HR: 09:00h
AN: T51A-02    [Abstracts]
TI: Application of a New Model of Continental Lithosphere Breakup and Sea-floor Spreading Initiation to the Woodlark Basin Western Pacific
AU: * Karner, G D
EM: garry@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Kusznir, N J
EM: n.kusznir@liverpool.ac.uk
AF: Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, L69 3BX United Kingdom
AB: A new model of continental lithosphere thinning leading to continental breakup has been applied to the most recent segment of sea-floor spreading initiation in the Woodlark ocean basin in the western Pacific. Sea-floor spreading in the Woodlark ocean basin commenced approximately 8 Ma ago in the east and has propagated westwards with time reaching the Moresby sea-mount region at the present day. The most recent segment of westward sea-floor spreading propagation initiated at the beginning of the Brunhes epoch. To the west of the Moresby sea-mount, ahead of the propagating spreading tip, the extending continental crust is characterised by up to 3 km of sag-basin subsidence over a width of 150-200 km, but with little upper crustal faulting implying depth-dependent lithosphere stretching. Significant but local brittle deformation is associated with the late-stage (<0.5 Ma) Moresby fault system. Depth-dependent lithosphere thinning, in which stretching of the lower crust and lithosphere mantle greatly exceeds that of the upper crust, has been observed at many non-volcanic and volcanic rifted continental margins including conjugate margin pairs. Our new model of continental lithosphere thinning leading to continental breakup and sea-floor spreading initiation assumes that lithosphere thinning occurs in response to an upwelling divergent flow field within continental lithosphere and asthenosphere. Depth-uniform stretching of continental lithosphere cannot explain observed depth-dependent lithosphere stretching. Model formulation uses corner-flow predicted by kinematic iso-viscous stream-function or finite element solutions to advect continental lithosphere and asthenosphere material and their temperature fields. Corner-flow is defined by Vx, the divergence half-velocity, and Vz, the vertical upwelling velocity. Thinning of continental margin crust and lithosphere temperature field evolution is sensitive to the velocity ratio Vz/Vx. The new model of continental breakup and sea-floor spreading initiation successfully predicts the observed bathymetric profile of young ocean floor and rifted continental margin for the most recently initiated segment of Woodlark Basin sea-floor spreading to the east of Moresby sea-mount. The preferred model of Woodlark sea-floor spreading initiation and rifted margin formation requires that the upwelling divergent flow field propagated upwards from the base of the lithosphere from 8 Ma to 2 Ma leading to continental breakup and sea-floor spreading initiation at approximately 1 Ma.
DE: 8105 Continental margins and sedimentary basins
DE: 8109 Continental tectonics--extensional (0905)
DE: 8110 Continental tectonics--general (0905)
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8122 Dynamics, gravity and tectonics
SC: Tectonophysics [T]
MN: 2005 Joint Assembly