin, the Norfolk Basin in the Southwest Pacific, based on high resolution and deep multichannel seismic reflection profiles from the northern Norfolk Basin FAUST-2 survey and the AGSO law of the sea survey 177. Multichannel seismic reflection data reveal lava deltas, landward flows, seaward-dipping reflectors and feeder dikes along the rift margins and volcanic plateaus within the basin. The timing of the construction of this volcanic margin is inferred to be syn-rift due to the the masking of major extensional faults by volcanic flows. In addition to suggesting high mantle temperatures beneath the Norfolk Basin, which have been imaged by seismic tomography (Ritsema et al., 1999), the data provide further evidence that the Norfolk Basin formed as a backarc basin in a plume-influenced subduction setting rather than by subduction driven mantle flow which may explain the apparent landward jump in back arc spreading. The identification of these volcanic facies in a backarc setting suggests that volcanic margin features may be useful indicators to identify plume-arc interactions in the geological record.
DE: 5480 Volcanism (8450)
DE: 3025 Marine seismics (0935)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting