HR: 0800h
AN: T41C-1217    [Abstracts]
TI: Influence of Cumulative Boundary-Normal Convergence on Topography and Thrust Fault Development in Oceanic Lithosphere: The Australian-Pacific Plate Boundary South of New Zealand Since 10.9 Ma
AU: * Meckel, T A
EM: tmeckel@usgs.gov
AF: Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, 4412 Spicewood Springs Rd. #600, Austin, TX 78759-8500 United States
AU: * Meckel, T A
EM: tmeckel@usgs.gov
AF: Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 1 University Station C1100, Austin, TX 78712-0254 United States
AU: Mann, P
EM: paulm@ig.utexas.edu
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AU: Mosher, S
EM: mosher@mail.utexas.edu
AF: Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 1 University Station C1100, Austin, TX 78712-0254 United States
AU: Coffin, M F
EM: mcoffin@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AB: Individual segments of the submarine Australian-Pacific plate boundary south of New Zealand have evolved with unique tectonic histories since ~10.9 Ma (anomaly 5o). This is the direct result of the variable orientation of the boundary and relatively close proximity of the Australian-Pacific poles of rotation. Interaction along the oceanic extent of the plate boundary involves oceanic lithosphere of broadly similar age (i.e. thermal structure), resulting in morphologic and structural differences that can be attributed primarily to the variability in the angle and rate of convergence with respect to the plate boundary orientation over the last 10.9 Ma. We use swath bathymetry data from three cruises to quantify the amount of deformation that has occurred along ~1500 km of the plate boundary south of New Zealand. We calculate volumes of crust within 75 km of the plate boundary to the east and west that are displaced from the average local seafloor depth, and compare those results to plate boundary-normal convergence along the boundary predicted by stage rotations since 5.9 Ma. Plate boundary-normal convergence and topography are compared considering active faulting observed at the seafloor to characterize the geodynamic evolution of the different regions. Analysis reveals that a boundary-normal convergence of ~100 km marks the transition from strike-slip dominated faulting to partitioned underthrusting and strike-slip faulting. We consider the topography and structural development at the Macquarie and McDougall segments of the MRC to reflect failure to initiate subduction, suggesting that topographic relief (deepest trench to ridge crest) at a convergent oceanic boundary can reach ~5 km before initiation, which could take 5.9 m.y. These estimates provide observational constraints for the deformation processes involved in the poorly understood topic of subduction initiation, and should be incorporated in numerical modeling of such processes in similar settings.
DE: 8150 Plate boundary--general (3040)
DE: 8155 Plate motions--general
DE: 8157 Plate motions--past (3040)
DE: 8158 Plate motions--present and recent (3040)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting